Available online at http://www.urpjournals.com
International Journal of Fiber and Textile Research Universal Research Publications. All rights reserved
ISSN 2277-7156 Original Article Fiber morphology and Pulping study of Banana Pseudo-stem 1,2
M. Z. H. Khan*, 3M. A. R. Sarkar, 4Md. Forhad Ibne Al Imam,1Raimo O.Malinen 1 Dept. of Pulp and Paper Technology, Asian Institute of Technology (AIT), Thailand 2 Dept. of Chemical Engineering, Jessore Science and Technology University, Jessore 7408, Bangladesh 3 Dept. of Genetic Engineering & Biotechnology, Jessore Sci. and Tech. University, Jessore 7408, Bangladesh 4 Dept. of Mechanical Engineering, Pabna Polytechnic College, Pabna, Bangladesh *corresponding author: Dr. M. Z. H. Khan, Email: [email protected]
Received 03 March 2013; accepted 05 April 2013 Abstract This study deals with the determination of chemical composition, fiber morphology, and the pulping potentialities of banana pseudo-stems growing in Thailand. Banana stem was cooked by Kraft process with different chemical charges and a wide range of time and temperature, and the optimal pulping conditions were established. The lignin and extractive content was found low. The only discouraging finding was the relative high amounts of ash and water solubility of raw material. Unbleached banana kraft pulp in the kappa number range of 23-28 was not easy to bleach with three stages sequence of D0-EP-D1. Kappa number, yield, viscosity is used to describe the extent of lignin removal in the cooking process. © 2013 Universal Research Publications. All rights reserved Keywords: Banana stem; fiber morphology, chemical composition; kraft pulping; bleaching. 1. Introduction In view of the shortage of conventional raw materials for pulping and the increasing demand for paper products worldwide, non-wood plants and agricultural residues attracted renewed interest. Non-wood plants offer several advantages including short growth cycles, moderate irrigation and fertilization requirements and low lignin content resulting to reduced energy and chemicals use during pulping [1, 2]. Today, most modern pulp and paper enterprises rely on wood . Many non-wood fibers, such as bamboo, jute, straw, rice, abaca and bagasse, are currently used in small commercial pulping operations . Other agricultural residues such as banana stem possess characteristics suitable for paper making [5, 6]. Banana is one of the important fruit and vegetable crop plants and belongs to the genus Musa. Other well-known species are abaca (Musa extilis) and other wild banana plants used as a source of fibers for the paperand cordage industries [7,8]. Banana pseudo stem has been known as a potential cellulose source, though usually discarded as agricultural waste in many countries. The composition of banana pseudo stem obtained by elemental analysis, as determined by Bilba etal. . Despite low lignin content, the delignification of banana stems appears difficult. However
some authors think banana stem can give a high quality specialty fibre with high yield if the preparation of the material is adequate. Heikal et al. compared the kraft  and nitric acid  pulping of retted and unretted banana chips. They reported that pulping of retted samples gave pulps with better chemical and strength properties than that from unretted samples. Banana stem pulping has been the subjected to conflicting reports that showed pulping agent like caustic soda, caustic soda and sodium sulphiteor calcium bisulphite do not produce an easily bleachable pulp . The use of renewable agricultural by products for pulp production as non-wood cellulosic fibers would be great advantage for countries with limited wood forests, and would increase the profit of farmers in developing countries [13,14]. This fact was mainly motivated by the increasing consumption of wood fiber based products, such as panel, composites, textile grade fibers, paper and boards .This demand is currently solved by using increasing amount of recycle fibers . In this study we examined a wide range of cooking conditions for banana fiber pulping. The extraction of fiber from the pseudostem is not a common practice and much of the stem is not used for production of fibers. The behaviour of the fibers also gives important hint regarding their
International Journal of Fiber and Textile Research 2013; 3(1): 31-35
subsequent behaviour as reinforcement in composites. The effects of different cooking on fiber properties were also studied. The detailed comparison study was done between the fiber properties of banana fiber with others. 2. Experimental 2.1 Raw Material: The raw material used for this research was whole length banana stem. Banana stem was collected from a common species in Thailand. This type of banana plant is generally growing all over the country. The stem was cut from plant and chopped in small pieces (2-3 inch) and let it sun dry for about 3/4 days in the open air. After sun dried the OD measurement had done and prepared it for cooking. 2.2 Pulping: Cooking: Five cooks were done in an air bath digester of six autoclaves. Cooking liquor was prepared from solid NaOH pallets by dissolving them in water and concentration of NaOH was determined (SCAN-N 2.88). Since the packing of raw material very low, only 100g (as OD) per each autoclave could be used for cooking in digester. 2.3 Bleaching of Chemical Pulp: Bleaching sequence and conditions have been given in Table 3.3. Bleaching was done after oxygen delignification. Pulps were taken in plastic bags in a water bath. Bleaching chemicals and water were added into pulp together and the mixture was heated near to reaction temperature in microwave oven. Pulp was mixed well during bleaching
