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[Display omitted] • An energy band-matched efficient photo-Fenton-like reactor was constructed. • Graphitic carbon ring induced successive built-in electric field for PMS activation. • CoWO 4 /GD-CN universally degraded representative contaminants in different fields. • The reaction mechanism enhanced by gradient graphitic carbon rings was proposed. The heterojunction with matched energy band enables efficient peroxymonosulfate (PMS)-based photo-Fenton-like reaction. Nevertheless, the rapid photogenerated charge separation and transfer has been challenging. Herein, we precisely constructed an efficient heterogeneous photo-Fenton-like reactor with successive built-in electric field by gradient doping of coplanar graphitic carbon rings (C gra) into cobalt tungstate/graphitic carbon nitride (CoWO 4 /GD-CN) heterostructure. The as-prepared CoWO 4 /GD-CN exhibited remarkable enhancement with a tetracycline hydrochloride degradation rate constant (0.776 min−1) higher than that of CoWO 4 /CN (0.507 min−1). Theoretical and experimental results demonstrated that the successive built-in electric field enhanced by gradient-doped coplanar C gra ring accelerated photogenerated electrons transfer from the innermost to the outmost layer of CoWO 4 /GD-CN. This transfer drove Co(III)/Co(II) conversion for accelerated PMS activation, leading to enhanced degradation reactivity. CoWO 4 /GD-CN had excellent degradability towards representative contaminants, including carbamazepine (1.0 min−1), 4-chlorophenol (0.920 min−1), sulfamethoxazole (0.90 min−1), bisphenol A (0.933 min−1), atrazine (0.829 min−1), ciprofloxacin (0.589 min−1) and norfloxacin (0.617 min−1) in CoWO 4 /GD-CN/PMS/vis system, respectively. This work provided a novel insight into the gradient-dope modulated photo-Fenton-like reaction and guided the design of efficient photo-Fenton-like reactor. [ABSTRACT FROM AUTHOR]

Breaking hydrogen bond in metal free carbon nitride (CN) to increase peroxymonosulfate (PMS) adsorption for surface-mediated electron transfer has been challenging. Herein, we incorporated N−C N monomer into CN to break hydrogen bond by the introduction of polyvinylpyrrolidone (PVP). The developed nonradical oxidation system achieved selective decomposition of highly hydrophilic contaminants and efficient removal of chemical oxygen demand (58.0%), total phosphorus (88.1%), ammonia nitrogen (100.0%) and total nitrogen (67.8%) from the secondary effluent in a continuous flow reactor. This was attributed to that the breakage of hydrogen bond accelerated the redistribution of electron densities at C and N sites, leading to an increase in the adsorption energy of N site to PMS. This promoted the formation of PVP/CN-PMS* complex for the selective and efficient removal of organics and inorganics. This work provided a new perspective for the selective and long-term treatment of practical wastewater. [Display omitted] • Surface-mediated electron transfer system was constructed by breaking hydrogen bond. • The effect of hydrogen bond in carbon nitride on PMS activation pathway was revealed. • PVP/CN/PMS/vis system selectively remove highly hydrophilic contaminants. • The efficient and continuous flow treatment of practical wastewater was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual electron transfer from TCH and N vacancy to metal for efficient PMS activation. • DFT calculation revealed the direct electron transport from pollutant to Co (III). • Lower EE/O value in PMS/vis system brought more economic benefit. • Recyclable FeCoO x /g-C 3 N 4 -N vac oxidized high-toxic pollutant to less-toxic products. The construction of surface defect was a promising modification strategy to accelerate peroxymonosulfate (PMS) activation mediated by metal for water purification, but intrinsic impact on electron transfer path has been unclear. In this study, nitrogen vacancies (V n) were introduced into graphite carbon nitride and coupled with iron-cobalt bimetals (FeCoO x /CN-V n). Experimental and theoretical results confirmed that V n not only provided abundant electrons to reduce Fe(III)/Co(III) into Fe(II)/Co(II), but also induced the extraction of electrons from pollutant to electron-poor Co(III) for a faster Co(III)/Co(II) cycle. The sustainable dual-path electron transfer effectively overcame the obstacle of low-valence metal regeneration in conventional PMS-based oxidation, increasing the degradation rate constant of tetracycline hydrochloride, a typical refractory pollutant, from 0.2479 to 0.6674 min−1 in the first 2 min. The impacts of environmental factors (pH, PMS dosage, types of oxidants, water matrix) were investigated. Also, the effect of co-existing inorganics and organics was explored using a response surface quadratic model. The evaluation of electrical energy consumption and stability confirmed the outstanding practical application prospect of FeCoO x /CN-V n. Finally, degradation pathways of TCH were elucidated and toxicity of the products was evaluated using quantitative structure activity relationship (QSAR). This study not only furnished a novel insight into the defect-assisted PMS activation, but also achieved in-situ utilization of contaminant for efficient wastewater treatment. [ABSTRACT FROM AUTHOR]

Limited peroxymonosulfate (PMS, HSO 4 −) activation efficiency resulted from slow metal reduction has been a challenge in visible-light (vis) assisted sulfate radical-based oxidation. Herein, a Z-scheme photocatalyst composed of nitrogen-defect-rich graphitic carbon nitride nanosheets embedded with nickel cobaltate nanoparticles (NiCo 2 O 4 /g-C 3 N 4 -N vac) was elaborately designed to accelerate Ni(III)/Ni(II) and Co(III)/Co(II) cycles for PMS activation in PMS/vis system. The NiCo 2 O 4 /g-C 3 N 4 -N vac exhibited remarkable enhancement with a tetracycline hydrochloride (TCH) degradation rate constant (0.1168 min−1), higher than those of NiCo 2 O 4 /g-C 3 N 4 (0.0724 min−1) and g-C 3 N 4 (0.0233 min−1), respectively. Also, the removal efficiencies of 95.5%, 94.2%, 98.0% and 91.4% for carbamazepine, 4-chlorophenol, atrazine and p-nitrophenol were achieved within 30 min, respectively. Theoretical and experimental results suggested that nitrogen (N) vacancies modulated electric structure to build Z-scheme-charge-transfer platform for rapid reduction of Ni(III) and Co(III), thereby accelerating PMS activation for remarkable removal of emerging pollutants. NiCo 2 O 4 /g-C 3 N 4 -N vac exhibited excellent stability and corresponding electrical energy per order (EE/O) in different water matrix was evaluated. Additionally, TCH degradation behavior, pathways and toxicity of products were analyzed, respectively. This work provided an novel paradigm to design the efficient photo-activator of PMS for environmental remediation. [Display omitted] • Z-scheme NiCo 2 O 4 /g-C 3 N 4 -N vac was designed to accelerate PMS activation. • N vacancies lower barrier for achieving Z-scheme charge transfer route. • NiCo 2 O 4 /g-C 3 N 4 -N vac had remarkable performance for various emerging pollutants. • Lower EE/O values in different water matrix engendered more economic benefits. • Degradation pathway and toxicity of products was proposed. [ABSTRACT FROM AUTHOR]