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This article in SSSAJ

  1. Vol. 64 No. 3, p. 908-917
    Received: Jan 4, 1999

    * Corresponding author(s): barnettm@eng.auburn.edu


Adsorption and Transport of Uranium(VI) in Subsurface Media

  1. M. O. Barnett *a,
  2. P. M. Jardineb,
  3. S. C. Brooksb and
  4. H. M. Selimc
  1. a Dep. of Civil Engineering, 208 Harbert Engineering Center, Auburn Univ., Auburn, AL 36849-5337 USA
    b Environ. Sci. Div., Oak Ridge National Lab., P.O. Box 2008, Oak Ridge, TN 37831-6038 USA
    c Dep. of Agronomy, 104 Sturgis Hall, Louisiana State Univ., Baton Rouge, LA 70803 USA


Uranium(VI) adsorption and transport in three natural, heterogeneous subsurface media were investigated in batch and column experiments. The rate of U(VI) adsorption to the natural samples was rapid over the first few hours of the experiments, and then slowed appreciably after 24 to 48 h. The adsorption of U(VI) to the samples was also nonlinear, suggesting a decreasing attraction for the surface with increased surface loading. The extent of adsorption on each of the media was strongly pH-dependent, increasing sharply as the pH increased from 4.5 to 5.5 and then decreasing sharply over the pH range 7.5 to 8.5 as the concentration of dissolved carbonate and U(VI)–carbonate complexes increased. The similarities in the pH-dependent behavior between the three materials despite differences in bulk mineralogy was likely due to the similar Fe contents of the materials. The transport of U(VI) through packed columns of the soils and sediments was significantly retarded but reversible. The local equilibrium assumption and the batch-measured adsorption isotherms dramatically underestimated the degree of retardation observed in the columns. The U(VI) displacement experiments were modeled with the one-dimensional advective–dispersive equation and several different model formulations describing the interactions of U(VI) with the solid phase. These models were able to fit the observed breakthrough curves within 0.1 root mean square error of the initial concentration.

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