Chapter I Introduction

Chapter I INTRODUCTION AND OBJECT OF INVESTIGATION

IA. INTRODUCTION

nvironmental pollution, as a consequence of the Eindustrialization process, is one of the major problems that has to be solved and controlled.

Wastewaters can contain compounds that are non- biodegradable or toxic to biological organisms. This may include heavy metals such as (cadmium, cobalt, mercury, lead, zinc, copper, arsenic, strontium, chromium,……. etc ) and organic compounds as dyes, chlorinated aromatic compounds; poly- chlorinated bi-phenols (PCBs) and poly aromatic hydrocarbons (PAHs ).

Heavy metals are not biodegradable and have become an ecotoxicological hazard of prime interest and increasing significance owing to their harmful effect on human physiology and other biological systems when they exceed the tolerance levels. In addition mining, mineral processing, electric and electronic industries, dye and paint manufacture, textile production, plating works, photography, battery manufacturing, and extractive metallurgical operations also generate toxic liquid wastes [Goyal and Ahluwalia, (2007) & Olayinka et al., (2007) & Olayinka et al., (2009)]. 1 Chapter I Introduction

A number of technologies for the removal of heavy metal ions and dyes from aqueous solutions have been developed over the years [Romero-Gonzales et al., (2001)]. The most important treatment processes for metals and dyes contaminated waste streams include chemical precipitation, membrane, filtration, ion exchange, carbon adsorption, and coprecipitation/adsorption [Bailey et al., (1999)]. However, all these techniques have their inherent advantages and limitations in application. Some examples are summarised in Table (I.1) [Luqman Chuah Abdullah et al., (2010 )].

2 Chapter I Introduction

Table (I.1): Current treatment technologies for heavy metals and dyes removal involving physical and/or chemical process

Physical and/or chemical Advantages Disadvantages process High energy costs Oxidation Rapid process for and formation by- dye removal products Good removal of a Absorbent requires Ion-exchange wide range of regeneration or metals and dyes disposal Good removes of Concentrated Membrane filtration heavy metals and sludge production, technologies dyes expensive High sludge Economically production and Coagulation/flocculation feasible formation of large particles Rapid process and High energy costs Electrochemical treatment effective for certain and formation of metal ions by-products Applied in gaseous Ozonation state: alteration of Short half life volume No sludge Formation of by- Photochemica production products Irradiation Effective at lab Required a lot of scale dissolved O2 Economically High sludge Electrokinetic coagulation feasible production Effective decolourisation of Sludge generation Fentons reagents both soluble and insoluble dyes Feasible in Technology yet to Biological treatment removing some be established and metals and dyes commercialized

3 Chapter I Introduction

The previous processes usually need expensive facility and high maintenance cost. Therefore, there is a need for more economical alternative technologies or sorbents for the treatment of metals and dyes contaminated waste streams.

This work is focused on the removal of certain metal ions and some organic materials from waste streams using two techniques: adsorption by bone char and liquid emulsion membrane (LEM). IA.1 ADSORPTION TECHNIQUE:

Adsorption is an effective purification and separation technique used in industry especially in water and wastewater treatments. Sorption treatment can be used independently and in combination with biological treatment as a method of preliminary purification or primarily polishing. In this context, it is desirable to distinguish between three principal types of adsorption:

IA.1.1. Exchange Adsorption:

Adsorption of the first type falls within the of ion– exchange and is often referred to as “exchange adsorption´. Exchange adsorption is, as the term implies, a process in which ions of one substance concentrate at a surface as a result of electrostatic attraction to charged sites at the surface. For two potential ionic adsorbates in like concentration and in the absence of other specific sorption effects, the charge on the ion

4 Chapter I Introduction is the determining factor for exchange adsorption. In a system containing a monovalent ion under the stated conditions, the influence of kinetic energy to remain in solution phase is the same for each, but the trivalent is attracted much more strongly toward a site of opposite charge on the surface of the adsorbent. For ions of equal charge, molecular size (hydrated radius) determines order of preference for adsorption, the smaller ion being favored.

IA.1.2. Physical Adsorption (Ideal Adsorption):

Adsorption occurring as a result of van der Waal,s forces is generally termed ³ physical adsorption ” a term which has come to represent cases in which the adsorbed molecule is not affixed to a specific site at the surface but is rather, free to undergo translational movement within the interface. Physical adsorption is usually predominant at low temperature, and is characterized by a relatively low energy of adsorption, that is the adsorbate is not held as strongly to the adsorbent as for chemical adsorption. Adsorption of this type is sometimes referred to also as ³ideal adsorption´

IA.1.3. Chemical Adsorption:

If the adsorbate undergoes chemical interaction with the adsorbent, the phenomenon is referred to as ³chemical adsorption´, ³activated adsorption ´ or ³ chemisorption´. Chemically adsorbed molecules are considered not to be free to move on the surface, or within the interface.

5 Chapter I Introduction

Chemical adsorption processes exhibit high energies of adsorption because the adsorbate forms strong localized bonds at active centers on the adsorbent. Chemical interaction between the adsorbent and the adsorbate is favored at higher temperature because chemical reactions proceed more rapidly at elevated temperatures than at lower temperatures.

Most adsorption phenomena are combinations of the two forms (physical and chemical adsorption) that is, the several forces which influence the different types of adsorption often interact to cause concentration of a particular solute at interface. Thus, it is generally not easy to distinguish between physical and chemical adsorption.

IA.1.4. Main Factors Influence The Adsorption Process:

Many factors influence the rate at which adsorption reactions occur and the extent to which a particular material can be adsorbed. Some of the more important factors will be discussed.

IA.1.4.1. Characteristics of the adsorbent.

Particle size and surface area are important proprieties of an adsorbent with respect to its use as an adsorbent. The size of carbon particle influences the rate at which adsorption occurs: adsorption rates increase as particle size decrease [Najm et al., (1990)].

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IA.1.4.2. Solubility of adsorbate.

For adsorption to occur, a molecule must be separated from the solvent and become attached to the adsorbent surface. Soluble compounds have strong affinity for their solvent and thus are more difficult to adsorb than insoluble compounds. However, there are exceptions, since many compounds that are slightly soluble are difficult to adsorb, whereas some very soluble compounds may be absorbed readily [Benefield et al., (1982)].

IA.1.4.3. Size of adsorbate molecules.

Molecular size would logically be important in adsorption, since the molecules of adsorbate must enter the micropores of a adsorbent particle so as to be adsorbed. Research studies have shown that within a homologous series of aliphatic acids, aldehydes or alcohols, adsorption usually increases as the size of molecule becomes greater [Benefield et al., (1982)]. This can partly be explained by the fact that forces of attraction between adsorbent particle and adsorbate molecules are greater the closer the size of the molecule is to the size of the pores in the adsorbent. Adsorption is strongest when the pores are just large enough to permit the molecules to enter. Most wastewaters contain a mixture of compounds representing many different sizes of molecules. In this situation there would appear to be a danger of molecular screening, i.e. large molecules blocking the pores to prevent the entrance of small molecules. However, irregular shape of both the molecules and the pores as well as the constant motion of the 7 Chapter I Introduction molecules, prevents such blockage from occurring. Further more, the greater mobility of the small molecules allows them to diffuse faster and to enter the pores ahead of the large molecules[Benefield et al., (1982)].

IA.1.4.4. Temperature.

The temperature at which an adsorption process is conducted will affect both the rate of adsorption and the extent to which adsorption occurs. Adsorption rates increase with the increased temperature and decrease with decreased temperature. However, since adsorption is an exothermic process, the extent of adsorption will increase at lower temperatures and decrease at higher temperatures [Benefield et al., (1982) & Weber et al., (1972)].

IA.1.4.5. Initial concentration.

In a multisolute system, the adsorptive capacity is the function of the initial concentration of the adsorbate, which doesn’t occur in the single-solute system[Najm et al., (1991) & Huang et al., (1996)].

IA.1.4.6. Contact time“Equilibrium time”.

Perhaps the most important consideration in determining an equilibrium isotherm is selection of an equilibration (contact) time long enough to ensure that equilibrium is actually reached or closely approached. Failure to do so can result in data of questionable value, and use of such data can lead to

8 Chapter I Introduction gross underestimation of adsorptive capacity [Randtke and Snoeyink, (1983)].

Generally equilibrium time is defined as the time through which equilibrium occur between adsorbate and adsorbent or in other words is the period of time after which there is no further decrease in the solution concentration. This time may be hours, days or even weeks [Randtke and Snoeyink, (1983)].

IA.1.4.7. Adsorption of mixed solutes.

In the application of adsorption for purification of waters and wastewaters the material to be adsorbed commonly will be a mixture of many compounds rather than a single one. In systems with more than one adsorbate, competition between the adsorbates for surface sites may occur. The degree of competition is dependent on the type and concentration of the competing ions, number of surface sites and the affinity of the surface for adsorbate. The presence of second adsorbate does not always decrease metal removal. Huang, (1984) reported that the presence of organic adsorbates did not adversely affect the removal of several heavy metal .

IA.1.4.8. Effect of pH.

pH is the primary variable governing metal adsorption onto hydrous solids (activated carbon, metal oxides, clays, etc.) [Stumm and Morgan, (1981)].

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For cationic heavy metals, adsorption increases with increasing pH (the fraction of metal removed increases from zero to one over a relatively narrow pH rang ). The opposite is observed when the metal exists as an anion (removal generally increases with decreasing pH ). The pH affects the status of the outer hydration sheaths of the metal ion, metal solution speciation, complexation and solubility and the behavior of the carbon surface groups .

IA.1.4.9. Metal type and concentration.

In general, the lower the pH at which cationic metals x ( x-n ) form aqueous hydroxide complexes [ Me (OH)n ] and solids [ Me (OH) 2(s) ], the better the metal will be removed. The formation of the first metal hydroxide species can be represented by the following chemical reaction :

2+ + + Me + H2O ļMe (OH) + H ; K1

The concentration of the metal ion affects the removal mechanism as well as the surface loading. If the concentration of the cationic metal is large enough such that Me (OH)2(s) forms, then surface precipitation can occur. If the metal concentration is less than the metal`s solubility, then the primary removal mechanisms are sorptive in nature (physical / chemical adsorption, ion exchange).

Many investigators have studied the feasibility of using cheap, commercial available materials as potential adsorbents

10 Chapter I Introduction e.g. activated carbons, bone char, alumina, silica, bauxite, bentonite, fuller’s earth, molecular sieves, peat, lignite, chitin, chitosan, and ion exchange resins [Mckay, (1995) & Srivastava et al., (1997)].

IA.1.5. Activated Carbon:

The term active carbon (AC) actually implies a rather broad family of substances, with highly developed internal surface area, porosity and individual species being characterized by sorptive and catalytic properties rather than by definite structure or specific chemical composition [Timothy, (1999)]. Porous carbon materials or activated carbons have been used for thousands of years and have become extremely versatile adsorbents. Active carbon is a broad-spectrum agent that effectively removes toxic and bio-refractive substances such as insecticides, herbicides, chlorinated hydrocarbons, heavy metal ions, and phenols, typically present in many water supplies [Hassler, (1974) & Austin and Shreve, (1985) & Bandosz, et al., (2003) & Kadirvelu et al., (2001) Ansari and Masoudi, (2004) & Ansari, (2004) & Ansari and Omidvari, (2005) & Ansari and Nikravan Shalmani, (2005) & El-Shafey et al., (2002) & Mostafa, (1997 )].

The major applications of activated carbon are in solution purification and for the removal of taste, color, odors and other objectionable impurities from liquids, water supplies and vegetable and animal oils. In the recent years, it has been increasingly used for the preventation of environmental 11 Chapter I Introduction pollution and antipollution laws have increased the sales of active carbons for control of air and water pollution.

Activated carbon can be manufactured from any material that has reasonable elemental carbon content. Any lignocellulosic material can be converted to an activated carbon. The literature mentions many precursors for activated carbon such as bagasse [Ahmedna et al., (2000)] scrap tires and saw dust [Nadhem K. Hamadi et al., (2001)], almond, pecan, English walnut, black walnut and macadamia nut [Christopher A. Toles at al., (1998)] pistachio [ Wartelle and Marshall, (2001)] hazelnut shells [ Kobya, (2004 )] rice husk [Nevin Yalem and Vadettin Sevine, (2000)] rice bran [ Mubeena Akhtar, (2005)].

Particular properties may be imparted to an active carbon either by starting with different raw material or by utilizing different preparative procedures.

IA.1.5.1 Preparation of active carbon.

According to Bansal et al., (1988) & Satya et al., (1997), the preparation of activated carbons involve two main steps; carbonization of the carbonaceous raw material at temperature below 700 0C in the absence of oxygen, and activation of the carbonized product. During carbonization most of the non- carbon elements such as oxygen and hydrogen are first removed in gaseous form by the pyrolytic decomposition of the starting material. The free atoms of elementary carbon

12 Chapter I Introduction are grouped into sheets of condensed aromatic ring systems with a degree of planar structure. The arrangement of these aromatic sheets is irregular and leaves interstices between them, which may, filled with tarry matter or products of decomposition or at least blocked partially by disorganized carbon. The important parameters that determine the quality and the yield of the carbonized product are:(i) rate of heating, (ii)final temperature and (iii) soaking time [Manocha, (2003)].

Simple cooking or carbonization does not give rise to products that have adsorption capacity because of their less developed pore structure and low surface area. This pore structure is enhanced during the activation process, which convert the carbonized raw material into a form that contain the greatest possible number of randomly distributed pores of various shapes and size giving rise to an extended and extremely high surface area of the product [Bansal et al., (1988)].

The objective of the activation process is to enhance pore volume and to enlarge diameter of the pore, which were created during carbonization process, and to create new porosity. Activation process removes the disorganized carbon, exposing the aromatic sheets to the activation agent in the first phase and leads to the development of microporous structure. In the later phases of the reaction the significant effect is widening the existing pores or the formation of large-sized pores by complete burn- off of the walls between the adjacent pores

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I A.1.5.2 Methodes of activation.

Typically, the activation of carbon can be divided into two processes. First, the physical method consists of the pyrolysis of the precursor material and gasification of the resulting char in steam, nitrogen gas, air or carbon dioxide. The formation of the porous structure is achieved by elimination of a large amount of internal carbon mass. High porosity carbons can be obtained only at a high degree of char burn off. For the chemical method, pyrolysis char would be impregnated with some chemical reagents, such as ZnCl2, H3 PO4, NaOH and KOH. Because of the dehydrogenation process, the chemical reagents promote the formation of cross-links, leading to the development of a rigid matrix, less prone to volatile loss and volume contraction upon usage. According to Zhonghua and Vansant, (1995) & Ahmadpour and Do, (1996) & Lillo- Ródenas et al., (2003) & Lillo-Ródenas et al., (2004) major advantages of the chemical activation compared to the physical activation are lower treatment temperatures and shorter treatment times. In addition, activated carbon obtained by chemical activation exhibits a larger surface area and better developed mesoporosity than physical activation.

IA.1.5.3 Structure of activated carbon.

Activated carbons are highly porous materials with surface areas of up to 3000 m2.g-1. The surface area of a typical activated carbon is about 1000 m2.g-1. These high surface areas are the result of development of mainly micro- and mesopores while a little contribution is also come from macropores.

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According tothe IUPAC classification, pores having the radii less than 2 nm are called micropores whereas pores having the size of radii in between 2 to 50 nm are identified as mesopores. Macropores are defined as pores having the radii size above 50 nm. Cokes, chars and activated carbons are often termed as amorphous carbon. X-ray diffraction and electron microscopy have shown that these materials have crystalline characteristics, even though they may not show certain features, such as crystal angles and faces, usually associated with the crystalline state. The existence of submicroscopic dimensions in so called amorphous carbons makes the microcrystal structure known as crystallites. The basic structural character of amorphous carbons is closely approximated by the structure of pure graphite. The graphite crystal is composed of layers of fused hexagons held approximately 0.335 nm apart by van der Waals forces [Smisek and Cerny, (1970)].

Figure (IA.1): Carbon Atom Arrangements in Graphite Crystal

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However, the structure of activated carbon differs some what from that of graphite. During carbonization process, several aromatic nuclei, having a structure similar to that of graphite are formed. Planar separation distance in carbon is approximately 0.36 nm. From X-ray spectrograph, these structures have been interpreted as microcrystallite consisting of fused hexagonal rings of carbon atoms structurally, carbon can therefore be considered to consist of rigid interlinked cluster of microcrytallites. Each microcrystallite comprises a stack of graphite planes. Microcrystallites are interconnected by interaction of functional groups terminating the graphitic planes. The diameter of the planes forming the microcrystallites, as well as the stacking height, has been estimated at 2-5 nm indicating that each microcrystallite consists of about 5-15 layers of graphite planes [Wolff, (1959)].

It can be summarized that AC is black, amorphous solid containing major portion of fixed carbon content and other materials such as ash, water vapor and volatile matters in smaller percentage. Beside that, AC also contain physical characteristic such as internal surface area and pore volume. The large surface area results in a high capacity for absorbing chemicals from gases or liquids. The adsorptive property stems from the extensive internal pore structure that develops during the activation process.

IA.1.5.4 Surface functional groups on active carbon.

Faust and Aly, (1987) reported that when oxygen contacts carbon surfaces some sort of oxygen-carbon complex is formed. It is known that surface functional groups are 16 Chapter I Introduction formed during the carbon activation process. In general, acidic oxides are predominantly formed in carbon when it is prepared under moist air at 300 to 500°C, and basic oxides in those carbons prepared at 800 to 900°C in air, steam, or carbon dioxide. Amphoteric properties are found in carbons prepared between 500 to 800°C. The activated carbons prepared at low activation temperature, below 500-600°C, adsorb OH– ions primarily are called L-carbons. Those activated carbons are prepared at above 500-600°C and adsorb H+ ions are called H– carbons. Almost every type of functional group in organic chemistry has been suggested to be present on activated carbons surface. The ones suggested most often acidic functional groups are: carboxyl, phenolic-hydroxyl and quinone-type carbonyl groups Fig. (IA.2) while other suggested groups are ether, peroxide and ester groups in the forms of normal lactones and fluorescein-like lactones, carboxylic acid, anhydrides and the cyclic peroxide Fig. (IA.3). On the other hand, proposed basic surface groups include chromene and pyrone.

Carboxyl groups Phenolic hydroxyl groups Quinones

Fig.(IA.2): Structures of carboxyl, phenolic hydroxyl and quinines carbonyl groups

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Carboxylic acid anhydrides Cyclic peroxide

Fig. (IA.3): Structures of carboxylic acid anhydrides and cyclic peroxide

IA.1.5.5 Bone char as precursor for activated carbon.

Almost any carbonaceous material can be converted into activated carbon [Hsisheng and Sheng-Chi, (2000) & Girgis et al., (2002)], whether it is occurring naturally such as coal (e.g. peat, lignite and all forms of coal) and lignocellulosic materials (e.g. wood, coconut shell, fruit stones, nut kernels etc.) or prepared synthetically such as organic synthetic polymers (e.g. synthetic resins, rayon, polyacrylonitrile, polyvinylidene chloride, waste resins, textile wastes, rubber, dumped gangue etc).

Extensive research has been carried out during the last ten years to find low-cost, high capacity adsorbents for the removal of metal ions and organic compound such as dyes. A wide range of adsorbents have been developed and tested, including several activated carbons [Cheung and Venkitachalam, (2000) & Rao et al., (2002) & Yildiz, (2004) & Gray and Schwab, (1993)]. A number of low-cost agricultural [Netzer and Hughes, (1984) & Ngah et al., (2002) & Wang and Xing, (2002) & Keith and

18 Chapter I Introduction

Gordon, (2005)]. Other minerals and materials with potential for exchange sorption have been tested; among those are sodium calcium bentonite and bone char [Keith and McKay, (2008) & Purevsuren et al., (2004) & Wilson et al., (2003) & Jiang, (2001) & Wu et al., (2005) & Nasiruddin et al., (2007) & Liu et al., (2007) & Pattanayak et al., (2000)] to remove a wide range of pollutants, such as metal ions and organics, from wastewaters.

Bone char is derived from the carbonization of the crushed animal bones by heating them to 500–700 0C in an airtight iron retort for 4–6 h [Chen et al., (2008)]. The crushed bone, after the heating process, will form the bone charcoal, which is composed of calcium hydroxylapatite (CaHAP) (70–76 wt%), carbon content (9–11wt%), calcium carbonate (7–9 wt%) and traces of acid insoluble ash, Fe, Mg and SiO2 [Choy and Mckay, (2005) & Hassan et al., (2008)]. Actually, calcium phosphate acts as adsorption as well as ion exchange sites [Hassan et al., (2008)]. Bone char has been used extensively as an adsorbent for the decolorization of cane sugar, defluoridating agent [Chen et al., 2008)].

IA.1.6 Literature Survey on Adsorption Using Animal Bone Char:

Carbon is found in the free state crystalline as diamond and graphite and amorphous as coal or combined as CO2 in air, as hydride CH4 in petroleum districts, as carbonate CaCO3 in

19 Chapter I Introduction

marble, chalk and lime stone, MgCO3 in magnesite and

MgCO3. CaCO3 in dolomite.

It is better to give insight on the five types of amorphous forms of carbon a) Carbon black is a black powder made by ignition of high carbon substances such as turpentine in limited amount of air, and passing the smoke over large sheets of porous cloth, from which its powder is separated by shaking for use in making printing inks and paints and in rubber industry. b) Wood charcoal is obtained by destructive distillation of wood, i.e., by heating it in absence of air. Among the volatile products are methanol, acetic acid, acetone and wood tar. c) Animal charcoal (bone char) is obtained by treating bones with benzene to remove fats and with steam to remove gelly matter used in making glue, and then subjecting them to destructive distillation in closed retorts. The product known as animal charcoal (bone char) contains 10 percent calcium carbonate and 80 percent calcium phosphate. d) Coal is a natural product resulting from the decomposition of vegetable matter under high pressure in presence of water and absence of air inside the soil. The decomposition

results in losses hydrogen as CH4 and carbon as CO2 so that the residual becomes richer in carbon. During the progressive stages of carbonization the several varieties of coal, peat, lignite, and bituminous are formed. 20 Chapter I Introduction e) Coke is obtained by heating coal in absence of air. It contains 80 to 90 percent carbon and the rest are ammonia. Coke is used in the reduction of metallic ores and in the production of water gas.

In the following a literature survey on bone char as adsorbent in recent publication

Kawasaki et al., (2009) studied the removal of fluoride ion by bone char which produced from animal biomass and found that fluoride ion adsorption was increased in bone char produced at a low carbonization temperature, the adsorption mechanism of fluoride ion on bone chars might be monolayer. The authors stated that phosphate ions from bone char eluted due to adsorption of fluoride ions, and the adsorption mechanisms of fluoride ions onto bone char would be a physical adsorption and phosphate ion in bone char is exchange to fluoride ion.

Chen et al., (2010) investigated the isotherms and kinetics of adsorption of aqueous Pb(II) by bone char meal (BM) and phosphate rock (PR) using batch experiments. The removal of Pb(II) was characterized and effects of pH and reaction time on Pb removal efficiency by BM/PR were also investigated. They found that Pb sorption onto BM or PR was generally biphasic, with initially fast reactions followed by slow and continuous reactions and the removal efficiency by BM and PR increased with increasing pH except at a pH higher than 6.15. They also showed that BM has a much higher Pb (II) removal rate than PR in solution. 21 Chapter I Introduction

Razaee et al., (2009) studied the removal of endotoxin from aqueous solution using bone char (BC) which prepared from cattle animal bone by pyrolysis in a furnace at 850 0C as an adsorbent material. They investigate the morphology and physic- chemical characteristics of the adsorbent. Kinetic studied revealed that the adsorption of endotoxin is rapid and the mechanisms of adsorption of endotoxin onto BC had a significant contribution from film diffusion. The maximum adsorption efficiency they achieved is 98 % at an adsorbent dose of 40 g L-1 with initial endotoxin concentration 80 mg ml-1. They showed that the Langmuir isotherm adsorption equation model describe the experimental adsorption isotherm with good accuracy and the bone char could be used as effective adsorbent for endotoxin removal.

Sneddon et al., (2005) discussed the arsenic (V) removal from aqueous solution by addition of either a mixture of synthetic hydroxylapatite and baryte or bone char. They found that, although the mixture of hydroxylapatite and baryte had a small influence on arsenic concentrations, bone char was a very effective sorbing agent for arsenic (V). Packed-column studies to investigate the bone-char capacity, followed by leaching tests were carried out. They showed that the capacity of bone-char was found to be superior to that granular activated carbon.

Ko et al., (2004) studied the ability of bone char to adsorb copper (II), zinc (II) and cadmium (II) ions from wastewater. They have been measured experimentally three single-component

22 Chapter I Introduction systems and three binary systems. The three single-component equilibrium data were analyzed using the Langmuir equilibrium isotherm equation. The Cu-Zn, Cu-Cd, Cd-Zn binary equilibrium experimental data were examined by incorporating the Langmuir isotherm equation into the ideal adsorbed solution threory (IAST). The solution methods and the predicted results for the three binary systems at different metal ion compositions have been evaluated. In addition, the application of the IAST to the model prediction for the fixed bed system is presented.

Abe et al., (2004) derived the characteristics of fluoride ion adsorption onto carbonaceous materials as adsorption isotherms at different temperatures and in different pH solutions. The fluoride ion was adsorbed into pores in carbonaceous materials produced from wood; the large the specific surface area, the more fluoride ions adsorbed. The results showed that bone char was the most effective adsorbent. The adsorption of fluoride ion onto bone char is endothermic. Bone char can be utilized to remove fluoride ions from drinking water.

Abdel Raouf and Daifullah, (1997) have been studied the sorption capability of bone char (B.Ch.) towards the removal of 124SbIII, 124SbV and their mixture from aqueous and organic liquid radioactive wastes. For the sake of comparison, the sorption of 152EuIII from aqueous radioactive wastes has also been investigated.

Cheung et al., (2001) studied the sorption equilibrium and kinetics of cadmium ions from aqueous solution onto bone char. 23 Chapter I Introduction

Equilibrium isotherms for the sorption system were correlated by Langmuir equation. They also investigated the removal rates of cadmium ions based on the Langmuir equation.

Ko et al., (2000) have been studied the sorption of copper, cadmium ions on bone char due to their toxicity in nature and extensive use in industry. Fixed-bed column experiments with different feed concentrations, flow rates and adsorbent particle sizes have been carried out, evaluating sorption of these two metal ions on bone char. They also studied pilot plant experimental and used the BDST model to analyze the data.

Daifullah et al., (1998) studied the removal of some organic pollutants which are commonly found in wastewater streams using bone charcoal (BC). In this concern, they have been evaluated the adsorption isotherms of 2-chlorophenol, m-,p- cresols, 4- nitrophenol, 2,4 dichlorophenol and 2- nitrophenol from aqueous solutions by (BC). The data confirm both Langmuir and Freundlich adsorption isotherms. Also, they assessed treatment of industrial wastewater using (BC) coupled with uv- irradiation in the presence of H2O2.

Warwick et al., (2006) studied the reaction of uranyl ions with bone char under a variety of laboratory conditions and found that this reaction leads to products (e.g. uranium modified bone char) that are effective incorporating and retaining radionuclides and these products are highly insoluble and are compositionally analogous to natural uranium-bearing minerals found in the supergene environment. A calcium uranium oxyhydroxide, 24 Chapter I Introduction similar to becquerelite is produced when bone char reacts with uranyl ions at elevated temperatures and pressures under mildly acidic conditions (pH§ 4). Under more acidic conditions (pH§3), a compound similar to phosphuranylite forms whilst in the presence of excess phosphate, a compound similar to chernikovite is produced.

Lambert and Graham, (1995) investigated the amenability of non-specific natural organic compounds for removal by adsorption onto activated carbon, activated alumina, activated bauxite and bone char adsorbents.

Lambert and Graham, (1989) used alternative adsorbents of activated carbon e.g. bone char, activated alumina and activated bauxite for adsorption of polar organic compounds.

Cheung et al., (2000) have been studied the removal of copper and zinc from aqueous effluents by bone char in single component sorption systems. The results showed that the sorption capacity of bone char for copper and zinc is 0.75 and 0.53 mmol per g bone char, respectively. The values indicate that bone char is a suitable sorbent for the two metal ions. The equilibrium isotherms are best described by a Langmuir- Freundlich (L–F) type isotherm equation. The kinetics of sorption of the two metal ions have been analyzed by the kinetic models, namely, the Lagergren pseudo first order model. Kinetic analysis of the model has been carried out for system variables (initial metal ion concentration and mass of bone char). 25 Chapter I Introduction

Christoffersen et al., (1991) used a bone char column to defluoridate water. They could repeatedly, regenerated the bone char column without significant loss of capacity for fluoride or of efficiency. The regeneration solution contains calcium chloride and sodium dihydrogen phosphate at pH=3.

Choy et al., (2004) studied the sorption of copper, cadmium and zinc onto bone char in terms of equilibrium and rate studies. Equilibrium studies have been analyzed using the Langmuir isotherm equation and the maximum sorption capacities for the metals were 0.477, 0.709, 0.505 mmol g-1 bone char for cadmium, copper and zinc ions, respectively. The kinetic experimental data were used to analyze the effect of external film boundary layer and intraparticle mass transfer resistance on the sorption process and its significance.

Mjengera and Mkongo, (2003) have been tested the defluoridation methods on bone char. The bones are charred in special kilns fuelled by wood charcoal. The effectiveness of bone char particles sizes in fluoride removal has been studied and the results favoured small particle sizes. However, experimental conditions discouraged the use of very fine particles sizes of bone char due easy clogging. The bone char used has the capability of producing water with a residual fluoride concentration of less than 0.1 mg/l from initial fluoride 12 mg/l.

Walker and Weatherley, (2001) have been investigated the removal of acid dyes, Tectilon Blue 4R, Tectilon Red 2B and Tectilon Orange 3G, from single component solution adsorption 26 Chapter I Introduction on activated carbon and bone char in isotherm experiments. The results were successfully modelled using Langmuir and freundlich isotherm analyses. Nitrogen adsorption analysis was also undertaken and indicated that the activated carbon had a much higher specific surface than the bone char. Calculation involving the pore size distribution data indicate that only 14 % of the total specific surface of the activated carbon is available for adsorption due to the high molecular area and aggregation of the dye. The equilibrium data indicate that dye aggregation takes place in the solid phase of both adsorbents with higher solid phase aggregation numbers found using the bone char, which is indicative of multilayer adsorption.

Lambert and Graham, (1995) investigated the effect of preozonation on the organics adsorption efficiencies using activated carbon, activated alumina, activated bauxite and bone char adsorbents.

Larsen et al., (1994) examined the efficiency of defluoridation by char produced from various parts of bones and charred for various lengths of time at various temperatures, relating the preparation of the char to its X- ray diffraction pattern, its content of pyrophosphate and its capacity for defluoridation. Bone sample charred for shorter periods at lower temperatures were poorer apatites. Bennett and Abram, (1967) used bone char as an adsorbent for the decolorization of cane sugar.

Rim-Rukeh et al., (2007) investigated the adsorption of a fixed-bed filled with bone-chars in terms of removal 27 Chapter I Introduction efficiency of pollutants in raw harvested rainwater. Kinetic study of the treatment process revealed that the adsorption of contaminants was physiosorption (physical adsorption) with low values of activation energies of ECOD(359.84 J/mol) and

ETSS (215.91 J/mol)

Katsumata et al., (2004) characterized the adsorption of organic polyelectrolytes (hummic and fulvic acids) by bone char and found that the bone char was a useful adsorbent for humic substances compared to an activated carbon. A comparison of molecular weight distributions demonstrated conclusively that large molecular-weight components were adsorbed preferentially. They observed the surface conditions of the adsorbent before and after adsorption by a scanning electron microscope and found that the adsorption ability of the adsorbent was closely related to its pore size. The authors calculated the heats of adsorption by the Clapeyron-Clausius equation and found it over 50 KJ/mol, this means that the adsorption type appeared to be chemical adsorption.

28 Chapter I Introduction

IA.2 LIQUID MEMBRANE TECHNIQUE:

A membrane can be viewed as a semi permeable barrier between two phases. This barrier can restrict the movement of molecules across it in a very specific manner and the membrane must act as a barrier between two phases, then an immiscible liquid can serve as a membrane between two liquids or gases phases. The semi- permeable nature is essential for insuring that a separation will take place.

Liquid membrane (LM) separation technique provides a potentially powerful technique for effecting a diverse number of separation operations. Liquid membranes may be grouped into three types:

IA.2.1. Bulk Liquid Membrane (BLM):

This membrane is the easiest to prepare. It consist of an organic solution as the carrier, which is directly contacted the aqueous phase. This is done in the U- shaped tubes due to the different densities of aqueous and organic phases. Experimental work with this kind of membranes has a serious limitation due to the limited stirring range of the phases that can be achieved without disturbing the interface [Mark, (1990)]

IA.2.2. Supported Liquid Membrane (SLM):

A supported liquid membrane (SLM) can be made in the best three different geometries. (1) A planar or flat geometry is very useful for laboratory purposes. For industrial purposes, a

29 Chapter I Introduction planar geometry is not very effective, since the ratio of surface area to volume is too low. (2) Hollow fiber and (3) spiral wound moduls can be used to provide high surface area to volume ratios, which approach 10,000 m2/ m3 for hollow fiber and 1000 m2/ m3 for wound modules.

There are two primary problems associated with the use of SLM: solvent loss can occur by evaporation, dissolution or large pressure differences forcing solvent out of the pore support structure. Also carrier loss can occur due to irreversible side reactions or solvent condensation on one side of the membrane. Pressure differences can force the liquid to flow through the pore structure and leach out the carrier.

IA.2.3. Liquid Emulsion Membrane (LEM):

Liquid Emulsion membranes (LEMs), also called surfactant liquid membranes or liquid surfactant membranes, are basically double emulsions formed by emulsifying two immiscible phase (e.g. water droplets in an oil phase and vice versa) and dispersing the resulting emulsion in another external feed (or donor) phase containing solutes to be removed. Therefore, there are two different configurations for the LEM: (1) oil-in-water in-oil (O/W/O) system and (2) water-in-oil-in-water (W/O/W) system. The LEM process is very unique and promising in the separation of mixtures (e.g. industrial wastewater containing toxic organic or inorganic substances). The LEM separation process has several attractive characteristics: 1) relatively low energy consumption especially compared to other 30 Chapter I Introduction separation processes such as thermal evaporation, electrodialysis and pressure-driven membrane processes [Naim and Monir, (2003)], 2) rapid extraction with relatively high efficiency due to large surface area available for mass transfer [Frankenfeld and Li, (1987)], 3) potential for removing various toxic substances down to very low levels [Frankenfeld and Li, (1987) & Skelland and Meng, (1999)], 4) high selectivity especially when carrier agents are used in the membrane phase that bind exclusively with target compounds [Frankenfeld and Li, (1987)] and 5) easy regeneration of the spent emulsions by a demulsification process [ Li and Calo, (1992)]. As a result, since the LEM technology was first introduced by Li in 1968, the LEMs have been intensively investigated and demonstrated as an effective alternative technology for diverse separation and purification processes including metal extraction [Draxler and Marr, (1986) & Mikucki and Osseoasare, (1986) & Reis and Carvalho, (1993) & Urtiaga et al., (2000)], separation of organic acids and bases [ Halwachs et al., (1980) & Terry et al., (1982) & Yan et al., (1985) & Baird et al., (1987) & Wang and Bunge, (1990)], and pharmaceutical separations [Frankenfeld and Li, (1987) & Thien et al., (1988) & Itoh et al., (1990)]. Unfortunately, the widespread use of the LEM process has been limited due to the instability of emulsion globules against fluid shear. Breakup of emulsions and subsequent release of the internal receptor phase to the external donor phase would nullify the extraction process [Nakashio et al., (1988) & Skelland and Meng, (1996) & Wan and Zhang, (2002)].

