Efficient degradation, mineralization and toxicity reduction of sulfamethoxazole under photo-activation of peroxymonosulfate by ferrate (VI)

The photodegradation of sulfamethoxazole (SMX) based on activation of peroxymonosulfate (PMS) with ferrate (VI) (Fe(VI)) was investigated for the first time. The role of the reagents under different light sources and the effects of reagent dosages as well as solution pH on the SMX degradation were revealed. Besides, the SMX degradation, mineralization, the reaction mechanism, and the toxicity of the degradation products to Artemia salina under various treatment processes with one-off or stepwise dosing of reagents were determined. SMX of 0.1 mM can be completely removed in 8 min under optimal conditions. A mathematic model was proposed to describe the two stage reactions, and the initial decay rate as well as the maximum oxidation capacity were calculated accordingly. Fe(VI) played a dominant role in initial degradation while radicals including SO₄ ^[rad]− and OH^[rad] contributed to continuous degradation. Compared to one-off dosing, stepwise addition of reagents slowed down SMX degradation, while stepwise introduction of Fe(VI) enhanced the mineralization efficiency. The proposed degradation pathways include hydroxylation, carboxylation, nitration and so on. The adverse effect of SMX solution to the feeding of Artemia Salina was abated after treatment. The results from this study demonstrate a good potential of using UVA/Fe(VI)/PMS in treatment of antibiotics in aqueous phase.