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Additive Surface Complexation Modeling of Uranium(VI) Adsorption onto Quartz-Sand Dominated Sediments
journal contribution
posted on 2014-06-17, 00:00 authored by Wenming Dong, Jiamin WanMany aquifers contaminated
by U(VI)-containing acidic plumes are
composed predominantly of quartz-sand sediments. The F-Area of the
Savannah River Site (SRS) in South Carolina (USA) is an example. To
predict U(VI) mobility and natural attenuation, we conducted U(VI)
adsorption experiments using the F-Area plume sediments and reference
quartz, goethite, and kaolinite. The sediments are composed of ∼96%
quartz-sand and 3–4% fine fractions of kaolinite and goethite.
We developed a new humic acid adsorption method for determining the
relative surface area abundances of goethite and kaolinite in the
fine fractions. This method is expected to be applicable to many other
binary mineral pairs, and allows successful application of the component
additivity (CA) approach based surface complexation modeling (SCM)
at the SRS F-Area and other similar aquifers. Our experimental results
indicate that quartz has stronger U(VI) adsorption ability per unit
surface area than goethite and kaolinite at pH ≤ 4.0. Our modeling
results indicate that the binary (goethite/kaolinite) CA-SCM under-predicts
U(VI) adsorption to the quartz-sand dominated sediments at pH ≤
4.0. The new ternary (quartz/goethite/kaolinite) CA-SCM provides excellent
predictions. The contributions of quartz-sand, kaolinite, and goethite
to U(VI) adsorption and the potential influences of dissolved Al,
Si, and Fe are also discussed.