Rhodium Production
Rhodium Production
Rhodium is concentrated in mother solutions after platinum и palladium separation from hydrochloric solutions appeared after platinum processing or Cu and nickel electrochemical refining. Contaminating metals are extracted by nitration, after which rhodium chloride complexes pass into Na3[Rh(NO2)6], and precipitated by NH4Cl as (NH4)2Na[Rh(NO2)6]. It is dissolved by heating with hydrochloric acid and reduced by formic acid; heating in hydrogen at 1000°C yields rhodium sponge.
Rhodium affinage (refining) is processed by chlorine treatment of rhodium sponge which results into [Rh(NH3)5Cl]Cl2, [Rh(NH3)3Cl3], (NH4)3[Rh(SO3)3], (NH4)3[RhCl6] complexes with further roasting until rhodium sponge appears. Various extraction and ion exchange methods are used in this process. Pure rhodium sponge is smelting in induction furnaces with inert atmosphere.