COSMO-RS-Guided Selection of DES for the Delignification of Sugar Cane Bagasse Allowing the Integrated Recovery of Holocellulose and Functionalized Lignin

A major challenge in biomass valorization is achieving selective lignocellulose fractionation under mild and sustainable conditions, enabling the recovery of both holocellulose and lignin. Deep eutectic solvents (DES) offer tunable and greener alternatives to conventional pretreatments. This study aimed to develop a dual-valorization strategy for sugar cane bagasse by combining COSMO-RS-guided DES selection with optimized delignification to simultaneously obtain high-purity holocellulose and functionalized lignin. A total of 47,080 DES combinations were screened, identifying diethylene glycol dimethyl ether:ethanolamine (DGDE:ET), acidified with p-toluenesulfonic acid (PTSA), as the most promising solvent. The performance of the selected DGDE:ET+PTSA system was benchmarked against conventional 3% w v–1 NaOH extraction and ET+PTSA solvents, and the recovered holocellulose and lignin fractions were systematically characterized through compositional, elemental, and spectroscopic analyses to elucidate structural differences and assess fractionation efficiency. Response surface methodology enabled optimization under mild conditions (DGDE molar fraction 0.10, 100 °C, 0.03 mol L–1 PTSA, 90 min, S/L = 1:10), yielding holocellulose-rich solids containing up to 88.9 ± 2.6% holocellulose for derinded bagasse (SGB), comparable to or better than alkaline pretreatment at less corrosive conditions. The DES was also effective for rind-containing bagasse (SGB-C). Lignin recovered from DES extracts exhibited O/N/S functionalization and achieved complete removal of 2,4-dichlorophenoxyacetic acid at near-neutral pH, outperforming Klason lignin, alkaline lignin, holocellulose, bagasse, and biochars. This dual-stream recovery supports an integrated biorefinery pathway that provides high-purity holocellulose for downstream valorization and chemically functionalized lignin for environmental remediation, contributing to more sustainable and circular biomass utilization.