Leaching roaster calcine leach residues with aqueous solutions of sulfur dioxide and thiocyanate

Guresin, N., Blanco, S. and Dunne, R. (2013). Leaching roaster calcine leach residues with aqueous solutions of sulfur dioxide and thiocyanate. In: Leon Lorenzen, World Gold 2013 Conference: Challenges in Gold Mining. Proceedings. 5th World Gold 2013 Conference, Brisbane, QLD, Australia, (129-136). 26-29 September, 2013.

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Name Description MIMEType Size Downloads
Author Guresin, N.
Blanco, S.
Dunne, R.
Title of paper Leaching roaster calcine leach residues with aqueous solutions of sulfur dioxide and thiocyanate
Conference name 5th World Gold 2013 Conference
Conference location Brisbane, QLD, Australia
Conference dates 26-29 September, 2013
Proceedings title World Gold 2013 Conference: Challenges in Gold Mining. Proceedings
Place of Publication Carlton, VIC, Australia
Publisher AusIMM: Australasian Institute of Mining and Metallurgy
Publication Year 2013
Sub-type Fully published paper
Open Access Status
ISBN 9781921522956
Editor Leon Lorenzen
Start page 129
End page 136
Total pages 8
Collection year 2014
Language eng
Formatted Abstract/Summary
This paper presents the results of research work conducted to assess if aqueous solutions of sulfur dioxide (SO2) can be used to treat roaster calcine leach residues such that recovery of gold in this material can be achieved with subsequent application of the thiocyanate (SCN-) leaching system. The project is mainly aimed at assessing an alternative use for sulfur dioxide gas generated during flotation concentrate roasting. The calcine leach residue sample used in the study contained 2.56 g/ t gold. The reason for this high level of residual gold is thought to be due to gold surface passivation by thin iron oxide films, presence of gold in solid solution with refractory iron oxides and encapsulation of gold in the structure of these iron oxides.

The study was conducted in three stages. The first stage was the characterisation of a sample from a roaster calcine leach residue. The second stage in the project was a set of leaching tests to assess the feasibility of using aqueous solutions of sulfur dioxide to reductively dissolve refractory iron oxide mineral phases contained in the calcine. The final objective was to assess the efficiency of thiocyanate, a gold complexing ligand stable under acidic and oxidative conditions, to extract gold liberated during sulfur dioxide leaching.

The study showed that the reductive sulfur dioxide treatment of the calcine leach residues followed by oxidative thiocyanate leaching to extract gold was not a particularly efficient process as only around 20 per cent gold could be extracted. Leaching the calcine residues by any of these systems separately also extracted the same amount of gold (12- 14 per cent) implying that irrespective of the solution potential, the acidity helps dissolution of gold encapsulating minerals, mostly hematite, but at a very slow rate.

The findings on the topic in the literature and during this study show the requirement for further technical investigations and economical analyses on two cases. The first case is to roast gold concentrates to produce magnetite rather than hematite followed by sulfur dioxide and thiocyanate leaching of magnetite containing calcines. The second case is to apply a magnetic concentration process to conventional roast-cyanidation calcine residues to produce a gold-rich magnetite concentrate that can be further treated with sulfur dioxide followed by thiocyanate leaching.

For both cases, the best evaluation of the sulfur dioxide leach system in extracting residual gold from calcine leach residues will require a detailed economic analysis to find out the balance between the value of the gold recovered and the loss of revenue from acid production. There are a number of roasters that do not produce acid. In these cases, a portion of the unwanted sulfur dioxide gas can be used to recover gold in magnetite containing calcines as an economic incentive.
Q-Index Code E1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Conference Paper
Collections: Official 2014 Collection
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Created: Wed, 30 Apr 2014, 11:53:16 EST by Jon Swabey on behalf of School of Earth Sciences