Rapid activation of PMS by dual-site functional carbon nitride for continuous removal of PPCPs

A metal-free P/O dual-site functional carbon nitride was synthetized. • P O Lewis-acid centers and O-coordinated electron-rich sites were induced to CN-P5. • CN-P5 removed 5 mg/L APAP within 60 min using 1 mM PMS. • APAP was degraded via hydroxylation, C N scission, ring opening, and mineralization. • PPCPs at realistic level were removed from actual domestic sewage continuously. Peroxymonosulfate (PMS) activation-based advanced oxidation processes provide powerful strategies for persistent pharmaceuticals and personal care products (PPCPs) removal in aquatic environments and wastewater. However, intrinsically sluggish PMS decomposition kinetics and inefficient utilization of reactive species impede their practical implementation. Developing robust, metal-free photocatalysts capable of efficiently activating PMS under mild conditions remains challenging. In this study, a metal-free P/O dual-site functional carbon nitride (CN-P5) featuring localized polarization was rationally constructed via phytic acid-assisted thermal polymerization, enabling efficient PMS activation under visible-light for rapid PPCPs degradation. With 1 mM PMS, complete removal of 5 mg/L acetaminophen (APAP) was achieved within 60 min. The degradation proceeded through hydroxylation, C N scission, ring opening, and progressive mineralization, accompanied by decreasing predicted toxicity of intermediates. Characterizations combined with density functional theory calculations revealed that P atoms partially substitute framework C to generate electron-deficient P O Lewis acid centers, preferentially accumulating photogenerated holes and promoting PMS adsorption. Meanwhile, O atoms coordinate at bridging N sites, giving rise to electron-rich P O units. The synergistic integration of these polarized dual P O dipolar sites boosted PMS activation efficiency. To demonstrate application potential, CN-P5 was packed into a fixed-bed continuous-flow reactor, enabling simultaneous and efficient removal of APAP, norfloxacin and sulfamethoxazole from real lake water matrices. Moreover, the reactor maintains stable removal efficiency for APAP, norfloxacin and ofloxacin continuously at realistic concentrations from actual domestic sewage. Collectively, this work establishes a scalable, metal-free PMS activation platform that couples dual-sites electronic engineering with continuous processing for PPCPs abatement in real waters.