Extraction of Gold and Silver by Thiourea-Based Reagents

Abstract
The synthesis and properties of some novel solvent extractants that are highly selective for gold and silver in very acidic chloride solutions are described. In this paper we also report on the study of one of these reagents; Dodecyl-thiourea (DTH), which has shown to be a very selective extractant for Au(III) and Ag(I) in the presence of Cu(II) and Fe(III). The extraction of Au and Ag was found to be fast. The Gold-DTH extraction data were explained by the formation of AuCl3.(DTH)3 species while silver forms AgCl.(DTH)2 complex. The extractant has been also tested for practical application by determining the loading and stripping isotherms.