Title
Steam and hot water prehydrolysis of bamboo and its effect on residual lignin structure and pulping
Authors
M. SARWAR JAHAN M. AZHARUL ISLAM M. MOSTAFIZUR RAHMAN JANNATUN NAYEEM SHAMIM AHMED and M. A. QUAIYYUM

Received November, 13, 2015
Published Volume 51 Issue 5-6 May-June
Keywords bamboo, steam prehydrolysis, hot water prehydrolysis, dissolving pulp, lignin, methoxyl group

Abstract
In this study, steam prehydrolysis (SP) and hot water prehydrolysis (HWP) of bamboo chips were carried out, followed by kraft cooking and bleaching under identical cooking and bleaching conditions. Then the obtained pulp composition and properties were evaluated, specifically, alkali solubility S10 and S18, viscosity and brightness. The pentosan dissolution from bamboo chips was 51.2% for SP and 55.8% for HWP and it was found that, under the applied prehydrolysis conditions, direct delignification also took place, without affecting α-cellulose.The overall unbleached pulp yield after kraft cooking was almost similar, 32.7% for SP and 33.2% for HWP. The purity of the bleached pulp was 94% with degraded cellulose percentages (S10-S18) of 6.0-6.8% and brightness of 84.2%. To reveal prehydrolysis induced changes in the lignin structure by the SP and HWP processes, lignin was isolated by the acidic dioxane method and characterized. The formulae of lignin C9 indicated a significant decrease in the number of methoxyl groups as the HWP was performed. 1H-NMR spectra showed that bamboo lignin had 0.81 and 0.79 guaiacyl and syringyl protons per C9 units, while the corresponding guaiacyl and syringyl protons for SP and HWP lignins were 0.67 and 0.87 and 0.57 and 0.63, respectively.