Evaluation of different methods for the separation of acetonitrile and water. Liquid-liquid and solid-liquid extraction

To separate azeotropic mixtures efficiently, an entrainer is often required. In addition to extractive or azeotropic distillation, extraction with liquid or solid entraining agents can also be used. The most important task is to select an entrainer with high separation performance, considering the downstream step, i.e. the regeneration of the entrainer. This study aims to separate acetonitrile-water mixtures using liquid-liquid extraction with hydrophilic and hydrophobic DESs and solid-liquid extraction with various solid compounds. Both experimental and thermodynamic modeling approaches were used. Of the hydrophilic DES tested, only three DESs caused phase separation. Sodium chloride showed the best separation performance among the solid entrainers tested. Hydrophobic DESs, especially the one with decanoic acid, proved to be the most suitable liquid entrainers. The impact of feed composition, stage number, and DES reusability on separation performance was investigated. Considering the solvent consumption, multistage extraction is the best performing method for separating acetonitrile and water. Hydrophobic DESs were successfully regenerated by freezing.