Photochemical degradation of dexamethasone by UV/Persulphate, UV/Hydrogen peroxide and UV/free chlorine processes in aqueous solution using response surface methodology (RSM)

Dexamethasone (DEX) degradation was investigated using three UV-based advanced oxidation processes combined with sodium persulphate, hydrogen peroxide, and free chlorine in aqueous solutions in a bench-scale reactor. The goal was to determine which process would be the best option in terms of DEX degradation without the subsequent generation of toxic compounds. The process performance for DEX degradation followed the UV/S2O82-> UV/H2O2> UV/HOCl order under equal conditions. In the UV/S2O82- process, sulphate radicals led to a 70.4% DEX degradation. The experimental mineral inhibitory factors showed that nitrite and bicarbonate further decrease the efficiency of the UV/S2O82- process. In the optimal conditions, the UV/S2O8-2 process removed DEX by 100% and had a 74.1% mineralisation. Furthermore, the intermediates were detected using LC-MS/MS, and the cytotoxicity of the UV/S2O8-2 process effluent was evaluated using human embryonic kidney cultured cells. The treatment of DEX solution by the UV/S2O8-2 process significantly decreased the toxicity of the effluent. Therefore, it can be concluded that the UV/(SO8-2)-O-2 process can be a reliable process for DEX degradation and detoxification in aqueous solutions.