Extraction of copper(II) from hydrochloric acid solution by Cyanex 921

The solvent extraction of copper(II) from hydrochloric acid solution has been investigated using the commercial extractant, Cyanex 921 in kerosene. The effect of hydrochloric acid concentration, extractant concentration, chloride concentration on the extraction of copper has been studied and a model has been developed for the extraction of copper(II) chloride in order to calculate the concentration of Cu2+ in the extracted organic phase. The distribution ratios of Cu(II) were determined for various concentrations of hydrogen ion, chloride ion and Cyanex 921(L) using the model and were in good agreement with the experimental data for the di-solvated species. The proposed complex formed in the organic phase is H2CuCl4.2L. A negative value of ∆H obtained from temperature variation studies show that the extraction process is exothermic. Almost 99.7% copper was recovered from the loaded organic phase using 0.2 M H2SO4 or 0.5 M HCl.

Research Highlights
► Extraction of Cu(II) is quantitative using 0.5 mol/L Cyanex 921 and 5 mol/L HCl.
► Proposed model confirms the formation of di-solvated species, CuCl4.2 L in the organic phase.
► The negative value of enthalpy indicates extraction process is exothermic and negative entropy change confirms the extraction involves the formation of a complex.
► 0.2 mol/L H2SO4 can effectively strip copper from the loaded organic phase.