A new compound, α-aminophosphonate derivative containing pyridine ring (PPDE), was designed and synthesized as an extractant for the separation of nickel from metal impurities. Over 94.5% of Ni (II) extraction from sulfuric acid solution was achieved by using PPDE with an equilibrium pH of 4.02. Meanwhile, high separation coefficients of 23.8 for Ni to Co, 84.9 for Ni to Mn, 254.1 for Ni to Ca and 696.7 for Ni to Mg, respectively, were obtained. It was noted that PPDE exhibited an excellent regenerability, and the extraction of Ni with the recycled organic phase ranged from 92.5% to 93.9% during six circulations. The extracted nickel complex was determined as [Ni (PPDE) 2 (DNNSA − ) 2 (H 2 O) 4 ], which was supported by the data obtained from Fourier transform-infrared, UV–Vis and electrospray ionization-mass spectrometry spectra.
The extraction and separation of heavy rare earths (REs) using newly synthesized α-aminophosphonic acid extractant 2-ethylhexyl-3-(2-ethylhexylamino)pentan-3-yl phosphonic acid (HEHAPP, H A ) in n-heptane were investigated from chloride medium. The extraction stoichiometries of lanthanum , gadolinium , yttrium and lutetium are determined to be RE A 3 by the slope analysis method. The favorable separation factors of adjacent heavy REs(Ⅲ), i.e. β Y/Ho , β Er/Y , β Tm/Er , β Yb/Tm and β Lu/Yb , are determined to be 1.87, 1.36, 3.21, 3.22 and 1.93, respectively, when extracted from a binary system at proper condition. The loading capacities of H A for Ho, Er, Yb and Lu increase in the order Ho < Er < Yb < Lu with the values being 0.201, 0.205, 0.216 and 0.229 mol/L, respectively. So H A would be a potential extractant for the separation of heavy REs(Ⅲ). Among inorganic acids such as H 2 SO 4 , HNO 3 and HCl, HCl is tested to be the most effective stripping agent.
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