31 Chapter I Introduction

IA.2.3.1 General description of liquid emulsion membrane.

Liquid Emulsion membranes (LEMs) consist of an aqueous phase (or internal stripping (or receptor) phase) stabilized by oil soluble surfactants and dispersed as very fine droplets (1 í 10 ȝm) inside an oil phase (liquid membrane phase). The resulting liquid membrane, or W/O emulsion, is further dispersed as emulsion globules (0.1í2mm) in another aqueous solution (external feed (or donor) phase). Target solutes in the external feed phase (e.g. contaminants in industrial wastewater) are transferred across the membrane phase into the internal stripping phase during an extraction process. In this W/O/W LEM (i.e. in contrast to an O/W/O type LEM), the oil phase functions as a selective barrier, or membrane. The solute mass transfer is driven by the concentration difference between the external feed phase and the internal stripping phase. Activity of target solutes in the internal phase is typically kept at near zero by using a trapping agent in order to maintain the concentration gradient, although it gradually decreases, until most of target solutes are extracted from the external phase.

IA.2.3.2 Liquid emulsion membrane process.

LEM process largely consists of three steps, which are emulsion preparation, solute extraction/emulsion separation, and demulsification. The configuration and key components of LEMs can vary depending on their application and the types of target solutes and the external feed phase treated. Choosing a

32 Chapter I Introduction suitable formulation of LEMs and optimizing the process are often pretty complicated.

Prior to the first step of emulsion preparation, it is required to prepare a membrane phase containing surfactant, extractant and the other additives such as polymer. The membrane phase is mainly composed of a solvent such as aliphatic and aromatic diluents. It is very critical to employ an appropriate solvent as membrane phase for an efficient LEM process. There are several considerations in choosing a suitable solvent [Ho and Sirkar, (1992)]: (1) low solubility in the external feed phase and the internal stripping phase in order not to lose the solvent during emulsion preparation and solute extraction, (2) compatibility with surfactant and extractant dissolved, (3) moderate viscosity balancing the membrane stability and permeability, (4) enough density difference from the aqueous phase for the fast process of emulsion separation, (4) low cost of its production, and (5) low toxicity because of environmental concern.

A surfactant is also one of key components of the membrane phase for the establishment of an effective LEM process. The surfactant composed of a polar head group and a non-polar tail is an emulsifying agent which not only determines the stability of emulsion but also affects several other parameters such as osmosis, water solubility, and mass transfer resistance [Draxler and Marr, (1986)]. The emulsifying agents form an interfacial film around the dispersed internal droplets and this film prevents or retards the droplet coagulation and flocculation [Cavallo and Chang, (1990)]. An appropriate surfactant should

33 Chapter I Introduction have the following properties. First, it should be soluble in the membrane phase only, neither the internal stripping phase nor the external feed phase in order not to lose any surfactant during operation. It should not react with the extractant in the membrane phase. If any, it would facilitate the decomposition of the extractant and subsequently affect the efficiency of the LEM process. In addition, it must have a low resistance to mass transfer and is stable against acids, bases, and bacterial activity. Last, demulsification must not be hindered by the surfactant. In this study, Span 80 (sorbitan monooleate with a molecular weight of 428) was used as an emulsifying agent for the following reasons: it provides relatively stable and easily demulsified emulsions and it shows less resistance to mass transfer than other surfactants like Span 20 (sorbitan monolaurate), Span 40 (sorbitan monopalmitate), Span 60 (sorbitan monostearate), Span 65 (sorbitan tristearate) [Draxler and Marr, (1986) & Draxler et al., (1988) & Nakashio et al., (1988) & Strzelbicki and Schlosser, (1989) & Lee and Chan, (1990) ].

Accordingly, the selection of a suitable carrier is vital for the high performance of the system. The selection of a suitable extractant is generally based on the thermodynamic and kinetic considerations. That is the selected extractant should thermodynamically favor to form a complex with a solute from the external feed phase and it should react kinetically fast for solute extraction. Therefore, the extractant with higher stability of the complex is more appropriate for the fast solute extraction from the external feed phase. However, it needs to be noted that 34 Chapter I Introduction the stability of the solute-extractant complex should be moderate for the ease of stripping process in the internal stripping phase.

IA.2.3.2.1 Emulsion preparation.

For the preparation of stable emulsion, the size of internal droplets should be very tiny as small as 1 – 3 ȝm in diameter. It can be accomplished by high input of energy density to W/O emulsion during emulsification. For the small LEM system, high-speed agitators with stirring rates up 20,000 rpm and/or ultrasonic emulsifiers are used to prepare emulsion. During emulsification, an internal aqueous phase containing a stripping agent is introduced. Like the extraction process with an extractant in the membrane phase, the selected stripping agent should be also thermodynamically favorable for the stripping process and exhibit a fast reaction with a solute-extractant complex. Interestingly, however, owing to the very large interfacial area of internal droplets provided, even the stripping process with very low reaction kinetics can be employed in an LEM system.

IA.2.3.2.2 Solute extraction and emulsion separation (settling).

The solute extraction step of an ELM process is initiated by dispersing the previously tailored emulsion into the external feed phase in a mixing contactor. During the dispersion operation with agitation in the external feed phase, emulsion is dispersed to form numerous small globules with a typical size

35 Chapter I Introduction of 0.1–2 mm in diameter. The consequent large interfacial area of emulsion globules is able to provide fast reaction in solute extraction process. Generally, higher agitation is desired for smaller emulsion globules, larger interfacial area, and resulting fast mass transfer. However, increasing the agitation speed increase shear rate and shear stress and thus, reduce the stability of emulsion, which causes breakage (or rupture) of emulsion liquid membranes. Hence, there is an optimal agitation speed in an ELM process. After the solute extraction, the emulsion separation from the treated external feed phase is completed by density difference in a settler.

IA.2.3.2.3 Demulsification.

Demulsification (i.e. the breaking of the loaded emulsion) is one of the critical steps in LEM process. After the solute extraction by LEMs, the spent membrane phase should be reused repeatedly and the enriched internal stripping phase is recovered or discarded. Hence, the separation of two immiscible liquids of oil membrane phase containing surfactant and extractant and internal aqueous phase containing highly concentrated solute is generally inevitable [Dines, (1982) & Sun et al., (1998)]. Demulsification has largely two major approaches: (1) chemical treatment and (2) physical treatment [Ho and Sirkar, (1992)]. Chemical treatment is adding a demulsifier to the loaded W/O emulsion and this method seems to be very effective in terms of the membrane recovery ratio. However, the added chemicals will change the properties of the membrane phase and thus, the

36 Chapter I Introduction recovered membrane phase cannot be reused. Besides, the additional cost for the demulsifers and their recovery are another flaws. Therefore, this method is not usually used in demulsification process. Physical treatment includes heating, centrifugation, ultrasonics, solvent dissolution, high shear, microwave radiation, porous glass or fiber membrane and the use of high-voltage electrostatic fields. It is reported that the loaded W/O emulsion can be effectively broken by those methods [Ho and Sirkar, (1992) & Li and Calo, (1992) & Larson et al., (1994) & Sun et al., (1998) & Chan and Chen, (2002) & Juang and Lin, (2004)]. IA.2.3.3 The factors affecting extraction rate/ permeability through LEM:

IA.2.3.3.1 Membrane thickness.

As the membrane thickness increases, the permeability decreases. Mixing of viscous compound (like glycerol) with surfactant has the effect of thickening the LEM, which results in decreasing the rate of diffusion process.

IA.2.3.3.2 Temperature.

It has been found that the temperature plays an important role in the diffusion rate. With the increase in the temperature the extraction rate too increases.

IA.2.3.3.3 Mixing rate.

The speed of agitation affects the extent of extraction to a great extent. It is observed initially extraction rate increases 37 Chapter I Introduction due to the increase in the mass transfer coefficient in aqueous phase but later the extraction rate decreases due to the hydrodynamic instability of membrane at higher speed leading to the breakage membrane.

IA.2.3.3.4 pH.

The pH of the external phase plays a very important role in the solute extraction particularly in the case of carrier- mediated transport. For a particular ion a particular pH or pH range is suitable.

IA.2.3.3.5 Feed phase solute concentration.

It is found that with increase in the initial concentration of feed phase solute, rate of separation will be slower as the separation progresses, although the initial rates are similar.

IA.2.3.3.6 Volume ratio of emulsion to external phase (treat ratio).

Volume ratio of emulsion to external phase when increases, extraction rate also increases due to increase in the capacity of the membrane and the internal phase for enhancement permeation and stripping of the solute.

IA.2.3.3.7. Internal stripping reagent concentration and the volume fraction of the internal phase:

However, the internal reagent concentration as well as the internal phase volume fraction cannot be increased indefinitely.

38 Chapter I Introduction

If the concentration of the internal reagent is beyond a limiting value, it will be harmful to the stability of the membrane and will increase water permeability in the membrane. This will lead to obvious swelling due to high osmotic pressure gradient between the internal and external phases.

IA.2.3.4 Literature survey on the liquid emulsion membrane in treatment of some hazardous substances produced from industrial wastewater:

Extensive work has already been reported for liquid membrane extractions. A series of metal species including alkali, alkaline earth, transition and heavy metals has been studied. Among these metals, chromium, mercury, copper, cadmium, cobalt, lead, and uranium are the most widely produced from industrial waste stream.

The following is a literature survey lists some of the liquid membrane processes published in the pullutants removal.

Talekar and Mahajani, (2008) studied the extraction and enrichment of cadmium(II) using di-2-ethylhexyl phosphoric acid (D2EHPA) dissolved in n-dodecane as carrier and methane sulfonic acid (MSA) as a strip phase. The complexation stoichiometric coefficient (n) and equilibrium constant (Kex) were determined by carrying out conventional liquidíliquid extraction studies. The factorial design method was used to see the importance of parameters. Emulsion preparation parameters such

39 Chapter I Introduction as carrier concentration, surfactant concentration, and internal strip phase (MSA) concentration were determined to get maximum extraction and enrichment. They studied The influence of operating process parameters on the performance of LEM process, i.e., residence time, speed of agitation, and treat ratio. A realistic simple model to aid the process design of LEM process has been developed.

PAN Lu-ting, (2006) used the emulsion liquid membrane technique to extract amino-J acid from industrial dye waste- water. The effects of stirring speed, ratio of the emulsion to water (Rew), ratio of the oil to internal phase (Roi) and membrane phase components on the extraction rate were investigated and optimized. The results showed that the extraction rate of amino-J acid approached 97% when the stirring speed was 300 r/min, Rew 1:6, Roi 1:1, trioctylamine (TOA) 3 mL/100 mL kerosene, and methylídidecyleíalcoholíacrylate (LMA-2) 3 g/100 mL kerosene, respectively. The author showed that the extraction rate had not changed with the oil phase reused for times.

Bourenane et al., (2003) studied the applicability of the Liquid Surfactant Membrane (LSM) process for the removal and the concentration of lead and cobalt. In this study, a phosphoric acid (di-2- ethylhexyl phosphoric acid or HDEHP) was used as extractant and monooleate of sorbitan (SPAN 80) as surfactant. The results show that it is possible to recover 98.83 % of cobalt and 94.21 % of lead in the inner phase after 2 minutes of contacting time with a concentration factor of 50 for lead and 50 for cobalt.

40 Chapter I Introduction

Kulkarni et al., (2002) discussed the application of a liquid emulsion membrane (LEM) process in the recovery of zinc from aqueous solutions. The role of a stripping agent is very important in the LEM extraction process. Various stripping agents, such as hydrochloric, sulfuric, nitric and methane sulfonic acids, were tested for the stability of membrane. Methane sulfonic acid outperforms the other acids as a strippant. Further importance was given to the stability of the liquid emulsion membrane during the extraction process. The important variables affecting the LEM permeation process of zinc in a mechanically agitated contactor (MAC), such as residence time for extraction, speed of agitation, organic diluents, surfactant concentration and internal strip acid concentration, were systematically investigated. The authors also described Emulsion swelling and breakage that occurred during these investigations. Finally, the static mixer (SM) device was shown to have a very good potential for LEM extraction of zinc as it outperforms MAC.

Hasan et al., (2009) studied the recovery of Cr (VI) from dilute HCl solution using liquid emulsion membrane (LEM). The liquid membrane is made up of Tri-octylphosphine oxide (TOPO) as a carrier, cyclohexane as an organic diluent, sodium hydroxide as a stripping solution and Span-80 (sorbitain monooleate) as an emulsifying agent. The selection of the extractant (TOPO) and the stripper (NaOH) was chosen on the basis of conventional liquid-liquid extraction studies. The authors investigated the important parameters affecting the permeation of Cr (VI) through the prepared membrane and

41 Chapter I Introduction these are, hydrogen ion concentration in the external aqueous phase, stirring speed of mixing the two phases, type of diluents, carrier concentration, stripper concentration, membrane to feed ratio and volume fraction. The effect of surfactant types and concentration on the stability of LEM were studied because of its important role in the permeation process.

Saravanan et al., (2006) investigate the removal of hexavalent chromium ions from aquesous solutions and industrial effluents by using liquid emulsion membrane (LEM) technique. They studied the effect of surfactant concentration, carrier concentration, agitation speed and emulsification time on the emulsion stability. The authors reported the effects of emulsion phase to the external phase (M/E) ratio and impeller speed on the percentage reduction of Cr (VI) ions in three types of effluents viz, synthetic effluent, electroplating effluent and tannery effluent. Also they showed that the liquid emulsion membrane is a very effective process by which the Cr(VI) ions can be removed successfully.

Synergic transport of metal ions of yttrim has been studied by Gaikwad, (2003) in a supported liquid membrane system using Aliquat-336 and TBP as anion exchange and solvating extractant, respectively. In this work, different experimental variables for supported liquid membranes has been studied such as stirring speed of source or receiving phase, pH of source phase, yttrium metal ion concentration, carrier concentration, concentration of complexing agent in receiving

42 Chapter I Introduction phase, and pH of receiving phase in presence of complexing agent. In addition to this, efficiency and stability of investigated supported liquid membrane have been explored.

Tatjna-Petroviü and Jönsson, (2002) studied the extraction of Cu (II), by supported liquid membrane using a flat PTFE membrane and di( 2-ethylhexyl) phosphate in kerosene as organic phase. The influence of donor phase flow rate on the extraction efficiency and the mass transfer coefficient was investigated. The dependence of extraction efficiency of Cu (II) on the presence of humic acids (HA) in donor phase was also investigated. The extraction efficiency decreases with increasing of humic acids concentration in donor phase, due to interaction of copper ions with humic acids. Fraction of Cu (II) binding with humic acids in donor phase was calculated using the theory of mass kinetic for analytical enrichment using SLM extraction formulated by Jönsson et al. They have shown that SLM extraction can be used as a method for investigation of metal- humic acid binings. The obtained calculated values of the binding of copper to humic acids in presence of 10 and 20 mg.dm-3 humic acids in donor phase are 25.6 and 55.8 %, respectively.

The concepts of apparent swelling and actual swelling are proposed by Wan and Zhan, (2002) to illustrate the relationship between the emulsion swelling (the osmotic and entrainment swelling) and the membrane breakage, focussing on the effect of the volume change caused by emulsion swelling and membrane

43 Chapter I Introduction breakage on the experimental results. Theoretical analyses indicate that “ zero” or “negative” swelling may occur under certain experimental conditions. A- bi-tracer method is further proposed and then used to measure the osmotic entrainment swelling and the membrane breakage simultaneously, only requiring some initial operation conditions and measurements of concentrations of both tracers in the external and internal phases. They have been experimentally proved that this new method is highly applicable in ELM process and provides a useful tool to specify the effects of membrane breakage, Osmotic swelling and entrainment swelling in the same experiment. “Negative” swelling may occur under certain operating condition, particularly when the electrolyte concentration in the external phase is higher than that in the internal phase. The experimental results also indicate that the effect of membrane breakage on the measurement of emulsion swelling should not be neglected to avoid measurement error. They showed that polymeric surfactant LMA is superior to other commercial surfactants as it imparts high membrane stability and small emulsion swelling.

The parameter affecting the stability of liquid emulsion membrane (LEM) for enrichment of nickel were studied by Kulkarni et al., (2000). They made up the liquid membrane of a carrier (di-2-ethylhexylphosphoric), organic diluent and an emulsifying agent ( sorbitan monooleate). They found that the swelling of the internal phase during extraction resuts in breakage of the emulsion, the role of pH is very important in the LEM process for extraction of nickel, a significant decrease

44 Chapter I Introduction in swelling was observed by maintaining the of the feed phase constant during extraction and a lower osmotic pressure difference between the external and internal phase brings about lower changes in the swelling and membrane breakdown.

Mahammed and Marimuthu, (2000) studied some surfactants known as bi- functional surfactants, which have an dual properties of extractant and emulsifier. Use such surfactant may eliminate the addition of an extractant to LEM system. In this study, polyethylene glycol was used as bi-functional surfactant in a LEM process for the extraction of metal ions from ternary (copper, nickel, and cobalt) aqueous solution. Dichloroethane, ammonium thiocyanate and potassium hydroxide were used as solvent, ligand and stripping agent respectively.

A liquid emulsion membrane (LEM) extraction rotating disc contactor ( RDC) column with auxiliary equipment has been designed and tested by Breembroek et al., (2000). This work proposed and verified a design procedure based on solvent extraction methods. The equipment was designed to reduce 100 ppm cadmium concentration in a 90l/h feed stream to 5%of its initial value, and to achieve a concentration factor for at least 12.5 % in the strip phase. Trilaurylamine (1%) in kerosene was used as the extractant solution. The RDC column diameter was 70 mm and its designed height was 2.2 m.

A mathematical model for batch extraction of Cr (VI) with liquid emulsion membrane from aqueous acidic solution using aliquat 336 as extractant and sodium hydroxide as 45 Chapter I Introduction stripping agent is reported by Banerjea et al., (2000). The model considered a reaction fronts to exist within the emulsion globule and assumed an instantaneous and irreversible reaction between the solute and the internal reagent at the membrane – internal droplet interface. Batch experiments were performed for separation of Cr (VI) from potassium dichromate solution of initial concentration in the 75-100 mg/l range. The membrane composition was selected to ensure negligible membrane breakage.

Mehta and Mahajani, (2010) studied, the extraction and enrichment of chromium (III), using di-2-ethylhexyl phosphoric acid (D2EHPA) in dodecane was carried out via the LEM process with aqueous methane sulfonic acid (MSA) as the strip phase. The complexation stoichiometric coefficient and equilibrium constant were measured by conventional liquid– liquid extraction studies. Emulsion preparation parameters, such as carrier concentration, surfactant concentration, and internal strip phase (MSA) concentration, were determined in order to obtain the maximum extraction and enrichment. The influence of operating process parameters on the performance of the LEM process, i.e. residence time, speed of agitation and treat ratio (TR), were studied. It was found that 83% extraction and nearly nine times enrichment of chromium(III) was obtained within 6 min of residence time at 400 rpm and 1:10 TR. A simple, but practical, model was developed in order to assist process design studies.

46 Chapter I Introduction

El-Reefy et al., (1998) studied the isolation of minor uarnium concentration from thorium matrix in HCl medium using liquid emulsion membrane (LEM ) containing TOPO as carrier, span 80 as surfactact and sodium citrate as stripping agent. The factors affecting the stability of LEM were investigated. Different parameters affecting the permeation process were also studied. The results obtained showed that, under certain condition it is possible to isolate ~ 98 %of U (VI) from 1.0 M HCl solution containing Th (IV). The isolate U was found to be contaminated with less than 3 % of Th.

Serga et al., (2000) studied the extraction of nickel ions by liquid membrane in an electric field using HDEHP as a carrier.

El-Reefy et al., (1993) investigated the permeation of thorium from HCl medium using liquid emulsion membrane (LEM) containing HDEHP in cyclohexane as carrier, polyethylene glycol dioleate as surfactant and HCl as stripping solution. The different parameters affecting the permeation of thorium through the LEM were studied. A method for separation of thorium-234form its parent uranium was developed based on the investigated system.

EL-Reefy et al., (1997) studied the extraction values of

U(VI), Th, Zr and Fe (III) from 0.1 M HNO3 solution by 0.1M TOPO in cyclohexane solution. Among these elements only U(VI) and Th were found to be stripped from their organic phase by 0.1 M sodium citrate solution. Cerium, copper and 47 Chapter I Introduction cadmium were not extracted by TOPO under similar conditions. Based on these equilibrium results, a liquid emulsion membrane (LEM) was prepared from TOPO/span 80/sodium citrate and the factors affecting its stability were studied. Permeation of U (VI) into this membrane was kinetically studied in detail.

Gürel et al., (2005) studied the removal of lead from storage battery industry wastewater by using liquid emulsion membrane (LEM) technique. The storage battery industry wastewater has an initial lead concentration of 4.2 ppm (average) and a pH value of 1.4. Emulsion liquid membrane consisted of kerosene and mineral oil as organic solvents, sorbitan monooleate (Span 80) as a surfactant, di-2-ethylhexyl phosphoric acid (D2EHPA) as a carrier or extractant, and sulphuric acid (H2SO4) as a stripping agent. The important variables affecting the ELM systems, such as organic solvents, surfactant, and carrier concentrations, internal stripping phase normality, external aqueous phase pH value, and normality of organic ligand added, have been investigated systematically. The system which adjusted to a pH value of 4.0, obtained the maximum lead removal in first 5 min of the treatment studies and exhibited a low turbidity and swelling at the end of the experiment.

Mâúu et al., (2005) presented the application of emulsion liquid membrane technique on simulated wastewater, which contained MB R 12 red reactive dye. Regarding the receiving aqueous phase two type of emulsion liquid membranes were

48 Chapter I Introduction tested, and the better results were obtained for the use of HCl solution as receiving phase of the emulsion membrane versus the use of NaOH solution as receiving phase. The transport of dye from feed aqueous phase into the receiving aqueous phase occurred only in the presence of trioctylamine (TOA) as carrier agent. The optimum working conditions for removal of reactive red dye from simulated wastewaters were the following: the contact time of 300 seconds, 0.5 M HCl solution as receiving phase and the slow stirring intensity of 200 rot/min. IB. OBJECT OF INVESTIGATION

The object of this investigation is to study the treatment of some hazardous substances such as heavy metals (e.g. lead, cobalt and strontium) and dyes (e.g. acid red 73 and acid blue 74) using either adsorption or liquid emulsion membrane techniques.

In the adsorption technique, 23-activated carbons will be prepared by either physical or chemical methods using bone char as precursor. In this concern, activated carbon will be prepared as follows: (i) by physical activation (either steam or N2 gas); (ii) by chemical activation either by mineral acids (HCl, HNO3, H2SO4 and H3PO4) or strong alkalies (KOH and NaOH) or organic compounds (sodium dodecyl sulphate, SDS). Sorption behavior of 5-adsorption systems will be examined. These are:

BC-SDS-2105: Pb, BC-S-2750 : Co, BC-N2-2500 : Sr, BC-SDS-2105: acid red 73 and BC-SDS-2105: acid blue 74

49 Chapter I Introduction and the factors affecting adsorption process will be described. In liquid emulsion membrane technique, the extraction of Co(II) ions using Cyanex 301 as extractant in cyclohexane from nitrate medium will be investigated to determine the suitable conditions for the permeation of Co (II) ions by the membrane under investigation. The factors affecting the stability of the prepared liquid emulsion membrane will be studied in terms of leakage percent at different parameters and also the factors affecting the permeation process for Co(II) ions. The physico-chemical characteristics will be determined using nitrogen adsorption technique, scanning electron microscopy (SEM) and FTIR- spectra. The atomic absorption and UV- spectroscopic techniques will be used for the determination of lead, cobalt, strontium, acid red 73 and acid blue 74 concentrations in their aqueous solutions.

50 Chapter II: Experimental

Chapter II EXPERIMENTAL

he experimental design was divided into two main Ttechniques: adsorption and liquid emulsion membrane techniques. In this concern;

(IIA) ADSORPTION TECHNIQUE: will include

i) Preparation of activated carbon from bone char by physical and chemical activations ii) Factors affecting adsorption of some metals ions (pb2+, Co2+and Sr2+) and organic dyes (acid red 73 and acid blue 74)

(IIB) LIQUID EMULSION MEMBRANE: will study i) Liquid – liquid extraction Investigation of cobalt (II) ions ii) Permeation of cobalt (II) ions using LEM (IIA) ADSORPTION TECHNIQUE

IIA.1 The Precursor:

Discard bone char (BC) residue from Pakin Co., Egypt was tested. This local biomass derived material is of animal origin. The (BC) residue is the resultant of a pyrolysis process occurred according to the following conditions.

51 Chapter II: Experimental

800°C/5 hr Animal bones ¾¾¾¾¾¾® (BC) residue + steams + oil + ammonia liquor Inert atmosphere

The residue content varies according to the type of animal (e.g. camel, buffalo or cattle) and its food. The (BC) residue is left in an inert atmosphere to avoid any oxidation. Then, it crushed and sieved to give constant particle size used for different purposes. The remaining size from sieving (30 mesh) is considered as carbidge (waste) of no use. This waste is the precursor of the new adsorbents.

IIA.2 Chemical Composition of the Precursor:

The elemental analysis of BC is listed in Table (II.1) based on a dry weight.

Table (II.1): Chemical analysis of BC used in this work.

Elements C H Cl N S ash content % 10.8 1.3 1.9 3.6 - 81.5

The tabulated data reveals that the main constituents are: ash (81.5); carbon (10.8); Nitrogen (3.6); hydrogen (1.3); and chlorine (1.9). The metallic residue (ash) of BC mainly contains:

Ca(PO4)2 78 %, CaCO3 2.5% and traces of Mg O, Fe2O3 and silica (SiO2).

52 Chapter II: Experimental

IIA.3 Preparation of Activated Carbons.

The preparation of activated carbon can be done either by physical or chemical activation using any carbonaceous raw material. In this concern, the bone char contains 10.8 % carbon may be used as a precursor for preparation of activated carbon.

In this concern, three categories of adsorbents were: 1- Bone char without any treatment 2- Activated carbon produced by physical activation (either

steam or N2 gas) 3- Activated carbon produced by chemical activation either by

mineral acids (HCl, HNO3, H2SO4, and H3PO4) or strong alkalies (KOH, NaOH) or organic compounds (SDS)

The total samples prepared from activated carbons were 23 samples as well as the precursor BC (used as it is) and the schematic diagram of the system used for the preparation of activated carbons from bone char is shown in Fig. (II.1).

II A.3.1 Bone char without treatment:

The bone char (BC) residue from Pakin Co., Egypt was used as it is without any treatment to assess its capability in treating water pollutants Table (II.2). The amount of bone char available is far in excess of any local uses and thus has posed a disposal problem. The advantage in its application as adsorbent is that there is no need to regenerate them because of their low production costs. 53 Chapter II: Experimental

II A.3.2 Physical activation:

II A.3.2.1 Steam activation:

This was performed by using the same setup in Fig.(II.1) with slight modification, where the system was mounted in an inclined position with an angle of 70 degree , so as to allow flow of the pyrolysis products. In each experiment, 25 g. of the raw material (BC) were placed in the reactor to be situated in the hot zone of the tubular furnace. The temperature was raised gradually (50 0C/10 min.) up to around 350 0C. Pure steam was then introduced through the heated mass, and heating was continued up to 7500 C. The product was soaked at this temperature for 1 and 2 hr., respectively to give activated carbons (BC-S-1750) and (BC-S-2750), Table (II.2)

II A.3.2.2 Nitrogen activation:

In this experiment, 25 g. of the precursor (BC) were placed in the reactor to be situated in the hot zone of the tubular furnace. The temperature was raised gradually (50 0C/10 min.) up to around 350 0C. Pure nitrogen was then introduced through the heated mass, and heating was continued up to 500 0C only . The product was soaked at this temperature for 1 hr. The activated carbon has notation (BC-N2-2500) as shown in Table (II.2).

54 Chapter II: Experimental

Fig. (II.1): Schematic diagram of the system used for the preparation of activated carbons from bone char.

The reactor (A) is a 4 cm inner diameter stainless steel tube fitted with screw caps of narrow tubes to pass condensates and vent volatiles, and an internal net near to one end so as to keep the material in the heated zone. This reactor was introduced into a calibrated tubular electric furnace (B) open from both ends. In each experiment, 25 gms of BC are placed in the hot zone of the reactor (A), and the heat was raised to required temperature.

II A.3.3. Chemical Activation: II A.3.3.1 Activation with acids: Bone char was activated chemically with acids: HCl or

HNO3 or H2SO4 or H3PO4 respectivly. In each experiment 25 g. of BC was soaked in 30 ml (3N) of acid solutions. The BC

55 Chapter II: Experimental mass was slightly agitated to ensure penetration of the acid throughout, then the mixture heated to 800C for 1hr and left overnight at room temperature to help appropriate wetting of the precursor. Next day, the impregnated sample was admitted into the reactor, which was then placed in a tubular electric furnace open from both ends. The temperature was raised at the rate of (500C/15 min) to the required temperature. The activation process was carried out at different temperatures: 500,700 and 900C for 60 min. The cooled product was washed with distilled water, then dried at 1100C, and weighted.

This gives carbons: BC-Cl-1500, BC-Cl-1700, BC-Cl-1900; using HCl ;

BC-N-1500, BC-N-1700, BC-N-1900; using HNO3

BC-SA-1500, BC-SA-1700, BC-SA-1900; using H2SO4

BC-P-1500, BC-P-1700, BC-P-1900 using H3PO4 , as shown in Table (II.2).

II A.3.3.2 Activation with bases: Bone char was activated chemically with bases ( KOH or NaOH). In each experiment 25 g. of BC was soaked in 30 ml (3N) of base solutions. The procedure were applied as described above with acids at the same activation temperatures. These give carbons: BC-K-1500, BC-K-1700, BC-K-1900; using KOH BC-Na-1500, BC-Na-1700, BC-Na1900; using NaOH as shown in Table (II.2).

56 Chapter II: Experimental

II A.3.3.3 Activation with 70 % KOH

Bone char was stirred with the concentration of 70 % KOH and heated to 80o C for 1 hr, then the mixture was left overnight. Then, the dry residue was placed in the reactor and immersed in the hot zone of the tubular furnace. The temperature was raised gradually (50 0C/10 min.) up to around 500 0C. The products were soaked at this temperature for 1hr , then cooled and weight determined BC-K70%-1500

II A.3.3.4. Sodium dodecyl sulphate treatment

10 gms of bone char was treated with 200 ml 10-2 M sodium dodecyl sulphate (10 % butanol, v/v). The treatment was carried out at 1050C for 2 hours on a hot plate with constant stirring. The heated mass was thoroughly washed with distilled water, decanted, dried at 60 0C in an oven overnight and stored in stoppered bottle. This carbon is denoted as (BC- SDS-2105) Table (II.2).

57 Chapter II: Experimental

Table (II.2): Different types of activated carbons from bone char

No Sample notation Preparation condition - BC Bone char without any treatment 1 BC-S-1750 Activation using steam at 750 0C for 1 hr. 2 BC-S-2750 Activation using steam at 750 0C for 2 hr. 0 3 BC-N2-2500 Activation using nitrogen at 500 C for 2 hr. 4 BC-Cl-1500 Activation using Hcl at 500 0C for 1 hr. 5 BC-Cl-1700 Activation using Hcl at 700 0C for 1 hr. 6 BC-Cl-1900 Activation using Hcl at 900 0C for 1 hr.

0 7 BC-N -1500 Activation using HNO3 at 500 C for 1 hr. 0 8 BC-N-1700 Activation using HNO3 at 700 C for 1 hr. 0 9 BC-N-1900 Activation using HNO3at 900 C for 1 hr.

0 10 BC-SA -1500 Activation using H2SO4 at 500 C for 1 hr. 0 11 BC-SA-1700 Activation using H2SO4at 700 C for 1 hr. 0 12 BC-SA-1900 Activation using H2SO4 at 900 C for 1 hr.

0 13 BC-P -1500 Activation using H3PO4 at 500 C for 1 hr. 0 14 BC-P-1700 Activation using H3PO4at 700 C for 1 hr. 0 15 BC-P-1900 Activation using H3PO4 at 900 C for 1 hr. 16 BC-K -1500 Activation using KOH at 500 0C for 1 hr. 17 BC-K-1700 Activation using KOH at 700 0C for 1 hr. 18 BC-K-1900 Activation using KOH at 900 0C for 1 hr. 19 BC-K70%-1500 Activation using 70 % KOH at 900 0C for 1 hr.

20 BC-Na -1500 Activation using NaOH at 500 0C for 1 hr. 21 BC- Na -1700 Activation using NaOH at 700 0C for 1 hr. 22 BC- Na -1900 Activation using NaOH at 900 0C for 1 hr. 23 BC-SDS-2105 Activation using Sodium Dodecyl Sulphate at 105 0C for 2 hrs.

58 Chapter II: Experimental

II A.4 Chemical and Reagents: All the solution used in this study were prepared from analytical reagent grade chemical, and double distilled water was used throughout this work for solution preparation as well for final washing of the glass wares.

Table (2.3): Chemical reagents used in this study Name Formula M. Wt Purity Supplied by Sodium dodecyl sulphate C12H25OSO3.Na 288.38 A.R B.D.H

Cobalt chloride CoCl2 129.837 A.R Sigma

Lead chloride PbCl2 278.1 A.R Sigma

Strontiun nitrate Sr( NO3)2 211.56 99 % B.D.H

Acetone C3H6O 58.08 A.R B.D.H

Ammonium thiocyante NH4SCN 76.12 A.R Sigma

4-(2-pyridylazo)resorcinol C11H9N3O2 215.21 A.R Aldrich

Acid Red 73 C22H14N4Na2O7S2 556.48 A.R Aldrich

Acid Blue 74 C16H8N2Na2O8S2 466.35 A.R Aldrich

Methylene Blue Basic blue 9 373.9 A.R Merck

Nitric acid HNO3 63.01 A.R B.D.H

Cyanex 301 bis(2,4,4- 322 A.R Fluka trimethylpentyl)dithiophosphinic acid

Cyclohexane C6 H12 84.18 A.R Merck

Hydrochloric acid HCl 36.46 A.R Merck

Phosphoric acid H3PO4 98.09 A.R Merck

Sulphoric acid H2SO4 98.08 A.R Merck

Span 80 C24 H44 O6 428.61 A. R Fluka

Sorbitan Sesquioleate C66H130O18 1175.7 A.R Fluka

Arlacel A C24 H42O5 410.594 A.R. Fluka

59 Chapter II: Experimental

II A.5 Methods: II A.5.1 Charaterization of the prepared carbons. II A.5.1.1 Physical characteristics. II A.5.1.1.1 Apparent density: The apparent density is equal to the mass (weight) of a quantity of carbon divided by the volume it occupies (including pore volume and interparticle voids). This can be measured simply by measuring the volume occupied by a given weight with the aid of a graduated cylinder.

