ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Etching and recovery of gold from aluminum substrate in thiourea solution

Tomáš Jindra, Zdeněk Prokop, and Dalimil Šnita

Materion Czech s.r.o., Václavské náměstí 808/66, 110 00 Prague, Czech Republic

E-mail: tomas.jindra@materion.cz

Abstract: This paper deals with two (main) problems of specific gold etching from parts of industrial equipment (e.g., supporting inserts into chambers for physical or chemical vapor deposition). First part of the paper is focused on selective etching of gold from aluminum substrates. Selectivity of the reaction, i.e. leaving substrates intact, is crucial. For this reason, the environmentally friendly and safe method of etching gold in a thiourea solution was tested. This method, while well described in literature, does not preserve various substrates (e.g., aluminum, stainless steel). The main goal of this part of the paper was to understand the mechanism of the reaction and to improve the reaction selectivity towards the aluminum alloy substrate. Thus, different acidifying agents were tested. Second part of the paper is focused on recovery (reduction) of gold from thiourea solutions. Chemical, electrochemical, and biological reduction were tested for gold recovery.

Keywords: gold – selective etching – thiourea – electrowinning – Spirulina platensis

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-011-0117-z

Chemical Papers 66 (6) 617–620 (2012)