Tellurium and Selenium Cycling and Supply

A shift from fossil fuels to low-CO2 technologies will lead to greater consumption of certain essential raw materials. Tellurium (Te) and selenium (Se) are 'E-tech' elements essential in photovoltaic (PV) solar panels. They are rare and mined only in small quantities; their location within the Earth is poorly known; recovering them is technically and economically challenging; and their recovery and recycling has significant environmental impacts. Yet demand is expected to surge and PV film production will consume most Se mined and outstrip Te supply by 2020. Presently, these elements are available only as by-products of Cu and Ni refining and their recovery from these ores is decreasing, leading to a supply risk that could hamper the roll-out of PV.
Meeting future demand requires new approaches, including a change from by-production to targeted processing of Se and Te-rich ores. Our research aims to tackle the security of supply by understanding the processes that govern how and where these elements are concentrated in the Earth's crust; and by enabling their recovery with minimal environmental and economic cost. This will involve >20 industrial partners from explorers, producers, processors, end-users and academia, contributing over £0.5M. Focussed objectives across 6 environments will target key knowledge gaps.
The magmatic environment: Develop methods for accurately measuring Se and Te in minerals and rocks - they typically occur in very low concentrations and research is hampered by the lack of reliable data. Experimentally determine how Te and Se distribute between sulfide liquids and magmas - needed to predict where they occur - and ground-truth these data using well-understood magmatic systems. Assess the recognised, but poorly understood, role of "alkaline" magmas in hydrothermal Te mineralisation.
The hydrothermal environment: Measure preferences of Te and Se for different minerals to predict mineral hosts and design ore process strategies. Model water-rock reaction in "alkaline" magma-related hydrothermal systems to test whether the known association is controlled by water chemistry.
The critical zone environment: Determine the chemical forms and distributions of Te and Se in the weathering environment to understand solubility, mobility and bioavailability. This in turn controls the geochemical halo for exploration and provides a natural analogue for microbiological extraction.
The sedimentary environment: Identify the geological and microbiological controls on the occurrence, mobility and concentration of Se and Te in coal - a possible major repository of Se. Identify the geological and microbiological mechanisms of Se and Te concentration in oxidised and reduced sediments - and evaluate these mechanisms as potential industrial separation processes.
Microbiological processing: Identify efficient Se- and Te-precipitating micro-organisms and optimise conditions for recovery from solution. Assess the potential to bio-recover Se and Te from ores and leachates and design a bioreactor.
Ionic liquid processing: Assess the ability of ionic solvents to dissolve Se and Te ore minerals as a recovery method. Optimise ionic liquid processing and give a pilot-plant demonstration.

This is the first holistic study of the Te and Se cycle through the Earth's crust, integrated with groundbreaking ore-processing research. Our results will be used by industry to: efficiently explore for new Te and Se deposits; adapt processing techniques to recover Te and Se from existing deposits; use new low-energy, low-environmental impact recovery technologies. Our results will be used by national agencies to improve estimates of future Te and Se supplies to end-users, who will benefit from increased confidence in security of supply, and to international government for planning future energy strategies. The public will benefit through unhindered development of sustainable environmental technologies to support a low-CO2 society.

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.