Bioresource Technology

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1 Bioresource Technology 101 (2010) Contents lists available at ScienceDirect Bioresource Technology journal homepage: Effect of different locations on the morphological, chemical, pulping and papermaking properties of Trema orientalis (Nalita) M. Sarwar Jahan a,b, *, Nasima Chowdhury a, Yonghao Ni b a Pulp and Paper Research Division, BCSIR Laboratories, Dr. Qudrat-E-Khuda Road, Dhaka 1205, Bangladesh b Pulp and Paper Research Centre, University of New Brunswick, Fredericton, Canada article info abstract Article history: Received 24 August 2009 Received in revised form 1 October 2009 Accepted 13 October 2009 Available online 14 November 2009 Keyword: Trema orientalis, Variation of wood properties Stem and branch Pulping and bleaching The chemical compositions and fiber morphology of stem and branch samples from Trema orientalis at three different sites planted in Bangladesh were determined and their pulping, bleaching and the resulting pulp properties were investigated. A large difference between the stem and branch samples was observed. The stem samples have consistently higher a-cellulose and lower lignin content, and longer fibers than the branch samples in all sites. T. orientalis from the Dhaka and Rajbari region had higher a-cellulose content and longer fiber length, resulting in higher pulp yield and better papermaking properties. The T. orientalis pulp from Rajbari region also showed the best bleachability. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction * Corresponding author. Address: Pulp and Paper Research Division, BCSIR Laboratories, Dr. Qudrat-E-Khuda Road, Dhaka 1205, Bangladesh. Fax: address: sarwar2065@yahoo.co.uk (M.S. Jahan). The increased demand for wood and fiber and declining availability of wood supplies have prompted investigations into the potential of fast-growing species as raw material for the pulp and paper industry. Among them, Eucalyptus, Acacia have received much attention (Colodette et al., 2000; Cossalter and Smith, 2003; Downes et al., 2003; Edgrard, 1999; FAO, 2005, 2009; Khristova et al., 1997; Malinen et al., 2006; Patt et al., 2006; Santiago and Neto, 2008a,b). Trema orientalis is also a fast-growing species and can be harvested in 3 4 years for valuable pulpwood (Jahan and Mun, 2003). Many studies have been carried out to evaluate some fast growing wood species for the pulp and paper industry (Edgrard, 1999; Fidel and Tamayo, 2003; Jahan and Mun, 2003, 2004; Jahan et al., 2007, 2008a; Khristova et al., 1997; Malinen et al., 2006; Lei et al., 2006; Zhu et al., 2005). Triploid Populus tomentosa a hybrid poplar has received much attention recently and it can be made into chemical and mechanical pulp with quality (Chen and Mao, 2000; Zhu et al., 2005; Yang et al., 2006). Fidel and Tamayo (2003) determined the chemical composition of plantation grown Acacia mangium, and the results showed that the Philippine mangium s chemical composition resembled closely to those of Malaysian-grown mangium and other fast-growing plantation species, including the traditionally-used pulpwood of the Philippines. The T. orientalis is among the fastest growing trees in the tropical and temperate regions and produce wood that can be widely used by the paper industry. It is a native species grows in many places in Bangladesh. At present it has no industrial use. In earlier studies, we introduced this species as a pulping raw material (Jahan and Mun, 2003, 2004; Jahan et al., 2008b). T. orientalis was characterized with high a-cellulose content. Pulp yield and paper making properties were comparable to the Gmalina, which is presently used by the Kharnaphuli Paper Mills in Bangladesh. Due to the differences in climate, soil and others, it is likely that the chemical, physical and morphological properties of the same wood species but at different locations, are different, therefore affecting pulping and papermaking properties. For example, Goyal et al. studied the variability in pulping and fiber characteristics of hybrid poplar due to their genetic makeup, environmental factors and tree age (Goyal et al., 1999). In this paper, we determined the potential of T. orientalis collected in three different locations in Bangladesh, as potential raw material for pulping and papermaking. The physical, chemical and morphological properties of the stem and branch samples were carried out. The kraft and soda-anthraquinone (AQ) pulping trails of these raw materials were conducted. ECF bleaching T. orientalis pulps from different sites and stem and branch was also evaluated /$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi: /j.biortech

