Recycling of deep eutectic solvents with a membrane-based process

Abstract

Deep eutectic solvents (DES) are non-flammable, non-toxic, biodegradable solvents which recycling opportunities are still poorly studied. One of the possible applications of DES includes lignin extraction from lignocellulosic materials. The aim of this work was in examining of feasibility of DES (choline chloride and lactic acid in molar ratio of 1:10) recycling with ultrafiltration process. The difficulty with high viscosity of DES was tackled with addition of 99% ethanol to spent DES. The influence on stability and flux of ultrafiltration was examined analyzing such factors as concentration of ethanol, temperature of filtration, and presence of suspended solids during filtration. Resultingly, most effective concentration was proved to be 60 vol% DES in ethanol. A conclusion has been made that a higher DES concentration should be filtered at higher temperature. Presence of suspended solids during filtration was proved to significantly decrease flux. In addition, membrane resistance to DES and 60% DES in ethanol solution was examined. FTIR analyses did not reveal any signs of membrane degradation. Ultrafiltration process showed the feasibility of the tested membrane for DES recycling.