Microwave-assisted deep eutectic solvent pretreatment for enhanced dissolution efficiency of high-purity cellulose in N-methylmorpholine-N-oxide

Efficient dissolution of cellulose is a critical initial stage in converting it into high value materials. In this study, we developed a rapid pretreatment method based on microwave-assisted deep eutectic solvent (MW-DES) technology to markedly reduce the dissolution time of dissolving pulp fibers in N -methylmorpholine-N-oxide (NMMO). Specifically, treatment with a ZnCl 2 /H₃PO₄ system under microwave irradiation at 200 W for 4 min effectively disrupted the hydrogen-bond network of cellulose. This treatment increased the specific surface area by 124% and reduced cellulose crystallinity from 64.06% to 44.63%. Owing to the synergistic pretreatment, the complete dissolution time in NMMO decreased to 12 min, a 60% reduction compared to the 30 min required following microwave-water (MW-water) pretreatment, and demonstrated a significant enhancement in dissolution efficiency. This approach provides a novel, sustainable strategy for the efficient pretreatment of dissolving pulp, thereby supporting the industrial production of Lyocell fibers.