An Integrated ionoSolv Process with Ethanol-Free Pulp Washing for Lignocellulosic Biomass Valorisation and High-Purity Cellulose Pulp Production

High Resolution Image Download MS PowerPoint Slide Sustainable and cost-effective lignocellulosic biomass valorisation is essential for the transition from fossil to renewable feedstocks. The ionoSolv process, which employs protic ionic liquids (PILs) to selectively extract hemicellulose and lignin while preserving cellulose, has demonstrated effectiveness across various feedstocks. Nevertheless, current laboratory protocols rely on ethanol for cellulose pulp washing, raising safety and sustainability concerns and failing to accurately represent commercial-scale process dynamics. Herein, we report for the first time an ethanol-free pulp washing strategy based on an additional IL washing step using a low-cost PIL, enabling enhanced cellulose pulp purity. Miscanthus × giganteus was used as a model feedstock, and a statistical design of experiments was applied to optimise washing conditions, including IL concentration, pulp:IL ratio, and temperature. Enhanced lignin removal was achieved, yielding a cellulose pulp with up to 92.7% glucan content and up to 90.5% enzymatic digestibility (7 days, Ctec-3, 50 °C). Eliminating ethanol and increasing solid loading did not affect cellulose structure. Techno-economic analysis indicates a minimum cellulose selling price of ≤0.80 $·kg –1 at ≥10% solid loading. Overall, the proposed ethanol-free pulp washing strategy enhances safety and process simplification while delivering high-purity cellulose for biorefining and advanced material applications.