Overview

Project Highlights:

  • Gain expertise in novel methods of processing minerals in high ionic strength media.
  • Visit industry to gain insight into current hydrometallurgical mineral processing techniques.
  • Design and build prototype bench-top reactors for processing minerals with optimal space-time yield.

 

Overview

Traditional ore processing is generally carried out using either hydrometallurgy (high cost, low volume, reasonable selectivity) or pyrometallurgy (lower cost, high volume, low selectivity). Both methods require a large energy input and produce large volumes of waste e.g. slags or waste water. This project will seek to use a new type of solvent process which will be more selective, use less energy, and be more environmentally compatible.

Electrocatalytic and electrolytic methods can be used to solubilize metals and metallic compounds from complex matricies. Ionic liquids can also increase the selectivity and efficiency of metal extraction and winning. The main issue is that this approach necessitates a new approach to reactor design. The majority of processes use batch style tanks or heap leaching to extract metals from their ores.

The project will address a diverse group of ore minerals commonly encountered in important hydrothermal deposit types such as epithermal gold and porphyry copper (including the world-class Lepanto deposit of one of our partners). These minerals, and the chemical elements they host, pose both challenges and opportunities for mineral processing operations.

This project will explore the electrochemistry of common sulfosalt minerals in ionic liquids to assess the potential for new environmentally-benign approaches to processing. It will suit a student, either with a degree in mineral processing/applied geology/geochemistry/mineralogy who is keen to develop skills in chemistry, or with a degree in chemistry who is keen to apply their skills in the mineral processing industry.

You will need to design new ionic liquids to selectively extract specific metals from a concentrate and selectively precipitate the base metals enabling efficient recovery of the more strategic elements. The challenge will be to control material flow to optimise both mineral dissolution and metal recovery while using the minimum volume of solvent. You will also carry out techno-economic analysis during the design stage to ensure that it is viable on a practical scale. The Green metrics of the process will be calculated to support the objectives of improving sustainability and decreasing environmental impact.

Ionic liquids change metal reactivity – image shows copper chloride dissolved in 8 different ionic liquids.

Methodology

You will characterise the structure and chemistry of sulphosalt samples, assessing their reactivity in deep eutectic solvents and their reaction products using optical profiling, cyclic voltammetry, UV-vis spectroscopy and electrochemical quartz crystal microbalance. These data will be correlated with the mineralogical information to derive general rules about the behaviour of these minerals. These will then be used to design bulk tests on concentrate samples to assess the efficacy of dissolution and methods of recovery of the components from solution. There will be the opportunity to investigate routes to produce end-products as well as means of safe disposal of waste products (such as converting arsenic to scorodite). Based on results, a pilot scale test will be carried out to demonstrate the possible industrial application of your work. One aim will be to focus on a non-cyanide based method for extracting gold from ores which is an important issue in artisanal mining.

 

Training and Skills

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.

Geological training will include: reflected light microscopy and scanning electron microscopy (SEM) for mineralogical and textural characterisation of sample material, operation of the electron microprobe to determine the chemistry of samples and X-ray diffraction (XRD) to confirm crystal structures. Chemical training will include: electrochemical techniques such as cyclic voltammetry and chronocoulometry, advanced microscopy including SEM and 3D optical profilometry, and spectroscopy to determine speciation in the solid and solution states.

You will have the opportunity to take introductory modules in mineralogy, ore deposit geology, Advanced Analytical Chemistry or Sustainability of Materials to upgrade your knowledge as required. We will also provide training on enterprise and protecting intellectual property.

 

Timeline

Year 1: Training in research techniques. Obtain additional samples (including museum visits) and characterise these mineralogically. Carry out experiments on selected samples to scope out the major controls on dissolution and metal recovery. Publication and presentation at national conference.

Year 2: Visit processing operations to observe current practices, obtain samples and liaise with metallurgical staff. Systematically investigate a range of samples with the aim of being able to predict reactivity across the group and write publication. Bulk testing of concentrates and investigation of recovery. Presentation at international conference.

Year 3: Completion of bulk testing and write publication. Presentation at international conference. Design and implementation of pilot demonstration. Final publication. Write and submit thesis.

Partners and collaboration (including CASE)

Prof Abbott developed deep eutectic solvents and their application to metal processing. He has worked on scale-up and chemical engineering aspects of reactor design through numerous EU and Innovate UK projects. He is a partner on a Marie Curie Training network on ionometallurgy. Prof Jenkin has over 25 years experience in mineralogy and geochemistry and their application to mineral deposits He has pioneered mineral processing with Prof Abbott over the past 5 years.

 

Further Details

Prof Andrew Abbott;

Department of Chemistry, University of Leicester,

LE1 7RH, UK, 0116 252 2087, apa1@le.ac.uk