Separation and recovery of precious metals from leach liquors of spent electronic wastes by solvent extraction

Abstract

Solvent extraction was employed to recover precious metals (Au (III), Pd (II) and Pt (IV)) from the leach solution of spent electronic wastes containing Cu (II), Cr (III) and Fe (III). First, pure Fe (III) and Au (III) were recovered by simultaneous extraction with Cyanex 923 followed by selective stripping with HC1 and Na2S2O3. Second, Pt (IV), Pd (II) and Cu (II) were extracted by Alamine 336 from the raffinate. After the removal of Cu (II) by stripping with weak HC1, Pd (II) and Pt (IV) were separately stripped by controlling the concentration of thiourea in the mixture with HC1. A process flow sheet for the separation of precious metals was proposed.