time every 15 minutes. After every stage pH of filtrate was measured and after D stages residual chlorine was determined. Pulp was then washed by diluting and dewatering procedure; first it was diluted to consistency 5% and then dewatered. 3. Results and Discussions 3.1 Chemical composition and fiber morphology of banana stem fiber: Chemical Composition: The chemical composition of banana stem fiber is shown in Table 1. The first remark concerns the high amount of ash (approximately 16%) which is common for annual plants. The ash content is high for industry processing. The second remark is the low amount of lignin, i.e. approximately 15%, to compare with other annual plants. In spite of high content of ash, this raw material is worth pulping, mainly because of its relatively low lignin content. The quantity of extractives in Methanol/Benzene (1:2) was 3.52% that is medium when compared with other wood and some other annual plants. Holocellulose is a collective term referring to the entire polysaccharide portion of wood. Another important remark is high water solubility (approximately 15%). This is one of the reasons why the total yield after cooking is low. As the water solubility is high, for this reason we analyze extractive after passing the sample through water solubility analysis. The experiments provided basic and important information on the usability of banana fiber for paper making.
Table 1: Chemical compositions of banana stem fiber Raw material Banana stem
Hollocellulose (%) 61.5
Lignin (%) 14.9
Pentosans (%) 12.8
Comparison of chemical composition between banana fibers together with other general raw materials: The chemical composition and solubility results of banana fiber with other common raw materials shown in Fig.1 below –
Figure 1: Chemical composition and solubility of banana stem fiber together with some other raw materials Banana stem fiber had the lowest lignin content followed by other general raw materials (Fig. 1). The most striking result is that banana stem fiber has high ash content. Another important thing is water solubility of banana fiber.
Extractives (%) 3.52
Water solubility (%) 14.91
Banana fiber has a much more hot water solubility than other raw materials. Fiber Morphology: The chemical composition of the pulps has a strong influence on the fiber properties. Cellulose is the main strength-giving component, hemicelluloses are softeners in the wet state, and lignin gives wet stiffness and resistance to strength development through refining. The amount of lipophilic extractives in pulp is always rather small but they may still be quite disturbing. Fiber morphology is a dominating factor for pulp quality (both the structure of the fiber wall and the fiber dimensions). Fiber length and coarseness are important quality criteria asis the heterogeneity of the fibrous material. In these respects there is a fundamental difference between softwood and hardwood pulps which determines how they are used. The result of fiber analysis of banana stem fiber is shown in Table 2. The average fiber length of banana stem fiber was found to be around 1.7 mm. Banana fibers have shown high variability along the length and between fibers, which is a characteristic of natural fibers. The standard deviation has been found to decrease with increasing diameter of fibers. The diameter variability had a normal distribution.
Table 2: Fiber analysis result based on Length weighted average values Name of Sample Fiber length Fiber width Banana stem
Ash (%) 15.7
International Journal of Fiber and Textile Research 2013; 3(1): 31-35
Comparison of fiber characteristics between banana fibers shows fiber morphology of banana stem fiber compared together with other general raw materials: Below Table 3 with other common raw materialsTable 3: Fiber characteristics of banana fiber compared to other general raw materials Raw material Sisal Eucalyptus Soft wood Bamboo Hard wood Banana stem
Fiber length (mm) 3 1.0-1.1 2-3.5 2.7 0.7-1.6 1.7
Fiber width (µm) 20 9-10 30-45 14 16-25 31.4
Coarseness (mg/m) 0.104 0.074 0.160-0.340 0.070-0.12 0.15
The general morphology of the fibrous elements of banana stem is presented in Fig.2. It is evident that the figure represents in fact a variety of cells of very different size, form and structure, and each cell has a different role on a fibrous network. Here, in the term fiber used is meant to include all types of cells found in the material.
