Uranium (bio) remediation via Ureolysis Induced calcite Precipitation

Uranium contamination of surface and sub-surface aquifers hosted in granitic rocks is a recognised problem. U(VI) is water soluble and readily forms soluble ion pairs with dissolved carbonate ions. Being radioactive, uranium has huge cytotoxic effects on living beings. It is therefore necessary to reduce U(VI) into U(IV), an insoluble species. The carbonyl form of U is highly water soluble and demonstrates bioavailable characteristics. Using microbes or microbial by-products for remediation of uranium & other rare earth elements could be a sustainable, cheap & eco-friendly method. Some sulfate-reducing microbes can facilitate this reduction under anaerobic conditions but the reaction is readily reversible in the presence of oxygen. Hence, reduction of uranium from (VI) to (IV) oxidation state irreversibly is the key to alleviation of uranium from the water bodies. In our study, we have demonstrated co-sequestration of uranium with calcium carbonate by microbially induced calcite precipitation (MICP). MICP ensures the complexation of uranium within the calcite structure, immobilizing U as a precipitate thereby, allowing for in-situ quasi-quantitative removal of U from soluble phases.