Solvent extraction of gold(III) from hydrochloric acid media by nonionic surfactants

Studies have been conducted on the equilibrium distribution of Au(III) between hydrochloric acid media and chlorinated organic solvents with nonionic surfactants, polyoxyethylene nonyl phenyl ethers (PONPEs). The equilibrium constants were determined on the basis of the stoichiometric relation as: AuCl4- + H+ <(PONPE)over bar> reversible arrow <(HAuCl(4)PONPE)over bar> The extraction efficiencies increased with an increase in ethylene oxide number of the surfactant, whereas for the diluent the order was chloroform < dichloromethane < dichloroethane. The selective extraction of Au(III) to some heavy metals (Pd(II), Pt(IV), Zn(II), Cu(II) and Fe(III)) could be attained satisfactorily, and the back extraction of Au(III) from the loaded solvent was realized by using water as the shipping solution. Successful application of the present extraction system to a gold leach liquor from a printed substrate was demonstrated.