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[Display omitted] Increasing water pollution has imposed great threats to public health, and made efficient monitoring and remediation technologies critical to a clean environment. In this study, a versatile heterojunction of Au nanoparticles modified phosphorus doped carbon nitride (Au/P-CN) is designed and fabricated. The Au/P-CN heterostructure demonstrates improved light absorption, rapid separation of charge carriers, and improved electrical conductivity. Taking the toxic 4-chlorophenol (4-CP) as an example, an ultrasensitive photoelectrochemical (PEC) sensor is successfully demonstrated, exhibiting a wide linear range (0.1–52.1 μM), low detection limit (∼0.02 μM), significant stability and selectivity, as well as reliable analysis in real samples. Moreover, efficient photocatalytic degradation with a high removing efficiency (∼87%) toward 4-CP is also achieved, outperforming its counterpart of Au nanoparticles (NPs) modified graphitic carbon nitride (Au/g−CN, ∼59%). This work paves a new way for efficient and simultaneous detection and remediation of organic pollutants over versatile photoactive catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiFe LDH NSs were synthesized on the in situ grown CuNWs over a Cu foam substrate. • NiFe LDH NSs demonstrate effective non-enzymatic glucose sensing. • The unique structure facilitates the mass transport and charge transfer. • An ultralow detection limit and superior sensitivity are achieved. Rational design with fine-tuning of the electrocatalyst material is vital for achieving the desired sensitivity, selectivity, and stability for an electrochemical sensor. In this study, a three-dimensional (3D) hierarchical core–shell catalyst was employed as a self-standing, binder-free electrode for non-enzymatic glucose sensing. The catalyst was prepared by decorating the shell of NiFe layered double hydroxide (LDH) nanosheets (NSs) on the core of Cu nanowires (NWs) grown on a Cu foam support. The optimized 3D core–shell Cu@NiFe LDH sensor demonstrated higher sensitivity (7.88 mA mM-1cm−2), lower limit of detection (0.10 µM) and wider linear range (1 µM to 0.9 mM) in glucose sensing with a low working potential (0.4 V). The applied sensor also showed excellent stability, reproducibility, interference ability as well as practicability in real environment. The detection of real samples further suggests its great feasibility for practical applications. The superior electrocatalytic performance is collectively ascribed to the excellent electro-conductivity of the Cu substrate, the distinct self-standing 3D porous nanostructure, the ultrathin homogenous architecture, and the appropriate loading amount of NiFe LDH NSs. This study then provides a non-enzymatic glucose sensor with 3D Cu@NiFe LDH electrode for ultrahigh sensitivity and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cobalt doped Fe 2 O 3 nanospheres were synthesised via a solvothermal route. • 3% cobalt doping was most efficient for peroxymonosulfate activation in degradation of p-hydroxybenzoic acid. • Identification of free radicals was done by quenching tests and electron paramagnetic resonance spectra. • Detailed mechanistic studies on peroxymonosulfate activation and degradation pathways were performed. Environmental remediation has become more effective when using nanotechnologies. In this study, iron oxide (α-Fe 2 O 3) nanospheres with different cobalt doping levels (xCo-Fe 2 O 3) were synthesised and applied in the heterogeneous activation of peroxymonosulfate (PMS) for the degradation of p-hydroxybenzoic acid (p-HBA). The catalyst (3Co-Fe 2 O 3) with 3% Co doping exhibits the best performance for PMS activation, possibly because of the larger specific surface area and the tailored catalyst surface as confirmed by X-ray photoelectron spectroscopy (XPS). Reaction parameters were investigated to optimise the degradation efficiency. The metal ions leaching tests confirmed the higher stability of the catalyst, thanks to the leaching suppression by the doping of Co2+. The main contribution of free radicals (SO 4 •- and •OH) was confirmed by electron paramagnetic resonance (EPR) spectra, whereas partial contribution of oxygen anions and singlet oxygen (O 2 •-, 1O 2) was observed during the quenching tests. Finally, a radical based degradation mechanism was proposed for the removal of p-HBA. It is expected to open up a novel perspective for the application of iron oxide as a potential catalyst for the removal of emerging contaminants. [ABSTRACT FROM AUTHOR]

