REMOVAL of TURBIDITY, LEAD and CADMIUM IONS from WASTEWATERS USING PRODUCTS DERIVED from Mangifera Indica KERNEL

REMOVAL OF TURBIDITY, LEAD AND CADMIUM IONS FROM WASTEWATERS USING PRODUCTS DERIVED FROM mangifera indica KERNEL

KARIUKI JOHN NJUGUNA I56/CE/22622/2011

A Thesis Submitted in Partial fulfillment of the Requirement for the Award of the Degree of Master of Science in Chemistry in the School of Pure and Applied Sciences of Kenyatta University

JUNE 2016

DECLARATION

This thesis is my original work and that it has not been presented for a degree in any university, or any other award.

Sign ……………………………….. Date …………………………………

Kariuki, John Njuguna I56/CE/22622/2011 Department of chemistry

Supervisors

We confirm that the work reported in this thesis was carried out by the candidate under our supervision

Sign ……………………………….. Date ……………………………….

Dr. Harun M. Mbuvi Department of Chemistry Kenyatta University

Sign ……………………………… Date …………………………………..

Dr. Margaret M. Nganga Department of Chemistry Kenyatta University

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Dedication

I dedicate this work to my beloved wife Jane Njuguna and my children Joseph

Kariuki, Naomi Njeri and Isaac Waweru.

Acknowledgement

First and foremost am grateful to Almighty God for enabling me to see the completion of this research work. My gratitude goes to my supervisors Dr. Harun Mbuvi and Dr.

Margaret Nganga for their unwavering input, encouragement, support, advice and guidance throughout the research period. May the Almighty God bless both of you abundantly in all aspects of your life.

I would also like to register my acknowledgement to lecturers and technical staff of department of chemistry, Kenyatta University. Am also indebted to my coursemates for your advice and encouragement throughout the course. My gratitude also goes to my colleagues at work and much more the principal, Mr. Zachary Njenga for the warm and conducive atmosphere during the course.

Finally am sincerely grateful to my beloved wife Jane Njuguna for prayers, support, encouragement, patience and understanding during the whole period of study.

TABLE OF CONTENTS DECLARATION ...... ii Dedication ...... iii Acknowledgement ...... iv TABLE OF CONTENTS ...... v List of tables ...... viii List of Figures ...... ix ABBREVIATIONS AND ACRONYMS ...... x ABSTRACT ...... xi CHAPTER ONE ...... 1 INTRODUCTION ...... 1 1.1 Background Information ...... 1 1.2 Statement of the problem ...... 3 1.3 Justification of the Study ...... 3 1.4 Hypothesis...... 4 1.5 General objective ...... 4 1.6 Specific objectives ...... 4 1.7 Significance of the Study ...... 5 CHAPTER TWO ...... 6 LITERATURE REVIEW ...... 6 2.1 Utilization of agricultural waste ...... 6 2.2 Water scarcity ...... 8 2.3 Water pollution ...... 8 2.5 Heavy metal toxicity ...... 9 2.6 Water treatment ...... 11 2.7 Methods used to remove water contaminants ...... 12 2.7.1 Ion exchange ...... 12 2.7.2 Microbial degradation ...... 13 2.7.3 Biosorption ...... 14 2.8 Mango tree ...... 15 2.9 Synthesis of activated carbon...... 17 2.10 Activation mechanism ...... 18 2.11 Adsorption equilibrium ...... 20 2.12 Langmuir adsorption isotherm ...... 22

2.13 Freundlich adsorption isotherm ...... 23 2.14 Mechanism of adsorption ...... 24 2.15 Turbidity ...... 25 CHAPTER THREE ...... 27 MATERIALS AND METHODS ...... 27 3.1 Collection of materials ...... 27 3.2 Preparation of carbon adsorbent ...... 28 3.3 Preparation of activated carbon ...... 29 3.4 Preparation of Mangifera indica kernel ash ...... 29 3.5 pH variation ...... 29 3.6 Contact time ...... 30 3.7 Dosage...... 30 3.8 Concentration of metal ions ...... 30 3.9 Temperature ...... 31 3.10 Equilibrium adsorption isotherms ...... 31 3.11 Turbidity removal ...... 32 3.12 Instrumentation ...... 33 3.13 Data presentation and analysis ...... 33 CHAPTER FOUR ...... 34 RESULTS AND DISCUSSION ...... 34 4.1 Sorption experiments ...... 34 4.1.1 Effects of contact time ...... 34 4.1.2 Effects of initial concentration on metal ions ...... 37 4.1.3 Effects of dosage ...... 40 4.1.4 Effects of temperature ...... 42 4.1.5 Effects of pH ...... 45 4.2 Freundlich and Langmuir adsorption isotherm constants ...... 47 4.3 Turbidity removal ...... 49 CHAPTER FIVE ...... 50 CONCLUSION AND RECOMMENDATIONS ...... 50 5.1 Conclusions ...... 50 5.2 Recommendations ...... 51 REFERENCES ...... 52

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Appendices ...... 59 Appendix 1: Calibration curves for Pb2+ ions ...... 59 Appendix 2: Calibration curve for Cd2+ ions ...... 59 Appendix 3: Langmuir adsorption isotherms for Pb2+ for MKAC ...... 59 Appendix 4: Langmuir adsorption isotherm for Pb2+ for MKC ...... 60 Appendix 5: Langmuir adsorption isotherm for Pb2+ on MKA ...... 60 Appendix 6: Langmuir adsorption isotherm for Pb2+ on MBM ...... 60 Appendix 7: Freundlich adsorption isotherm for Pb2+ on MKAC ...... 61 Appendix 8: Freundlich adsorption isotherm for Pb2+ ions on MKC ...... 61 Appendix 9: Freundlich adsorption isotherm for Pb2+ ions on MKA ...... 61 Appendix 10: Freundlich adsorption isotherm for Pb2+ ions on MBM ...... 62 Appendix 11: Langmuir adsorption isotherm for Cd2+ ions on MKAC ...... 62 Appendix 12: Langmuir adsorption isotherm for Cd2+ ion on MKC ...... 62 Appendix 13: Langmuir adsorption isotherm for Cd2+ ions on MKA ...... 63 Appendix 14: Langmuir adsorption isotherm for Cd2+ ions on MBM ...... 63 Appendix 15: Freundlich adsorption isotherm for Cd2+ ions on MKAC ...... 63 Appendix 16: Freundlich adsorption isotherm for Cd2+ ions on MKC ...... 64 Appendix 17: Freundlich adsorption isotherm for Cd2+ ions on MKA ...... 64 Appendix 18: Freundlich adsorption isotherm for Cd2+ ions on MBM ...... 64 Appendix 19: Raw data for Pb2+ ions ...... 65 Appendix 20: Raw data for Cd2+ ions ...... 70 Appendix 21: Comparison of percentage removal versus contact time ...... 75 Appendix 22: Comparison of percentage removal versus initial metal concentration ...... 76 Appendix 23: Comparison of percentage removal versus dosage ...... 76 Appendix 24: Comparison of percentage removal versus temperature ...... 77 Appendix 25: Comparison of percentage removal versus pH ...... 77 Appendix 26: Parameters for drawing Langmuir and Freundlich adsorption isotherm for Pb2+ ions ...... 78 Appendix 27: Parameters for drawing Langmuir and Freundlich adsorption isotherm for Cd2+ ions ...... 79 Appendix 28: Raw data for turbidity ...... 81 Appendix 29: Comparison for percentage turbidity removal ...... 82

viii

List of tables

Table Title page

4.1 Langmuir and Freundlich constants for Pb2+ ions 47

4.2 Langmuir and Freundlich constants for Cd2+ ions 48

List of Figures

Figure Title Page Figure 2.1 Mangifera indica tree and fruits 16 Figure 3.1 Dried Mangifera indica kernels 27 Figure 3.2 Mangifera indica kernel powder 28 Figure 4.1 Percentage removal of Pb2+ ions versus contact time at 25ºC, 80 35 mg/L and dosage of 1 g Figure 4.2 Percentage removal of Cd2+ ions versus contact time at 25ºC, 80 36 mg/L and dosage of 1 g Figure 4.3 Percentage removal of Pb2+ ions versus concentration at 25oC, 60 38 minutes and dosage of 1 g Figure 4.4 Percentage removal of Cd2+ ions versus concentration at 25oC, 60 39 minutes and dosage of 1 g Figure 4.5 Percentage removal of Pb2+ ions versus dosage at 25oC, 80 mg/L 40 and 60 minutes Figure 4.6 Percentage removal of Cd2+ ions versus dosage at 25oC, 80 mg/L 41 and 60 minutes Figure 4.7 Percentage removal of Pb2+ ions versus temperature at 80 mg/L, 43 60 minutes and dosage of 1g Figure 4.8 Percentage removal of Cd2+ ions versus temperature at 80 mg/L, 44 60 minute and dosage of 1 g Figure 4.9 Percentage removal of Pb2+ ions versus pH at 25oC, 60 minutes 45 and dosage of 1 g Figure 4.10 Percentage removal of Cd2+ ions versus pH at 25oC, 60 minutes 46 and dosage of 1 g Figure 4.11 Percentage turbidity removal versus dosage 49

ABBREVIATIONS AND ACRONYMS

MKAC Mangifera indica kernel activated carbon

MKC Mangifera indica kernel carbon

MKA Mangifera indica kernel ash

MBM Mangifera indica kernel biomass pH power of hydrogen

FTU Formazine turbidity unit

ABSTRACT Lack of sufficient safe drinking water remains a major challenge world over. Further, population growth and subsequent growth in agriculture, industry and technology continues to contribute to increased contamination of the little available clean water everyday. Major contaminants include, agro-chemical residuals, industrial effluents, acids, dyes and toxic heavy metals. Heavy metals of concern includes lead and cadmium because at even very low levels are toxic and have no known metabolism in the body. Literature findings have established a direct correlation between the level of turbidity and microbial load. convectional methods fall short because they are expensive or not readily available. The current work sought to establish a low cost effective adsorbent by utilizing mango (Mangifera indica L.) kernels agricultural waste as a resource to prepare adsorbent materials. Biomass, MBM was obtained by grinding dried kernels, ash, MKA was obtained by burning M.indica kernels in presence of oxygen in a furnace at 600ºC. Carbon, MKC and activated carbon, MKAC, were prepared by pyrolysis of dried kernels and activated kernels in a furnace at 400ºC, respectively. The materials obtained were utilized for the adsorption of lead and cadmium ions and turbidity from wastewaters. Batch experiments were carried out to determine the effect of contact time, initial concentration of metal ions, dosage, temperature and pH on the percentage removal of Pb2+, Cd2+ and turbidity on the four adsorbents. The adsorption capacity for Pb2+ was 8.73 for MKAC, 5.69 for MKC, 9.69 for MKA and 4.69 for MBM and 12.76, 7.13, 12.71 and 3.8 for MKAC, MKC, MKA and MBM, respectively for Cd2+. MKAC, MKC and MKA fitted well in Freundlich adsorption isotherm model for Pb2+ and Cd2+ with R2 values of 0.989 for MKAC, 0.993 for MKC and 0.978 for MKA with Pb2+ and 0.974, 0.987 and 0.914 for MKAC, MKC and MKA, respectively for Cd2+. MBM fitted in the Langmuir model with R2 value of 0.983 and 0.997 for Pb2+ and Cd2+, respectively. Highest percentage turbidity removal were 54.82, 31.63, 97.37 and 59.97 for MKAC, MKC, MKA and MBM, respectively. Products derived from M. indica kernel were found to be effective adsorbents.

CHAPTER ONE

INTRODUCTION

1.1 Background Information

Industrial waste constitutes the major source of various kinds of metal pollution in natural waters. Rapid industrialization has led to increase in disposal of heavy metals into the environment. According to Wasewar (2010), mining activities, agricultural run-off, industrial and domestic effluents are mainly responsible for the increase of the metals released into the environment. Metals released into the environment tend to persist indefinitely accumulating in living tissues throughout the food chain and are posing threat to the environment and public health (Aksu and Kutsa, 1991). Heavy metals like lead and cadmium are present in low concentrations in wastewaters and are difficult to remove from water. Once in the body there is no known metabolism or excretion of the heavy metals.

There are many methods employed to remove and recover the metals from the environment and many physio-chemical methods have been proposed for removal and recovery of heavy metals from wastewaters (Barakat, 2011). They include; adsorption, microbial degradation, chemical oxidation, precipitation, ion exchange and solvent extraction. Adsorption is an effective method of removing heavy metals from industrial effluents. Adsorbents such as activated carbon, silicates, aluminates and cellulose can be used. Activated carbon is effective due to its large number of pores, large surface area relative to the size of the actual carbon particle and visible exterior surface and high degree of porosity making it most versatile adsorbent to be used for effective removal of organic solids that have extraordinary large internal

2 surface and pore volume. Its unique pore structures play an important role in many different liquid and gas phase application.

Adsorption processes offer an effective alternative approach for lead, cadmium, and turbidity remediation owing to the lower initial cost, sludge free, clean, simple design and operation, easy recovery and insensitivity to toxic pollutants. Most agricultural solid wastes are inexpensive, abundant, easily available and eco- friendly.

Consequently many researchers have focused on the feasibility of low-cost materials that were derived from agricultural wastes for the removal of various dyes, heavy metals and other pollutants (Budinova et al., 2006). Wastes and industrial by-products can be used directly or after modification as adsorbents.

An adsorbent can be termed as a low cost adsorbent if it requires little processing, is provided in nature or is a by-product of waste materials. Generally plant biomass exist as cellulosic surfaces, that have partially negative charges in water. They posses columbic interaction with cationic species in water (Mckay et al., 1987). The high binding abilities of cationic species on the adsorbents are mainly the result of columbic interactions. Due to the sorption properties possessed by cellulosic materials,many agricultural wastes have been used for removal of various organic and inorganic compounds.

