Tell us about your PhD project

I am investigating the stability and degradation of metatorbernite-type minerals. Basically, making radioactive crystals, subjecting them to extreme conditions, and working out how/ why they break down.

Metatorbernite-type minerals are currently being investigated for their potential use in uranium remediation. This group of minerals are able to ‘trap’ uranium in a crystalline form, immobilizing it and so preventing U-contamination from spreading (from e.g. uranium mine tailings or radiochemical spills). Fully understanding stability is therefore essential for retention – we need to know how to prevent the rerelease of uranium into the environment.

Metatorbernite (Cu(UO₂)2(PO₄)₂∙8H₂O), and its arsenate analogue metazeunerite (Cu(UO₂)2(AsO₄)2∙8H₂O) can exist as a solid solution. The stability of the solid solution depends on the relative proportion of P: As, with the As-rich phases generally being less stable. I am trying to determine the reason for this composition-based stability. To do this I am using x-ray diffraction and neutron diffraction studies to look for subtle differences in crystal structure.

There is also a lot we do not yet know about the stability of metatorbernite and metazeunerite. By synthesising these minerals in the lab, I can and test the stability of the pure phases under extreme conditions (e.g. high pressure).

Which element is key to your research area and why?

Uranium. Uranium is one of the fundamental constituents of metatorbernite-type minerals, and the reason we want to investigate them! If we understand the conditions needed to keep these minerals stable, then we can ensure that uranium will remain ‘trapped’ within the crystal lattice.

Describe your average day of PhD work here in the School of Chemistry

Currently I am doing a lot of synthesis work, refining x-ray diffraction data, and drinking a lot of coffee.

What’s your favourite chemical element?

Uranium, of course.

What's your favourite chemical reaction?

A reaction described by Dzik et al. (2017) that I use to synthesise single crystals. It’s an unusual set up. Two separate solutions (uranyl nitrate hexahydrate and phosphoric/ arsenic acid) slowly diffuse through a third solution (copper(II) nitrate trihydrate), eventually reacting to form single crystals of metatorbernite or metazeunerite. However, the former two solutions must be initially separate from - yet submerged in - the third solution. How do you submerge two beakers of solution within a third solution without them instantly mixing? The answer was stolen from the art of cocktail making. By slowly pouring the copper nitrate down a glass rod, turbulence is minimised, and the solutions can remain stratified - like a tequila sunrise.