SOLVENT EXTRACTION OF PALLADIUM(II) FROM ALKALINE CYANIDE SOLUTION BY THE DODECYL DIMETHYL-2-PHENOXYETHYL AMMONIUM BROMIDE

The direct extraction of Pd(CN)(4)(2-) from alkaline cyanide solutions with dodecyl dimethyl-2-phenoxyethyl ammonium bromide (DDPB) was investigated. Several factors affecting extraction efficiency, including DDPB concentration, modifier content, equilibrium time, phase ratio (O/A), pH and palladium concentration in aqueous phase, were studied. The results indicated that nearly all of the Pd(II) (>98%) was transferred from the aqueous phase into the organic phase. N-pentanol was the most appropriate modifier for the extraction of Pd(CN)(4)(2-). Palladium can be separated efficiently by DDPB over base metals (Fe, Co, Ni and Cu) from alkaline cyanide medium. The extraction was quite fast and equilibrium could be established within 3 min. Most of Pd(II) (>96%) in the organic phase could be stripped with ammonium thiocyanate aqueous solutions, from which elemental palladium could potentially be recovered by the addition of hydrazine hydrate. The organic phase after stripping can be recycled for a continuous extraction-stripping operation. The extraction mechanism can be deduced based on FTIR spectrum and slope analysis while the mechanism of stripping can be explained by the principle of minimum charge density and Le Chatelier's principle. The proposed method was applied to extract palladium from real cyanide leaching liquor of Pd flotation concentrate with satisfactory results.