The solvent extraction of zinc and cadmium from phosphoric acid solution by di-2-ethyl hexyl phosphoric acid in kerosene diluent

The solvent extraction of zinc and cadmium from phosphoric acid solutions using di-2-ethyl hexyl phosphoric acid, D2EHPA, in treated kerosene as diluent has been investigated. The influence of the following parameters was investigated: the extractant concentration, the organic/aqueous phase ratio and the equilibrium pH. Extraction experiments were carried out to determine the effects of equilibrium pH, O/A phase ratio and D2EHPA concentration and their interactions on the extraction yield of zinc and cadmium by using the factorial design and the Yates algorithm for non-linear regression. Based on the above results and taking into consideration that D2EHPA exists in a dimeric form in kerosene, the extraction of 0.45 x 10(-2) mol/L zinc and 0.05 x 10(-2) mol/L cadmium from 5.5 M phosphoric acid solution by D2EHPA in kerosene could be represented at equilibrium by Zn-aq(2+) + 1.5(H(2)A(2))(org) -> ZnA(2)(HA)(org) + 2H(aq)(2+) and Cd-aq(2+) + 1.25(H(2)A(2))(org) CdA(2)(HA)(1/2 org) + 2H(aq)(+). The equilibrium constants for the extraction of zinc and cadmium from phosphoric acid solution were found to be 1.28 x 10(-2) mol/(1/2) L-1/2 and 3.50 x 10(-4) mol(3/4) L-3/4, respectively. (c) 2006 Elsevier B.V. All rights reserved.