Quantitative extraction of Rh(iii) using ionic liquids and its simple separation from Pd(ii).

The extraction of Pd(ii) and Rh(iii) from acidic solutions containing between 1 and 8 M HCl towards three ionic liquids, namely [P66614][Cl], [P66614][Br] and [P66614][DCA], based on the trihexyltetradecylphosphonium cation ([P66614]) and chloride, bromide or dicyanamide (DCA) anions, respectively, is reported. Extraction of Pd(ii) is quantitative up to 6 M HCl (D > 3000). A value of 258 for the distribution coefficient of Rh(iii) extracted from 1 M HCl towards [P66614][Br] is also reported. [P66614][Cl] and [P66614][Br] were found to be very efficient at separating these two metals from aqueous solutions containing at least 6 mol L-1 HCl.