Determination And Correlation Of Liquid-Liquid Equilibrium Data For The Ternary Dichloromethane+Water+N, N-Dimethylacetamide System

N, N-dimethylacetamide, also known as DMAC. It is widely used as an excellent organic solvent in petroleum processing, organic synthesis and other areas of the industry because of its steady chemical property, fine dissolubility, difficult to hydrolysis, high boiling points and other advantages as well. But now, in practical industrial production, especially in the production process for pharmaceutical intermediates, the wastewater often contains between 10 and 30 mass percent of DMAC. Direct discharge of wastewater with large amounts of DMAC without treatment will cause a negative effect on our environment, but also will lose a part of DMAC inevitably, which may lead to a significant loss of resources. So how to deal with and recycle DMAC in wastewater is extremely essential.The substance of extraction is mass transfer process that happened between two phases, it has a close relationship with the balance between two liquid phases. So we determined the (liquid+liquid) equilibrium (LLE) data of the system dichloromethane+ water+DMAC to obtain the basic data which are required for recovering DMAC in extraction process. In addition, we also studied the influences of salt effect, and determined the LLE data of the system dichloromethane+water+DMAC+NaCl.Based on the experimental requirements, this article has taken the liquid-liquid equilibrium cell made by our group to determine the solubility data of the system dichloromethane+water+N,N-Dimethylacetamide at 298.15K and 308.15K, respectively under atmospheric pressure, then the solubility curves could be carried out. In the meantime, the LLE data with the different salt concentrations were determined and the phase diagrams for the system were drown out. The experimental results show that the enlargement of two-phase region occurred slowly with an increase of salt concentration, it illustrates that adding salt to the system is beneficial to increase the selectivity of solvent. The experimental data were correlated by using Othmer-Tobia equation, and all the linear correlation coefficients were approximate to 1. Meanwhile both NRTL and UNIQUAC models were adopted to correlate the LLE data, then the LLE data were calculated according to the corresponding values of binary interaction parameters. It can be seen that both NRTL and UNIQUAC models give good representation of the LLE data of the system.