Liquid−Liquid Extraction of Low-Concentration Aniline from Aqueous Solutions with Salts

The focus of this work was to concentrate aniline at low concentration from water samples using liquid−liquid extraction with salts. The salts included inorganic solid salts and ionic liquids and were added to the system of water + aniline + MTBE (methyl tert-butyl ether) to intensify the conventional liquid−liquid extraction process. The influence of such factors as extraction time, initial aqueous aniline concentration, phase volume ratio, and extraction temperature on the extraction process was investigated to determine the optimum extraction conditions. It was found that the salting effect of K2CO3 on aniline and water is the highest among all of the salts investigated, whereas the imidazolium-based ionic liquids do not bring about a good extraction efficiency as expected. The complex formation and interaction force of the systems containing salts were determined using FTIR (Fourier transform infrared) spectrometry and density functional theory (DFT). This work also tries to explain the separation mechanism by means of the Hofmeister series and quantum chemistry.