The
JEB Tailings Management Facility (TMF) is central to reducing
the environmental impact of the uranium ore processing operation located
at the McClean Lake facility and operated by AREVA Resources Canada
(AREVA). The geochemical controls of this facility are largely designed
around the idea that elements of concern, such as Mo, will be controlled
in the very long term through equilibrium with supporting minerals.
However, these systems are far from equilibrium when the tailings
are first placed in the TMF, and it can take years, decades, or centuries
to reach equilibrium. Therefore, it is necessary to understand how
these reactions evolve toward an equilibrium state to understand the
very long-term behavior of the TMF and to ensure that the elements
of concern will be adequately contained. To this end, the Mo speciation
in a series of samples taken from the JEB TMF during the 2008 sampling
campaign has been analyzed. This analysis was performed using powder
X-ray diffraction (XRD), X-ray fluorescence mapping (μ-XRF),
and X-ray absorption near-edge spectroscopy (XANES). These results
show that only XANES was effective in speciating Mo in the tailings
samples, because it was both element-specific and sensitive enough
to detect the low concentrations of Mo present. These results show
that the predominant Mo-bearing phases present in the TMF are powellite,
ferrimolybdite, and molybdate adsorbed on ferrihydrite.
The geochemical model for Mo mineralization in the JEB Tailings Management Facility (JEB TMF), operated by AREVA Resources Canada at McClean Lake, Saskatchewan, was investigated using X-ray Absorption Near-Edge Spectroscopy (XANES), an elemental-specific technique that is sensitive to low elemental concentrations. Twenty five samples collected during the 2013 sampling campaign from various locations and depths in the TMF were analyzed by XANES. Mo K-edge XANES analysis indicated that the tailings consisted primarily of Mo(6+) species: powellite (CaMoO4), ferrimolybdite (Fe2(MoO4)3·8H2O), and molybdate adsorbed on ferrihydrite (Fe(OH)3 - MoO4). A minor concentration of a Mo(4+) species in the form of molybdenite (MoS2) was also present. Changes in the Mo mineralization over time were inferred by comparing the relative amounts of the Mo species in the tailings to the independently measured aqueous Mo pore water concentration. It was found that ferrimolybdite and molybdate adsorbed on ferrihydrite initially dissolves in the TMF and precipitates as powellite.
Drooling is distressing for patients and their families. Ideally an individual would have easy access to the most efficient treatment with the fewest side effects. More evidence is now available but a lack of consensus on management approach, treatment dose and administration technique still exists. The symptom of drooling is best managed by a multidisciplinary team, starting with a conservative approach and then leading to more invasive procedures as appropriate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.