www.iaard.net eISSN: 2455 – 4472 International Association of Advances in Research and Development International Journal of Environmental Science and Technology International Journal of Environmental Science and Technology, 2015, 1(2),20-26 Synthesis and Characterization of Eucalyptus by for Sheet Formation Atnafu Guadie 1*, Agraw Mulat 1, Addis Kokeb 1, Nigus Gabbiye 2 1Department of Chemistry, University of Gondar, P.O. 196, Gondar, Ethiopia 2School of Chemical and Food Engineering, P. O. Box 26, Bahir Dar University, Bahir Dar, Ethiopia *Corresponding Author’s email: [email protected] …………….………………………...... Abstract: In contrast to the highly growing demand of paper and paper products, paper product in Ethiopia is at its infant stage where there are only paper mills producing an annual output of 10-15 tones in aggregate. This number is very low as compared to other African countries by importing the raw material pulp outside the country and in some extent from recycled paper. This study deals with the synthesis and characterization of eucalyptus pulp by the Kraft process. The separation of the pulp from eucalyptus chips were performed in three stages: Prehydrolysis, cooking (digestion) and bleaching steps. The results indicate that Kraft process is considered to be more suitable to extract pulp from eucalyptus chips since higher yield of cellulose (46.4 %) and low content pulp was obtained that demonstrated a better pulp quality with lower value of (5.9). The Fourier transform (FT-IR) spectrum of single and sequential bleached pulps specified that the chemical treatment successfully remove the lignin and content. The UV-visible spectrums of single and sequentially bleached eucalyptus pulp shows transparent at visible region that confirms the characteristic indicator of satisfactory brightness of the bleached pulps. In this study, the Kraft process was found to be a suitable process for pulp synthesis and making high quality writing and with low cost due to the cheapest raw material and recovery of the chemicals used. Keywords : Eucalyptus Pulp, Kraft process, Paper, Kappa number, Lignin Content ……………………………………………………………………………………………………………………… 1. Introduction the proportion of is higher. The molecular mass of Paper making industry is a huge industrial branch with lignin is also apparently lower than the high capacities, complicated equipment and processes softwood lignin. Thus, hard wood is a better raw influenced by variety of factors. Paper has become is a material for producing the expected pulp yield with the crucial substance in our day to day activities. The range required quality. Cellulose is the main component of of possible uses of paper is infinite and alternative wood carbohydrates polysaccharide consisting of means of using it are being devised daily. The most glucose units. The cellulose molecule easily forms commonly used paper types are stationary paper (i.e. hydrogen bonds with neighboring molecules, thus printing and writing), news print, covering, packaging, giving xylem cells mechanical support that makes it and paper card. Pulp and paper are manufactured from suitable for paper making [4-5] . In terms of quantity, wood, recycled paper and many types of farming cellulose is the most abundant renewable polymer residue. Now a day, the main raw material for paper resource available worldwide. It has been estimated making is wood fibers which are called wood pulp. that, by photosynthesis 10 11 to 10 12 tons are synthesized Both soft and hard wood species can be used for annually in a rather pure form but mostly in producing fibrous material [1] . Most lingo-cellulosic and combination with lignin and other polysaccharides cellulosic materials of fibrous structure of wood may be (hemicelluloses) in the cell wall of woody plants [6] . processed into various grades of papers and paper Pulp is the raw material for the production of paper, board. Fibres from different raw materials are differing , fiberboard, and similar manufactured considerably in their morphological and chemical products. Pulp is obtained from plant fiber (cellulose) characteristics, which make them more or less and is, therefore, a renewable source. Pulp is the most appropriate for paper making [2, 3] . Hardwood fiber is important product of chemical conversion of considerably shorter and thinner than the softwood lignocelluloses materials [7] . It can be obtained by fibers. Generally, hardwood contains more cellulose digesting wood chips in acidic, neutral or alkaline and hemicelluloses and less lignin than softwood while conditions. There are many types of pulping processes

