Investigation of the influence of acetate ions on cadmium extraction with D2EHPA

• The effect of acetate ions on cadmium extraction with D2EHPA was investigated.
• Acetate ions present in the aqueous phase improve the extraction efficiency of cadmium.
• Cadmium extraction with D2EHPA is a pH controlled process.
• Acetate does not enter into the metal–extractant organic complex and only acts as a buffering agent.
• Optimum extraction efficiencies were found by using 0.05 to 0.25 M acetate.

In this paper, effect of acetate ions on cadmium solvent extraction with di-2-ethyl hexyl phosphoric acid, D2EHPA, in kerosene as diluent has been investigated. Infrared spectroscopy and slope analysis methods were used to determine metal–organic complex and reaction stoichiometry respectively. Results showed that acetate ions did not participate in the complex formation but acted as a buffering agent. It was found that acetate could greatly improve the extraction yield. Maximum distribution coefficients were observed in the presence of 0.05 to 0.25 M acetate corresponding to the equilibrium pH of 4.14 to 4.70. The mechanism of cadmium extraction from acetate solution can be represented at equilibrium by: Cd2 + + 2(H2A2)org ↔ (CdA2(HA)2)org + 2H+.