Ian Wark Research Institute
ARC Special Research Centre
ARC Special Research Centre
Research Area: Mineral engineering, environmental engineering, chemical/biochemical engineering, physical chemistry
Supervisors: Prof
Bill Skinner and Prof
Jonas Addai-Mensah
Description: Refractotory gold ores are known to normally have
the gold finely disseminated in the sulphide minerals and carbonaceous
materials. The gold is not totally liberated even by fine grinding. As a
result, these ores are difficult to treat by milling and direct cyanide
leaching to recover the gold. Consequently, the refractory portion
(sulphides) of such ores are concentrated by froth flotation and
pretreated to make the concentrate amenable to cyanidation. The
preferred pretreatment process is bacterial oxidation using
chemolithotropic bacterial species such as Thiobacillus ferooxidans,
thiooxidans, and Leptospirilium ferooxidans1. These bacteria species
(e.g. Thiobacillus ferooxidans) is an obligate acidophile that respire
aerobically on pyritic or soluble ferrous ions1-4.
After bio-oxidation, the gold bearing solid residue is recovered by a
liquid/solid separation process. The effluent which is acidic and rich
arsenic and sulphur is commonly neutralized using a two stage,
limestone-based (calcium carbonate and lime) process to produce stable
arsenate and sulphate compounds. However, due to high demand for
limestone for lime and cement production, bio-oxidation plants resorted
to the use of substitutes of limestone. This search resulted in the use
of milled seashells which have high calcium carbonate content and are
found along coastal plains as a good candidate. Seashells are, however,
often used as calcium supplement in the poultry and animal feed
production and several other suitable applications. Thus, its use for
bio-oxidation effluent treatment may be considered as a waste of a
valuable resource. It is therefore compelling to find alternative waste
carbonate compounds such as manganese carbonate waste. Manganese
minerals may basically exist as oxide and carbonate compounds. However,
due to the depletion of the oxide feed stocks in manganese ore bodies,
the carbonate is the phase that is in relative abundance. For commercial
exploitation, manganese carbonate ore particles of sizes < 12.0mm are
considered too fine and usually dumped as waste.
Research Aims, Objectives and Approach
The aim of this project therefore is be to investigate the use,
mechanism, kinetics and efficacy of waste manganese carbonate for
neutralising acidic effluent from bio-oxidation process under relevant
conditions. These will involve:
Expected Outcomes
An effective method for treating mine waste with another waste
appropriate for in sulphide mineral mining areas in countries such as
Australia and Ghana.
References
1. R.C. Blake II, E.A. Shute, G.T. Howard, Applied and Environmental
Microbiology, 60 9 3349-3357 (1994).
2. E.B. Lindstrom, E. Guineriusson, O.H. Tuovinen, Crit. Rev.
Biotechnology, 12: 33-155 (1992).
3. K.C. Marshall, In N. Mozes, P.S. Handley and H. J. Busscher, P.G.
Rouxhet (Ed.) Microbial cell surface analysis. VCH Publishers, Inc. New
York. ( 1991)
4. J.C. Bennet, H. Tributch. Bacterial leaching patterns on pyrite
crystal surfaces. J. Bacteriol. 134 310-317 (1978).
Funding: Potential applicants must be highly qualified to win an
appropriate scholarships (e.g. Endeavour, IPRS, UPS and UNISAPA) to
cover living allowance and tuition (where necessary).
