Separation of Se and Te Minerals

BACKGROUND
Ionic liquids are defined as salts that are liquid at low temperature, typically <100C. These anhydrous liquids are composed of ions and, like high temperature molten salts, are powerful solvents and electrolytes. High ligand concentrations are possible allowing much greater control on metal speciation in solution, whilst recovery from solution can be by electrowinning, cementation, ion exchange or precipitation. These features provide potential for high selectivity in both dissolution and recovery. Recovery can also be engineered to produce different physical properties, such as nanomaterials. A vast range of ionic liquids exist - those pioneered at Leicester are deep eutectic solvents (DES); mixtures of salts such as choline chloride with H-bond donors such as urea or citric acid. DESs have distinct advantages in being environmentally benign, yet chemically stable. Furthermore the components are industry ready, being already produced in large quantities (10-50 kg choline chloride p.a.) at low cost (~2 Euros/kg).

AIMS
The aim of this project will be to investigate the potential for Deep Eutectic Solvent techniques in the processing and purification of Te and Se and the recovery of them from otherwise unrecycled materials. The main aims are to identify DES suitable for the solubilisation and quantitative recovery of Se and Te from a range of media, including natural samples, smelter by-products, and end of life materials. Also it will assess the potential to scale up to industrial scale and characterise the purity and form of the recovered Se and Te from ores. The project will liaise with 5N plus to investigate the production of elemental and compound products with suitable material properties so that they can be directly used in manufacturing streams without further processing. Finally the PhD will determine the nature of any waste materials and effluents in terms of volumes, chemistry (XRF, ICPMS) biodegradability and recyclability.

We have fully engaged with stakeholders and beneficiaries from the outset, and used the catalyst stage to develop relationships with industrial, governmental and NGO partners. They have helped shape the research plan by exchange of knowledge, strategic plans, and problems. Key issues they raised have allowed us to identify knowledge gaps addressed in the Case for Support:
* Identification of potential resources (lack of data & predictive models)
* Low current value requires low cost production
* Lack of rapid analytical capability with the requisite detection limits
* Dependence on energy intensive smelting and refining of base metals as the dominant source of supply
* How to process alternative ores for recovery
* Lack of well understood mass flows in recovery operations, and thus a lack of optimisation
* Their deleterious role in the recovery of gold from ores
Our research covers four areas of impact outside the scientific community:
1 Identification and discovery of alternative sources of Se and Te. Beneficiaries will include BGS, USGS, Geological Survey of Cyprus and Geological Institute of Romania - NATIONAL AGENCIES with the responsibility to advise government on resource statistics and policy and to provide impartial advice to industry, academia and the public. Our research will enable them to provide improved Te and Se resource statistics and more realistic estimates of future supply to manufacturers, qualified by a sound understanding of the feasibility of extraction and processing. PRIVATE SECTOR COMPANIES who will benefit include those who are already mining Se and Te-rich material but with little understanding of the location of these elements in their deposits and how to recover them; and those actively exploring for new deposits that could include Se and/or Te as a co-product. Our partners include Platina, Vale, Glencore, AngloGold Ashanti and Scotgold. Our research will provide: a) data on the occurrence of Te and Se in crustal systems; b) data for companies to perform a cost-benefit analysis for recovery of Te and Se currently mined, and c) process-based predictive models for the efficient discovery of new economic deposits of Te and Se. One of our UK study sites is a SSSI owned by Leicester City Council and managed by Natural England. These PUBLIC SECTOR ORGANISATIONS will benefit through enhanced scientific understanding of the site, helping them promote its value to the general public.
2 Improved analytical and geometallurgical characterisation techniques. Beneficiaries will be PRIVATE SECTOR COMPANIES who are mining Se and/or Te bearing ore, including AngloGold Ashanti, Mandalay Resources, and Glencore, who will use our results to develop geometallurgical models for Se and Te to improve their recovery along with associated metals. Olympus will benefit through becoming a world-leader in the use of portable instruments for Te and Se determination in grade and mill control.
3 Environmentally benign, low-cost extraction techniques. This will benefit PRIVATE SECTOR COMPANIES who process ores, including partners 5NPlus, Mandalay Resources, AngloGold Ashanti and Scotgold. They will gain economic advantage through our research on new low-energy, low-environmental impact, locally-based extraction, demonstrated at pilot plant scale. The WIDER PUBLIC gain through continued access to, and reduced CO2 footprint of, modern technologies.
4 Strategic knowledge of security of supply. Beneficiaries will be GOVERNMENT AGENCIES who advise on resource strategy (BGS, SOPAC and especially through integration with USGS parallel programs), and POLICY MAKERS IN INTERNATIONAL GOVERNMENT planning future clean energy strategies. PRIVATE SECTOR end-users of Se and Te will benefit through improved integration of their supply chain, security of supply confidence, and direct contact with producers. The WIDER PUBLIC gain through development of sustainable environmental technologies to support a low-carbon society.