Atmospheric Soda Pulping of Banana Stem

Abstract

Banana stem is one of the most explored non-wood lignocellulose due to its high cellulose content with small amount of lignin. The conventional pulping processes efficiently remove the lignin, but there is potential to reduce the energy and chemical consumptions due to the low lignin content of banana stem. In this work, soda pulping was carried out for 60-120 minutes using 16-20% w/v alkali charge at boiling temperature of 105°C. The efficiency of lignin removal at low temperature was evaluated using kappa number analysis. The effects of pulping time and alkali charge on pulp properties were investigated using fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Soda pulping using 18% w/v alkali charge at 10 liquid-to-solid ratio for 90 minutes under atmospheric pressure efficiently removed lignin with minimal cellulose degradation. Extended pulping time and concentrated alkali charge would induce cellulose degradation. FTIR analysis verified that alkaline pulping caused depolymerization on both lignin and cellulose. SEM images of banana stem showed ordered structure cellulose fibrils arrangement. Removal of lignin and hemicellulose was observed through smoother surface of the banana pulp. However, TGA analysis suggested that a better thermal stability could be achieved through pulping using 16% w/v alkali charge.