Lignin removal enhancement from prehydrolysis liquor of kraft-based dissolving pulp production by laccase-induced polymerization

Lignin removal is essential for value-added utilization of hemicelluloses and acetic acid present in the prehydrolysis liquor (PHL) of a kraft-based hardwood dissolving pulp production. In this paper, a novel process concept, consisting of laccase-induced lignin polymerization, followed by filtration/flocculation, was developed to enhance the lignin removal. The results showed that the lignin removal increased from 11% to 46–61% at laccase concentration of 1–4 U mL−1. The GPC results showed that the molecular weight of the lignin from the laccase treated PHL was increased by 160% in comparison with the original one. The subsequent flocculation using singular Poly-DADMAC system or dual polymer system of Poly-DADMAC/CPAM can further remove 10–15% lignin. The concentrations of hemicelluloses and acetic acid were negligibly affected during the laccase treatment, while flocculation caused 12–15% of total sugar loss. Additionally, the process incorporates this new concept into the kraft-based dissolving pulp production process was proposed.