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 × 10−2 mol/L zinc and 0.05 × 10−2 mol/L cadmium from 5.5 M phosphoric acid solution by D2EHPA in kerosene could be represented at equilibrium by Znaq2+ + 1.5(H2A2)org → ZnA2(HA)org + 2Haq+ and Cdaq2+ + 1.25(H2A2)org → CdA2(HA)1/2 org + 2Haq+. The equilibrium constants for the extraction of zinc and cadmium from phosphoric acid solution were found to be 1.28 × 10−2 mol1/2 L−1/2 and 3.50 × 10−4 mol3/4 L−3/4, respectively.