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The catalytic membrane, which combines the physical barrier and peroxymonosulfate (PMS)/visible light (Vis)-induced catalytic oxidation functionalities while minimizing biofouling, exhibits great promise as a material for the removal of persistent organic pollutants from wastewater. In this study, three catalytic membranes composed of 2D/2D hybrid g-C 3 N 4 /kaolinite with nitrogen vacancies and modified with different iron species (γ-FeOOH nanosheets, Fe 2 O 3 quantum dots, and Fe single atoms) were prepared via vacuum filtration. Evaluation of the catalytic performance demonstrated that γ-FeOOH nanosheets-modified sample exhibited a relatively higher water flux (258.13 L m-2 h-1). In contrast, Fe single atom-modified sample achieved improved bisphenol A removal efficiency (97.39%) under the PMS/Vis synergetic system. Interestingly, the Fe 2 O 3 quantum dots-modified sample exhibited the highest rate constant based on the retention time. Furthermore, the Fe single atom-modified sample showed consistent removal of bisphenol A, reaching nearly 100% during continuous-flow operation for 180 min, while maintaining a flux of approximately 200 L m-2 h-1. Quenching experiments suggested that •O 2 −, 1O 2 , and h+ were the most important oxidizing species involved in the reaction of the three membranes. Statistical analysis indicated that variations in the average pore size of the membranes were key factors influencing the catalytic activity. Overall, this study offers an in-depth insight into the systematic and quantitative assessment of 2D/2D hybrid g-C 3 N 4 /layered clay-based catalytic membranes for wastewater treatment. [Display omitted] • The catalytic performance of three iron species-based membranes for bisphenol A removal were compared. • Fe single atom modified membrane showed more superior catalytic performance. • Fe 2 O 3 quantum dots modified membrane possessed the largest rate constant. • The catalytic performance was significantly correlated with surface area and average pore size. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel nZVI/kaolinite composite was prepared by liquid-phase reduction method. • nZVI particles with oxide layer were embedded into kaolinite surface and edges. • nZVI/kaolinite exhibits high efficiency for BPA removal with PMS activation. • SO 4 •− and 1O 2 were proved to be the main active components. • The possible degradation pathways were well analyzed and illustrated. Nano-zero valent iron/kaolinite (nZVI/kaolinite) composite was prepared by liquid-phase reduction method in the presence of sodium borohydride. Transmission Electron Microscope images demonstrated that spherical nZVI particles with oxide layer were successfully engaged into the kaolinite surface and edges, which was beneficial to the peroxymonosulfate (PMS) activation and bisphenol A (BPA) degradation. The prepared nZVI/kaolinite composite was endowed with excellent performance in removing BPA with the assistance of PMS, namely more than 95% BPA could be eliminated in 15 min. In contrast with alkaline environment, weak acid and neutral environment were more advantageous to the BPA degradation. All the anions like Cl−, SO 4 2−, HCO 3 − and H 2 PO 4 − were adverse to the BPA degradation in nZVI/kaolinite/PMS system. Furthermore, EPR and radical quenching experiments proved that SO 4 •− and 1O 2 were the main active components during the series reactions. The possible degradation pathways were also inferred based on the liquid chromatography-mass spectrometry (LC-MS) results. Besides, the nZVI/kaolinite composite displayed good performance toward coking wastewater as well. This study is of great significance in designing of efficient persulfate activated materials and treating wastewater. [ABSTRACT FROM AUTHOR]

Inspired by the features of both transition metal oxide and natural clinoptilolite (flaky structure with suitable pore diameter and open skeleton structure), we adopted a robust strategy by immobilization of nickel ferrite nanoparticles (NiFe 2 O 4) on the clinoptilolite surface via typical citric acid combustion method. The hybrid catalyst exhibited enhanced peroxymonosulfate (PMS) activation efficiency and bisphenol A (BPA) degradation performance. Calculated by effective equivalent of NiFe 2 O 4 , it is found that the reaction rate constant (k) of NiFe 2 O 4 /clinoptilolite/PMS system (0.1859 min−1) was 11.9 times higher than that of bare NiFe 2 O 4 /PMS system (0.0156 min−1), which demonstrated that catalyst would be conjugated to PMS or contaminant efficiently and renders the rapid degradation and mineralization in the presence of clinoptilolite. After comprehensive characterization analysis and DFT simulations, natural mineral carrier effect (i.e. decreased crystalline size, increased oxygen vacancy content, etc.), abundant surface-bonded and structural hydroxyl groups as well as effective bonding with iron or nickel ions charged for the potential activation mechanism of PMS by NiFe 2 O 4 /clinoptilolite composite. And it is indicated that not only •OH and SO 4 •−, but also 1O 2 was involved into series reactions. Overall, this study put forward a green and promising technology for high-toxic wastewater treatment. ga1 • NiFe 2 O 4 /clinoptilolite was structural assembled through spontaneous combustion. • Carrier effect and hydroxyl groups bonding with metal ions charged for the activation mechanism. • The reaction rate constant of NiFe 2 O 4 /clinoptilolite was 11.9 times higher than that of bare NiFe 2 O 4. • This study put forward a green and promising technology for high-toxic wastewater treatment. [ABSTRACT FROM AUTHOR]

• Diatomite and CoFe 2 O 4 was effectively assembled to activate peroxymonosulfate. • CoFe 2 O 4 /diatomite catalyst has lower metal dissolution rate. • Surface structure and crystallization dispersion improve activation performance. • The 1O 2 was the primary active substance for BPA degradation. • Weak basic condition enhanced PMS activation and increased BPA degradation. Porous magnetic CoFe 2 O 4 /diatomite catalyst (CFD) was rationally synthesized via a facile citrate combustion process. The relationship between catalytic performance and material properties of the prepared catalysts was comprehensively investigated by various characterizations, especially for the interface interaction between CoFe 2 O 4 and diatomite as well as crystallization regulation of CoFe 2 O 4. Overall, higher specific surface area, overspreading surface hydroxyl groups, better crystal dispersion and abundant surface-active sites make CFD have better degradation performance of bisphenol A (BPA) than pure CoFe 2 O 4 in the presence of peroxymonosulfate (PMS), and the pseudo-first-order reaction rate constant of 40-CFD (40% CoFe 2 O 4 /diatomite) is almost 5.32 times higher than that of pure CoFe 2 O 4. Besides, CFD has excellent magnetic properties, lower metal dissolution rate and good reusability. In addition, electron paramagnetic resonance (EPR) and radical quenching experiments show that sulfate radicals (SO 4 −) and singlet oxygen radicals (1O 2) generated from the electron transfer of BPA molecule and valence state change of transition metals should be the predominant oxidation species. Moreover, possible degradation pathways of BPA are determined by the detection of intermediates derived from the results of liquid chromatograph–mass spectrometer (LC–MS). In brief, it is indicated that the CoFe 2 O 4 /diatomite composite material is an efficient and environmentally friendly catalyst, which has a great potential application in wastewater treatment by activating PMS. [ABSTRACT FROM AUTHOR]