University of Illinois Urbana-Champaign

On Competitive Adsorption of Oxyanions by Soils (Freundlich Equation, Enthalphy of Adsorption, Selectivity Coefficient, Anion Mixtures, Anion)

Roy, William Robert

This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.

Permalink

https://hdl.handle.net/2142/71619

Description

Title
On Competitive Adsorption of Oxyanions by Soils (Freundlich Equation, Enthalphy of Adsorption, Selectivity Coefficient, Anion Mixtures, Anion)
Author(s)
Roy, William Robert
Issue Date
1985
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Geochemistry
Abstract
  • The adsorption behavior of anionic mixtures (binary-solute combinations of arsenate, molybdate, and phosphate) by three soil samples (Cecil clay, EPA-14, and Catlin silt loam) was investigated using batch equilibrium techniques. The adsorption of arsenate and molybdate by all three soils was significantly reduced by the presence of phosphate, while the adsorption of phosphate was not greatly influenced by either arsenate or molybdate. The adsorption of arsenate by Cecil clay and EPA-14 was reduced in the presence of molybdate, while arsenate did not compete strongly in molybdate adsorption. In contrast, the adsorption of arsenate by Catlin appeared to be independent of molybdate, while the presence of arsenate lowered molybdate adsorption.
  • The usefulness of two multicomponent Freundlich-type isotherm equations to describe the adsorption of arsenate by Cecil clay in the presence of phosphate or molybdate was evaluated. These multicomponent equations were the DiGiano-Baldauf-Frick-Sontheimer Equation and the Sheindorf-Rebhun-Sheintuch (SRS) Equation. Both expressions were found to satisfactorily describe the isotherm data although there was no clear indication of which, if either, was the more accurate.
  • The application of the SRS equation yielded competitive coefficients for each binary-solute system on a concentration basis. These coefficients appeared to be consistent with qualitative observations, and were viewed as single-valued terms that indicated the relative affinity of each soil for a given anion from a binary-solute mixture.
  • These coefficients appeared to have a soil-specific, quasi-thermodynamic basis. Single-solute isotherms at 288(DEGREES), 298(DEGREES), and 308(DEGREES)K were constructed with arsenate, phosphate, and molybdate using all three soils. A Clausius-Clapeyron-type equation was used to estimate isosteric heats of adsorption values (q(,iso)). The adsorption of the three anions were characterized by different q(,iso) values, and were generally in the order of H(,2)PO(,4)('-) > H(,2)AsO(,4)('-) > MoO(,4)('2-). The magnitude of the SRS competitive coefficients derived from binary-solute mixtures were correlated with the ratios of the heats of adsorption of the individual anion-soil systems. Higher coefficients, indicating the preferential adsorption of solute i in a binary-solute mixture containing solutes i and j, tended to be associated with higher ratios of q(,iso) (i) to q(,iso) (j).
Graduation Semester
1985
Type of Resource
text
Permalink
http://hdl.handle.net/2142/71619

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois
Dissertations and Theses - Agronomy