Separation of Ni and Co by D2EHPA in the Presence of Citrate Ion

Recycling processes for the recovery of metallic content from the electronic wastes are environmentally friendly and economical. This paper reports a method for the recovery and separation of Ni and Co from the sulfate solution by the use of D2EHPA. In this regard, the influence of citrate ion, as a carboxylate ligand, was examined in the separation conditions of Ni and Co via D2EHPA (a poor selective extractant for Ni and Co separation). It was found that the ΔpH_0.5^Ni-Co (the difference between pH values corresponding to 50 pct extraction of metallic ion) increases to 1.5 at the citrate concentration of 0.05 M; this ΔpH_0.5^Ni-Co value is much higher than that obtained in the absence of citrate ion (0.1). Fourier Transform Infrared Spectroscopy (FT-IR) indicated that the citrate ion is co-absorbed during the metallic ions absorption by D2EHPA meaning that the metal–organic complexes contain Co/Ni and citrate ion. Also, the stoichiometric coefficients of the Ni and Co extraction reaction were proposed by applying the slope analysis method.