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viz., chemical, mechanical, semi-chemical and recycle screened with 0.8 mm mesh and 1.5 mm mesh sieves to among which chemical pulping is the most common eliminate over sized and fine chips. Then, the chips process [8] . Chemical (i.e., Kraft, soda, and sulfite) were washed several times with distilled water to pulping involves cooking of wood chips using aqueous remove dirties and dried with electric oven and stored chemical solutions at elevated temperature and pressure in moisture free place until analysis. to extract pulp fibers [9] . Generally, paper is made by 100 grams of accepted chips with 0.8 mm mesh sieve pulping wood, bleaching this pulp and then spreading it size were fed in to the autoclave at a pressure of 6 bar. out into sheets to formulate paper. At various stages of The extraction (prehydrolyzed) experiments were the process, chemicals are used to give the paper performed with (21.948 grams of NaOH particular properties such as the bleaching chemicals and 14.88 grams of Na 2S) to wood ratio of 4:1 at 100 that make paper white (and which also enable it to oC for 100 minutes. The wood chip was then washed subsequently be colored). Kraft pulping is by far the with distilled water. Then, the washed pre-hydrolyzed most common pulping process in the world for virgin chip heated in an oven drier at 105 oC for 180 minutes fiber, accounting for more than 80 percent of the total to remove the moisture gained during prehydrolyzed world pulp production [10] . process. The weight loss during digestion and washing The major reason why there are no additional paper process was determined by subtracting the dried weight mills with better capacity in Ethiopia is estimated to be from the weight of chips feed to autoclave with the huge capital investment that paper mills normally moisture. require and significantly high cost of raw material that The yield was calculated by the formula: is imported from different countries of the world. These make the local production of paper inefficient and less (1) competitive when compared to other sectors in the 2.2. Digestion of extracted pulp industry, which significantly affects the overall 100 gram of dried pre-extracted wood chips was economic growth of the country. For this reason, the cooked with an autoclave at 131 oC for 140 minutes country should produce the raw material for paper with 4:1 liquor to wood ratio. The cooked pulp was making from the available wood products. Eucalyptus washed with deionized water to remove black liquor wood produces quickly to meet society’s needs, and composed of digested lignin, Na 2SO 4 and Na 2CO 3. also helps preserve indigenous forests. Eucalyptus trees Then the pulp was dried in an open air and weighed to are highly profitable and take a shorter period to reach know the losses during cooking and washing processes. at the harvesting age and require little human action on Finally the yield was calculated using equation (1). [11] the land during this period . 2.3. Bleaching Experiment and Pulp sheet formation It is clear that in Ethiopia, pulp is imported from abroad processes for paper factories. In order to overcome this problem it Bleaching of Kraft pulp were performed in two seems promising to establish pulp factory at a national bleaching methods; single (temporary) bleached by wide. If so, eucalyptus can met the problem of highly hydrogen peroxide and sequential (true or permanent) increasing cost of paper as alternative source of raw bleached by a sequence HEHP which are a combination [3] material for paper synthesis . In order to overcome the of three types of chemicals H(sodium hypochlorite, challenges of the paper industry, a special attention used in two different stages to accomplish two quality should be given facilitating the productions of the parameters: high brightness and high delignification major raw material (pulp) locally and discouraging (residual lignin removal), E(sodium hydroxide) and importation so that the local manufacturers will be P(hydrogen peroxide). competent enough on the market. The main objective of In the first place, the dried pulp was bleached by using this work is to synthesize and characterize eucalyptus hydrogen per oxide as bleaching agent in the ratio of 1: pulp by chemical Kraft process with investigation of 100, hydrogen peroxide (mL) to pulp (g). The solution the recovery mechanism of the consumed chemicals. was prepared from ingredients 2% sodium hydroxide, 2. Materials and Methods 1% sodium sulfide and distilled water. Then, 0.08 mL 2.1. Raw material preparation and Pulp extraction hydrogen peroxide and 8 grams of dry pulp was added Seven up to nine year eucalyptus wood was collected to the solution and bleached for 60 minutes at 80 oC. from Debark at around North Gondar, Ethiopia. The Then, the bleached pulp was washed with distilled eucalyptus wood was debarked, chipped and grinded in water, filtered and dried in an open air until the to the range of 0.2-2 mm. The ground chips were moisture content removed. Finally, the dried bleached

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pulp was weighed to determine the amount of final permanganate consumption was estimated by product and determine losses during bleaching and iodometrictitration method. washing processes. The Kappa number (Kn) or pulp stiffness was In sequential (true) bleaching method all tested pulps calculated according to Equation: were bleached under equal conditions with a simple --(2) four-stage process, without pre-bleaching. The conditions applied (including time, temperature and Where d-converting coefficient into 50% potassium chemical charge) were kept almost the same for each permanganate consumption determined based on the stage in different sequences. The dried cooked pulp was value of v; m- the amount of dry pulp in gram; [1 bleached by a sequence HEHP. +0.013(25T)]-Temperature correction term; T- average In the first stage (sodium hypochlorite, H) the pulp with temperature of the reaction mixture measured 5 minutes 10% consistency was treated with NaOCl solution after the reaction start, °С; V-the volume of 0.1 M (charge of 2.5% based on pulp weight) at a pH of 10 for solution of potassium permanganate required for 60 minutes at 60 °C. The product was then filtered and titration, mL. washed with distilled water until free of chlorine ions. The weight percent of the lignin can be calculated by In the second stage (sodium hydroxide, E) the product the formula: of the first stage were suspended in an aqueous (3) solution with 10% consistency which contained NaOH 2.5. Physical test parameters of pulp (5% based on pulp weight) the suspension was agitated A number of standard tests were carried out on the pre for 90 minutes at 60 °C , filtered and washed with pared sheets. The basic dimensional and structural tests distilled water until reaching neutral condition. such as thickness, porosity, bulkiness and basic strength In the third stage (sodium hypochlorite, H) the product tests of the pulp or paper such as tensile, bursting index of the second stage with 10% consistency was mixed tear and compression tests were carried out. with a NaOCl solution (5% based on pulp weight) pH 2.6. Chemical Recovery Mechanism of 10, which contained the remaining 5% of the active The weak black liquor that was separated from the pulp chlorine requirement for 70 minutes at 70 °C and the after a cooking process was evaporated by using product was filtered and washed with distilled water till Kjeldhal instrument at a temperature of 200 oC. The free of chlorine ions. In the last stage (hydrogen concentrated black liquor after evaporation was burnt in o peroxide, P) the product of the third stage with 10% an oven by 180 C for 24 hrs, the smelt of Na 2CO 3 and consistency was filtered and treated for 60 minutes at Na 2S were formed. The smelt was dissolved with o 60 C with H 2O2 (2.2 % based on pulp weight) , at a deionized water which formed . The pH range of 9-11. Then, it was filtered, washed with solution of green liquor was recausticized by calcium distilled water until reaching neutral condition and oxide-water slurry (Ca(OH) 2). After the caustization the dried in air. liquid phase containing NaOH and Na 2S (white liquor) For pasting, 400 grams of oven-dry pulp which was a was separated from the solid lime mud by a slow mixture of prehydrolyzed, cooked, single and double decantation. The presences of the inorganic salts in the bleached pulps were mixed and beaten at a range of separated liquor were checked by reused the liquor for 3000-4000 rpm and squeezed and pounded digestion of the accepted chips. At last the lime mud mechanically the cellulose. After that the pulp was was heated to decompose by furnace at 1200 0C. ready for the sheet formation. 2.7. Lignin recovery 2.4. Determination of kappa number Kraft black liquors acquired from the end of each cook The Kappa number was determined by the amount of a and at other times during the cooks were isolated by 0.1 M potassium permanganate solution consumed for precipitating the lignin from solution by acidification. the oxidation of lignin contained in 1gram of absolutely The black liquors were first filtered through a whatman dry pulp at the standard conditions. Prepared amount of # 4 on a Buchner funnel. Approximately 0.5 dried unbleached pulp was dispersed in 370 mL of grams of EDTA-2Na + was added for every 100 ml of water avoiding fiber cutting until pulp agglomerates black liquor. The liquors were neutralized with 2 M disappear. A mixture of 50 mL of a 0.1 M potassium H2SO 4 until pH 6. The solutions were then stirred permanganate and 50 mL of a 4 M sulphuric acid vigorously for one hour. The liquors were further solution were added to the pulp suspension under acidified to a pH of 3 and frozen at -20 °C. After continuous stirring and diluted with water to the total thawing the solutions, the precipitates were collected on volume of 500 mL. After 10 minutes, potassium