2 M.S. Jahan et al. / Bioresource Technology 101 (2010) Methods 2.1. Material The T. orientalis samples (4 years old) were collected from the Dhaka, Gaibandha and Rajbari districts in Bangladesh. Three trees in each location were selected. The stem samples were prepared by removing 2 ft from top and bottom, while the branch samples were prepared by removing 1 ft from the terminal. For the pulping experiments, the debarked log was chipped to cm size by hand. For the chemical analysis, the wood chips were ground in a Wiley mill and the mesh size fraction was used Analysis for chemical, morphological and physical properties The basic wood density was determined according to PAPTAC Standard A. 8P. For the measurements of fiber length, the sample was macerated in a solution containing 1:1 HNO 3 and KClO 3. The macerated sample was taken in a slide and the fiber length was measured under a profile projector (Nikon V-12, Japan). The fiber diameter was measured in an image analyzer. The chemical compositions were carried out by following Tappi Test Methods: the extractive (T204 om88), 1% alkali solubility (T212 om98), water solubility (T207 cm99), Klason lignin (T211 om83) and ash content (T211 os76). The holocellulose content was determined by treating the extractive free wood meal with NaClO 2 solution Browining (1976). The ph of the solution was maintained at 4 by adding a CH 3 COOH CH 3 COONa buffer and the a-cellulose content was determined by treating the holocellulose sample with 17.5% NaOH (T203 om93) Pulping The kraft pulping was carried out in a thermostatically controlled electrically heated digester. The capacity of the digester was 5 l. The normal charge was 300 g of oven dried (o.d.). The pulping conditions were as follows: Active alkali was 16 20% on oven-dry (o.d) raw material as Na 2 O. Sulphidity was 25% (for kraft process). AQ was 0.1 on od raw materials (soda-aq process). Cooking time was 120 min at maximum temperature (170 C). Ninety minutes were required to raise the maximum temperature (170 C) from a room temperature. Liquor to wood ratio was 4. At the completion of cooking, the pulp was thoroughly washed, and screened in a flat vibratory screener (Yasuda, Japan). The screened pulp yield, total pulp yield and screened reject were determined gravimetrically as the percentage of oven dried (o.d.) raw material. The kappa number of the resulting pulp was determined in accordance with Tappi Test Methods (T236 om99). Three replicates were done and the average reading was taken. The accuracy of data was 95% Evaluation of pulps Pulps were beaten in a PFI mill to different revolution and handsheets of about 60 g/m 2 were made in a Rapid Köthen Sheet Making Machine. The sheets were tested by following Tappi Standard Test Methods: tensile (T494 om96), burst (T403 om97), tear strength (T414 om98), folding endurance (T511 om96) and brightness (T525 om92) DE p D bleaching The brown stock samples were bleached in a D o E p D bleaching sequence. The kappa factor was 0.20 in the first D o stage. Other conditions were: 70 C, 5% pulp consistency, 60 min. The initial ph was adjusted to 2.5 by adding dilute H 2 SO 4. The conditions for the E p stage were: 70 C, 60 min, 10% pulp consistency, 2% NaOH and 0.2% H 2 O 2. The conditions for the D 1 stage were: 3.5 end ph, the ClO 2 charge in the D 1 stage was one half of that in the D o stage. The brightness and viscosity (T230 om99) of the bleached pulp were determined in accordance with Tappi Test Methods. 3. Results and discussion 3.1. Chemical, morphological and physical properties A complete wood chemical analysis was performed to determine the differences in chemical composition of T. orientalis in relation to sites and stem and branch. Table 1 gives a summary of these results. The a-cellulose content of a raw material, which is directly correlated with pulp yield, varied significantly among these sites. The a-cellulose content varied significantly among these sites. The highest content of a-cellulose (45%) was observed in stem from Dhaka and Rajbari, while the lowest content of a-cellulose (41%) was observed in branch from Dhaka region. Similar differences of T. orientalis branch and stem from Taiwan were Table 1 Chemical, physical and morphological properties of stem and branch of T. orientalis from different sites. Dhaka Gaybandha Rajbari Stem Branch Stem Branch Stem Branch Extractives, % Acetone 0.89 ± ± ± ± ± ± 0.05 Cold water 2.4 ± ± ± ± ± ± 0.4 Hot water 4.9 ± ± ± ± ± ± 0.6 1% Alkali 21.4 ± ± ± ± ± ± 1.2 Lignin, % Klason 24.1 ± ± ± ± ± ± 1.1 Acid soluble 2.8 ± ± ± ± ± ± 0.4 Pentosan, % 23.5 ± ± ± ± ± ± 1.0 a-cellulose, % 45.0 ± ± ± ± ± ± 1.0 Ash, % 1.1 ± ± ± ± ± ± 0.02 Density, g/cc ± ± ± ± ± ± 0.04 Fiber length, mm 1.34 ± ± ± ± ± ± 0.03 Fiber diameter, lm 24.5 ± ± ± ± ± ± 0.9

