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

Abstract

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.