CoO-3D ordered mesoporous carbon nitride (CoO@mpgCN) composite as peroxymonosulfate activator for the degradation of sulfamethoxazole in water

Highlights: • 3D-mesoporous carbon nitride-CoO composites were synthesized and studied. • Nano-CoO particles and unique surface structure led to high catalytic reactivity. • High degree of SMX degradation occurred in the pH range of 3–9. • SO₄⁻ and OH radicals were responsible for SMX degradation. • CoO@mpgCN composite exhibited high catalytic stability and usability. A facile impregnation method was used to fabricate a hybrid CoO-3D ordered mesoporous carbon nitride (CoO@mpgCN) catalyst that effectively activated peroxymonosulfate (PMS) for the degradation of pharmaceutical chemical, exemplified by antibiotic sulfamethoxazole (SMX) in aqueous solutions. The CoO@mpgCN/PMS system exhibited high catalytic reactivity and SMX removal efficiency over a wide pH range with an observed rate constant (k_obs) of 0.314 min⁻¹. Furthermore, CoO@mpgCN was stable with consistently high degree of SMX degradation without having cobalt dissolution and loss of catalytic activity for at least five consecutive cycles. The significant catalysis performance of CoO@mpgCN was due to its uniformly distributed mesopores, large specific surface area, and high electron transfer ability at the active CoO sites. Both quenching experiments and electron paramagnetic resonance (EPR) analysis verified the yield, in abundance, of highly active species, specifically SO₄⁻ and OH from the CoO@mpgCN activation of PMS, primarily. Hence, SMX degradation followed a radical chain reaction mechanism. The result of this study revealed a novel prospective of CoO@mpgCN composite as PMS activator for the remediation of recalcitrant pollutants in water.