3 1894 M.S. Jahan et al. / Bioresource Technology 101 (2010) noted (Ku et al., 1987). Generally the a-cellulose content in branch is lower than that in stem. The average Klason lignin content in T. orientalis was 23 25%, which is consistent with other reported data for T. orientalis planted in other regions (Ku et al., 1987), higher than the Acacia auriculiformis (Jahan et al., 2008a), A. mangium (Law and Daum, 2000) and the Eucalyptus globules (Santos et al., 2008), but lower than the Eucalyptus camaldulensis (Fatehi et al., 2009). The lignin content in branch was slightly higher than stem. There is no significant difference of Klason lignin content among these three regions. The variation of total lignin content (acid soluble and insoluble) content in T. orientalis from different sites was similar trend to that of the wood extractives. The lower wood density demonstrated increased amounts of lignin found in the wood. The pentosan content did not vary significantly among the sites and stem and branch. It was about 21 23%, which was higher than that of A. mangium and A. auriculiformis (Malinen et al., 2006; Jahan et al., 2008). The maximum amount of ash content was found in Rajbari stem (1.2%) and the lowest amount found in Rajbari branch (0.7%) and it was within the other tropical species (Khristova et al., 1997). The extractives contents, including those from acetone, cold water, hot water and 1% alkali, are all higher in the branch samples than the stem samples. The 1% alkali solubilities in stem varied between 21% and 24%, while in branch it varied between 25% and 27%. This difference may be due to the differences in weather and soil conditions associated with the specific region. Extractives of a raw material are undesirable parts since they can have negative impact on pulping and bleaching operations. For example, a higher extractive content, in particular, 1% alkali solubility may lead to a lower pulp yield from the kraft and soda pulping processes. The 1% alkali solubilities in Table 1 were lower than those of A. auriculiformis (Jahan et al., 2008). As shown in Table 1, the wood density results of branch samples were slightly lower than those of the corresponding stem samples. Similar results were observed by Ku et al. (1987) for T. orientalis and other fast-growing species. The wood density of T. orientalis was in general, lower than the other fast-growing species (Miranda et al., 2001). The fiber length is recognized as an important parameter for pulp and paper properties, for example, it has a significant impact on the paper strength and paper machine runability (Jackson, 1988; Watson and Dedswell, 1961). Table 1 also shows the fiber length of stem and branch samples of different sites. The stem samples showed consistently longer fibers than the branch samples, which is consistent with other wood species (Miranda et al., 2001). The sample from Dhaka region exhibited longest fibers (1.34 and 1.00 mm, respectively, for the stem and branch samples) in comparison with Gaibandha and Rajbari regions Pulping Both kraft and soda-aq pulping processes at various active alkali charges were studied and the results are shown in Tables 2 4. The pulp yield results from the stem samples were significantly higher than those from the branch samples, which are expected because of the higher a-cellulose content in stem samples. The total pulp yields in Dhaka region T. orientalis were 51 49% and 49 47% in the kraft process for the stem and branch, respectively, while they were 46 44% and 42 35% in the soda-aq process. No reject was obtained in the soda-aq process. In the kraft process, the rejects were decreased and screened pulp yield increased with the increase of alkali charge in both stem and branch. In the kraft process 20% alkali charge was required to reach the target kappa number of 20, while in the soda-aq, the required alkali charge was 16%. At the same kappa number of 20, the total pulp yield difference became minimize and reached to 2% for stem and 4% for branch (Figs. 1 and 2). The samples from the Rajbari region showed the highest