No abstract

In this study, we evaluate and compare the photocatalytic degradation and mineralization of two alkylphosphates, tributylphosphate (TBP) and dibutylphosphate (DBP), in the presence of TiO 2 and under ultraviolet A radiation. Tri-and dibutylphosphate are used as extractants in nuclear decontamination processes and thus could be found in reprocessing plant waste water. We have investigated the degradation of TBP by gas chromatography-mass spectrometry, the fate of phosphate ions by 31 P NMR and ion chromatography, the mineralization kinetics of TBP and DBP by total organic carbon measurements, and finally, the formation of carboxylic acid by high-performance liquid chromatography with ultraviolet detection. Our results show that DBP is an intermediate product of the degradation of TBP and that the same types of carboxylic acids are formed during the degradation of both compounds. We also show that the kinetics of the mineralization process is well described in both cases by the Langmuir-Hinshelwood model, with identical rate constants.

The 60 Co present in some low-level effluents forms complexes with organic ligands such as ethylenediaminetetraacetic acid (EDTA). These complexes make it difficult to remove the 60 Co using conventional filtration methods. The aim of this study was to test the use of titanium-based photocatalysis (TiO 2 /UV) and photochemical methods involving the use of oxidation agents (H 2 O 2 / UV-C) (both of which are advanced oxidation processes) to degrade EDTA and recover 60 Co once it has been released from the complex. In preliminary experiments on the 59 Co-EDTA complex, we tested the efficiency of the TiO 2 /UV and H 2 O 2 /UV-C processes as means of degrading EDTA molecules and releasing cobalt in its cationic forms Co 2? and Co 3? . These cations can be trapped by either precipitating and/or adsorbing them on TiO 2 depending on the pH. When this treatment was applied experimentally to radioactive wastes, it turned out to be highly effective since it improved the decontamination factor (DF: initial volumic activity/final volumic activity) twofold.