Degradation of aqueous bisphenol A in the CoCN/Vis/PMS system: Catalyst design, reaction kinetic and mechanism analysis

Low levels of pharmaceutical and personal care products (PPCPs) in the environment have attracted widespread attention as a new class of organic pollutants. Degradation of these PPCPs by optimizing advanced oxidation processes (AOPs) is highly desirable, but remains a huge challenge. Here, the Co sites embedded in carbon nitride catalyst (CoCN) was synthesized by a simple one-step pyrolysis of Co-based Zeolitic Imidazolate Framework-67 (ZIF-67) and melamine, of which highly dispersed Co atom sites were uniformly doped in the CN ring of g-C3N4. In the optimized system of visible light irradiation involving CoCN and peroxymonosulfate (CoCN/Vis/PMS system) (λ ≥ 420 nm, [PMS] = 0.2 g L-1, pH = 7.0), 100% of bisphenol A (BPA, 20 mg L-1) was removed after 2 min and the total organic carbon (TOC) removal rate of BPA reached 88.8% after 90 min reaction. Detailed characterization showed that a specially designed unique Co-N bond structure was crucial for the high degradation performance of BPA in the CoCN/Vis/PMS system. HO∙, SO4∙-, O2∙-, h+ and 1O2 contributed to the BPA degradation in the CoCN/Vis/PMS system. Besides, the effect of solution pH and several common anions in environmental water on BPA removal was evaluated. Several typical pollutants, sulfamethoxazole (SMX), ciprofloxacin (CIP), 4-chlorophenol (4-CP) and atrazine (ATZ), were effectively degraded by the same CoCN/Vis/PMS system, which exhibited universal applicability of this AOP reaction. The cycling degradation experiment showed the stability and reusability of the CoCN/Vis/PMS system. This work offers immense hope to the environmental purification and provides numerous new opportunities for the effective removal of other pollutants beyond BPA, SMX, CIP, 4-CP and ATZ.