Solvent Extraction of Lanthanoids(III) and Yttrium(III) with N-Alkylcarbonyl-N-(4-chlorophenyl)hydroxylamines

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Abstract We investigated the effect of halogen substitution of N-alkylcarbonyl-N-phenylhydroxylamines on the extraction of lanthanoids(III). A p-chloro substituent of a phenyl group increased the acidity of R-PHAs by 0.3—0.5 pKa units, and a bromo substituent on the α carbon of the acyl group increased it by 1.5 pKa units. In the former substitution, the separation factor for pairs of lanthanoids(III) and yttrium(III) remained unchanged, whereas in the latter the separation factor was considerably reduced. Hence, the chloro substitution at the phenyl group was a good choice for lowering pH values in the extraction of lanthanoids(III). The pH region was suitable for extracting lanthanoids(III) while preventing the formation of their hydroxo complexes.