Modeling the Solvent Extraction of Cadmium(II) from Aqueous Chloride Solutions by 2-pyridyl Ketoximes: A Coordination Chemistry Approach.

The goal of this work is to model the nature of the chemical species [CdCl ₂ (extractant) ₂ ] that are formed during the solvent (or liquid-liquid) extraction of the toxic cadmium(II) from chloride-containing aqueous media using hydrophobic 2-pyridyl ketoximes as extractants. Our coordination chemistry approach involves the study of the reactions between cadmium(II) chloride dihydrate and phenyl 2-pyridyl ketoxime (phpaoH) in water-containing acetone. The reactions have provided access to complexes [CdCl ₂ (phpaoH) ₂ ]∙H ₂ O ( 1 ∙H ₂ O) and {[CdCl ₂ (phpaoH)]} _n ( 2 ); the solid-state structures of which have been determined by single-crystal X-ray crystallography. In both complexes, phpaoH behaves as an N , N '-bidentate chelating ligand. The complexes have been characterized by solid-state IR and Raman spectra, and by solution ¹ H NMR spectra. The preparation and characterization of 1 ∙H ₂ O provide strong evidence for the existence of the species [CdCl ₂ (extractant) ₂ ] that have been proposed to be formed during the liquid-liquid extraction process of Cd(II), allowing the efficient transfer of the toxic metal ion from the aqueous phase into the organic phase.
Competing Interests: The authors declare no conflict of interest.