Abstract：In polyethylene glycol 2000(PEG)-(NH4)2SO4-extractant(sodium diethyldithiocarbamate, DDC) two-phase aqueous systems, spectroscopic behaviour of complexes of Cu(Ⅱ), La(Ⅲ), U(Ⅵ) and Ce(Ⅳ) with DDC as the extractant in PEG phase and general water phase was investigated. Comparing to DDC spectrophotometry, the new method has the advantage that the maximum wavelength of complex of Cu(Ⅱ) shifts to red wavelength. Extraction mechanism and existing form of complexes of metal ions in PEG phase were studied. Effects of different acidity, quantities of DDC and salt, different surfactant on the extraction efficiency of copper(Ⅱ), lanthanum(Ⅲ), uranium(Ⅵ) and cerium(Ⅳ) were discussed. Experimental results show that Cu(Ⅱ) was almost completely extracted in PEG phase at pH 5-8, U(Ⅵ) was partly extracted at pH 1-11, while La(Ⅲ) and Ce(Ⅳ) were not extracted at pH 3-6 buffer solution. So, extraction separation of Cu(Ⅱ)-La(Ⅲ) and Cu (Ⅱ)-Ce (Ⅳ) was carried out by control ling the solution acidity.
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