Liquid-liquid extraction of cadmium chloride complexes studied by NMR
Hans Vigeland Lerum, Chemistry.
Cadmium can occur as a contaminant in the process feeds for nickel. Such feeds tend to have very high salinity which makes the speciation and lability of cadmium difficult to predict. To better understand the underlying process in cadmium extraction, NMR was performed on 113Cd. NMR spectroscopy enables characterisation of the distribution of cadmium-chloride complexes in the solution. In addition liquid-liquid extraction was performed using the radionuclide 109Cd to trace the transfer of cadmium between the organic and the aqueous phase. The investigations were performed in solutions having nominal concentrations of chloride ranging from 0.01 m to 5 m. The ionic strength of the solutions was controlled using perchlorate and nitrate. Transfer of cadmium from the aqueous phase to the organic phase was accomplished using Aliquat 336. NMR showed that the chemical shift was significantly affected by the chloride concentration and less affected by the ionic strength of the solution.