The extraction of Zn(Ⅱ) in aqueous PEG (1550) - (NH_4)_2SO_4 two-phase system using Cl~- ions as extracting agent

摘要

The extraction of Zn(Ⅱ) in an aqueous PEG (1550) - (NH_4)_2SO_4 two-phase system as a function of several experimental parameters was studied. PEG-based aqueous two-phase systems are composed of two immiscible phases: a polymer-rich phase and a salt-rich phase, which can be used for extraction experiments. In the absence of a suitable extracting agent, for the system consisting of a mixture of equal volumes of 40 mass % PEG and 40 mass % (NH_4)_2SO_4 aqueous solutions, Zn(Ⅱ) remained predominantly in the salt-rich phase. Variation of the pH of the salt stock solution did not change very much the extraction efficiency. By adding chloride ions, an enhancement of the Zn(Ⅱ) extraction was observed. The Zn(Ⅱ) extraction efficiency in presence of Cl~- depends on the acidity of the salt stock solution and on the concentration of chloride ions added into the system.