pulp yield in comparison with those of Dhaka and Gaybandha region, which is consistent with the fact that the Rajbari region T. orientalis had the highest a-cellulose content among these three sites. Pulp Table 2 Pulping of T. orientalis from Dhaka region stem and branch in kraft and soda-aq processes. Stem Branch AA Na 2 O SPY KN Rev TI TenI BI Fold SPY, screened pulp yield; KN, kappa number; Rev, PFI revolution required to get 0 SR 30; TI, tear index (mn m 2 /g); TenI, tensile index (N m/g); BI, burst index (kpa m 2 /g); fold, double fold number. Table 3 Pulping of T. orientalis from Gaybandha region stem and branch in kraft and soda-aq processes. Stem Branch AA Na 2 O SPY KN Rev TI TenI BI Fold

4 M.S. Jahan et al. / Bioresource Technology 101 (2010) Table 4 Pulping of T. orientalis from Rajbari region stem and branch in kraft and soda-aq processes. Stem Branch AA Na 2 O SPY KN Rev TI TenI BI Fold Fig. 1. The total pulp yield kappa number relationship of different region T. orientalis in kraft process. Fig. 2. The total pulp yield kappa number relationship of different region T. orientalis in the soda-aq process. yield of unbleached pulp at kappa number 20 was measured from the pulp yield kappa number plot in different alkali charge (Figs. 1 and 2) to evaluate the impact of sites of T. orientalis and shown in Fig. 3. T. orientalis from Gaybandha had 4.5% lower pulp yield than the Rajbari and 3.0% than the Dhaka and for stem. It has been demonstrated that kraft pulp yield is directly proportional to the alphacellulose content of the wood (Hale, 1959). Pulp yield data were slightly lower than that reported of Eucalyptus globulus (Fatehi et al., 2009). At kappa number 20, pulp yield from stem in soda- AQ and kraft process was almost similar in Gaybandha region, while soda-aq process yielded 0.5% higher pulp yield than that of kraft process from the stem of Rajbari region. The branch samples have consistently lower pulp yield and higher kappa number than the stem samples for all the three sites. Such differences can be explained by the differences in the lignin content of these raw materials (Table 1), i.e., consistently higher lignin content in

5 1896 M.S. Jahan et al. / Bioresource Technology 101 (2010) Fig. 3. Pulp yield of stem and branch of T. orientalis from different sites at kappa number 20. the branch than in the stem. The pulp yield from T. orientalis is lower generally than the Eucalyptus (Colodette et al., 2000; Guerra et al., 2008) and higher than another fast-growing species Paulownia (Ates et al., 2008). Under different alkali charge, the kappa number of the pulps from different sites was in the range of (Tables 2 4). The kappa number of the stem is lower than that of the branch from the same site. These results suggest that the stem is easier to delignify than the branch. Among these three sites, the samples from Rajbari region is the easiest to delignify, which is due to the lowest lignin content (Table 1). It may be noted that the klason lignin content may not affect the delignification rate, other factors, such as wood density may be more critical in determining delignification rate, for example, Mortha et al. (1992) suggested that hybrid poplar for its higher delignification rate in kraft process is due to its lower wood density, so that the diffusion of lignin out of the wood chips can be explained. Our present data support the same hypothesis. The lowest density of branch from Dhaka region T. orientalis produces pulp with the highest kappa number. Another explanation could be that the lignin structure of these sites is different. Nimz et al. (1983) reported that b-o-4 linkages in guaiacyl units are hydrolyzed at a slower rate than syringyl units. A straight line correlation between delignification rate and the ratio of syringyl to guaiacyl propane units was also obtained by Chang and Sarkanen (1973). Since the syringyl content of a typical hardwood can vary from 20% to 60% (Fengel and Wegener, 1989), the higher rate of delignification is most likely due to higher syringyl contents in the native lignin of T. orientalis from Rajbari Papermaking properties Depending on the end use of the pulp, the strength properties of a pulp might also play a significant role in selection criteria. For evaluating papermaking properties, pulps were beaten in a PFI mill for different revolutions and handsheets were prepared. The physical properties at 0 SR 30 were obtained from extrapolation. The number of PFI revolution required to reach target 0 SR 30 varied