Toward Organosolv Biorefineries Based on γ-Valerolactone Recycling via Salting-Out Extraction

This study presents an alternative approach for solvent regeneration in γ-valerolactone (GVL) based organosolv fractionation of lignocellulosic biomass through a two-stage salting-out assisted liquid–liquid extraction (SALLE) mediated by Na2SO4. Cynara cardunculus L. altilis (cardoon) stems were treated via microwave-assisted GVL/water extraction, followed by sequential washing and SALLE steps to separate and quantify cellulose, lignin, and hemicellulose fractions while regenerating GVL and Na2SO4. The regenerated GVL was reused over six consecutive cycles, and its performance was assessed through pulp composition and solvent purity analyses. Results show that SALLE enables consistent GVL regeneration (82%), high-purity cellulose pulps (>90 wt % cellulose), and lignin recovery (about 78%) without significant solvent degradation or undesired solute accumulation. The findings demonstrate that SALLE provides an efficient and reproducible method for GVL recovery, which could be implemented in a GVL-based biorefinery.