Complete removal or reduction of lead to acceptable concentration has become a major challenge in environmental protection. According to Zhaoquin (2013) it is difficult for lead to be biodegraded. Consequently, development of potentially low- cost adsorbents with high adsorption capacity is critical for heavy metal removal.

Many materials such as synthetic resin, green macro algae, bagasse fly ash and water hyacinth have been used as adsorbents. The current study aimed at producing eco- friendly low cost adsorbent from M. indica kernels.

1.2 Statement of the problem

Kenya is a water scarce country and the large population lacks access to safe, clean drinking water. Population, industrial and economic growth has led to increased pollution and pressure on water. The little available water has been contaminated and there is need to purify it for human consumption. Lead and cadmium are key contaminants and are highly toxic. The adsorption characteristics of lead and cadmium using various adsorbents have been investigated for purposes of separation and purification. The adsorbents used which include carbonized beet pulp, peat, fly ash and bentonite are expensive or not readily available.

There is therefore need to prepare a low cost yet effective adsorption material. In the local markets, there are a lot of agricultural wastes like M. indica kernels which do not decay easily. There is a need to find ways of reducing these solid wastes and converting the otherwise pollutants into useful materials. Activated carbon processed from M. indica kernels would be cost effective in removing lead, cadmium and turbidity from wastewaters at the same time controlling solid wastes from market places.

1.3 Justification of the Study

The availability of safe clean drinking water is a major concern in Kenya. The high level of pollution and inadequate treatment of wastewater has enhanced the water

crisis in our nation. Lead and cadmium being persistent in the environment have

contributed to water contamination. There is need to develop adsorbents for these

heavy metals to ensure safe drinking water to Kenyan growing population.

Agricultural solid wastes like chaff, rice husk, sesame, sunflower and tea wastes have

been used to remove lead from waste waters (Kafia and Surchi, 2011). Also pineapple

stem waste has been used to remove basic dye (methylene blue) by adsorption

(Hameed et al., 2009). Since M. indica kernels are readily available agricultural

wastes, they were utilized as adsorbents for lead, cadmium and turbidity removal in

this research work.

1.4 Hypothesis

Biomass, charcoal, activated charcoal and ash prepared from M. indica kernels are

effective adsorbents for lead, cadmium and turbidity.

1.5 General objective

The main aim of the study was to determine efficiency and capacity of charcoal,

activated charcoal, ashes and biomass generated from M. indica kernels in removal of

lead, cadmium and turbidity from water.

1.6 Specific objectives i. To determine percentage removal of Pb2+ and Cd2+ from water using charcoal,

activated carbon, ash and biomass from M. indica kernels while varying contact time,

initial metal concentration, adsorbent dose, temperature and pH. ii. To determine the optimum adsorption capacities of charcoal, activated carbon, ash

and biomass from M. indica kernels for lead and cadmium ions from water.

5 iii. To determine the coagulation capacity of charcoal, activated carbon, ash and

biomass from M. indica kernels towards removal of turbidity.

1.7 Significance of the Study

Agricultural solid waste disposal is a concern in the country. Mismanagement of

these wastes results in pollution of the natural environment and may posse substantial

danger to public health and welfare. The study aimed at producing a cheaper

adsorbate to purify wastewaters by utilizing agricultural waste products that are

responsible for solid waste in our local markets. Therefore the study converted the

otherwise waste into cost effective adsorbent at the same time enhancing green

chemistry.

CHAPTER TWO

LITERATURE REVIEW

2.1 Utilization of agricultural waste

There are a number of researches done on utilization of activated carbon from agricultural waste materials. Those studied include performance of mango seed adsorbents in adsorption of anthraquinone and azo and dyes in single and binary aqueous solutions (Martin et al., 2009), comparative studies of adsorbents prepared from agricultural waste like bagasse, jackfruit peel & ipomoea fistulosa (beshram)

(Pandharipade et al., 2012), jujube seed for removal of anionic dye (Congo Red) from aqueous medium (Somosekhara, 2012), removal of Erichrome Black T from synthetic wastewater by activated Nilgiri leaves (Ladhe et al., 2011).

Other studies like dye uptake onto processed and raw mango seed back (Itodo et al.,

2011), use of activated carbon prepared from sawdust and rice-husks for adsorption of acid yellow 36 (Malik 2003), synthesis of adsorbents from waste materials such as

Ziziphus jujube seed and mango kernel (Pandharipade et al., 2012), utilization of mango seed (Kittiphoom 2012), effectiveness of cactus biomass and its combusted products in removal of colour, turbidity and selected metal ions from contaminated water (Mbugua 2015), equilibrium and kinetic studies of safranine adsorption on alkali –treated mango seed integuments (Malekbala et al., 2012) also utilized agricultural wastes.

In these researches there are findings that the amount of sample increased the percentage of adsorption although the optimum adsorbate/adsorbent ratio was not stated. Also the influence of pH on adsorption has been identified as a variable that

7 influences the amount of adsorbate adsorbed. According to Zenasni et al.(2012) the affinity of weak organic acids or bases for activated carbon is an important function of pH. Lead was found to adsorb below a pH of 8 and it desorbs above pH of 10. In this study the effect of pH on adsorption was investigated.

The adsorption characteristics of activated carbons are generally governed by the surface area, pores formation on the surface, and surface functional groups. It is believed that mesopores are more suitable for adsorption as compared to micropores and macropores. Surface functional groups play an important role during cationic and anionic adsorbate removal (El-Hendawy, 2009). Although many agricultural by products have been used as source for activated carbon, it is unfortunate that not much has been said about by products of Mangifera indica kernels as a low cost adsorbent and precursor for the production of activated carbon. Millions of tons of

M.indica kernels are generated from mango production and processing. The utilization of these wastes as an adsorbent will solve the problem of its disposal.

According to Ahmad et al. (2012), the chemical composition and the physical properties of the precursor, as well as the methods and processing conditions employed for activation, determine the final pore size distribution in the activated carbon and that guides its adsorption properties. Therefore different precursor material will give rise to activated carbon with different surface area, particle size, pore size hardness and density.

2.2 Water scarcity

According to Kenya government 2006 report on Kenya national water development,

17 million out of the 41.8 million Kenyans lack safe water. This accounts for about

41 percent. Kenya has limited renewable water supply and is classified as a water scarce country. Kenyans depend heavily on water for; drinking, agriculture, livestock and fishing. Kenya is mainly an agricultural country with an expanding economy whose basic element for development is water. The amount of water actually available for utilization in any one year depends on the rate of run-off, the aridity of the catchment area and the methods of interception at various points in the hydrological cycle (Onjala, 2002).

For decades water scarcity in Kenya has been a major issue caused mainly by years of recurrent drought, poor management of water supply, contamination of available water sources and a sharp increase in water demand due to increased population

(Marshall, 2011). Some of the harmful compounds are lead and cadmium. According to Mwangi (2009), the water condition in Kenya has caused a number of issues including diseases and tribal conflicts over the remaining resources. Contamination is a major reason for worsening of water crisis in Kenya. Faced with the problem of water scarcity, there is a need to come up with mitigation measures and interventions that will protect the scarce resource.

2.3 Water pollution

Water pollution is the contamination of water bodies such as lakes, rivers, oceans, aquifers and ground water. Water pollution occurs when pollutants are directly or indirectly discharged into water bodies without adequate removal. Contamination of

9 water affects humans and other organisms in nature. Humans and other organisms produce bodily wastes which enter into rivers, lakes, oceans and other surface waters

(Glassmeyer et al., 2005). Industrial chemicals are also released to water bodies

(Giorgi and Malacalza, 2002). Kenya’s water resources have been under increasing threat of pollution in recent years due to rapid demographic changes and human settlement that lack appropriate sanitary infrastructure (Wilcove et al., 1998). In high concentrations these wastes result in bacterial contamination and excessive nutrient loading. Water pollution is also a source of many diseases and death worldwide. The problem of water pollution and quality degradation in the developing countries is increasingly becoming a threat to the natural water resources. This phenomenon is attributed to the increasing quest of these countries to attain industrialization status and diversification of the national development goals and Kenya is no exception to this phenomenon (Kithiia, 2010).

2.5 Heavy metal toxicity

Heavy metals such as lead, cadmium and mercury with adverse health effects on the human metabolism present obvious concerns due to their persistence in the environment and documented potential for serious consequences. Other heavy metals that have also posed health problems include nickel, chromium and copper. Heavy metal pollution occurs in many industrial wastewaters such as those produced by metal plating facilities, mining operations, battery manufacturing processes, production of paints and pigments and glass production industry (Argun et al., 2007).

Environmental contamination by toxic metals is a serious problem worldwide due to their incremental accumulation in food chain and continued persistence in the ecosystem. The heavy metals are not biodegradable and their persistence in streams

10 and lakes leads to bioaccumulation in living organisms causing health problems in animals, plants and human beings.

According to Huang (2009), heavy metal toxicity inhibits nitrogen removal performance in plants including the specific ammonia uptake rate and nitrate uptake rate when a combination of heavy metals (lead, nickel and cadmium) was used.

Excessive human intake of copper leads to severe mucosal irritation and corrosion, widespread capillary damage, hepatic and renal damage and central nervous system irritation followed by depression (Ajamal et al., 1998). Severe gastrointestinal irritation and possible necrotic changes in the liver and kidney can also occur.

Lead is one of the most frequently reported unintentional toxic heavy metal exposure and leading cause of single metal toxicity in children. It has no known beneficial function in human metabolism. Its exposure is often through lead-containing paints, food stored in lead can liners, food stored in ceramic jars or contaminated water.

Inhalation of lead particulates is a primary route of occupational lead exposure, while oral ingestion is a primary form of exposure in the general population (Ahmed and

Siddiqui, 2007). Lead ‘mimic’ calcium in the body and therefore most absorbed lead is stored in bones and can remain for a long time. Conditions that cause release of calcium from the bones for instance fracture, pregnancy, age related bone loss among others also release stored lead from bones thus allowing it to enter into the blood and other organs. In addition to disrupting calcium metabolism, it also mimics and displaces magnesium and iron from certain enzymes that construct the building blocks of DNA. Lead will also disrupt the activity of zinc in synthesis of heme

(Kirberger, 2013).

Chronic low-level lead exposure is associated with increase in hypertension risk and reduction in kidney function. Higher levels exposure affect the endocrine glands and reproductive hormones. It can also cause anemia. In children low level lead exposure can result in severe developmental disorders which include accelerated skeletal growth, cognitive deficit and IQ decline.

According to Thevenod and Lee (2013), cadmium exposure presents large threat to human health. Cadmium has no beneficial role in human metabolism. It is easily absorbed through inhalation of cigarette smoke and can be absorbed through the skin.

Following exposure, cadmium binds to red blood cells and is transported through the body where it concentrates in the liver and kidney. It is also found in testes, pancreas and spleen (Sigel et al., 2013). Cadmium mimics zinc and is thought to exert its toxicity by disrupting zinc metabolism.

There are 3000 different enzymes and structural proteins in human metabolism that require zinc for their activity and are potential targets of cadmium toxicity (Sigel et al., 2013). Chronic cadmium exposure can result in the accumulation of cadmium complexes in the kidney leading to renal failure, decreased bone mineralization and decreased lung function. Cadmium is a known human carcinogen (Sinicropi et al.,

2010).

2.6 Water treatment

Water is a commodity that is consumed and a carrier of many substances or properties such as heat, disease vectors, pollutants and energy (Jordaan et al., 1993). Whereas

12 the total quantity of water on earth remains constant, its quality changes in both time and space. The problem of water quality causes a great strain on water supply system especially in cities along river causes. In 1985, at the midpoint of the international water supply and sanitation decade, it was reported that although 870 million people lived in urban areas of the developing world, roughly 1.6 million were rural inhabitants and approximately 22% of the urban group lacked water supply and 40% were without sanitation. Water treatment is the process of removing undesirable chemicals, biological contaminants, suspended solids and gases from contaminated water (Olsson and Newell, 1999). Water quality involves both aesthetic and health concerns depending on the contaminants present. Therefore, the purpose of water treatment is to produce safe aesthetically pleasant water. This ensures that the water be free of harmful chemicals and microbes as well as have an acceptable taste and odour. Adsorbents such as charcoal, clay, glass and organic matter have been used for water treatment (Bottino et al., 2001).

2.7 Methods used to remove water contaminants

Common methods used to remove heavy metals include ion exchange, flotation, precipitation, biosorption, microbial degradation and chemical oxidation among others.

2.7.1 Ion exchange

Ion exchange (IE) is a water treatment method where one or more undesirable contaminants are removed from water by exchange with another non-objectionable or less objectionable substance. Both the contaminant and the exchanged substance must be dissolved and have the same type of electrical charge (Rhoades, 1982). Ion

13 exchangers are either cation resin exchanger that exchange positively changed ions, anionic exchanger for exchanging negatively changed ions or amphoteric exchanger that are able to exchange both cations and anions. Ion exchanger media have an affinity for certain contaminants over others. The strength of this selective affinity is governed by the valence of the contaminant and the weight or size of the contaminant ion (Shkolnikor et al., 2012).

When contaminants dissolve in water they form ions. Ions are electrically charged portions of a compound. There is a balance of positively and negatively charged ions in natural waters. When contaminants are dissolved in water, the water is crystal clear. If the water is cloudy it is likely that some, or all, of the contaminants are in solid form.

Dumping which is related to the affinity sequences and to the relative concentration of the contaminants in the raw water is a major limitation of ion exchange process. As the selective cycle continues, the highest preferred contaminant will be dumped. This would increase its concentration in the water above the value in the raw water concentration. The concentration of the less preferred contaminant could exceed a water standard near the end of each service run (Shkolnikor et al., 2012). The resin recovery by use of brine weakens ion exchange and need to be constantly replaced making the method expensive.

