Title: Predictive solvent extraction: computational and experimental tools for understanding gold and rhodium recovery.

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Chemistry

Abstract

A study using a combination of computational modelling (quantum mechanical calculations and classical molecular dynamics simulations) and experimental methods (reagent synthesis, liquid-liquid extraction tests and a range of analytical techniques, including acid/base, chloride and Karl Fischer titrations, nuclear magnetic resonance spectroscopy, mass spectrometry and extended X-ray absorption fine structure spectroscopy) to define the mode of action of reagents (both from the literature and those currently used industrially) in the recovery of gold and rhodium in hydrometallurgy processes. Elucidating the mode of action of these extractant reagents is key to facilitating the development of new, improved (e.g. more selective, stronger, more sustainable) versions or to improve upon processes using existing reagents. The research programme will investigate spontaneous assembly and anion recognition of the extractants and the metal species (and any additional components, such as water), aiming to determine the structure of the assemblies formed on metal extraction and to understand how this structure allows for the extraction characteristics observed. This work links closely to the "Synthetic Supramolecular Chemistry" research theme, an area of continuing investment by the EPSRC and to the Physical Science Directed Assembly Grand Challenge network. The work also ties closely with the "Manufacturing for the Future" theme, as understanding processes to obtain critical metals from scarce minerals and secondary mining sources, whilst reducing environmental impact, is a pressing issue for global manufacturing companies. The research falls under the general fields of: inorganic chemistry, analytical chemistry, computational modelling, supramolecular chemistry, and sustainable chemistry.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509152/1 01/10/2015 30/09/2020
1651920 Studentship EP/N509152/1 01/09/2015 31/08/2019 Rebecca Nicolson
 
Description We have gained a better understanding of how amido-amine based reagents act in the solvent extraction of rhodium and explained why they are more effective than simple amines.

We have computationally explored possible modifications to the amido-amines, which could potentially change their extraction ability, and have shown that, theoretically, the presence of chelation is key to the extractants effective recovery of Rh and that small structural changes can have a large influence on the favourably of this chelation.

We have developed a new Rh extractant, based on a known Rh precipitant, which is effective for Rh extraction from high HCl concentrations and back-extraction can be achieved using basic aqueous solution. We are in the process of exploring the selectivity of this extractant.

We are in the process of using molecular dynamics computational modelling to develop an understanding of the behaviour of gold solvent extraction reagents.
Exploitation Route These findings could be taken forward by those in the mining/metal recovery industry (including our industrial partner) to help improve existing processes. The information gained on why amido-amine molecules are effective rhodium extractants and the theoretical testing that has shown how structural modifications may change extraction behaviour could be used to inform the design of new reagents which overcome the drawbacks of the existing ones.

Similarly, the results we have obtained so far from the gold extraction modelling could be used to improve gold recovery processes.

The new Rh extracant developed could be used industrially, though this would heavily depend on the implications involved in changing the existing metal-recovery flow-sheet.
Sectors Chemicals,Environment,Other