Photocatalytic Reduction and Removal of Uranium From a Uranium- EDTA Solution
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Abstract
The removal, from aqueous solution, of uranyl ions by adsorption in the absence and presence of the chelant EDTA, and the photocatalytic removal by reduction of uranium from U:EDTA solutions is reported. Uranyl (UO22+) adsorption at pH6 approaches saturation at about 40 ppm UO2(NO3)2. Adsorption is negligible at pH 2, and increases to a maximum at pH = 7-8, then declines at pH 10. The increased adsorption is consistent with a progressively higher deprotonation of TiO2 surface sites, whereas the decrease at pH 10 corresponds to partial conversion of positive uranyl specie, UO22+, to a negatively charged hydroxy complex, UO2(OH)3-. Added EDTA competes for uranyl with the surface sites, and a monotonic diminution of adsorbed uranium is observed with increasing EDTA level. At 1:1 U:EDTA ratio, the adsorbed metal increases monotonically from zero at pH 2 to a maximum at pH 10 (more basic conditions were not explored), a result reflective of the stability of the U:EDTA complex. Under illumination in the absence of dissolved oxygen, the uranium (VI) in solution (free and complexed) decreases indicating a reductive process for the metal. The apparent first order rate constant for disappearance is observed to decrease with increasing pH, i.e. the rate constant is maximum at pH 2 and smallest at pH 10. Centrifugation of catalyst and exposure of supernatant for 24 h to air results in regaining the original uranyl (VI) concentration at pH near 2 and 5; in contrast, one day exposure to air provides no reoxidation of supernatants at pH 7 or 10. These results indicate that uranyl is photocatalytically reduced to a lower, positive oxidation state to form a positive specie which adsorbs appreciably only under neutral/ basic conditions, above the isoelectric point of TiO2.
© 2017 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Masthead
- Contents
- Preface
- Editorial
- Research Articles
- Activity, and Hardness of Supported TiO2 Films on Pyrex and Soda-Lime Glass in Photocatalytic Degradation of Formic Acid for 50 Days
- Endurance Test of TiO2-Based Photocatalytic Oxidation
- Photocatalytic Inactivation of Different Bacteria and Bacteriophages in Drinking Water at Different TiO2 Concentration With or Without Exposure to O2
- Solar Photochemical Detoxification and Disinfection for Water Treatment in Tropical Developing Countries
- Photodegradation of Phenol in Water using Silica-Supported Titania Catalysts
- Photocatalytic Decomposition of Chlorinated Benzaldehydes in Aqueous Solution Using TiO2
- Photocatalytic Reduction and Removal of Uranium From a Uranium- EDTA Solution
- Figures-of-Merit for Advanced Oxidation Technologies: A Comparison of Homogeneous UV/H2O2, Heterogeneous UV/TiO2 and Electron Beam Processes
- Gas-Phase Destruction of VOCs Using TiO2/UV and TiO2/O3/UV
- Mass Transfer Considerations in the Design of Vapor-Phase photocatalytic Reactors
- A Simple Kinetic Model for the Simultaneous Concentration and Intensity Dependencies of TCE Photocatalyzed Destruction
Articles in the same Issue
- Masthead
- Contents
- Preface
- Editorial
- Research Articles
- Activity, and Hardness of Supported TiO2 Films on Pyrex and Soda-Lime Glass in Photocatalytic Degradation of Formic Acid for 50 Days
- Endurance Test of TiO2-Based Photocatalytic Oxidation
- Photocatalytic Inactivation of Different Bacteria and Bacteriophages in Drinking Water at Different TiO2 Concentration With or Without Exposure to O2
- Solar Photochemical Detoxification and Disinfection for Water Treatment in Tropical Developing Countries
- Photodegradation of Phenol in Water using Silica-Supported Titania Catalysts
- Photocatalytic Decomposition of Chlorinated Benzaldehydes in Aqueous Solution Using TiO2
- Photocatalytic Reduction and Removal of Uranium From a Uranium- EDTA Solution
- Figures-of-Merit for Advanced Oxidation Technologies: A Comparison of Homogeneous UV/H2O2, Heterogeneous UV/TiO2 and Electron Beam Processes
- Gas-Phase Destruction of VOCs Using TiO2/UV and TiO2/O3/UV
- Mass Transfer Considerations in the Design of Vapor-Phase photocatalytic Reactors
- A Simple Kinetic Model for the Simultaneous Concentration and Intensity Dependencies of TCE Photocatalyzed Destruction