2.7.2 Microbial degradation

Microbial degradation of pollutants strives to find sustainable ways to clean up contaminated environment (Koukkou, 2011). These bioremediation and

14 biotransformation methods endeavour to harness the naturally occurring ability of microbial xenobiotic metabolism to degrade, transform or accumulate a huge range of compounds. The elimination of a wide range of pollutants and wastes from environment is a requirement to promote a sustainable development of our society with low environmental impact. Rates of biodegradation depend greatly on the composition, state, and concentration of the oil or hydrocarbons, with dispersion and emulsification enhancing rates in aquatic systems and absorption by soil particulates being the key feature of terrestrial ecosystems.

Temperature, oxygen and nutrient concentrations are important variables in both types of environments. Salinity and pressure may also affect biodegradation rates in some aquatic environments, and moisture and pH may limit biodegradation in soils

(Leahy and Colwell, 1990). Hydrocarbons are degraded primarily by bacteria and fungi. Adaptation by prior exposure of microbial communities to hydrocarbons increases hydrocarbon degradation rates. Adaptation is brought about by selective enrichment of hydrocarbon-utilizing microorganisms and amplification of the pool of hydrocarbon-catabolizing genes. The latter phenomenon can now be monitored through the use of DNA probes (Das and Chandran, 2010). Increases in plasmid frequency may also be associated with genetic adaptation. Seeding to accelerate rates of biodegradation has been shown to be effective in some cases, particularly when used under controlled conditions, such as in fermentors or chemostats.

2.7.3 Biosorption

Metal biosorption is the removal of metal from a solution by inactive non- living material due to presence of high attractive force between the two. It is the binding and

15 concentration of heavy metals from aqueous solutions (even very dilute ones) by certain type of inactive, dead microbial biomass (Macaskie et al., 1992). Biosorption is also due to the presence of functional groups like amine, hydroxyl, carboxyl among the many (Wang, 2002).

Many investigators have found various methods for removal of heavy metals from wastewaters. The presence of heavy metals in form of complex on the biological mass is a cause of concern. Biomass has been used effectively for the removal of heavy metals by researchers. The chemically and physically modified biomass has higher potential for removal of heavy metals than untreated biomass (Dhokpande and

Kaware, 2013). Biological materials, such as chitin, chitosan, peat, yeasts, fungi or bacterial biomass, are used as chelating and complexing sorbents in order to concentrate and to remove dyes from solutions (Gregorio, 2006). Biosorption is important in the removal of potentially toxic and or valuable rare metals and nuclides from aqueous effluents which can result in detoxification and therefore safe environment. Furthermore appropriate treatment of loaded biomass can enable recovery of valuable elements for recycling or further containment (Amorim et al.,

2003).

2.8 Mango tree

The mango is a common tropical fruit usually found in southern Asia especially eastern India (Litz, 2009). In Kenya mangoes are majorly grown in Eastern and coastal provinces. There are some varieties of mangoes in central province like

Murang’a and Maragua districts (Maundu, 2007). Mangoes belong to the genus

Angifera, consisting of numerous species of tropical fruiting trees in the flowering

16 plant family Anacardiaceae. Mango trees (Mangifera indica) reach 35-40 m in height, with a crown radius of 10 m. The leaves are ever green, alternate, simple, 15-35 cm long and 6-16 cm broad. The fruit takes from 3-6 months to ripen. The ripe fruit is variable in size and colour. It may be yellow, orange red or green when ripe, depending on the cultivar. In the centre is a single flat oblong seed that can be fibrous or hairy on the surface, depending on the cultivar (Litz, 2009).

Ripe mangoes are processed into frozen mango products, canned products, dehydrated products and ready-to-serve beverages (Ramteke and Eipeson, 1997).

After consumption or industrial processing of the fruits, considerable amount of mango seeds are discarded as waste (Puravankera et al., 2000). Mango seed accounts for 35-55% of the fruit depending on the variety. Utilization of mango seed may be an economical way to reduce the problem of waste disposal from mango production.

Figure 2.1: Mangifera indica tree and fruits

2.9 Synthesis of activated carbon

Activated carbon is an effective adsorbent material due to its large number of pores.

These provide a large surface area relative to the size of the actual carbon particle and visible exterior surface. Its high degree of porosity and surface area makes it most versatile adsorbent to be used for effective removal of organic solids that have extraordinary large internal surface and pore volume. These unique pore structures play an important role in many different liquid and gas phase application. Adsorption processes provide an effective alternative treatment approach for lead and cadmium removal due to the lower initial cost, sludge free, clean, flexibility and simplicity of design, simple operation, easy recovery and insensitivity to toxic pollutants.

Agricultural solid wastes can be used as an inexpensive precursor material with high carbon content (Arami-Niya et al., 2011). Wastes or by-products of industries can be used, directly or after treatments, as adsorbents in adsorption processes. Any carboneous material with high concentration of carbon can be simply changed into activated carbon. The most common raw materials are wood, charcoal, nut shells, bituminous coal lignite, peat, bone and paper mill waste. Activated carbon can be produced by physical reactivation involving carbonization carried at temperatures in the range 600 – 900ºC in the absence of oxygen or oxidation by exposing the carbonized material to oxidizing atmospheres at temperatures above 250o C (Ansari and Mohammad-Khah, 2009 ). Chemical activation involves pretreatment of the raw material with an acid, strong base, or a salt followed by carbonization at lower temperatures of between 450 – 900o C. Chemical activation uses lower temperatures and shorter time and hence preferred to physical activation. During the carbonization

18 process, the incomplete combustion tremendously increases the surface of carbon by the removal of hydrocarbons or tars.

The processing of activated carbon basically involves selection of raw material, carbonisation and activation. For the selection of an appropriate raw material for preparation of porous carbon, several factors are taken into consideration.

Industrially, inexpensive material with high carbon and low inorganic (that is low ash) content is preferred as raw material for the production of activated carbon. High density of the precursor and sufficient volatile content are of considerable importance

(Manocha, 2003). Evolution of volatiles during pyrolysis results in porous char, essential for making activated carbons, while high density contributes to enhanced structural strength of the carbon, essential to withstand excessive particle crumble during use.

2.10 Activation mechanism

The structure of the pores and pore size distribution are largely dictated by the nature of the raw materials and the history of their carbonization. Carbon atoms differ from each other in their reactivity depending on their spatial arrangement. Activation eliminates the disorganised carbon, exposing the aromatic sheets to the action of activation agents and leads to development of a microporous structure. Since activation is associated with weight loss of the host carbon, the extent of burn-off of the carbon material is taken as a measure of the degree of activation (Manocha,

2002). At a particular temperature, weight loss increases linearly with activation time.

Normally, in the first phase, the deorganised carbon is burnt preferentially when the burn-off is about 10%. This results in the opening of blocked pores. Subsequently, the

19 carbon of the aromatic ring system starts burning, producing active sites and wider pores.

In the latter phase, excessive activation reaction results in knocking down of the walls by the activated agents and a weight loss of more than 70%. This results in an increase in transitional pores and macropores. The volume of the micropores decreases but there is no significant increase in adsorption capacity or internal surface area. At higher burn-off, the difference in porosity created by different activating agents becomes more pronounced. In a typical example, activation of a hard wood with water vapour results in progressive development and widening of all size pores until at a burn-off of 70%, the activated product contains a well-developed porous system with wide pore size distribution.

Activation with 50–70% burn-off causes an increase in the total adsorption volume from 0.6 to 0.83 cm3/gm (Rodriguez, 1995). But as it is associated mainly with widening of pores, the surface area remains almost the same. Activation with carbon dioxide mainly develops microporosity over the entire range of burn-off. The micropores account for about 73% of the total adsorption pore volume, for over 90% of total surface area. The micropores contribute only 33% towards total pore volume and 63% towards surface area in the case of steam-activated carbon. Thus carbon

3 produced by CO2 activation has lower total pore volume 0.49 cm /gm than those of corresponding samples obtained by activation of steam.

However, the effective surface area in both cases is almost the same. This is mainly due to the contribution of micropores to the surface area. Moreover, the carbon atoms

20 which are localised at the edges and the periphery of the aromatic sheets or those located at defect position and dislocations or discontinuities are associated with unpaired electron or have residual valencies which are rich in potential energy.

Consequently, these carbon atoms are more reactive and have a tendency to form surface oxygen complexes during oxidative activation (Patrick, 1995). These surface chemical groups promote adsorption and are beneficial in certain applications.

Alternatively, these surface oxygen complexes break down and peel off the oxidised carbon from the surfaces as gaseous oxides leaving behind new unsaturated carbon atoms for further reaction with an activating agent.

Thus, activation mechanism can be visualised as an interaction between the activating agent and the carbon atoms. These forms the structure of intermediate carbonised product resulting in useful large internal surface area with interconnected pores of desired dimension and surface chemical groups (Ekpete et al., 2011).

2.11 Adsorption equilibrium

Adsorption is the adhesion of substances onto the surface of adsorbent solid. It is the formation of gas, liquid or solid to the surface of a solid or less frequently a liquid

(Itodo et al., 2011). Adsorption occurs at solid-solid, gas–solid, liquid–liquid and liquid–gas interfaces. An isotherm is a functional expression for the variation of adsorption relative to the concentration of adsorbate in the bulk solution at a constant temperature. It describes the relation between the adsorbate retained by the activated charcoal and the adsorbate equilibrium constant. This graphical representation shows the relationship between the amounts adsorbed by a unit weight of adsorbent for example activated carbon and the amount of adsorbate remaining in a test medium of

21 equilibrium. Sorption isotherm is based on data that is specific for each system and the isotherm must be determined for every application. According to Itodo et al.,

(2011) the major factors in determining the shape of an isotherm are;- i) the number of compounds in the solution ii) the relative adsorb abilities of the compound iii) the initial concentration of the solution iv) the degree of competition among solutes for adsorption sites v) the characteristics of the specific carbon

An adsorbate is the molecule that accumulates or adsorbs at the interface. The solid on which adsorption occurs is the adsorbent. According to Letterman (1999), adsorbate are held on the surface by various types of chemical forces such as hydrogen bond, dipole-dipole interactions and Van der Waal’s forces.

In adsorption equilibrium the rate at which the materials adsorb onto the surface is equal to the rate at which they desorb. The adsorption can be on a monolayer as explained by Langmuir or on a multilayer as explained by Freundlich. The adsorption capacity of activated carbon may be determined by the use of adsorption isotherms.

Freundlich isotherm used in heterogeneous surface is used to measure adsorption from solution in environmental engineering and specifically drinking water treatment applications. For a single solute system this isotherm is more convenient.

The amount of lead and cadmium at equilibrium qe is calculated from the mass balance equation given by;

( ) ⁄ …………………… 1

Where qe is equilibrium concentration, Co is initial metal concentration, Ce is equilibrium concentration of the adsorbate, V is volume of solution of the sample and

W is the dosage.

2.12 Langmuir adsorption isotherm

The Langmuir adsorption isotherm describes quantitatively the formation of a monolayer adsorbate on the outer surface of the adsorbent and after which no further adsorption takes place. The Langmuir represents the equilibrium distribution of metal ions between the solid and liquid phases (Doda et al., 2012). The Langmuir isotherm is valid for monolayer adsorption onto surface containing a finite number of identical sites. The model assumes uniform energies of adsorption onto the surface and no transmigration of adsorbate in the plane of the surface. Based on these assumptions,

Langmuir represents the following equation;

…………………………………… (2)

Langmuir adsorption parameters are determined by transforming the Langmuir equation (2) to linear form;

………………………………………. (3)

Where;

Ce = the equilibrium concentration of adsorbate mg/L

Qe=the amount of metal adsorbed per gram of the adsorbent at equilibrium (mg/g)

Q0 = maximum monolayer coverage capacity (mg/g)

KL = Langmuir isotherm constant (L/mg)

The values of Q0 and KL are computed from the intercept and slope respectively of the Langmuir plot of 1/qe versus 1/Ce.

The essential features of the Langmuir isotherm may be expressed in terms of equilibrium parameter RL which is a dimensionless constant referred to as separation factor or equilibrium parameter (Webber et al., 1974);

……………………………… (4)

Where;

Co =highest concentration

2.13 Freundlich adsorption isotherm

Freundlich equation is given by;

………………………….. (5)

Where Kf is constant measuring adsorption capacity, C is equilibrium concentration of the adsorbate in solution and qe is equilibrium surface coverage (amount of adsorbate adsorbed per unit weight of adsorbent). This equation describes non-linear adsorption in a narrow range of adsorbate concentration. The Freundlich equation can be reduced to linear form as;

………………(6)

Where qe is the amount at equilibrium (mg/g), Ce the equilibrium concentration of the

2+ 2+ adsorbate such as Pb or Cd ions and Kf and n are Freundlich constants. n gives an indication of how favorable the adsorption is and Kf is the adsorption capacity of the adsorbents. Kf can be defined as the adsorption or distribution coefficient and represents the quantity of Pb2+ and Cd2+ ions adsorbed onto biosorbents for a unit

24 equilibrium concentration (Adeogun et al., 2012). The slope 1/n ranging between 0 and 1 is a measure of adsorption intensity or surface heterogeneity, becoming more heterogeneous as its value gets closer to zero (Haghseresht, 1998). A value for1/n < 1 indicates a normal Langmuir isotherm while 1/n > 1 is indicative of cooperative adsorption. A plot of log qe against log Ce gives a straight line with slope 1/n and log

Kf as intercept. Freundlich model agrees with Langmuir equation and experimental data over moderate range of concentration.

2.14 Mechanism of adsorption

Understanding the mechanisms of the solute adsorption onto the solid surface is essential for certain removal of contaminants from aqueous solution. The adsorption mechanism involves oppositely charged ionic interaction such as dipole–dipole, dipole-induced dipole and induced dipole-induced dipole, hydrogen bonding, chemical bonding, and ion exchange. The surface chemistry of the adsorbent and its effect on the adsorption process is generally investigated in order to interpret the solute adsorption. Fourier transform infrared (FTIR) spectroscopy is a useful tool for studying the interaction between an adsorbate and the active sites on the surface of the adsorbent (Ahmad et al., 2011). Both cellulose and hemicelluloses contain majority of oxygen functional groups which are present in the lignocellulosic material such as hydroxyl, ether and carbonyl, while lignin is a complex, systematically polymerized, highly aromatic substance that acts as a cementing matrix that holds between and within both cellulose and hemicellulose units.

