Synergistic delignification of corncob with a phenoxyethanol/alkaline hydrogen peroxide biphasic system under mild conditions and mechanistic insights

Abstract

Efficient lignin removal under mild conditions remains a critical challenge for sustainable lignocellulosic biorefineries. Herein, a novel biphasic pretreatment system consisting of phenoxyethanol (EPH) and alkaline hydrogen peroxide (AHP) was developed for lignin separation from corncob. The optimized pretreatment parameters were determined as a temperature of 343 K, a time of 90 min, an AHP concentration of 3%, and an EPH/AHP volume ratio of 5/5, achieving a lignin removal of 85.21% while preserving 91.86% of cellulose and 73.68% of xylan. The EPH/AHP system exhibited a strong synergistic effect, significantly outperforming the individual solvent systems in fractionation efficiency and enzymatic hydrolysis, with glucose and xylose yields reaching 98.61% and 92.88%, respectively. Comprehensive characterization suggested that the pretreatment was associated with disruption of the compact structure of corncob and appeared to enrich carbohydrates on the sample surface. EPH demonstrated good recyclability, maintaining stable performance over six consecutive reuse cycles, with an average recovery yield of 82.43%. Kinetic study confirmed that lignin removal followed pseudo-first-order kinetics, with a remarkably low activation energy of 23.36 kJ·mol−1, explaining the efficient delignification achievable under mild conditions. Density functional theory (DFT) calculations suggested that hydrogen bonding and π−π stacking may play a key role in lignin removal, with a greatly enhanced total binding energy of 71.91 kcal·mol−1, which is consistent with a synergistic delignification effect. This work provides an efficient and green pretreatment strategy for enhancing fermentable sugar production from lignocellulosic biomass under mild conditions.