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a medium sintered glass funnel and washed twice with decreased due to the bleaching chemicals. During cold water by suspending the precipitates in the water bleaching adjustment of pH is necessary at strong and stirring vigorously at 0 °C. The precipitates were alkaline range due to the decrease in alkalinity up on collected, air dried. Finally the recovered lignin was addition of bleaching chemicals otherwise cellulose tested and characterized by FTIR instrument. degradation takes place at lower pH value which 3. Results and Discussion decreases pulp yield. Generally these results give 3.1. Effect of pH higher alkaline process (Kraft) process is suitable for The effect of pH on the synthesis of pulp was high pulp yield product and adjustment of pH is investigated for a wide range of the measured pH at necessarily up on cooking and bleaching processes to different process stages of pulp synthesis (Figure 1). adjust the decrease in pH due to the lignin acidic For a reacting mixtures a short hand designation groups are dissolved [13] . symbols were used; mixture of white liquor chips 3.2. Pulp extraction before hydrolyzed (MBPH), mixture of mother liquor In basic Prehydrolysis 100 g of eucalyptus chips were with chips after prehydrolyzed (MAPH), mixture of suspended in a solution of sodium hydroxide (21.948 g) white liquor with prehydrolyzed chips before cooking and sodium sulfide (14.88 g) white liquor and heated (MBC), mixture of mother liquor with pulp after for 100 minutes in autoclave which gives 70.9 g of cooked (MAC), mixture of bleaching chemicals with prehydrolyzed pulp. cooked pulp before bleaching (MBCPBB). Table 1 The result of the recovered mass and qualitative observation obtained after pre hydrolysis pH Effect 1 5 process 1 4 Parameter Quantitative Qualitative 1 3 Initial weight 100 g - 1 2 Final Weight 70.9 g -

pH 1 1 1 0 Color - Light brown 9 Fine amount Medium - 8 M B pH M A p H M B C M A C M B C P B B Kappa number 20.8 -

Pulp Samples with liquor Lignin content High -

Figure 1 Effect of pH on pulping processes at different After Prehydrolysis only 70.9 g of pulp was obtained stages per 100 g of input chips. In other studies, the yield of pulp for acid and alkaline pre-hydrolyzed pulp is 65% The pH of the reacting mixtures of pulp samples are and 74% respectively [14] . In this study, after decreasing from MBPH-MAPH, MBC-MAC, and Prehydrolysis with base 70.9% yield of pulp was MAC-MBCPBB and sharply increasing from MAPH- achieved. On the other hand, 29.1% of cellulose during MBC (Figure 1). The results showed that during the pre-base Prehydrolysis stage was obtained. In the Kraft process as a result of large amount of NaOH used, Prehydrolysis of the eucalyptus chips, alkaline the pH at the start of the prehydrolyzed and cooking hydroslysis provided a higher yield than acid hydrolysis processes recorded were high due to the alkaline with higher kappa number (more lignin content pulp) pulping process. It decreases continuously during the and light brown in color. At prehydrolyzed step only course of cooking since organic acids were liberated some amount of lignin is removed so that the produced from lignin and carbohydrates (hemicelluloses) during pulp has high kappa number which is 20.8. Besides, the pulping reaction as a result of hydrolysis and medium fine amount of fibers were obtained in this step dissolution processes. This indicates the alkaline Kraft due to incomplete digestion process. process hydrolyzes and dissolves the lignin and the The low yield in the acid pulping could be amorphous hemicelluloses at higher pH, and prevents related to acid hydrolysis of cellulose to sugar the hydrolysis of cellulose which is favorable in acidic monomer. Acid hydrolysis proceeds in three steps. The conditions at a lower pH value. At acidic condition reaction starts with a protonation of the glycosidic cellulose fibers were degraded up on decreasing of its oxygen linking in to two sugar units, forming pH when lignin is dissolved [12] . protonated cellulose (conjugate acid). Then, water The sharp decrease from MAC-MBCPBB makes a nucleophilic attack on the protonated cellulose indicates large amount of lignin dissolution at the time which breakdown to the cyclic carbonium ion [14] . This of cooking at higher pH and the residual lignin content

