Gold and palladium oxidation/complexation in water by a thioamide-iodine leaching systemElectronic supplementary information (ESI) available. See DOI: 10.1039/c7gc01310h

• Main Authors: Isaia, Francesco, Aragoni, Maria Carla, Arca, Massimiliano, Caltagirone, Claudia, Castellano, Carlo, De Filippo, Greta, Garau, Alessandra, Lippolis, Vito, Pivetta, Tiziana
• Format: Article
• Language: English
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c7gc01310h

This paper concerns the oxidative dissolution ability of a thioamide/iodine leaching system in water towards gold, palladium and silver metals in powder in view of a potential application in the recovery process of these metals from electrical and electronic waste equipment (E-waste). The leaching mixture composed of equimolar amounts of thioamide 3-methyl-benzothiazole-2-thione and I 2 in water can oxidize/complex gold and palladium metals in powder in order to form the complexes [Au I (mbtt) 2 ]I 3 and [Pd II (mbtt) 3 I]I 3 . Considering the mild conditions under which the processes were performed ([I 2 ] = 1.14 × 10 −3 M, T = 20 °C, pH = 5.0, leaching time = 24 h), the obtained oxidation yield of Au 0 and Pd 0 are to be considered satisfactory with values of 65% and 69%, respectively. No oxidation was observed for the silver powder. The oxidising/complexing properties of the leaching mixture mbtt + I 2 were interpreted considering the formation of the mbtt-I 2 adduct that features, as a consequence of the S-donor to I 2 interaction, a charge separation between the bridging and terminal iodine atoms in the fragment S-I b -I t . The feasibility of recovering gold from the complex [Au I (mbtt) 2 ]I 3 was verified by performing a cementation with magnesium powder. This paper concerns the oxidative dissolution ability of a thioamide/iodine leaching system in water towards gold, palladium and silver metals by using reaction conditions safe for the health and environment.