Parameters like pH, surface functional groups and pores size play very important roles in determining the adsorption mechanisms. Metal ions may form complexes

25 with surface functional groups of the adsorbents such as cellulose–OH and phenolic–

OH through ion exchange reactions. At lower pH, the functionality of these groups is not changed. At higher pH, these groups begin to neutralize changing their activity and binding properties. In order to understand how solute binds to the activated carbon surface, it is essential to identify the functional groups responsible for their binding. Most of the functional groups involved in the binding process are found in cell walls. Plant cell walls are generally considered as structures built by cellulose molecules, organized in microfibrils and surrounded by hemicellulosic materials, lignin and pectin along with small amounts of protein (Al-Ghouti et al., 2010).

During the activation process, these molecules are converted into graphitic carbon with some oxygen bonded functional groups. A lot of surface area is generated inside the molecule due to loss of volatile organic matters from the cell wall. Surface area and surface functional groups of activated carbons play the major role in adsorption processes.

2.15 Turbidity

Turbidity is a measure of suspended materials in water that decreases the passage of light through the water (Palanques et al., 2001). Clarity of water is important in producing products for human consumption and in many manufacturing operations.

Turbidity in water is caused by suspended and colloidal matter such as clay, silt, finely divided organic and inorganic matter, and plankton and other microscopic organisms (Davies and Smith, 2001). Higher turbidity increases water temperature because suspended particles absorb more heat. It also decreases the concentration of dissolved oxygen, higher turbidity also prevents penetration of light into water which reduces photosynthesis and suspended particles also clog fish gills. Various methods

26 have been used to remove turbidity which includes cloth filtration, sedimentation and coagulation.

CHAPTER THREE

MATERIALS AND METHODS

3.1 Collection of materials

Mangifera indica kernels were collected from Ol-Kalou market in Nyandarua

County. The kernels were washed thoroughly with water several times to remove all dirt particles and then sun dried for one day to remove excess water and further dried in an oven at a temperature of 100o C for 12 hours.

Figure 3.1: Dried Mangifera indica kernels

The dried kernels were cut into small pieces and ground using Retsch SR200

Guisseisen grinder made in Germany to obtain M. indica kernel powder. The powder was divided into four portions which were used to prepare activated carbon MKAC, carbon MKC, ash MKA and biomass MBM.

Figure 3.2: Mangifera indica kernel powder

Stock solution of lead and cadmium containing 1000 mg/L were prepared by dissolving 1.6 g of lead nitrate and 2.754 g of cadmium nitrate respectively. From the stock solution serial test solutions of lead and cadmium containing 20 mg/L, 40 mg/L,

60 mg/L, 80 mg/L 100 mg/L, 120 mg/L, 140 mg/L and 160 mg/L were prepared. The pH of solution was adjusted with 0.1M HCl and 0.1M NaOH and 50% H3PO4 was used as an activating agent.

3.2 Preparation of carbon adsorbent

Dried M. indica kernel powder was placed in crucibles and covered and the contents were placed in a furnace whose temperature was adjusted to 400o C. The powder was burned for four hours in the absence of oxygen to obtain M. indica carbon. The powdered carbon was stored in air tight bottles for use as adsorbent.

3.3 Preparation of activated carbon

Dried M. indica kernel powder was sieved to obtain fine powder. A 100 g of the raw sample was mixed with 50% phosphoric acid as an activating agent. The mixture was left standing overnight after which it was placed in a furnace at 400o C for 4 hours.

The sample was removed and placed in an ice bath then allowed to stand at room temperature. The procedure was repeated with 5 different samples using the activating agent. The powdered activated carbon (PAC) generated from the above procedure was washed with 0.1M HCl to remove surface ash followed by hot water.

The washed sample was then rinsed with distilled water to remove residual acid.

Rinsing was stopped when the pH of solution was 7. The samples were oven dried at

100o C overnight and stored in air tight containers.

3.4 Preparation of Mangifera indica kernel ash

A 500 g of dried M. indica kernels was burned in the presence of air to produce ash.

The kernels were placed in open crucibles and placed in Elsklo US 500 furnace at

600o C for six hours. The ash was washed with distilled water to remove the soluble part then oven dried. It was sieved to remove large particles and stored in air tight containers.

3.5 pH variation pH is an important parameter that influences the adsorption process by way of modifying the functional groups of the biomass. The effect of pH on adsorption of lead and cadmium was conducted with pH values of 2, 4, 6, 7 and 8 using 80 mg/L solution containing Pb2+ ions. A 0.1 g of adsorbents was agitated with 50 cm3 of metal ions at a constant time of 60 minutes. The samples were placed in a rotator

30 shaker with a shaking speed of 120 rpm at 25º C. The experiments were carried out with MKAC, MKA, MKC and MBM for Pb2+ and Cd2+ ions. A 0.1M NaOH and

0.1M HNO3 were used to adjust the pH of the solution using a magnetic stirrer.

Graphs of percentage removal against pH were drawn to show the effect on each adsorbent.

3.6 Contact time

A 0.1 g of activated carbon was agitated with 80 mg/L Pb2+ ions in 20, 40, 60, 80 and

100 minutes. The amount of Pb2+ and Cd2+ adsorbed was then determined using VGP

210 Buck atomic absorption spectrophotometer (AAS). The procedure was repeated with samples containing Cd2+ ions.

3.7 Dosage

The adsorption dosage was determined using 0.1 g, 0.2 g, 0.3 g, 0.4 g and 0.5 g.

Activated carbon was agitated with Pb2+ ions each in turn at optimum contact time using water bath shaker at room temperature to determine optimum adsorbent dosage.

The amount of Pb2+ adsorbed was determined using AAS. The studies were done at room temperature of 25 2oC at constant shaking speed. The adsorption studies of

Pb2+ were also carried out with unmodified carbon, kernel ash and biomass (Prasad et al., 2013). The procedure was repeated with samples containing Cd2+ ions. The percentage removal by the adsorbents were calculated and comparison made thereof.

3.8 Concentration of metal ions

A 0.1 g of the adsorbents was agitated with 20 mg/L, 40 mg/L, 60 mg/L, 80 mg/L,

100 mg/L, 120 mg/L, 140 mg/L and 160 mg/L of Pb2+ and Cd2+ ions in a water bath

31 shaker. The temperature was maintained at 25oC at uniform shaking speed. The studies were carried out at optimum contact time for maximum adsorption to be realized. The results obtained were used to plot adsorption isotherms and to determine the adsorption capacity.

3.9 Temperature

The variation of percentage removal of Pb2+ and Cd2+ adsorbed by MKAC, MKA,

MKC and MBM were investigated as a function of temperature and the results recorded. A 50 cm3 solution of Pb2+ and Cd2+ was agitated with 0.1 g of the activated carbon for 60 minutes at a constant shaking speed and a temperature of 25ºC. The mixture was then filtered into a clean plastic container. The study was repeated at

35ºC, 45ºC, 55ºC and 65ºC. The filtrate was analyzed with AAS to determine the percentage removal. The procedure was repeated with MKC, MKA and MBM.

3.10 Equilibrium adsorption isotherms

This study was done with the optimum pH of Cd2+ and Pb2+. In order to understand the adsorbate-adsorbent interaction, optimization of the use of adsorbent and its adsorption capacity towards a particular adsorbate is necessary for studying the adsorption isotherm. Adsorption capacity of M. indica kernels in different forms towards Cd2+ and Pb2+ was determined by plotting the amount of Cd2+ and Pb2+ adsorbed by the biomass (qe ) against equilibrium concentration (ce) in solution. The adsorption equilibrium data was fitted to both the Freundlich and Langmuir adsorption isotherm models (Lin and Jung, 2009).

The equilibrium sorption of the Pb2+ and Cd2+ was carried out by contacting 0.1 g of the adsorbents derived from kernels with 50 cm3 of 1000 mg/L of different concentrations from 20 mg/L to 160 mg/L in 100 cm3 plastic containers placed in a water bath rotator shaker for 60 minutes. The mixture was filtered and the filtrate analyzed for metal ions concentration using AAS. The data was fitted into both the

Langmuir and Freundlich isotherms.

3.11 Turbidity removal

Turbidity is a measure of water clarity, how suspended material in water decreases the passage of light through the water. The procedure was as follows:-

The turbidity meter was prepared according to the manufacturer’s instructions and then calibrated to ensure accurate readings in the working range. The sample was shaken vigorously until the bubbles disappeared. A lint-free cloth was used to wipe the outside of the tube into which the sample was poured making sure that the tube below line where light would pass was not touched. The sample water was poured into the tube and any drops on the outside of the tube wiped. The meter was set for appropriate turbidity range and then placed in the meter after which the turbidity was read. The readings were recorded and procedure repeated for every sample measured

(Ginting and Mamo, 2006).

Turbid water was drawn from Ruiru River using bottles and transported to the laboratory. Batch experiments were done with four adsorbents (MKAC, MKA, MKC and MBM). 50 cm3 of turbid water was agitated with 0.1 g of the adsorbents for 60 minutes at a constant shaking speed of 120 rpm at 25ºC. The samples were filtered into clean plastic containers and turbidity measured using LP 2000 turbidity meter.

The procedure was repeated by varying the adsorbent dosage from 0.2 g, 0.3 g, 0.4 g and 0.5 g.

3.12 Instrumentation

Atomic absorption spectrophotometer (AAS) was used to determine adsorption of

Pb2+ and Cd2+ ions from samples. A turbidity meter was used to determine turbidity removal while a pH meter was used to measure the pH of the adsorbent and when varying the pH of the samples. The samples were placed in a rotator shaker while carrying out the adsorption studies.

3.13 Data presentation and analysis

The data was presented in tables and graphs. The data on effects of concentration of metal ions on percentage removal was fitted to both the Freundlich and Langmuir adsorption isotherms.

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1 Sorption experiments

The effects of contact time, initial concentration of metal ions, dosage, temperature and pH on biosorption of Pb2+ and Cd2+ by products derived from M. indica kernels is discussed. The five parameters of adsorption were studied using four adsorbents namely; MKAC,MKC, MKA and MBM. The adsorption of activated carbon was compared with that of unmodified carbon, ash and the M. indica kernel biomass. The equilibrium data was fitted in both the Langmuir and Freundlich isotherms and interpretation made. Graphs showing the percentage removal of Pb2+ and Cd2+ from wastewater are discussed and the raw data presented in appendices 19 and 20

4.1.1 Effects of contact time

Appendix 21 shows experimental results on effect of varying the contact time on percentage removal of Pb2+ and Cd2+ using MKAC, MKC, MKA and MBM while keeping the other parameters of adsorption constant. The studies were done at a shaking speed of 120 rpm in a water bath shaker and an initial metal concentration of

80 mg/L. The results showed that the amount of metal ions adsorbed by the adsorbents increased with increase in time of equilibration and reached a maximum of

93.25% in 60 minutes using MKAC, 87.5% in 60 minutes with MKC, 96.75% with

MKA in 60 minutes and 61.75% in 80 minutes with MBM for Pb2+. Figure 4.1 shows the comparison of percentage removal of Pb2+ against contact time

120 110 100

90 MKAC 80 MKC

%Removal 70 MKA 60 MBM 50 40 0 20 40 60 80 100 120 Time (minutes)

Figure 4.1: Percentage removal of Pb2+ ions versus contact time at 25ºC, 80 mg/L and dosage of 1g

There was a gradual increase in percentage Pb2+ removal when the contact time was increased from 20 minutes to 100 minutes. MKAC had a percentage removal increasing from 86.5 to 93.25 when contact time was increased from 20 to 60 minutes. After 60 minutes the percentage removal remained almost constant.

Percentage Pb2+ removal increased from 88.25 to 96.75 for MKA and 76.5 to 87.5 for

MKC when the contact time was varied from 20 to 60 minutes after which it remained constant. When the contact time was increased from 20 to 80 minutes the percentage removal increased from 41.00 to 61.75 with MBM.

Figure 4.2 shows comparison of percentage removal of Cd2+ against time.

120

110

100

90 MKAC

80 MKC % Removal MKA 70 MBM 60

50 0 20 40 60 80 100 120 Time (Minutes)

Figure 4.2: Percentage removal of Cd2+ ions versus contact time at 25ºC, 80 mg/L and a dosage of 1g

When the experiment was repeated with Cd2+ ions the percentage removal increased from 84.26 to 95.15 when MKAC was used and time increased from 20 to 60 minutes. With MKC the removal increased from 81.65% to 83.16% when time was changed from 20 to 80 minutes after which the percentage removal remained constant. With MKA the percentage removal increased from 92.65 to 98.93 when the contact time was varied from 20 to 60 minutes. When MBM was used there was a gradual increase in percentage removal from 62.35 to 71.65 when contact time was increased from 20 to 80 minutes. This showed that the optimum contact time was 60 minutes for MKAC, MKC and MKA, while that of MBM had a higher period of 80 minutes.

The high percentage removal at low contact time was probably due to initial concentration gradient between the adsorbate in solution and the number of vacant sites available on the surface at the beginning. The progressive increase in adsorption

37 and consequently the attainment of equilibrium was due to limited mass transfer of the adsorbate molecules from the bulk liquid to the external surface of the adsorbents.

According to Sadon et al. (2012), it has been revealed that during initial stages of adsorption, a large number of vacant sites are available for adsorption. After some time, the remaining vacant sites have difficulty in becoming occupied because of repulsive forces between the adsorbate molecules on the solid surface and in the bulk phase. Theoretically, the equilibrium time is the time when the equilibrium occurs between the metal ions in the wastewater and in the adsorbent state. Similar observations were made by Wongjunda and Saueprasearsit, (2010) who reported that the rate of Cr6+ adsorption was found to gradually increase when the time was increased from 0 to 180 minutes. Thereafter the removal of Cr6+ ions was almost constant.

