Rapid Dissolution of Noble Metals in Organic Solvents

The dissolution of elemental noble metals (NMs) such as gold, platinum, palladium, and copper in organic solutions is necessary for their recycling but carries a high environmental burden due to the use of strong acids and toxic reagents. Herein, a new approach is presented for the rapid dissolution of elemental NMs in organic solvents using mixtures of triphenylphosphine dichloride or oxalyl chloride and hydrogen peroxide, forming metal chloride salts directly. Almost quantitative dissolution of metallic Au, Pd, and Cu was observed within minutes at room temperature. For Pt, dissolution by hydrogen peroxide was inhibited but achieved, albeit more slowly, using the chlorinating oxidant alone. After leaching, transfer of Pt(IV) and Pd(II) chloride salts from the organic phase into a 6 M HCl aqueous phase facilitated the separation of Pt(IV) by precipitation using a simple diamide ligand. In contrast, the retention of Au(III) chloridometalate in the organic phase allowed its selective separation from Ni and Cu from a leachate solution obtained from electronic CPUs. This new approach has potential application in the hydrometallurgical leaching and purification of NMs from ores, spent catalysts, and electronic- and nano-wastes.