Graduate Thesis Or Dissertation
 

Chromium (VI) sorption in soils : chemical behavior and solute transport modeling

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/1j92g988r

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  • Chromium spills on soils are causing severe groundwater contamination problems. To increase the performance of cleanup methods, the chemical behavior of chromium in soils and its transport through soils have to be understood. The objectives of this research were to investigate the sorption characteristics of chromium(VI) in soil and to develop a solute transport model that allows the prediction of chromium(VI) movement through soil columns. Of particular interest was the sorption behavior of chromium(VI) in the presence of phosphate, another adsorbing anion. Laboratory experiments were performed using soil samples taken from an area close to a chromium contamination site. Batch experiments were conducted for both chromium(VI) and phosphates to determine sorption parameters. Soil column breakthrough curves for chromium(VI) were determined with and without phosphate present. The batch studies indicated a strong kinetic sorption behavior for both chromium(VI) and phosphate, which was attributed to a physical non-equilibrium transport process. The soil column experiments showed that the chromium(VI) removal rate from soil can be increased when phosphates are introduced into the soil solution during the desorption process. To interpret the results of these experiments, a physical non-equilibrium solute transport model was developed that incorporated competitive sorption. Numerical solutions of the transport equations were obtained by a partially implicit finite difference method. Computer simulations of experimental breakthrough and desorption curves had close agreement with experimental results. This study demonstrated that phosphate addition to the soil solution is a possible way of increasing desorption rates and, consequently, the effectiveness of chromium(VI) removal from contaminated soils.
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