Ultraviolet (UV) light-activated persulfate oxidation of sulfamethazine in water

Ultraviolet light (UV)/persulfate (S2O82-) oxidation of a pharmaceutically active compound, sulfamethazine (SMT), was studied in a stainless steel photo-reactor. During the treatment, UV photolytic S2O82- activation to produce highly reactive sulfate radicals (SO4-) to decompose SMT in water. The treatment was advantageous over direct photolysis or persulfate oxidation alone and UV/H2O2 oxidation, suggesting that SO4- is a very effective agent to remove SMT from water. Under the experimental conditions, the SMT degradation exhibited a pseudo-first-order reaction pattern. The degradation rate was influenced by the S2O82- dose and solution pH. Typically, a high persulfate dose could achieve a high SMT removal. In contrast, both the highest SMT degradation rate and the lowest mineralization degree were observed at pH 6.5, while the highest mineralization extent was accomplished at pH 11. The complex pH effect may be associated with the fact that the total radical concentration and fractions of the different radicals were varied with pH. Finally, the major SMT degradation products were identified, and the primary reaction pathways were proposed. This study demonstrated that UV/persulfate is a viable option for controlling SMT pollution in water.

► Effective SMT degradation can be achieved by UV/persulfate oxidation treatment.
► The degradation rate and mineralization degree of SMT were influenced by the S2O82- dose and pH.
► Mass spectrometry was applied for identification of intermediates and products.
► Degradation mechanisms were proposed according to the results of LC–MS analysis.