Treatment of tributyl phosphate by fenton oxidation: Optimization of parameter, degradation kinetics and pathway

In nuclear industry, tributyl phosphate (TBP) is used as organic extracting solvent to separate uranium and plutonium. The spent TBP is finally discarded as the radioactive organic waste, which should be treated due to its potential risk. In this study, TBP degradation by Fenton oxidation was investigated in detail, including the optimization of operational conditions, degradation kinetics and degradation products. The optimal conditions for TBP degradation (per 10 ml) by Fenton oxidation was: 95 °C, pH 2, 150 ml 30% H₂O₂, and 105 ml 0.2 M Fe(II). H₂O₂ was continuously added with the flow rate of 0.5 ml/min, Fe(II) was intermittently added with the flow rate of 3 ml/10 min. The oil phase volume decreased with time and completely disappeared at the third hour. In contrast, the COD in water phase increased firstly and then decreased. At the end of the experiments, the COD achieved 23.8 g/L. The detection of phosphorus in water phase further confirmed the decomposition of TBP. Mono-butyl phosphate and di-butyl phosphate were identified as the intermediate products of TBP degradation. In addition, other four degradation products with the same m/z of 154 were identified, which may be derived from the hydroxylation of mono-butyl phosphate and di-butyl phosphate. Based on the degradation products, the degradation pathway of TBP was proposed. This study could provide an insight into the TBP degradation by Fenton oxidation, and an potential strategy for treating the spent radioactive organic solvent.