4.1.2 Effects of initial concentration on metal ions

Varying concentrations of Pb2+ and Cd2+ ions were contacted with the four adsorbents for 60 minutes and the sample solutions were analyzed using AAS to determine the percentage adsorption of the ions. The initial metal concentration provides an important driving force to overcome all mass transfer resistance of metal between the aqueous and solid phases (Wasewar, 2010). At equilibrium the remaining metal ions concentration in each case was determined and the results recorded in appendix 22

(a). The data of percentage removal versus concentration of lead (II) ions are given in figure 4.3.

110 100 90

80 MKAC 70 MKC

% Removal % 60 MKA 50 MBM 40 0 50 100 150 200 concentration (ppm)

Figure 4.3: Percentage removal for Pb2+ ions versus concentration at 25ºC, 60 minutes and dosage of 1g

Figure 4.3 shows how percentage removal of Pb2+ ions adsorbed as saturation varied when initial concentration were varied from 20 mg/L to 160 mg/L for MKAC, MKC,

MKA and MBM. From the results there was a change in percentage removal with change in initial metal concentration. When 0.1 g of the adsorbents was used, there was a corresponding decrease in percentage removal in MKAC, MKC, MKA and

MBM from 95% to 89.2%, 91% to 80.71%, 98% to 93.8% and 81% to 48.2%. MKA was however found to be the best adsorbent removing up to 93.8% of Pb2+ ions at 80 mg/L of initial metal concentration while MBM gave the least of upto 50% at 125 mg/L. The study was repeated with Cd2+ ions and the results are recorded in appendix

22 (b).

Figure 4.4 shows comparison of percentage removal against concentration of Cd2+ ions.

120 110 100

90 MKAC

80 MKC % Removal % 70 MKA 60 MBM 50 0 50 100 150 200

Concentration (ppm)

Figure 4.4: Percentage removal of Cd2+ ions versus concentration at 25ºC, 60 minutes and dosage of 1g

From figure 4.4, the percentage removal decreased with increase in concentration of metal ions. The percentage removal of MKAC decreased from 97.56 to 86.76, MKC decreased from 92.67 to 74.33, MKA decreased from 99.72 to 91.34 while that of

MBM decreased from 81.22 to 60.25. It may be concluded that the adsorbents had the highest percentage removal when the initial metal concentration was 20 mg/L for both Pb2+ and Cd2+ ions.

The results show that the metal ions uptake tended to saturate as the initial concentration was increased. This may be explained by a progressive increase in electrostatic mutual interaction between sites that had lower affinity for metal ions as the population of occupied sites increased. At low ion concentrations the ratio of surface active sites to the total metal ions in the solution was high and hence all metal ions interacted with the adsorbent and removed from solution. The initial concentration provided an important driving force to overcome all mass transfer resistance of metal ions between the aqueous and solid phases (Malkoc and Nuhoglu,

2005). This driving force for biosorption is the concentration difference between the metal ions on the adsorbent and the metal ions in solution. However, the amount of metal adsorbed per unit weight was higher at high concentrations.

4.1.3 Effects of dosage

The dosage of the adsorbents was varied from 0.1 g to 0.5 g and 80 mg/L of the metal ions agitated with the four adsorbents. The experiments were done at 25º C with a pH of 6 with a contact time of 60 minutes for MKAC, MKC, MKA and MBM. The results for Pb2+ ions are in appendix 23 (a).

120

110

100

90 MKAC

80 MKC % Removal % 70 MKA

60 MBM

50 0 0.1 0.2 0.3 0.4 0.5 0.6

Dosage (g)

Figure 4.5: Percentage removal of Pb2+ ions versus dosage at 25ºC, 80 mg/L and 60 minutes

The results showed that as the adsorbent doses increases, the percentage removal of

Pb2+ ions increased for all the four adsorbents as in figure 4.5. A gradual increase in percentage removal from 89.25% to 95.5% was noted when the dosage increased from 0.1 g to 0.2 g for MKAC. Above this dosage there was no significant increase in percentage removal. This shows that even at low dosage MKAC had a high

41 adsorption capacity. MKC showed an increase in percentage removal from 80.25 to

85.23 when the dosage was increased from 0.1 g to 0.3 g. The percentage removal in

MKA changed from 90.25 to 97.00 when the dosage was changed from 0.1 g to 0.2 g.

Above this dosage there was no change in percentage removal of Pb2+ ions. With

MBM there was a gradual increase in percentage removal from 56.25 to 73.25 when the dosage was increased from 0.1 g to 0.4 g. The experiments were repeated by agitating 50 cm3 of solution containing Cd2+ ions.

The data for the comparison of percentage removal of Cd2+ as the dosage was varied was presented in figure 4.6

110

100

MKAC 80

MKC % removal% 70 MKA MBM 60

50 0 0.1 0.2 0.3 0.4 0.5 0.6

Dosage (g)

Figure 4.6: Percentage removal of Cd2+ ions versus dosage at 25ºC, 80 mg/L and 60 minutes

As the adsorbent dosage was increased a similar trend with that of adsorption of Pb2+ was found. Percentage removal of metal ions increased with increase in adsorbent dosage. The percentage removal by MKAC increased from 88.45 to 93.63 when the

42 dosage was increased from 0.1 g to 0.3 g. For MKC the percentage removal increased from 76.67 to 86.22 and then decreased to81.67 at a dosage of 0.5 g, in MKA the increase was from 95.3 to 97.4 while in MBM the increase was from 56.54 to 72.21.

There was no significant increase in percentage removal with MKA above a dosage of 0.1 g. The increase in percentage removal when the dosage was increased from 0.1 g to 0.5 g was due to increase in the number of available adsorption sites for metal attachment (Abdel et al., 2007). The increase in percentage removal can also be due to unsaturation of adsorption sites through the adsorption process.

According to Bishnoi et al. (2004) a high adsorbent dosage can impose a screening effect on the dense outer layer of the cells leading to shielding of the adsorption site from metal ions. This may lead to decrease in percentage removal. Another reason for decrease or no change in percentage removal is due to partial interaction, such as aggregation which would lead to decrease in total surface area of the adsorbents and an increase in diffusion path length (Sadon et al., 2012). In some cases the amount of metal ions adsorbed per unit weight of adsorbent (q) decreases with the adsorbent dose. This is due to the fact that at higher adsorbent dose the solution ion concentration drops to a lower value and the system reaches equilibrium at lower values of ‘q’ indicating the adsorption sites remain unsaturated (Wasewar, 2010).

4.1.4 Effects of temperature

The experiments were done at temperature intervals of 10o C from 25º C to 65º C using a dosage of 0.1 g , pH of 6 and an initial metal concentration of 80 mg/L for the four adsorbents. The results are given in appendix 24.

Figure 4.7 shows the comparison between the four adsorbents when the temperature was varied from 25º C to 65º C.

110

100

90 MKAC 80 MKC % Removal % 70 MKA 60 MBM

50 0 10 20 30 40 50 60 70

Temperature (ºC)

Figure 4.7: Percentage removal of Pb2+ versus temperature at 80 mg/L, 60 minutes and dosage of 1 g

The percentage removal of Pb2+ ions by MKAC increased from 89.5 to 95.25 when the temperature was increased from 25ºC to 45ºC and then dropped to 90.22 when the temperature was increased to 65º C as shown in figure 4.7. The percentage removal when MKC was used increased from 83.34% to 90.25% at 45ºC and then dropped to

84.25% when temperature increased to 65º C. There was a very small change in percentage removal using MKA since it only changed from 98.25% to 98.75% when the temperature was increased from 25ºC to 45ºC. Above this temperature however,the three adsorbents did not show a significant change in percentage removal. Increased temperature led to a slight decrease in percentage removal. Thus the temperature of 45ºC was the optimum temperature for adsorption of Pb2+ ions.

When MBM was used it was found that an increase in temperature produced a

44 significant change in the percentage removal of Pb2+ ions. Increased temperature from

25ºC to 65ºC resulted in increase in the percentage adsorption from 59.75 to 67.25.

When the experiment was repeated with Cd2+ ions a similar trend was observed.

Figure 4.8 shows the effect on percentage removal of Cd2+ ions with variation of temperature.

110

100

MKAC 80

MKC % Removal % 70 MKA MBM 60

50 0 10 20 30 40 50 60 70

Temperature (ºC)

Figure 4.8: Percentage removal of Cd2+ ions versus temperature at 80 mg/L,60 minutes and dosage of 1 g

There was increased percentage adsorption of Cd2+ ions of 86.32 to 94.89 by MKAC with temperature rise from 25º C to 45ºC then dropped to 89.19 at 65º C. With MKC the percentage removal increased from 78.33 to 82.78 at 35ºC after which the percentage removal dropped slightly and remained almost constant. Adsorption using

MKA led to an increase in the percentage removal from 94.36 to 97.57 when the temperature was raised from 25ºC to 35ºC and then decreased gradually to 92.93 at

65ºC. There was a gradual increase in percentage removal when MBM was used and temperature varied from 25º to 65ºC. The percentage removal increased from 55.29 to about 72.00. Increase in adsorption with increase in temperature may be attributed to

45 increase in penetration of metal ions inside the micopores of adsorbent at high temperatures or the creation of new active sites (Yahya et al., 2007). At higher temperatures the mobility of metal ions is enhanced resulting in higher adsorption capacity. Since adsorption is an exothermic process at high temperatures the percentage removal decreases.

4.1.5 Effects of pH

Percentage removal of metal ions was plotted against the pH of the solution and the results recorded in appendix 25.

120

110

100

90 MKAC

80 MKC % Removal % 70 MKA

60 MBM

50 0 2 4 6 8 10

Figure 4.9: Percentage removal of Pb2+ ions versus pH at 25ºC, 60 minutes and dosage of 1 g

The percentage removal of Pb2+ ions using MKAC increased from 83.00 to 96.25 when the pH was adjusted from 2 to 6 as shown in figure 4.9. Thereafter the percentage removal remained constant up to pH of 8. Application of MKC gave a similar trend with the percentage removal increasing from 72.00 to 89.00 at a pH of 6.

With MBM the percentage removal increased gradually from 58.25 to 65.25 with the pH rise of 2 to 6. There was however, no significant change in percentage removal

46 when the pH was varied with MKA adsorbent. The experiments were repeated with

Cd2+ ions and results obtained are given in figure 4.10.

110

100

MKAC 80

MKC % Removal % 70 MKA MBM 60

50 0 2 4 6 8 10

Figure 4.10: Percentage removal of Cd2+ ions versus pH of solution at 25ºC, 60 minutes and dosage of 1 g

The percentage removal of Cd2+ ions using MKAC rose from 77.50 to 92.39 with the pH variation from 2 to 6. Percentage removal remained unaffected with pH adjustment to 8. The same trend was observed for MKC, MKA and MBM. With

MKC, the percentage removal increased from 68.29 to 83.68 at pH 6 while application of MKA led to increased percentage removal from 84.67 to 99.74 at pH 6 with consequential constant percentage removal up to pH 8. Adsorption involving

MBM resulted in increased percentage removal from 52.44 to 65.76 when the pH was adjusted from 2 to 6 after which it remained constant.

Generally, metal ions are more soluble at lower pH values and this enhances their adsorption as reported by Olayinka et al., (2009). The pH of the feed solution is an

47 important controlling parameter in heavy metal adsorption process and thus the role of hydrogen ion. The pH is an important variable in the ion exchange governed adsorption process by which surface charges may be changed or modified. Cay et al.

(2004) observed that the adsorption percentages are very low at strong acidic medium. When concentration of hydrogen ions decreases at high pH, the competition for adsorption sites between the metal ions and hydrogen decreases resulting in high percentage removal of the metal ions. The optimum pH for removal of Pb2+ and Cd2+ ions was found to be 6.

4.2 Freundlich and Langmuir adsorption isotherm constants

The Langmuir and Freundlich adsorption isotherm constants were calculated from the intercept and slope. The physical parameters obtained from the isotherms for Pb2+ and

Cd2+ ions are presented in tables 4.1 and 4.2, respectively.

Table 4.1: Langmuir and Freundlich constants for Pb2+ ions Langmuir Freundlich 2 2 Adsorbent Adsorption KL R RL Adsorption 1/n R capacity value capacity value MKAC 71.43 0.15 0.969 0.06 8.73 0.702 0.989 MKC 66.67 0.09 0.972 0.08 5.69 0.685 0.993 MKA 80.31 0.43 0.974 0.02 9.69 0.6 0.978 MBM 35.71 0.08 0.983 0.09 4.69 0.457 0.977

As shown in table 4.1, sorption data for Pb2+ ions fitted best into Freundlich isotherm based on the corresponding R2 values of 0.989, 0.993 and 0.978 for MKAC,MKC and

MKA and 1/n values of 0.702, 0.685, 0.6 and 0.457 for MKAC, MKC, MKA and

MBM, respectively. 1/n values of < 1 imply a normal adsorption. Based on the

Freundlich model the adsorption surface is heterogeneous. The respective adsorption capacities were 8.73, 5.69 and 9.69 for MKAC,MKC and MKA. However, MBM

48 adsorption fitted well in the Langmuir adsorption isotherm with R2 value of 0.983 implying mono layer adsorption.

The separation factor (RL) indicates the adsorption nature to be either unfavourable if

RL > 1, linear if RL=1, favourable if 0< RL <1 and irreversible if RL=0. From the data calculated in table 4.1, the corresponding RL of 0.06, 0.08, 0.02 and 0.009 for

MKAC,MKC MKA and MBM imply favourable adsorption for Pb2+ ions.

