A Short Review of the Separation of Iridium and Rhodium from Hydrochloric Acid Solutions by Solvent Extraction

Abstract

Iridium and rhodium are among the platinum group metals. The properties, production processes, and aqueous chemistry of both metals are reviewed. The separation of Ir(IV) and Rh(III) from hydrochloric acid solution is dependent on the characteristics of the solvent extraction systems. In most of the extraction conditions, Ir(IV) is selectively extracted over Rh(III) by either amines or neutral extractants. Rh(I) can be selectively extracted over Ir(III) by neutral extractants after Rh(III) is reduced in the presence of a reducing agent. The separation of these two metals using cationic extractants has also been reported. Although selective extraction of one metal over the other is possible, more efficient solvent extraction systems need to be developed.