es400658f_si_001.pdf (19.1 MB)
Mineralogical Controls on Aluminum and Magnesium in Uranium Mill Tailings: Key Lake, Saskatchewan, Canada
journal contribution
posted on 2013-07-16, 00:00 authored by M. A. Gomez, M. J. Hendry, J. Koshinsky, J. Essilfie-Dughan, S. Paikaray, J. ChenThe mineralogy and evolution of Al and Mg in U mill tailings are
poorly understood. Elemental analyses (ICP-MS) of both solid and aqueous
phases show that precipitation of large masses of secondary Al and
Mg mineral phases occurs throughout the raffinate neutralization process
(pH 1–11) at the Key Lake U mill, Saskatchewan, Canada. Data
from a suite of analytical methods (ICP-MS, EMPA, laboratory- and
synchrotron-based XRD, ATR-IR, Raman, TEM, EDX, ED) and equilibrium
thermodynamic modeling showed that nanoparticle-sized, spongy, porous,
Mg–Al hydrotalcite is the dominant mineralogical control on
Al and Mg in the neutralized raffinate (pH ≥ 6.7). The presence
of this secondary Mg–Al hydrotalcite in mineral samples of
both fresh and 15-year-old tailings indicates that the Mg–Al
hydrotalcite is geochemically stable, even after >16 years in the
oxic tailings body. Data shows an association between the Mg–Al
hydrotalcite and both As and Ni and point to this Mg–Al hydrotalcite
exerting a mineralogical control on the solubility of these contaminants.