DFT-based study on the molecular interaction of hydrochloric acid with different extractants

Abstract

As an important chemical raw material, hydrochloric acid widely exists in various chemical production processes. After being used in industrial production, an acidic waste solution will be produced, creating a need to recover hydrochloric acid from the waste solution. Solvent extraction is considered to be an efficient and easy-to-operate method. This paper uses DFT theory to study the binding characteristics of different kinds of extractants and hydrochloric acid molecules. The comprehensive analysis of RDG, AIM, and ELF found that hydrogen proton transfer occurs during hydrochloric acid extraction by amine extractants, and HCl is extracted by ionic association. At the same time, alcohols, ketones, esters, and neutral phosphorus-containing species are all bonded with HCl in the form of a hydrogen bond. In addition, by studying the changes of Gibbs free energy before and after the extraction process, it was found that amines had the most potent binding force to HCl. Moreover, the binding force of TEHA to HCl is much smaller than that of other amines, which not only retains the ability to extract HCl but also makes it have excellent stripping performance. Finally, the results of the DFT calculation are verified by experiments.