Pertraction of cadmium and zinc ions using a supported liquid membrane impregnated with different carriers

An experimental study on the removal of Cd2+ and Zn2+ through a supported liquid membrane using a mixture of mono-(2-etylhexyl) ester of phosphoric acid (M2EHPA) and bis-(2-etylhexyl) ester of phosphoric acid (D2EHPA) as carriers is presented. Parameters affecting the Cd2+ and Zn2+ pertraction such as feed concentration, carrier concentration, pH of the stripping phase, and TBP (tributyl phosphate) concentration were analyzed using the Taguchi method. Optimal experimental conditions for Cd2+ and Zn2+ pertraction were obtained using the analysis of variance (ANOVA) after a 6 h separation with the initial feed concentration of 8.9 x 10(-4) mol L-1, carrier concentration of 20 vol. %, TBP concentration of 4 vol. %, and pH of 0.5. Then, under optimum conditions, a comparison of M2EHPA, D2EHPA, and bis-(2,4,4-trimethylpentyl)monothiophosphinic acid (Cyanex 302) was performed. Effective pertraction of Cd2+ and Zn2+ using these carriers was observed in the following order: mixture of M2EHPA and D2EHPA, D2EHPA, Cyanex 302. It was also found that the presence of one metal ion in the feed solution reduces the pertraction rate of the other one.