Figure 4: Effect of alkali (AA) charge on screening reject Figure 2: Cells from the stem of Banana (Image taken from L & W fiber analyzer) 3.2 Chemical Cooking and Bleaching Chemical cooking of Banana stem fiber and pulp characteristics: A wide range of yield (19-41) % was found with the mentioned chemical charge with different cooking conditions. Considering chemical charge, yield, kappa number, viscosity etc., 14 – 18 % AA charge seems to be the reasonable range. Yield decrease with increase of chemical charge (Fig. 3). High temperature and long time (170oC and 120 min) is required for maximum yield. Because of the bulky nature of the banana stem, it is necessary to maintain the liquor/matter ratio for uniform chip impregnation and solubilization of the dissolved matter (lignin and hydrolyzed hemicelluloses fragments). So the higher cooking liquor content allowed improving simultaneously the pulping and the yield of the pulp. Screening reject decreases with increase of chemical charge. At the same chemical charge screening reject is low if H-factor is high. Also total yield is low when screening reject is low. That means at high H-factor cellulose degrades. The effect of alkali charge on screening reject has been shown below (Figure 4).In case of chemical pulping the screening reject was found 5-14 %, which seems very high. At high chemical charge reject is lower.
Because of the bulky nature of the banana stem, it is necessary to maintain the liquor/matter ratio for uniform chip impregnation and solubilization of the dissolved matter (lignin and hydrolyzed hemicelluloses fragments). So the higher cooking liquor content allowed improving simultaneously the pulping and the yield of the pulp. Figure 5show that the residual alkali concentration at the end of the lower cook zone (at the end of bulk delignification) shows a good correlation with cellulose yield. Cellulose yield increases by decreasing the residual alkali concentration regardless of cooking temperature. Black liquor pH increases with the increase of chemical charge. Residual alkali charge increases with the increase of active alkali (AA).
Figure 5: Effect of alkali (AA) charge on residual alkali (RA) in black liquor
Figure 3: Effect of alkali (AA) charge on yield (Condition: Figure 6: Effect of alkali (AA) charge on Kappa Number 14 % AA, 1700C, 120 min) International Journal of Fiber and Textile Research 2013; 3(1): 31-35
The effect of alkali charge on kappa number was shown in Fig. 6. Kappa number decreases very slowly with increase of chemical charge. Temperature and time has little effect on kappa number. H-factor does not affect much kappa number with same chemical charge. The positive impact of cooking to a higher kappa number on the unbleached pulp viscosity was shown in Fig. 7 and can be explained by the higher pulp viscosity. Due to the fact that the viscosity loss during the cooking is affected in a similar way for both high and low kappa pulps, a higher unbleached viscosity is obtained from a high kappa pulp.
