Co and S dual-doped carbon derived from endogenous sulfur-containing 2-thiobarbituric acid: application in PMS activation for ultra-rapid degradation of norfloxacin

Abstract

Heteroatom doping represents an effective strategy for enhancing the catalytic performance of materials. A cobalt–sulfur/carbon catalyst (denoted as Co₉S₈/C) was synthesized via high-temperature calcination using an endogenous sulfur-containing precursor, 2-thiobarbituric acid. The as-prepared Co₉S₈/C was employed as a heterogeneous catalyst to activate peroxymonosulfate (PMS) for the degradation of norfloxacin (NOR). Interestingly, under the optimized conditions of 0.05 g L⁻¹ Co₉S₈/C, 0.3 g L⁻¹ PMS, and pH 7, NOR degradation efficiencies of (50 mg L⁻¹, 50 mL) 84.0% and 93.6% were achieved in 3 and 15 min, respectively. NOR removal efficiency still remained 73.8% after 5 cycles. Radical scavenging experiments showed that the NOR degradation mechanism involved coordinating sulfate radicals (SO₄˙⁻), hydroxyl radicals (˙OH), superoxide radicals (O₂˙⁻), and singlet oxygen (¹O₂), with the latter playing a significant role. Specifically, ¹O₂ was demonstrated to dominate the efficient removal of NOR. The results from the electron paramagnetic resonance (EPR) experiment evidenced that Co₉S₈/C triggered rapid PMS activation in 3 min. This study offers a novel highly effective PMS activator preparation method and encourage its effective and practical application in the rapid degradation of organic pollutants.