Table 4.2: Langmuir and Freundlich constants for Cd2+ ions Langmuir Freundlich 2 2 Adsorbent Adsorption KL R RL Adsorption 1/n R value capacity value capacity MKAC 57.62 0.51 0.93 0.04 12.76 0.503 0.974 MKC 47.62 0.16 0.953 0.05 7.13 0.541 0.987 MKA 83.33 0.17 0.8 0.06 12.71 0.62 0.914 MBM 45.45 0.06 0.997 0.11 3.8 0.597 0.994

Table 4.2 shows the Freundlich and Langmuir constants for Cd2+ ions adsorption. The sorption data fitted best in the Freundlich adsorption isotherm with respective R2 of

0.974, 0.987 and 0.914 for MKAC,MKC and MKA. The corresponding adsorption capacities were 12.76, 7.13 and 12.71 for MKAC, MKC and MKA. The respective RL values were 0.04, 0.03, 0.06 and 0.11 for MKAC,MKC,MKA and MBM showing that the adsorption was favourable. The corresponding 1/n values were 0.503, 0.541 and

0.62 for MKAC,MKC and MKA and adsorption proceded by the Freundlich model having a heterogenous surface. However,the R2 value for MBM of 0.997 fitted well in the Langmuir adsorption isotherm model with adsorption capacity of 45.45.

4.3 Turbidity removal

The raw data on turbidity removal are presented in appendices 28 and 29. The dosage of the four adsorbents were varied from 0.1 g to 0.5 g.

Figure 4.11 shows a comparison of turbidity removal when the dosage of adsorbent was varied

120

100

80 MKAC

60 MKC MKA %Removal 40 MBM 20

0 0 0.1 0.2 0.3 0.4 0.5 0.6 Dosage (g)

Figure 4.11: Percentage turbidity removal versus dosage at 25ºC, shaking speed of 120 rpm and contact time of 60 minutes

The corresponding percentage turbidity removal for MKAC, MKC, MKA and MBM increased from 36.99 to 54.82, 21.46 to 31.63, 96.26 to 97.37 and 38.94 to 59.97.

MKA was however, found to be a better adsorbent for turbidity removal at even very low dosage of 0.1 g with a percentage removal of 96.26.

CHAPTER FIVE

CONCLUSION AND RECOMMENDATIONS

5.1 Conclusions

From the results obtained it was concluded that

 Mangifera indica kernel can be used as a precursor material for development

of a biosorption technology for the removal of lead and cadmium ions from

aqueous system. Charcoal, activated carbon, ash and biomass derived from M.

indica kernel had a high percentage removal of Pb2+ and Cd2+ from

wastewaters. However, efficiency of adsorbents to remove metal ions from

wastewater was affected by contact time, initial metal concentration, dosage,

pH and temperature.

 The adsorbents derived from M. indica kernels had high adsorption capacity

in removal of metal ions. The maximum adsorption capacity were 8.73 mg/g,

5.69 mg/g, 9.69 mg/g and 4.69 mg/g for MKAC, MKC, MKA and MBM

respectively, for Pb2+. The adsorption capacities for Cd2+ was 12.76 mg/g 7.13

mg/g, 12.71 mg/g and 3.8 mg/g for MKAC, MKC, MKA and MBM

respectvely. The adsorption data fitted well in the Freundlich adsorption

isotherm for MKAC,MKC and MKA which indicated that adsorption surface

was heterogenous. However, MBM fitted in the Langmuir adsorption

isotherm indicating that the ion exchange took place at the surface of the

adsorbent.

 M. indica kernel adsorbents had a high coagulation capacity towards removal

of turbidity.

5.2 Recommendations

The study did not deal with optimization conditions for preparation of the activated carbon. Also characterization of the absorbents was not done and therefore it is recommended that this should be done to identify the surface properties that enable these adsorbents to remove metal ions. Further recommendations:

i. Studies should be conducted on effects of mesh size and shaking speed on

percentage removal of metal ions.

ii. Adsorption studies on adsorption of organic contaminants like phenols and

malathion should be done.

iii. Modification of mangifera indica kernel biomass for adsorption studies

should be taken.

iv. Feasibility study should be done to determine whether the adsorbents can be

applied in purification of wastewater from industrial effluents.

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Appendices

Appendix 1: Calibration curves for Pb2+ ions

0.06 y = 0.0058x - 0.0068 0.05 R² = 0.9953 0.04

0.03 Series1 Linear (Series1)

absorbance 0.02

0.01

0 0 2 concentration4 of6 metal ions8 (ppm) 10 12

Appendix 2: Calibration curve for Cd2+ ions

0.5 y = 0.0348x + 0.0481

0.4 R² = 0.9898

0.3 Series1 0.2

Linear (Series1) absorbance 0.1

0 0 2 4 6 8 10 12 concentration of metal ion (ppm)

Appendix 3: Langmuir adsorption isotherms for Pb2+ for MKAC

0.12 MKAC (Lead) y = 0.094x + 0.014 0.1 R² = 0.969

0.08

0.06 1/Qe 1/Qe 0.04 Linear (1/Qe)

0.02

0 0 0.2 0.4 0.6 0.8 1 1.2

1/Ce

Appendix 4: Langmuir adsorption isotherm for Pb2+ for MKC

0.12 MKC (Lead) y = 0.176x + 0.015 0.1 R² = 0.972

0.08

0.06 1/Qe 1/Qe 0.04 Linear (1/Qe)

0.02

0 0 0.1 0.2 0.3 0.4 0.5 0.6

1/Ce

Appendix 5: Langmuir adsorption isotherm for Pb2+ on MKA

0.12 MKA (Lead) y = 0.035x + 0.015 0.1 R² = 0.974

0.08

0.06

1/Qe 1/Qe 0.04 Linear (1/Qe)

0.02

0 0 1 2 3

1/Ce

Appendix 6: Langmuir adsorption isotherm for Pb2+ on MBM

0.14 MBM (Lead) 0.12 y = 0.366x + 0.028 R² = 0.983 0.1

0.08

1/Qe 0.06 1/Qe

0.04 Linear (1/Qe)

0.02

0 0 0.05 0.1 0.15 0.2 0.25 0.3

1/Ce

Appendix 7: Freundlich adsorption isotherm for Pb2+ on MKAC

2 MKAC (Lead) 1.8 y = 0.702x + 0.941 1.6 R² = 0.989 1.4 1.2 1

Log Qe Log 0.8 Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 0 0.5 1 1.5

Log Ce

Appendix 8: Freundlich adsorption isotherm for Pb2+ ions on MKC

2 MKC (Lead) 1.8 y = 0.685x + 0.755 1.6 R² = 0.993 1.4 1.2 1

Log Qe Log 0.8 Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 0 0.5 1 1.5 2

Log Ce

Appendix 9: Freundlich adsorption isotherm for Pb2+ ions on MKA

2 MKA (Lead) 1.8 1.6 y = 0.600x + 1.220 R² = 0.978 1.4 1.2

Log Qe Log Log Qe 1 Linear (Log Qe) 0.8 0.6 0.4 -0.5 0 0.5 1 1.5

Log Ce

Appendix 10: Freundlich adsorption isotherm for Pb2+ ions on MBM

1.8 MBM (Lead) y = 0.457x + 0.671 1.6 R² = 0.977 1.4 1.2 1 0.8 Log Qe Log Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 0 0.5 1 1.5 2 2.5

Log Ce

Appendix 11: Langmuir adsorption isotherm for Cd2+ ions on MKAC

0.12 MKAC (cadmium) y = 0.041x + 0.021 0.1 R² = 0.930 0.08

0.06 1/Qe 1/Qe 0.04 Linear (1/Qe)

0.02

0 0 0.5 1 1.5 2 2.5

1/Ce

Appendix 12: Langmuir adsorption isotherm for Cd2+ ion on MKC

MKC (Cadmium) 0.12 y = 0.132x + 0.021 0.1 R² = 0.953 0.08

0.06 1/Qe 1/Qe 0.04 Linear (1/Qe) 0.02

0 0 0.2 0.4 0.6 0.8

1/Ce

Appendix 13: Langmuir adsorption isotherm for Cd2+ ions on MKA

0.12 MKA (Cadmium)

0.1 y = 0.069x + 0.012 0.08 R² = 0.800

0.06 1/Qe 1/Qe 0.04 Linear (1/Qe)

0.02

0 0 0.2 0.4 0.6 0.8 1 1.2

1/Ce

Appendix 14: Langmuir adsorption isotherm for Cd2+ ions on MBM

MBM (Cadmium) 0.14 0.12 y = 0.382x + 0.022 R² = 0.997 0.1 0.08

1/Qe 0.06 1/Qe 0.04 Linear (1/Qe) 0.02 0 0 0.05 0.1 0.15 0.2 0.25 0.3

1/Ce

Appendix 15: Freundlich adsorption isotherm for Cd2+ ions on MKAC

MKAC (Cadmium)

2 1.8 y = 0.503x + 1.106 1.6 R² = 0.974 1.4 1.2 1

Log Qe Log 0.8 Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 -0.5 0 0.5 1 1.5

Log Ce

Appendix 16: Freundlich adsorption isotherm for Cd2+ ions on MKC

MKC (Cadmium) 2 1.8 y = 0.541x + 0.853 1.6 R² = 0.987 1.4 1.2 1

Log Qe Log 0.8 Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 0 0.5 1 1.5 2

Log Ce

Appendix 17: Freundlich adsorption isotherm for Cd2+ ions on MKA

2 MKA (Cadmium) 1.8 y = 0.620x + 1.104 1.6 R² = 0.914 1.4 1.2 1

Log Qe Log 0.8 Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 0 0.5 1 1.5

log Ce

Appendix 18: Freundlich adsorption isotherm for Cd2+ ions on MBM

MBM (Cadmium) 1.8 1.6 y = 0.597x + 0.580 1.4 R² = 0.994 1.2 1 0.8 Log Qe Log Log Qe 0.6 Linear (Log Qe) 0.4 0.2 0 0 0.5 1 1.5 2

Log Ce

Appendix 19: Raw data for Pb2+ ions

1. Contact time

MKAC

Time Average A1 A2 A3 Ce Sd % (min) absorbance Removal 20 0.048 0.047 0.048 0.049 10.8 0.0010 86.5 40 0.033 0.033 0.033 0.032 7.82 0.0006 90.25 60 0.021 0.022 0.023 0.018 5.41 0.0026 93.25 80 0.022 0.022 0.023 0.023 5.6 0.0006 93 100 0.022 0.021 0.022 0.023 5.6 0.0010 93

MKC

Time Average A1 A2 A3 Ce Sd % (min) absorbance Removal 20 0.088 0.088 0.087 0.087 18.8 0.0006 76.5 40 0.064 0.066 0.062 0.064 14 0.0020 82.1 60 0.044 0.044 0.043 0.044 10 0.0006 97.5 80 0.044 0.044 0.043 0.044 10 0.0006 97.5 100 0.044 0.044 0.044 0.043 10 0.0006 97.5

MKA

Time Average A1 A2 A3 Ce Sd % (Min) absorbance Removal 20 0.041 0.042 0.041 0.041 9.4 0.0006 88.25 40 0.025 0.025 0.024 0.026 6.2 0.0010 92.25 60 0.007 0.008 0.006 0.007 2.6 0.0010 96.75 80 0.007 0.005 0.006 0.01 2.6 0.0026 76.75 100 0.007 0.006 0.007 0.008 2.6 0.0010 96.75

MBM

Time Average A1 A2 A3 Ce Sd % (Min) absorbance Removal 20 0.23 0.213 0.239 0.238 47.2 0.0147 41 40 0.191 0.196 0.19 0.188 39.4 0.0042 50.75 60 0.167 0.167 0.167 0.168 34.6 0.0006 56.75 80 0.147 0.146 0.148 0.147 30.6 0.0010 61.75 100 0.147 0.147 0.148 0.147 30.6 0.0010 61.75

2. concentration of metal ions

MKAC

Concent.(mg/L) Average A1 A2 A3 Ce sd % absorbance Removal 20 0.001 0.001 0.001 0.001 1 0.0 95 40 0.012 0.011 0.011 0.013 3.13 0.0012 92.17 60 0.024 0.024 0.023 0.024 5.33 0.0006 90.78 80 0.037 0.037 0.039 0.036 8.27 0.0015 89.67 100 0.051 0.053 0.051 0.049 11 0.0020 89 120 0.061 0.061 0.062 0.059 12.93 0.0015 89.22 140 0.072 0.071 0.074 0.07 15.13 0.0021 89.2 160 0.082 0.082 0.084 0.081 17.27 0.0015 89.2

MKC

Concent.(mg/L) Average A1 A2 A3 Ce Sd % absorbance Removal 20 0.005 0.005 0.008 0.002 1.8 0.0030 91 40 0.023 0.023 0.023 0.022 5.33 0.0006 86.67 60 0.045 0.041 0.047 0.042 9.73 0.0032 83.78 80 0.065 0.065 0.068 0.062 13.1 0.0030 82.75 100 0.088 0.088 0.089 0.086 18.33 0.0015 81.67 120 0.112 0.111 0.111 0.113 23.13 0.0012 80.72 140 0.131 0.131 0.134 0.128 27 0.0030 88.71 160 0.15 0.15 0.151 0.15 30.8 0.0006 80.71

MKA

Concent.(mg/L) Average A1 A2 A3 Ce Sd % absorbance Removal 20 0.001 0.001 0.001 0.001 0.4 0.0 98 40 0.002 0.002 0.001 0.003 1.2 0.0010 97 60 0.009 0.009 0.008 0.01 2.65 0.0010 95.67 80 0.023 0.023 0.026 0.02 5.4 0.0030 93.25 100 0.027 0.027 0.029 0.025 6.25 0.0020 93.8 120 0.033 0.033 0.034 0.032 7.4 0.0010 93.8 140 0.039 0.039 0.036 0.043 8.68 0.0035 93.8 160 0.045 0.046 0.048 0.042 9.92 0.0031 93.8

MBM

Concent.(mg/L) Average A1 A2 A3 Ce Sd % absorbance Removal 20 0.015 0.015 0.017 0.013 3.8 0.0020 81 40 0.047 0.047 0.049 0.045 10.2 0.0020 74.5 60 0.097 0.097 0.096 0.098 20.62 0.0010 66.33 80 0.165 0.168 0.162 0.165 33.8 0.0030 57.75 100 0.243 0.243 0.246 0.24 49.4 0.0030 50.6 120 0.307 0.307 0.309 0.304 62.13 0.0025 48.2 140 0.359 0.358 0.356 0.362 72.53 0.0031 48.2 160 0.411 0.412 0.409 0.411 82.93 0.0015 48.2

