Evaluation of the Interactions Between Palladium(II) and N,N’-Dimethyl-N,N’-di-n-hexyl-thiodiglycolamide in the Presence of Surfactants Using Capillary Electrophoresis

Continuous counter-current foam separation (CCFS) is a method for the recovery of valuable metals with high selectivity. It was developed as an organic solvent-free method, and the interaction of surfactants and metal ions in aqueous solution is a key precondition for the successful recovery. In this study, the interactions between the anionic complex of palladium(II) chloride and N,N’-dimethyl-N,N’-di-n-hexyl-thiodiglycolamide (MHTDA), which is an extraction agent for palladium(II), were investigated by capillary electrophoresis, in the presence of surfactants (sodium dodecyl sulfate (SDS) or polyoxyethylene mono-4-octylphenyl ether (POOPE)). The addition of MHTDA to an electrophoretic media containing SDS, resulted in electropherograms composed of two or three peaks. On the other hand, in the case of an electrophoretic media containing POOPE, the elimination of palladium (II) peak was observed due to MHTDA addition. This behavior suggested that the palladium-MHTDA neutral complex is rapidly captured in the POOPE micelles compared with the SDS micelles, and the use of POOPE is effective for the successful recovery of palladium(II) in CCFS.