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indicates Kraft alkaline process is suitable for high pulp input which corresponds to 8.9 % loss and 91.1% yield of pulp synthesis. yield (Table 3). 3.3. Cooking or Digestion of Eucalyptus Wood Table 3 Yield and quality of pulp obtained by single In this study, after digestion only 46.4 g of bleaching process pulp was obtained per 100 grams of input prehydrolyzed chips (Table 2) at cooking conditions of Parameter Quantitative Qualitative 6 bars, 131 oC for 140 minutes, liquor to wood ratio of Initial weight 20 gm - Final weight 18.22 gm - 4:1 and effective alkali of 87.8g per liter with a Color - white sulphidity of 24.4 %. Kappa number 7.7 - Table 2 . The result obtained after cooking process Fine content Very small - Parameter Quantitative Qualitative Initial weight 100 gm - Lignin content Low - Final weight 46.4 gm - The single bleached eucalyptus pulp has a kappa number of 7.7 which is less than the kappa Color - Dispersed white Kappa number 9.834 number 9.834 of cooked pulp (Table 2) signifies the Fine amount small - residual lignin content almost removed up on bleaching with hydrogen peroxide. The fine content of the fibers After cooked with white liquor, a yield of also increased very well due to removal of a residual 46.4 % pulp was achieved which is nearer value of lignin that can compact the fibers by holding together. yield to the expected one which is 53-56 % [4] for The 91.1 % yield from the single bleached pulp reveals eucalyptus Kraft pulp. The eucalyptus cooked pulp has that hydrogen peroxide has a high selectivity power to a kappa number of 9.834 (Table 2) which is less than degrade the residual lignin without interfering to the from the kappa number of prehydrolyzed pulp which degradation of carbohydrates specially cellulose fiber has a (kappa number of 20.8) (Table 1). This suggested which is the main constituent of pulp yield and gives that much of the lignin was dissolved and entered into achievable brightness of the pulp product. the liquid phase during cooking step. 7-10 % cellulose It was reported that lignin removal rates is as loss of fiber pulp is less than that of the expected value high as 95 % during bleaching pulp which leads high due to unfavorable conditions for digestion like the levels of brightness (whiteness) without pulp non-selectivity of the chemicals (white liquor) used to degradation [15] . In that , the result obtained in this degrade lignin, time, temperature and the decrease in experiment has comparable pulp yield of 91.1%. Thus, pH. In the cooking stage of this process in a pressurized hydrogen peroxide can remove the residual lignin autoclave with a specific pressure of 6 bar, the cooking attached to the cellulose after cooking and cleavage aryl chemicals (white liquor) used in pulping process alter ether linkage of the attached cellulose that increases the the structure of lignin in such a way that soluble dissolution of lignin. But, it only gives temporarily fragments of polymer was produced by different brightness which is not suitable for manufacturing of possible mechanisms. many types of paper grades. 3.4. Pulp Bleaching Sequence In the sequentially bleached pulp, after each Pulping process alone is not enough to produce bleaching stage, the pulps were thoroughly washed with cellulose of eucalyptus suitable for Pulp synthesis deionized water and analyzed for yield and residual applications. After pulping, cellulose must be subjected lignin contents (Kappa number).The progress of the to further purification. The goal of bleaching is to digestion was monitored by measuring the pH. The reduce the kappa number without drastically decreasing resulted sequentially bleached pulp has 5.9 of kappa the degree of polymerization of the cellulose. In single number which indicates almost the total removal of bleaching step, 20 grams of cooked dried pulp was lignin from pulp which gives brightest permanent bleached with bleaching agent of 0.2 mL of hydrogen whiteness colored pulp. The weight of pulp at the first per oxide for 60 minute at 80 oC operating temperature. bleaching stage was 20 g at one step whereas the At the end of operation, the bleached pulp was washed, weight of the bleached pulp after the sequential dried and weighed. bleaching was 15.4 g. This shows that a weight loss of

After bleached by H 2O2 18.22 g of white 6.6 g pulp and a decrease in pulp yield to 77 % which is bleached pulp was obtained from 20 g of dried cooked less than single bleached pulp yield of 91.1 %. It may be due to the unselectively degradation of cellulose by

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bleaching chemicals and loosing of the pulp during higher lignin content. Consequently, low Kappa open air dried. numbers should be targeted if the pulp is to be bleached 3.5. Determination of kappa number [14] . The amount of lignin remains in cellulose after In this experiment, the mass, blend temperature pulping and bleaching usually estimated by Kappa and volumes were measured for cooked pulp, single number. The Kappa number is an indicator of the bleached pulp and sequential bleached pulp during each residual lignin content of the pulp and is an important of the experiment separately. quality parameter. The higher Kappa number gives Table 4 . the measured parameters and the calculated kappa number of bleached & unbleached pulps Parameters Sample name m (g) ºC b (ml) V2(ml) C(M) V(ml) d Kappa number Cooked pulp 3 20 12 6.8 0.2 27.4 1.011 9.834 Single bleached 3 23 12 10.8 0.2 22.8 0.991 7.7 Sequential bleached 3 23.8 12 13.1 0.2 18 0.970 5.9

