Recycling choline chloride-acetic acid deep eutectic solvent for ferulic acid extraction from palm mesocarp fiber

This study investigated the recovery and recycling of a choline chloride–acetic acid deep eutectic solvent (ChCl–AA DES) used to extract ferulic acid from oil palm mesocarp fiber. Ferulic acid was recovered via selective precipitation with ethanol as an antisolvent, while the residual DES was treated and reused for up to five extraction cycles. The performance of recycled DES was evaluated by monitoring ferulic acid yield, solvent properties, and extraction efficiency. Ferulic acid yield from untreated recycled DES declined from 215 ± 11 mg/g to 78 ± 3 mg/g after five cycles. In contrast, DES treated with a second antisolvent showed improved retention of extraction efficiency, with yields decreasing from 215 ± 11 mg/g to 132 ± 3 mg/g over the same period. Supplementing recycled DES with fresh DES in 1:1 ratio did not enhance performance. Although the pH of recycled DES increased slightly across cycles, the change was minimal. A clear difference in viscosity was observed between water-treated recycled DES (≈7.05 mm2 /s) and untreated DES (≈20.95 mm2/s), though no significant changes occurred when the same treatment was applied consistently.Practical Applications: The study’s findings can be applied to develop an efficient solvent recycling system for DES extraction of ferulic acid from palm mesocarp fiber, making the process more cost-effective and environmentally sustainable while adding value to the oil palm.