Title: Optimisation of efficient auxiliary agents of gold leaching in an alkaline thiourea solution for a finely disseminated gold ore

Authors: Lifeng Li; Zhongsi Zhu; Youcai Liu; Qingquan Lin; Zhihui Li; Jiangang Fu

Addresses: School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China ' School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China ' School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China ' School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China ' School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China ' School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China

Abstract: Thiourea as a kind of green and eco-friendly gold lixiviant, was employed to substitute cyanide in the present study of gold leaching. The investigation was carried out on a finely disseminated gold ore from Hongmiao (Hunan province, China) in alkaline thiourea solution with indispensable stable reagents of Na₂SO₃ and (NaPO₃)₆. The main aim was to seek suitable stable reagents and oxidising agents required in leaching gold. Na₂SO₃ and (NaPO₃)₆ were determined as the best stable reagents and Na₂S₂O₈ was a more appropriate oxidant compared with K₃[Fe(CN)₆] in this study. Meantime, the effects of leaching parameters, i.e., the molar ratio of SO₃²⁻, PO₃⁻, TU and S₂O₈²⁻, pH, mixing time and grinding fineness were examined in detail and the optimum condition was obtained. The experimental results show that the molar ratio of SO₃²⁻, PO₃⁻, TU and S₂O₈²⁻ greatly affected gold leaching extent and thiourea decomposition. No more than 72.6% leaching rate could be reached due to deactivation of elemental sulphur created by thiourea and other negative factors, while lower leaching rate (69.4%) of gold leaching rate was obtained in acidic thiourea media compared with alkaline media.

Keywords: alkaline thiourea; gold leaching; stable reagents; oxidising agents; Na2SO3; sodium sulphite; (NaPO3)6; sodium hexametaphosphate; Na2S2O8; sodium persulphate; hydrometallurgy; optimisation; finely disseminated gold ore; cyanide.

DOI: 10.1504/IJMME.2014.066579

International Journal of Mining and Mineral Engineering, 2014 Vol.5 No.4, pp.315 - 327

Received: 26 Apr 2013
Accepted: 08 Feb 2014
Published online: 26 Dec 2014 *

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