Most of Australia’s gold is produced by leaching of the gold from its ores using an alkaline cyanide solution. The gold is recovered from solution by adsorption onto activated carbon, which is then separated from the leached pulp by screening (this is generally referred to as the carbon-in-pulp (CIP) process). The gold cyanide is then desorbed from the loaded carbon and metallic gold recovered from the resulting high-grade solution by electrowinning. If the ore being treated is mineralogically complex, then a pre-treatment step may be required prior to leaching.

The Parker Centre is supported by gold producers and allied companies. Two of the world’s leading gold mining companies – Barrick Gold and AngloGold Ashanti – are Industry Participants in the Centre. A number of engineering companies and industry suppliers who are involved in the gold industry are also Industry Participants, namely Hatch Associates, WorleyParsons, Ciba Speciality Chemicals, Nalco Australia and Outotec. SME Straits Resources, another Industry Participant, includes a gold mine amongst its operations.

The Parker Centre’s gold research is addressing the following challenges for the gold industry:
- the technological advances required to access resources whose extraction is uneconomic with present technology, such as:
• sub-economic complex and refractory gold ores
• deeply buried paleochannel gold deposits
- improving current plant processes to increase gold recovery through:
• process optimisation
• on-line monitoring and control
- minimising the environmental impact of gold processing via:
• developing an alternative to cyanide.

The Centre’s 15 full-time equivalent gold researchers are metallurgists, chemists, mineralogists, chemical engineers and process engineers, and are based within three of the four Research Participants in the Centre. A unique range of research equipment and analysis techniques are available to these researchers for fundamental and applied studies. Their research includes CRC-funded projects; the AMIRA P420C "Gold Processing Technology" project (sponsored by 14 companies) and one-to-one projects with Centre Industry Participants and other companies associated with the gold industry.

GOLD RESEARCH CAPABILITIES

• Mineralogical ore characterisation
• Gravity gold recovery
• Carbon fouling
• Cyanide measurement and management
• Process optimisation
• Processing of complex ores, especially copper-gold ores
• Treatment of refractory ores/concentrates
• Assessment of, and treatment options for, preg-robbing ores
• Alternatives to cyanide, particularly thiosulfate
• Deportment/minimisation of environmental contaminants
• Computer modelling and flowsheeting.

GOLD RESEARCH AREAS
The work undertaken by Centre researchers for the gold industry includes CRC-funded projects covering optimisation of the cyanidation process currently used by the industry, alternatives to cyanide for gold leaching, processing of complex and refractory ores and environmental issues related to gold processing (follow the links below for further details of the specific research in each project).

Cyanidation Process Optimisation:

• Research in the Carbon Management project includes:
  - the adsorption of frothers, copper and other foulants onto activated carbon
  - the impact of organic and inorganic foulants on gold adsorption by carbon
  - determining frother deportment (location) around an entire operating circuit
  - the impact of contactor design and agitation energy on gold and foulant adsorption
  - developing a universal method for measuring carbon activity.
  
  
• Work on flowsheeting and modelling/simulation of gold recovery processes is being undertaken in the Flowsheeting and Process Modelling project and the Modelling/Simulation of Gold Recovery Processes project, and includes:
  - incorporating copper leaching and copper cyanide solution chemistry and adsorption by carbon into a gold processing flowsheet
  - economic and environmental optimisation of gold processing circuits
  - predictive water chemistry and water balance modelling to assess water management options.
  - expanding the capability of the SIMCIL computer simulation for modelling cyanide leaching/carbon adsorption to include:
  • preg-robbing factors
  • multi-element systems (gold, copper and silver)
  • heap leaching
  • an improved diagnostic option
  - extending the model that simulates gravity gold recovery to include:
  • gravity devices other than Knelson concentrators (eg Falcon concentrators, the Kelsey jig, the Gekko Inline Pressure Jig)
  • the flash flotation behaviour of gravity recoverable gold.

Alternatives to Cyanide:

• The Non-Cyanide Leaching and Recovery of Gold project involves:
  - investigating thiosulfate leaching for in situ and heap leaching of gold
  - examining different oxidant systems for thiosulfate leaching
  - investigating pre-treatments of “difficult to leach with cyanide” gold ores that may enhance thiosulfate leaching of these ores
  - developing a new elution system for stripping gold thiosulfate from resins.

Complex & Refractory Ores:

• The Improving the Treatment of Preg-Robbing Ores project includes:
  - investigating links between ore mineralogy and gold cyanide adsorption chemistry
  - using Raman spectroscopy to characterise carbonaceous preg-robbing ores
  - evaluating existing and new potential treatment options for preg-robbing ores.
  
  
• Research on processing copper-gold ores is being undertaken in the Processing Complex Ores project and the Processing Copper-Gold Ores project, and includes:
  - developing methods for treating gold ores with a range of copper concentrations, achieved through:
  • different flowsheets depending on copper concentration
  • understanding the mineralogy of copper-gold ores
  • generating novel flowsheets
  - developing innovative ways of treating sulfide concentrates with cyanide
  - reagent measurement and control in the processing of complex ores.

Environmental:

• Work on the environmental aspects of the Processing Complex Ores project focuses on:
  - recovery of metallic copper and cyanide for recycling following cyanide leaching of high copper ores/concentrates
  - copper recovery by adsorption on ion exchange resins, elution and electrowinning.
  
  
• The Trace Elements in Gold Process Solutions project

The Centre also undertakes a wide range of other projects with companies involved in the gold industry, many of which are confidential projects.

INDUSTRY BENEFITS
The potential benefits to the minerals industry of the Centre’s gold research include:

The Parker Centre's gold researchers are based within:
CSIRO Minerals Gold Group
The Murdoch Gold Technology Group
Murdoch University Engineering
Process Mineralogy, WA School of Mines.
Curtin University's Department of Chemical Engineering

GOLD MARKET LEADER: DR MATTHEW JEFFREY