Extraction of cadmium from dilute solution using supported liquid membrane

The extraction efficiencies of three phosphoric acid derivatives (D2EHPA, PC-88A and Cyanex 272) for Cd in supported liquid membrane (SLM) have been reported. The equilibrium study indicated the release of two moles of H+ ions from the extractant for extraction of one mole of cadmium ion and association of two moles of the extractants in the extracted species in each case. The diffusion constant of Cd-D2EHPA, Cd-PC-88A and Cd-Cyanex 272 complex through the membrane phase was found to be 2.53 × 10−9, 5.435 × 10−9 and 11.22 × 10−9 m2/s, respectively. The effects of various parameters such as flow rate, pH of feed solution, concentration of extractants in membrane phase, concentration of H2SO4 in strip solution and concentration of Cd in feed solution on cadmium flux (JCd) have been investigated. At pH 7.5, the percentage of cadmium extraction was found to be maximum with 600 mol/m3 D2EHPA and PC-88A and 800 mol/m3 Cyanex 272. The extraction of cadmium using the phosphoric acid derivative follows the order D2EHPA > PC-88A > Cyanex 272.