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Fundamental Studies of Competitive Equilibria at Silica Surfaces
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Fundamental Studies of Competitive Equilibria at Silica Surfaces. |
| 개인저자 | Stubbs, Barrack Perez. |
| 단체저자명 | Michigan State University. Chemistry - Doctor of Philosophy. |
| 발행사항 | [S.l.]: Michigan State University., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 117 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-06B. Dissertation Abstract International |
| ISBN | 9781392881347 |
| 학위논문주기 | Thesis (Ph.D.)--Michigan State University, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-06, Section: B.
Advisor: Blanchard, Gary. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | The fundamental interactions such as physisorption at solid-liquid interfaces are not fully characterized. The physical properties and chemical reactivity at the silica surface is one that is subject to much investigation. A variety of analytical techniques, including solid state nuclear magnetic resonance (SS-NMR ) and high-performance liquid chromatography (HPLC) were utilized to help characterize the surface of silica. These techniques were combined in order to understand the fundamental mechanisms of surface interactions such as adsorption mechanisms and chemical reactivity. The pH, ionic strength, and mobile phase compositions were varied throughout the experiments as a basis for assessing reactivity.The SS-NMR data shows a correlation between pH and labile surface hydrogens. At higher pH values, the transfer of excitation from labile surface hydrogens to surface silicon atoms is diminished. A change in peak ratios that correspond to labile primary silanols and surface bridging siloxanes was observed. The relative concentration of bridging siloxanes is constant whereas the signal from primary silanols is greatly diminished.Aqueous, normal-phase HPLC shows the various interactions of phenol with the silica surface. Multiple peaks were generated from a single analyte when the water/methanol concentration was at least 20%/80%. At 90% and 100% methanol, a single peak is shown for phenol. The ratio and number of peaks depends on conditions such as solvent composition, pH, ionic strength, flow rate, and temperature. We argue that the distribution of surface silanol sites is responsible for the generation of multiple peaks that are seen in the extreme aqueous conditions. These sites, as well as the water in the mobile phase, modify the mass transport term in the Van Deemter equation. The conditions and results obtained in these experiments are explained below with an emphasis on mass transport.Additionally, other analytical techniques such as scanning electron microscopy, thermogravimetric analysis, and inductively coupled plasma were used to help characterize the silica surface. Through these techniques, values for surface silanol concentration ranging from 1.6關mol/m2 to 7.0關mol/m2 were obtained. The physical morphology of the silica surface was also characterized before and after exposure to basic environments. |
| 일반주제명 | Chemistry. |
| 언어 | 영어 |
| 바로가기 | 
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