Abstract

• Betel nut fiber was used to isolate cellulose fiber by four processing steps such as alkali hydrolysis using sodium hydroxide (pulping), bleaching using hydrogen peroxide, acid hydrolysis using sulphuric acid and homogenization. In the pulping of biomass, Central Composite Design of Response Surface Methodology was used to opt imize the yield of cellulose. Three variables such as alkali concentration, alkali volume and cooking time were considered as influencing factors on the yield of holocellulose, alpha cellulose and hemicellulose during alkali pulping process. The maximum yields of holocellulose, alpha cellulose and hemicellulose by % wt were 94.33±0.76, 80.17±1.89, and 13.83±1.75 under the optimum conditions. Cellulose fiber was analysed by thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The XRD results revealed high crystallinity of both the cellulose fiber and cellulose pulp, while the TGA thermograms indicated that the alkali and acid treatment completely removed lignin and hemicelluloses from the betel nut fiber. FTIR results reveal that the peaks in the range between 1200 and 1300 cm-1 were not observed in pulp and cellulose fiber which indicated the removal of hemicelluloses and lignin. SEM microphotograph showed that mercerization and acid hydrolysis lead to fibrillation and breakage of the fiber into smaller pieces which promote the effective surface area available for contact.