Selective removal of soluble lignin from pre-hydrolysis liquor of bamboo willow dissolving pulp

Abstract

The selective removal of lignin can be a profitable value-added utilization for the pre-hydrolysis liquor (PHL) produced during kraft-based dissolving pulp production. In this work, the soluble lignin was removed from PHL using CaCl2, Al2(SO4)3, cationic polyacrylamide (CPAM), and a CPAM/Al2(SO4)3 dual-system treatment. The results of zeta potential recording revealed that 8.86% of soluble lignin was removed by CaCl2 treatment through charge neutralization and adsorption, and 13.1% soluble lignin was removed by CPAM through charge neutralization and flocculation bridging. The optimal dosages of CaCl2, CPAM, Al2(SO4)3, and CPAM/Al2(SO4)3 dual-system treatments were 2.0 wt%, 30 ppm, 300 ppm, and 60/300 ppm respectively, at which the soluble lignin removals were 8.09%, 9.24%, 18.3%, and 25.0%, respectively. Additionally, the total sugar loss by the CPAM/Al2(SO4)3 dual-system treatment was higher than that by other individual systems; however, the soluble lignin selective removal by the CaCl2 treatment was the highest, at over 80%.