3. Dosage

MKAC

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.039 0.038 0.039 0.040 8.6 0.0010 89.25 0.2 0.014 0.013 0.016 0.013 3.6 0.0017 95.50 0.3 0.015 0.014 0.012 0.019 3.8 0.0036 95.25 0.4 0.015 0.014 0.016 0.015 3.8 0.0010 95.25 0.5 0.016 0.014 0.014 0.020 4.0 0.0035 95.00

MKC

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.075 0.078 0.076 0.071 15.8 0.0036 80.25 0.2 0.062 0.061 0.063 0.062 13.2 0.0010 83.5 0.3 0.055 0.053 0.054 0.054 11.8 0.0006 85.25 0.4 0.055 0.057 0.054 0.054 11.8 0.0017 85.25 0.5 0.055 0.058 0.055 0.052 11.8 0.0030 85.25

MKA

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.035 0.034 0.035 0.035 7.80 0.0006 90.25 0.2 0.008 0.006 0.009 0.009 2.40 0.0017 97.00 0.3 0.008 0.008 0.009 0.007 2.40 0.0010 97.00 0.4 0.008 0.005 0.008 0.011 2.40 0.0030 97.00 0.5 0.011 0.012 0.014 0.007 3.00 0.0036 96.25

MBM

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.171 0.170 0.172 0.171 35.00 0.0010 56.25 0.2 0.130 0.110 0.140 0.14 26.80 0.0170 66.50 0.3 0.114 0.116 0.113 0.113 23.60 0.0017 70.50 0.4 0.103 0.105 0.104 0.100 21.40 0.0026 73.25 0.5 0.103 0.102 0.104 0.103 21.40 0.0010 73.25

4. Temperature

MKAC

Temp.(ºC) Average A1 A2 A3 Ce Sd % absorbance Removal 25 0.038 0.038 0.039 0.037 8.40 0.0010 89.50 35 0.023 0.021 0.025 0.023 5.40 0.0020 93.25 45 0.015 0.012 0.016 0.017 3.80 0.0026 95.25 55 0.026 0.025 0.027 0.026 6.00 0.0010 92.50 65 0.035 0.033 0.037 0.035 7.80 0.0020 90.25

MKC

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 0.062 0.061 0.064 0.061 13.20 0.0017 83.50 35 0.051 0.054 0.051 0.048 11.00 0.0030 86.25 45 0.035 0.038 0.032 0.035 7.800 0.0030 90.25 55 0.045 0.044 0.046 0.045 9.800 0.0010 87.75 65 0.059 0.056 0.058 0.063 12.60 0.0036 84.25

MKA

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 0.003 0.003 0.003 0.002 1.4 0.0006 98.25 35 0.002 0.002 0.002 0.003 1.2 0.0006 98.50 45 0.001 0.001 0.002 0.001 1.0 0.0006 98.75 55 0.002 0.002 0.002 0.002 1.2 0.0000 98.50 65 0.006 0.004 0.008 0.006 2.0 0.0020 97.50

MBM

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 0.157 0.156 0.158 0.157 32.2 0.0010 59.75 35 0.150 0.140 0.170 0.140 30.8 0.0170 61.50 45 0.142 0.144 0.141 0.141 29.2 0.0017 63.50 55 0.129 0.124 0.131 0.133 26.6 0.0047 66.75 65 0.127 0.129 0.125 0.127 26.2 0.0020 67.25

5. pH

MKAC pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 0.064 0.065 0.064 0.063 13.6 0.0010 83.00 4 0.027 0.027 0.027 0.026 6.20 0.0006 92.25 6 0.011 0.010 0.011 0.011 3.00 0.0006 96.25 7 0.012 0.011 0.013 0.012 3.20 0.0010 96.00 8 0.012 0.014 0.011 0.011 3.20 0.0017 96.00

MKC pH Average A1 A2 A3 Ce Sd % Removal absorbance 2 0.108 0.107 0.108 0.108 22.4 0.0006 72.00 4 0.071 0.072 0.070 0.071 15.0 0.0010 81.25 6 0.040 0.030 0.060 0.030 8.80 0.0170 89.00 7 0.040 0.040 0.050 0.040 8.40 0.0060 89.00 8 0.040 0.070 0.020 0.030 8.80 0.0260 89.00

MKA pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 0.022 0.023 0.024 0.02 5.2 0.0021 93.5 4 0.002 0.002 0.002 0.003 1.2 0.0006 98.5 6 0.001 0.002 0.001 0.001 1.0 0.0006 98.75 7 0.002 0.002 0.002 0.003 1.2 0.0006 98.5 8 0.002 0.002 0.002 0.002 1.2 0.0000 98.5

MBM pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 0.163 0.164 0.162 0.163 33.4 0.0010 58.25 4 0.147 0.147 0.145 0.148 30.2 0.0015 62.25 6 0.133 0.134 0.130 0.135 27.4 0.0026 65.25 7 0.136 0.136 0.136 0.135 28.0 0.0006 65.00 8 0.136 0.135 0.138 0.135 28.0 0.0017 65.00

Appendix 20: Raw data for Cd2+ ions

1. Contact time

MKAC

Time Average A1 A2 A3 Ce Sd % (Min) absorbance Removal 20 0.476 0.421 0.422 0.423 11.00 0.0010 86.25 40 0.224 0.223 0.225 0.224 5.18 0.0010 93.53 60 0.180 0.181 0.180 0.180 3.88 0.0006 95.15 80 0.180 0.190 0.170 0.180 3.88 0.0100 95.15 100 0.180 0.180 0.180 0.190 3.88 0.0060 95.15

MKC

Time Average A1 A2 A3 Ce Sd % (Min) absorbance Removal 20 0.547 0.547 0.547 0.546 14.68 0.0006 81.65 40 0.545 0.546 0.544 0.545 14.62 0.0010 81.73 60 0.511 0.512 0.544 0.507 13.47 0.0201 83.16 80 0.506 0.506 0.505 0.507 13.47 0.0010 83.16 100 0.506 0.506 0.507 0.505 13.47 0.0010 83.16

MKA

Time Average A1 A2 A3 Ce Sd % (Min) absorbance Removal 20 0.248 0.248 0.247 0.249 5.88 0.0010 92.65 40 0.145 0.145 0.147 0.143 2.85 0.0020 96.43 60 0.077 0.077 0.076 0.075 0.85 0.0010 98.93 80 0.077 0.077 0.076 0.076 0.85 0.0006 98.93 100 0.077 0.077 0.076 0.077 0.85 0.0006 98.93

MBM

Time Average A1 A2 A3 Ce Sd % (Min) absorbance Removal 20 1.072 1.074 1.070 1.072 30.12 0.0020 62.35 40 0.988 0.989 0.989 0.986 27.65 0.0017 65.44 60 0.939 0.939 0.937 0.941 26.21 0.0020 67.24 80 0.819 0.819 0.819 0.821 22.68 0.0012 71.65 100 0.819 0.820 0.818 0.819 22.68 0.0010 71.63

2. Concentration of metal ions

MKAC

Concent. Average A1 A2 A3 Ce Sd %Removal (mg/L) absorbance 20 0.059 0.059 0.056 0.061 0.49 0.0025 97.56 40 0.112 0.112 0.114 0.110 2.27 0.0020 94.33 60 0.219 0.219 0.217 0.220 5.82 0.0015 90.29 80 0.324 0.324 0.326 0.322 9.33 0.0020 88.34 100 0.441 0.441 0.444 0.439 13.24 0.0025 86.76 120 0.521 0.521 0.523 0.518 15.89 0.0025 86.76 140 0.600 0.610 0.610 0.590 18.53 0.0015 86.76 160 0.679 0.679 0.677 0.682 21.18 0.0025 86.76

MKC

Concent. Average A1 A2 A3 Ce Sd % (mg/L) absorbance Removal 20 0.088 0.088 0.086 0.090 1.47 0.0020 82.67 40 0.197 0.197 0.198 0.197 5.11 0.0006 87.22 60 0.391 0.391 0.394 0.388 11.57 0.0030 81.72 80 0.562 0.562 0.563 0.556 17.26 0.0038 78.43 100 0.757 0.757 0.759 0.756 23.78 0.0015 76.22 120 0.968 0.968 0.969 0.967 30.80 0.0010 74.33 140 1.122 1.124 1.122 1.121 35.94 0.0015 74.33 160 1.276 1.275 1.276 1.277 41.07 0.0010 74.33

MKA

Concent. Average A1 A2 A3 Ce Sd % (mg/L) absorbance Removal 20 0.046 0.048 0.046 0.043 0.06 0.0025 99.72 40 0.076 0.076 0.074 0.078 1.07 0.0020 97.33 60 0.164 0.167 0.164 0.162 4.01 0.0025 93.31 80 0.252 0.25 0.251 0.252 6.93 0.0010 91.33 100 0.304 0.306 0.304 0.301 8.66 0.0025 91.34 120 0.356 0.353 0.358 0.356 10.39 0.0025 91.34 140 0.408 0.406 0.408 0.409 12.12 0.0015 91.34 160 0.459 0.461 0.459 0.459 13.86 0.0012 91.34

MBM

Concent. Average A1 A2 A3 Ce Sd % (mg/L) absorbance Removal 20 0.157 0.158 0.157 0.155 3.76 0.0015 81.22 40 0.322 0.324 0.322 0.320 9.27 0.0020 76.83 60 0.564 0.567 0.564 0.560 17.32 0.0035 71.13 80 0.855 0.854 0.855 0.851 27.02 0.0021 66.22 100 1.141 1.138 1.141 1.143 36.56 0.0025 63.44 120 1.475 1.475 1.478 1.472 47.70 0.0030 60.25 140 1.714 1.712 1.716 1.714 55.66 0.0020 60.25 160 1.952 1.952 1.950 1.954 63.60 0.0020 60.25

3. Dosage

MKAC

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.321 0.322 0.322 0.319 9.23 0.0017 88.45 0.2 0.232 0.234 0.231 0.233 6.29 0.0015 92.14 0.3 0.197 0.198 0.197 0.196 5.10 0.0010 93.63 0.4 0.197 0.198 0.197 0.196 5.10 0.0010 93.63 0.5 0.212 0.211 0.215 0.210 5.60 0.0026 93.00

MKC Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.604 0.602 0.603 0.607 18.67 0.0026 76.67 0.2 0.513 0.512 0.514 0.513 15.63 0.0010 80.46 0.3 0.374 0.372 0.373 0.379 11.02 0.0038 86.22 0.4 0.374 0.373 0.373 0.378 11.02 0.0029 86.22 0.5 0.484 0.487 0.479 0.486 14.67 0.0044 81.67

MKA

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 0.156 0.156 0.157 0.155 3.73 0.0010 95.3 0.2 0.106 0.105 0.108 0.107 2.07 0.0015 97.4 0.3 0.106 0.104 0.109 0.105 2.07 0.0026 97.4 0.4 0.106 0.102 0.106 0.110 2.07 0.0040 97.4 0.5 0.123 0.124 0.122 0.123 2.64 0.0010 96.7

MBM

Mass Average A1 A2 A3 Ce Sd % (g) absorbance Removal 0.1 1.087 1.086 1.087 1.088 34.77 0.0010 56.54 0.2 0.946 0.943 0.947 0.948 30.06 0.0026 62.43 0.3 0.795 0.793 0.795 0.797 25.03 0.0020 68.70 0.4 0.711 0.71 0.713 0.71 22.23 0.0017 72.21 0.5 0.711 0.714 0.712 0.707 22.23 0.0036 72.21

4. Temperature

MKAC

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 0.372 0.372 0.370 0.373 10.94 0.0015 86.32 35 0.266 0.267 0.264 0.263 7.59 0.0021 90.76 45 0.167 0.163 0.167 0.171 4.09 0.0040 94.89 55 0.217 0.217 0.219 0.217 5.77 0.0012 92.79 65 0.303 0.303 0.300 0.304 8.64 0.0021 89.19

MKC

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 0.564 0.563 0.564 0.566 17.33 0.0015 78.33 35 0.547 0.458 0.456 0.456 13.78 0.0012 82.78 45 0.499 0.498 0.499 0.502 15.20 0.0021 81.03 55 0.523 0.523 0.519 0.524 15.98 0.0026 80.03 65 0.532 0.532 0.533 0.531 16.26 0.0010 79.68

MKA

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 0.179 0.180 0.178 0.179 4.51 0.0010 94.36 35 0.102 0.102 0.103 0.103 1.94 0.0006 97.57 45 0.104 0.104 0.100 0.103 1.99 0.0021 97.51 55 0.155 0.155 0.156 0.155 3.70 0.0006 95.38 65 0.214 0.214 0.212 0.213 5.60 0.0010 92.93

MBM

Temp. Average A1 A2 A3 Ce Sd % (ºC) absorbance Removal 25 1.117 1.117 1.118 1.117 35.77 0.0006 55.29 35 0.972 0.972 0.973 0.972 30.94 0.0006 61.35 45 0.825 0.825 0.826 0.824 26.02 0.0010 67.47 55 0.724 0.724 0.722 0.725 22.68 0.0015 71.65 65 0.724 0.724 0.721 0.725 22.68 0.0021 71.65

5. pH

MKAC pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 0.584 0.577 0.589 0.586 18.00 0.0062 77.5 4 0.383 0.382 0.381 0.385 11.29 0.0021 85.89 6 0.227 0.230 0.240 0.210 6.090 0.0150 92.39 7 0.227 0.240 0.240 0.200 6.090 0.0230 92.39 8 0.227 0.210 0.250 0.220 6.090 0.0210 92.39