II A.5.1.1.2 Bulk density (Packed density):

Bulk density was determined by ascertaining the volume of a known mass of sample in a graduated cylinder after tamping shows no further change in volume and the bulk density was calculated as: [Ahmedna et al., (1997)]

Bulk density ( g/ml) = Wt of material (g). ………...(II.1) Vol of packed dry material

II A.5.1.1.3 Ash content:

The gravimetric determination of ash contents is performed according to British Standard BS1016 and is summarized in the following section. A weighted quantity of carbons (1.0g) was placed in a porcelain crucible and set in a circulating air oven at115 ƚ for 4h.The samples were then weighted and placed in muffle furnace and heated at 800 0C for 1.5h. The crucibles were removed from the muffle furnace and allowed to cool in 60 Chapter II: Experimental desiccators and reweighted. Percent ash was calculated by [Mckay, (1996)]

%Ash = Remaining of solid wt (g) …………….(II.2) Orginal carbon wt (g)

II A.5.1.1.4 Moisture content:

The moisture content of content of activated carbon is often required to define and express its properties in relation to the net weight of carbon. The dry weight of an adsorbent is normally measured at a standard temperature of 105 0C under an inter atmosphere, for example nitrogen. This method avoids oxidation of carbonaceous adsorbents. The sample should be dried in this manner for 24h. and stored in desiccators [Mckay, (1996 )].

%The moisture = Weight after heating (g) x 100«..(II.3) Orginal carbon weight (g)

II A.5.1.1.5 Pore structure characterization:

In order to determine surface areas and pore characteristics of various samples, nitrogen adsorption/ desorption isotherms were measured at 77 K on automatic adsorption instrument (Quantachrome Instruments, Model Noval1000e series, USA) in relative pressure ranging from 10-6 to 0.999. Prior to the measurement, all the samples were crushed and powdered to shorten the time required for reaching equilibrium in the isotherm study and degassed at 250 0C under nitrogen flow for 24 hours. The cross section area i.e. the area occupied by an

61 Chapter II: Experimental adsorbate molecule in completed monolayer for the molecule at 77 K was taken as 16.2 ǖ2.

The surface area of the carbon samples were obtained by means of standard methods, pore volume and pore size distribution were subsequently calculated from the N2 adsorption data using NOVA Win 2.0 software.

II A.5.1.1.6 Scanning electron microscopy( SEM):

The scanning electron micrographs of selected carbons were carried by using a scanning electron microscope (SEM: LSMT 20 JOEL, JAPAN).

II A.5.1.2. Chemical Characterstics.

II A.5.1.2.1 pH Measurements:

When the pH of a particular adsorbent is mentioned, one refer to the pH of a suspension in distilled water. In this concern, one method entail preparing a suspension of 1g of adsorbent in 50 ml distilled water (pH =7.0). The suspension were heated to approximately 90 0C and stirred for 20 min. [Mckay, (1996 )] The suspensions were then allowed to cool to room temperature and the pH was measured. The pH meter was initially calibrated.

62 Chapter II: Experimental

II A.5.1.2.2. FTIR analysis:

Fourier Transformer Infra-Red specrophotometery was used to determine the surface functional groups on the sorbents. The infrared spectra of the prepared carbons, were recorded on a Perkin – Elmer FTIR- 1600 series infrared spectrometer as KBr discs.

II A.5.1.2.3 Elemental analysis:

Both treated and untreated carbons samples were subjected to elemental analysis. Carbon, hydrogen, and nitrogen contents were determined with a CHN Elemental Analyzer (Perkin-Elmer, Norwach, USA).

II A.5.1.2.4 Methylene blue test:

The literature indicates that the adsorption of methylene blue, from the aqueous phase is a useful tool for product control in the manufacture of activated carbons [Avom et al., (1997)].

In case of isotherm determinations a sample, 10ml of dye (MB) is introduced into a 100ml Erlenmeyer flask. The adsorbent to be tested, 0.02 gm, is added and the flask shaken for 48 hours at 25 0C. This procedure is repeated for several other concentrations of dye. A good mixing for the two phases was achieved using a mechanical shaker, Sankyo, Japan, the temperature was thermostatically controlled within ± 1 C. Complete phase separation of the two phases was attained by using a centrifuge obtained from (Chirama) Czechoslovakia, Universal which

63 Chapter II: Experimental provides a centrifugation range of 5000 rpm at the ambient temperature. To ensure homogeneity of the filtrates, the contents of the flask are stirred and the concentration of the dye is determined by using “ Shimadzu”, UV-visible Spectrophotometer model UV-160A, Japan; at Ȝmax= 664 nm for (MB). This apparatus is double beam recording Spectrophotometer and covers the UV- visible range 200-1100 nm, with a resolution of ± 0.4 nm and wavelength accuracy of ± 0.5 nm. In all measurements, two matched cm3 quartz cells with a path length of 1 cm were used for the sample and blank measurements. All measurements were carried out at laboratory temperature.

The residual concentration of methylene blue in the solution was determined.

The calibration curve of methylene blue was plotted in Fig. (II.2) as a relation between the concentration in (mg/l) vs. the absorbance obtained. It was found that the relation was linear up to concentration of 75 mg/l for methylene blue. The solutions with higher concentrations, dilution was required to operate the analysis in the linear Beer-Lambert region.

64 Chapter II: Experimental

1.6

1.4

1.2

1.0

0.8

0.6 absorbance

0.4

0.2

0.0 0 2 4 6 8 10 concentration(mg/l) Fig.(2.2) Calibration curve of methylene blue

Fig. (II.2): Calibration curve of methylene blue

II A.5.2. Sorption investigation.

II A.5.2.1 Lead, cobalt and strontium experiments:

Stock solution (1000 ppm) of lead, cobalt, and strontium was prepared by dissolving the required amount of the pure reagent in a least amount of double distilled water, and then transferring to a volumetric flask and completing to the mark with double distilled water. Various standard solutions were obtained by diluting certain amount of stock solution with the addition of double distilled water as required.

65 Chapter II: Experimental

II A.5.2.1.1. Analytical measurement

The concentration of Pb (II) and Co (II) in the sample solutions were determined with Shimadzu model 160A double- beam UV spectrophotometer. The concentration of Sr (II) in the sample solutions was determined by GBC- 902 atomic absorption spectrometry.

II A.5.2.1.1.1. Determination of lead:

The spectrophotometric determination of Pb (II) was done using 4-(2- pyridylazo) resorcinol ( PAR) solution.

PAR solution:

Dissolve 0.005g ( PAR) in 10 ml distilled water. Store the solution in an amber glass bottle.

Procedure:

To a 5-ml graduated flask was added a known amount of Pb (II) solution, 0.4 ml (PAR) solution, 2 ml buffer solution pH 10. The mixture was diluted to 5 ml with distilled water, then the absorbance at 520 nm against a reagent blank was measured.

The calibration curve of lead with (PAR) solution is shown in Fig (II.3).

66 Chapter II: Experimental

2.5

2.0

1.5

1.0 Absorbance

0.5

0.0 0 50 100 150 200 Concentration(mg/l) Fig.(2.3)Calibration Curve of lead by UV Spectrophotometer Fig. (II.3): Calibration curve of lead by UV spectrophotometer

II A.5.2.1.1.2. Determination of cobalt:

Spectrometric determination of Co (II) is performed by ammonium thiocyanate solution.

Ammonium thiocyante solution

Ammonium thiocyante solution is prepared by dissolving 5 gm of ammonium thiocyanate in 5 ml of distilled deionized water. Store the solution in amber glass bottle.

Procedure:

To the cobalt sample, 2.5 ml of acetone, 0.4 ml ammonium thiocyante solution, complete with distilled water to

67 Chapter II: Experimental the mark, 5 ml. The absorbance at 621nm against a reagent blank was measured.

Calibration curve for cobalt with ammonium thiocyante was carried out by taking different concentrations of cobalt ranging from 5-150 ppm; the curve is shown in Fig.(II.4) as absorbace vs. concentration.

0.35

0.30

0.25

0.20

0.15 absorbance 0.10

0.05

0.00 0 20 40 60 80 100 120 140 160 concentration(mg/l) Fig.(2.4)Calibration curve of cobalt by UV Spectrophotometer Fig. (II.4): Calibration curve of cobalt by UV spectrophotometer

II A.5.2.1.1.3. Determination of strontium:

The concentration of Sr (II) in sample solutions was determined by using GBC- 902 atomic absorption spectrometry. The standard concentration ranges from 5-300 ppm; the calibration curve is shown in Fig. (II.5) as absorbace vs. concentration.

68 Chapter II: Experimental

0.040

0.035

0.030

0.025

0.020

0.015 Absorbance

0.010

0.005

0.000 0 50 100 150 200 250 Concentration(mg/l)

Fig. (II.5): Calibration curve of strontium by Atomic absorbance

IIA.5.2.1.2 Factors affecting the removal of heavy metals: II A.5.2.1.2.1 Activated carbon selection. 24 carbon samples under studies were evaluated for their specific ability to adsorb lead, cobalt and strontium from aqueous solutions. These experiments were conducted at the original pH of the solutions. In this concern single dosage experiments were carried out by conducting 20 mg of each carbon with 25 ml of 200 ppm of lead, cobalt, strontium, nickel, and cadmium solutions using thermostatic shaker (Kottermann D-1362, Germany) water bath at 25±1 0C for 24h.

The solutions were filtered. The equilibrium concentration Ce was measured. The activated carbon of the maximum uptake was selected and utilized for the remaining tests. To correct for 69 Chapter II: Experimental

any adsorption of pb (II), Co (II) and Sr (II) on containers, control experiments were carried out without adsorbent. There is no adsorption by container wall.

Table (II.4): Preliminary test for selection of activated carbon samples. No Sample notation Uptake(mg/g) Sr (II) Pb (II) Co (II) 1 BC 8.92 33.07 23.175 2 BC-S-1750 150.75 63.75 32.87 3 BC-S-2750 143.75 88.37 53.25 4 BC-N2-2500 164.876 5.5 18.875 5 BC-Cl-1500 5.27 3.60 -- 6 BC-Cl-1700 6.5 2.83 5.28 7 BC-Cl-1900 3 .960 1.3 8 BC-N -1500 1.125 3.30 0.96 9 BC-N-1700 1.2 4.16 -- 10 BC-N-1900 4.22 0.74 4.8 11 BC-SA -1500 0.2 3.52 0.86 12 BC-SA-1700 0.85 4.58 1.76 13 BC-SA-1900 4.87 3.50 3.48 14 BC-P -1500 6.62 3.72 -- 15 BC-P-1700 0.475 6.4 0.42 16 BC-P-1900 2.07 3.52 5.28 17 BC-K -1500 1.15 2.35 3.48 18 BC-K-1700 0.77 1.49 -- 19 BC-K-1900 0.20 7.83 4.8 20 BC-K70%-1500 -- --- 133.12 21 BC-Na -1500 2.77 2.68 1.3 22 BC- Na -1700 4.35 7.36 -- 23 BC- Na -1900 5.3 8.9 4.36 24 BC-SDS-2105 155.5 151.125 20.125

70 Chapter II: Experimental

II A.5.2.1.2.2 Effect of contact time (Minimum contact time determination).

In order to determine the contact time required for the sorption equilibrium, the sorption kinetic experiments were conducted first. 20 mg of the adsorbent in 100 ml reagent bottles containing 25 ml of lead, cobalt, and strontium solution were mixed and placed in the shaker at 25± 1 0C for different time intervals. The adsorbent was finally removed by filtration, then lead, cobalt and strontium concentration were determined as mentioned above. The contact time required for complete metal adsorption was determined and utilized in the remaining tests.

II A.5.2.1.2.3 Effect of pH ( Optimum pH determination).

Influence of the pH on the metal adsorption was studied by using 25 ml of 100 ppm solution of cobalt, lead, and strontium, adjusted to an initial pH of 2-10 and agitated with 20 mg of carbon. The equilibrium concentration was measured after equilibrium contact time. The lowest solution pH for maximum metal adsorption was then selected and utilized for the remaining tests.

II A.5.2.1.2.4 Effect of adsorbate concentration.

The effect of metal ion concentration was studied by agitation 25 ml of different concentrations (5-150 mg/l) of cobalt, lead, and strontium solution with 20 mg of adsorbent for equilibrium time at pH 5.5, 6.5 and 7.5 for lead, cobalt and strontium, respectively.

71 Chapter II: Experimental

II A.5.2.1.2.5 Adsorption isotherm.

20 mg of carbon were placed in each 100 ml reagent bottles. 25 ml of cobalt, lead, and strontium solution, having various concentration was added. These suspensions were then shaken to achieve equilibration. Each mixture was filtered and the residual concentration was determined.

In all cases, the adsorption capacity ( qe ) which is given in mg of adsorbate/g of adsorbent, was calculated from the difference between the initial concentration (C0) and the equilibrium concentration (Ce) and the amount of used carbon as mentioned in equation (II.4) II A.5.2.2. Adsorption of organic dyes

Stock solution was prepared by adding appropriate amount of Acid Red 73 and Acid Blue 74 in deionized water. Various standard solutions were obtained by diluting stock solution with addition of distilled deionized water as required.

II A.5.2.2.1 Determination of acid red 73 and acid blue 74:

The concentration of acid red and acid blue were determined by the direct spectrophotometric method at (510 and 610 nm) for both Acid Red 73 and Acid Bblue 74; respectively against distilled water blank has been measured. The calibration curves of acid red and acid blue are presented in Figs. (II.6 ) and (II.7)

72 Chapter II: Experimental

10

8

6

4 Absorbace

2

0 0 20 40 60 80 100 120 140 160 180 200 220 Concentration(mg/l)

Fig. (II.6): Calibration curve of acid red 73 by UV spectrophotometer

2.0

1.8

1.6

1.4

1.2

1.0

0.8 Absorbance 0.6

0.4

0.2

0.0 0 10 20 30 40 50 Concentration(mg/l) Fig.(2.7)Calibration Curve of Acid Blue 74 by UV spectrophotometer Fig. (II.7): Calibration curve of acid blue 74 by UV spectrophotometer

73 Chapter II: Experimental

II A.5.2.2.2 Factors affecting the adsorption of acid red 73 and acid blue 74

II A.5.2.2.2.1. Selection of adsorbent.

To select a particular adsorbent to be used for the main experimental work, a fixed amount of each dry adsorbent (0.02 g ) and 15 ml aliquots of the stock solution of initial concentration C0 = 50mg/l, for each acid red 73 or acid blue74; respectively were shaken for 24h. Each mixture was filtered and residual acid red and acid blue content in the solution was determined.

II A.5.2.2.2.2 Kinetic studies.

Batch adsorption tests were conducted to study the effect of various parameters on adsorption efficiency of acid red and acid blue onto BS-SDS-2105 carbon. In this concern, 20 mg of adsorbent was shaken with 15 ml of the solution of initial concentration of 50 mg/l of acid red 73 or acid blue 74 for different time intervals. After the required time intervals, the suspension was filtered and the residual dye concentration were determined.

II A.5.2.2.2.3 Effect of adsorbent mass.

The effect of carbon mass on dye adsorption was studied by agitation 15 ml solution containing 50 mg/l of either acid red 73 or acid blue 74 with different carbon mass (5 -125 mg) for respective equilibrium times. The solution was filtered and the dye concentration was determined.

74 Chapter II: Experimental

II A.5.2.2.2.4 pH studies.

In order to investigate the effects of pH on acid red 73 or acid blue 74 adsorption, the pH of the solutions were adjusted from 2 - 11 by using dilute NaOH or HCl solutions. Then 15 ml of pH adjusted solution and 20 mg adsorbent were conducted at the determined equilibrium time. The pH value of the filtrate providing the maximum dye removal was determined.

II A.5.2.2.2.5 Equilibrium adsorption isotherm.

The equilibrium isotherms were determined by taking 15ml of various concentrations 10-150 ppm for acid red 73 or acid blue 74 with 20mg of BS-SDS-2105 carbon and were agitated for 48 hrs at room temperature. The equilibrium concentrations were determined.

II A.5.2.2.2.6 Temperature effect.

The temperature affects each of the adsorption rates and the degree of adsorption. So, it was necessary to decide if the adsorption process exothermic or endothermic. In this concern, 15 ml solution containing acid red 73 or acid blue 74 of concentration range (5 -75 mg/l) were agitated with carbon sample for 48 hrs. at various temperatures 25, 35, 45, 65 0C .

In all experimental runs, the uptake (qe) was calculated from the fallawing Eq. (II.4):

75 Chapter II: Experimental

v(C - C ) q = 0 e «««««««««««««««..(II.4) e M

Where:

C0 is the initial concentration of the solute (mg/L);

Ce is the residual concentration of the solute (mg/L); V is the volume of solute solution (ml); and M is the mass of the adsorbent used (g)

IIB LIQUID EMULSION MEMBRANE TECHNIQUE: IIB .1 Reagents: Cobalt chloride of analytical reagent grade (AR) was supplied by Sigma Cyanex 301 is bis (2,4,4-trimethylpentyl) dithiophosphinic acid extractant of analytical grade (Fluka) was used as received as carrier extractant for cobalt. Several surfactants from fluka have been tested such as Span 80 (sorbitan monooleate), Arlacel A and Sorbitan Sesquioleate. The diluents used were ( toluene, benzene and cyclohexane) from Merck.

IIB .2 Procedure:

The external aqueous phase is obtained by dissolving the chloride of cobalt into nitrate medium. The internal aqueous is of analytical pure (sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid solution ) from (Merck), which the type of stripping agent will be one of the parameters to optimize. The organic phase was cyanex 301/ in different diluents.

76 Chapter II: Experimental

II B.2.1 Liquid – Liquid Extraction Investigation

First, cobalt liquid-liquid extraction and equilibrium measurements were carried out by contacting equal volumes (25 ml) of aqueous and organic solution in thermostated shaker at 25 0C for 1 hour, a time in excess sufficient to allow equilibrium to be reached.

II B.2.2 Liquid Emulsion Membrane.

In general all the LEM experiments were prepared by mixing 25 ml of the organic extractant in the chosen diluent with proper surfactant. To this mixture, 25 ml of the stripping aqueous phase solution was added. Emulsion was prepared by slow adding aqueous solution of acid (strip phase) to the organic phase (membrane phase). The mixture was stirred by vigorous mixing using an ultra high-speed homogenizer (3000-7000 rpm) for 5 min. then excellent milky- white and stable emulsion was obtained. In LEM permeation, a known volume of the prepared LEM was added to known volume of the feed solution which contain cobalt into a thermostated vessel. The system was mixed with a magnetic stirrer of variable speeds ranging from 100-300 rpm and samples were withdrawn from the mixture at known time intervals and filtrated. The concentration of cobalt in the filtrate was determined using the spectrophotometer (Shimadzu model 160A double-beam UV spectrophotometer) using ammonium thiocyante method as mentioned before. The concentration of cobalt in the organic phase was calculated from the difference of the metal concentration in the aqueous phase before and after 77 Chapter II: Experimental extraction. The distribution ratio (D) was calculated as the ratio of the Co(II) Concentration in the organic phase to that in the aqueous phase and percentage extraction (%E) were calculated accordingly.

78 Chapter III Results and Discussion

Chapter III

RESULTS AND DISCUSSION

Two main techniques were used in this investigation; these are: III A. ADSORPTION TECHNIQUE. III A.1 Characterization of the Used Carbons. III A.1.1 Physical characterization of selected activated carbons. III A.1.1.1 Apparent and bulk density. Density is a property of all matter, which reveals much about the composition of the matter [Webb and Orr, (1997)]. There are two types of density associated with activated carbon called apparent and bulk (packed ) densities.

The apparent density is equal to the mass (weight) of a quantity of carbon divided by the volume it occupied (including pore volume and interparticle voids) while the bulk density is calculated using the tamped volume occupied by a certain mass of carbon. The density of the final products after activation depends not only on the nature of the starting material but also on the activation process [Lua and Guo, (2000)].

The experimental results of the apparent and the bulk density of physical and chemical activated bone char are represented in Table ( III.1). In physical activation, it is clear that,

79 Chapter III Results and Discussion as the time of activation increases from 1 hr. in sample BS-S-1750 to 2 hrs. in sample BS-S-2750, the apparent and bulk densities decreased. This is due to the fact that, the changes in densities are related to the reaction rate between carbon and steam, which essentially depends on the reaction time and activation temperature. Evidently, with increasing time of activation process, there is successive release of volatiles, gases, and oil or tars; consequently, the steam penetrates easily into the surface of bone char. In case of using nitrogen as activating agent in sample BS-N2-2500, the apparent and bulk densities are slightly decreased. This may be referred to the smaller size of water molecules than nitrogen molecules, consequently to the higher mobility for penetration.

Samples of BS-SDS-2105 and BC-K70%-1500 prepared from bone char through chemical activation, produced activated carbons with high density, in the range of 0.452-0.904 g /c.c. (Table III.1).

In pactical terms, granular activated carbons (GACs) with high bulk densities are preferred for general use. The American Water Works Association (AWWA) has set a lower limit of the bulk density at 0.25 g/c.c. for GACs to be of practical use [AWWA, (1991)]. Accordingly, all of the five carbons prepared from bone char either by physical or chemical activation, would fall within this guideline.

80 Chapter III Results and Discussion

Table (III.1): Apparent and bulk densities of activated carbons

Physical Apparent Bulk Chemical Apparent Bulk activation density density activation density density adsorbents g/c.c. g/c.c. adsorbents g/c.c. g/c.c. BC-S-1750 0.632 0.903 BC-SDS-2105 0.700 0.875 BC-S-2750 0.595 0.833 BC-K70%-1500 0.452 0.904

BC-N2-2500 0.603 0.822

III A.1.1.2 Ash content

Ash content is the indicator of the quality of an activated carbon; it is the residue that remains when the carbonaceous material is burned off. The ash content of the solid products depends on the chemical composition of raw materials (mainly inorganic compounds) and the degree of carbonization. The removal of volatile organic compounds in the thermal treatment results in enrichment of the inorganic material in the solid residues, which undergone deep carbonization [Zanzi et al., (2001)]. The high ash contents of activated carbons made from bone char can be explained by their high specific mineral content, especially their richness in silica (SiO2), iron oxide

(Fe2O3), magnesium oxide (MgO), and calcium oxide (CaO) and phosphorous oxide (P2O5).

81 Chapter III Results and Discussion

Table (III.2): ash content of various activated carbons

Physical Ash content Chemical Ash content activation % activation % adsorbents adsornents

BC-S-1750 92.40 BC-SDS-2105 77.29 BC-S-2750 76.03 BC-K70%-1500 70.32

BC-N2-2500 71.19

Bone char used as an effective agent for ion exchange contain up 90% of ash [Girgis et al., (1997)]. The values of measured ash content are given in Table (III.2). In case of physical activation, the ash content dropped somewhat with increasing activation time from 1 hr. in sample BC-S- 1750 to 2 hrs. in sample BC-S-2750 and with using another activation agent in sample BC-N2-2750 and the same observation was noticed in case of chemical activation samples. This suggested that, the amount of carbonaceous parts removed and inorganic parts removed or added depending not only on the type of oxidant but also on the activation time of the parent activated bone char. The chemisorptive properties of high ash content carbons may be advantageous in the treatment of flew gas containing acid contaminant such as SO2 and in the treatment of waste waters containing dissolved heavy metals [Bayer et al., (1995)].

III A .1.1.3 Moisture content

Generally, adsorbents are priced on a moisture-free basis, although sometimes moisture content may be stipulated, e.g.

82 Chapter III Results and Discussion

3,5 and 10 % w/w unless stored in airtight packing. Under humid conditions, adsorbents may adsorb perhaps 25 to 30% moisture, over a few months, and still appear dry [Mckay, (1996)].

According to Mckay, (1996), the moisture content does not adversely affect the adsorbent performance, in wastewater treatment, but merely acts as diluents. So that an additional quantity of adsorbent is required to provide the desired dry weight.

Furthermore, the behavior of water vapor in porous carbons is very different from that of non-polar molecules (owing to the hydrophobic or hydrophilic nature of the carbon surfaces) [Gauden, (2005)]. The process of water adsorption is very sensitive to the presence of surface functional groups on the carbon surface. They act as primary centers and initiate the process of adsorption via hydrogen bonding. Once the water molecule is adsorbed on the primary centers, it becomes a secondary adsorption site, and the clusters are formed. The resulting adsorbed water molecules can prevent pollutant access to hydrophobic regions on the activated carbon surface, and/or effectively block pollutant access to micropores [Li et al., (2002)]. It is also remarked that organic contaminant adsorption from aqueous solution necessitates the displacement of water molecules from the activated carbon surface [Daifullah and Girgis, (2003) & Pendleton et al., (1997)]. As shown in Table (III.3), the moisture content for activated samples are in the

83 Chapter III Results and Discussion range of 3.4 -10 %. Although the results showed that all the activated carbon are basic carbons, the presence of basic sites on the surface of carbon is not the only factor affecting adsorption of water vapor on activated carbon. The moisture content of different adsorbents agrees to a great extent with porosity detected by gas adsorption in latter section. Samples activated by steam have low porosity with low moisture content as compared by sample activated by nitrogen, which has high porosity with high moisture content; i.e. the adsorption of water from atmosphere depends on the porosity and surface chemistry (surface sites) of activated carbon and increases with both. This is in a good agreement with the results of earlier study [Heinen et al., (2000)]. But in case of chemical activation, the sample treated by sodium dodecyl sulphate has high porosity with low moisture content as compared to sample treated by KOH. The third factor affects adsorption of water vapor, is the ash content which increases the hydrophilicity of activated carbon [Tsai and Chang, (1994)].

Table (III.3): Moisture content of various activated carbons

Physical Moisture Chemical Moisture activation content activation content adsorbents % adsornents %

BC-S-1750 3.4 BC-SDS-2105 5.8 BC-S-2750 5.1 BC-K70%-1500 10

BC-N2-2500 6.3

84 Chapter III Results and Discussion

III A.1.1.4 Pore structure characterization. III A.1.1.4.1 Nitrogen adsorption isotherms: The physical adsorption of gases is a very useful technique for the characterization of porous solids and especially, microporous solids. Adsorption of nitrogen at its normal boiling point (77K) has become a standard in this approach.

An adsorption- desorption isotherms of N2 on activated bone char samples at 77 k are showen in Figs.(III.1) and (III.2). The shapes of adsorption isotherms can provide qualitative information on the adsorption process and it is apparent that all isotherms of all carbon series belonging to type IV, according to BDDT classification with an hysteresis loop typical of mesoporous materials. The isotherms exhibit hystheresis loop due to filling the pores by capillary condensation in mesopores [Sing et al., (1985)]. Thus, the activated bone char has not only micropores (pores with internal width of less than 2nm) but also mesopores (pores with internal width between 2 and 50 nm). The slope of curves gradually increases with increasing

P/P0 at the highest pressure region near saturation, indicating a wider pore size distribution. The IUPAC recommened a new classification of hysteresis loops, which categorized loops into four groups from H1-H4 [Sing et al., (1985)]. In our case the loop of H4 type is indicative of slit-shaped pore produced by tubular pores which contain a narrow constriction or closed pores of the ink bottle type [Pradhan and Sandles, (1999)]. In the present investigation, although the adsorption isotherms for all samples are similar, the adsorption capacities are significantly different according to type of activation and time of

85 Chapter III Results and Discussion activation. The distinction can be established between nitrogen adsorption isotherms of different samples based on the widening of their knee and shape of the low pressure portion of the isotherms. The shape of low – pressure portion of the isotherms depends on the microporosity and graphitic order of carbon surface [Darmstadt at al., (2001)]. There is no sharp knee appeared in any of the isotherms, reflecting the presence of small amount of microporosity ( supper and ultra micropores < 1 nm). A more rounded knee appear in most of the isotherms pointing to a widening of the microporosity that extend to high degree of mesoporosity which conformed by appearing of hystersis loop in their isotherms [Villar-Rodile et al., ( 2002)].

86 Chapter III Results and Discussion

BC-S-1750 Volume (cc/g) Volume

Relative pressure, P/P0

BC-S-2750 Volume (cc/g)

Relative pressure, P/P0 Fig.(III.1): Nitrogen adsorption isotherms at 77 k for physical-activated carbons.

87 Chapter III Results and Discussion

BC-N2-2500 g) Volume (cc/ Volume

Relative pressure, P/P0

Fig.( III.1): Continued

88 Chapter III Results and Discussion

BC-SDS-2105 Volume (cc/g)

Relative pressure, P/P0

BC-K70%-1500 Volume (cc/g)

Relative pressure, P/P0

Fig. (III.2): Nitrogen adsorption isotherms at 77 k for chemical -activated carbons. 89 Chapter III Results and Discussion

III A.1.1.4.2 Pore parameter analysis.

Based on the results of nitrogen adsorption isotherm, the structure of the carbon was characterized using the BET equation in the range of relative pressure 0.05 up to 0.35 and 2 the specific surface area (SBET, m /g) was calculated. The total pore volume (Vp, ml/g) was estimated from the amount of nitrogen adsorbed at relative pressure of 0.95 and the mean pore radius from, r BET = 2 Vt/ S BET ,was calculated assuming cylindrical model pore opened at both ends.

Table (III.4): Characteristics of activated carbons calculated from BET model and t-plot Sample Activation Type BET T –plot Method notation

SBET SEXT SMicro Vp VMicro VMesop Vmeso/Vp (m2/g) (m2/g) (m2/g) (ml/g) (ml/g) (ml/g) (%)

BC-S-1750 27.03 16.49 10.542 0.034 0.009 0.025 74 Physical-activation BC-S-2750 48.93 13.996 34.93 0.040 0.019 0.021 53

BC-N2-2500 117.71 44.593 73.11 0.10 0.041 0.056 56

Chemical-activation BC-SDS-2105 81.90 47.68 34.21 0.094 0.022 0.072 77 BC-K70%-1500 3.19 1.75 1.43 0.0044 0.002 0.0024 55

As shown in Table (III.4), the fraction of the total pore system located in micropores was calculated from t-plot method using the following equations:

Micropore volume (Vmic) = intercept x 0.001547

Mesopore volume (Vmeso) = total pore volume (Vp) – micropore volume.

% micropore = (Vmicro/ Vp) x 100

% mesopore = (Vmeso / Vp) x 100

90 Chapter III Results and Discussion

Parameters calculated by the Brunauer–Emmett–Teller (BET) equation [Brunauer et al., (1938)] and the t-plot method

[Lowell and Shields, (1991)] from N2 sorption isotherms are shown in Table (III.4). For samples activated by physical activation, the results show that sample BC-N2-2500 gives the highest surface area of 117.71 m2/g with highest pore volume of 0.1ml/g and the mesopore volume represents 56 % of total pore volume. This means that the effect of using nitrogen as activating agent instead of steam in physical activation is felt in terms of two competing mechanisms; micropore formation and pore widening; [Rodriguez-Reinoso and Molina-Sabio, (1992)]. The sample BC-S-1750 is essentially a mesoporous carbon, as the mesopore content reaches a value of 73 % of total pore volume and BET surface area 27.03 m2/g. But for sample BC-S-2750, micropores and mesopores formation is the dominating mechanisms as the mesopores volume represents 53 % of the total pore volume with surface area 48.93 m2/g. This means that by increasing the hold time the surface area increased and mesoporesity decreased as shown in Table (III.3)

In case of chemical activation it was found that the use of sodium dodecyl sulphate in sample BC-SDS-2105 is conducted as it give active carbon with highest surface area (81.90 m2/g) and highest mesoporesity (76% ) than using potassium hydroxide in sample BC-K70%-1500 which give lowest surface area (3.19 m2/g) and low mesoporosity (54 %).

91 Chapter III Results and Discussion

III A.1.1.5 Scanning electron microscopy.

The scanning electron microscopy images gave insight into the bone char structure with respect to particle size and shape. The cellular structure of bone char before activation showed a relatively heterogeneous morphology of particles and channels ( Fig III.3) The particles had irregular shapes with edges and corners. The dark areas are macropores and the pale grey areas represents the carbon matrix.

Fig.(III.3): Scanning electron microscopy of bone char without activation

Figs.(III.4) and (III.5 ) represent the morphology of the resulting activated carbon prepared via physical and chemical activation methods, respectively. It can be clearly seen that physical and chemical activations show some changes in the surface of the particles before and after activation. The different pore structure of the activated carbon prepared from either physical activation (using steam or nitrogen as activating agent)

92 Chapter III Results and Discussion or chemical activation (using sodium dodecyl sulphate or KOH) are observed, which depend upon different reaction mechanisms.

The dark areas are greater than the pale gray areas in physical activation using nitrogen gas compared to that of steam activation. This implies to the higher surface area of BC-N2-2500. On the contrary, the chars activated either by SDS or KOH has irregular carbon matrix (different shapes and sizes). It was clear that, activated carbons treated by SDS consists mainly of large particles size and have more cannels like structure than the untreated bone char. Nitrogen adsorption isotherms of the physical and chemical activated bone char samples indicated that, the pore system is mainly composed of mesopores.

93 Chapter III Results and Discussion

BC-S-1750

BC-S-2750 Fig. (III.4): Scanning electron micrograph of the physical-activated carbons

94 Chapter III Results and Discussion

BC-N2-2500

Fig. (III.4): Continued

95 Chapter III Results and Discussion

BC-SDS-2105

BC-K70%-1500

Fig.(III.5): Scanning electron micrograph of the chemical-activated carbons.

96 Chapter III Results and Discussion

IIIA.1.2 Chemical characterization of selected activated carbon. III A.1.2.1 FTIR analysis The FTIR spectrum of the bone char is presented in Fig.(III.6) as reported by [Bahrololoom et al., (2009)]. It shows a series of bands in the mid-infrared region. These bands can be divided into three main categories associated with phosphate, carbonate and hydroxyl groups. The bands located at 1043, 567, 603 and 962 cmí1 are due to the phosphate group. Tanaka et al., (2003) have also observed two bands at 603 and 1051 cmí1 due to the stretching vibrations of the phosphate group. The bands which appear at 873 , 1417 and 1456 cmí1 are associated with the carbonate group. The small bands at 2341, and 2358 cmí1 are due to ketone [Yakout, (2005)]. There is also a relatively broad band at 3436 cmí1 which is attributed to the hydroxyl group.

Fig.(III.6): The FTIR spectrum of bone char

97 Chapter III Results and Discussion

Fig. (III.7):FTIR spectra of physical-activated carbons

a) BC-S-1750 b) BC-S-2750 c) BC-N2-2500

98 Chapter III Results and Discussion

Fig. (III.8): FTIR spectra of chemical-activated carbons a) BC-SDS-2105 b) BC-K70%-1500

99 Chapter III Results and Discussion

The FTIR spectra of physical and chemical activated bone char samples are presented in Figs. (III.7) and (III.8), respectively. They provide a number of spectral details indicating some changes have occurred as compared by the spectrum of untreated bone char. The band around 3400 cm-1 characteristic for -OH becomes more broader and higher intense in case of sample -1 BC-N2-2500. A new small peak located at 3567 cm was appeared in case of samples BC-S-1750 and BC-S-2750, this may be due to carboxyl groups [ Shawabekeh, (2004)]. For the sample activated by KOH (BC-K70%-1500), the adsorption band at 3400 cm-1 for the – OH becomes more broader and higher intense with a new broad band at 3179 cm-1. The new absorption band -1 located at 2923 cm is mainly due to methylene group (-CH2- stretching) [Yakout, (2005)]; this band appeared in all of the activated carbons under investigated and becomes more intense in case of BC-K70%-1500 sample. The band at 2341 cm-1 was shifted to higher wave number 2377 cm-1and appears as a shoulder after physical and chemical activation of bone char samples. This may be referred to carbon dioxide release [Bahrololoom et al., (2009)]. The peak appeared at around 1600 cm-1, attributed to the presence of conjugated C=O group such as diaryl ketone, quinone and /or carbonyl groups near hydroxyl group, becomes highly intense. A new peak at 1540 cm-1 was also appeared; its intensity increased with increasing time of activation from 1 hr. to 2 hrs. in sample BC-S-2750 and by using nitrogen as activating agent in sample BC-N2-2500 instead of steam in case of sample BC-S-1750. The bands at

100 Chapter III Results and Discussion

1417 and 1456 cmí1 characterizing the carbonate group, become more intense in the following order:

BC-N2-2500 > BC-S-2750> BC-S-1750 & BC-SDS-2105 > BC-K70%-1500

III A.1.2.2 pH:

The pH of carbon is an important parameter of interaction at the interface of the adsorbate containing fluid and carbon, which contain other non carbonceous constituents [Tsai et al., (2001)]. The surface chemical nature of the prepared carbons was estimated by measuring their pH values; the obtained data are listed in Table (III.5). The prepared carbons show basic surfaces (pH = 7.85 -10.43). It is well established that steam activation at high temperature form basic oxides, which have chromene and pyrone type structures [Boehm, (1966)].

