Scalable Extraction of High-Purity Hemicellulose from Biomass via Urea-Assisted Tetramethylammonium Hydroxide and Membrane Separation

Efficient fractionation of hemicellulose from lignocellulosic biomass is vital for its valorization. In this study, corncob is first used as a model feedstock due to its well-structured lignocellulosic composition. Through systematic optimization of parameters such as alkali concentration, temperature, reaction time, alkali type, and cosolvent, tetramethylammonium hydroxide (TMAH) is identified as the best choice for isolating hemicellulose with high purity. By further implementing optimized conditions (80 °C for 1 h), a urea-assisted TMAH system (comprising 6 wt% TMAH and 10 wt% urea) achieves a 74.94% extraction yield of high-purity hemicellulose (85.7%) from corncob. The versatility of this system is then confirmed by its ability to dissolve hemicellulose from various biomass sources, including Chinese fir, poplar, and bamboo. Additionally, integrating membrane separation within the TMAH–urea system enables scalable fractionation, significantly cutting down acid consumption and antisolvent use by at least 80%. A 500-fold scale-up maintains a close yield of 70.14%. The solvent system exhibits excellent recyclability, sustaining a yield of 64.74% after three recycling cycles. This research highlights the essential roles of alkaline platforms and membrane technology in the industrial production of high-purity hemicellulose. Graphical A tetramethylammonium hydroxide–urea system efficiently extracts high-purity and high-yield hemicellulose from corncob and diverse biomass sources. Integrated membrane separation enables closed-loop solvent recycling, significantly reducing acid/antisolvent consumption. The process demonstrates robust scalability and maintains high efficiency over multiple solvent cycles, offering a sustainable platform for biorefinery.