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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] • CoWO 4 /g-C 3 N 4 with matched energy band structure was successfully synthesized. • Hindrance of interfacial barrier in conventional heterojunctions was much reduced. • Pollutants degradation efficiency was greatly improved compared to previous work. • O 2 −, 1O 2 and SO 4 − played an important role in the degradation process of TCH. • The degradation mechanism and pathways of TCH were proposed. Activation of peroxymonosulfate (PMS) by constructing heterojunctions using cobalt-based catalysts under visible light has been widely used for the treatment of emerging pollutants. However, the high recombination rate of photogenerated charge carrier severely inhibited the degradation efficiency of photocatalysts. Herein, CoWO 4 /g-C 3 N 4 was prepared as an efficient PMS activator for the degradation of typical antibiotics according to a rational structural and compositional design via the matching principle of Fermi levels. The morphology, structure and chemical composition of the composites were investigated through a series of characterizations. The tetracycline hydrochloride (TCH) degradation efficiency of 2CoWO 4 /g-C 3 N 4 reached 99.9 % in 10 min at PMS/vis system, with the mineralization performance at 59.8 %. The excellent degradation performance was attributed to the unimpeded photogenerated carrier separation and transfer caused by the matched energy band structure between CoWO 4 and g-C 3 N 4. Also, its degradation performance for Ciprofloxacin (CIP) and Norfloxacin (NOF) was better than the reported non-Fermi level matched heterojunction composed of CoWO 4 and g-C 3 N 4. The results of quenching experiments verified the production and consumption processes of reactive oxidants O 2 −, 1O 2 , SO 4 − and OH. The degradation pathways and mechanism of TCH were also extrapolated in detail. This research provided an in-depth theoretical basis for the design and construction of highly efficient photocatalysts. [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]