{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/26283"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/26283","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Precipitation and Dissolution of Uranyl Phosphates in a Mircofluidic Pore Structure","abstract":"The abiotic precipitation of uranium (U(VI)) was evaluated in a microfluidic pore structure (i.e. micromodel) to assess the efficacy of using a phosphate amendment to immobilize uranium in groundwater and mitigate the risk of this contaminant to potential down-gradient receptor sites. U(VI) was mixed transverse to the direction of flow with hydrogen phosphate (HPO42-), in the presence or absence of calcium (Ca2+) or sulfate (SO42-), in order to identify precipitation rates, the morphology and types of minerals formed, and the stability of these minerals to dissolution with and without bicarbonate (HCO3-) present. Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite (also known as hydrogen uranyl phosphate; UO2HPO4), even though the formation of other minerals were thermodynamically favored depending on the experimental conditions. Precipitation and dissolution rates varied with influent conditions. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3 times slower when SO42- was present, and 1.4 times faster when Ca2+ was present. These rates were inversely related to the size of crystals formed during precipitation. Dissolution rates for chernikovite increased with increasing HCO3- concentrations, consistent with formation of uranyl carbonate complexes in aqueous solution, and they were the fastest for chernikovite formed in the presence of SO42-, and slowest for the chernikovite formed in the presence of Ca2+. These rates are related to the ratios of mineral-water interfacial area to mineral volume. Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that changes in the solute conditions evaluated affect precipitation rates, crystal morphology, and crystal stability, but not mineral type.","abstract_html":"The abiotic precipitation of uranium (U(VI)) was evaluated in a microfluidic pore structure (i.e. micromodel) to assess the efficacy of using a phosphate amendment to immobilize uranium in groundwater and mitigate the risk of this contaminant to potential down-gradient receptor sites. U(VI) was mixed transverse to the direction of flow with hydrogen phosphate (HPO42-), in the presence or absence of calcium (Ca2+) or sulfate (SO42-), in order to identify precipitation rates, the morphology and types of minerals formed, and the stability of these minerals to dissolution with and without bicarbonate (HCO3-) present. Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite (also known as hydrogen uranyl phosphate; UO2HPO4), even though the formation of other minerals were thermodynamically favored depending on the experimental conditions. Precipitation and dissolution rates varied with influent conditions. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3 times slower when SO42- was present, and 1.4 times faster when Ca2+ was present. These rates were inversely related to the size of crystals formed during precipitation. Dissolution rates for chernikovite increased with increasing HCO3- concentrations, consistent with formation of uranyl carbonate complexes in aqueous solution, and they were the fastest for chernikovite formed in the presence of SO42-, and slowest for the chernikovite formed in the presence of Ca2+. These rates are related to the ratios of mineral-water interfacial area to mineral volume. Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that changes in the solute conditions evaluated affect precipitation rates, crystal morphology, and crystal stability, but not mineral type.","abstract_has_math":false,"creators":["Fanizza, Michael F."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Environ Engr in Civil Engr","degree_department":null,"school":null,"contributors":["Werth, Charles J.","Strathmann, Timothy J.","Finneran, Kevin T."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-08-26T15:21:25Z","date_published":"2011-08-26T15:21:25Z","updated_at":"2026-07-22T22:25:26Z","subjects":["remediation","uranium","micromodel","precipitation","dissolution"],"languages":["en"],"rights":["Copyright 2011 Michael F. Fanizza"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/26283","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Werth, Charles J.","Strathmann, Timothy J.","Finneran, Kevin T."]},{"key":"dc:creator","label":"Author","values":["Fanizza, Michael F."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-08-26T15:21:25Z","2013-08-27T10:00:19Z","2011-08"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Environ Engr in Civil Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["remediation","uranium","micromodel","precipitation","dissolution"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2011 Michael F. 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Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite (also known as hydrogen uranyl phosphate; UO2HPO4), even though the formation of other minerals were thermodynamically favored depending on the experimental conditions. Precipitation and dissolution rates varied with influent conditions. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3 times slower when SO42- was present, and 1.4 times faster when Ca2+ was present. These rates were inversely related to the size of crystals formed during precipitation. Dissolution rates for chernikovite increased with increasing HCO3- concentrations, consistent with formation of uranyl carbonate complexes in aqueous solution, and they were the fastest for chernikovite formed in the presence of SO42-, and slowest for the chernikovite formed in the presence of Ca2+. These rates are related to the ratios of mineral-water interfacial area to mineral volume. Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that changes in the solute conditions evaluated affect precipitation rates, crystal morphology, and crystal stability, but not mineral type.","Item withdrawn by Rebecca Bryant (rabryant@illinois.edu) on 2011-07-21T18:28:09Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Fanizza_Michael_Thesis.docx: 3969475 bytes, checksum: b3bdb0eaa259ba6383a55c5112985a1b (MD5) Fanizza_Michael.pdf: 2225922 bytes, checksum: be9c98dfcad9dfbbb1568ca76e57f4bb (MD5)","Made available in DSpace on 2011-08-26T15:21:25Z (GMT). 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U(VI) was mixed transverse to the direction of flow with hydrogen phosphate (HPO42-), in the presence or absence of calcium (Ca2+) or sulfate (SO42-), in order to identify precipitation rates, the morphology and types of minerals formed, and the stability of these minerals to dissolution with and without bicarbonate (HCO3-) present. Raman backscattering spectroscopy and micro X-ray diffraction (μ-XRD) results both showed that the only mineral precipitated was chernikovite (also known as hydrogen uranyl phosphate; UO2HPO4), even though the formation of other minerals were thermodynamically favored depending on the experimental conditions. Precipitation and dissolution rates varied with influent conditions. Relative to when only U(VI) and HPO42- were present, precipitation rates were 2.3 times slower when SO42- was present, and 1.4 times faster when Ca2+ was present. These rates were inversely related to the size of crystals formed during precipitation. Dissolution rates for chernikovite increased with increasing HCO3- concentrations, consistent with formation of uranyl carbonate complexes in aqueous solution, and they were the fastest for chernikovite formed in the presence of SO42-, and slowest for the chernikovite formed in the presence of Ca2+. These rates are related to the ratios of mineral-water interfacial area to mineral volume. Fluorescent tracer studies and laser confocal microscopy images showed that densely aggregated precipitates blocked pores and reduced permeability. The results suggest that changes in the solute conditions evaluated affect precipitation rates, crystal morphology, and crystal stability, but not mineral type.","Item withdrawn by Rebecca Bryant (rabryant@illinois.edu) on 2011-07-21T18:28:09Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Fanizza_Michael_Thesis.docx: 3969475 bytes, checksum: b3bdb0eaa259ba6383a55c5112985a1b (MD5) Fanizza_Michael.pdf: 2225922 bytes, checksum: be9c98dfcad9dfbbb1568ca76e57f4bb (MD5)","Made available in DSpace on 2011-08-26T15:21:25Z (GMT). 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