Type
Text
Type
Dissertation
Advisor
Holdener, Bernadette C. | Martin A. Schoonen | Michael Sperazza | R James. Kirkpatrick.
Date
2010-12-01
Keywords
adsorption, aluminum (hydr)oxide, phosphate, solid state NMR | Geochemistry -- Environmental Sciences -- Physical Chemistry
Department
Department of Geosciences
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/72582
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
Phosphorus is an essential nutrient for plant growth and agriculture. In aqueous environments, interaction of dissolved phosphate with the surfaces of Al oxyhydroxides and clays is important for controlling its transport, fate and bioavailability. Understanding the reaction mechanisms responsible for phosphate uptake at the molecular level can provide significant insight and improved prediction of phosphate uptake behavior, leading to better strategies for phosphate fertilizationand regulation. In this research, I examined the specific adsorption of phosphate on boehmite (γ-AlOOH) and other Al (hydr)oxides by combining mainly batch sorption techniques, 31P solid-state NMR spectroscopy, quantum chemical calculations and Fouriertransform infrared (FTIR) spectroscopy. Solid state NMR spectroscopy is sensitive with phosphate species that adsorb on mineral surfaces, such that outer-sphere complexes, inner-sphere complexes and surface precipitates can be distinguished.Using novel solid state NMR techniques, such as 31P{1H} cross-polarization magic-angle-spinning (CP/MAS) and 31P{27Al} dephasing curves from rotational echo adiabatic passage double resonance (REAPDOR) experiments, formation of bridging bidentate or monodentate mononuclear surface complexes can be readily determined. In particular, solid state NMR results indicate that bridging bidentate surface complexes is responsible for the dominant uptake mechanism for all Al-oxyhydroxides under all conditions (0.1. 10 mM P; pH 4-10, etc.). Furthermore, two distinct bidentate surface complexes are resolved for adsorbed phosphate on boehmite, even though macroscopic adsorption isotherm is well fitted by a single-siteLangmuir isotherm. The two species exhibit distinct pH-dependence and different protonation states, and further examination of their reaction stoichiometry suggests they might adsorb at different surface sites. In addition, I found that in the presence of dissolved calcium, the mechanism of phosphate uptake is dominant by surfaceprecipitation of calcium phosphates (Ca-P). The Ca-P surface precipitate is identified as poorly crystalline hydroxylapatite by two-dimensional 31P{1H} heteronuclear correlation (HetCor) experiments. To summarize, this dissertation shows 31P solid state NMR is significant sensitivity to the chemical environment and motional property of phosphate adsorbed on different Al (hydr)oxides, from which a better understanding of mineral surfaces can be achieved by using 31P nuclei as a molecular probe.
Recommended Citation
Li, Wei, "Multinuclear Solid-State NMR Studies of Phosphate Uptake by Aluminum (Hydr)oxides" (2010). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 1786.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/1786