Degradation of sulfamonomethoxine by iron–copper catalyst-activated persulfate

Sulfamonomethoxine (SMM) is an emerging organic pollutant that is environmentally persistent, highly toxic, and difficult to degrade, and there is an urgent need to develop efficient degradation methods. Therefore, this paper investigates the degradation of SMM using iron–copper catalyst-activated persulfate (PS). With an iron–copper catalyst amount of 1.5 g/L, initial sodium persulfate solution concentration of 2 mmol L⁻¹, and initial solution pH = 7, the SMM removal rate reached approximately 99.7% after reaction for 2 h. When NO₃⁻ and Cl⁻ coexisted in the system, the degradation efficiency of SMM (more than 99% at 2 h) did not change significantly. When SO₄²⁻ was present in the system, the inhibition effect was insignificant (97.1% at 2 h). The presence of HCO₃⁻ and H₂PO₄⁻ resulted in noticeable inhibitory effects, with SMM degradation rates of 47.4% and 76.8%, respectively. Electron paramagnetic resonance analysis showed that the radical that plays a dominant role in the degradation of SMM in this system is SO₄^−·, Cu(I), Cu(II), and Fe(II) activate PS to produce SO₄^−·, and some SO₄^−· is converted to ^·OH with high redox potential. Therefore, it is assumed that the degradation pathway of SMM involves attack by SO₄^−· and ^·OH, and the formation of corresponding intermediate products, which finally degrade to CO₂, H₂O, and other low-molecular-weight substances, thus achieving degradation.