Table (III.5): The measured pH values of the prepared cabons.

Carbon type pH BC-S-1750 9.25 BC-S-2750 9.15

BC-NO2-2500 10.43 BC-SDS-2150 7.85 70% BC-K -1500 9.73

101 Chapter III Results and Discussion

Hassler (1963) reported that the pH of most commercial activated carbons is due to the inorganic constituents (ash) originating from the precursor or those added during manufacture. This means that there is a positive correlation between pH and ash contents; however, this is not the case of the carbon samples under investigation. As shown in Fig. (III.9), there is a negative correlation between these two variables which indicates that there is no leaching of inorganic constituents from these carbon samples which affect their pH values; this recommends the suitability of the prepared carbons for water treatment.

10.5

10.0

9.5

9.0 pH

8.5

8.0

7.5 70 75 80 85 90 95 % Ash

Fig. (III.9): Scatter graph of ash and pH of various carbon samples.

102 Chapter III Results and Discussion

III A.1.2.3 Methylene blue test

The dye adsorption tests help to determine the capacity of carbon to adsorb molecules of a particular size. The mesoporosity of carbon is often studied by methylene blue adsorption and this also serves as a model compound for removing organic contaminants and colored bodies from aqueous solutions [Yenisoy-Karakas et al., ( 2004)]. It gives an indication of adsorption capacity of an activated carbon towareds molecules having similar dimensions to methylene blue [Aygun et al., (2003) & Vitidsant et al., (1999)].

The results of the methylene blue uptake by the activated bone chars, either by physical or chemical routes, are listed in Table (III.6). In this concern, the bone char activated via the physical route by steam at 750 0C for 1 hr gives a higher methylene blue value while that activated by nitrogen at 500 0C for 2 hrs gives a lower value of methylene blue test. The bone char activated via chemical route using SDS gives higher uptake of methylene blue while that activated by KOH gives lower uptake value of methylene blue index.

103 Chapter III Results and Discussion

Table (III.6): Results of methylene blue uptake by various carbons.

Carbon type Methylene blue uptake (mg/g) BC-S-1750 54.5

BC-S-2750 52.63

BC-N2-2500 50

BC-SDS-2105 58.82

BC-K70%-1500 21.68

These results of methylene blue uptake could be related to the BET surface area and the fraction percentage of micropore and mesopores volumes (% mic. and %meso.). From results of Table (III.7), it is clear that the uptake of methylene blue decreases by increasing surface area (SBET, mg/g) and

% micropore volume (Vmiro/Vp) but increases by increasing

% mesopore volume (Vmeso/ Vp). This indicats that the mesopore volume is represents the dominant factor that affecting this type of adsorption rather than the micropores, i.e. methylene blue is mainly accessible to mesopores and inaccessible towards micropores. Therefor the mesoporosity of carbon is often studied by methylene blue adsorption. In this concern, the surface area of sample BC-S-1750 (27.03 m2/g) 2 was lower than that of the sample BC-N2-2500 (117.71 m /g) but the former has methylene blue uptake equals to 54.5 mg/g greater than the latter 50 mg/g. This is due to BC-S-1750 has a

104 Chapter III Results and Discussion

higher mesoporosity (74%) but BC-N2-2500 has a lower mesoporosity (56 %). Similary, the chemically activated carbon BC-SDS-2105 has high fraction mesoporosity (77%); consequently, it has higher methylene blue uptake (58.82 mg/g) than that of KOH activated carbon which has (55%) mesoporosity and its methylene blue uptake is only 21.68 mg/g.

Table (III.7): Relationship between methylene blue uptake and porous characterstics of carbons

Methylene SBET Vmicro/Vp Vmeso/Vp Activation Type notation blue uptake 2 (m /g) (mg/g) (%) (%)

Physical-activation BC-S-1750 27.03 54.5 26.4 74 rout BC-S-2750 48.93 52.63 47.5 53

BC-N2-2500 117.71 50.00 41 56

Chemical- activation BC-SDS-2105 81.90 58.82 0.022 77 rout BC-K70%-1500 3.19 21.68 0.002 55

III A.1.2.4 Elemental analysis

The elemental analysis of untreated and treated samples are shown in Table (III.8 ). In case of physical activation, it can be seen that with the increase of activation time using steam from 1 hr. in sample BC-S-1750. to 2 hrs in sample BC-S-2750 , the carbon content increased from 5.79 % to 7.36 %. If nitrogen gas was used as activant for 2 hrs at 500 0C in sample

BC-N2-2500, there was further increase in carbon content 18.13 %. This may be due to release of volatiles during pyrolysis that results in elimination of the non-carbon species and enrichment

105 Chapter III Results and Discussion of carbon [Aygun et al.,(2003 )]. There is a significant increase of surface area with incteasing carbon content. According to current knowledge, carbonization at high temperature (> 600 0C) yields materials with a low amount of oxygen surface groups and basic character [Figueiredo et al., (1999) and Pereira et al., (2003 )] as all oxygen-containing groups are removed during the carbon activation. However, the resultant surface adsorbs significant quantities of oxygen upon re-exposure to air at room temperature. The relatively high oxygen content in activated carbon, after exposure to air, is attributed to the stabilized form of the active carbon [ Strelko et al., (2002)].

Table (III.8): Elemental analysis of activated carbons.

C H N O Ash Activation type notation C/H (%) (%) (%) (%) (%) Bone char (untreated) BC 10.8 1.3 3.6 0.9 8.30 81.5 BC-S-1750 5.79 0.59 ---- 1.22 9.81 92.40 Physical-activation BC-S-2750 7.36 0.75 --- 15.86 9.81 76.03

BC-N2-2500 18.13 1.79 0.78 8.11 10.12 71.19 BC-SDS-2105 14.49 1.03 ---- 7.19 14.06 77.29 Chemical- activation BC-K70%-1500 7.48 1.14 --- 21.06 6.56 70.32

The formation of considerable quantities of oxygen- surface groups during carbon activation is evident from elemental oxygen composition of the starting bone char and activated carbons [Strelko et al., (2002)]. Activated samples show higher oxygen content than the untreated sample but the hydrogen contents decreased in all activated samples, except in BC-N2-2500 sample, compared with untreated samples. The 106 Chapter III Results and Discussion atomic ratio of C/H have been widely used to represent the respective aromaticity of the carbon [Lewis, (1982)]; i.e the ability for organic adsorption increases as confirmed by methylene blue test. Physical activation using nitrogen as an activating agent, introduces small amounts of nitrogen § 0.8 %). This is not surprising because it has been noted that nitrate or nitro surface groups are present in small amounts on the surface after treatment [Pradhan and Sandles, (1999)]; this is confirmed by FTIR analysis. III A.1.3 Adsorption characterization conclusion.

This research examines the preparation of 23-activated carbons through physical or chemical activation processes using bone char as precursor. In both methods, the development of porosity is different in terms of practical procedures and mechanism. In physical activation, the generation of porosity takes place via gasification leading to the production of the activated carbon with its distinct pore structure.

In chemical activation process, the precursor is mixed with a chemical substances, such as SDS or KOH then carbonized and washed to produce the activated carbon. Following the thermal decomposition of the precursor, the chemical substances reacts with product causing a reduction in the evolution of volatile matter and inhibition of the particle shrinkage. Once the chemical substances is removed by exhaustive washing, a large amount of porosity is produced [Helena et al., (1991) & Rodrguez-Reinoso and Molina- Sabio, (1992)].

107 Chapter III Results and Discussion

We can conclude that physical and chemical activation lead to formation carbons having different physical and chemical properties as shown in Table ( III.9). It is clear that a wide variety of activated carbons could be obtained with various characteristic properties depending on activation temperature and activating agent.

Physical and chemical activation lead to activated carbons which have different degrees of surface heterogeneity. The heterogeneity of carbon surfaces results from two sources known as geometrical and chemical ones. Geometrical heterogeneity is the result of differences in size and shape of pores, cracks and pits. Chemical heterogeneity is associated with different functional groups, mainly oxygen groups that are located most frequently at the edges of the crystallites, as well as with various surface impurities. Both chemical and geometrical heterogeneities contribute to the unique sorption properties of bone char based carbons.

Particularly, the development of micropores and mesopores is of great importance because it allows the porous carbons to adsorb various types of chemical compounds from gas or liquid streams. Although the relative size of the adsorbate molecules have a significant effect on adsorption capacity; the chemical nature of both the adsorbate and adsorbent also play a significant role. For this reason, in order to characterize the adsorption capacity of a material, the determination of its surface area would not be enough; sorbents have the same surface area often exhibit different adsorptive behaviors.

108 Chapter III Results and Discussion

Table (III.9): Characteristic parameters of carbon samples derived from bone char

Parameter Range

Apparent density (g/ml) 0.452-0.700 Bulk density (g/ml) 0.822-0.904 Ash content (%) 70.32-92.4 Moisture content (%) 3.4-10 BET surface area ( m2/g ) 3.19- 117.71 Micropore volume (ml/g ) 0.002-0.041 Mesoopore volume (ml/g ) 0.0024-0.072 Average pore radius (nm) 1.64-2.77 pH 7.85- 10.43 Methylene blue uptake (mg/g) 21.68 – 58.82

III A.2 Lead, Cobalt and Strontium Removal

Increased use of metals and chemicals in process industries has resulted in generation of large quantities of effluent that contain high levels of toxic heavy metals and their presence causes environmental-disposal problems due to their non-degradable and persistence nature. In addition, mining, mineral processing and extractive metallurgical operations also generate toxic liquid wastes [Goyal and Ahluwalia, (2007) & Olayinka et al., (2007) & Olayinka et al., (2009)]. The removal of toxic heavy metal contaminants from aqueous waste streams is currently one of the most important environmental issues being investigated [Igwe et al., (2005) & Mondal, (2009) & Suthipong and Siranee, (2009)].

109 Chapter III Results and Discussion

Industrial wastewaters may contain compounds that are non-biodegradable or toxic to biological organisms. This may include heavy metals such as (cadmium, mercury, lead, zinc, cobalt, copper, arsenic, strontium, chromium, …..etc).

Lead does not appear to be an essential element for life for any organism, but there is plenty of evidence on its toxicity. Lead is toxic to humans, as it substitutes in tissue, and accumulates there. The toxic level of lead to fish was 100-15000 µg/L according to Harrison and Laxen, (1981).

Cobalt is an essential element for living organisms. As shortage of cobalt in the herbage gives rise to weakness, emaciation, anaemia and eventually death. But in high doses, cobalt can be toxic. According to Liebmann (1958), cobalt concentration in the range of 30-100 mg/L is toxic to fish, whilst about 5 mg/L reduces the self- purification process in natural waters.

Small concentration of strontium may be of benefit to animals, but high concentrations are toxic, as they upset the metabolism of calcium and phosphorus.

Adsorption on low cost-adsorbent for removal of toxic metals from wastewater has been investigated extensively. These materials include thioglycolic cocoyam biomass [Horsfall and Ayebaemi, (2004)], brewery biomass [Kim et al., (2005)], sodium hydroxide modified lang (Imperata cylindrica) leaf powder [Hanafiah et al., (2006)].

110 Chapter III Results and Discussion

The aim of this section was to investigate the use of activated bone char in the removal of some metal ions, namely, lead, cobalt and strontium, from their aqueous solutions.

III A.2.1 Activated carbon selection. The main task of this section was to investigate and to select the best carbon sample suitable for the removal of lead, cobalt, and strontium from wastewater streams. Table (III.10) illustrates the results obtained for the removal of toxic metal ions namely, lead, cobalt and strontium from their aqueous solution using untreated and activated bone char.

Table (III.10): Preliminary tests for untreated and activated bone char Uptake (mg/g) Carbon type Pb(II) Co(II) Sr(II)

BC 68.25 22.625 123.87

BC-S-1750 63.75 32.87 150.75

BC-S-2750 88.37 53.25 143.75

BC-N2-2500 5.5 18.87 164.87

BC-SDS-2105 151.12 20.125 155.5

BC-K70%-1500 -- -- 133.12

There is a significant difference in the ability of the 5-activated carbon samples to adsorb lead, cobalt and strontium ions from their aqueous solutions. The observed large variations in the uptake indicate different interaction mechanisms between

111 Chapter III Results and Discussion carbon surface and metal containing species present in the aqueous solution.

As shown from Table (III.10), sample BC-SDS-2105 is found to be superior in the removal of lead but sample BC-S- 2750 exhibited the highest capacity for removal of cobalt, and sample BC-N2-2500 was selected for removal of strontium. Therefore, these 3-adsorption systems, namely, BC-SDS- 2+ 2+ 2+ 2105:Pb ; BC-S-2750:Co and BC-N2-2500:Sr were chosen for further investigations. In this concern, various parameters of adsorption process: equilibrium time, carbon mass, initial concentration and pH will be discussed.

III A.2.2 Adsorption kinetic studies

Kinetic of adsorption were carried out in order to determine the effect of time on the adsorption process and to identify the rate of reaction taking place at the adsorbent- adsorbate interface. In this concern, Fig. (III.10) shows the effect of reaction time on removal of lead, cobalt and strontium in the 3-adsorption systems. The removal curves are single, smooth and continuous leading to saturation, suggesting possible monolayer coverage of the specified metal ion on the surface of each adsorbent. It was clear that the amount adsorbed of Pb(II), Co(II) and Sr(II) increases with increasing contact time. The equilibrium steady state was reached at 120, 60 and 120 min. for lead, cobalt and strontium, respectively (Fig. III.10). The time required to reach the equilibrium state of 120 min. for lead ions in solution systems was in good agreement with previous results [Akhtar and Qadeer, (1997) & Shekinah et al., (2002)]. We can conclude that, the contact

112 Chapter III Results and Discussion time required for the metal ion is short and this result is very important because equilibrium time is one of the most important considerations for economical wastewater treatment applications.

The curves shown in Fig. (III.10) present a double nature, this means that the adsorption process comprised two steps: a rapid initial step followed by a much slower one. The adsorption of lead by sample BC-SDS-2105 was very fast during the first 30 min. of contact, where about 70% of equilibrium capacity was obtained, while the remaining adsorption density was only achieved after further 90 min. Similarly, about 83 % of cobalt was adsorbed by sample BC-S-2750 within 30 min., followed by further 30 min. to attain equilibrium. Also, about 85% of strontium was adsorbed by sample BC-N2-2500 within 60 min., while the rest (15 %) of adsorption capacity was achieved after further 60 min. These two distinct stages in metal ion adsorption were also reported by Tran et al., (1999).

Yubin et al., (1998) explained the two-stage of adsorption; during the first stage the metal ion adsorbed on the external surface and in the macropores of the asorbent where the resistance towards metal ions to reach these surfaces is small. As the adsorption proceeds more and more metal ions diffuse through macropores, mesopores and micropores to reach the total surface area within the adsorbent particles. However, the rate of diffusion in such pores decreases with increasing contact time and consequently, the adsorptive capacity increases more slowly as time elapsed until equilibrium was attained [Yubin et al., (1998)].

113 Chapter III Results and Discussion

120

100

80

60 (mg/g) e q 2+ 40 BC-SDS-2105:Pb BC-S-2750:Co2+ 20 2+ BC-N2 -2500:Sr

0 0 50 100 150 200 250 Tim e (m in.)

Fig. (III.10): Effect of time on adsorption of lead, cobalt and strontium ions III A.2.2.1 Adsorption dynamics: Rates of adsorption are usually measured by determining the change in concentrations of adsorbate with the adsorbent as a function of contact time. The kinetic rate constant of lead, cobalt and strontium adsorption were described by pseudo-first order rate of Lagergren and pseudo-second order rate expression as applied by Ho and Mckay, (1999&2000) t log( qe – qt) = log qe - K1 ( ) ….. 1 st- order (III.1) 2.303 t 1 t = 2 + … 2nd–order (III.2) q t K 2 q e q e

Where qt and qe are the amount adsorbed (mg/g) at time t and at equilibrium time, respectively and K1, K2 are the first and second order-rate constants of adsorption, respectively.

114 Chapter III Results and Discussion

K1 can be obtained from the slop of straight line of plot log

(qe – qt) vs. t from Eq. (III.1) and K2 from slop of plot t vs. t/qt using Eq. (III.2). The results of the kinetic plots were shown in Figs. (III.11) and (III.12 ).

2.0

BC-SDS-2105:Pb2+ 1.5 BC-S-2750:Co2+ 2+ BC-N2-2500:Sr 1.0 ) t -q

e 0.5 log(q 0.0

-0.5

-1.0 0 20 40 60 80 100 120 140 160 180 200 Time (min.)

Fig. (III.11): Pseudo-first order adsorption kinetics of lead, cobalt and strontium.

115 Chapter III Results and Discussion

3.5

BC-SDS-2105:Pb2+ 3.0 BC-S-2750:Co2+ 2+ 2.5 BC-N2-2500:Sr

2.0 e

t/q 1.5

1.0

0.5

0.0 0 50 100 150 200 250 Time(min.) Fig.(III.12): Pseudo-second-order sorption kinetics of lead, cobalt, and strontium Fig. (III.12): Pseudo-second order sorption kinetics of lead, cobalt and strontium.

Table (III.11): Comparison of the pseudo first- and second-order adsorption rate constants and the calculated and experimental qe values for Pb(II), Co(II) and Sr(II) Model Parameter Pb (II) Co (II) Sr (II)

Pseudo First-order model qe,exp (mg/g) 115.24 105 74.54

-1 K1 (min ) 0.0352 0.0283 0.3222

qe,calc (mg/g) 87.068 67.407 71.833

R2 0.9933 0.9999 0.9989

-4 -3 -4 Second-order model K2(g/mg.min) 6.49x10 1.04x10 5.47x10

h (mg/g min) 9.21 12.367 3.748

qe,calc(mg/g) 119.189 109.051 82.781

R2 0.9952 0.9993 0.9989

116 Chapter III Results and Discussion

Table (III.11) lists the calculated results of the kinetic parameters K1, K2, qe,calc and the initial adsorption rate 2 h=(K2qe ) along with the corresponding correlation coefficients. As can be seen from Table ( III.11), both pseudo-first order and pseudo-second order rate expressions give good correlation coefficients as ( R2 > 0.99 for lead, cobalt and strontium ). For lead and cobalt the calculated qe values obtained from pseudo- second order rate expression (119.189 and 109.051 ) are in good agreement with the experimental data (115.24 and 105 ) respectively. This observation confirms the applicability of Eq.( III.2); i.e. the adsorption reaction can be approximated to pseudo-second order. This suggested that the pseudo-second order adsorption mechanism is predominant and that the overall rate of the adsorption process is most likely to be controlled by the chemisorption process [Chairat et al., (2005)]. Similar results were reported by Parab et al., (2005)

The reaction involving in the pseudo-second order are greatly influenced by the amount of metal on the surface of adsorbent and the amount of metal adsorbed at equilibrium. This means that the rate of reaction is directly proportional to the number of active sites on the surface of adsorbent [Krishnan and Anirudhan, (2002)].

According to pseudo-second order model, the adsorption rate dqt/dt is proportional to the second order of (qe- qt). Since BC-SDS-2105 and BC-S-2750 samples have relatively high equilibrium adsorption density qe, the adsorption rates become very fast and the equilibrium times are short. Such short equilibrium times coupled with high adsorption capacity indicate high degree of affinity between metal ions and carbon samples [Chiou and Li, (2002)].

117 Chapter III Results and Discussion

In case of strontium, the pseudo-first order kinetic model is the predominant due to that, the calculated value qe,cal (71.83) 2 agrees very well with qe,exp (74.54) and the R was 0.9989 as listed in Table (III.11). This suggests that adsorption of Sr2+ on sample BC-N2-2500 is controlled by first-order kinetic model.

III A.2.2.2 Diffusion studies.

Sorption kinetic data were further processed to determine whether pore-diffusion or intra-particle diffusion is rate-limiting step in the adsorption process and also to find the rate parameters for both types of diffusion.

In the model developed by Weber and Morris (1963), the rate of intra-particle diffusion is a function of t0.5 and can be defined as follows:

0.5 q t = kpt …………………………………..(III.3)

The intra-particuler diffusion rates (kp) were determined 0.5 from the plots of qt versus t as shown in Fig.(III.13). If intra- particle diffusion is a rate-controlling step, then the plots should be linear and pass through the origin. As can be seen, the plots have the same general features. They have an initial curved portion, followed by an intermediate linear portion, and a plateau. The initial portion of these plots is due to external mass transfer, the intermediate linear part is due to intra- particule diffusion, and the plateau is due to the equilibrium stage where intra-particle diffusion starts to slow down due to extremely low solute concentrations in the solution [Namasivayam and Ranganathan, (1995) &Wu et al., (2005)]

118 Chapter III Results and Discussion

The slope of linear portion has been defined as intra- particle diffusion rate parameter (kp). The kp values obtained are 6.95, 10.831 and 8.626 mg.g-1min-0.5for lead, cobalt and strontium, respectively.

On the other hand, the intercept of the plot reflects the boundary layer effect. The larger the intercept, the greater is the contribution of the surface sorption in the rate-limiting step [Chaturvedi et al., (1988) & Vadivelan and Kumar, (2005)], and it follows the sequence: Pb2+ > Co2+ >Sr2+ suggesting higher contribution of surface sorption in case of lead is less than cobalt and less than strontium.

Ho, (2003) has indicated that it is essential for the qt vs. t0.5 plots to go through the origin if the intra-particle diffusion is the sole rate-limiting step [Ho, (2003)] . Since this was not the 0.5 case in the present work, as the qt vs. t plots have intercepts, it may be concluded that the intra-particle diffusion was not the only rate-controlling step. The adsorption mechanism of these metal ions from their aqueous solutions is a rather complex process, probably a combination of external mass transfer, and intra-particle diffusion which contribute to the rate determining step [Mohan et al., (2002)]. This behavior is predicted when a large initial fraction of the reaction is controlled by intra- particle diffusion.

119 Chapter III Results and Discussion

120

100

80

60 (mg/g) t q Lead 40 Cobalt Strontium 20

0 0 2 4 6 8 10 12 14 16 t0.5(min.0.5) Fig.(III.13): Intra-particle diffusion plots for adsorption of lead, Fig. (III.13): Intra-particle diffusion plots for adsorption of lead, cobalt and strontium.

As the multi nature of intra-particle diffusion plot confirms the presence of both film and pore diffusion, in order to predict the actual slow step involved, the kinetic data were further analyzed using the Boyd kinetic expression. This kinetic expression predicts the actual slowest step involved in the sorption process for different sorbent-sorbate systems. The Boyd kinetic expression is given by Boyd et al., (1947):

2 F = 1- (6/ʌ )exp(-Bt) …………..(III.4) And q F = t …………..(III.5) qa

120 Chapter III Results and Discussion

Where: qt represents the amount of metal adsorbed (mg/g) at any time t (min.), qĮ is the amount of metal adsorbed (mg/g) at infinite time (mg/g), F represents the fraction of solute adsorbed at any time t,

Bt is a mathematic function of F, was calculated for each value of Femploying Reichenburg equation [Reichenburg, (1972)]

Bt = - 0.4977- ln (1- F) ………………………………(III.6)

The calculated Bt values were plotted against time t as shown in Fig. (III.14). The linearity test of Bt vs. time plots was employed to distinguish between the film diffusion and particle-diffusion controlled sorption. If the plot of Bt vs. time (having slope B) is straight line passing through the origin, then the adsorption rate is governed by particle diffusion mechanism otherwise it is governed by film diffusion [Mohan and Singh, (2002)]. From Fig.(III.14), it was observed that the plots was linear for lead (up to 60 min.), cobalt ( up to 120 min.) and strontium ( up to 120 min.), but the straight line does not pass through the origin confirming the observed behavior of the Weber-Morris equation (Eq. III.3). Thus, particle diffusion is the most probable operating mechanism and does not control the kinetics of metal ions sorption [El-Shahawi et al., (2005)]. i.e. external mass transport mainly governs the rate-limiting process [Kumar et al., (2005)].

121 Chapter III Results and Discussion

3.5 Pb2+ 2+ 3.0 Co Sr2+ 2.5

2.0 t B 1.5

1.0

0.5

0.0 0 20 40 60 80 100 120 Time, min. Fig.(III.14): Boyd plots of the kinetics for lead, cobalt and strontium adsorption.

Fig. (III.14): Body plots of the kinetics for lead, cobalt and strontium adsorption.

III A.2.3 Effect of initial concentration of metals.

The effect of lead, cobalt and strontium concentration was studied by using varyious initial concentrations from 5-200 ppm. The results are shown in Fig.(III.15). It is clear that as the initial concentration increases the equilibrium uptake qe increases till saturation. This indicates that the sorption process appears to proceed rapidly when the number of available sites is much larger than the number of metal species that can be adsorbed and more favorable sites became involved first. As the metal concentration increases, the high-affinity sites begin to reach saturation, and energetically less favorable ones (low affinity surface sites ) become involved in the sorption process 122 Chapter III Results and Discussion causing reduction of removal efficiency [Saleem et al.,(1993) & Seco et al., (1999)]. It is evident from Fig.(III.15) that the amount adsorbed on the solid phase at lower initial concentration of adsorbate was smaller than the corresponding amount when higher initial concentration were used.

130 120 110 100 90

80 70 (mg/g) e

q 60

50 Lead 40 Cobalt 30 Strontium 20 10 0 0 50 100 150 200 Initial Concentration, C0 Fig.(III.15): Influence of initial concentration of lead, cobalt, and strontium, Fig. (III.15): Influence of initial concentration of lead, cobalt and strontium, on equilibrium uptake (qe).

Considering the effect of metal concentration, Weber, (1967), reported that the relationship between soluble concentration and the rate of sorption []= 1/ t ln(C0 /Ce helps to describe how the mechanism of removal taking place. In case of strict surface adsorption, a variation of rate should be proportional to the first power of concentration (i.e. linear), however, when pore diffusion limits the sorption process, the relationship between concentration and the rate of reaction will not be linear [Knocke and Hemphil, (1981) & Deshkar et al., (1990)].

123 Chapter III Results and Discussion

Fig.(III.16) shows that a direct linear relationship exists in case of lead, cobalt, and strontium adsorption. This suggests that the limiting step of adsorption kinetics is represented by transport phenomena inside solid particles and on surface. The data also confirmed that both mass transfer and pore diffusion are important in determining the sorption rates.

0.035 Pb2+ 0.030 Co2+ Sr2+

) 0.025 -1

0.020

0.015

0.010 Reaction rate (min.

0.005

0 50 100 150 200

Initial concentration,C0 Fig. (III.16): Effect of initial concentration on sorption rate of lead, cobalt and strontium

III A.2.4 Equilibrium adsorption isotherm.

Adsorption data for wide range of adsorbate concentrations are most conveniently described by adsorption isotherm, which relate adsorption density qe (metal uptake per unit weight of adsorbent) to equilibrium adsorbate concentration in the bulk fluid 2+ 2+ 2+ phase, Ce. The adsorption isotherms of Pb , Co and Sr were obtained in an attempt to get a more through insight to the 124 Chapter III Results and Discussion adsorption mechanism and maximum adsorption capacity of lead, cobalt and strontium onto the activated carbons.

In this concern, the experimental results obtained for the adsorption of lead on sample BC-SDS-2105; cobalt on sample

BC-S-2750 and strontium on sample BC-N2-2500 at room temperature (25±1 0C) are given in Fig.(III.17). Initially, the amount adsorbed raises rapidly over the initial stage of adsorption where low Ce and qe values exist. This behavior indicates that there were plenty of readily accessible sites available on the used adsorbents. Eventually, a slow approach to equilibrium at high concentrations occurred. As more sites are filled, it becomes more difficult for the solute molecules to find a vacant site available for adsorption and/or the difficulty of molecules in penetrating the layer of adsorbed metal ion already covering the surface sites. As a result, the rate of adsorption decreases giving a plateau covers a wide range of solution concentration i.e. considerably increasing the Ce values for a small increase in qe.

120

100

80

60 (mg/g) e q

40 Lead Cobalt 20 Strontium

0 0 20 40 60 80 100 120 140

C e(mg/l) Fig. (III.17): Equilibrium adsorption isotherms of lead, cobalt and strontium.

125 Chapter III Results and Discussion

Data obtained from adsorption isotherms are fitted to the linearized forms of Langmuir, Eq. (III.7) and Freundlich isotherm Eq.(III.8):

Ce 1 Ce = 0 + 0 ……………………………(III.7) qe bq q 1 logq = log K + logC …………………………….(III.8) e n e

Where: qe is the equilibrium uptake (mg/g).

Ce is the equilibrium concentration (mg/l), and q0 and b are the Langmuir constants related to the maximum adsorption capacity corresponding to complete monolayer coverage and energy of adsorption, respectively.

K and n are the Freundlich constants, n gives an indication of favorability (adsorption intensity) and K the capacity of adsorbent (adsorption capacity).

126 Chapter III Results and Discussion

1.4 1.3 Lead 1.2 Cobalt 1.1 Strontium 1.0 0.9 0.8 0.7 (g/l) e

/q 0.6 e

C 0.5 0.4 0.3 0.2 0.1 0.0 0 20 40 60 80 100 120 140

Ce(mg/l) Fig.(III.18): Langmuir plots of Lead,Cobalt and Strontium sorption. Fig. (III.18): Langmuir plots of lead, cobalt and strontium sorption

2.1 Lead Cobalt 2.0 Strontium 1.9

1.8 e 1.7 log q 1.6

1.5

1.4

1.3 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

log Ce Fig.(III.19): Freundlich plots of Lead, Cobalt and Strontium sorption. Fig. (III.19): Freundlich plots of Lead, cobalt and strontium sorption

127 Chapter III Results and Discussion

Langmuir and Freundlich plots are given in Figs. (III.18) and (III.19). The adsorption parameters were calculated by the slope and intercept of Langmuir and Freundlich equations and listed in tables (III.12) and (III.13), respectively. Table (III.12) shows that the Langmuir constants ‘b’, which reflect the binding strength between sorbent and sorbate, are different for the metal ions under investigation. In this concern, the b-value is more for cobalt onto sample BC-S-2750 than either for lead onto sample

BC-SDS-2105 or strontium onto sample BC-N2-2500, thereby indicating strong bonding of Co (II) with carbon surface in comparison to either Pb2+ or Sr2+; i.e. the metal ions exhibit different sorption characteristics: i.e., some are strongly adsorbed e.g.Co2+and Pb2+, whereas the weakly adsorbed are Sr2+ ions .

According to the Langmuir equation, q0 is the limiting amount of adsorbed metal ion required to give a complete monolayer on the carbon and b, is a measure of the relative adsorption affinity. From Table (III.12), the adsorption capacity or the monolayer coverage determined by Langmuir isotherm follows the order Pb2+ > Co2+ > Sr2+, whereas adsorption affinity, b, the sequence trend obtained in the present work is Co2+ > Pb2+ > Sr2+. It is worth to mention that the adsorptive capacity does not follow the same order as the adsorption affinity. This is logic considering that q0 values depend on the solute concentration and the adsorbent mass while the coefficient b is proportional to e ¨H/RT, where the driving force is the enthalpy change, ¨H.

128 Chapter III Results and Discussion

Table (III.12): Langmuir parameters for investigated metal ions

q0 b R2 r Metal ion (mg/g) (L/mg) Correlation dimensionless coefficient separation factor

Pb2+ 128.534 0.1079 0.9991 0.085

Co2+ 109.52 0.124 0.9967 0.075

Sr2+ 87.260 0.0779 0.9943 0.113

Table (III.13): Freundlich parameters for investigated metal ions R2 Correlation coefficient Metal ion K (mg/g) n

Pb2+ 29.769 3.114 0.95965

Co2+ 26.546 3.216 0.9785

Sr2+ 16.253 2.720 0.9244

From Table (III.13), the magnitude of K and n, the Freundlich constants, showed easy uptake of each cations. The constant K is a general indicator of the capacity of adsorbent for the solute while the constant n is a general indicator of the strength of interaction forces of the solute by the adsorbent. Both K and n determine the shape of the isotherm. From Table (III.13), it is obvious that lead and cobalt adsorbed considerably better than strontium. The values of n between 1 and 10 represent good and favorable adsorption and higher values of K indicate high affinity [Rengaraj et al., (2002)]. By comparing the calculated correlation coefficients, R2 listed in Tables (III.12 ) and (III.13) for Langmuir and Freundlich models, it 129 Chapter III Results and Discussion can be concluded that the experimental data fit the Langmuir model better than the Freundlich model, over the whole range of concentrations. The correlation coefficients of Langmuir isotherm for the 3-metal ions are higher than 0.99. The high fitting to the Langmuir model for each metal ion suggests that once metal ion occupies a site, no further adsorption can take place at that site, then the adsorption is limited with monolayer coverage and the surface is relatively homogeneous in the term of functional groups[Gücek et al., (2005)]. In other words, the Langmuir model is applicable when there is a strong specific interaction between the surface and adsorbate so that single adsorbed layer forms due to the chemical nature of the sorption (chemisorption interaction) [Mohan et al., (2002)]. To distinguish between physical and chemical adsorption, the adsorption data can be further interpreted by Dubinin- Radushkevich (D-R) isotherm [Dubinin and Radushkevich, (1947)]. This isotherm is more general than Langmuir isotherm because it does not assume a homogenous surface or a constant adsorption potential [Kilislioglu and Bilgin, (2003)].

The D-R equation is given as. 2 qe = qmexp(-Bİ ) ……………………………(III.9)

With æ 1 ö İ = RT ln ç1+ ÷……………………………(III.10) è Ce ø Where :

qe is the amount adsorbed at equilibrium.

qm is the maximum amount adsorbed and can be called the adsorption capacity.

130 Chapter III Results and Discussion

B is a constant related to the adsorption energy (mol2/kJ2). İ the potential energy of the surface. R is the gas constant ( 1.987 kJ/mol K), T is the absolute temperature.

The constant B gives the free energy E ( kJ/mol) of the transfer of 1 mole of solute from infinity to the surface of adsorbent and can be computed using the relationship:

1 E = …………………………………(III.11) 2B

The D-R equation can be linearized as:

2 ln qe = ln qm – Bİ …………………………(III.12)

2 A plot of ln qe versus İ gives straight lines as shown in 2 2 Fig.(III.20). The values of qm (mg/g) and B ( mol / kJ ) were obtained from the intercept and slope of straight lines, respectively, and are lised in Table (III.14). Thus, the mean free energy of adsorption E (kJ/mol) can be calculated from Eq. (III.11). The constants B and the correlation factors R2, are listed in Table (III.14). Therefore, the D-R equation can be used to estimate not only the maximum adsorption capacity, but also an average free energy value unique to the adsorbate- adsorbent system.

131 Chapter III Results and Discussion

-0.5 Lead Cobalt -1.0 Strontium

-1.5

-2.0 (mmol/g) e -2.5 lnq

-3.0

-3.5

-4.0 0 5 10 15 20 e 2 x10-3

Fig. (III.20): D-R plots of Lead, cobalt and strontium adsorption

The values of qm calculated from the D-R model are lower than those calculated from the Langmuir model, Table(III.14). The q0 values determined from Langmuir model are always located at some point beyond the whole range of the adsorption isotherm, for this reason it is better called the maximum adsorption capacity. The q0 from Langmuir model may be considered as a monolayer capacity when the plateau of the isotherm does not exhibit any rising with the increase of the equilibrium concentration. The D-R model, on the other hand, considers only the adsorption points of the isotherm preceding the plateau of the isotherm and therefore the qm values determined from the D-R plots are of more significance. The energies of adsorption listed in Table (III.14) are proportional to the fraction of mesopores of the adsorbents; sample BC-SDS-2105 has energy and fraction mesoporosity of 22.62 kJ /mol and 77%, respectively, while sample BC-S-2750 has 10.62 kJ/mol of

132 Chapter III Results and Discussion

energy and 53 % mesoporosity and sample BC-N2-2500 has 12.86 kJ/mol of energy and 56 % mesoporosity. This finding is in agreement with the interpretations that the existence of mesopores facilitates the adsorption of the adsorbate onto higher energy sites [Hsieh and Teng, (2000) ].

The sorption free energy has been evaluated to get some information of the nature of bonding i.e. either physisorption or chemisorption. In this regard, the E values obtained in case of cobalt and strontium adsorption are in the energy range of an ion- exchange reaction i.e., 8-16 kJ/mol [Helferich, (1962)]. But the value of lead sorption free energy indicated that lead is adsorbsed by physisorption i.e., (20-40 kJ/mol).

Table (III.14): D-R parameters of lead, cobalt and strontiun adsorption R2 2 2 Metal Ions qm(mg/g) B (mol /kj ) E(kJ/mol) Correlation coefficient

Pb2+ 107.392 0.00097 22.62 0.971

Co2+ 102.602 0.00443 10.62 0.989

Sr2+ 75.897 0.00302 12.86 0.990

The values of correlation coefficients ( R2 )of D-R equation are fairly good for the adsorption of lead (0.971), cobalt (0.989) and strontium (0.990); i.e., each metal adsorption obeys D-R equation.

133 Chapter III Results and Discussion

III A.2.4.1. Effect of isotherm shape.

The effect of isotherm shape has been considered to predict if an adsorption system is favorable or unfavorable. In this concern, the features of the Langmuir isotherm can be expressed in trems of a dimensionless constant separating factor or equilibrium parameter ‘r’ which is defined by the following relationship given by Hall et al., (1966)

r = 1 …………………………….(III.13) 1+ bC0

Where C0 is the initial concentration of solute (mg/l), b is the Langmuir adsorption constant (l/mg). The parameter indicates the shape of isotherm as shown in Table (III.15):

Table (III.15): Effect of isotherm shape. Value of r Type of isotherm r > 1 Unfavorable r = 1 Linear 0< r < 1 Favorable r = 0 Irreversible

As shown from Table (III.12) the values of r for

BC-SDS-2105:Pb; BS-S-2750:Co and BC-N2-2500:Sr more than zero and less than one indicating that the adsorption of lead, cobalt and strontium by investigated carbons are favorable.

134 Chapter III Results and Discussion

III A.2.5 Effect of solution pH on metal adsorption

Solution pH is the primary variable governing metal adsorption by all hydrous solids (activated cabon, metal oxides, clays, bone chars, ect.). The metal removal versus pH curve is referred to in the literature as a “ pH- adsorption range”.

Specifically, the pH affects the status of the outer hydration sheaths of the metal ion, aqueous metal speciation, complexation and solubility and the electrochemical behavior of the carbon surface. Netzer and Hughes, (1984) reported that onset of cationic metal adsorption coincided with the loss of the outer hydration sheath of metal ion. The outer hydration sheath is removed at a pH slightly lower than the pH at which

Me(OH)(aq) forms.

The solution pH as a variable was conducted to determine the lowest pH range for maximum metal adsorption by each adsorbent used . In this concern, the adsorption edge for Pb(II) was found in the pH range 2 - 5 as shown in Fig. III.21(a). The values of adsorption edge were found in the pH ranges of 2 - 6 and 2-8 for Co (II) and Sr(II) as shown in Figs. III.21(b) and (c), respectively.

135 Chapter III Results and Discussion

130

120 (a) lead

110

100

90

80 (mg/g) e

q 70

60

50

40

2 3 4 5 6 7 8 9 pH

110 (b) cobalt 100

90

80

70

(mg/g) 60 e q 50

40

30

20 1 2 3 4 5 6 7 8 9 10 11 pH

Fig (III.21): Effect of pH on the adsorption of (a) lead (b)cobalt and (c)strontium.

136 Chapter III Results and Discussion

200 (c) strontium 180

160

140

120

100 (mg/g) e q 80

60

40

20

234567891011 pH

Fig (III.21): Continoud

137 Chapter III Results and Discussion

At pH values below 2 the adsorption of lead, cobalt and strontium were negligible. With the increase of pH from 2 to 4, the adsorption of Pb(II), Co(II) and Sr(II) increased considerably; this result might be explained by the changes in the carbon surface charge at different pH values. At pH values lower than 2 the electrostatic repulsion between the positively charged surface and the metal ions prevents their adsorption. As the pH is raised the surface charge of the adsorbent changes. At pH = 4 and above, there was a dramatic increase in the extent of metal adsorption. As solution pH is increased from a low value metal adsorption by activated carbon ( at metal concentration of approx. 100 mg/l) began at a pH of approx 2 for lead, cobalt and strontium. As solution pH is increased, the metal hydrolysis and precipitation (at a metal concentration of 100 mg/l) began at a pH of 6 for lead, a pH of 8 for cobalt and a pH of 10 for strontium. As solution pH is increased the onset of adsorption therefore occurs before the beginning of hydrolysis and precipitation for all three metals. This finding that the onset of adsorption occurs at a lower pH than the beginning of hydrolysis agrees with that of James and Healey, (1972) in their experiments with adsorption of cobalt, iron, chromium and calcium on SiO2 and TiO2. the adsorption of hydrolysable metal ions [Huang and Lin. (1981) & Hohl and Stumm, (1976) & Schindler et al.,(1976)] showed that, the amounts of heavy metal adsorption increase from a low value to nearly 100% in a narrow pH range. Therefore “pH-adsorption edge” is specific to the heavy metal and carbon type.

138 Chapter III Results and Discussion

The effect of pH on the adsorption of Pb(II) has been investigated by various investigators using various sorbent types. Wang, (1981) reported an adsorption edge at pH 3 - 7 for Pb (II) on Al2O3 and SiO2. Huang et al., (1977) have also reported an abrupt increase in the adsorption of lead and copper in the pH range 5 - 6. Tran et al., (1999) reported that the pH region over which there was a rapid increase in lead adsorption at an initial concentration of 0.5 m M was found to be (3.5 - 5.5). Corapcioglu and Huang, (1987) reported that the adsorption edge of Pb (II) was between pH 3 - 6, and that was a dominant parameter because it affects the charge distribution of various species and the hydroxyl group distribution at the carbon surface.

III A.2.6 Mechanism of metal ions adsorption.

Understanding the mechanism of metal ions interaction, specifically adsorption, with hydrous solid surface is essential to the control of heavy metals in aquatic system. Many adsorption models have been developed to describe the adsorption characteristics and to predict the adsorption quantity of several systems. In the literature, there are:

(1) The ion exchange model, according to which the free metal ions are adsorbed when surface protons are displaced [Ahrland et al., (1960) & Dugger et al., (1964)].

(2)The Gouy-Chapman-Stern-Grahame model, which accounts for electrostatic and specific chemical reaction as major

139 Chapter III Results and Discussion adsorption energies [Breeuwsma and Lyklema, (1973) & Levine and Smith, (1971) & Graham, (1955)].

(3) The ion- solvent interaction(the James- Healy) model, according to which the adsorption energy includes electrostatic, specific chemical reaction and solvation [James and Healy, (1972)].

(4) The surface complex formation model, according to which the specific chemical adsorption energy plays a role more important than the electrostatic energy. Solvation energy, a negative contributing quantity to the overall adsorption i. e. is not existing. [Schindler, (1981) & Hohl et al., (1980) & Huang and Lin, (1981) & Hohl and Stumm, (1976) & Davis et al., (1978) & Davis and Leckie (1978) & Davis and Leckie (1980)].

Activated carbon can be divided into two general types, namely H- and L-types [Mattson and Mark, (1971)]. Several researchers have proposed that metal removal can be quantitavely predicted based on whether a carbon is L-type (acidic nature) or H-type (basic nature). The more acidic carbon, the lower the pH at which it deprotonates and takes on a negative surface charge (i.e.,lower the pHzpc). A negatively charged surface favors cation removal. The opposite behavior occurs for H-type carbons, deprotonation occurs at alkaline pH values, and anions [ e.g.,Cr(VI),Se(IV), etc.] is favored.

140 Chapter III Results and Discussion

III A.2.6.1 Mechanism of lead adsorption on sample BC-SDS-2105

Cationic heavy metals including Pb(II) are removed from aqueous solution due to their interaction with anionic functional groups on the surface of activated carbon [ Yin et al., (2007) & Hong et al., (2008)]. Thus, the surface charge of the activated carbon significantly influences its interaction with Pb (II) ions, and this charge varies according to the solution pH [ Moreno- Castilla et al., (2004) & Nadeem et al., (2006) & Boehm, (1966)].

Other researchers reported that the surface charge of the activated carbons impregnated with other anionic surfactants (i.e. linear alkyl benzene sulfonate) were negative at all pHs tested because the hydrophilic negatively charged head groups of the surfactants are arranged toward the aqueous phase [Baúar et al., (2003)]. These results suggest why BC-SDS-2105 can effectively remove Pb(II) even at pH = 2. As pH is raised, the surface charge of activated carbon is negative, so Pb (II) ions, which are positively charged, can easily bind to negatively dissociated forms of the surfactant,s active groups and can undergo complex formation with its surface groups, as indicated in Eq.(III.14) [ Rangel-Mendez and Streat, (2002) ].

2+ + 2 ROH + M « (RO ) 2 M + 2 H ……….(III.14)

Because of activated carbon is highly hydrophobic, exterior molecules with hydrophobic groups can be strongly

141 Chapter III Results and Discussion bound to its surface by van der Waals interaction and then can influence the characteristics of the activated carbon,s surface. In anionic surfactants a long (hydrophobic) alkyl chain binds to the surface of the activated carbon, while its negatively charged (hydrophilic) head group is arranged toward the surrounding water.

As a result, the hydrophilic part(s) of the surfactant contribute a large quantity of anionic functional groups to the activated carbon Eq.(III.15)

2+ + 2RSO3 Na + M « (RSO3 ) 2 M + 2Na …………(III.15)

Eq.(III.15) indicates that Pb (II) ions can easily approach and bind to the negatively charged group(s) of the anionic surfactant that is bound to the surface of activated carbon. In addition, the Pb (II) ions can bind to the other active groups which were originally present on the surface.

Another possible reaction is a competitive or inhibition mechanism between Pb2+ and H+ion Eq.(III.16)

+ + RSO3 Na + H « RSO3 H + Na ………………(III.16)

142 Chapter III Results and Discussion

III A.2.6.2 Mechanism of cobalt and strontium sorption

Physical activation of bone char by steam and nitrogen as activating agents in samples BC-S-2750 and BC-N2- 2500, respectively, results in H-type activated carbons i.e (basic nature), this means that a positive surface charge over a wide pH-range is available on the activated carbon surface. It is interesting to understand the mechanism that governs the adsorption process in these very particular systems where positive carbons remove positive cations. It seems that some non- electrostatic forces called “ specific adsorption ” were involved in the process of adsorption [Namasivayam and Ranganathan, (1995)]. The significant amount of the metal removal observed, might be attributed mainly to the electron donating acceptor (EDA) complexation between the de-localized ʌ-electron of graphen layers and Co2+ and Sr2+ by dispersive forces [Metaxas et al., (2003)]. Similar observations were reported by Namasivayam and Ranganathan, (1995) for adsorption of Cd (II) onto “waste” Fe(III)/Cr(III) hydroxide and by Galiatsatou et al., (2002) for adsorption of zinc onto H-type carbon. The same trend of Cd (II) adsorption was reported by Chi K.Ahn et al., (2009) for adsorption of cadmium onto surfactant-impregnated activated carbons.

Another explanation for this observation, is that the positively charged Co2+ and Sr2+ species present in the solution may exchange with H+ from –COOH groups of the carbons Eq.(III.17).

143 Chapter III Results and Discussion

- + 2 + + 2R - COO H + M « (R - COO)2 M + 2H ……………..(III.17)

Generally, sorption studies of cobalt (II) and strontium

(II) onto samples BC-S-2750 and BC-N2-2500, respectively, indicated that adsorbed species result from both ion exchange and electron donating acceptor complexation reactions at the edge sites.

III A.2.7 Thermodynamic evaluation of the adsorption process.

III A.2.7.1 Effect of temperature.

The effect of increasing temperature on the uptake of lead, cobalt, and strontium from 35 0C to 55 0C was investigated. The experimental results are given in Figs.(3.22, 3.23 and 3.24). The data indicated that the magnitude of adsorption is proportional to the solution temperature in the 3- cases of Pb 2+, Co 2+ and Sr2+ adsorption.

It was found that, according to the adsorption isotherm, the amounts of lead, cobalt and strontium adsorbed increase with increasing the solution temperature. The Langmuir parameters for the adsorption isotherms obtained at different temperatures were calculated from the Ce/qe versus Ce plots (Figs. III.25, III.26 and III.27). The results are given in Table(III.16); it was clear that the value of the monolayer coverage (q0) for lead, cobalt and strontium increases with the increase of temperature.

144 Chapter III Results and Discussion

The increase of lead, cobalt and strontium capacity with respect to temperature is a direct consequence of; (i) enlargement of pore size or activation of the adsorbent surface or creation of some new active sites on the adsorbent surface [Namasivayam and Ranganathan, (1995) & Weber et al., (1963 )], (ii) rapid kinetic at higher temperature due to enhanced mobility of lead, cobalt and strontium ions from the bulk solution towards the adsorbent surface and extent of penetration within the adsorbent structure [Agrawal et al., (2004) & Khalid et al., (2000)] and (iii) overcoming the activation energy barrier and accelerating the rate of external mass transfer and intra-particle diffusion giving the short time span of the kinetic experiments [Shukla et al., (2002) & Weber et al., (1963 )]. Table (III.16): Langmuir parameters for lead, cobalt and strontium adsorption at different temperatures.

Metal ion Temperature q0 b R2 (0C) (mg/g) (l/g)

Pb2+ 35 128.53 0.107 0.999 45 233.10 0.089 0.998 55 400 0.047 0.991

Co2+ 35 109.52 0.124 0.996 45 143.47 0.077 0.996 55 186.21 0.0344 0.990

35 87.26 0.0779 0.994 Sr2+ 45 129.53 0.083 0.982 55 140.84 0.236 0.994

145 Chapter III Results and Discussion

400

0 360 35 C 0 320 45 C 55 0C 280

240

200 (mg/g)

e 160 q

120

80

40

0 0 20 40 60 80 100

C e(mg/l)

Fig. (III.22): The effect of temperature on lead sorption

160 35 0C 140 45 0C 120 55 0C

100

80 (mg/g) e

q 60

40

20

0 0 20 40 60 80 100 120 140

C e( mg/l) Fig.(III.23): The effect of temperature on Cobalt sorption. Fig. (III.23): The effect of temperature on Cobalt sorption

146 Chapter III Results and Discussion

140 130 120 110 100 90 80 70 (mg/g)

e 60 0 q 50 35 C 0 40 45 C 30 55 0C 20 10 0 0 20 40 60 80 100

Ce(mg/l)

Fig. (III.24): The effect of temperature on strontium sorption

1.2 0 1.1 35 C 1.0 45 0C 0.9 55 0C 0.8

e 0.7 /q e

C 0.6

0.5

0.4

0.3

0.2

0.1

0.0 20 40 60 80 100 Ce(mg/l) Fig. (III.25): Langmuir plots of lead adsorption showing the effect of temperature

147 Chapter III Results and Discussion

1.4 35 0C 1.2 45 0C 0 1.0 55 C

0.8 e /q e

C 0.6

0.4

0.2

0.0 0 20 40 60 80 100 120 140

Ce(mg/l)

Fig. (III.26): Langmuir plots of cobalt adsorption showing the effect of temperature.

1.4

35 0C 1.2 45 0C 0 1.0 55 C

0.8 e /q e

C 0.6

0.4

0.2

0.0 0 20 40 60 80 100 Ce(mg/l)

Fig. (III.27): Langmuir plots of strontium adsorption showing the effect of temperature.

148 Chapter III Results and Discussion

III A.2.7.2. Thermodynamic parameters.

Thermodynamic parameters such as free energy change ¨G0), enthalpy change (¨H0) and entropy change(¨S0) were determined using the following equations [Singh et al.,(1988) & Catena and Bright, (1989) & Fraiji et al., (1992)]

CAe Kc = ……………………………(III.18) Ce

Where Kc is the equilibrium constant and CAeand Ceare the equilibrium concentration (mg/l) of the metal ion on the adsorbent and in the solution, respectively.

0 (¨G ) = RT ln Kc .…………………………(III.19) where T is temperature in Kelvin and R is the gas constant ( 8.314 J.mol-1.k-1 )

DS 0 DH 0 log Kc = - ………………….(III. 20) 2.303R 2.303RT

¨H0 and ¨S0 were obtained from the slope and intercept ’ of van t Hoff plots of log Kc vs. 1/T Fig. (III.28). The calculated 0 0 0 values of Kc , ¨H , ¨S and (¨G ) at different temperatures are presented in Table (III.17).

149 Chapter III Results and Discussion

0.5 Lead 0.4 Cobalt Strontium 0.3

0.2 c 0.1 log K 0.0

-0.1

-0.2

-0.3 3.05 3.10 3.15 3.20 3.25 1/Tx10-3

Fig. (III.28): Van't Hoff plots of lead, cobalt and strontium adsorption

Table(III.17): Thermodynamic parameters of lead, cobalt and strontium adsorption.

¨G0 ¨H0 ¨S0 Metal ion Temperature K c (kJ/mol) kJ/mol J/mol.k 308 K 1.037 -0.093 318K 1.178 -0.433 7.275 24.01 Lead 328 K 1.232 -0.568

308 K 0.544 1.556 Cobalt 318K 0.731 0.827 23.589 71.552 328 K 0.954 0.128

308 K 1.141 -0.337 Strontium 318K 1.504 -1.078 19.564 64.698 328 K 1.816 -1.627

150 Chapter III Results and Discussion

The equilibrium constant (Kc) values are higher than unity for both lead and strontium i.e., lead and strontium have a higher preference for their sorbent surfaces [Bansal et al.,

(1981)] than cobalt which has Kc value less than unity. The transition of metal uptakes from physical adsorption ( at lower tempretures) to chemical adsorption (at higher tempreture) is indicated by an increase in Kc with rise in temperature. This is confirmed by the positive values of enthalpy change (¨H0). The values of (¨G0) listed in Table (III.17) are negative for both lead and strontium, this suggests that the adsorption process of lead and strontium is spontaneous with a high preference of samples BC-SDS-2105 and BC-N2-2500 for Pb and Sr, respectively.The positive value of (¨G0) in case of cobalt adsorption at all temperatures studied indicates the formation thermodynamically unstable adsorbed species [Alama et al., (2005)].

The positive values of entropy change (¨S0) in lead, cobalt and strontium adsorption show the increased randomness at the solid/solution interface during the adsorption of metal ions onto investigated carbons [Namasivayam and Ranganathan, (1995 )] which suggests that metal ions replace some water molecules from the solution prior to the adsorption on the surface of carbons. These displaced molecules gain more translation entropy than is lost by the absorbate ions resulted in the creation of steric hindrance, thus allowing the prevalence of randomness in the system [Namasivayam and Ranganathan, (1995) & Romero- Gonzalez et al., (2006 )].

151 Chapter III Results and Discussion

III A.2.8 Effect of carbon mass on metal ions adsorption.

Fig. (III.29) shows the effect of carbon dosage on Pb (II),Co(II) and Sr(II) adsorption. The figure shows that the percent of removal of metal ions increased with an increase in carbon mass and attained complete removal after a particular carbon concentration for each metal ion under investigation. This is due to the availability of more surface functional groups at higher carbon concentrations.

120

100

80

60 Lead

% Removal 40 Cobalt Strontium

20

0 0.00 0.02 0.04 0.06 0.08 0.10 Carbon mass (gm.) Fig.(III.29): Effect of carbon mass on lead,cobalt and strontium sorption. Fig. (III.29): Effect of carbon mass on lead, cobalt and strontium sorption

152 Chapter III Results and Discussion

III A.3 Acid Red 73 and Acid Blue 74 Removal.

Dyes have long been used in dying, paper, pulp, textile, plastics, leather, cosmetics and food industries [Gulnaz et al.,(2004)]. Colour stuff discharge from these industries causes certain hazards and environmental problems. These coloured compounds are not only aesthetically displeasing but also inhibiting sunlight penetration into the stream and affecting aquatic ecosystem [Tsai et al., (2001)]. Dyes usually have complex aromatic molecular structures which make them more stable and difficult to biodegrade [Blanca et al., 2006)]. Furthermore, many dyes are toxic to microorganisms and may cause direct destruction or inhibition of their catalytic capabilities [ Santhy and Selvapathy ,( 2006)].

There are various conventional methods of removing dyes including coagulation and flocculation [órfão et al., (2006)], oxidation or ozonation [Malik and Saha, (2003)] and membrane separation [Ciardelli et al., (2001) ]. However, these methods are not widely used due to their high cost and economic disadvantage. Chemical and electrochemical oxidations, coagulation are generally not feasible on large scale industries. In contrast, an adsorption technique is by far the most versatile and widely used. The most common adsorbent materials are: alumina and silica [Josefa and De Oliveira, (2003)], metal hydroxides [Feng-Chin Wu and Ru-Ling Tseng, (2006)] and activated carbon [ Malik et al., (2002)].

153 Chapter III Results and Discussion

The largest class of dyes used at present is referred to as acid dyes, which are anionic compounds mainly used for dyeing nitrogen containing fabrics like wool, polyamine and silk. Out of 12 classes of different chromogenic groups of dyes, a most common group is azo group, which contributes up to 70% of all textile dyes produced, followed by anthraquinone group [Vandevivere et al., (1998)]. Azo dyes, characterized by their typical azo bond (R1-N=N-R2), which is responsible for colour, are a more popular dye group used in the textile industry and due to their poor exhaustion properties, as much as 30% of initial dye applied remain unfixed and end up in effluents [Manu and Sanjeev, (2003)]. Anthraquinone dye chromophore is characterized by its carbonyl group, and it may be present once or repeated times. The colour of anthraquinone dyes is partially associated with the anthraquinone nucleus and is modified by the type, number and position of the substitutes.

In this concern, this section deals with the adsorption of acid dyes using activated carbon derived from bone char. According to the preliminary test, table (2.2), sample BC-SDS-2105 was chosen for the removal of acid dyes (acid red 73 and acid blue 74). Their structural formulae and colour index (C.I) are described in Figs. (III.30) and (III.31).

154 Chapter III Results and Discussion

Figure ( III.30): Structure of (acid red 73) C.I 27290 Mol.wt 556.48 4-phenylazophenyleazo)- 1,3-naphthalenedisulfonic acid disodiumsalt

Figure (III.31): Structure of (acid blue 74) C.I 73015 Mol.wt 466.35 Disodium5,5,-(2-(1,3-dihydro-3-0x0-2H- indazol-2-ylidene)-1,2dihydro-3H-indol-3- one)disulphonate

155 Chapter III Results and Discussion

III A.3.1 Kinetic studies of acid red 73 and acid blue 74 adsorption. III A.3.1.1 Effect of agitation time.

The kinetic investigations on the adsorption of acid red 73 and acid blue 74 using BC-SDS-2105 sample are given in Fig.(III.32). As agitation time increases, the dye removal also increases initially, but then gradually approaches a constant value, thus denoting the attainment of an equilibrium. Obviously, the equilibrium was attained after shaking for about 48 hr, beyond which there is no further increase in the adsorption.

The curves shown in Fig.(III.32), present a double nature, the removal of each dye is high in the initial time, but thereafter the rate significantly levels off and eventually zero, i.e. equilibrium is attained. These changes in the rate of removal may be due to the fact that, initially adsorption sites were vacant and the solute concentration gradient was high. Afterwards, the dye uptake rate by the adsorbent decreases significantly, due to decrease in adsorption sites. In other words, adsorbed dyes firstly occupy highest-energy sites at low surface coverage. As the high-energy sites become saturated, dyes progressively occupy lower-energy sites, resulting in the decrease of the average binding energy on the surface. Acid red 73 adsorption takes place with high degree on the sorbent surface. This is supported on the shape of acid red 73 curve in Fig.(III.32)

156 Chapter III Results and Discussion

26 acid red 73 24 acid blue 74 22 20 18 16 14

(mg/g) 12 e q 10 8 6 4 2 0 0 10 20 30 40 50 60 70 80 Time(hr.)

Fig. (III.32): Influence of agitation time on adsorption of acid red 73 and acid blue 74.

Sorption processes of this type of dyes are considered to comprise three step [Mckay et al., (1998)]: (i) external or film diffusion across the boundary layer surrounding the particle, (ii) intraparticle mass transfer within the adsorbent particle boundary by homogeneous surface diffusion or pore diffusion, (iii) sorption or attachment of the solute molecule at a surface site. External film diffusion is frequently cited as an important criterion in the rate-controlling process.

However, the intraparticle diffusion processes often have a much greater influence on the time for adsorbent to reach equilibrium, i. e. full saturation capacity, particularly for large molecules such as dyestuff.

157 Chapter III Results and Discussion

III A.3.1.2 Kinetic rate parameters.

The kinetic experimental data obtained for acid red 73 and acid blue 74 on BC-SDS-2105 sorbent is simulated by pseudo- first-order and the second-order rate equations. The results are shown in Fig.(III.33 ) and (III.34). Obviously, the kinetic data of the dyes can be described well by second-order rate equation due to the high values of correlation coefficient R2 for second- order adsorption model compared to that of pseudo-first-order model. The calculated equilibrium adsorption capacities qe,cal derived from second-order model agree well with the experimental values. These results suggest that the sorption system is not first-order reaction and that the second-order model is more favourable, based on the assumption that the rate-limiting step may be chemical sorption involving valency forces through sharing or exchange of electrons between dyes and adsorbent [Aksu and Tezer, (2000) & Chiou et al., (2004) & Gücek et al., (2005)].

158 Chapter III Results and Discussion

Table (III.18): Comparison of the pseudo-first-order and second-order adsorption rate constants and the calculated and experimental qe values for acid red and acid blue dyes.

Model Parameter Acid red 73 Acid blue 74

Eperimental qe,exp(mg/g) 25.122 16.719

Pseudo-first-order model K1 (min-1) 8.983 8.914

qe,cal(mg/g) 13.359 9.460

R2 0.981 0.9709

K2(g/mg min) 0.00025 0.000306 Second-order model h(mg/g min) 0.165 0.0912

qe,cal(mg/g) 25.621 17.241

R2 0.998 0.999

The initial adsorption rate (h) determined by the second- order rate equation are listed in Table (III.18). The values of second-order initial adsorption rate constant for acid red 73 and acid blue 74 are 0.165 and 0.0912; respectively. These results confirm the data obtained by maximum adsorption capacity from equilibrium time curves.

Furthermore in most cases the pseudo-first-order equation of Lagergren does not fit well for the whole range of contact time and is generally applicable over the initial time of the sorption process. The second-order equation is also based on the sorption capacity of the solid phase. Contrary to the other model, it predicts the behaviour over the whole range of adsorption and it is in agreement with an adsorption mechanism being the rate controlling step [Aksu and Tezer, (2000)].

159 Chapter III Results and Discussion

2.0

1.8 acid red 73 acid blue 74 1.6

1.4

1.2

) 1.0 t -q e 0.8

0.6 log(q

0.4

0.2

0.0

-0.2

0 500 1000 1500 2000 2500 3000 Time( min.) Fig.(III.33): Pseudo-first-order sorption kinetics of acid red 73 and acid blue74. Fig. (III.33): Pseudo-first-order sorption kinetics of acid red 73 and acid blue 74.

280 260 acid red 73 240 acid blue 74 220 200 180 160

t 140

t/q 120 100 80 60 40 20 0 0 1000 2000 3000 4000 5000 Time(min.) Fig.(III.34): second-order sorption kinetics of acid red 73 and acid blue 74. Fig. (III.34): Second-roder sorption kinetics of acid red 73 and acid blue 74

160 Chapter III Results and Discussion

III A.3.1.3 Intra-particle diffusion.

From a mechanistic point of view to interpret the experimental data, prediction of the rate-limiting step is an important factor to be considered in the sorption process [Vadivelan and Kumar, (2005)]. In order to show the existence of intra-particle diffusion in the adsorption process, results were subjected to the Weber-Morris (Eq. III.3). In case of a batch process, the adsorbate molecules are often diffuse into the interior of the porous adsorbent and the rate of the process in such case usually depends upon t0.5 rather than time (t) itself. A plot of the quantity of dye adsorbed against square-root of time is shown in Fig.(III.35). It can be observed that the plots are not linear over the whole time range and the graphs of this figure reflect a dual nature, with initial linear portion followed by plateau.

acid red 73 25 acid blue 74

20

15 (mg/g) e

q 10

5

0 0 10203040506070 Time0.5(min.0.5) Fig.(III.35): Intra-particle diffusion plots for acid red 73 and acid blue 74 sorption. Fig. (III.35): Intra-particle diffusion plots for acid red 73 and acid blue 74 sorption.

161 Chapter III Results and Discussion

This implies that the external surface adsorption (stage 1) is absent and the stage of intra-particle diffusion (stage 2) is attained and continued to 240 min. Finally, equilibrium adsorption (stage 3) starts after 240 min. The dyes are slowly transported via intra- particle diffusion into the particles and is finally retained in the pores. Similar duel nature of intra-particle diffusion curve with initial linear portion was found by Cox et al., (2005) for sorption of precious metals onto activated carbon

The rate constants of intra-particle diffusion were obtained from the slopes of the straight lines and were found to be 1.044 and 1.005 mg g-1hr.0.5 for acid red 73 and acid blue 74 with correlation coefficients of 0.999 and 0.995 for acid red 73 and acid blue 74, respectively. However, the linear portion of the curves do not pass the origin Fig. (III.35) i.e. the pore diffusion is not the only rate controlling step [Cox et al., (2005)]. This indicates that other factors started to play an important role in controlling the adsorption. Since most of the adsorption sites on the carbon surface were occupied by previously adsorbed dyes the dyes molecule that were subsequently transported to the surface of the carbon had to find available adsorption sites before the attachment can occur. The adsorption of dyes on the sample BC-SDS-2105 in the later stage hence slowed down and would probably transit from the initial diffusion- controlled process (intra-particle) to a final attachment-controlled process (equilibrium). As shown in Fig.(III.35), the latter stage of dyes adsorption doesn’t obey Weber-Morris equation. This results were confirmed by Boyed plots Fig. (III.36) where straight lines don’t pass through the origin point.

162 Chapter III Results and Discussion

1.0 acid red 73 0.5 acid blue 74 0.0

-0.5

-1.0

t -1.5 B -2.0

-2.5

-3.0

-3.5

-4.0 0 500 1000 1500 2000 2500 3000 Time(min.) Fig.(III.36): Boyd plots of the kinetics for acid red 73 and acid blue 74 sorption.

Fig. (III.36): Body plots of the kinetics of acid red 73 and acid blue 74 sorption.

III A.3.2 Effect of adsorbent mass

Fig. (III.37) shows that as the carbon mass increased the percent of removal (% R) increases but the adsorption capacity

(qe) decreases. There are many factors, which can contribute to this adsorbent mass effect, the first factor is that as the mass of adsorbent is increases, the number of available adsorption sites increases which are able to adsorb more dyes thus resulting in an overall increase in the percent of removal (%R ) [Sharma and Forster, (1993)], but the adsorption sites remain unsaturated during the adsorption process leading to drop in adsorption capacity (qe). The second cause may be aggregation/ agglomeration of sorbent particles at higher concentration of adsorbent mass, which would 163 Chapter III Results and Discussion lead to a decrease in the surface area available for dyes adsorption and an increase in the diffusional path length [Belmouden et al., (2000)]. Some authers, attributed the effect of adsorbent concentration to the kinetic limitation, the time-scale for an adsorption equilibrium to be reached in diffusion mode is solid concentration dependent. They attribute the sorbent concentration effect to the non-attainment of equilibrium [Belmouden et al., (2000)]. The particle interaction at higher adsorbent concentration may also help to desorb some of the loosely bound dyes from the sorbent surface [Özacar and Sengil, (2005)].

26 110

24 100

22 % R AR 73 q AR 73 90 20 e 80 18 % R AB 74 70 16 q AB 74 14 e 60

12 50 (mg/g) % R e

q 10 40 8 30 6 20 4 2 10 0 0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 Carbon mass(mg)

Fig. (III.37): Effect of carbon mass uptake and % of removal on acid red 73 and acid blue 74 sorption.

164 Chapter III Results and Discussion

III A.3.3 Effect of adsorbate concentration.

The effect of acid red 73 and acid blue 74 concentration on the adsorption process was studied. Fig (III.38) shows that, as acid red 73 and acid blue 74 concentration increases, the adsorbed amount of acid red 73 and acid blue 74 also increases. Increasing the initial concentration provides an important driving force to overcome all mass transfer resistance of acid red 73 and acid blue 74 between the aqueous and solid phase and accelerates the diffusion of dyes from solution onto adsorbents [Montanher et al., (2005)] and this would result in higher adsorption. However, the increase in acid red 73 and acid blue 74 concentration beyond about 150 mg/l causes little increase in the amount of acid red 73 and acid blue 74 adsorbed indicating that the adsorption sites are saturated. At different acid red 73 and acid blue 74 concentrations for a fixed adsorbent mass, the surface sites are fully exposed. With increasing concentration there is an increase in adsorption capacity up to a certain value, which may be due to a high intramolecular competitiveness to occupy the lower energetic surface sites left behind. After saturation point the process becomes purely reversible and there will be no adsorption [Das et al., (2003)]. These results may be explained considering that, at low adsorbate concentration, the ratio of surface active sites to total dye concentration is high, hence the dyes could interact with the sorbent to occupy the active sites on the carbon surface sufficiently and be removed from the solution [Montanher et al., (2005)]. But with the increase in adsorbate concentration, the number of active adsorption sites is not enough to accommodate dyes.

