Date of Award

12-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Engineering and Earth Science

Committee Chair/Advisor

Dr. Lindsay Shuller-Nickles

Committee Member

Dr. Brian Powell

Committee Member

Dr. Mark Schlautman

Committee Member

Dr. Rachel Getman

Abstract

Overall, the objective of this dissertation was to investigate the degree of sorption for the alkali cations on rutile to ascertain the impact of different cation properties, such as ion size and charge density, on sorption mechanics as well as probe how the ion may alter the surface – aqueous interface. Initial molecular dynamic simulations and batch experiments showed minimal surface sorption for any alkali cation at relatively low concentrations while simultaneously suggesting the enthalpy of deprotonation shifts slightly in the presence of the alkali cations at different ionic strengths. The cations are likely causing small reorientations of the near-surface water structure, resulting in a different enthalpy of deprotonation of the surface sites. Further MD simulations demonstrated the sorption trend is reverse lyotropic with more of the smaller cations near the surface throughout the MD simulations relative to the larger cations. Comparisons of different complexation models of the thermograms from isothermal calorimetry showed some imprecision in the current framework of the most descriptive models. Potential alterations to improve the fit will likely need to focus on the near-surface aqueous description, either through variable capacitance values or careful consideration of the differences in water orientation in the stern layer of different crystal surface planes.

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