UV-A-a photocatalytic degradation of the radionuclide complexants tributylphosphate and dibutylphosphat

In this study, we evaluate and compare the photocatalytic degradation and mineralization of two alkylphosphates, the tributylphosphate (TBP) and the dibutylphosphate (DBP) in presence of TiO2 irradiated under UV-A. TBP and DBP are chosen because they are frequently present in nuclear reprocessing waste water, where they are used as extractant for cleaning and decontamination purposes. In the first part of the publication, we focus on the degradation of TBP by following its disappearance by GC-MS, the fate of phosphate by 31P NMR analysis and ionic chromatography, its mineralization by TOC measurement and finally the formation of carboxylic acid carbon by HPLC-UV. In the second part of the publication, we compare the kinetic of mineralization of TBP and DBP, the fate of phosphate by $^{31}$P NMR analysis and the nature and evolution of carboxylic acid. Our results show that DBP is an intermediate product of the degradation of TBP and that the nature carboxylic acid formed during the degradation of TBP and DBP are the same. We also show that mineralization process is consistent with the Langmuir-Hinshelwood model and independent of the nature of alkylphosphate.