Microbial recovery of rare earth elements from metallic wastes and scrap

Vavlekas, Dimitrios (2016). Microbial recovery of rare earth elements from metallic wastes and scrap. University of Birmingham. M.Res.

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Abstract

In this thesis the microbial recovery of the rare earth neodymium is being examined using biofilm of the bacterium Serratia sp. N14, which has been used previously for the removal of lanthanide elements from liquid solutions. The mechanism used is via the PhoN phosphatase enzyme of these cells, which releases phosphate from an organic feedstock and metal cations (M2+) existing in the solution precipitate on the bacterial cell as metal phosphate. Neodymium was announced in 2013 to be included in the five most critical rare earth elements (REEs) and among the recycling of REEs, this was less than 1%. Therefore, the need to recover neodymium from liquid metallic wastes and scrap leachates would be a crucial step to recycle such metals.
The first aim of this project was to study the ageing properties of the PhoN of Serratia sp. N14 cells during one year of storage, with respect to total phosphate release (Pi) and neodymium recovery. A simple predictive mathematical model was produced for the evaluation of metal recovery over various months of storage.
The second goal of this project, was to construct an outflow chamber onto existing equipment for a semi-continuous biofilm preparation as an alternative economic production of biofilm, since the normal ‘’in vessel’’ biofilm production, is not readily scalable. The activity of biofilm from this new method was compared with the biofilm produced in the normal chamber reactor after appropriate times of storage.
The final aim was to establish the potential usefulness of the biofilm with respect to its tolerance to low pH values or to high salt concentrations (neutralized aqua regia), since the overall goal is to recover metals from solid scraps, which may have been leached in strong acid. The robustness of the metal accumulating biofilm is discussed with respect to this envisaged application.

Type of Work:

Thesis (Masters by Research > M.Res.)

Award Type:

Masters by Research > M.Res.

Supervisor(s):