MKC pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 0.805 0.805 0.807 0.803 25.37 0.0020 68.29 4 0.525 0.526 0.525 0.525 16.04 0.0006 79.94 6 0.436 0.439 0.432 0.436 13.06 0.0035 83.68 7 0.436 0.438 0.434 0.435 13.06 0.0021 83.68 8 0.436 0.433 0.436 0.438 13.06 0.0025 83.68

MKA pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 0.412 0.412 0.413 0.411 12.26 0.0010 84.67 4 0.182 0.182 0.181 0.183 4.60 0.0010 94.25 6 0.05 0.05 0.051 0.05 0.21 0.0006 99.74 7 0.05 0.052 0.05 0.059 0.21 0.0047 99.74 8 0.05 0.05 0.051 0.05 0.21 0.0006 99.74

MBM pH Average A1 A2 A3 Ce Sd % absorbance Removal 2 1.185 1.185 1.186 1.185 38.04 0.0006 52.44 4 0.993 0.993 0.992 0.994 31.63 0.0010 60.46 6 0.866 0.867 0.865 0.865 27.39 0.0012 65.76 7 0.866 0.866 0.868 0.863 27.39 0.0025 65.76 8 0.866 0.869 0.865 0.863 27.39 0.0031 65.76

Appendix 21: Comparison of percentage removal versus contact time

Effect of contact time on percentage removal of Pb2+ ions Contact time MKAC MKC MKA MBM 20 86.5 76.50 88.25 41.00 40 90.25 82.50 92.25 50.75 60 93.25 87.50 96..75 56.75 80 93.00 87.50 96.75 61.75 100 93.00 87.50 96.74 61.75

Effect of contact time on percentage removal of Cd2+ ions Contact time MKAC MKC MKA MBM 20 84.26 81.65 92.65 62.35 40 93.53 81.73 96.43 65.45 60 95.15 82.98 98.93 67.21 80 95.15 83.16 98.93 71.65 100 95.15 83.16 98.93 71.67

Appendix 22: Comparison of percentage removal versus initial metal concentration a) Effect of concentration on percentage removal of Pb2+ ions Concentration MKAC MKC MKA MBM of metal ions (mg/L) 20 95.00 91.00 98.00 81.00 40 92.17 86.67 97.00 74.50 60 90.78 83.78 95.67 66.33 80 89.67 82.75 93.25 57.75 100 89.00 81.67 93.80 50.60 120 89.20 80.72 93.80 48.20 140 89.20 80.72 93.80 48.20 160 89.20 80.72 93.80 48.20

Effect of concentration on percentage removal of Cd2+ ions Concentration MKAC MKC MKA MBM of metal ions (ppm) 20 97.56 92.67 99.72 81.22 40 94.33 87.22 97.33 76.83 60 90.29 81.72 93.31 71.13 80 88.34 78.43 91.33 66.22 100 86.76 76.22 91.34 63.44 120 86.76 74.33 91.34 60.25 140 86.76 74.33 91.34 60.25 160 86.76 74.33 91.34 60.25

Appendix 23: Comparison of percentage removal versus dosage a)

Effect of dosage on percentage removal Pb2+ ions Mass (g) MKAC MKC MKA MBM 0.1 89.25 80.25 90.25 56.25 0.2 95.50 83.50 97.00 66.50 0.3 95.25 85.23 97.00 70.50 0.4 95.25 85.23 97.00 73.25 0.5 95.00 85.23 96.25 73.25

Effect of dosage on percentage removal of Cd2+ ions Mass (g) MKAC MKC MKA MBM 0.1 88.45 76.67 95.30 56.54 0.2 92.14 80.46 97.41 62.43 0.3 93.63 86.22 97.40 68.70 0.4 93.63 86.22 97.40 72.21 0.5 93.00 81.67 96.70 72.21

Appendix 24: Comparison of percentage removal versus temperature a)

Effect of temperature on percentage removal of Pb2+ ions Temperature MKAC MKC MKA MBM (oC) 25 89.50 83.34 98.25 59.75 35 93.25 86.25 98.50 61.50 45 95.25 90.25 98.75 63.50 55 92.50 87.75 98.50 66.75 65 90.22 84.25 97.50 67.25

Effect of temperature on percentage removal of Cd2+ ions Temperature MKAC MKC MKA MBM (oC) 25 86.32 78.33 94.36 55.29 35 90.76 82.78 97.57 61.33 45 94.89 81.03 97.51 67.47 55 92.79 80.03 95.38 71.65 65 89.19 79.68 92.93 71.65

Appendix 25: Comparison of percentage removal versus pH a)Effect of pH on percentage removal of Pb2+ ions pH MKAC MKC MKA MBM 2 83.00 72.00 93.50 58.25 4 92.25 81.25 98.50 62.25 6 96.25 89.00 98.75 65.25 7 96.00 89.00 98.50 65.00 8 96.00 89.00 98.50 65.00

Effects of pH on percentage removal of Cd2+ ions pH MKAC MKC MKA MBM 2 77.50 68.29 84.67 52.44 4 85.89 79.92 94.25 60.46 6 92.39 83.68 99.74 65.76 7 92.39 83.68 99.74 65.76 8 92.39 83.68 99.74 65.76

Appendix 26: Parameters for drawing Langmuir and Freundlich adsorption isotherm for Pb2+ ions

Parameters for plotting Langmuir and Freundlich isotherms for Pb2+ ions on MKAC Co (mg/L) Ce 1/ce Log Ce Qe (mg/g) 1/Qe Log Ce (mg/L) 20 1.00 1.00 0.00 9.50 0.1053 0.9777 40 3.13 0.3195 0.4955 18.44 0.0542 1.2658 60 5.53 0.1808 0.7427 27.24 0.0367 1.2658 80 8.27 0.1209 0.9175 35.87 0.0279 1.4352 100 11.00 0.0909 1.0414 44.50 0.0225 1.5547 120 12.03 0.0773 1.1116 53.54 0.0187 1.6484 140 15.13 0.0661 1.1798 62.44 0.0160 1.7287 160 17.27 0.0579 1.2373 71.37 0.0140 1.8535

Parameters for plotting Langmuir and Freundlich isotherms for Pb2+ ions on MKC Co (mg/L) Ce 1/Ce Log Ce Qe (mg/g) 1/Qe Log Qe (mg/L) 20 1.80 0.5556 0.2553 9.10 0.1099 0.9590 40 5.33 0.1876 0.7267 17.34 0.0577 1.2390 60 9.73 0.1028 0.9881 25.14 0.0398 1.4004 80 13.8 0.0725 1.1399 33.10 0.0302 1.5198 100 18.33 0.0546 1.2632 40.84 0.0245 1.6111 120 23.13 0.0432 1.3642 48.44 0.0206 1.6852 140 27.00 0.0370 1.4314 56.50 0.0177 1.7520 160 30.8 0.0325 1.4886 64.60 0.0155 1.8102

Parameters for plotting Langmuir and Freundlich isotherms for Pb2+ ions on MKA Co (mg/L) Ce (mg/L) 1/Ce Log Ce Qe (mg/g) 1/Qe Log Qe 20 0.40 2.5000 -0.3979 9.80 0.1020 0.9912 40 1.20 0.8333 0.0792 19.40 0.0515 1.2878 60 2.60 0.3846 0.4149 28.70 0.0348 1.4579 80 5.40 0.1852 0.7324 37.30 0.0268 1.5717 100 6.25 0.1600 0.7959 46.88 0.0213 1.6709 120 7.44 0.1344 0.8716 56.28 0.0178 1.7504 140 8.68 0.1152 0.9385 65.66 0.0152 1.8173 160 9.92 0.1008 0.9965 75.04 0.0133 1.8753

Parameters for plotting Langmuir and Freundlich isotherms for Pb2+ ions on MBM Co Ce (mg/L) 1/Ce Log Ce Qe (mg/g) 1/Qe Log Qe (mg/L) 20 3.80 0.2632 0.5798 8.10 0.1235 0.9085 40 10.20 0.0980 1.0086 14.90 0.0671 1.1732 60 20.20 0.0495 1.3054 19.90 0.0503 1.2988 80 33.80 0.0296 1.5289 23.10 0.0433 1.3636 100 49.40 0.0202 1.6937 25.30 0.0395 1.4031 120 62.13 0.0161 1.7933 28.94 0.0346 1.4615 140 72.53 0.0138 1.8605 33.74 0.0296 1.5281 160 82.93 0.0121 1.9187 38.54 0.0259 1.5859

Appendix 27: Parameters for drawing Langmuir and Freundlich adsorption isotherm for Cd2+ ions a)

Parameters for plotting Langmuir and Freundlich isotherms for Cd2+ ions on MKAC Co (mg/L) Ce 1/Ce Log Ce Qe (mg/g) 1/Qe Log Qe (mg/L) 20 0.49 2.0408 -0.3098 9.76 0.1025 0.9895 40 2.27 0.4405 0.3560 18.87 0.0529 1.2758 60 5.82 0.1718 0.7649 27.09 0.0369 1.4328 80 9.33 0.1072 0.9699 35.34 0.0283 1.5483 100 13.24 0.0755 1.1219 43.38 0.0231 1.6373 120 15.89 0.0629 1.2011 52.06 0.0192 1.7165 140 18.53 0.0539 1.2679 60.74 0.0165 1.7835 160 21.18 0.0472 1.3259 69.41 0.0144 1.8414

80 b)

Parameters for plotting Langmuir and Freundlich isotherms for Cd2+ ions on MKC Co (mg/L) Ce 1/ce Log Ce Qe (mg/g) 1/Qe Log Qe (mg/L) 20 1.47 0.6803 0.1673 9.27 0.1079 0.9671 40 5.11 0.1957 0.7084 17.45 0.0573 1.2418 60 11.57 0.0864 1.0633 24.22 0.0413 1.3842 80 17.26 0.0579 1.2370 31.37 0.0319 1.4965 100 23.78 0.0421 1.3762 38.11 0.0262 1.5810 120 30.8 0.0325 1.4886 44.6 0.0224 1.6493 140 35.94 0.0278 1.5556 52.03 0.0192 1.7163 160 41.07 0.0244 1.6135 59.47 0.0168 1.7743

Parameters for plotting Langmuir and Freundlich isotherms for Cd2+ ions on MKA Co (mg/L) Ce 1/Ce Log Ce Qe (mg/) 1/Qe Log Qe (mg/L) 20 1.00 1 0.00 9.50 0.1053 0.9777 40 1.07 0.9346 0.0294 19.47 0.0514 1.2894 60 4.01 0.2494 0.6031 27.99 0.0357 1.4470 80 6.93 0.1443 0.8407 36.54 0.0274 1.5628 100 8.66 0.1155 0.9375 45.67 0.0219 1.6596 120 10.39 0.0963 1.0166 54.81 0.0182 1.7389 140 12.12 0.0825 1.0835 63.94 0.0156 1.8058 160 13.86 0.0722 1.1418 73.07 0.0137 1.8637

Parameters for plotting Langmuir and Freundlich isotherms for Cd2+ ions on MBM Co (mg/L) Ce 1/Ce Log Ce Qe (mg/g) 1/Qe Log Qe (mg/L) 20 3.76 0.2659 0.5752 8.12 0.1232 0.9096 40 9.27 0.1079 0.9671 15.37 0.0651 1.1867 60 17.32 0.0577 1.2386 21.34 0.0469 1.3292 80 27.02 0.0370 1.4317 26.49 0.0378 1.4231 100 36.56 0.0274 1.5630 31.72 0.0315 1.5013 120 47.7 0.0209 1.6785 36.15 0.0277 1.5581 140 55.66 0.0179 1.7455 42.17 0.0264 1.6250 160 63.60 0.0157 1.8035 48.20 0.0252 1.6831

Appendix 28: Raw data for turbidity

MKAC

Mass average 1 2 3 Sd Removal % (g) Removal 0.1 130.26 130.27 130.26 130.25 0.0100 76.49 36.99 0.2 126.23 126.32 126.31 126.34 0.0153 80.43 38.90 0.3 112.49 112.49 112.48 112.51 0.0153 94.25 45.59 0.4 97.42 97.42 97.41 97.42 0.0058 107.33 52.89 0.5 93.41 93.41 93.41 93.42 0.0058 113.37 54.82

MKC

Mass average 1 2 3 Sd Removal % (g) Removal 0.1 162.38 162.39 162.38 162.38 0.0058 44.37 21.46 0.2 158.31 158.31 158.3 158.31 0.0058 48.44 23.43 0.3 146.45 146.45 146.44 146.45 0.0058 60.3 29.17 0.4 144.26 143.26 143.27 146.25 1.7234 62.49 30.22 0.5 141.35 141.34 141.33 141.37 0.0208 65.4 31.63

MKA

Mass average 1 2 3 Sd Removal % (g) Removal 0.1 7.73 7.73 7.72 7.72 0.0058 199.02 96.26 0.2 6.26 6.27 6.26 6.25 0.0100 200.49 96.97 0.3 5.43 5.44 5.42 5.44 0.0115 201.32 97.37 0.4 5.47 5.47 5.46 5.47 0.0058 201.28 97.36 0.5 5.44 5.43 5.49 5.48 0.0321 201.31 97.36

MBM

Mass average 1 2 3 Sd Removal % (g) Removal 0.1 126.24 126.22 126.24 126.25 0.0153 80.81 38.94 0.2 113.32 113.33 113.31 113.33 0.0115 93.42 45.19 0.3 96.22 96.22 96.23 96.21 0.0100 110.53 53.46 0.4 83.62 83.62 86.61 86.63 1.7321 123.13 59.56 0.5 82.76 82.75 82.77 82.76 0.0100 123.99 59.97

Appendix 29: Comparison for percentage turbidity removal

Percentage removal of turbidity Dosage (g) MKAC MKC MKA MBM 0.1 36.99 21.46 96.26 38.94 0.2 38.9 23.43 96.97 45.19 0.3 45.59 29.17 97.37 53.46 0.4 52.88 30.22 97.35 59.56 0.5 54.82 31.63 97.37 59.97