Recovery of nickel from electroplating wastewater with a new extractant

Nickel is one of the most important strategic metals. With the depletion of high-grade nickel sulfide ores, electroplating wastewater as a kind of secondary resources, its utilization has great significance in nickel recycling industries. A novel extractant, [(2-ethyl-hexylamino)-pyridin-4-yl-methyl]-phosphonic acid diethyl ester (L) was synthesized and used with D2EHPA (di-2-ethyl-hexyl phosphoric acid) to extract and recover nickel from simulation electroplating wastewater. The optimum conditions were determined by single-stage extraction process, and the extraction efficiency and the selectivity of Ni could be greatly enhanced by synergistic binary mixture of L–D2EHPA system. The coordination mode of Ni-extracted complex was studied through the analysis of Fourier transform infrared spectroscopy. It was cued that Ni ions might be coordinated with the N atom from the pyridine ring of L and the O atom of P=O in D2EHPA. Moreover, hydrogen bonds between the O atom of P=O in D2EHPA and the H atom of water molecules might be formed.