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Issue 19, 2017
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Gold and palladium oxidation/complexation in water by a thioamide–iodine leaching system

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Abstract

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 I2 in water can oxidize/complex gold and palladium metals in powder in order to form the complexes [AuI(mbtt)2]I3 and [PdII(mbtt)3I]I3. Considering the mild conditions under which the processes were performed ([I2] = 1.14 × 10−3 M, T = 20 °C, pH = 5.0, leaching time = 24 h), the obtained oxidation yield of Au0 and Pd0 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 + I2 were interpreted considering the formation of the mbtt–I2 adduct that features, as a consequence of the S-donor to I2 interaction, a charge separation between the bridging and terminal iodine atoms in the fragment S–Ib–It. The feasibility of recovering gold from the complex [AuI(mbtt)2]I3 was verified by performing a cementation with magnesium powder.

Graphical abstract: Gold and palladium oxidation/complexation in water by a thioamide–iodine leaching system

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Publication details

The article was received on 02 May 2017, accepted on 11 Aug 2017 and first published on 15 Aug 2017


Article type: Paper
DOI: 10.1039/C7GC01310H
Citation: Green Chem., 2017,19, 4591-4599
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    Gold and palladium oxidation/complexation in water by a thioamide–iodine leaching system

    F. Isaia, M. C. Aragoni, M. Arca, C. Caltagirone, C. Castellano, G. De Filippo, A. Garau, V. Lippolis and T. Pivetta, Green Chem., 2017, 19, 4591
    DOI: 10.1039/C7GC01310H

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