Characterization And Optimization Of Soda-anthraquinone Pulping Of Teff Straw For Paper Making Process

The aim of this research was to investigate the important features of teff straw and its utilizationrnin the pulp and paper industry via soda-anthraquinone pulping process. Morphologicalrncharacterization indicated that the average length of teff straw fibers (1230μm), average fibersrnwidth (15.28μm), cell wall thickness (3.83μm), lumen diameter (21.28μm) and acceptablernderived indices of slenderness ratio (80.78), Runkle ratio (0.36), flexibility coefficient (138.7)rnand wall rigidity coefficient (25) which were comparable to the most non-wood plants andrnEucalyptus. The chemical composition of teff straw showed that the cellulose content (39.4%),rnhemicellulose (29.6%), lignin (14%), extractives (7.2%) and ash content (6.78%). It containedrnlower lignin and higher hemicellulose contents than most of non-wood plants which reflectedrnthat teff straw requires mild cooking conditions. For experimental design, Response SurfacernMethodology/Central Composite Design was used to compare the effects of cooking temperaturern(130, 140 and 150℃), cooking time (60, 90, and 120 minutes) and active alkali concentrationrn(10, 15, and 20%) on pulp yield and Kappa number. The results indicated that sodium hydroxidernconcentration had a higher significant influence on both pulp yield and Kappa number followedrnby cooking time and temperature respectively. Greater interaction effects (temperature-time,rntemperature-active alkali concentration and time-alkali concentration) of factors were also seenrnon pulp yield and Kappa number both positively and negatively. Over cooking, extended timernpulping and high active alkali concentration gave the lower pulp yield. The optimization resultsrnof pulping processes gave the optimal operating condition of 13.76% active alkali at 145.13℃rnfor 71.5 minutes and 33.15% pulp yield (based on oven dried teff straw) of 25.85 Kappa number.rnThe paper hand sheets of 60 g/mrn were prepared from the pulps produced at optimum conditionsrnand tested for its mechanical properties that showed breaking length (4294 m), tensile strengthrn(11.6 kN/m), tensile index (42.1 Nm/g), tear index (5.2 mN.mrn2rn/g) and burst index (1.41rnkPa.mrn2rn2rn/g), and porosity (19.5 se/100 air). The results indicated that the tested strength propertiesrnwere acceptable and make teff straw an alternative material for pulp and paper application.

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