Photocatalytic Reduction and Removal of Uranium From a Uranium- EDTA Solution
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Consuelo Cerrillos
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