The kappa number decrease as bleaching stage plane bending of cellulose of bleached pulp. The increase. The result indicated that residual lignin medium sharp tiny peak at around 1374 cm -1 indicates content of cooked pulp is highest whereas due to bending vibration of aliphatic C-H stretching in methyl effective bleaching, it decreases when the pulp was and C-O groups of the aromatic ring in polysaccharides bleached. Lignin content would not be completely (cellulose). The absorbance short branched peak at removed during the digestion step which has a higher around 1311 cm -1 assigned to C-H in plane bending of amount of residual lignin content whereas up on cellulose I and cellulose II and used to characterize bleached with single chemical it decreases a lesser polymorphs of crystalline cellulose. extent and bleaching with a combination of chemicals The medium branched peak at around 1157 cm - as HEHP sequence resulted almost pure pulp. 1 is due to C-O-C ring vibrational stretching of B(1,4)- Generally, the result indicates that sequential bleaching glycosidic linkage for cellulose I and cellulose II and C- sequence was an achievable and efficient method for O anti-symmetric bridge stretching of cellulose. The complete removal of the residual lignin which gives a broad long peak at around 1060 cm -1 indicates the C- lower kappa number of 5.9. OH stretching vibration of the cellulose and 3.6. Characterizations of the synthesized pulp hemicelluloses.The very short tiny absorption band at 3.6.1 FTIR data of single and sequential bleached around 893 cm -1 assigned to C-O-C β-glycosidic pulps linkages between the glucose units of cellulose. The FTIR spectra of single and sequential bleached peaks at around 677 cm -1 and 607 cm -1 can be attributed pulps were recorded for further investigation of the to C-OH out of plane bending of cellulose. The result of structures of constituents and the chemical changes of the FTIR spectrum in this study is the same as reported eucalyptus pulps during Kraft pulping and bleaching. in previous studies [16-22] . Thus, the IR spectra of the two types of bleached pulps Similarly, the spectra of sequential bleached have almost the same number of peak absorption bands pulps shows a bands at 1423, 1374,1157,1060,893 and (Figure 2). However, the amount of absorption bands 677 cm -1 are assigned to O-H in-plane bending of sharpness of the peaks, their intensities, their cellulose and C-H asymmetric deformation, bending broadening and overlapping are different. An intense, vibration of aliphatic C-H stretching in methyl and C- very broad absorbance peak at around 3444.9 cm -1 O groups of the aromatic ring, C-O-C ring vibrational indicates the OH - bond stretching vibration of alpha stretching of B(1,4)-glycosidic linkage for cellulose I cellulose. The signals at around 2894 cm -1 is due to C- and cellulose II and C-O anti symmetric bridge H stretching vibrations in methyl and methylene groups stretching of cellulose. of the polysaccharide (lingo cellulosic components). The C-OH stretching vibration of the cellulose The peaks observed at around 1639 cm -1 is due to the and hemicelluloses-O-C B-glycosidic linkages between OH - vibration of the adsorbed water. The short the glucose units of cellulose and C-OH out of plane branched peak at around 1423 cm -1 is attributed to bending of cellulose, which are associated with typical skeletal vibration of the aromatic ring combined with absorption of cellulose. This indicates the evidence of C-H in plane deforming and stretching and the OH - in removed from the bleached pulp effectively.In

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general band intensity changes in the spectra reflects changes (degradation and condensation) taking place the sequential bleached pulps have an intense and during bleaching and lignin extraction as a result their sharper peaks than single bleached once which peaks are differ in band intensity. indicates the effectiveness of the former system. The

Figure 2 . FTIR Spectra of single and sequential eucalyptus pulp by alkaline H 2O2

3.6.2. FTIR Spectra of the recovered lignin O stretching vibration of H 2SO 4 added at lignin In order to elucidate the structure of Kraft lignin recovery acidification step [18, 23] . 467 cm -1, and 426 cm - isolated from the eucalyptus pulp from black liquor by 1 is due to the Na metallic absorption of sodium metal acid precipitation were analyzed by FTIR (Figure 3). that came from digestion step. -1 The wide absorption band at around 3410 cm is R ecovered Lignin 4 5 - 8 7 2 assigned to aromatic and aliphatic OH vibrations of 4 0 1 3 1 1

-1 3 5 Kraft lignin. The band at around 3020 cm is reflected 1 2 1 4 3 0 to the C-H vibration of methyl and methylene groups of 2 5 4 2 6 Kraft lignin. The band at around 1694.8 cm -1 2 0 4 6 7 1 5 3 0 2 0 7 8 1 .8 5 5 8 Transmittance:% corresponding to conjugated carbonyl stretching (C=O) 1 0 1 4 1 6 5 8 6 5 3 4 1 0 1 6 9 4 .8 9 6 3 [23] 1 0 9 5 1 0 4 6 of ketones and carboxyl groups of lignins .The band 0 4000 3500 3000 2500 2000 1500 1000 500

