Recovery of metals from chloride leach solutions of anode slimes by solvent extraction. Part I: Recovery of gold with Cyanex 272

A separation process was developed to recover Au(III) from the chloride leach solution of anode slime using selective extraction and stripping step. The anode slime contained Ag, Au, Cu, Ni, Sn and Zn. The extraction with Cyanex 272 in kerosene was conducted by varying the HCl concentration of the solution from 0.5 to 9 M. Most of Au(III) and Sn(II) were extracted into Cyanex 272/kerosene phase together with a small amount of Cu(II) and Zn(II). The Au(III) in the loaded Cyanex 272 was selectively stripped over Sn(II) by (NH4)2S2O3. The McCabe-Thiele diagrams for the extraction and stripping were constructed. Extra pure Au(III) solution was recovered from the leach liquor by batch simulation experiments of two stage countercurrent extraction with Cyanex 272 and by one stage stripping with (NH4)2S2O3. The developed process can be applied to recover gold from a hydrochloric acid solution containing Ag(I), Cu(II), Sn(II) and Zn(II).