Separation of Se and Te Minerals

Lead Research Organisation: University of Leicester
Department Name: Chemistry

Abstract

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.

Publications

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Abbott A (2017) Paint casting: A facile method of studying mineral electrochemistry in Electrochemistry Communications

Studentship Projects

Project Reference Relationship Related To Start End Student Name
NE/M010848/1 01/06/2015 30/11/2019
1646204 Studentship NE/M010848/1 01/10/2015 31/03/2019 Francesca Bevan
 
Description The most significant achievements include the development and quantification of an electrochemical technique to analyse a wide range of selenides and tellurides. Previously the electrochemical analysis of these materials was difficult or in some cases impossible. Through a quick and simple technique, employing the viscosity and conductivity of DESs, in particular Ethaline, the redox potentials of silver, zinc, copper and cadmium tellurides and selenides were analysed. This subsequently led to the successful dissolution of both Te and Se into the Ethaline electrolyte, again using the novel paint casting technique. The solutions could be tested by a selection of spot tests that proved the existence of tellurium and selenium oxide in solution. Finally a scaled up version of a recovery cell was developed for the complete recovery of copper from chalcopyrite. This employed the use of a combination of DESs in order to utilise the appropriate properties from the different solvents. This technique is also due to be applied to a chosen selenide or telluride in order to separate the metal entirely from the Te/Se. If this is not completed by the end of my research, there are a lot of project students at Leicester that will be able to carry on the work.
Exploitation Route There needs to be more development for the electrochemical cell used in the recovery of Se/Te in order to continue extract the pure elements and eventually scaling up and improving the space time yield.
Sectors Energy,Environment

 
Description Generic technology has been developed to extract metals from ores and secondary sources. This aims to extract meals from complex matrices and hopes to remove the use of toxic reagents such as mercury and cyanide from artisanal metal processing. The University of Leicester has signed an agreement to investigate some issues of mineral processing using DESs with a company called ARGO. It aims to develop pilot plant facilities to extract metals using deep eutectic solvents. The project has investigated some of the practical issues associated scale up and has developed new cell designs to improve space-time-yield from the process.
 
Title Paint Casting 
Description A novel way to study the electrochemical behaviour of typically difficult to study materials. Paint casting is a simple technique, whereby a paste of powdered material and a viscous liquid (DES) is painted directly onto the surface of an electrode in order to study its electrochemical behaviour. It allows materials that don't dissolve easily or are not conductive in solution to be studied quickly and easily. 
Type Of Material Improvements to research infrastructure 
Year Produced 2017 
Provided To Others? Yes  
Impact Certain materials, in particular minerals are difficult or sometimes impossible to dissolve in solution, other materials aren't very conductive and therefore can't be made into individual electrodes. The use of this technique allows a lot of the chalcogenides to be studied very easily where previously it would require a laborious technique to be used to study them. 
URL https://www.sciencedirect.com/science/article/pii/S1388248117300024
 
Description STEM for Britain 2018 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact I was chosen, through a competition entry to present a poster on my research to MPs and policy makers.
Year(s) Of Engagement Activity 2018