A simple and low‐energy strategy for the separation of water and acetonitrile

Abstract

As acetonitrile is a widely used solvent for the chemical industry, the recovery of acetonitrile from acetonitrile wastewater is significant for both industrial cost reduction and environmental protection. In this article, a simple, low‐energy, and low‐cost strategy is proposed for the effective separation of acetonitrile from high‐concentration acetonitrile wastewater. The approach is based on a sequential combination of two steps: salt‐induced phase separation and hydrophobic filtration. The acetonitrile wastewater was first induced to split into two phases by salt, that is, the acetonitrile‐rich phase and the water‐rich phase, then the above two phases were poured into the hydrophobic filter paper funnel for the separation. It was shown that NaCl is a suitable salting‐out reagent, and that hydrophobic filter papers—obtained from modification by butyltrichlorosilane and octyltrichlorosilane were the optimal choice for hydrophobic filtration. The salt‐induced phase separation process is able to increase the volume fraction of acetonitrile in the acetonitrile‐rich phase up to 92%. The acetonitrile‐rich phase can pass through the hydrophobic filter paper, whereas the water‐rich phase was intercepted. The hydrophobic filter paper retained strong hydrophobicity and high acetonitrile‐separating capacity after 3 months storage, or upon immersion in acetonitrile‐water mixtures for 12 h, or applied for 25 consecutive separations.