Peroxymonosulfate activation for efficient sulfamethoxazole degradation by Fe₃O₄/Β-FeOOH nanocomposites: Coexistence of radical and non-radical reactions

Environmental friendly magnetic Fe₃O₄/β-FeOOH nanocomposites with low cost were prepared via a simple one pot method and their physiochemical properties were investigated. The Fe₃O₄/β-FeOOH nanocomposites efficiently catalyzed the activation of peroxymonosulfate (PMS) for sulfamethoxazole (SMX) degradation and can be easily recovered through magnetic separation. The effects of catalyst dosage, PMS dosage, temperature and pH were evaluated. The catalyst showed great stability and reusability based on the successive degradation cycles. The reactive oxygen species (ROS) including sulfate radical (SO₄ ^−[rad]), hydroxyl radical ([rad]OH) and singlet oxygen (¹O₂) were generated in the Fe₃O₄/β-FeOOH/PMS system, while both of SO₄ ^−[rad] and ¹O₂ were dominantly attributed to the SMX degradation. The special tunnel-type structure and surface oxygen vacancies of β-FeOOH may be responsible for the high catalytic activity towards PMS to degrade SMX. At last, the catalytic mechanism of PMS on the surface of catalysts were proposed.