from 1320 to 1510 revolution depending on sample location and whether it was from stem or branch (Table 5). The pulp made from branch required less refining than the stem pulp. The strength properties tear, tensile and burst indexes at 0 SR 30 are also presented in Table 5. A significant difference exists among the sites and also between the stem and branch samples of the same site. The tensile index of stem pulp from Dhaka region was 4.1% higher than that of branch, while the stem samples from Gaybandha and Rajbari was 10.0% and 5.2% higher than that of the branch samples, respectively, in the kraft process. The tear index also showed a variation among the sites. A stem pulp showed a higher tear index than a branch pulp. The higher tear and tensile indexes for the stem pulp are due to longer fiber lengths (Table 1). Pulp from Dhaka region stem had the highest tear index (12.7 mn m 2 /g) in the kraft process, which is mn m 2 /g higher than that of Gaybandha and Rajbari stem pulp. The branch pulp from Dhaka region had the lowest tear index (8.4 mn m 2 /g) and the Gaybandha region branch pulp had the highest tear index (10.7 mn m 2 /g) from the kraft process. The soda-aq pulp showed inferior tear index than the kraft pulp. The burst index is not affected by environmental factors (Table 5). Slight variation of burst index was observed between stem and branch. Table 5 Physical properties (at 30 0 SR by extrapolation) of stem and branch pulp from T. orientalis obtained from different regions at kappa number 20 by extrapolation. Dhaka region Gaybandha region Rajbari Kraft SAQ Kraft SAQ Kraft SAQ Stem Branch Stem Branch Stem Branch Stem Branch Stem Branch Stem Branch Rev TI Ten BI

6 M.S. Jahan et al. / Bioresource Technology 101 (2010) Table 6 Bleachability of T. orientalis pulp from different region in Bangladesh. Brightness, % Viscosity, mpa s Dhaka Stem Branch Gaybandha Stem Branch Rajbari Stem Branch Bleaching In recent years chlorine dioxide is completely taking place of elemental chlorine in the production of bleached chemical pulp to minimize the environmental impact. Chlorine dioxide is effective in delignifying as well as brightening chemical pulp. Unbleached pulps, with different kappa number, obtained from three different sites from stem and branches were submitted to a conventional ECF sequence (D o E p D 1 ). Brightness of pulp was increased with the increase of alkali charge during pulping (data not shown). This can be attributed by higher kappa number of brownstock pulp. Bleachability tends to decrease as the kappa number increases (Jahan et al., 2008). In order to evaluate the bleachability of these pulps, brightness was measured at kappa number 20 from extrapolation, where the same amount of chemicals were used. The results of bleaching experiments are presented in Table 6. Pulp from Rajbari region showed better bleachability than that of Gaybandha and Dhaka region. Branch pulp responded slightly better bleachability than that of stem pulp. Kraft pulp showed better bleachability than soda-aq pulp. The kraft pulp from Gaybandha and Rajbari region had % higher brightness than the corresponding soda-aq pulp. Lina and Leelo (2002) showed that the higher bleaching chemical was required when AQ was used in cooking. Francis et al. (2006) also observed that the soda-aq pulp was difficult to bleach. Branch contains higher extractives, which also affects bleachibility (Table 1). But this effect is not pronounced here. The residual lignin structure may affect the bleaching. It needs to be studied. The viscosity of bleached pulp was also dependent on the samples origin. The viscosity of the stem pulps was higher than the viscosity of the branch pulps ( verses mpa s). There was no significant difference observed between the viscosities of kraft and soda-aq pulps. 4. Conclusions We reached the following conclusions based on our research: T. orientalis from three sites investigated showed variations in density, chemical properties and fiber morphology, which could significantly affect pulp production. Extractives in branch are higher than that stem. Stem contained higher a-cellulose, lower lignin and larger fiber length than the branch. Stem pulp showed higher yield and lower kappa number than the branch pulp. Papermaking properties of stem pulp also better than branch pulp. Dhaka region T. orientalis showed better pulp yield and papermaking properties. Surprisingly the bleachability of branch pulps were better. 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