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

•A new process enhances lignin removal from the prehydrolysis liquor was proposed.•Laccase treatment was incorporated into the new process.•Laccase treatment can polymerize low Mw lignin.•The concentration of hemicelluloses and acetic acid were largely unaffected. 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 1–4UmL−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.