Five base metals producers – BHP Billiton, Minara Resources, Rio Tinto, Straits Resources and Zinifex – are amongst the Industry Participants in the Parker Centre. Two engineering firms and three industry suppliers involved in the base metals processing sector are also Industry Participants: these companies are Hatch Associates, WorleyParsons, Ciba Speciality Chemicals, Nalco Australia and Outotec.

Australia is endowed with a substantial share of the world’s economic demonstrated mineral resources of base metals, specifically about 37% for nickel, 32% for lead, 20% for cobalt, 18% for zinc and 8.5% for copper (Geoscience Australia 2006). The major base metal minerals present in Australian deposits are sulfides, although there are also significant quantities of silicates, carbonates and hydroxy-oxides in weathered surface deposits. In particular, Australia's nickel laterite deposits represent a major resource.

However, high grade reserves are becoming depleted and new technologies for processing progressively more marginal ores are urgently needed. The challenges faced by the base metals industries include lower grade deposits, increased ore complexity, less accessible deposits and the growing importance of the abundant low-grade resources of chalcopyrite (copper iron sulfide) ores (which are quite refractory or resistant to leaching).

Increasingly, hydrometallurgical processes are being developed to deal with these challenges. Hydrometallurgical processes lend themselves to:
- processing ores in large or small deposits and in remote areas
- processing ores that contain elements or other constituents that make pyrometallurgical process routes unacceptable
- companies developing “mine to metal” operations, even in remote sites
- improving processing performance and reducing the environmental impact of wastes and tailings.

The Centre’s base metals research is undertaken by a group of around 22 full-time equivalent researchers from all four of the Research Participants in the Centre. Chemists, metallurgists, microbiologists, mineralogists, chemical engineers and modellers contribute to the research effort. These researchers have access to a broad range of laboratory and pilot scale equipment and sophisticated instrumentation.

The research projects undertaken for the base metals market include CRC-funded projects, the collaborative industry-sponsored AMIRA P705A "Improved Anode and Cathode Processes in the Electrowinning of Base Metals" project and one-to-one projects with minerals processing companies.

BASE METALS RESEARCH CAPABILITIES

• Quantitative mineralogical analysis for ores and leach residues
• Ore comminution and beneficiation as related to processing
• Pressure leaching (nickel laterite minerals)
• Pressure oxidation (sulfide minerals)
• Reductive leaching (oxide minerals)
• Electrochemical investigations of leaching processes (sulfide minerals)
• Studies of solution properties and solution chemical species (metal sulfate solutions)
• Surface chemistry (chalcopyrite)
• Process chemistry
• Microbiology and bioleaching (sulfide minerals)
• Metal ion separation & concentration using solvent extraction and ion exchange
• Gaseous reduction (metal sulfate solutions)
• Crystallisation (nickel powder)
• Electrowinning of base metals
• Computer modelling of solvent extraction equipment, reactors and processes.

BASE METALS RESEARCH AREAS
The Centre’s research for the base metals market focuses on hydrometallurgical processes for treating nickel laterites and base metal sulfide ores and concentrates. The CRC-funded projects (listed below) span all areas of hydrometallurgy, namely leaching, separation and metal recovery (by reduction). Further details of the specific research in each of these projects can be found by following the link for each project.

Leaching:

• Research in the Electrochemical Investigations of the Leaching of Sulfide Minerals project includes:
  - studying electrochemical behaviour during leaching of selected sulfide minerals
  - developing methods and techniques for low temperature leaching and then applying them to high temperature, high pressure leaching.
  
  
• The Reductive Leaching of Metal Oxides project focuses on:
  - determining the effects of ligands (sulfate, chloride, sulfite and novel ligands) on the reductive leaching of mixed oxides relevant to ilmenite (iron titanium oxide) and laterites
  - developing thermodynamic and kinetic (rate) data and models for mineral dissolution.
  
  
• The Pressure Hydrometallurgy project includes research in the area of leaching aimed at:
  - understanding the leach reaction chemistry occurring in autoclaves
  - reducing nickel/cobalt losses in pressure acid leaching of laterite ores
  - investigating the impact of process water quality on pressure oxidation of copper and nickel sulfides.
  
  
• The research in the Processes for Low-Grade Nickel Ores project covers laterites and sulfides and includes:
  - understanding the effect of ore mineralogy on leach chemistry
  - examining atmospheric acid leach technologies for processing low-grade laterite ores
  - investigating ways of modifying the physical properties of ores to increase pulp density and enhance nickel production from autoclaves
  - examining the benefits of co-processing laterites and sulfides in heaps and autoclaves.
  
  
• The Biooxidation Process Water project focuses on:
  - quantifying and modelling the effects of high salinity, high total dissolved (ionic) solids process water on biooxidation
  - establishing the limitations to adaptation to water quality by the microbes catalysing sulfide mineral oxidation.
  
  
• The work being undertaken in the Biohydrometallurgy of Sulfides project includes:
  - bioleaching of low-grade sulfide ores (nickel, copper)
  - mineralogical characterisation of ores and residues (tailings)
  - prospecting for new native bioleaching bacteria: enriching, isolating, identifying and testing leaching ability.
  
