A spectroscopic investigation of phosphate reactions with thin film oxides /
Phosphate adsorption by hematite, titania, and alumina was
| Main Author: | |
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739669031&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Phosphate adsorption by hematite, titania, and alumina was examined by exposing freshly prepared thin films to phosphate solutions and subsequently analyzing the surfaces by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and atomic force microscopy (AFM). Thin hematite coatings exhibited adsorption and desorption behavior similar to that previously observed in natural systems. Hematite exposed to a sodium phosphate solution at incremental times demonstrated initially rapid phosphate uptake during the first 10 min of solution exposure, followed by a 10 min induction period after which phosphate accumulated as a species different than that adsorbed initially. For titania and alumina exposed to a calcium phosphate solution at incremental times, the initially rapid reaction was completed after 1 and 3 h, respectively. Subsequent rapid accumulations occurred after 3 to 4 h for titania and 25 to 30 h for alumina. The data for these two oxides were comparable to in-situ studies using the same solutions. AFM images of hematite and alumina revealed the formation of structures 200 to 500 nm in size after exposure to phosphate solution for a period of time conducive to three dimensional growth. We postulate that phosphate chemisorbs initially as an inner-sphere complex, but with continued exposure, it forms three-dimensional structures. |
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| Item Description: | Vita. "Major Subject: Soil Science". |
| Physical Description: | xv, 155 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 148-154. |