165 Chapter III Results and Discussion

40 acid red 73 35 acid blue 74

30

25

(mg/g) 20 e q

15

10

5 0 20 40 60 80 100 120 140 160 180 200 220 C0(mg/l) Fig.(III.38): Influence of initial concentration on the equilibrium uptake(q ) Fig. (III.38): Influence of initial concentration on the equilibrium uptake (qe) of acid red 73 and acid blue 74 using sample BC-SDS-2105

III A.3.4 Effect of solution pH.

Beside the many other factors which affect the extent of adsorption, the fraction of colored ions in the commercial salts, the molecular volume of dye and its planarity, the chelating ability of the adsorbent-dye system and the dimerization ability of the dye act may affect on the adsorption [Mckay et al., (1982)]. The pH of the aqueous solution is an important variable which controls the adsorption at water-adsorbent interfaces. Therefore, the adsorption of acid red 73 and acid blue 74 on sample BC-SDS-2105 were examined at different pH-values ranging from 2.5 to 12 and the results are presented

166 Chapter III Results and Discussion in Fig.(III.39). It can be seen that the adsorption of acid red 73 and acid blue 74 on sample BC-SDS-2105 is strongly pH dependent. In general, the uptakes are much higher in acidic solution than those in neutral and alkaline conditions. Similar results of pH effect were also reported for the adsorption of Congo Red onto activated carbon [Namasivayam and Kavitha, (2002)], adsorption of aromatic acids on activated carbons [Ward and Getzen, (1970)], the adsorption of acid dye on cross-linked chitosan fibers [Yoshida et al., (1993)] and the adsorption of RD 189 (reactive dye) on cross-linked chitosan beads [Chiou and Li, (2003)].

A possible explanation of pH effect on acid red 73 and acid blue 74 adsorption is the change of surface charge of the adsorbent. According to Yoshida et al., (1993) and Kumar, (2000), at lower pH more protons will be available to protonate the surface of adsorbent, thereby increasing the electrostatic attractions between positively charged adsorption sites and negatively charged dye anions and causing an increase in dye adsorption. This explanation agrees with our data on pH effect. This means that the increase of adsorption with decreasing pH was due to increasing positive charge on the adsorbent and vice versa.

167 Chapter III Results and Discussion

38 36 acid red 73 34 acid blue 74 32 30 28 26 24

(mg/g) 22 e q 20 18 16 14 12 10 2 4 6 8 10 12 pH

Fig. (III.39): Effect of pH on the sorption of acid red 73 and acid blue 74 dyes by sample BS-SDS-2105

III A.3.5 Mechanism of acid red 73 and acid blue 74 adsorption.

The bone char analysis indicates that it consists of calcium phosphate as a major component [Juan et al., (2010)]. Consequently, the ash content of sample BC-SDS-2105was 77.29 % as described in Table (III.8) and it has the highest C/H ratio (14.06) among the prepared carbons i.e. the ability for organic adsorption increases and this is confirmed by methylene blue test Table (III.6). So the possible mechanisms of the adsorption process of acid dyes on sample BC-SDS-2105 are likely to be ionic interactions of the colored dye ions with the phosphate

168 Chapter III Results and Discussion groups on bone char. In aqueous solution, the acid dye is first dissolved and the sulfonate groups of acid dye (D-SO3-Na) dissociate and are converted to anionic dye ions.

- + D-SO3Na + H2O ĺ D-SO3 + Na ………....(III.21)

Also, in the presence of H+, the phosphate groups of bone char became protonated [Juan et al., (2010)].

ŁPO- + H+ ĺŁPOH …….……(III.22)

+ ŁCaOH2 ĺ ŁCaOH + H ….………(III.23)

The adsorption process proceeds due to the electrostatic attraction between these two counter ions.

- ŁPOH + D-SO3 ļŁPOH …..O3S-D …………(III.24)

- ŁCaOH + D-SO3 ļ ŁCaOH…. O3S-D ………..(III.25)

Therefore, the difference in the degree of adsorption may be mainly attributed to the chemical structure of each dye.

III A.3.6 Equilibrium adsorption isotherms.

Adsorption equilibria provide fundamental physicochemical data for evaluating the applicability of the sorption process as a unit operation [Vadivelan and Kumar, (2005)] .

To investigate the adsorption of acid red 73 and acid blue 74, the adsorption equilibrium isotherms of the two dyes on

169 Chapter III Results and Discussion

BC-SDS-2105 are given in Fig.(III.40). All the isotherms show that, the adsorption capacity increases with increasing equilibrium concentration of dyes in the first portion of the isotherm, and the increasing slopes became slow at higher equilibrium concentrations until the curves reached a plateau.

The isotherms have been classified according to Giles classification [ Giles et al., (1960)]. Giles classified adsorption isotherms into four main groups: (i) S curves, indicative of vertical orientation of adsorbed molecules at the surface, (ii) L curves, the normal or “Langmuir” isotherms, usually indicative of molecules adsorbed flat on the surface, or sometimes, of vertically oriented adsorbed ions with particularly strong intermolecular attraction, (iii) H curves, “High affinity” (commencing ionic micelles) and by high-affinity ions exchanging with low-affinity ions and (iv) C curves, “Constant partition”, linear curves, given solutes which penetrate into the solid more readily than does the solvent.

170 Chapter III Results and Discussion

40 acid red 73 35 acid blue 74

30

25

20 mg/g) e q 15

10

5

0 20 40 60 80 100 120 140 160 180 200

C e(mg/l) Fig.(III.40): Equilibrium adsorption isotherms of acid red 73 Fig. (III.40): Equilibrium adsorption isotherms of acid red 73 and acid blue 74 onto sample BC-SDS-2105.

According to Giles classification Giles et al., (1960) of isotherms, acid red 73 and acid blue 74 show an L-type isotherms with steep initial portions and a plateau starting at relatively low concentration, the plateau covers a wide range of solution concentrations. This indicates that acid red 73 and acid blue 74 dyes are strongly sorbed on the BC-SDS-2105 sorbent. Also, the results show that acid red 73 exhibits stronger adsorption than acid blue 74.

III A.3.6.1 Isotherm modeling.

Adsorption isotherms describe how adsorbates interact with adsorbents and are critical in optimizing the use of adsorbents. To optimize the design of a sorption system to remove dyes from effluents, it is important to establish the most appropriate

171 Chapter III Results and Discussion correlation for the equilibrium curves. The experimental data of equilibrium isotherms for the two dyes onto BC-SDS-2105 were modeled using the most frequently used isotherms: Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms [Dubinin and Radushkevich, (1947)]. The parameters of all three models can be obtained from slopes and intercepts of equations (III.7, III.8 and III.12). The isotherm parameters are given in Table (III.19). The applicability of the isotherm equation is compared by judging the non-linear correlation coefficients R2. In a view of value of non-linear R2, Langmuir isotherm gives good fit (R2 > 99) for the two dyes.

Table (III.19): Langmuir, Freundlich, and Dubinin- Radushkevich parameters for adsorption of acid red 73 and acid blue 74 onto BC-SDS-2105 sample at 25 0C

Model Parameter Acid Red 73 Acid Blue 74

q0(mg/g) 35.112 18.467 Langmuir b (l/mg) 0.192 0.127 R2 0.999 0.997

K ( mg/g) 13.782 5.846 1/n 0.193 0.246 Freundlich n 5.163 4.065 R2 0.973 0.993

qm (mg/g) 34.105 16.576 B (mol2/kJ2) 0.357x10-4 0.425x10-4 Dubinin-Radushkevich E (kJ/mol) 118.34 108.35 R2 0.984 0.936

172 Chapter III Results and Discussion

(A) Langmuir Model:

From Table (III.19), it is clear that the adsorptive capacity (q0) of BC-SDS-2105 toward acid red 73 is higher than that toward acid blue 74. This result was confirmed by the value of b (adsorption affinity) for acid red 73, which is higher than that of acid blue 74. Fig.(III.41) shows linear relationship of Ce against Ce/qe indicating the applicability of Langmuir model.

(B) Freundlich Model:

Fig. (III.42) shows satisfactory linear relationship of log Ce against log qe indicating also the applicability of the Freundlich model. Accordingly, Freundlich isotherm parameters (K, n) for acid red 73 and acid blue 74 are summarized in Table (III.19). The constant K represents the capacity of BC-SDS-2105 for the solute while the constant n represents the strength of the adsorption of the solute by adsorbent. Together, K and n determined the shape of the isotherm.

In general, an isotherm shows that one component adsorbs more than another if it has a higher value of K at the same equilibrium concentration, if its data have a lower slope, and if its equilibrium points extend to a lower value of equilibrium concentration. In our study, this rule is applicable for acid red 73 which have higher K and lower slope than that of acid blue 74. From Table (III.19), the values of 1/n were found in the range 0.1 to 0.5, indicating that: (a) the adsorption

173 Chapter III Results and Discussion capabilities of acid red 73 and acid blue 74 towards BC-SDS- 2105 increased as the temperature increased [Milonjic et al., (1992)] and (b) surface structure of sorbent BC-SDS-2105 is heterogenous [IUPAC,(1994)]. The values of the Freundlich exponent “n” are greater than one, indicating that the adsorption of acid red 73 and acid blue 74 by carbon BC-SDS-2105 is favorable. However, it is further clear that adsorption of acid red 73 is more favorable than that of the acid blue 74 as indicated by higher K and n values, and higher capacity at the same equilibrium concentration.

8

acid red 73 7 acid blue 74

6

5

e 4 /q e C 3

2

1

0 0 20 40 60 80 100 120 140 160

C e(mg/l) Fig. (III.41): Langmuir plots of acid red 73 and acid blue 74 adsorption

174 Chapter III Results and Discussion

2.4 acid red 73 2.2 acid blue 74

2.0

1.8

1.6

1.4 e

1.2 log q 1.0

0.8

0.6

0.4

0.2

0.0 0.5 1.0 1.5 2.0 2.5

log Ce

Fig. (III.42): Freundlich plots of acid red 73 and acid blue 74 adsorpiton

(C)Dubinin-Radushkevich (D-R) isotherm

It is known that the Langmuir and Freundlich isotherm constants do not give any idea about the adsorption mechanism. In order to understand the adsorption type, equilibrium data was tested with Dubinin-Radushkevich (D-R) isotherm.

2 The plots of ln qe against İ for acid red 73 and acid blue 74 sorption onto BC-SDS-2105 carbon are shown in Fig

(III.42). The D-R parameters qm and B are calculated from the intercept and slope of the lines in Fig. (III.42), respectively. The values of these parameters are given in Table (III.19), The mean free energy of adsorption (E), defined as the free energy change when 1 mole of ion is transferred to the surface of the solid

175 Chapter III Results and Discussion from infinity in solution, [Onyango et al., (2004)] was calculated from B values (Eq. III.11).

The value of correlation coefficient factor ( R2 ) of D-R equation are fairly good for the adsorption of acid red 73 ( R2 > 0.98) only i.e. acid red 73 adsorption obey D-R equation. 0 The qm values calculated from D-R model are less than q calculated from the Langmuir model (Table III.19).

The sorption free energy has been evaluated to get some information of the nature of bonding i.e. either physisorption or chemisorption . In this regard the E values obtained are in the energy range 52.99 - 133.63 kJ/mol i.e. acid red 73 and acid blue 74 are adsorbed by chemisorption.

-2.0 -2.2 acid red 73 -2.4 acid blue 74

-2.6

-2.8

-3.0

-3.2

-3.4 (m.mole/g) e -3.6 ln q -3.8

-4.0

-4.2

-4.4

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 e2x10-4 Fig. (III.43): D-R plots for acid red 73 and acid blue 74 sorption onto sample BC-SDS-2105.

176 Chapter III Results and Discussion

III A.3.7 Thermodynamic Studies.

III A.3.7.1 Temperature effect

The effect of temperature on the adsorption of acid red 73 and acid blue 74 dyes on BC-SDS-2105 carbon was also checked using a series of isotherms which determined at different temperatures (25, 35, 45 and 65 0C) and the results are shown in Figs.(3.44 )and (3.45), respectively.

It was found that, according to the adsorption isotherms, the uptake of acid red 73 decreases only slightly with increasing temperature but the uptake of acid blue 74 increases with increasing temperature.

The isotherms constants that are obtained for the sorption of acid red 73 and acid blue 74 dyes onto BC-SDS-2105 carbon for the three models: Langmuir, Freundlich and Dubinin- Radushkevich at different temperatures are presented in Table (III.20). Based on the correlation coefficient values, R2, generally, Freundlich and Dubinin-Radushkevich isotherms are not good models for the adsorption of acid red 73 and acid blue 74 in this case. Langmuir, isotherm is still found to be good representative for the experimental data over the whole concentration range with high correlation coefficient values i.e., Langmuir isotherm provides a good model for this sorption system. The q0 values calculated from Langmuir model were obtained and were found that q0 deceases only slightly by increasing temperature in case of acid red 73 but in case of acid blue 74 (q0 ) increase by

177 Chapter III Results and Discussion increasing temperature. The decrease in adsorptive capacity with increasing adsorption temperature in case of acid red 73 may be due to a tendency for dye molecules to escape from the solid phase to the bulk phase with increasing temperature of the solution.

In case of acid blue 74 adsorption Fig.(III.45), the increase of adsorption capacity with increasing temperature may either be due to acceleration of some originally slow adsorption steps or to the creation of some new active sites on the adsorbent surface.

178 Chapter III Results and Discussion

35

30

25

25 0C (mg/g)

e 20 0 q 35 C 45 0C 15 65 0C

10

0 20 40 60 80 100 120 140 160 180

Ce(mg/l) Fig.(III.44): Temperature effect on acid red 73 adsorption onto BC-SDS-2105 carbon. Fig. (III.44): Temperature effect on acid red 73 adsorption onto BC-SDS-2105 carbon.

30 28 26 24 22 20 18 16 14 (mg/g) e 12 0 q 25 C 10 35 0C 8 0 6 45 C 4 65 0C 2 0 0 20 40 60 80 100 120 140

Ce(mg/l)

Fig. (III.45): Temperature effect on acid blue 74 adsorption onto BC-SDS-2105 carbon.

179 Chapter III Results and Discussion

5 25 0C 35 0C 0 4 45 C 65 0C

3 e /q e C 2

1

0 0 20 40 60 80 100 120 140 160 180 C e(mg/l) Fig.(III.46): Langmuir plots of acid red 73 adsorption on BC-SDS-2105 Fig. (III.46): Langmuir plots of acid red 73 adsorption on BC-SDS-2105 sample showing the effect on temperature.

8

7 25 0C 0 6 35 C 45 0C 5 65 0C

e 4 /q e C 3

2

1

0 0 20 40 60 80 100 120 140

C e(mg/l) Fig.(III.47): Langmuir plots of acid blue 74 adsorption on Fig. (III.47): Langmuir plots of acid blue 74 adsorption on BC-SDS-2105 showing the effect of temperature.

180 Chapter III Results and Discussion

Table (III.20): Characteristic parameters of the experimental data according to the Langmuir, Freundlich and Dubinin-Radushkevich models for the adsorption of acid red 73 and acid blue 74 onto sample BC-SDS-2105 at different temperatures.

Dye Temp Langmuir Frundlich Dubinin-Radushkevich 0 0 2 2 2 C q b R K n R qm B E R (mg/g ) ( l/g) (mg/g) (mg/g) (mol2/KJ2) (kJ/mol)

25 35.11 0.192 0.999 13.782 5.163 0.973 34.10 0.35x10-4 118.34 0.98

35 33.68 0.295 0.999 16.468 6.844 0.990 33.83 0.55x10-4 95.34 0.99 acid red 73 45 33.31 0.294 0.998 17.676 8.107 0.993 32.53 0.42x10-4 111.80 0.95

65 34.305 0.198 0.997 17.662 8.257 0.987 35.602 1.78x10-4 52.99 0.99 25 18.46 0.127 0.997 5.846 4.065 0.993 16.57 0.42x10-4 108.35 0.94 35 18.42 0.157 0.999 5.443 3.502 0.977 17.77 0.28x10-4 133.63 0.93 acid blue 74 -4 45 22.37 0.046 0.986 3.664 2.859 0.949 19.74 0.80x10 78.76 0.98 -4 65 27.04 0.068 0.992 4.412 2.643 0.962 23.52 0.22x10 151.09 0.95

181 Chapter III Results and Discussion

III A.3.7.2 Thermodynamic parameters.

The value of ¨ H0, and ¨ S0 were obtained from the slope and intercept of Van’t Hoff plot of ln Kc with the reciprocal temperature 1/T as shown in Fig.(III.48). The thermodynamic equilibrium constant Kc was calculated from Eq.(III.18). The thermodynamic parameters determined for the adsorption of acid red 73 and acid blue 74 on BC-SDS-2105 carbon are given in Table (III.21)

The exothermic nature of adsorption in case of acid red

73 adsorption is indicated by a decrease in Kc with temperature and the negative value of ¨ H0. Entropy change ¨ S0 has negative value in case acid red 73 adsorption, which suggests no significant change occur in the internal structure of BC-SDS- 2105 carbon during adsorption [Gupta et al., (2005)] and the sorbate molecules are stable on the solid surface resulting the loss of a degree of freedom at solid/liquid interface [Akyl et al., (1998) & Raji and Anirudhan, (1998)].

In case of acid blue 74 adsorption, the value of Kc increases with rise in temperature, i.e.,a negative temperature effect of acid blue 74 adsorption at high temperatures. This is confirmed by the positive value of enthalpy change (¨ H0). The positive value of entropy change (¨ S0) in case of acid blue 74 adsorption show the increase randomness at the solid/solution interface during the adsorption process of dye onto sample BC-SDS-2105 [Namasivayam and Ranganathan, (1995)] under action of heat.

182 Chapter III Results and Discussion

The values of ¨G0, which have been calculated from Eq.(III.19) are shown in Table (III.21). From this table, it is observed that all values of ¨G0 are positive in both of acid red 73 and acid blue 74 adsorption at all studied temperatures this indicates the formation of thermodynamically unstable adsorbed species [Alama et al., (2005)]. The slight change in the value of ¨G0 with increasing temperature indicates that the sorption of acid red 73 and acid blue 74 dyes onto sample BC- SDS-2105 becomes slightly changed at higher temperatures.

-0.3 acid red 73 acid blue 74 -0.4

-0.5 c -0.6 log K

-0.7

-0.8

-0.9 2.9 3.0 3.1 3.2 3.3 3.4 3.5 1/TX103

Fig. (III.48): Van'ts Hoff plots of acid red 73 and acid blue 74 sorption onto sample BC-SDS-2105

183 Chapter III Results and Discussion

Table (III.21): Thermodynamic parameters of acid red 73 and acid blue 74 adsorption onto sample BC-SDS-2105 at different temperatures.

0 0 0 Dye Temperature Kc ¨G ¨H ¨S K (kJ/mol) J/mol.k J/mol.k

298 0.296 3.015

308 0.284 3.221 -4.250 -24.277 acid red 73 318 0.274 3.421

338 0.242 3.984

298 0.181 4.234

308 0.241 3.641 9.893 19.624

acid blue 74 318 0261 3.550

338 0.300 3.380

184 Chapter III Results and Discussion

III.B LIQUID EMULSION MEMBRANE TECHNUQUE:

Consumption of heavy metals and their usage is increasing steeply while their availability is diminishing drastically. Even the low quantities of heavy discharged in effluents cause serious environmental and health problems [Rajendra et al., (1987)]. According to the World Health Organisation [IPCS, (1988)], the most toxic metals are aluminium, chromium, iron, cobalt, nickel, copper, zinc, cadmium, mercury and lead. Hence, removal and recovery of these heavy metals from effluents is of great importance. Among the technical options for the extraction and separation of heavy metals dissolved in effluents are precipitation (pyrometallurgical) and filtration which generate solid wastes. Electrochemical processes [Van Berkel, (2000) & Lupi and Pasquali, (2003)] are also used for metal ions recovery which are less efficient and uneconomical for dilute streams. Ion-exchange (IX) methods [Inglezakis and Grigoropolou, (2003)], cementation [Choo and Jeffrey, (2004)] are others technologies which used for removal of heavy metal from effluents, even though these technologies have several advantage, they have many serious economical and technical limitations and are basically recommended when the concentration of metal ions in solution is high. Liquid-liquid extraction for metals recovery from effluents [Venkateswaran and Palanivelu, (2004)] is anther option. Through this operation extracts solute, it releases a waste solution or stream which has the contaminant metals and this has to be stripped by another operation to avoid disposal problems. Separation techniques based on liquid membranes offer high scope and potential [Raghuraman et al., (1993) & Raghuraman et

185 Chapter III Results and Discussion al., (1994) & Li, (1968 ) & Li, (1971) & Kitagawa et al., (1977) &De Gyves and Rodriguez de San Migul, (1999) & Lee et al., (1978) & Dwozak and Naser, (1987) & Chakravarti et al., (1995) & Asraf Chaudry et al., (1997) & Chakravarti et al., (2000) ] due to its characteristics such as ease of operation, lesser energy requirement and high selectivity. Compared to supported liquid membranes, LEM also offers other advantages of large interfacial area, low cost factors and a single stage operation of both extraction and stripping. It finds more application in the industrial effluent treatments [Kumaresan et al., (2003)] and in waste treatments [Shukia and Misra, (1995) & Zhi-Fa Yang, (1996) & Mohammed and Marimuthu, (2000)]. III.B.1 Extraction of Cobalt from Wastewater Using Liquid Emulsion Membrane.

The applicability of the Liquid Emulsion Membrane (LEM) process for the removal of cobalt ions was investigated. The aim of this work is to find a process for the purification of wastewater, which contains cobalt ions. In the extraction of Co (II) from nitrate medium by Cyanex 301, the effect of some parameters such as type of diluent, nitric acid concentrations in feed solution and effect of internal aqueous solution were investigated. A complete study of the cobalt ions permeation by liquid emulsion membrane process using Cyanex 301 as extractant is performed in terms of extraction and stripping efficiencies and emulsion stability were investigated. The influence of different parameters such as nitric acid concentration in external phase, carrier concentration, type of stripping agent, type of surfactant and effect of surfactant concentration was studied. 186 Chapter III Results and Discussion

III B.1.1 Liquid –liquid extraction investigation.

III B.1.1.1 Effect of diluent type in the extraction of Co(II) ions. The suitability of some diluents for the extraction of cobalt (II) by the proposed method was tested. Table (III.22) showed that cyclohexane gives the maximum extraction (88 %) as diluent compared to toluene and benzene.

Table (III.22): Effect of diluent type on percent of extraction

Extraction percent Diluent type (% E) Cyclohexane 88 Toluene 69 Benzene 58.5

III B.1.1.2 Effect of nitric acid concentration. The effect of nitric acid concentrations on the extraction percent of cobalt ions (100 mg/l) was studied using different nitric acid concentrations in the range from 0.01 to 2.0M. Fig.(III.49) illustrated that the extraction of cobalt ions was maximum especially from dilute nitric acid solution Therefore the extraction percent decreases with increasing nitric acid concentration from 0.01 to 2.0 M, as well known the cationic exchange being more difficult when the acidity increased, due to competition with hydrogen ions [Bourenane et al., (2003)]. These results indicate that Cyanex 301 is suitable for the extraction of cobalt ions at low nitric acid concentration (10-2 M).

187 Chapter III Results and Discussion

90

80

70

60

50

40 %Extraction 30

20

10

0 0.0 0.5 1.0 1.5 2.0 Nitric acid concentration / M

Fig. (III.49): Effect of nitric acid concentration on the percent of extraction of cobalt by Cyanex 301 in cyclohexane.

III B.1.1.3. Effect of type of stripping agents.

Stripping of the extracted cobalt species from their organic phases was investigated using different stripping agents. Aqueous solutions of HCl, H2SO4, H3PO4, HNO3 and NaOH were tested as stripping agents. The data obtained are given in Table (III.23). From this table, it is clear that, HCl is the best stripping agents for cobalt ions from Cyanex

301compared to H2SO4, H3PO4, HNO3 and NaOH.

188 Chapter III Results and Discussion

Table (III.23): The effect of different stripping agents on the stripping % of cobalt from Cyanex 301

Stripping agent Stripping efficiency, %

HCl, 3M 81

H2SO4, 3M 50

H3PO4, 3M 50.2

HNO3, 3M 46 NaOH, 0.1M 4

III B.1.1.4 Effect of stripping agent concentration.

The effect of stripping agent concentration on extracted Co (II) from Cyanex 301 in cyclohexane was studied. Fig. (III.50). showed that the stripping efficiency of Co(II) increases with increasing the concentration of HCl from 0.01 to 5 M. This may be due to the increase of hydrogen ion concentrations in the right hand side of the equilibrium Eq. (III.26) which enhance the reversible reaction direction

2+ + M +2HB ļ MB2 +2H …...... (III.26)

189 Chapter III Results and Discussion

100

80

60

40

Strippingefficiency% 20

0 0 1 2 3 4 5 6 7 Concentration of HCl, M

Fig. (III.50): Effect of HCl concentration on the stripping of Co (II) from Cyanex 301/cyclohexane solution: [Co(II)] = 100 ppm, Cyanex 301 = 4% (v/v), [HNO3] = 0.01 M

III B.1.1.5 Effect of shaking time.

Kinetic investigation was carried out in order to determine the effect of shacking time on the extraction % of cobalt ions (100 mg/L) in 0.01 M HNO3 by Cyanex 301/ cyclohexane. In this concern, the time ranging from 1 to 30 minutes were tested. The results are depicted in Fig. (III.51), it is obvious that the extraction percent of Co ions increases with increasing the shacking time and the extraction was very fast and maximum extraction % was 90 % of cobalt ions extracted after 15 min

190 Chapter III Results and Discussion

100

90

80

70

60

50

Extraction percent (%E) percent Extraction 40

30

20 0 5 10 15 20 25 30 Time,min. Fig. (III.51): Effect of time on the extraction of cobalt by Cyanex 301 in cyclohexane from 0.01 M nitrate medium: [Co(II)] = 100 ppm; [CYanex 301] = 4% (v/v) T = 25±1oC.

III B.1.1.6 Effect of carrier concentration.

To study the effect of carrier concentration, cobalt (II) ions was extracted from 0.01 M HNO3 of diffirent concentrations of Cyanex 301. The Cyanex 301 concentrations were varied from 2- 8 % (V/V). As shown in Fig.(III.52), increasing the amount of carrier concentration lead to increase the extraction percent of Co(II) ions. At the same time, increasing the carrier concentration over a certain limit does not result in a benefit but decrease the extraction percent due to the increase in viscosity, which leads to large globules. On the other hand, the increase in the concentration of the carrier also promotes the permeation swelling, which dilutes the aqueous receiving phase and decreases the efficiency of the process. The maximum extraction of Co(II) ions is found at carrier concentration of 6 % (v/v). 191 Chapter III Results and Discussion

100

99

98

97

96

95

94

93

Extraction percent (% E) 92

91

90 012345678 Carrier concentration (v/v) Fig.(III.52): Effect of carrier concentration on percenttage of Co(II) extraction

Fig. (III.52): Effect of carrier concentration on percentage of Co (II) extraction.

III B.2 Permeation of Cobalt (II) Ions Using LEM.

The permeation of the cobalt ions from nitric acid solution through the prepared emulsion membrane was investigated. The composition of the prepared liquid emulsion membrane was chosen based on the results obtained from the equilibrium extraction investigation. Stability of membrane plays very important role in LEM separation technique. Therefore the stability of the prepared LEM was studied. Effect of various parameters such as time and speed of emulsification, extractant concentration, selection and concentration of surfactant, stirring

192 Chapter III Results and Discussion speed and volume ratio of the membrane phase to the aqueous external phase were also investigated.

III B.2.1 Transport mechanism of cobalt (II) extraction process using LEM.

Liquid emulsion membranes (LEMs) are formed by mixing two immiscible phases (water in oil, W/O) and dispersed by mild agitation in a third, aqueous phase. The dispersed internal phase is separated from the external phase by a very thin film of oil that acts as a barrier “liquid membrane” between the two aqueous phases.

From a theoretical point of view, the metal transport mechanism through LEM could be explained by the following steps: (1) Diffusion of metal ions to the membrane-external phase interface. (2) Formation of complex by reaction between the carrier (Cyanex 301) with metal ions. (3) Diffusion of the metal- extractant complexes through the membrane phase to the membrane-internal aqueous phase interface. (4) Finally, a stripping ( back-extraction) reaction between the complex and the acid stripping agent takes place. (5) Extractant species diffused back to feed/membrane interface.

193 Chapter III Results and Discussion

The metal ions are transported from the external phase to the internat phase by diffusion-facilited transport mechanism using the carrier as well as hydrogen concentration gradient across the membrane phase.

III B.2.2 Emulsion stability.

The satbility of LEM plays an important role in the permeation process. The parameters affecting the stability of LEM are surfactant type, surfactant concentration, stirring speed, contact time and …. etc., therefore when LEM is dispersed in the external aqueous phase, the emulsion must be sufficiently stable in order to extract the metal ions into the internal aqueous. The LEM breakdown will result on operation failure and lower the extraction efficiency and loss of the extracted species. The LEM globules are stabilised by adding suitable surfactant and the degree of permeation of extracted metal species into the internal aqueous phase is highly affected by the degree of LEM stability. The stability of LEM was investigated by tracing the red dye (acid red 73) which loaded in the internal aqueous phase and detect the leakage of the red dye in the external aqueous phase.

The percentage of leakage (%) was determined using the following Eq. (III.27) [Miesiac et al.,(1992)]:

C Leakage (%) = ext X100 ……………….(III.27) Cint

194 Chapter III Results and Discussion

Where: Cext = the concentration of red dye leaked from the internal phase to the external phase.

Cint, max = the total concentration of red dye in the internal phase.

The emulsion composition used during the stability studies of membrane under investigation was the following unless otherwise stated, concentration of Cyanex 301 was 6% (v/v), different surfactants were used; and the internal aqueous phase was 3 M HCl and a red dye ( acid red 73) was used as a tracer, and the temperature was 25 oC.

The external aqueous phase was 0.01M nitric acid containing cobalt ions and the membrane /feed ratio was 10:100 ml

III B.2.2.1 Effect of type of surfactant.

Surfactants play very important role in the formation and in the stability of liquid emulsion membrane. The effect of surfactant type on the amount of red dye leaked from the internal aqueous phase to the external aqueous phase was studied using different surfactants with constant concentration of 4 % (v/v). The different surfactants used were, span80, ArlacelA and sesquioleate. The leakage % as a function of time is illustrated in Fig.(III.53), for different surfactants investigated. It was found that, span80 has a highest stability (lowest leakage percent) for the LEM globules.

195 Chapter III Results and Discussion

50

45 Span 80 Aracyl A 40 Sesquioleate 35

30

25

20

Leakage(%) 15

10

5

0 0 5 10 15 20 25 Time, min. Fig.(III.53): Effect of type of surfactant on the leakage(%) Fig. (III.53): Effect of type of surfactant on the leakage (%) of LEM in nitric acid medium.

III B.2.2.2 Effect of surfactant concentration.

The effect of surfactant concentration (Span 80) in the prepared LEM were studied using different span 80 concentrations varies from 2 % to 6% (v/v). Fig.(III.54) showed that the stability of LEM increases with increasing spen 80 concentration but there is no big stability difference between 4 % and 6% (v/v), hence 4 % (v/v) was the optimum Span 80 concentration which used in further studies to avoid the probability of LEM swelling.

196 Chapter III Results and Discussion

50

45 2% (v/v) 4% (v/v) 40 6% (v/v) 35

30

25

20

Leakage(%) 15

10

5

0 0 5 10 15 20 25 Time,min.

Fig. (III.54): Effect of surfactant concentration on the leakage (%) of LEM in nitric acid medium.

III B.2.2.3. Effect of emulsification speed.

Experiments were performed with cyanex 301 (6 %) , span 80 (4 %) , a concentration of internal phase (HCl) of 3 M, cyclohexane as a diluent, a ratio of membrane / internal phase ratio is 1, rotating speed of 250 rpm, emulsion volume 10 ml and external phase volume of 100 ml, the temperature of 25 0C with different emulsification speed. (2000, 3000, 4000, 5000, 6000 and 7000 )

Fig.(III.55) shows that the stability of LEM increases with increasing the emulsification speed. An efficient emulsification gives a good dispersion of the internal phase drops into the membrane phase. As the fact that, these drops

197 Chapter III Results and Discussion become smaller so it will take much more time to coalesce leading to good stability of the emulsion. In addition, the size of internal phase droplets is samller at greater emulsification speed, creating a large surface area for permeation and hence obtaining a higher fraction of recovery. The optimal emulsification speed was found to reach at the value of 6000 rpm with a leakage of 3.3 %.

10

9

8

7

6

5

4 Leakage(%) 3

2

1

0 1000 2000 3000 4000 5000 6000 7000 Emulsification speed (rpm)

Fig. (III.55): Effect of emulsification speed on the stability of emulsion in nitrate medium.

198 Chapter III Results and Discussion

III B.2.2.4 Effect of stirring speed.

As expected the sability depends greatly on the stirring speed on the stirring tank. Fig. (III.56) shows the effect of stirring speed on stability of liquid emulsiom membrane in stirred tank. It is obvious from the figure that the stirring speed at 250 rpm gives a lower leakage percent. However, there was a little difference in stability rate over 250 rpm. When the level of stirring is decreased (< 250 rpm), the size of the emulsion globules increases and the interfacial area available for mass transfer decreases. On the other hand, the leakage up of the emulsion is more pronounced and leakage of the internal phase occurs. This can be explained by the increase of the osmotic swelling of the membrane. Increasing the speed of stirring above a critical value (250 rpm) not affects the stability of emulsion but also does not increase the extraction efficiency considerably. By increasing the stirring speed, the shear force, which acts on the emulsion globules, is increased, and this makes the globules smaller. The area for mass transfer increases but the membrane ruptures, this lead to spill of the internal stripping phase into the outer continuous phase. Hence, the optimum stirring speed was taken as 250 rpm. The same result was obtained by Gasser et al., (2008) who found that, the optimum stirring speed was taken as 300 rpm for removal of Co(II) using Cyanex 923 as extractant from thiocyanate medium through liquid emulsion membrane.

199 Chapter III Results and Discussion

20

18 150 rpm 250 rpm 16 350 rpm 14

12

10

8

Leakage (%) Leakage 6

4

2

0 0 5 10 15 20 25 Time,min.

Fig. (III.56): Effect of stirring speed on the stability of LEM in nitrate medium.

III B.2.2.5 Effect of internal phase concentration on the stability of LEM.

Experiment was conduted under the same conditions as mentioned previously, using a stirring speed of 250 rpm and different concentrations of HCl as internal aqueous phase from 0.5 to 5 M to study the stability of LEM under each concentration. Fig. (III.57) shows that the stability of LEM decreases with increasing the HCl concentration. This may be due to the reaction between HCl and the surfactant which is responsible for the stability of membrane, that consequently led to a destabilization of the emulsion.

200 Chapter III Results and Discussion

5

4

3

2 Leakage (%) Leakage

1

0 0 1 2 3 4 5 HCl concentration, (M)

Fig. (III.57): Effect of stripping phase concentration on the stability of emulsion in nitrate medium.

III B.2.2.6 Effect of volume ratio of the organic phase to the aquoues internal phase.

The effect of volume fraction of the prepared LEM on the stability of membrane was studied under the same conditions The volume ratios of the organic phase to stripping phase were varied between 0.2 to 2. Fig. (III.58) shows that the stability of LEM increases with increasing the volume fraction ratio of prepared LEM. This result may be explained on the basis of increasing volume fraction leads to increasing the thickness of the membrane oil layer of LEM which increases the stability of membrane. In the other hand increases the thickness of membrane oil layer decrease both the permeation rate and the capacity of the internal aqueous phase. Hence, in order to obtain a uniform and 201 Chapter III Results and Discussion homogeneous distribution of the internal phase droplets in the membrane space and to avoid the influence of HCl on the emulsion stability, the optimum phase ratio of organic phase to internal aqueous was taken to be 1.

10

9

8

7

6

5 Leakage(%)

4

3

2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 organic phase/internal phase (v/v) Fig.(III.58): Effect of volume ratio of organic phase to internal aquoues phase on Fig. (III.58): Effect of volume ratio of organic phase to internal aqueous phase on the stability of emulsion in nitrate medium. III B.2.2.7 Effect of volume ratio of W/O emulsions to the aqueous external phase.

Experiment was conducted by taking into account the parameters already optimized and the volume ratios of emulsion to external phase varied between 0.1 to 0.5 Fig. (III.59) shows the effect of variation of this ratio on the stability of the emulsion. It is evident that the increase of volume ratio of emulsion to aqueous external phase leads to decrease of the

202 Chapter III Results and Discussion emulsion leakage. But with increasing this volume ratio, the swelling phenomenon becomes remarkable, fast and accompanied by a more significant coalescence of the internal droplets which grow. So, as the leakage values remain acceptable for the studied volume ratios range. Therefore, the volume ratio of emulsion to the external phase used in further studied was 0.1.

5.0

4.5

4.0

3.5

3.0

2.5

2.0

Leakage (%)Leakage 1.5

1.0

0.5

0.0 0.1 0.2 0.3 0.4 0.5 0.6 volume of emulsion phase/volume of external phase

Fig. (III.59): Effect of volume ratio of emulsion phase to external phase on the stability of the emulsion in nitrate medium.

III B.2.3 Factors affecting the permeation process of cobalt by LEM.

Based on the results obtained from liquid-liquid extraction studies of cobalt, and the stability of the liquid emulsion membrane studies, the emulsion composition used during the investigations of some important factors affecting the rate of

203 Chapter III Results and Discussion permeation of cobalt through LEM is the following; unless otherwise stated: cobalt ion concentration in the external aqueous phase was (100-300) mg/l cobalt, in (0.01- 0.5) M nitric acid medium, Cyanex-301 concentration was 2-8% (v/v), span 80 4 % (v/v) in cyclohexane, ratio of organic phase to internal aqueous phase was taken to be 1 (v/v), the emulsion phase volume to the external aqueous phase volume was 10:100 (v/v), the temperature was 25 oC, the internal aqueous phase was 3 M HCl, stirring speed 250 rpm, emulsification speed 6000 rpm and emulsification time 5 min.

III B.2.3.1 Effect of nitric acid concentration in external phase.

Fig.(III.60) shows the effect of nitric acid concentration in the external aqueous phase on the (permeation %) of cobalt through LEM. Different nitric acid concentrations were used ranging from 0.01 to 0.5 M. It was found that, the (permeation %) of cobalt decreases with increasing the nitric acid concentrations. This may be due to the competition between cobalt ions and hydrogen ions at the membrane feed interface at high nitric acid concentration.

204 Chapter III Results and Discussion

100

80 0.01 M HMO3

0.1 M HNO3

0.5 M HNO3

60

40 Permeation % Permeation

20

0 0246810121416 Time, min. Fig.(III.60): Effect of nitric acid concentration in the external phase Fig. (III.60): Effect of nitric acid concentration in the external phase on the % permeation of cobalt through LEM.

III B.2.3.2 Effect of carrier concentration.

The effect of carrier concentration (Cyanex 301) on the permeation % of Co(II) ions is studied. Fig.(III.61) shows that the permeation % of Cobalt ions increases with increasing Cyanex 301 concentration. This is due to the fact that, with increasing Cyanex 301 concentration, the formation of Cyanex 301/cobalt ion complex is greater at the feed/membrane interface. Hence the concentration gradient increases in the peripheral oil layer, thereby increasing the diffusion rate of cobalt through LEM.

205 Chapter III Results and Discussion

110

100

90

80

70

60

50 2 % (v/v)Cyanex 301 40 6% (v/v)Cyanex 301 Permeation, % Permeation, 8% (v/v)Cyanex 301 30

20

10

0 0 2 4 6 8 10121416 Time, min. Fig.(III.61): Effect of Cyanex 301 concentration in the membrane phase Fig. (III.61): Effect of Cyanex 301 concentration in the membrane phase on the permeation, % of cobalt through LEM.

III B.2.3.3 Effect of initial cobalt concentration of the feed phase. Fig.(III.62) shows the effect of cobalt ions concentration in the external aqueous phase on the permeation, % of cobalt ions by LEM. As expected, permeation % of cobalt ions decreases with increasing the initial concentration of cobalt ions in the external aqueous phase, this may be due to, the internal aqueous phase in the emulsion globule is more rapidly saturated with cobalt ions and thus the pH gradient between the external and the internal phases as well as the capacity of chloride ions to trap cobalt decrease faster. Also it is very clear that the total concentration of cobalt ions permeated increases with increasing the initial cobalt ions concentration.

206 Chapter III Results and Discussion

100

80

60 100 ppm cobalt 200 ppm cobalt 40 300 ppm cobalt Permeation, (%)

20

0 0 2 4 6 8 10 12 14 16 Time, min. Fig.(III.62): Effect of initial cobalt concentration in the feed phase Fig. (III.62): Effect of initial cobalt concentration in the feed phase on the permeation, % of cobalt through LEM.

III B.2.3.4 Effect of stripper concentration in the internal aqueous phase.

The results of the effect of stripping internal phase concentration on permeation % of cobalt ions, showed that when HCl concentrations increase in the rang 3-5 M no significant increase in the permeation % as showen in Fig. (III.63 ) as the permeation % of cobalt reach to 90% and does not increase significantly by increasing the concentration of stripping agent (HCl).

207 Chapter III Results and Discussion

100

95

90

85 3M HCl 4M HCl 5M HCl 80 Permeation, Permeation, % 75

70

0 2 4 6 8 10 12 14 16 Time, min.

Fig. (III.63): Effect of HCI (stripper) concentration in the internal aqueous phase on the permeation % of Co (II) ions.

However, for a concentration of HCl greater than 3M, the emulsion swells up and this lead to decrease the stability of the membrane. So the optimal stripping concentration is found to be 3M HCl.

III B.2.4 Extraction kinetics of Co (II) ions by LEM.

To describe the overall permeation kinetics of Co(II) ions we used the model reported by [Teramoto et al., (1986)]. In order to get a quantitative measure of kinetics of Co(II) complexation and permeation, the following simple first order rate equations (III.28) and (III.29 ) was applied.

208 Chapter III Results and Discussion

C t - k obs t = e ………….……………(III.28 ) C 0

C t ln = - k obs t ……………..……(III.29) C 0

Where (Ct) and (C0) are the concentration of Co(II) ions remained at time (t) and the initially present in the external phase solutions, respectively. Fig.(III.64 ) represents the first order plots for different parameters affecting on cobalt permeation and the values of kobs were calculated from the slopes of straight lines. The plot of log-log relations between kobs and these different parameters gave linear relations. + Plotting log K obs versus logarithim of the [H ], [Cyanex 301], [Co(II)] and [HCl] concentrations, gives their power dependency Fig.(III.65 ). From this figure, it is clear that the rate constant was inversely dependent on [HNO3] concentration in external phase and on [Co (II)] concentrations where slopes § -1and -1.5, respectively were obtained. But the rate constant depends on [Cyanex 301] concentration as extractant as a slope §1 was obtained. The rate constant was found to be independent on [HCl] concentration in the internal phase. From these data, the rate of Co(II) permeation at 25 0C at a ratio of membrane to external phase volume of 0.1 can be represented by the following relation:

-1 -1.5 1 0.12 d[C]per /dt= K[HNO3] [Co (II)] [CYANEX 301] [HCl]

Where [C]per is the concentration of the permeated Co(II) and K is a constant.

209 Chapter III Results and Discussion

-1.0 + -1.2 [H ] [Cyanex 301] -1.4 [Co(II)] -1.6 o [Hcl] -1.8

-2.0

0 -2.2 /C t -2.4 ln C -2.6 -2.8 -3.0 -3.2 -3.4 -3.6 10 20 30 40 50 60 70 Time,sec.

Fig. (III.64): First order plots for permeation of cobalt from nitrate medium in cyclohexane; [Co(II)] = 100 PPM; [Cyanex 301] = 6% (v/v); 0.01 HNO3; [HCl] = 3 M; [Span 80] = 4% (v/v); stirring speed = 250 rpm; feed volume; emulsion volume = 10:1

4 [H+] 3 [Cyanex 301] [Co(II)] 2 slope= 0.12 o [Hcl]

1 -1

,S 0 slope= -1.5 obs slope= -0.97 -1 slope=0.703

log K -2

-3

-4

-5

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

log[HNO3],[Cyanex 301],[Co(II)],[Hcl]

Fig. (III.65): Effect of [HNO3] [Cyanex 301] [Co(II)] and [HCl] concentrations on the rate constant of Co (II) ions permeation by Cyanex 301 in cyclohexane from nitrate medium through liquid emulsion membrane: [surfactant] = 4% (v/v/); stirring speed 250 rpm; feed volume: emulsion volume = 10: 1; T = 25±oC.

210 Summary

SUMMARY

nvironmental pollution, as a consequence of the Eindustrialization process, is one of the major problems that has to be solved and controlled. The most important treatment processes for metals and dyes contaminated waste streams include chemical precipitation, membrane, filtration, ion exchange, carbon adsorption and coprecipitation/adsorption. However, all these techniques have their inherent advantages and limitations in applications. These processes usually need expensive facility and high maintenance cost. Therefore, there is a need for more economical alternative technologies for the treatment of metals and dyes contaminated waste streams.

The aim of present work is to study the treatment of some hazardous substances such as heavy metals e.g. ( lead, cobalt and strontium) and dyes e.g. ( acid red 73, and acid blue 74 ) using either adsorption or liquid emulsion membrane techniques.

The experimental part deals with the application of adsorption and liquid emulsion membrane techniques for removal of some hazardous substances such as metal ions ( ead, cobalt and strontium) and dyes (acid red 73 and acid blue 74). All the apparatus and techniques employed were described.

In the adsorption technique, 23 samples of activated carbons were prepared by either physical or chemical methods using bone char as precursor. In this concern, activated carbon prepared as follows: (i) by physical activation (either steam or

211 Summary

N2 gas ); (ii) by chemical activation either by mineral acids

(HCl, HNO3, H2SO4 and H3PO4) or strong alkalies (KOH and NaOH) or organic compounds (sodium dodecyl sulphate) (SDS) were prepared. Sorption behavior of 5- adsorption systems were examined. These are: BC-SDS-2105: Pb,

BC-S-2750 : Co, BC-N2-2500 : Sr, BC-SDS-2105: acid red 73 and BC-SDS-2105: acid blue 74 and the factors affecting adsorption process were described. In liquid emulsion membrane technique, the extraction of Co(II) ions using Cyanex 301 as extractant in cyclohexane from nitrate medium was investigated to determine the suitable conditions for the permeation of Co (II) ions by the membrane used. The factors affecting the stability of the prepared liquid emulsion membrane was studied in terms of leakage percent at different parameters. The factors affecting the permeation process for Co(II) ions were also investigated.

The results of the first part of this study describes the physicochemical and adsorption properties of the 24-activated carbons derived from bone char and prepared by physical or chemical activation methods. In this concern, characterization of the used five adsorbents in our applications exhibited bulk density greater than 0.25 g/cc. i.e. the value of density reported by American Water Works Association (AWWA) as the lower limit of activated carbon of the bulk density to be of practical use. The high ash content of activated carbons made from bone char can be explained by their high specific mineral content, especially their richness in silica (SiO2), iron oxide (Fe2O3),

212 Summary magnesium oxide (MgO), and calcium oxide (CaO) and phosphorous oxide (P2 O5).

From N2 isotherms, samples activated by physical activation, (BC-N2-2500) had the highest surface area (117.71 m2/g) with the highest pore volume (0.1cc/g) and possess a mesopore volume representing 56 % of the total pore volume. This is due to nitrogen as activating agent instead of steam in physical activation is felt in terms of two competing mechanisms, namely, micropore formation and pore widening. In case of steam activation, sample BC-S-1750 is essentially a mesoporous carbon, as the mesopore content reaches a value of 73 % of total pore volume and BET surface area of 27.03 m2/g . But in case of sample BC-S-2750, micropores and mesopores formation are the dominating mechanisms as the mesopores content represents 52 % of the total pore volume with surface area of 48.93 m2/g. This means that by increasing the hold time, the surface area increases and mesoporesity decreases. In case of chemical activation, it was found that using sodium dodecyl sulphate in sample BC-SDS-2105 gives active carbon with the highest surface area of 81.90 m2/g and highest mesoporesity of 76% but using potassium hydroxide in sample BC-K70%-1500 gives the lowest surface area of 3.19 m2/g and low mesoporosity of 54 %.

The scanning electron microscopy (SEM) images of bone char samples before and after activation, showed relatively heterogeneous morphology of particles and channels. The

213 Summary particles had irregular shapes with edges and corners. The FTIR spectra of the bone char samples indicated a series of bands in the mid-infrared region. These bands can be divided into three main categories associated with phosphate, carbonate and hydroxyl groups. On the basis of pH measurement, the prepared carbons show slightly basic surfaces (pH = 7.85 - 10.43).

In the second part of this investigation, the untreated bone char and the prepared activated carbons were tested for removal of lead, cobalt, strontium, acid red 73 and acid blue 74 from aqueous solution. BC-S-2750 and BC-N2-2500 carbons were found to be the most effective in removal of cobalt and strontium; respectively. BC-SDS-2105 carbon exhibited the highest capacity for removal of lead, acid red 73 and acid blue 74 compared to the other carbons. Factors affecting adsorption process proved that the reaction rate was fast, requiring only a short contact time for metals ( lead, cobalt and strontium ) but the rate was slow, requiring long contact time for dyes (acid red 73 and acid blue 74). The equilibrium steady state was reached at 120, 60, and 120 min. for lead, cobalt, and strontium; respectively. In case of acid red 73 and acid blue 74, the equilibrium was attained after shaking for about 48 hrs. The pseudo-first and second order kinetic models were applied.

For lead and cobalt the calculated qe (equilibrium adsorption capacity) values obtained from pseudo-second order rate expression are in good agreement with the experimental data

(qe,exp). In case of strontium, the pseudo-first order kinetic

214 Summary

model is the predominant due to the calculated value qe, agrees very well with the experimental data qe,exp.

The kinetic data of the dyes can be described well by second order rate equation due to the high values of correlation coefficient R2 for second order adsorption model compared to that of pseudo-first order model and the calculated equilibrium adsorption capacities (qe,cal) from second order model agree well with the experimental values. These results suggest that this sorption system is not first order reaction and the rate-limiting step may be chemical sorption. 0.5 The linear portion of the curves of qt vs. t plots for all studied sorption systems do not pass through the origin point. This proved that the intra-particle diffusion was not the only rate-controlling step. The sorption mechanism of these sorption systems from aqueous solution is rather a complex process, probably a combination of external mass transfer and intra- particle diffusion which contribute to the rate determining step. The adsorption edge for Pb (II) was found in the pH range 2- 5. While the adsorption edge was found in the pH range 2-6 for Co (II) and that of Sr (II) was found in the pH range 2-8.

The adsorption isotherms such as Langmuir (L), Freundlich (F) and Dubinin-Radushkevich (DR) were used to model the experimental data.

All the adsorption studied systems followed the Dubinin- Radushkevich (DR) model. From the DR isotherm parameters, the E-values obtained in case of cobalt and strontium adsorption 215 Summary are in the energy range of an ion-exchange reaction i.e., 8-16 kJ/mol. But the value of lead sorption free energy indicated that lead is adsorbed by physisorption i.e., (20-40 kJ/mol). In case of acid red 73 and acid blue 74, the E-values obtained are in the energy range 52.99-133.63 kJ/mol, i. e. acid red 73 and acid blue 74 are adsorbed by hemisorptions. The thermodynamic parameters of lead, cobalt, strontium, acid red 73 and acid blue 74 were calculated. The data indicat that lead, cobalt, strontium and acid blue 74 sorption are better occurred at higher temperature while acid red 73 sorption is not affected by increasing temperature.

The third part is concerned with the use of liquid emulsion membrane technique in removal of Co (II) ions from aqueous solution. In this part, the permeation of cobalt (II) ions from aqueous solution by a liquid emulsion membrane containing Cyanex-301 in cyclohexane was experimented based on liquid-liquid extraction studies. The effect of nitric acid concentration from 0.01 to 2.0 M on the extraction of Co was studied. It was found that, the extraction percent of cobalt decreases with increasing nitric acid concentration. HCl was found to be the best stripping agent for cobalt ions from

Cyanex 301 as compared to H2SO4, H3PO4, HNO3 and NaOH and the stripping efficiency of Co(II) increases with increasing the concentration of HCl from 0.01 to 5 M. The extraction percent of Co ions increases with increasing the shacking time and the extraction was very fast and the maximum extraction percent obtained was 90 % after 15 min.

216 Summary

The increase in the amount of carrier concentration leads to an increase in the extraction percent of Co(II) ions.

Slope analysis showed that cobalt ions extracted as MB2. The stability of the prepared LEM in nitric acid medium was studied using the different surfactants (Span80, Arlacel A and Sesquioleate ). It was found that Span 80 gives the most stable emulsion compared with ArlacelA and Sesquioleate. The effect of Span 80 concentration on the stability of emulsion globules was studied. It was found that, the stability of LEM increases with increasing the surfactant concentration from 2 to 6 % ( v/v).

The factors affecting the permeation of cobalt were studied and lead to the following:

· The permeation percent of cobalt ions decreases with increasing the nitric acid concentrations in the external aqueous phase.

· the permeation percent of cobalt ions increases with increasing Cyanex 301 concentration.

· The permeation percent of cobalt ions decreases with increasing the initial concentration of cobalt ions in the external aqueous phase.

· The permeation percent of cobalt ions has insignificant or slight increase when HCl concentration increased in the rang 3-5 M.

217 Summary

From these data, the rate of Co(II) permeation at 25 0C at a ratio of membrane to external phase volume of 0.1 can be represented by the following relation:

-1 -1.5 1 0.12 d[C]per /dt= K[HNO3] [Co (II)] [CYANEX 301] [HCl]

Where [C]per is the concentration of the permeated Co(II) and K is a constant.

218 References

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Zanzi R., Bai X., Capdevila P. and Bjorbom E.; World Congress of Chemical Engineering, Melboutne, Australia 23-27 September, (2001).

247 Arabic Summary ÌHh¥¸@ ua¹›@

ŚŕƊƔŷƉƈřŷƏƈŠƈŽƔŰƏśƏũƔŲţśƓƅŔřƅŕŬũƅŔƋŨƍŽŧƎś řƔŮŻƗŔ Ə ŪŔŪśƈƗŔ ŚŕƔƆƈŷ Ɖƈ ĻƜƄ ƇŔŧŦśŬŔƏ ųŮƊƈƅŔ ƉƏŗũƄƅŔ řƔƏŲŸƅŔŚŕżŗŰƅŔƏřƆƔƂŝƅŔ ƉŧŕŸƈƅŔ űŸŗřƅŔŪŏƓžřƆœŕŬƅŔřŗƆţśŬƈƅŔ şśŕƊƅŔ ŚŕƊŔƏƔţƅŔ ƇŕŴŷ Ƈţž ƇŔŧŦśŬŔ Ƈś ŧƁƏ .řƔœŕƈƅŔ ŕƎƆƔƅŕţƈ Ɖƈ ūƄŸƊƔ ƒŨƅŔƏ ƉƔƄŗ řƄũŮŗ ŚŕƔƏŕƈƔƄƅŔƏ ŚŕƔƏŗƅŔ řŷŕƊŰ Ɖƈ ŽƆŦƈƄ ƇƄŔũśƉŷƇŠŕƊƅŔƓœƔŗƅŔũŝƗŔŽƔſŦśŽŧƎŗřƄũŮƅŔřœƔŗƓƆŷŖƆŬƅŕŗ řƆƔƂŝƅŔƉŧŕŸƈƅŔűŸŗƅ řƅŔŪƗŔŚŕƔƆƈŷŚƔũŠŔƏ .řƄũŮƅŕŗ ŽƆŦƈƅŔ ŔŨƍ řƔƏŲŸƅŔŚŕżŗŰƅŔƏ (ƇƏƔŮƊŔũśŮƗŔƏŚƆŗƏƄƅŔƏůŕŰũƅŔ)

ƇśŕƈƄ .ŪŔŪśƈƗŔřƔƆƈŷƇŔŧŦśŬŕŗ (acid red 73 and acid blue 74) ¿ŕŝƈƄŚƆŗƏƄƅŔƉƏƔŔřƅŔŪŏƓžřƆœŕŬƅŔřŗƆţśŬƈƅŔřƔŮŻƗŔřƔƆƈŷƀƔŗųś .řŬŔũŧƅŔŚţśƌƆƔƂŝƅŔƉŧŕŸƈƆƅ

-:řƔŬƔœũŖŔƏŗŔ řŝƜŝƑƅŔŕƎƆƈŠƈƓžřƅŕŬũƅŔƇŬƂƊśƏ

:¾ƍƕŒŔœŕƃŒ

řųŗśũƈƅŔƏĻŕŝƔŧţŘũƏŮƊƈƅŔŜƏţŗƅŔƇŲśřƈŧƂƈűũŷƇśřƔžƏ :ŜƔţƉƈřƅŕŬũƅŔŘŨƎƅřƔƈƆŸƅŔřƔſƆŦƅŔ¿ŝƈśƓśƅŔƏ řƅŕŬũƅŔŵƏŲƏƈŗ ŖƏƔŷƏ ŚŔŪƔƈƈ ŔŨƄƏ ŕƎśŠƅŕŸƈƑžřƈŧŦśŬƈƅŔƀũųƅŔƏ ƋŕƔƈƅŔŜƏƆś řƔŮŻƗŔ řƔƆƈŷƏ ŪŔŪśƈƗŔ řƔƆƈŷ Ɖƈ ĻƜƄ ƑƆŷ ŪƔƄũśƅŔ žƀũųƅŔ ŘŨƍ ŘũŝŎƈƅŔ ¿ƈŔƏŸƅŔƏ ŪŔŪśƈƗŔ ŚŕƔƆƈŷ ŵŔƏƊŔ ũƄŨŗ řƆœŕŬƅŔ řŗƆţśŬƈƅŔ ƉƏŗũƄƆƅƓƈŕŬƈƅŔŖƔƄũśƅŔžƋũƔŲţś ƀũųƏųŮƊƈƅŔƉƏŗũƄƅŔ žŕƎƔƆŷ

˺ Arabic Summary

ƉƏŗũƄƅŕŗ řŰŕŦƅŔ řƔųŕŮƊƅŔ ŧƔŧţś Ɠž řƈŧŦśŬƈƅŔ ƀũųƅŔƏ žųŮƊƈƅŔ ƇƔŧƂś ƇśƏ řƆœŕŬƅŔ řƔŮŻƗŔ ŵŔƏƊŔ ũƄŨ Ƈś ƃƅŨƄ žŘŪŕƈ ŘŧŕƈƄ ųŮƊƈƅŔ ʼnŕŮżƅŔũƔŲţś řƂƔũų žřƆœŕŬƅŔ řŗƆţśŬƈƅŔ řƔŮŻƗŔ řƔƆƈŸƅ Ƈŕŷ ŽŰƏ ƓƅŔ řžŕŲƗŕŗ ŔŨƍ .řƔƆƈŸƅŔ ŘŨƍ ƓƆŷ ŘũŝŎƈƅŔ ¿ƈŔƏŸƅŔ žŖƆţśŬƈƅŔ .řƆœŕŬƅŔřŗƆţśŬƈƅŔřƔŮŻƗŔ¿ŕŠƈƓžŕƍũŮƊ ƇśƓśƅŔŚŕŬŔũŧƅŔ

:ƑƈœśƃŒ ŔœŕƃŒ

ƀũųƅŔƏŧŔƏƈƅŔŵŔƏƊŔŜƔţƉƈřŬŔũŧƅŔƋŨƎƅƓƆƈŸƅŔŖƊŕŠƅŔ¿ŝƈƔƏ ƉƏŗũƄƅŔ Ɖƈ řſƆśŦƈ ƌƊƔŷ ÐÑ ũƔŲţś ƀũų ¿ƈŮś ƓśƅŔƏ řƈŧŦśŬƈƅŔ řƔœŕƔŪƔž ũƔŲţś ƀũųŗ ŚŕƊŔƏƔţƅŔ ƇŕŴŷ Ƈţž Řŧŕƈ ƇŔŧŦśŬŕŗ ųŮƊƈƅŔ řſƆśŦƈřƔœŕƔƈƄƀũųƏ (ƉƔŠƏũśƔƊƅŔŪŕŻƇŔŧŦśŬŕŗƏŌʼnŕƈƅŔũŕŦŗƇŔŧŦśŬŕŗ) ¿ƏƆţƈƏƃƔũƏſŬƏſƅŔƏƃśƔũŗƄƅŔƏƃƔũśƔƊƅŔƏƃƔũƏƆƄƏũŧƔƎƅŔűƈţƇŔŧŦśŬōŗ šƏŔũśś ŘũŔũţŚŕŠũŧŧƊŷ ƇƏƔŧƏŰƅŔŧƔŬƄƏũŧƔƍƏƇƏƔŬŕśƏŗƅŔŧƔŬƄƏũŧƔƍ ŧƏŧŚŕśƔũŗƄ ¿ŝƈ řƔƏŲŸƅŔ ŧŔƏƈƅŔűŸŗƇŔŧŦśŬŔƏ ÎƇ ×ÎÎ-ÓÎÎƉƔŗ ŘŧƔŧŠƋŪŕƈŧŔƏƈƓƆŷ¿ƏŰţƅŔŽŧƎŗƃƅŨƏ .(SDS)ƇƏƔŧƏŰƅŔ¿ƔŬ řƔœŕƔƈƔƄƏŪƔſƅŔ ůŔƏŦƅŔ ŧƔŧţś Ə .řſƆśŦƈ řƔœŕƔƈƔƄƏ řƔœŕƔŪƔž ůŔƏŦ ŕƎƅ řƔƈŠţƅŔ řžŕŝƄƅŔ žƇŕŬƈƅŔ ƇŠţ žŢųŬƅŔ řţŕŬƈ :¿ŝƈ ųŮƊƈƅŔ ƉƏŗũƄƆƅ ůŕŰśƈƗŔŽƔųžƓƊƔŠƏũŧƔƎƅŔūƗŔžřŗƏųũƅŔřŗŬƊžřƔũƍŕŴƅŔřžŕŝƄƅŔƏ řżŗŰ řƅŔŪŔ řƔƆƈŷ ƇŔŧŦśŬōŗ řƔŪŔŪśƈƛŔ řśũŧƁ žʼnŔũƈţƅŔ Śţś řŸŮƗŕŗ ũŕŗśŦŔƇśƏ .řśŗŕŝřƔųƈƊŽƏũŴŚţśřƔœŕƈƅŔ¿ƔƅŕţƈƅŔƉƈƀũŪƗŔƉƔƆƔŝƈƅŔ Ɖƈ ůƆŦśƅŔ Ɠž ƋŪŕƈ ŧŔƏƈƄ ŘũŲţƈƅŔ ƌųŮƊƈƅŔ ƉƏŗũƄƅŔ ŚŕƊƔŷ ŘʼnŕſƄ ƏŚƆŗƏƄƅŔƏůŕŰũƅŔ)řƆƔƂŝƅŔƉŧŕŸƈƅŔ űŸŗ¿ŝƈřƆœŕŬƅŔŚŕƔŕſƊƅŔűŸŗ

˻ Arabic Summary

(acid red 73 &acid blue )ŚŕżŗŰƅŔűŸŗŪŔŪśƈŔƏ (ƇƏƔŮƊŔũśŬƗŔ ƑƆŷũŝŎśƓśƅŔ¿ƈŔƏŸƅŔűŸŗřŬŔũŧƇśƏ .řŝƏƆƈƅŔřƔœŕƈƅŔ¿ƔƅŕţƈƅŔƉƈ 74 ŪƔƄũśũƔŝōśƏŪŔŪśƈƗŔřƔƆƈŷƇŕƈśƗƇŪƜƅŔƉƈŪƅŔ ¿ŝƈŪŔŪśƈƛŔŘũƍŕŴ řŠũŧ ũƔŝōśƏ ŪŔŪśƈƗŔ ŚŕƔƊţƊƈ ƉƔŸś Ƈś ŕƈƄ .ŘŪśƈƈƅŔ Ə ŘŪŕƈƅŔ ŘŧŕƈƅŔ ʼnŕŮżƅŔũƔŲţśƇś ,řƆœŕŬƅŔřŗƆţśŬƈƅŔřƔŮŻƗŔřƔƆƈŸƅřŗŬƊƅŕŗŕƈŔ .ŘũŔũţƅŔ ŚŕŗƔŨƈƅŔűŸŗƏ (Cyanex 301) ŘŧŕƈƇŔŧŦśŬŕŗ¿œŕŬƅŔ ŖƆţśŬƈƅŔ ƉŕśƔŗũƏŬŘŧŕƈ¿ŝƈŖƜţśŬƗŔƑƆŷŧŷŕŬśƓśƅŔŧŔƏƈƅŔ űŸŗƏřƔƏŲŸƅŔ žřƆƔƂŝƅŔ ũŰŕƊŸƆƅ ¿ŕŝƈƄ ŚƆŗƏƄƅŔ ŚŕƊƏƔŔ řƅŔŪŔ Ƒž ƇŧŦśŬŔƏ ŚŕƔƅƏƊƏƈ .¿œŕŬƅŔŖƆţśŬƈƅŔʼnŕŮżƅŔŚŕŗŝřŠũŧƑƆŷũŝŎśƑśƅŔ¿ƈŔƏŸƅŔ :ŚƃœśƃŒŔœŕƃŒ

ƋŨƍƉƈ ŕƎƔƆŷ¿ƏŰţƅŔƇśƓśƅŔşœŕśƊƅŔ ƑƆŷ¿ƈśŮŔ ŧƁƏ .¿ŕŠƈƅŔŔŨƍƓžřƂŗŕŬƅŔŜƏţŗƅŕŗřƊŕŸśŬƗŕŗŕƎśŮƁŕƊƈƏřŬŔũŧƅŔ ʼnŔŪŠŔřŝƜŝƓƅŏŖŕŗƅŔŔŨƍƇƔŬƂśƇśŧƁƏ

:¾ƍƕŒŇŨŞƃŒ ųŮƊƈƅŔ ƉƏŗũƄƅŔ ŚŕƊƔŷ ŽƔŰƏś şœŕśƊ řŮƁŕƊƈŗ ůśŦƔƏ ƋŨƍƇŴŸƈ ƉŔŢŲśŔ ŜƔţ ŚŕƊŔƏƔţƅŔƇŕŴŷ Ƈţž Ɖƈ ŘũŲţƈƅŔ ƓƆŷ ƒƏśţś ŕƎƊŔƏ řƔƅŕŷ řƔũƍŕŴƏ řƔƈŠţ řžŕŝƄŗŪƔƈśśŧŔƏƈƅŔ ŧŔƏƈƅŔƋŨƍƏÆŕŗƔũƂś % ×Ð-ÕÎƉƔŗšƏŔũśśŧŕƈũƅŔƉƈřƔƅŕŷřŗŬƊ ŚŕƊƔŸƅŔƓžřŗƏųũƅŔřŗŬƊƉŔŢŲśŔŕƈƄ žřƔƅŕŷřƔŪŔŪśƈŔŘũŧƂŗŪƔƈśś

˼ Arabic Summary

řƆƔŬƏƏŘũŔũţƅŔřŠũŧƅĻŕŸŗś % ÏÎ-ÑÓƉƔŗšƏŔũśś ŕƎųƔŮƊśƇśƓśƅŔ ũƔŧƂśƅŚŕƊƔŸƅŔ¿ƄƅƉƔŠƏũśƔƊƅŔŪŕŻŪŔŪśƈŔşœŕśƊ¿ƔƆţśƇśŕƈƄ .ųƔŮƊśƅŔ řƂƔƁŧƅŔ řƔƈŕŬƈƅŔ) ƇŕŬƈƆƅ ƓƆƄƅŔ ƇŠţƅŔƏ ŢųŬƆƅ řƔŷƏƊƅŔ řţŕŬƈƅŔ ŘŧŕƔŪ ƉŔ ĻŕƔœŕƔŪƔž ƌŠƅŕŸƈƅŔ ŚŕƊƔŸƆƅ ƌŗŬƊƅŕŗ ƌƊŔ ƉƔŗś ŕƎƊƈƏ (řųŬƏśƈƅŔƏ ÎƇ ÓÎÎ řŠũŧŧƊŷƌųŮƊƈŘŧŕƈƄƉƔŠƏũśƔƊƅŔƇŔŧŦśŬŔƏųƔŮƊśƅŔƉƈŪ řƂƔƁŧƅŔ řƔƈŕŬƈƅŔ řŗŬƊ ŘŧŕƔŪ, ŢųŬƅŔ řţŕŬƈ ŘŧŕƔŪ ƓƅŔ ƒŧŎś ŚŕśƔũŗƄŘŧŕƈřųŬŔƏŗĻŕƔœŕƔƈƔƄřŠƅŕŸƈƅŔŚŕƊƔŸƆƅřŗŬƊƅŕŗŕƈŔž(řƔƊƏũƄƔƈƅŔ) ƋũŲţƈƅŔ ŚŕƊƔŸƅŔ Ɖƈ ƓƆŷŔ ŢųŬ řţŕŬƈ ŕƎƅ ƇƏƔŧƏŰƅŔ ¿ƔŬƔ ŧƏŧ ƌƔƈŕŬƈƅŔƏƌƔƊƏũƄƔƈƅŔƌƔƈŕŬƈƅŔŕƎƔžŧƔŪśƏƇƏƔŬŕśƏŗƅŔŧƔŬƄƏũŧƔƍřųŬŔƏŗ .ƌųŬƏśƈƅŔ

