Co-doped Fe3O4/α-FeOOH for highly efficient peroxymonosulfate activation to degrade trimethoprim: Occurrence of hybrid non-radical and radical pathways

Trimethoprim (TMP), as a widely used chemotherapeutic antibiotic agent, has caused potential risks to the aquatic environment. In this study, magnetic Co-doped Fe3O4/alpha-FeOOH was fabricated by a facile one-step ageing method and used for activation of peroxymonosulfate (PMS) in TMP degradation. It was found that low catalyst (0.5 g/L) and PMS addition (0.2 mM) led to the high degradation efficiency of TMP (97.2%, k(obs) = 0.11211 min(-1)) over a wide range of pH. The oxidation of active radical (SO4 center dot(-)) and non-radical singlet oxygen (O-1(2)) co-acted on TMP degradation. Besides, PMS was activated through the cycles between Co(II)/Co(III) and Fe (II)/Fe(III). Fifteen degradation intermediates of TMP were identified by LC-MS, and three possible degradation pathways including hydroxylation, demethylation, and cleavage were proposed. The recovered catalysts exhibited high stability and reusability, maintaining 80% TMP removal efficiency with inappreciable metal leaching (0.012 mg/L of Co, 0.113 mg/L of Fe) after six cycles. Besides, the Co-Fe3O4/alpha-FeOOH/PMS system was highly tolerant to inorganic anions and actual water bodies (river water, lake water, tap water, and sewage plant effluent). Overall, this work provided a promising way to the potential application of Fe-based binary metal oxide for PMS activation.

Automated summary

In this study, magnetic Co-doped Fe3O4/alpha-FeOOH was fabricated and used for the degradation of trimethoprim (TMP) by activating peroxymonosulfate (PMS). The catalyst showed high efficiency in degrading TMP over a wide range of pH. LC-MS analysis identified fifteen degradation intermediates of TMP and proposed three possible degradation pathways. The recovered catalysts exhibited high stability and reusability, and the system showed high tolerance to inorganic anions and actual water bodies.