SEPARATION AND RECOVERY OF SOME PLATINUM-GROUP METALS (PGMS) BY MEANSOF SELECTIVE PHOTOCATALYTIC REDUCTION

Selective photoreduction, using the semiconductor TiO2 under UV irradi ation, has been investigated as a possible recovery and/or separation method for the PGM's rhodium, palladium and platinum. The effect of pH value and concentration of the sacrificial reducing agent (ethanol) o n the rate of reduction of Rh(III), Pd(II) and Pt(IV) ions have been d etermined separately for these ions as well as for some mixtures. Cond itions favourable for the reduction and adsorption (or precipitation) on TiO2 have been established. It has been found that already deposite d Pt or Pd metal promotes reduction of Rh(III) ions at a pH value wher e it would not otherwise be reduced. A method for the separation of a mixture comprising Rh(III), Pd(II) and Pt(IV), based on photoreduction and adsorption on the TiO2, is proposed.