Synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA

Simultaneous extraction of zinc and cadmium by a mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) and mono-2-ethyl hexyl phosphoric acid (MEHPA), and the synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA have been investigated. It was shown that the extraction of zinc and cadmium by DEHPA and/or MEHPA can be increased by an increase of pH. The results also illustrate that the pH0.5 of zinc, by increase in MEHPA from 0.1 to 8 vol%, did not vary significantly while that of cadmium varies from 0.63 to 2.4. In other words MEHPA prevents selective extraction of zinc from aqueous media containing both zinc and cadmium. Studies on the selective separation parameter βZn/Cd show that it was reduced 50 to 13 times by an increase in MEHPA from 0.1 to 8.0 vol%. In this paper, the effects of DEHPA and MEHPA concentration on co-extraction of zinc and cadmium have been investigated.