Battery technology metals underpin almost all modern technology and humankind’s urgently needed transition to a new Green Economy is therefore inexorably linked to their continued procurement from both primary ores and waste. An intrinsic issue, however, is that our current metal mining practices are deeply unsustainable.
Towards a solution:
To shift the current paradigm away from its constraints, the obvious ‘Grand Challenge’ question is: “Can we obtain metals from their host minerals with drastically less energy input and generating little (or even zero) waste?” To meet this end this GeoNetZero PhD project will explore the mechanisms and kinetics of combining a targeted electric field with a solvent to enable the selective leaching of battery technology metals, including Cu, Ni, Zn and Co, from sulfide-bearing geological materials. Our group has recently provided a proof of concept for this process (for the recovery of Cu from a sulfidic ore) , however, research in this area remains in its infancy. This project will build on this preliminary work in order to develop a mechanistic understanding of this new sustainable mining approach. In particular we will target a range of minerals which are known to be conceptually amenable for teaching, however, very little is known with regard to how they will behave when a targeted electric field is superimposed.
Stated link to the overarching theme of the CDT. The Role of Geoscience in the
Energy Transition and the challenge to meet the net zero emission targets:
Electrokinetic in situ leaching is a new Sustainable Mining process which has the potential to enable the extraction of battery metals, such as Cu, Ni, Zn and Co, from the subsurface and surface stockpiles without the need to physically excavate the material. This would enable such metal recovery to occur with less energy requirement and environmental disturbance than conventional practices.
>99% of all metals (by mass) are currently extracted from the subsurface via physical excavation, which requires complete removal of overburden (and associated biological inhabitants), in order to gain access to the target metal, which then invariably also requires removal of the gangue material (often >99% by volume). Several hundred Gt of metalliferous mine waste are produced each year (this is several orders of magnitude greater than the production of municipal solid waste) with commensurate global scale ecological damage. Metal mining also remains amongst the most significant individual contributors to the Climate Emergency via direct CO2 emissions. It is therefore clear that a different approach is required in order to avoid a triple environmental crisis of resource scarcity, mine waste overload and irreversible Climate Change.
Details of mapping/fieldwork locations/data to be used by the project and confirmation of access to key data being secured:
This project will target battery metal bearing minerals which are relevant to the UK (located within both onshore and offshore metal resources) and world-wide. Samples will be procured from industry and pure ‘control’ mineral samples will be purchased from verified suppliers.
The following will be conducted:
1) Sample procurement (Months 0-6): this will involve the undertaking of a targeted literature survey and liaising with industry in order to identify a small selection of minerals which are suitable for electrokinetic in situ leaching (EK-ISL) but also nationally and globally relevant in terms of battery technology metal content (minerals may include: chalcopyrite, pentlandite, erythrite and sphalerite). Samples will undergo comprehensive analytical characterisation using a range of techniques including: QEMSCAN, SEM-EDX, XRD, ICP-MS/OES (follow total acid digestion) and XRF.
2) Small-scale electrokinetic in situ leaching experiments (Months 6-24): this will involve the construction (and optimisation) of small-scale (e.g. 20x20x20cm) electrokinetic in situ leaching reactions cells (building on our published output ) in order to undertake a range of controlled experiments as a function of time, solvent chemistry, electric field intensity, mineral particle size distribution and electrode architecture. Such experiments will use real mineral samples, mixtures of minerals and gangue material, and synthetic comparator systems (i.e. pure quartz sand mixed with mineral-bearing particles) in order to interrogate the fundamental processes, including the differential contributions of electromigration, electro-osmosis and electrophoresis to metal movement. Aqueous samples will be collected in effluent chambers and then analysed using ICPMS/OES in order to understand the efficacy of the leaching process and the physical and chemical composition of the sediment following the cessation of each experiment will be compared with the starting material (using the analytical techniques listed in (1)) in order to understand the selectivity of leaching and prevalence of different flow regimes (plug flow vs preferential flow).
3) Larger-scale electrokinetic in situ leaching experiments (Months 24-36): the most promising application specifications (and associated sample types) with be further interrogated at larger scale (e.g. 50x50x50cm) in order to gain further understanding of scale-dependent processes (such as preferential flow, surface passivation and gangue mineral chemistry phenomena). Full analytical characterisation (using the techniques outlined above) will be conducted.
Visit the GeoNETZero CDT website for information about the partnership or contact the CDT manager, Lorna Morrow, on [Email Address Removed]
GeoNetZero CDT studentships are open to UK and Irish nationals who, if successful in their applications, will receive a full studentship including payment of university tuition fees at the home fees rate.
A limited number of full studentships are also available to international students which are defined as EU (excluding Irish nationals), EEA, Swiss and all other non-UK nationals. For further details please see the GeoNetZero CDT website.
Those not meeting the nationality and residency requirements to be treated as a ‘home’ student may apply for a limited number of full studentships for international students. Although international students are usually charged a higher tuition fee rate than ‘home’ students, those international students offered a GeoNetZero Centre for Doctoral Training full studentship starting in 2022 will only be charged the ‘home’ tuition fee rate (which will be covered by the studentship).
How to apply
Please visit https://www.exeter.ac.uk/study/funding/award/?id=4400 for full details and to submit your application.