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The optimisation of stope leaching: a laboratory investigation into the extraction of uranium from a low-grade ore

Penman, Kristina Mary 2013. The optimisation of stope leaching: a laboratory investigation into the extraction of uranium from a low-grade ore. MPhil Thesis, Cardiff University.
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Abstract

Nuclear power continues to make an important contribution to energy production in many countries around the world. Uranium mining is the first step in the production cycle of nuclear power. In order to enable low-grade uranium ore bodies to be developed as economically viable resources, low input mining techniques, such as stope leaching, are gaining interest. This thesis presents the results of research undertaken into the optimisation of stope leaching from a lowgrade uranium ore. Stope leaching was simulated in the laboratory by submitting crushed ore samples to successive saturated (flooding) and unsaturated (rest period) cycles. Experiments were carried out over a 52 week period using seven different protocols. The effects of rest period and lixiviant composition on uranium extraction rates were investigated. Rest period was varied by flooding at weekly, twice weekly, 2 weekly and 4 weekly intervals. Four different lixiviants were investigated, tap water, Fe(III) sulfate, a nutrient solution and recycled leachate. Maximum uranium extractions over 52 weeks were: 57.7% for Fe(III) sulfate lixiviant with a 2 week rest period and 57.4% for tap water with a 4 week rest period. The introduction (via the lixiviant) or development (via oxidation of accessory pyrite) of low pH and Fe(III) and sulfate-rich interstitial water is thought to have provided conditions conducive to uranium oxidation and dissolution. The 4 week rest period is considered to have provided sufficient time for microbially assisted pyrite oxidation to develop similar conditions in the interstitial water as were provided by the addition of a Fe(III) sulfate lixiviant. All other protocols lead to less than 35% uranium extraction. Shorter rest periods did not allow time for sufficient pyrite oxidation to occur and the addition of a nutrient solution buffered pH which did not favour uranium dissolution. These findings have significant implications for low-grade uranium recovery by demonstrating that extraction achieved through the use of costly oxidising agents can be attained, in the same time frame, by using tap water and decreasing the number of cycles.

Item Type: Thesis (MPhil)
Status: Unpublished
Schools: Engineering
Subjects: Q Science > QD Chemistry
T Technology > TN Mining engineering. Metallurgy
Uncontrolled Keywords: Uranium, stope, Leaching, Low-grade, Optimisation
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:25
URI: http://orca-mwe.cf.ac.uk/id/eprint/51629

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