METHOD FOR REDUCTIVE EXTRACTION OF IRIDIUM, RHODIUM AND/OR RUTHENIUM

The invention relates to a method for reductive extraction of elemental noble metals from an acidic aqueous solution containing noble metal, the method comprising the addition of non-noble metal including zinc and/or tin to the acidic aqueous solution containing noble metal to form a reaction mixture, wherein the dissolved noble metal includes iridium, rhodium and/or ruthenium, wherein the non-noble metal is added in a leaner-than stoichiometric amount, and wherein the pH of the acidic aqueous solution containing noble metal prior to the addition of the non noble metal is in the range of +0.8 to +3.0 and is also kept in this range in the reaction mixture.