The temperature influence on the phase behavior of ionic liquid based aqueous two-phase systems and its extraction efficiency of 2-chlorophenol

Abstract

With the increasing research on the aqueous two-phase systems (ATPS), the ATPS containing ionic liquid (IL) and salt have been widely used in the extraction and purification process. In this work, the partitioning of 2-chlorophenol in novel ATPS composed of n-butylpyridinium trifluoromethanesulfonate and salts (ammonium sulfate, sodium dihydrogen phosphate) is evaluated. Firstly, the cloud point titration method was used to determine the binodal curves data experimentally at four temperatures and atmospheric pressure. And Merchuk equation was used to fit the binodal curves. Then, the gravimetric method was used to initially determine the tie-lines data and the concentration of all the ions in the top and bottom phases were determined by ion chromatography method to study the ion exchange in the ATPS. The reliability of tie-lines was evaluated by Othmer-Tobias and Bancroft equations. Finally, the influence of types of salts and temperature on the phase diagrams were studied carefully. Besides, in order to analyze the application of ATPS in the extraction, the partition coefficient of 2-chlorophenol was calculated at the same total composition while at different temperature. The ATPS formed by n-butylpyridinium trifluoromethanesulfonate, ammonium sulfate, and water at 298.15 K was found to have the maximum amount of partition coefficient and extraction efficiency.