Solvent extraction of cadmium(II) from thiocyanate solutions with methylsobutylketone and trioctylphosphine oxide in hexane

Solvent extractions of cadmium(II) in aqueous sodium thiocyanate solution and 1 mol dm-3 Na(SCN, ClO4) constant ionic media have been studied at 298 K. The extraction with methylisobutylketone(4-methyl-2-pentanone) was poor but that with trioctylphosphine oxide in hexane was effective if the concentration was above 1 x 10-2 mol dm-3. By a chelate extraction method, the stability constants of the thiocyanate complexes were determined and the extraction equilibria with these solvating type extractants were analyzed by using these constants. From a comparison of the results with those of zinc(II), it was concluded that though cadmium(II) complexes are more stable than those of zinc(II), their extractability is much inferior to that of the latter. (author)