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Spinel oxides can be considered effective heterogeneous catalysts in activating peroxymonosulfate (PMS) for wastewater decontamination. However, the intrinsic characteristics of agglomeration and metal ion leaching impede its further application. In this work, to further improve the catalytic efficiency and stability of the catalyst, ZIF-8 was employed as the candidate and further etched by tannic acid (TA) to obtain a core-shell structure with less mass transfer resistance. Following this, CoFe 2 O 4 was anchored on TA-ZIF-8 matrix via a hydrothermal method. Benefiting from the tailored core-shell structure and high activity of CoFe 2 O 4 , the as-prepared CoFe 2 O 4 @TA-ZIF-8 catalyst shortened the mass transfer distance of radical to target pollutant, thus realizing high radical utilization efficiency. Accordingly, 98.1% of tetracycline (TC) can be eliminated in 30 min with kinetic constants 3.15 times higher than pristine CoFe 2 O 4. Besides, the TC degradation efficiency can still maintain 84.1% after five consecutive cycles with cobalt leaching lower than 0.306 mg/L, showing favorable stability compared with pristine CoFe 2 O 4. Furthermore, electron paramagnetic resonance (EPR) and quenching experiments exhibited that singlet oxygen and sulfate radicals play dominant roles in TC degradation processes. This work fabricates an efficient CoFe 2 O 4 @TA-ZIF-8 heterogeneous catalyst for degrading refractory TC, which may possess potential applications in wastewater treatment. [Display omitted] • CoFe 2 O 4 was anchored on TA etched ZIF-8 matrix with core-shell structure. • CF@TA-ZIF-8 possessed enhanced TC removal efficiency than pristine CoFe 2 O 4. • ROS utilization efficiency and mass transfer ability was optimized by confinement. • 1O 2 and SO•− 4 were the dominated ROS in TC degradation process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Perovskite-based catalyst was modified to improve catalytic activity. • Membrane filtration and catalytic oxidation was integrated effectively. • Abundant channel-assisted reaction sites were formed on membrane structure. • Refractory pollutants can be degraded by catalytic membrane in the presence of NOM. • Continuous outflow of feed stream guarantee favorable stability of membrane. Catalytic membrane that can simultaneously enable physical separation and advanced oxidation process is considered as a novel approach for wastewater remediation; however, the unsatisfied catalytic performance and instability impede its further application. In this study, Fe doped LaCoO 3 perovskite with tunable electron structure was employed as a heterogeneous catalyst and incorporated with Polyacrylonitrile ultrafiltration membrane via a controlled phase inversion method. Owing to the continuous outflow of the intermediates and enriched concentration gradients in membrane channels, the catalytic membrane exhibited exceptional catalytic performance and stability under cross-flow apparatus. Correspondingly, over 99% of tetracycline hydrochloride can be degraded via activating peroxymonosulfate in 36 min under the flux of 220 L/m2h. Besides, the catalytic membrane with suitable pore size could exclude natural organic matter and selectively assist the degradation of pollutants in membrane channels due to a massive generation of sulfate radicals and singlet oxygen (equivalent to a retention time of 1.64 s). Following this, the degradation pathways and toxicity analysis of the intermediates were investigated to further verify the catalysis mechanism and the reduced toxicity of treated solution. Overall, it can be concluded that the integration of membrane and catalytic oxidation is effective for enhancing wastewater purification efficiency. [ABSTRACT FROM AUTHOR]

[Display omitted] • In situ mineralization method was used to anchor β-FeOOH in confined membrane pores. • Highly dispersed nanocatalysts were constructed in membrane structure. • Confined pore structure increases the effective contact of radicals and pollutants. • High rejection and rapid pollutants degradation can be realized simultaneously. Heterogeneous advanced oxidation process performs a promising perspective in the field of refractory pollutant degradation. However, the agglomeration and difficulty-to-recycle characters of the heterogeneous catalysts greatly impede its further development. In this study, membrane-confined pores were employed as the immobilization support to anchor highly dispersed β-FeOOH via an in situ mineralization method, which not only exposed highly active sites for refractory pollutants