MOLYBDENUM AND SELENIUM SPECIATION IN URANIUM MINE TAILINGS USING X-RAY ABSORPTION SPECTROSCOPY

摘要

Mined uranium (U) ore often contains relatively high concentrations of elements (other than uranium) that may be deleterious to the environment. These include molybdenum (Mo) and selenium (Se), which are liberated from uranium oxides and associated sulphide minerals during milling processing.?? A critical environmental concern in the U mining industry is the possibility of long-term mobilization of elements such as Mo and Se from tailings deposited in in-pit tailings facilities to regional groundwater systems. In this study, x-ray absorption spectroscopy (XAS) was used to study the molecular speciation of these elements of concern (EOC) in samples from the Deilmann Tailings Management Facility (DTMF) at Key Lake in northern Saskatchewan, Canada. An understanding of Mo and Se speciation will help to characterize their long-term stability and evolution in the mine tailings. Results indicate Mo exists mainly as molybdate (+6 oxidation state) and Se exists mainly as selenite (+4 oxidation state). Linear combination fitting (LCF) analysis of the Mo K-edge XANES spectra on tailings samples using standard reference compounds suggests various proportions of NiMoO4 and CaMoO4 complexes as well as molybdate adsorbed onto ferrihydrite.