Figure 7: Effect of kappa number on pulp viscosity
Figure 8: Effect of kappa number on yield
Table 4: Bleaching result after every stage Parameter D0 EP D1 Residual ClO2 (g/l) 0.064 Residual H2O2 (g/l) 0.012 Kappa Number 14.90 11.21 6.4 Brightness % ISO 19.36 32.34 44.81 Viscosity 790 620 585 End pH 5.91 Bleaching increase brightness as well as reduces the viscosity and yield of bleached pulp. The brightness and viscosity of pulp depend on the initial kappa number and initial viscosity of pulp and the amount of bleaching chemical charge in the process. Higher chemical charge in the bleaching of better quality unbleached pulp provides high brightness with high yield and acceptable viscosity. Loss of pulp during washing is also a reason of low yield pulp after every bleaching stage. Even though high chemical charges used for this bleaching program, the kappa was still high after D1 stage (kappa 6.4) with a high end pH. Conclusion Banana fiber at present is a waste product of banana cultivation and either not properly utilized or partially done so. The main objective of this study was to establish the suitability of banana stem fiber as a potential source of lignocellulosic fibers for paper making. This study shows that banana stem fiber had a lower lignin content but very high ash content compared with other general raw materials. Its average fibre length was found (1.7 mm). The highest yields 48.61% can be prepared with a relatively small alkali charge (14%) within 120 min at170°C. Drainage of pulp was extremely slow. Because of the lowest quality of its pulp it is not suitable for fine paper making. However there is scope for further research to completely characterize the banana fibers and facilitate proper applications in natural fiber reinforced composites. REFERENCES: 1. R.W. Hurter, F.A.Riccio, Why CEOS don’t want to hear about nonwoods—or should they? In: TAPPI Proceedings, NA Nonwood Fiber Symposium, Atlanta, GA, SA, 1998, pp. 1–11. 2. J.E. Atchison, J.N. McGovern, History of paper and the importance of nonwood plant fibres. In F. Hamilton & B. Leopold, eds. Paper and papermanufacture, Secondary fibers and non-wood pulping, Atlanta, GA, USA, Tappi Press, 1993. 3. S.R.D. Guha, Kraft papers from banana stem. Indian pulp and paper, 15 (1960) 31 - 315. 4. A.M. Hurter, Utilization of annual plants agricultural residues for the production of pulp and paper, Proc. TAPPI Pulping Conference, 1988, pp.139. 5. N.A. Darkwa, Pulping characteristics of plantain (MusaParadisiaca L.) pseudostems, Proc. International Non-wood Fiber Pulp and Paper Congress, 1988, pp.973. 6. J.O.V Escolano, C.H. Ballon, The pulping characteristics of some Musa sp. Fibers other than Abaca (Musa Textilisnee.), Proc. International Nonwood Fiber Pulp and Paper Congress , 1988, pp.197.
Since the variation of pulp yield depends mainly on the cellulose yield under different cookingconditions, its impact on Kappa number of the unbleached pulp is plotted in Fig.8. The unbleached pulp Kappa number shows a correlation with the cellulose yield. A higher Kappa number of unbleached pulp is obtained at a higher cellulose yield. 3.3 Bleaching of Banana Stem fiber Soda pulp Before bleaching the pulp was oxygen delignified (High yield pulp was selected). After oxygen delignified the kappa was 19.9. After cooking brightness was 6.56% ISO, after oxygen delignification brightness was 8.42% ISO. Bleaching was done three stages bleaching. The sequence was D0-EP-D1, where pulp was bleached with high bleaching chemical charge, pH was controlled within the specified range and pulp was washed several times with distilled water. Even though high chemical charges used in bleaching but after D0 stage residual ClO2 only 0.064 g/l. Viscosity reduction was within a reasonable figure. The summary of bleaching result is presented in tabulated form (Table 4). Here only the specific results are shown. International Journal of Fiber and Textile Research 2013; 3(1): 31-35
P.T. Franco, Abaca pulp and paper industry in the Philippines, Proceedings of TAPPI Pulping Conference, 1981, pp.133. 8. D.C. Saikia, Wild banana plants (Musa species) as source of fiber for paper andcordage industries, J. Sci. Ind. Res. 56(1997)408. 9. K. Bilba, M. A. Arsene, A. Ouensanga, Bioresource Technology 98(2007) 58. 10. S.O. Heikal, M. H.Fadl, Mild pulping of banana stem, Research and Industry 22(1977)222. 11. S.O Heikal, Nitric acid paper pulps from banana stems, Indian Pulp and Paper 31(1976)5.
12. A. Karolia, S. Malhan, Eco-friendly printing on monor fibre fabrics (Jute and Banana), Asian Textile Journal, 2005, pp. 83-86. 13. A.C. Dutta, The tissue, A Class –Book of botany, Oxford University press, London, 1980, pp. 182-194. 14. P. Ganan, R.Zuluage, J.M. Velez, I. Mondragon, Biological natural retting for determining the hierarchical structure of banana fibers,Mocromol. Biosci. 4 (2004) 978-983. 15. N. Gokarneshan, K.Durairaj, N. Kumar, I. Gupta, Innovation- The key to boost textile business, Textile Magazine, 2009, pp.18-26.
Source of support: Nil; Conflict of interest: None declared
International Journal of Fiber and Textile Research 2013; 3(1): 31-35