degradation but also endowed the membrane with hydrophilic/underwater superoleophobic properties. Accordingly, the Polyvinylidene fluoride/β-FeOOH (PVDF/β-FeOOH) catalytic membrane demonstrated favorable separation capacity and attractive catalytic oxidation performance via activating peroxymonosulfate. Instantaneous degradation (contact time about 1 s) of recalcitrant pollutants (over 98%) and high oil rejections (96.4% to 99.1%) can be achieved simultaneously under low operating pressure. Both the confined pore structure-induced enhanced mass transfer and enrichment of radicals and pollutants lead to favorable catalytic degradation performance. The mechanism of the catalytic membrane was analyzed by radical quenching test and electron paramagnetic resonance analysis, proving that sulfate radicals were predominant reactive oxygen species during catalytic oxidation. Besides, the PVDF/β-FeOOH catalytic membrane also possessed attractive stability without tedious catalyst separation/recovery processes. This work provides a meaningful tactic to further enhance the catalytic oxidation performance of catalytic membrane in water treatment. [ABSTRACT FROM AUTHOR]

Rational design of hydrophilic hierarchical structures on the membrane surface is a promising method to improve oil/water separation efficiency. However, oil droplets with intrinsic adhesion tend to accumulate on the membrane surface, which deteriorates membrane performance. In this study, tannic acid-Zn(II) complex was homogeneously anchored on the PVDF membrane surface and further in situ converted to ZIF-8 in the presence of 2-methylimidazole. Subsequently, Cu ion exchange was employed to transfer ZIF-8 layer to gerhardtite (Cu 2 (OH) 3 NO 3) with a hierarchical structure. Accordingly, the as-prepared PVDF/TA-gerhardtite membrane possessed attractive hydrophilicity and underwater superoleophobicity with oil contact angles above 150°, therefore achieving over 98 % oil rejection towards various surfactant stabilized oil-in-water emulsions. Moreover, self-cleaning properties can be realized by activating peroxymonosulfate, and 97 % of tetracycline hydrochloride, the target pollutant, was degraded within 30 min owing to the generation of sulfate radicals and hydroxyl radicals. Due to the attractive hydrophilicity and catalytic oxidation capacity of the gerhardtite hierarchical structure, degradation and bubble generation induced fouling recovery was accomplished after PMS cleaning, and the irreversible fouling decreased to 2.2 % after consecutive soybean oil fouling. Therefore, this work provides new insights into the construction of hierarchical structures on membrane surfaces and demonstrates their potential applications in oil/water separation and fouling mitigation. [Display omitted] • A gerhardtite hierarchical structure is formed on the PVDF membrane surface. • In situ conversion and ion exchange are employed to realize homogeneous modification. • PVDF/TA-gerhardtite membrane exhibits attractive oil/water separation efficiency. • The membrane features attractive stability and anti-fouling performance. • Irreversible oil fouling was significantly reduced in the presence of PMS. [ABSTRACT FROM AUTHOR]

The immobilization of heterogeneous catalysts on membrane supports can realize highly efficient degradation of organic pollutants to alleviate membrane fouling through in situ catalytic oxidation. In this work, a polyacrylonitrile (PAN)-based catalytic membrane was prepared via a phase inversion method in the presence of core-shell structured perovskite catalysts. Following this, a controlled alkali-induced strategy was employed to simultaneously hydrolyze the –CN groups on the membrane surface and the core-shell structured perovskite catalysts anchored in the membrane matrix. Correspondingly, improved hydrophilicity, permeability, and catalytic efficiency via activating peroxymonosulfate were achieved compared with pristine PAN membrane. Rapid tetracycline (TC) elimination (10 ppm, 500 mL) can be realized (99 % in 30 min) under a flux of 334.5 L/m2h (0.02 MPa). Besides, owing to the intrinsic size sieving of the membrane, favorable TC degradation efficiency can also be accomplished in the presence of humic acid. Furthermore, the accumulation of pollutants on the membrane surface was released owing to the massive generation of sulfate radicals and singlet oxygen, enabling self-cleaning properties. More importantly, the as-prepared catalytic membrane possessed attractive stability with the cobalt leaching below 0.013 mg/L. This work provides a method to synergistically enhance permeability, catalytic activity and anti-fouling performance of the membranes, which shows potential application in wastewater decontamination. [Display omitted] • Core-shell structured perovskite catalyst was incorporated in the membrane matrix. • Alkaline modification was used to improve hydrophilicity and catalytic activity. • Membrane filtration and catalytic oxidation were integrated effectively. • Rapid TC degradation was realized more efficiently by enhanced mass transfer. • Membrane possessed attractive stability and self-cleaning properties. [ABSTRACT FROM AUTHOR]

