Ibuprofen degradation and toxicity evolution during Fe2+/Oxone/UV process

This study shows the degradation of ibuprofen in aqueous solution using oxone process mediated by Fe2+ with UV irradiation (FOU). Fe2+/Oxone (FO), Fe2+/UV (FU), Oxone/UV (OU) processes were investigated separately to elucidate the role of different conditions in the processes. The effects of UV wavelength, the dosage of Fe2+, the dosage of oxone, initial target compound concentration, solution pH and anions on the degradation efficiency were studied. In general the FOU is best performed among the processes. About 97% of 0.05 mM ibuprofen was removed in 10 min, under the optimal conditions of FOU (wavelength = 300 nm, [Fe2+]0 = 0.25 mM, [Oxone]0 = 0.25 mM, and pH = 3.68). Subsequent tests like the mineralization efficiency and toxicity evolution were also conducted to ensure the FOU is a safe and comprehensive treatment process after the ibuprofen is removed. However, the above optimal conditions for IBP degradation were found inadequate in the TOC and toxicity tests. After cross examining the test results and intermediates, it was found that the low TOC and toxicity removal was mainly due to the accumulation of toxic intermediates in the solution. It is therefore suggested that a stepwise introduction of Fe2+and oxone (to control the radical concentration at a lower level, so as to minimize the futile consumption of radicals) with an elevated dosage of [IBP]0:[Fe2+]0:[Oxone]0 to 1:25:25 (to effectively degrade the unwanted intermediates at the later stage of reaction) is an efficient approach to ensure the TOC removal and toxicity elimination in FOU.