-1 - 1 at around 1416 cm indicates skeletal vibration of W ave num ber / C m aromatic ring (C-C) vibration of the lignin. The band at Figure 3. IR Spectra of recovered kraft lignin from the around 1311 cm -1 is due to syringyl ring vibration with black liquor valence vibration of CO-group which indicates syringyl In the IR spectrum of recovered kraft lignin, aromatic structure of the lignin. The absorbance peak absorption band of valence vibrations of alcohol and around 1214 cm -1 reflects the C-O vibration of ring phenol O-H bonds is surely identified with maximum guaiacyl structure of lignin and the skeletal vibration of absorption at about 3410 cm -1. Moreover, an intense syringyl ring. The peak appeared at around 1095 cm -1 vibration band of carbonyl group (C=O) is observed at comes from the ArC-H in-plane deformation in 1694.8 cm -1 that can be explained by either carbonyl guaiacyl ring and the plane deformation vibration of groups presence in lignin structure or acetylated alcohol ArC-H bond in syringyl ring structure of the recovered fragments or ester linkage of carboxylic group in the lignin [23] . ferulic and p-coumeric acids of lignin or The band at 1046 cm -1 comes from plane [18] . deformation vibrations of C-H bond in guaiacyl ring The absence of this peak in the above bleached and deformation vibrations of C-OH bond in primary pulp spectra indicates the removal of lignin and alcohols and C-O-C vibrations in ethers of the kraft hemicellulose during the chemical treatments of lignin [16] . The peak appeared at around 963 cm -1 arises beaching process. Absorption band at 1416 cm -1 may be from the C-H out-of plane bending in guaiacyl units of assigned to skeletal vibrations of aromatic ring. Peaks lignin. The peak at around at around 873 cm -1 indicates at 1311 cm -1 corresponds to skeletal vibrations of out of plane bending of C-H in syringyl units of lignin syringyl ring and at 1214 cm -1 that corresponds to and syringyl ring vibration of the recovered lignin [17] . skeletal vibrations of syringyl ring with guaiacyl ring The band at around 781.8 cm -1 arises due to C-OH out vibration super position. The absence of this peaks in of plane bending of the dissolved cellulose and ArC-H bleached pulp spectra (Figure 2) believed to be due to vibrations of the guaiacyl units of lignin [23] . The peaks the removal of lignin after chemical treatments. arise at 586 cm -1 and 558 cm -1 is associated with the S-

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The absorption bands at 1694.8, 1214, 1095, 1046, 963 conjugated C=O and C=C systems such as occur in o- and 872 cm -1 in this spectra attributed to the functional Quinone’s and in aromatic aldehyde, acids and ketones. groups present in the lignin before delignification but The main functional group contributing to the they are absent in the bleached pulps spectra (Figure 2). oxidation of hard wood Kraft residual lignin is syringyl, Thus, the spectra show that the recovered lignin is C5 non condensed guaiacyl units and stilbene phenolic composed of guaiacyl and syringyl structures, which structures. The inability to oxidize the phenyl propane are typical for lignin of hard wood pulp [19] . side chain of lignin and/or C5 condensed guaiacyl 3.6.3. UV-Visible diffuse absorption spectrum of phenolics detrimentally impacts bleachability [24] . The bleached pulps for brightness studies UV-vis difference spectrum had no absorption band at

UV-Vis reflectance spectroscopy is an efficient λmax 370 nm suggesting the absence of phenolic method for brightness stability studies. The absorbance stilbene-like structures which are the main components of UV spectra is directly proportional to the purity level of residual lignin. of lignin. Visible spectral region and reflectance spectra The UV-vis spectrum of the bleached pulps are sensitive to the changes in colored pulp components shows that both spectrum of pulps are visible determining pulp brightness. UV-active structures (like transparent which indicates enough brightness of the HexA, carbonyl groups and some lignin units) are pulps so that the lignin chromospheres were removed known precursors to the colored structures formed by chemical treatments with bleaching agents. during yellowing [24] . Single and sequentially bleached 3.6.4. Physical test parameters of pulp after sheet pulps were recorded by UV-visible diffuse reflectance formation spectrometer (Figure 4). The basic dimensional and structural tests such as thickness, porosity, bulkineness and basic strength tests of the pulp or paper such as tensile, bursting and tear tests were carried out. The maximum pressure that the prepared sheet can resist when applied perpendicularly to the surface of the sample was 1 kg/m 2 which is less than the standard (1.2 kg/m 2). This may happen due to short fibers of the eucalyptus pulp and the effect of beating. Bursting strength increases with increasing Figure 4 . The UV-visible spectra of single and beating energy. sequential bleached eucalyptus pulp The spectra near 370 and 320 nm are bands probably arise from strongly

Table 5. Results of physical testers of pulp after sheet formation

Parameters Test result Standard Bursting strength (kg/cm 2) 1.00 1.2 Porosity (sec/100m) 11.02 10 Tear strength (MN) 63.04 65 Smoothness (mL/sec) 388.42 365-424 Tensile strength (kg) 5.6 6 Thickness (mm) 0.16 0.1 Bulkiness (cm 3/gm) 1.78 1.67 The prepared sheet has a value of porosity sheet of eucalyptus pulp is low kappa pulp than the 11.02 sec/100m which is greater than the standard value standard once due to its high porosity. (10 sec/100m) which indicates the sheet prepared from The tear Strength (MN) measures the ability of the eucalyptus pulp is highly air permeable and porous due sheet to resist the propagation of a tear and the amount to increased amount of beating which gives a denser of energy to fracture a sample [24] . The prepared sheet smooth paper [4, 24] . The air permeability of high kappa had a value of tear strength 63.04 MN which is nearer pulp is lower than low kappa pulp so that the prepared to the standard ones which has value of 65 MN tear strength. The resulted eucalyptus Kraft pulp that was rregularities under either usual or unusual conditions. prepared in this experiment has enough strength. Smoothness is higher for denser, smaller and more Smoothness (mL/sec) refers to the absence of surface

