A study of uranium and molybdenum in a South Texas lignite /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | The modes of occurrence of uranium and molybdenum in a South Texas lignite (Eocene, Jackson Group, Whitsett Formation) have been investigated in detail. The distribution of uranium and molybdenum in the whole coal density separates indicates variable modes of occurrence predominantly in finely disseminated form. The relative enrichment of uranium in the heaviest density separate indicates the presence of mineralized uranium. Uranium and molybdenum extraction efficiencies for most of the organic solvents studied were low and it appears that these elements are not occurring in significant amounts as low molecular weight organometallics. Significant amounts of the metals including uranium and molybdenum appear to be strongly associated with the humic acids. The humic acids have been separated into three M.W. fractions (110,000,24,000, and 7,000 daltons) by gel filtration chromatography. The humic acids have also been separated into five molecular weight fractions (ranging from >100,000 to <1000) by ultrafiltration for the determination of the uranium and molybdenum distribution. The >100,000 M. W. Fraction contained 78 percent of the uranium and the <1000 M. W. fraction contained 67 percent of the molybdenum. Sequential extraction of the lignite with hydrochloric acid solutions ranging in pH from 3.0 to 0.7 produced a uranium extraction curve that is similar in shape to the acid dissociation cures of metal complexes. The good fit between curves for the first hydrochloric acid lignite extraction and calculated pH dependent uranyl-humate extraction are consistent with an exchange between the uranyl ions and hydrogen ions at the humic acid sites. Calculations indicate that approximately 80 percent of the uranium is humically associated. Poorly crystalline uranium oxide minerals (possible uraninite) were found in the >2.90 g/ml fraction of the low temperature ash by SEM-EDS. These minerals appear to be precipitated onto clay particles. The uranium oxide minerals account for 10 to 20 percent of the uranium present in the lignite. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xxiii, 242 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |