The Effect of Surface Complexation on Quartz and Amorphous Silica Dissolution
Abstract/Contents
- Abstract
- The geochemical process of adsorption facilitates chemical reactions between ions in solution and reactive surfaces at the mineral-fluid interface. Variations in surface disorder (e.g., crystallinity) and porosity can alter the structural properties of a substrate surface and influence both the propensity for adsorption to occur and the rate at which the substrate dissolves. Though crystallinity has been studied extensively as a property of surfaces, the direct effect of crystallinity on adsorption and the formation of surface complexes remains unclear. In addition, the surface complexes that form at the mineral-fluid interface and their unique properties may influence the dissolution of the material. In order to better understand dissolution and the interplay between dissolution and adsorption, careful examination of the types of surface complexes that form must be performed. A tool to understand these interfacial reactions is the construction of sorption isotherms associated with metals adsorbing onto surfaces across a spectrum of properties. Here, we examine the adsorption of cobalt, nickel, copper, zinc, and lead onto quartz, macroporous amorphous silica, and nanoporous amorphous silica surfaces using experimentally produced pH-titrated sorption isotherms. At low pH, we infer that metals form outer-sphere complexes on quartz surfaces and at high pH, metals form inner-sphere complexes. In comparison, only inner-sphere complexation occurs on amorphous silica surfaces. Though the presence of outer-sphere complexes slightly increases the rate at which the material dissolves, the presence of inner-sphere complexes strongly inhibits dissolution through an inferred passivation effect. By examining these variables, we are able to further our understanding of how the structural properties of mineral surfaces alter adsorption and, in turn, dissolution in natural and anthropogenic systems.
Description
| Type of resource | text |
|---|---|
| Date created | March 2018 |
Creators/Contributors
| Author | Zalles, Laura Berding |
|---|---|
| Primary advisor | Maher, Katherine |
| Advisor | Bird, Dennis |
| Degree granting institution | Stanford University, Department of Geological Sciences |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Subject | Geological Sciences |
| Subject | Stanford University |
| Subject | Stanford |
| Subject | Geochemistry |
| Subject | Geology |
| Subject | Dissolution |
| Subject | Silica |
| Subject | Adsorption |
| Subject | Surface complexation |
| Subject | Department of Geological Sciences |
| Genre | Thesis |
Bibliographic information
Access conditions
- Use and reproduction
- User agrees that, where applicable, content will not be used to identify or to otherwise infringe the privacy or confidentiality rights of individuals. Content distributed via the Stanford Digital Repository may be subject to additional license and use restrictions applied by the depositor.
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Preferred citation
- Preferred Citation
- Zalles, Laura. (2018). The Effect of Surface Complexation on Quartz and Amorphous Silica Dissolution. Stanford Digital Repository. Available at: https://purl.stanford.edu/vb383fn6420
Collection
Master's Theses, Doerr School of Sustainability
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- Contact
- laurazalles@gmail.com
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