Wet oxidation of activated carbon for enhanced adsorptive removal of lignin from the prehydrolysis liquor of kraft-based dissolving pulp production in an integrated forest biorefinery

Prehydrolysis is a key step for the production of kraft-based dissolving pulp. The pre-hydrolysis liquor mainly contains hemicellulosic components. Lignin can also be released into the pre-hydrolysis liquor, which hinders the purification and utilization of these hemicellulosic components. In this work, wet oxidation of activated carbon with nitric acid was employed to enhance the adsorptive removal of lignin from the pre-hydrolysis liquor. Under mild oxidation conditions (2% nitric acid solution), the oxidization of activated carbon resulted in significant enhancement of lignin removal. Adsorption isotherms showed that the specific surface area and the amount of carboxyl groups were affected by the oxidation treatment. The selective removal of lignin fitted well with the pseudo-second order kinetics model.