  
• The Bio-Inspired Hydrometallurgy project involves:
  - a scoping study aimed at mimicing or taking inspiration from selected biological processes (eg biological mineral synthesis) to develop a new hydrometallurgical approach to metal extraction.

Separation:

• Research in the Solvent Extraction Chemistry project includes:
  - studying metal-extractant reactions and interactions in synergistic solvent extraction (SSX)
  - developing methods to monitor extractant performance in SSX systems.
  
  
• Work in the Solvent Extraction Technology project involves:
  - developing and testing novel solvent extraction (SX) and synergistic SX systems for metal(s) separation to meet industry needs
  - improving SX equipment such as mixer-settlers and pulsed columns.
  
  
• The Electrostatic Solvent Extraction project focuses on:
  - an alternative to conventional SX that uses electrostatic charge for agitation
  - investigating the fundamentals of electrostatic agitation to disperse small droplets of the aqueous phase into the organic phase
  - examining mass transfer in electrostatically agitated SX
  - designing, constructing and assessing an electrostatic SX contactor.

Metal Recovery (by Reduction of Metal Ions):

• The Pressure Hydrometallurgy project includes research in the area of hydrogen reduction which focuses on:
  - production of nickel metal powder by pressure reduction in an autoclave (using H₂ (hydrogen) as the reductant) of nickel ammoniacal sulfate solutions
  - investigating the factors affecting the number of densifications (the H₂ reduction cycles responsible for size enlargement of the nickel metal particles)
  - studying the effects of additives and impurities on the rates of nickel powder production.
  
  
• The Gaseous Reduction Processes for Metal Ions project involves research on:
  - pressure reduction of copper ions in copper sulfate solutions
  - evaluating the technical feasibility of using natural gas instead of hydrogen as the reductant in pressure reduction of copper.

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

Benefits Arising from Breakthrough Technologies Research

• an improved understanding of heap leach chemistry and microbiology, and insights on a chalcopyrite heap leach “operating window”, which would complement the development of a heap leach model that could assist the copper industry to extend their heap leach capability
• radical breakthroughs in controlling the precipitation of ferrihydrite (an iron oxide precipitate that can causes problems in hydrometallurgical operations) in the zinc and nickel industries: generated through gaining a detailed understanding of the biological processes for ferrihydrite deposition and dissolution.

Benefits Arising from Process Fundamentals Research

new operating strategies and conditions to optimise pressure leaching of sulfide minerals, developed through a better understanding of how selected sulfide minerals dissolve under typical pressure leach conditions a mineralogical tool that uses electrochemical characterisation to identify minerals and can also provide quantitative information novel ambient/moderate temperature selective leaching and separation methods for metal/metal oxide extraction from ilmenite and nickel laterites the potential to improve biooxidation process performance in industry through assessment of the response of chemolithotrophic microorganisms (used for bioleaching) to the presence in the biooxidation process water of specific ions of interest to clients the ability to provide reliable cost-benefit analyses of the effects of process water of varying quality and different treatment options on biooxidation in operating industrial bioleaching plants demonstrated operational strategies for improving the rate and recovery in the heap bioleaching of copper from secondary sulfide ores such as chalcocite native Australian bioleaching bacteria with enhanced copper leaching ability over previously known strains available for evaluation and test work

demonstrated technique for tracking different types of microbes in bioreactors to help manage the right mix of microbes in the microbial community needed for effective bioleaching greater nickel recovery during high pressure acid leaching of nickel laterites through understanding how nickel losses occur during leaching identification of process conditions for copper and nickel sulfide pressure oxidation informed by fundamental understanding of the impacts of process water quality and additives on autoclave reaction chemistry and thus metal extraction process options for low-grade, mineralogically-complex nickel laterites and sulfides that currently cannot be processed economically new analytical methods to understand the chemistry of novel synergistic solvent extraction (SSX) systems developed by the Centre, to demonstrate that a SSX system is chemically robust and to monitor extractant performance in a processing plant novel solvent extraction and synergistic solvent extraction technologies for improved metal separation and recovery that have been tested for selected target applications in industry recommended modifications to the design of solvent extraction equipment (mixer-settlers and pulsed columns) which will increase the separation and purification efficiency of the equipment an alternative solvent extraction contactor that utilises electrostatic dispersion, which leads to high mass transfer of the desired metal ions – without moving parts – and has other advantages over the mixer-settler contactors currently used in industry higher nickel recovery by increasing the number of densifications possible in the production of metallic nickel powders by hydrogen reduction without loss of product quality a preliminary technical and economic evaluation of a pressure reduction process using natural gas as the reductant for copper production as an alternative to electrowinning: if feasible, this process could have major economic benefits for the Australian copper (and possibly also nickel) industry increased skills and knowledge for industry personnel via technology transfer, including AMIRA project review meetings with sponsors, workshops and training courses.

The Centre's base metals researchers work in:
CSIRO Minerals' Base Metals Hydrometallurgy Program
Curtin University's School of Biomedical Sciences
Murdoch University's School of Chemical and Mathematical Sciences
The University of Queensland's Division of Mining & Minerals Processing Engineering

BASE METALS MARKET LEADER: DR DAVE ROBINSON