Catalytic membrane with physical size sieving and peroxymonosulfate-induced catalytic oxidation is appealing for wastewater remediation. However, restricted by the retention time of the contaminant in membrane, exceptional degradation efficiency is usually achieved at lower permeation conditions. Herein, to improve the permeance while maintaining high degradation efficiency, heterogeneous Cu doping was employed to tune the electronic structure of LaCoO 3 perovskite, and the catalytic activity was further optimized by modulating Cu: Co ratios. Besides, Cu-doped LaCoO 3 was anchored in a SiO 2 fiber membrane with decent connectivity. Benefiting from the enriched local concentration of the reactants and highly connected fiber structures, attractive catalytic efficiency and permeability can be achieved simultaneously. About 99% of tetracycline hydrochloride (TC) was degraded within 12 min with a k constant of 0.4765 min−1, and the flux reached up to 2575.4 L/m2h under gravity, which was 10–70 times higher than other reported catalytic membranes. Density functional theory proved the enhanced interaction between PMS and catalytic membrane, and mechanism analysis demonstrated that singlet oxygen and sulfate radicals dominated the TC degradation process. Furthermore, the catalytic membrane also possessed favorable stability and regeneration capacities. This work highlights a promising strategy for fabricating high-efficient catalytic membranes, which can improve wastewater remediation efficiency. [Display omitted] • Cu doping was employed to tune electronic structure and activity of LaCoO 3. • Cu doped LaCoO 3 was anchored in membrane structure to fabricate reaction sites. • Membrane filtration and catalytic oxidation was integrated effectively. • Rapid TC degradation was realized more efficiently by enhanced mass transfer. • The catalytic membrane performed favorable permeability and catalytic efficiency. [ABSTRACT FROM AUTHOR]

Development of axial nitrogen-coordination engineering strategy. Regulation of single-atom catalyst coordination environment. Fenton-like reaction performance enhancement. Structure-performance relationship establishment. [Display omitted] • Axial coordination regulation strategy of single-atom catalyst is developed. • Intrinsic catalytic activities of Fe-N x single-atom sites are identified. • Axial N-coordination enhances Fenton-like reaction performance over Fe-N 5 species. • Role of axial N-coordination for weakening H 2 O adsorption is revealed. Activating hydrogen peroxide (H 2 O 2) to produce hydroxyl radical (•OH) (Fenton-like process) is of great importance in heterogeneous catalytic oxidations. However, most of transition metal nano-catalysts as well as recently reported carbon supported Fe-N 4 single atom catalysts (SACs) suffer from unsatisfactory catalytic performance. Herein, a novel Fe 1 /C 3 N 4 SAC with Fe-N 5 active site was constructed. Using this SAC, the electron/structure-symmetry of Fe-N 4 site can be broken by axial nitrogen-coordination, which transforms less active Fe-N 4 species into highly active Fe-N 5 species in Fenton-like reaction. Specifically, Fe-N 5 site exhibits an unprecedented activity for 3,3′,5,5′-tetramethylbenzidine oxidation, which is at least one order of magnitude more active than reported Fe-N 4 /C SACs. Mechanism studies reveal that the unique role of axial nitrogen-coordination over Fe-N x sites is to change the adsorption behavior of H 2 O over Fe-N 5 site without influencing H 2 O 2 activation. This discovery provides a new approach for rationally designing efficient catalysts in Fenton-like reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • An extension of classic deep oxidation CuMnOx catalysts to selective oxidation of alcohol with high efficiency. • CuMnOx catalysts characterized by Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 and CuO-Cu 1.4 Mn 1.6 O 4 oxide pairs. • Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 oxide pair is more active than CuO-Cu 1.4 Mn 1.6 O 4 oxide pair. • Rich Cu+ species in Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 oxide pair is essential to achieve high catalytic activity. This work presents an extension of classic deep oxidation CuMnOx catalysts to a selective oxidation of alcohol with high efficiency and in an environmental-friendly reaction system. A series of CuMnOx catalysts characterized by CuO-Cu 1.4 Mn 1.6 O 4 and Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 oxide pairs were prepared via a novel half carbonized citrus grandis peel assisted hard template method. A shift of the oxide pairs from CuO-Cu 1.4 Mn 1.6 O 4 to Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 has been achieved by tuning Cu/Mn molar ratio, and then leads to a one-pass benzaldehyde yield more than 50% with 100% benzaldehyde selectivity in the selective oxidation of benzyl alcohol using H 2 O 2 as oxidant. Higher relative amount of Cu 1.4 Mn 1.6 O 4 in either Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 or CuO-Cu 1.4 Mn 1.6 O 4 oxide pair is found to be essential for achieving high catalytic activity. The interaction between the Cu 1.4 Mn 1.6 O 4 constituent and Mn 2 O 3 constituent of Mn 2 O 3 -Cu 1.4 Mn 1.6 O 4 oxide pair is found to able to enhance the formation of Cu+ species, which can reacts with H 2 O 2 to produce •OH and then touch off a Fenton-like catalytic oxidation process of benzyl alcohol, in the current CuMnOx-H 2 O 2 system, to produce benzaldehyde with high selectivity. This work presents a new perspective in the development of highly effective and low cost CuMnOx catalysts for heterogeneous catalytic oxidation reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new understanding in the active site of CuMnOx catalysts. • CuMnOx catalysts are composed by uniform CuO-Mn 2 O 3 oxide pairs. • Highly isolated CuO nano-particles are essential for CuO-Mn 2 O 3 oxide pairs. • Cu-O-Mn sites are found to be the active sites of CuO-Mn 2 O 3 oxide pairs. The current work provide a new understanding on the active site of CuMnOx catalysts and thus offer a new perspective in the development of highly effective and low cost CuMnOx catalysts for heterogeneous catalytic oxidation reactions. A series of dual-component copper-manganese multi-oxide catalysts (CuMnOx) have been successfully synthesized using a surfactant assisted hydrolysis-hydrothermal method and studied by XRD, N 2 adsorption–desorption test, ICP-AES, SEM, Aberration-corrected HADDF-STEM, HRTEM, FT-IR, Raman, XPS, H 2 -TPR. These CuMnOx catalysts were found to be composed with uniform CuO-Mn 2 O 3 oxide pair structure, in which highly isolated/dispersed CuO species are anchored in the framework of Mn 2 O 3. It was found that the speciation in these CuMnOx catalysts presents a shift from highly isolated or even single Cu2+ oxide species (Cu2+Ox) to CuO nanoclusters and CuO microcrystalline with increasing Cu content. In CO oxidation reaction, which was employed to probe the structure of the CuO-Mn 2 O 3 oxide pairs in these CuMnOx catalysts, the Cu-O-Mn sites in those CuMnOx catalysts with highly isolated or highly dispersed CuO species were found to be highly active. For CuO-Mn 2 O 3 oxide pair catalysts, the highly isolated/dispersed CuO species in Mn 2 O 3 framework is essential to achieve high activity. [ABSTRACT FROM AUTHOR]

• The g-C 3 N 4 @Fe was firstly used as the catalyst for cataluminescence (CTL)-based sensing for H 2 S. • A home-designed system was developed for reliable preparation and introduction of H 2 S samples. • The sensing performance was comparable to or better than previous works on CTL-based sensing for H 2 S. • The method was applicable for home-made real samples with high accuracy. A home designed cataluminescence (CTL)-based gas sensor was developed with high selectivity and sensitivity, using g-C 3 N 4 @Fe composite as the catalyst for the detection of hydrogen sulfide (H 2 S) in a controllable manner. Intensive CTL was generated due to the effectively catalytic oxidation of H 2 S on the surface of the g-C 3 N 4 @Fe but none from diverse possible gas interferents including other sulfides or thiols, which was also proportional in intensity to the H 2 S concentration. The prepared g-C 3 N 4 @Fe was thoroughly characterized by TG, FTIR, XRD, SEM, XPS and TEM, and the sensing parameters were optimized. It turned out that 0.36% Fe contained in the g-C 3 N 4 could lead to the most intensive CTL from H 2 S, with a linear range of 10–500 μmol•mol−1 (i.e. ppm) and a limit of detection 1.5 μmol•mol−1. The proposed method also showed other attractive features including rapidness, simple equipment and low cost. [ABSTRACT FROM AUTHOR]