Molecular design of mass-separating agents for separation of cyclic ethers and acetonitrile from water

Abstract

The conductor-like screening model for realistic solvation (COSMO-RS) and molecular dynamics simulation were used to evaluate the salting-out capacity of piperazine-containing Good's buffers (GBs) on the removal of 1,4-dioxane, 1,3-dioxolane, and acetonitrile from water. The general formula of piperazine-based GBs is 2-[4-(2-hydroxyethyl)piperazin-1-yl]alkanesulfonic acid, HO − (CH2)2 − N<CH2CH2CH2CH2 > NH+ − (CH2)n − SO3−, (n = 1–10). The buffers with n = 1 to 4 are commercially available, while the buffers with n = 5 to 10 are molecular designed in order to predict their salting-out effects on the organic solvent + water systems. The isobaric vapor-liquid equilibria of the ternary piperazine-based GB + organic solvent + water systems were predicted. The studied organic solvents are miscible with water at any composition under ambient condition and form a minimum boiling azeotropes. It was observed that the piperazine-based GBs are able to shift the azeotropic composition. The activity coefficients of water and organic solvents in presence of piperazine-based GBs were predicted using the COSMO-RS model. The influence of alkyl chain length between the zwitterion end groups on the phase behavior of the ternary systems was evaluated. Piperazine-based GBs have displayed potent mass-separating agents in the recovery of 1,4-dioxane, 1,3-dioxolane, or acetonitrile from water. The hydrogen bonds formation in MSA + organic solvent + water mixture was analyzed using molecular dynamics simulation.