Title page for ETD etd-12302002-002411

Type of Document Master's Thesis
Author Luxton, Todd Peter
Author's Email Address tluxton@vt.edu
URN etd-12302002-002411
Title Competitive Adsorption of Arsenite and Silicic Acid on Goethite
Degree Master of Science
Department Crop and Soil Environmental Sciences
Advisory Committee
Advisor Name Title
Eick, Matthew J. Committee Chair
Daniels, Walter Lee Committee Member
Tadanier, Christopher J. Committee Member
Zelazny, Lucian W. Committee Member
  • surface complexation modeling
  • arsenic
  • silicic acid
  • CD-MUSIC model
  • competitive adsorption
  • Fe-hydroxide
  • silica
  • arsenite
  • goethite
Date of Defense 2002-12-12
Availability unrestricted
The adsorption behavior of silicic acid and arsenite alone and competitively on goethite over a broad pH range (3-11) at environmentally relevant concentrations was investigated utilizing pH adsorption data and zeta potential measurements. Both addition scenarios (Si before As(III) and As(III) before Si) were examined. The results of the adsorption experiments and zeta potential measurements were then used to model the single ion and competitive ion adsorption on goethite with the CD-MUSIC model implemented in the FITEQL 4.0 computer program. Silicic acid adsorption was reduced by the presence of arsenite for all but one of the adsorption scenarios examined, while in contrast silicic acid had little effect upon arsenite adsorption. However, the presence of silicic acid, regardless of the addition scenario, dramatically increased the arsenite equilibrium solution concentration over the entire pH range investigated. The CD-MUSIC model was able to predict the single ion adsorption behavior of silicic acid and arsenite on goethite. The modeled zeta potential data provided further evidence of the CD-MUSIC model's ability to describe the single anion adsorption on goethite. Our model was also able to collectively describe adsorption and zeta potential data for the low Si-arsenite adsorption scenario quite well however, our model under-predicted silicic acid adsorption for the high Si-arsenite competitive scenario.
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