Interaction of U(VI) with pyrite, galena and their mixtures: a theoretical and multitechnique approach

Pyrite and/or galena particles previously conditioned with U(VI) at pH 6 have been characterized by micro-Raman spectrometry, voltammetry, scanning electron microscopy and high resolution X-ray photoelectron spectroscopy. U3O8 is first formed on the sulphide surfaces via a redox process, then, if an excess of U(VI) remains in solution it is sorbed as UO3 and shoepite. Galvanic phenomena occur when the minerals are in mixture in a medium containing U(VI): galena particles are oxidized whereas U(VI) is reduced at the pyrite particle surface. The maximum amounts of fixed uranium are 0.4 mmol/g for pyrite and 0.1 mmol/g for galena and the 50:50 pyrite:galena mixture.