Atnafu Guadie et al., Page No. 34 International Journal of Environmental Science and Technology, 2015, 1(2),20-26 flexible fiber made papers but lower for bulky papers weak black liquor was evaporated by Kjeldhal [1] . The prepared sheet has a value of smoothness instrument. The result of this evaporation was 388.42 mL/sec which is a comparable value to the concentrated black liquor. After concentration of the standard indicates a smooth paper made with no black liquor it was burned by using an oven so that due irregularities. to the reduced sodium sulfur compounds Na 2S 2 Tensile strength (KN/m ) is the maximum force containing smelt with NaCO 3 was formed. The smelt per unit weight that a paper can tolerate without was dissolved with water that was given a green liquor breaking with the load applied in the direction of product. The solution of green liquor was reacted with parallel to the length of the sample. The stress is calcium oxide-water slurry for caustization process. expressed as force per unit width of a test specimen. After caustization two phase solution were Tensile index relates the value of tensile strength to the obtained which indicates the formation of the solid lime basis weight of the material. Tensile index is mainly mud due to calcium carbonate formation and a white used for pulp strength whereas tensile strength is liquor mixture of a liquid phase containing NaOH and [4] preferable for paper strength . The prepared sheet has Na 2S. This white liquor was separated from the solid tensile strength value of 5.6 Kg nearer to the standard lime mud by slow decantation and once again used for sheet which has a value of tensile strength 6 kg. digesting of eucalyptus chips. At last the lime mud was

The thickness of the paper (mm) was measured heated by furnace at 1200 °C so that CO 2 was evolved between two parallel plates applying certain pressure. from the mud that indicates the regeneration of calcium The prepared eucalyptus pulp sheet has thickness value oxide of calcium oxide slurry. of 0.16 mm higher than the standard. This may be due 3.7. Material Balance to the less compact of fibers. The actual physical The material (mass) balance calculation of thickness of a piece of paper usually expressed in this document is based on experimental results obtained thousands of an inch is the bulk of the paper. Bulk during laboratory analysis and can be scaled up into affects the flexibility of the paper. In general, bulk industrial level considering the annual pulp demand of decreased continuously with increased amount of about 10,000 tons of pulp for Ethiopia Paper Factory beating. The sheets made from high lignin containing (Wonji). The main purpose of performing material and pulp had lower bulk whereas the sheet made from lower energy balance is to know raw material and energy lignin containing pulp had higher bulk [24] . The prepared demand as well as the size of equipments for the sheet had a bulk value of 1.78 cm 3/g which is higher proposed production capacity. than the standard so that the sheet was formed from As indicated in the Table 6, it is clear that mass lower lignin containing pulp. of output product (unwashed prehydrolyzed pulp) is 3.6.5. Recovery of Inorganic Chemicals equal to that of the sum of individual input. The chemicals used were recycled for profitability and environmental reasons. Firstly the

Table 6 . Combined experimental result for the purpose of mass balance Process step Pre Digestion Single Bleaching Sequentially hydrolysis bleaching Initial weight (gram) 100 100 20 20 Final weight (gram) 70.9 46.4 18.22 15.4 NaOH + Na 2S (gram) 36.828 99.9 0.96 …… Water to make liquor 400 400 80 320 (mL)

Washing water(ml) 2000 1600 1000 1200

H2O2 (gram) ------0.12 0.022 NaOCl (gram) …… ……. …… 1.5 NaOH(gram) …… ……… …… 1

3.8. Cost Effectiveness and Selected Equipment Company which is located at Wonji. This factory has a Design of the Process production capacity of 8,000-10,000 tones, annually. The supply of paper in Ethiopia is dominated Due to the limited production capacity of the country's by imported products. The only paper producing sole producer of paper, the country imports a large factory in Ethiopia is Ethiopian Pulp and Paper Share quantity of paper from oversees. The information (data

Atnafu Guadie et al., Page No. 35 International Journal of Environmental Science and Technology, 2015, 1(2),20-26

of 2005 E.C) gathered from Ethiopia Pulp Factory considering the annual pulp demand of existing paper shows that the raw material (pulp) demand of the factory of the country. factory is about 10,000 -15,000 tons per year. This The digester which is suitable to the reaction is limited production of the country is due to lack of raw mixed flow reactor. The production design is to have material (pulp) in the country national wide. The supply eight batches per day with three hours resident time in of kraft paper in Ethiopia is through import. The the cooker (reactor). From annual production of 10,000 information obtained from external trade in (2000 E.C) tons of pulp, we can have the amount produced statistics gives that the present effective demand for 28,571.4 kg/day (3,571.4 kg per batch) of pulp. To kraft paper is estimated to be 5,504 tones. Design obtain 3,571.4 kg per batch of pulp we have to use () of major equipments that are used in eucalyptus 11916.68 kg of eucalyptus wood chip for single pulp production is performed based on experimental process and 14116.32 kg of eucalyptus wood chip for result and the equipment capacity should be scaled up sequentially bleach process.

