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dc.contributor.advisorLoeppert, Richard
dc.creatorLafferty, Brandon James
dc.date.accessioned2005-08-29T14:37:11Z
dc.date.available2005-08-29T14:37:11Z
dc.date.created2003-05
dc.date.issued2005-08-29
dc.identifier.urihttp://hdl.handle.net/1969.1/2264
dc.description.abstractArsenic is a toxic element that is widely distributed throughout the earth??s crust as a result of both natural geologic processes and anthropogenic activities. In virtually all environments, methylated forms of arsenic can be found. Because of the widespread distribution and toxicity of arsenic and methyl-arsenic, their adsorption behavior on soil minerals is of great interest. Although considerable attention has been given to the behavior of inorganic arsenic on mineral surfaces, little research has been conducted regarding interactions of the methyl-arsenic forms. The objective of this study was to compare the adsorption and desorption behavior of methylarsonate (MMAsV), methylarsonous acid (MMAsIII), dimethylarsinate (DMAsV), dimethylarsinous acid (DMAsIII), arsenate (iAsV), and arsenite (iAsIII) on iron oxide minerals (goethite and ferrihydrite) by means of adsorption isotherms and adsorption envelopes. Additionally, desorption envelopes were obtained using sulfate and phosphate as competitive ligands. Arsenic was measured by FI-HG-AAS. MMAsV and iAsV were adsorbed in higher amounts than DMAsV on goethite and ferrihydrite at all pH values studied. Although MMAsV and iAsV were adsorbed quantitatively at lower concentrations on goethite and ferrihydrite, as arsenic concentration was increased MMAsV was adsorbed in slightly lower quantities than iAsV. DMAsV was not quantitatively adsorbed at any concentration on goethite or ferrihydrite. MMAsV and iAsV exhibited high adsorption affinities on both goethite and ferrihydrite at pH values below 9 and showed decreasing adsorption above this point (more rapidly for MMAsV). DMAsV was adsorbed only at pH values below 8 on ferrihydrite and below 7 on goethite. MMAsV, iAsV, and DMAsV each exhibited adsorption characteristics suggesting specific adsorption on both goethite and ferrihydrite. Increased methyl substitution resulted in increased ease of arsenic release from the iron oxide surface. MMAsIII and DMAsIII exhibited no evidence for any type of specific adsorption under the conditions studied. Phosphate was a more effective desorbing ion than sulfate, but neither desorbed all arsenic species quantitatively.en
dc.format.extent209607 bytesen
dc.format.mediumelectronicen
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherTexas A&M University
dc.subjectarsenicen
dc.subjectadsorptionen
dc.subjectmethyl arsenicen
dc.subjectMMAen
dc.subjectMMAAen
dc.subjectDMAen
dc.subjectisothermen
dc.subjectdesorptionen
dc.subjectiron oxide,en
dc.titleMethyl arsenic adsorption and desorption behavior on iron oxidesen
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentSoil and Crop Sciencesen
thesis.degree.disciplineSoil Scienceen
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelMastersen
dc.contributor.committeeMemberSenseman, Scott
dc.contributor.committeeMemberKramer, Timothy
dc.type.genreElectronic Thesisen
dc.type.materialtexten
dc.format.digitalOriginborn digitalen


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