Exploiting calcinated CoFe-layered double hydroxide for the photo-persulfate catalytic degradation of sulfamethoxazole

This study synthesized CoFe-layered double oxide (CoFe-LDO) from CoFe-layered double hydroxide (CoFe-LDH) via simple calcination. The resulting CoFe-LDO material was characterized and first employed as a heterogeneous catalyst for sulfamethoxazole (SMX) degradation. The synergic activation of persulfate (PS) by CoFe-LDO in the presence of UV light was demonstrated in a degradation study. The UV/CoFe-LDO/PS system (pronounced as photo-PS system) achieved approximately 98 % SMX removal within 60 min with 0.1 g/L catalyst and 5 mM PS concentration. Compared with the control experiments, the PS was effectively activated by the CoFe-LDO, which degrades SMX in the presence of UV light. The effects of catalyst dosage and PS concentrations were examined, and 0.1 g/L CoFe-LDO and 5 mM PS were determined to be optimal for achieving complete SMX degradation within 60 min. Furthermore, the CoFe-LDO catalyst exhibited superior catalytic activity under weakly acidic pH conditions (i.e., pH 5–6). Reactive oxygen species were identified by scavenging experiments and electron spin resonance, suggesting that SO₄^•− and •OH radicals as well as ¹O₂ contributed to the SMX degradation. This finding proposed a plausible mechanism for SMX degradation in the UV/CoFe-LDO/PS system. Furthermore, nine by-products after the photo-PS process were identified, which were supposed to be generated through radical and non-radical pathways. This work offers a simple strategy for developing a sustainable, efficient, and effective catalyst for degrading persistent organic pollutants from water.