Table 7 Annual materials requirement in tones and cost Description Quantity Unit price Total cost (birr) Wood chip 18,750 200 3750 NaOH 2010 4360 8763.6

Na 2S 13.7688

H2O2 14.2 NaOCl 15 CaO 101.25 1200 121500 Electricity 10,500,000 (KWh) 0.335 Water 750000 (m 3) 1.5 Chemicals are also required in the pulp making process. recovered lignin is composed of guaiacyl and syringyl These include caustic soda, Sodium sulfide, sodium structures, typical for lignin of hard wood pulp. Peak hypochlorite, starch, hydrogen peroxide and lime. The intensity changes in the spectra of recovered lignin, process is economically effective. single and sequentially bleached pulps point out 4. Conclusions degradation and condensation processes during The Kraft pulp is lignin free and can be used in bleaching and lignin extraction. The UV-Visible making high quality writing and printing papers that are spectrums of single and sequential bleached pulps both coated and uncoated. The result obtained after indicate the lignin purity of the pulps based on the bleaching process was close to the expected result value of absorbance. The UV-Visible graph of the which has less lignin content pulp with a kappa number bleached pulps, transparent at visible region indicates of 20.8, 9.834, 7.7 and 5.9 for prehydrolyzed, cooked, the brightness of the pulps. The physical test parameters single bleached and sequentially bleached eucalyptus such as tensile strength, tear strength, porosity, bursting pulp respectively. The sequential bleaching process strength, bulkiness and thickness obtained from the produces a brightest pulp which is an efficient method instrumental readings were closer with the standards of than the single bleaching ones. The FTIR spectrum of the pulp and paper factories. In this study, the Kraft single and sequentially bleached pulps showed that the process in manufacturing pulp from eucalyptus is chemical treatments could successfully be used to generally a suitable process with cost effective due to remove lignin and hemicelluloses. An increase in the the cheapest raw material used and the recovery of the cellulose content in each chemical treatment observed used chemicals. at the major peaks in the spectrum indicating cellulose 5. References functional groups. Band intensity changes in the spectra 1. Lidia, T., Chemical and Biochemical engineering reflect the sequential bleached pulps have an intense division of chemical technology , 1-70, 59, 2006. and sharper peaks than single bleached once which 2. Hille, H. M., Journal of pulp and paper production , indicates the increase of cellulose content up on 1-17, 4(4), 2008. sequentially bleached eucalyptus pulp. 3. McGraw-Hill, Encyclopedia of Science and The FTIR spectrum of recovered lignin agrees Technology, 7 th ed, 13. New York, 1992. closely with certain values for functional groups of hard 4. Dhamodaran, T. K. and Gnanaharand, R. , Journal wood pulp lignin. IR spectrum indicates that the of kerala forest research institute ,1-208, 680, 2003.

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5. Gary, A. S., Hand Book for Pulp and Paper 15. Gary, C. C., Arttu, M., Cris, L. and Luengo, H., Technologists, 3 rd ed, Angus Wilde Publications Paper and Fibre Research Institute ,1-19, 2008. Inc, 1934. 16. Taylor & Francis Group, Journal of Wood 6. Antti, p., Julie, V. and Pasi, S., Chemical Review, Chemistry and Technology , 1-25, 31, 2011. 112:1-12, 2000. 17. Mehdi, J., Jalaludin, H. and Kirstiina, O., Institute 7. Honghai, Z. Isolation and functional genetic of tropical forestry and forest products , 1-14, 2011. analysis of eucalyptus wood formation genes. 18. Rastislav, S. and Bozena, K., Cellulose Chemical M.Sc. Thesis, Department of Genetics, University Technology , 163-177, 43(4-6), 2009. of Pretoria, Pretoria, 2005. 19. Sanni, R. and Minna, P., Silvafennica , 351-371, 8. Lewis, D. The 36 th international pulp and paper 41(2), 2007. congress and exhibition of a comparison of pulping 20. Sarwar, J. and Wang, H., Cellulose Chemical and bleaching of kraft soft wood and eucalyptus Technology , 261-267, 46(3-4), 2012. pulps. October 13-16, 2003, Sao, Brazil. 21. Sandra, S., Nagila, M., Ricardo, P. S., Steven, J. 9. EPA US, Journal of research triangle park , 1-62, and Frank, H., European Polymer Journal, 737- 277(11), 2010. 745, 37(2001), 2000. 10. John, K. R. and Richard, R. G., Journal of 22. Mohamad, I. and Chuah, S.B., Journal of School of forestery ,1-15,6(6), 2010. Chemical Sciences , 57-67, 2, 2004. 11. Antti, H. A., Sjostrom, D. and Wallback, M. 23. Svetlana, P. Extraction and examination of residual Journal of forestery , 102-108, 83(3), 2000. lignin from sulphate pulp. MSc thesis, Luleå 12. Celso, F., Advances in eucalyptus fiber properties University of Technology, Sweden, 10(129):1402- & paper products. Porto Alegre, Brazil, 1-6, 2007. 1552, 2010. 13. Sevtlana, P., Journal of chemical engineering and 24. Archard, M. and Michell, A. J., Diffuse reflectance Geosciences , 1-45, 129, 2010. ultraviolet spectroscopic studies of paper. 14. Yusra, F. A. S. Methods of extracting cellulosic Application note at division of forestry and forest material from olive pulp. MSc thesis, An-Najah products,1-6, 2012. National University, Palestine, 2009.

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