¿ƄŮŕƎƅƇŕŬƈƅŔƉŔŢŬŕƈƅŔƓƊƏũśƄƅƗŔŖƏƄŬƏũƄƔƈƅŔƉƈƉƔŗśƔƏ ŽƔųşœŕśƊŚţŲƏŔƏ .ŕƔŔƏŪ¿ƄŮƓƆŷŚŔʼnƏśƊŧƏŠƏŶƈƇŴśƊƈũƔŻ řžŕŲƗŕŗŚŕƊƏŗũƄƅŔƏŚŕſŬƏſƅŔŚŕŷƏƈŠƈŧƏŠƏ ʼnŔũƈţƅŔŚţśřŸŮƗŔ ŧŔƏƈƆƅƓƊƔŠƏũŧƔƎƅŔūƗŔƇƔƁ ŚţŲƏŔ .¿ƔŬƄƏũŧƔƎƅŔŚŕŷƏƈŠƈƓƅŔ ƉƏŗũƄƅŔŵŔƏƊŔƇŴŸƈƉōŮŕƎƊōŮŽƔŸŲƒƏƆƁ ũƔŝōśŕƎƅƉŔƋũŲţƈƅŔ ŕƍũƔŲţśƇśƓśƅŔŚŕƊƔŸƅŔŘũŧƁƉŔƉƔŗśŕƈƄ .ĻŕƔũ੶řžƏũŸƈƅŔųŮƊƈƅŔ ŢųŬƅ řƔƈŕŬƈƅŔ ůœŕŰŦƅŔ ƓƆŷ ŧƈśŸś ƉƔƆƔŝƈƅŔ řżŗŰ ŪŔŪśƈŔ ƓƆŷ ŚŕƊƏƄƈƅŔ ƉŔ ŚŕƊƔŸƆƅ ƒũŰŕƊŸƅŔ ¿ƔƆţśƅŔ Ɖƈ ƉƔŗśƔƏ .ŘŪŕƈƅŔ ŘŧŕƈƅŔ -ÓÕ× ƉƔŗ šƏŔũśś ƉƏŗũƄƅŔ řŗŬƊ :Ɠƍ ųŮƊƈƅŔ ƉƏŗũƄƆƅ řƔŬŕŬƗŔ ƉƔŠŬƄƗŔřŗŬƊšŔƏũśśƉƄƅ %ÏÕ×-ÎÓ×ƉƔŠƏũŧƔƎƅŔƏ %ÏÒÒ× %ÎÖƓƅŔ¿ŰśřƆƔœųřŗŬƊŗŧŠƏƔřƊŕžƉƔŠƏũśƊƅŔƏ %ÐÏÎÔ-Î×

˽ Arabic Summary

¿ƈŕŸƄ ƉƔŠƏũśƔƊƅŔ ƇŔŧŦśŬŕŗ ŕƔœŕƔŪƔž ŕƎśŠƅŕŸƈ Ƈś ƓśƅŔ řƊƔŸƅŔ Ɠž ųƂž .ųƂž ÎƇ ÓÎÎŘũŔũţřŠũŧŧƊŷųŮƊƈ

:ƑƈœśƃŒŇŨŞƃŒ

ųŮƊƈƅŔ ƉƏŗũƄƅŔ ŚŕƊƔŷ űŸŗ ƇŔŧŦśŬŔ ƓƆŷ ŚŕƂƔŗųś ƌƔžƏ ¿ŝƈƌƆƔƂŝƅŔũŰŕƊŸƅŔűŸŗřƅŔŪŏƓžŚŕƊŔƏƔţƅŔƇŕŴŷƇţžƉƈũŲţƈƅŔ ŚŕżŗŰƅŔ űŸŗ řŠƅŕŸƈ ƃƅŨƄƏ ƇƏƔŮƊŔũśŮƗŔƏ ŚƆŗƏƄƅŔƏ ůŕŰũƅŔ ŜƔţřƔœŕƈƅŔ¿ƔƅŕţƈƅŔƉƈ acid blue 74Ə acid red 73¿ŝƈřƔƏŲŸƅŔ ¿ƔŬ ŧƏŧ ŚŕśƔũŗƄ Řŧŕƈ ƇŔŧŦśŬŕŗ ōƔœŕƈƔƄ ųŮƊƈƅŔ ƉƏŗũƄƆƅ ƉŔ Śŗŝ ŪŔŪśƈŔƓžƃƅŨƄƏ ůŕŰũƅŔ ŪŔŪśƈŔƓžřƔƅŕŷŘũŧƂŗŪƔƈśƔ ƇƏƔŧƏŰƅŔ ųŮƊƈƅŔƉƏŗũƄƅŔŕƈŔ (acid red 73 &acid blue 74)ƉƈŘũƔŗƄřƔƈƄ ŪƔƈśƔž ƉƔśŷŕŬ Řŧƈƅ ÎƇ ÕÓÎ řŠũŧ ŧƊŷ ʼnŕƈƅŔ ũŕŦŗ ƇŔŧŦśŬŕŗ ōƔœŕƔŪƔž ųŮƊƈƅŔ ƉƏŗũƄƅŔ ƉƄƅƏ ž ŚƆŗƏƄƅŔ Ɖƈ řƔƅŕŷ řƔƈƄ ŪŔŪśƈŔ ƑƆŷ řśũŧƂŗ Śŗŝ ÎƇ ÓÎÎŘũŔũţřŠũŧŧƊŷƉƔśŷŕŬŘŧƈƅƉƔŠƏũśƔƊƅŔƇŔŧŦśŬŕŗĻŕƔœŕƔŪƔž Ƈś ƃƅŨƅ . ƇƏƔŮƊŔũśŬƗŔ Ɖƈ ŘũƔŗƄ řƔƈƄ ŪŔŪśƈŔ Ɠž řƔƅŕŷ ŘʼnŕſƄ ƌƅ ƉŔ ŧƁƏ .ƇŕŴƊ¿ƄƓžŘũŝŎƈƅŔ¿ƈŔƏŸƅŔřŬŔũŧƅƋŪŕƈŧŔƏƈƄŧŔƏƈƅŔƃƆśũŕƔśŦŔ :ƓƅŕśƅŔƏţƊƅŔƓƆŷŪŔŪśƈƘƅƌƈŴƊŔ ÓřŬŔũŧƇś

BC-SDS-2105: Pb, BC-S-2750 : Co, BC-N2-2500 : Sr, BC-SDS-2105: acid red 73 and BC-SDS-2105: acid blue 74

ƏƇƏƔŮƊŔũśŬƗŔƏŚƆŗƏƄƅŔƏůŕŰũƅŔŪŔŪśƈŔƃƏƆŬřŬŔũŧŗƏ ŧŔŧŪ»ƔŪŔŪ»śƈƗŔ¿ŧŸƈƉŔŧŠƏ acid blue 74 Ə acid red 73 ƌ»ŠƏƓ»Ɔŷ řƔƄƔƈŕƊƔŧƅŔřŬŔũŧƅŔŚţŲƏŔŕƈƄ . ŪŔŪśƈƗŔƉƈŪŘŧŕƔŪŗ

˾ Arabic Summary

Ə»ƍũ»ŰŕƊŸƅŔŪŔŪśƈƕƉŔŪśƗŔřƅŕţŜƏŧţƅƇŪƜƅŔƉƈŪƅŔƉŔƇƏƈŸƅŔ ÏÐÎ) ƇƏƔŮ»ƊŔũśŬƗŔƏ (řƂƔƁŧ ÔÎ) ŚƆŗƏƄƅŔƏ (řƂƔƁŧ ÏÐÎ) ůŕŰũƅŔ ÒÖ) ƏƍƉŔŪśƗŔřƅŕţƅƇŪƜƅŔƉƈŪƅŔƉྦŕżŗŰƆƅřŗŬƊƅŕŗŕƈŔ (řƂƔƁŧ :ƓśƕŔŧŠƏŪŔŪśƈƗŔ¿ŧŸƈƓƆŷŘũŝŎƈƅŔ¿ƈŔƏŸƅŔřŬŔũŧŗƏ .(řŷŕŬ

ŶŗśƔ acid red 73 , acid blue 74ƏŚƆŗƏƄƅŔƏůŕŰũƅŔŪŔŪśƈŔ - ŕ»ƈŔŚŕŝƏƆƈƅŔƋŨƎƅƓœŕƔƈƔƄƅŔŪŔŪśƈƗŔƓƆŷ¿ŧƔŕƈƈřƔƊŕŝƅŔřŗśũƈƅŔ .ƓƅƏƗŔřŗśũƈƅŔŶŗśƔƇƏƔŮƊŔũśŬƗŔŪŔŪśƈŔ Ó-Ð ƓƊƔŠƏũŧ»ƔƎƅŔūƗŔƒŧ»ƈ ŧ»Ɗŷůŕ»ŰũƆƅŪŔŪśƈŔ¿ŲžŔ - , Ö-Ð ƏƍƇƏƔŮƊŔũśŬƘƅřŗŬƊƅŕŗƒŧƈ¿ŲžŔƉƄƅ Ô-Ð ŚƆŗƏƄƆƅƏ .ÑƓƊƔŠƏũŧƔƎƅŔūƗŔŧƊŷ řŬŔũŧƅŔ¿ţƈŚŕżŗŰƆƅŪŔŪśƈŔƓŰƁŔ ƉŔ ŧŠƏŜƔţŘŪśƈƈƅŔřƔƈƄƅŔƓƆŷŴƏţƆƈũƔŝōśŕƎƅŘũŔũţƅŔřŠũŧ - ůŕŰũƅŔřƅŕţƓžŘũŔũţƅŔřŠũŧŘŧŕƔŪŗŧŔŧŪśŘŪśƈƈƅŔŘŧŕƈƅŔřƔƈƄ acid ř»ƅŕţƓžŕƈŔ acid blue 74ƏƇƏƔŮƊŔũśŬƗŔƏŚƆŗƏƄƅŔƏ ¿»ƈŔƏŸƅŔř»ƈƔƁŖŕŬ»ţƇ»śƓƅໜƅŕŗƏūƄŸƅŔŜŧţƔ red 73 0 0 0 ( ѐ H , ѐG , and ѐS )řƔũŔũţƅŔřƔƄƔƈŕƊƔŧƅŔ

:ŚƃœśƃŒŇŨŞƃŒ ŖƆţśŬƈƅŔ ʼnŕŮżƅŔ ƇŔŧŦśŬōŗ ŚƆŗƏƄƅŔ ŚŕƊƏƔŔ řƅŔŪŔ Ƈś řƔž Ə ʼnŕŮżƅŔũƔŲţśƇśƏ .řŬŔũŧƅŔŚţśƓśƅŔřƆƔƂŝƅŔũŰŕƊŸƆƅ¿ŕŝƈƄ¿œŕŬƅŔ ŚŕŗƔŨƈƅŔ űŸŗƏ (Cyanex 301)  ƇŔŧŦśŬŕŗ ¿œŕŬƅŔ ŖƆţśŬƈƅŔ Řŧŕƈ ¿ŝƈ ŖƜţśŬƗŔ ƑƆŷ ŧŷŕŬś ƓśƅŔ ŧŔƏƈƅŔ  űŸŗƏ řƔƏŲŸƅŔ ƓƆŷũŝŎśƑśƅŔ¿ƈŔƏŸƅŔƓƆŷşœŕśƊƅŔŚƆƈśŮŔŧƁƏ .ŚŕƔƅƏƊƏƈƉŕśƔŗũƏŬ

˿ Arabic Summary

űƈţ ŪƔƄũśƏ ŖƔŨƈƅŔ ŵƏƊ ¿ŝƈ ŚƆŗƏƄƅŔ ŚŕƊƏƔŔ ůƜŦśŬŔ řƔƆƈŷ ƉŔ ŧŠƏ ŧƁ Ə ůƜŦśŬƗŔ řƔƆƈŷ řƔž Ƈśś ƒŨƅŔ ųŬƏƅŔ Ɠž ƃƔũśƔƊƅŔ ĻŔũƏŧŖŸƆś ůƜŦśŬƗŔřƔƆƈŷřƔžƇśśƐŨƅŔųŬƏƆƅřŲƏƈţƅŔřŠũŧ şœŕśƊƅŔ ŔŨƄ Ə .¿ƏƆţƈƅŔ Ɖƈ ŚƆŗƏƄƅŔ ŚŕƊƏƔŔ řƅŔŪŏ řƔƆƈŷ Ƒž ÆĻŕƈŕƍ ŖƆţśŬƈƅŔʼnŕŮżƅŔŚŕŗŝřŠũŧƑƆŷũŝŎśƑśƅŔ¿ƈŔƏŸƅŔ řŬŔũŧŗřŰŕŦƅŔ řŷũŬƏ ŖƜţśŬƗŔ ƓƆŷ ŘŧŷŕŬƈƅŔ ŘŧŕƈƅŔ ŪƔƄũśƏ ŵƏƊ ¿ŝƈ ¿œŕŬƅŔ Řŧŕƈ ŪƔƄũś Ə ůƜŦśŬƗŔ řƔƆƈŷ ʼnŕƊŝŔ ŪŔŪśƍƗŔ řŷũŬƏ ŖƜţśŬƗŔ (Cyanex 301)

Ɖƈ şśŕƊƅŔ Ə ŚŕƊŔƏƔţƅŔ  ƇŕŴŷ Ƈţž ƉŔ  ƓƅŔ řŬŔũŧƅŔ ŚŰƆŦ ƓƅŔřƆƔƏţśƉƄƈƔ -řœƔŗƅŔƑƆŷƓŗƆŬũŝŔƌƅŖƆŰ ŽƆŦƈƄŚŕƔƏŗƅŔŶƊŕŰƈ ŘŪƔƈśƈ ůœŕŰŦ ŚŔŨ ŘŪŕƈ ŧŔƏƈƄ ¿ƈŸś ųŮƊƈƅŔ ƉƏŗũƄƅŔ Ɖƈ ŵŔƏƊŔ Ɖƈ ¿Ƅ ƑƆŷ řƔƏśţƈƅŔ ƋŕƔƈƅŔ řŠƅŕŸƈ ŚŕƔƆƈŷ Ɠž ƇŔŧŦśŬƘƅ ŕƎƆƍŎś řƅƏƎŬ Ɖƈ ƇŻũƅŕŗ řƊŔ ŢŲśŏ ŕƈƄ .řƔƏŲŷ ũƔżƅŔƏ řƔƏŲŸƅŔ  ŚŕŝƏƆƈƅŔ ŖŗŬŗƃƅŨƏũŕŮśƊƗŔřŸŬŔƏũƔŻŕƎƊŏƛŏ¿œŕŬƅŔŖƆţśŬƈƅŔʼnŕŮżƅŔřƔƊƂś .ŖƆţśŬƈƅŔŶƔƈŠśƏŤŕſśƊŔ ž¿œŕŬƅŔʼnŕŮżƆƅ ƓžŕƄƅŔŚŕŗŝƅŔƇŧŷ

̀ Ain shams University Faculty of Science Chemistry Department

" UTILIZATION OF ADSORPTION AND/OR LIQUID MEMBRANES TECHNIQUES IN TREATMENT OF SOME HAZARDOUS SUBSTANCES" Thesis Presented By Lamyaa Mohamed Soliman Hussin M.Sc. Chemistry, 2004 Submitted To Chemistry Department, Faculty of Science Ain shams University For the Degree of Ph.D. of Science in Chemistry Supervised By

Prof. Dr. Prof. Dr. Salah A. Abo-El-Enein Abd El-Hakim Abd Allah Mohamed Prof. of Physi. Chem., Prof. of Appl. Chem., Faculty of Science Hot Labs. Center Ain shams University Atomic Energy Authority Dr. Dr. Yasser Tawfik Mohamed Hamdi Mohamed Hasan Gad Ass. Prof. of Raies Chem., Ass. Prof. of Appl. and Physi. Chem., Hot Labs. Center Hot Labs. Center Atomic Energy Authority Atomic Energy Authority 2011 ¨ IInnttrroodduuccttiioonn ¨ EExxppeerriimmeennttaall ¨

RReessuullttss aanndd DDiissccuussssiioonn ¨ SSuummmmaarryy ¨

RReeffeerreenncceess ¨

AArraabbiicc SSuummmmaarryy Acknowledgments

First and foremost thanks to ALLAH the most merciful

I would like to express my deep thanks and gratefulness to Prof. Dr. Salah A. Abo-El-Enein Prof. of Physical Chemistry, and Building Materials, Faculty of Science, Ain Shams University, for supervision and sincere assistance guidance during this study.

Thanks to Prof. Dr. Abd El-Hakim Abd Allah Mohamed Prof. of Applied Chemistry, Hot Laboratories., Center Atomic Energy Authority, for suggesting the point of research, planning cooperation and intelligent observation.

Thanks to Dr. Yasser Tawfik Mohamed and Dr. Hamdy Mohamed Hasan Gad, Hot Laboratories. Center Atomic Energy Authority, for their kind and helpful advice.

I highly acknowledge and deep thanks to my husband, my children and all my family. Lamyaa Soliman ï¶ï¶áÀAáYãIâk @Éð¸Aï° áÀA áY ãI âk @ É ð¸ A ï° AAáÁï¸ á¾ñ¹ç¤ ïÙ áÁ ï¸ á¾ ñ¹ ç¤ ïÙ AA áÁ áÁ áM áM ã½ ã½ ÷¹ ÷¹ ᤠᤠA A á¼ á¼ ÷Ù ÷ÙõF õF áNáN À À ïB ïB ï¶ ï¶ éÀ éÀ õF õF â¾ËçµáYñ¸@ â¾Ëç¹á¥ñ¸@â¾ËçµáYñ¸@ â¾Ëç¹á¥ñ¸@

¾Ë¡¥¸@ @ ³ds ''21(( ÏÊÝ@ ÏÊÝ@ Îh±I¸@ ÎgÉk ''ÏËÀd¼(( m ’¤ Ï¥¼AT ÒA˽˵¸@ ¾l° - ¿É¹¥¸@ Ï˹´ τA¥¼  ϹÓAl¸@ ÏËp¨Û@'È@ ( È i@jM¼Û@ ÏËÁ±L ¿@daMk@! !ÎgAx¸@ c@ɛ@ z¥H ¼ ϼd±¼ ϸAkg ’lX ÃA½Ë¹k d½ˆ ÒA˛ ϡ ˻˹˹˽ - Δϴ΋Ύϳΰϴϓ ˯ΎϴϤϴϛ - ˯ΎϴϤϴϜϟ΍ ϰϓ ϡϮϠόϟ΍ ϲϓήϴΘδϴΟΎϣ ̸@ βϤη Ϧϴϋ ΔόϣΎΟ – ϡϮϠόϟ΍ ΔϴϠϛ - ˯ΎϴϤϴϜϟ΍ Ϣδϗ ˯ΎϴϤϴϜϟ΍ ϲϓ ϡϮϠόϟ΍ ϲϓ ΔϔδϠϔϟ΍ Γ΍έϮΘϛΩ ΔΟέΩ ϲϠϋ ϝϮμΤϠϟ ¯@hoF N‚ @ ®Ëw d½ˆ @ dI¤ ¾Ëµ @ dI¤ c-@ ’ÁË¥¸@ ÉH@ ©¸@ dI¤ _Ús - c-@ ΔϴϘϴΒτΘϟ΍ ˯ΎϴϤϴϜϟ΍ ΫΎΘγ΍ ˯ΎϨΒϟ΍ Ω΍Ϯϣϭ Δϴ΋Ύϳΰϴϔϟ΍ ˯ΎϴϤϴϜϟ΍ ΫΎΘγ΍ ΓέΎΤϟ΍ ϞϣΎόϤϟ΍ ΰϛήϣ ˯ΎϴϤϴϜϟ΍ ϢδϘΑ Δϳέάϟ΍ ΔϗΎτϟ΍ ΔΌϴϫ βϤη Ϧϴϋ ΔόϣΎΟ -ϡϮϠόϟ΍ ΔϴϠϛ cAT ÂlX d½ˆ Íd™ -c ¾Ë¹k d½ˆ ²Ë¬ÉL hkAÊ-c ΔϴϘϴΒτΘϟ΍ ϭ Δϴ΋Ύϳΰϴϔϟ΍ ˯ΎϴϤϴϜϟ΍ ΪϋΎδϣ ΫΎΘγ΍ ΔϴϋΎόηϷ΍ ˯ΎϴϤϴϜϟ΍ ΪϋΎδϣΫΎΘγ΍ ΓέΎΤϟ΍ ϞϣΎόϤϟ΍ ΰϛήϣ ΓέΎΤϟ΍ ϞϣΎόϤϟ΍ ΰϛήϣ Δϳέάϟ΍ ΔϗΎτϟ΍ ΔΌϴϫ Δϳέάϟ΍ ΔϗΎτϟ΍ ΔΌϴϫ 1/00, ÎhÄA±¸@ LIST OF CONTENTS

Title Page No. CHAPTER 1: INTRODUCTION and OBJECT OF INVESTIGATION CHAPTER I A. INTRODUCTION...... 1 IA .1 ADSORPTION TECHNIQUE...... 4 I A.1.1. Exchange Adsorption...... 4 I A.1.2. Physical Adsorption (Ideal Adsorption)...... 5 I A.1.3. Chemical Adsorption...... 5 I A.1.4. Main Factors Influence The Adsorption Process...... 6 I A.1.5 Activated Carbon...... 11 IA.1.6 Literature Survey on Adsorption Using Animal Bone Char ...... 19 I A.2 LIQUID MEMBRANE TECHNIQUE...... 29 I A.2.1. Bulk Liquid Membrane (BLM) ...... 29 I A.2.2. Supported Liquid Membrane (SLM)...... 29 I A.2.3. Liquid Emulsion Membrane (LEM) ...... 30 I A.2.3.4 Literature survey on the liquid emulsion membrane in treatment of some hazardous substances produced from industrial wastewater ...... 39

I B. OBJECT OF INVESTIGATION ...... 49

CHAPTER II: EXPERIMENTAL II A. ADSORPTION TECHNIQUE...... 51 II A.1 The Precursor...... 51 II A.2 Chemical Composition of the Precursor ...... 52 II A.3 Preparation of Activated Carbons...... 53 II A.4 Chemical and Reagents...... 59 II A.5 Methods...... 60

I LIST OF CONTENTS (Cont..)

Title Page No. II A.5.1 Charaterization of the prepared carbons ...... 60 II A.5.2. Sorption investigation ...... 65 II B. LIQUID EMULSION MEMBRANE TECHNIQUE...... 76 II B.1 Reagents ...... 76 II B.2. Procedure...... 76

CHAPTER III: RESULTS AND DISCUTION III A. ADSORPTION TECHNIQUIE ...... 79 III A.1 Characterization of the Used Carbons...... 79 III A.1.1 Physical characterization of selected activated carbons...... 79 III A.1.2 Chemical characterization of selected actived carbons...... 97 III A.1.3 Adsorption characterization conclusion ...... 107 III A.2 Lead, Cobalt and Strontium Removal ...... 109 III A.2.1 Activated carbon selection...... 111 III A.2.2 Adsorption kinetic studies ...... 112 III A.2.3 Effect of initial metals concentration ...... 122 III A.2.4 Equilibrium adsorption isotherm...... 124 III A.2.5 Effect of solution pH on metal adsorption...... 135 III A. 2.6 Mechanism of metal ions adsorption...... 139 III A.2.7 Thermodynamic evaluation of the adsorption process ...... 144 IIIA.2.8 Effect of carbon mass on metal ions adsorption...... 152 III A.3 Acid Red 73 and Acid Blue 74 Removal...... 153 III A.3.1 Kinetic studies of acid red 73and acid blue 74 adsorption...... 159 II LIST OF CONTENTS (Cont..)

Title Page No. III A.3.2 Effect of adsorbent mass...... 163 III A.3.3 Effect of adsorbate concentration...... 165 III A.3.4 Effect of solution pH ...... 166 III A.3.5 Mechanism of acid red 73 and acid blue 74 adsorption...... 168 III A.3.6 Equilibrium adsorption isotherm...... 169 III A.3.7 Thermodynamic studies...... 177 III B. Liquid emulsion membrane technique ...... 185 III B.1 Extraction of Cobalt from Wastewater Using Liquid Emulsion Membrane ...... 186 III B.1.1 Liquid –liquid extraction investigation ...... 187 III B.2 Permeation of Cobalt (II) Ions Using LEM...... 192 III B.2.1 Transport mecanism of cobalt(II) extraction process using LEM...... 193 III B.2.2 Emulsion stability...... 194 III B.2.3 Factors affecting the permeation process of cobalt by LEM ...... 203 III B.2.4 Extraction kinetics of Co (II) ions by LEM...... 208

SUMMARY ...... 211 REFERENCES ...... 219 ARABIC SUMMARY ...... –––

III LIST OF TABLES

Tab. No. Title Page No. Table (I.1): Current treatment technologies for heavy metals and dyes removal involving physical and/or chemical process...... 3 Table (II.1): Chemical analysis of BC used in this work ...... 52 Table (II.2): Different types of activated carbons from bone char ...... 58 Table (II.3): Chemical reagents used in this study...... 59 Table (II.4): Preliminary test for selection of activated carbon samples...... 70 Table (III.1): Apparent and bulk densities of activated carbons ...... 81 Table (III.2) Ash content of various activated carbons...... 82 Table (III.3): Moisture content of various activated carbons...... 84 Table (III.4): Characteristics of activated carbons calculated from BET model and t-plot ...... 90 Table (III.5): The measured pH values of the prepared cabons...... 101 Table (III.6): Results of methylene blue uptake of various carbon samples...... 104 Table (III.7): Relationship between methylene blue index and porous characterstics of carbon samples...... 105 Table (III.8): Elemental analysis for activated carbons...... 106 Table (III.9): Characteristic parameters of carbon samples derived from bone Char...... 109 Table (III.10): Preliminary tests for untreated and activated bone char...... 111 Table (III.11): Comparison of the pseudo first- and second- order sorption rate constants and the calculated and experimental qe values for Pb(II), Co(II) and Sr(II)...... 116

IV LIST OF TABLES (Cont…)

Tab. No. Title Page No. Table (III.12): Langmuir parameters for investigated metal ions...... 129 Table (III.13): Freundlich parameters for investigated metal ions...... 129 Table (III.14): D-R parameters of lead, cobalt and strontiun adsorption...... 133 Table ( III.15): Effect of isotherm shape...... 134 Table (III.16): Langmuir parameters for lead, cobalt, and strontium adsorption at different temperatures...... 145 Table (III.17): Thermodynamic parameters of lead, cobalt and strontium adsorption...... 150 Table (III.18): Comparison of the pseudo-first-order and second-order adsorption rate constants and the calculated and experimental qe values for acid red and acid blue dyes...... 159 Table (III.19): Langmuir, Freundlich, and Dubinin- Radushkevich parameters for adsorption of acid red 73 and acid blue 74 onto BC-SDS- 2105 sample at 25 0C...... 172 Table (III.20): Characteristic parameters of the experimental data according to the Langmuir, Freundlich and Dubinin-Radushkevich models for the adsorption of acid red 73 and acid blue 74 onto sample BC-SDS-2105 at different temperatures...... 181 Table (III.21): Thermodynamic Parameters of acid red 73 and acid blue 74 dsorption onto sample BC- SDS-2105 at different temperature...... 184 Table (III.22): Effect of diluent type on percent of extraction...... 187 Table (III.23): The Effect of different stripping agents on the stripping % of cobalt from Cyanex 301...... 189

V LIST OF FIGURES

Fig. No. Title Page No. Fig. (IA.1): Carbon Atom Arrangements in Graphite Crystal...... 15 Fig. (IA.2): Structures of carboxyl, phenolic hydroxyl and groups quinines carbonyl...... 17 Fig. (IA.3): Structures of carboxylic acid anhydrides and cyclic peroxide...... 18 Fig. (II.1): Schematic diagram of the system used for the preparation of Activated carbons from bone char ...... 55 Fig.(II.2): Calibration curve of methylene blue...... 65 Fig.(II.3): Calibration curve of lead by UV- spectrophotometeter...... 67 Fig.(II.4): Calibration curve of cobalt by UV- spectrophotometeter...... 68 Fig.(II.5): Calibration curve of strontium by atomic absorbance...... 69 Fig.(II.6): Calibration curve of acid red 73 UV- spectrophotometeter...... 73 Fig.(II.7): Calibration curve of acid blue74 UV- spectrophotometeter...... 73 Fig.(III.1): Nitrogen adsorption isotherms at 77 k for physical-activated carbons...... 87 Fig.(III.2): Nitrogen adsorption isotherms at 77 k for chemical-activated carbons...... 89 Fig.(III.3): Scanning electron microscopy of bone char without-activation ...... 92 Fig. (III.4): Scanning electron micrograph of the physical-activated carbons...... 94 Fig.(III.5): Scanning electron micrograph of the chemical-activated carbons...... 96

VI LIST OF FIGURES (Cont…)

Fig. No. Title Page No. Fig.(III.6): The FTIR spectrum of bone char without- activation ...... 97 Fig.(III.7): The FTIR spectra of the physical-activated bone char a) BC-S-1750; b) BC-S-2750; c) BC-N2-2500...... 98 Fig.(III.8): The FTIR spectra of the chemical-activated bone char a) BC-SDS-2105; b) BC-K70%- 1500 ...... 99 Fig.(III.9): Scatter graph of ash and pH of various carbon samples Fig.(III.10): Effect of time on adsorption of lead, cobalt and strontium Fig.(III.11): Pseudo-first-order sorption kinetics of Lead,Cobalt and Strontium ...... 102 Fig. (III.10): Effect of time on adsorption of lead, cobalt and strontium ...... 114 Fig. (III.11): Pseudo-first order sorption kinetics of lead, cobalt and strontium ...... 115 Fig.(III.12): Pseudo-second-order sorption kinetics of lead, cobalt and strontium ...... 116 Fig.(III.13): Intra-particle diffusion plots for adsorption of lead, cobalt and strontium...... 120 Fig.(III.14): Boyd plots of the kinetics for lead, cobalt and strontium sorption...... 122 Fig.(III.15): Influence of initial concentration of lead, cobalt, and strontium, on equilibrium uptake(qe) ...... 123 Fig.(III.16): Effect of initial concentration on sorption rate of lead, cobalt and strontium...... 124 Fig.(III.17): Equilibrium Adsorption Isotherms of Lead, Cobalt and Strontium...... 125 Fig.(III.18): Langmuir plots of Lead,Cobalt and Strontium sorption...... 127 Fig.(III.19): Freundlich plots of Lead, Cobalt and Strontium sorption...... 127

VII LIST OF FIGURES (Cont…)

Fig. No. Title Page No.

Fig.(III.20): D-R plots of Lead, Cobalt and Strontium adsorption...... 132 Fig. (III.21): Effect of pH on the adsorption of (a) lead (b) cobalt and (c)strontium...... 136 Fig. (III.22): The effect of temperature on lead sorption...... 146 Fig.(III.23): The effect of temperature on Cobalt sorption...... 146 Fig.(III.24): The effect of temperature on strontium sorption...... 147 Fig.(III.25): Langmuir plots of lead adsorption showing the effect of temperature ...... 147 Fig.(III.26): Langmuir plots of cobalt adsorption showing the effect of temperature...... 148 Fig.(III.27): Langmuir plots of strontium adsorption showing the effect of temperature...... 148 Fig.(III.28): Van't Hoff plots of lead, cobalt and strontium adsorption...... 150 Fig.(III.29): Effect of carbon mass on lead, cobalt and strontium sorption...... 152 Fig. (III.30): Structure of (Acid Red 73) ...... 155 Fig. (III.31): Structure of (Acid Blue 74) ...... 155 Fig.(III.32): Influence of agitation time on adsorption of acid red 73 and acid blue 74 ...... 157 Fig.(III.33): Pseudo-first-order sorption kinetics of acid red 73 and acid blue74...... 160 Fig.(III.34): Second-order sorption kinetics of acid red 73 and acid blue 74...... 160 Fig.(III.35): Intra-particle diffusion plots for acid red and acid blue 74 sorption...... 161

VIII LIST OF FIGURES (Cont…)

Fig. No. Title Page No. Fig.(III.36): Boyd plots of the kinetics for acid red 73 and acid blue 74 sorption...... 163 Fig.(III.37): Effect of carbon mass uptake and % of removal on acid red 73 and acid blue 74 sorption...... 164 Fig.(III.38): Influence of initial concentration on the equilibrium uptake (qe) of acid red 73 and acid blue 74 using sample BC-SDS-2105 ...... 166 Fig.(III.39): Effect of pH on the sorption of acid red 73 and acid blue 74 dyes by sample BS-SDS- 2105 ...... 168 Fig.(III.40): Equilibrium adsorption isotherms of acid red 73 and acid blue 74 onto sample BC- SDS-2105...... 171 Fig.(III.41): Langmuir plots of acid red 73 and acid blue 74 adsorption...... 174 Fig.(III.42): Freundlich plots of acid red 73 and acid blue 74 adsorption...... 175 Fig.(III.43): D-R plots for acid red 73 and acid blue 74 sorption onto sample BC-SDS-2105...... 176 Fig.(III.44): Temperature effect on acid red 73 adsorption onto BC-SDS-2105 carbon...... 179 Fig.(III.45): Temperature effect on acid blue 74 adsorption onto BC-SDS-2105 carbon...... 179 Fig.(III.46): Langmuir plots of acid red 73 adsorption on BC-SDS-2105 sample showing the effect of temperature...... 180 Fig.(III.47): Langmuir plots of acid blue 74 adsorption on BC-SDS-2105 showing the effect of temperature...... 180

IX LIST OF FIGURES (Cont…)

Fig. No. Title Page No. Fig (III.48): Vant's Hoff plots of acid red 73 and acid blue 74 sorption onto sample BC-SDS- 2105 ...... 183 Fig(III.49): Effect of nitric acid concentration on the percent of extration of cobalt by Cyanex 301 in cyclohexane...... 188 Fig.(III.50): Effect of HCl concentration on the stripping of Co(II) from Cyanex 301/cyclohexane solution: [Co(II)] = 100 ppm, Cyanex 301=4%(v/v), [HNO3] = 0.01 M ...... 190 Fig.(III.51): Effect of time on the extraction of cobalt by Cyanex 301 in cyclohexane from 0.01M nitrate medium: [Co(II)] = 100 ppm; [CYanex 301] =4%(v/v) T=25±1 0C...... 191 Fig.(III.52): Effect of carrier concentration on percenttage of Co(II) extraction...... 192 Fig.(III.53): Effect of type of surfactant on the leakage (%) of LEM in nitric acid medium ...... 196 Fig.(III.54): Effect of surfactant concentration on the leakage(%) of LEM in nitric acid medium...... 197 Fig.(III.55): Effect of emulsification speed on the stability of emulsion in nitrate medium...... 198 Fig.(III.56): Effect of stirring speed on the stability of LEM in nitrate medium...... 200 Fig.(III.57): Effect of stripping phase concentration on the stability of emulsion in nitrate medium...... 201 Fig.(III.58): Effect of volume ratio of organic phase to internal aquoues phase on the stability of emulsion in nitrate medium...... 202 Fig.(III.59): Effect of volume ratio of emulsion phase to external phase on the stability of the emulsion in nitrate medium...... 203

X LIST OF FIGURES (Cont…)

Fig. No. Title Page No.

Fig.(III.60): Effect of nitric acid concentration in the external phase on the % permeation of cobalt through LEM...... 205 Fig.(III.61): Effect of Cyanex 301 concentration in the membrane phase on the permeation, % of cobalt through LEM...... 206 Fig.(III.62): Effect of initial cobalt concentration in the feed phase on the peremeation, % of cobalt through LEM...... 207 Fig.(III.63): Effect of HCl (stripper) concentration in the internal aqoueous phase on the permeation % of Co(II) ions...... 208 Fig.(III.64): First order plots for permeation of cobalt from nitrate medium in cyclohexane; [Co(II)]=100 PPM; [Cyanex 301] = 6% (v/v); 0.01 HNO\-(3);[Hcl]= 3M; [Span 80]=4% (v/v);stirring speed=250 rpm; feed volume:emulsion volume=10:1...... 210

Fig.(III.65): Effect of [HNO3] [Cyanex 301] [Co(II)] and [HCl] Concentration on the rate of Co(II) ions permeation by Cyanex 301 in cyclohexane from nitrate medium through liquid emulsion membrane: [surfactant] = 4% (v/v); stirring speed 250 rpm; feed volume: emulsion volume = 10:1 ;T =25± 1 0C...... 210

XI