Applications of phytase-mediated phosphate biomineralizaton for the remediation of uranium mine tailings

Student thesis: Doctoral Thesis

Abstract

The mining of elements such as copper, gold, rare earths, and uranium is an essential part of modern society, providing the raw materials for a wide range of applications in technology, industry, medicine, and energy supply. However, the extraction of these and other resources may cause harm to human and environmental health through the mobilisation of contaminants, including naturally occurring radionuclides.Phosphate mineral phases have been researched as a method of immobilising contaminants including lead, radium, and uranium as natural analogues demonstrate that these metals can be stably incorporated into phosphate minerals over geological timescales and across varying pH, redox, and chemical conditions. Previous research has indicated that phosphate biominerals (produced via the microbial hydrolysis of organic phosphate compounds) may be more sustainable and more efficient at immobilising contaminants than sourcing phosphate minerals from mined phosphate rock.This PhD has investigated the applications of phytate -€“ a common plant waste product -€“ as a phosphate donor. Experiments have been performed with different microorganisms (Aspergillus niger and Blastobotrys adeninivorans) and purified phytate-degrading enzymes in batch solution and solid matrices to understand the opportunities and challenges associated with using phytate as a precursor for phosphate minerals.Both microorganisms tested were able to grow and hydrolyse phytate at environmentally relevant temperatures, an essential property for in situ remediation strategies, and both were able to use the low cost carbon source starch for growth. Experiments within solid substrates established that phosphate biomineralization occurs readily in the presence of a sandy matrix, but that challenges related to the interactions between phytic acid and mineral phases such as kaolinite need to be addressed when considering more complex solid media.Furthermore, it is established that phosphate phases that are insoluble under acidic conditions are suitable targets for phosphate biomineralization -€“ this is demonstrated for lanthanum and lead phosphate, and hypothesised to also be true for uranium -€“ which makes this process a highly promising method for the treatment of acidic, uranium-contaminated mine wastes.
Date of Award15 Sep 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorRebecca Lunn (Supervisor) & Joanna Renshaw (Supervisor)

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