[Display omitted] • A perforated CuFe 2 O 4 /Fe 2 O 3 composite was designed by a MOF-derived solid-state process. • The composite shows efficient PMS activation for sulfamethoxazole degradation. • Both radical and non-radical degradation contributed to SMX remediation. • Possible degradation mechanisms were proposed. • The catalyst shows excellent stability and reusability via magnetic recovery. Design of metal–organic framework (MOF) derived metal oxides is an effective approach for environmental remediation. The current study describes the fabrication of MIL-53-derived perforated CuFe 2 O 4 /Fe 2 O 3 using a facile, one-step, post-thermal solid-state approach by varying Cu/Fe ratios. Herein, the release of CO 2 and H 2 O during the thermal treatment facilitates the incorporation of Cu2+ onto the Fe 2 O 3 structure, forming a perforated hollow CuFe 2 O 4 /Fe 2 O 3 composite via an in-situ ion-exchange mechanism. The optimised catalyst CF-0.5 displays a high degradation efficiency for the removal of sulfamethoxazole (SMX) by heterogeneous activation of peroxymonsulfate (PMS), ascribing to the better textural, morphological, and elemental properties of the novel catalyst. Important reaction parameters such as pH, catalyst loading, PMS dosage, pollutant kind and concentration, and reaction temperature are further optimised to develop a cost-effective catalytic system. The magnetically recoverable catalyst outlines a high stability rate, and only a 9 % efficiency loss is observed even after the fourth cycle. Reactive oxygen species (ROS) are identified by electron paramagnetic resonance spectroscopy (EPR) and their roles are determined by performing quenching experiments. In the end, a detailed study of the mineralisation ability and reaction intermediates is performed and possible pathways for the degradation mechanism are proposed. This study not only introduces a facile approach for the fabrication of MOF-driven nanomaterials but provides insights into the removal of emerging contaminants such as SMX. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel g-C 3 N 4 /Fe 2 O 3 /rGO ternary composite was synthesised using a hydrothermal process. • The catalyst exhibits a high photocatalytic oxidation efficiency for the removal of sulfamethoxazole. • Reactive oxygen species were identified by quenching tests and electron paramagnetic resonance spectra. • Detailed mechanistic studies were performed to deduce the radical and non-radical degradation pathways. Rational design of semiconductor photocatalysts is an effective way to achieve efficient visible-light-driven environmental remediation. Herein, a series of graphitic carbon nitride (g-C 3 N 4) engineered hematite (Fe 2 O 3)/reduced graphene oxide (rGO) photocatalysts were synthesised and employed in visible-light-driven photo-Fenton-like degradation of sulfamethoxazole (SMX). The exceptional performance of the optimal photocatalyst (0.4-FerGCN-3) was achieved because of the successful structural integration of g-C 3 N 4 /Fe 2 O 3 /rGO for efficient separation and migration of photoinduced charge carriers (e−/h+). Photochemical decomposition efficiency was also optimised by analysing the important reaction parameters such as initial catalyst loading, initial H 2 O 2 dosage, pH, and reaction temperature. Detailed studies on the generation of reactive species and degradation intermediates were performed to propose a possible mechanism for SMX degradation. The findings may provide not only a strategy for nanostructure engineering of semiconductor photocatalysts but also insights into the effective remediation of emerging contaminants such as SMX. [ABSTRACT FROM AUTHOR]

[Display omitted] • α-Fe 2 O 3 of cuboid/rhombohedral, spheroidal, rice-like, and plate-like were synthesised. • Photo-Fenton-like degradation of p-hydroxybenzoic acid (p-HBA) and sulfachloropyridazine (SCP) was conducted. • Correlation among atomic configuration of the exposed facets, specific surface area and photocatalytic activity was established. • Degradation mechanism and pathways for p-HBA and SCP were proposed. Hematite (α-Fe 2 O 3) with different shapes and preferentially exposed facets may differ in surface energy and atomic configuration resulting in versatile catalysis. Herein, four morphologies of α-Fe 2 O 3 nanocrystals, e.g. cuboid/rhombohedral, spheroid, rice-like, and plate-like are synthesised by hydrothermal/solvothermal routes. The correlation between morphology and photochemical performance is established by investigating the photo-Fenton-like degradation of p-hydroxybenzoic acid (p-HBA) and sulfachloropyridazine (SCP). The plate-like sample demonstrates the highest removal efficiency, whereas the normalised reaction rate by specific surface area shows the reaction order as cuboid/rhombohedral > plate-like > spheroid > rice-like. This can be ascribed to the synergistic role of the surface atomic arrangement and specific surface area. The main reactive species and degradation pathways were studied in detail. The research findings may offer new insights into the morphology/facet-dependent photochemical remediation of emerging contaminants (ECs) on α-Fe 2 O 3. [ABSTRACT FROM AUTHOR]

Over the past few years, advanced oxidation processes (AOPs) have shown promising efficiencies for wastewater remediation. Carbocatalysis, in particular, has been exploited widely thanks to its sustainable and economical properties but has an issue of recovery and reusability of the catalysts. To address this, three-dimensional (3D) binary and ternary graphene-based composites in the form of macro discs were created to activate peroxymonosulfate (PMS) for catalytic oxidation of sulfamethoxazole (SMX). Graphene oxide served as the base, while graphitic carbon nitride (g-C 3 N 4) and/or single-walled carbon nanotubes (SWCNTs) were added. Among the various discs synthesized, rGNTCN discs (ternary composite) were proven to be the most efficient by completely degrading SMX in 60 min owing to their large surface area and nitrogen loading. The catalytic system was further optimized by varying the reaction parameters, and selective radical quenching and electron paramagnetic resonance tests were performed to identify the active radical, revealing the synergistic role of both radical and non-radical pathways. This led to the development of possible SMX degradation pathways. This research not only provides insights into ternary carbocatalysis but also gives a novel breakthrough in catalyst recovery and reusability by transforming nanocatalysts into macro catalysts. [Display omitted] • Novel graphene-based binary and ternary macro discs were fabricated. • The discs can activate peroxymonosulfate (PMS) for catalytic oxidation. • The identification of dominant reactive species was conducted. • PMS activation and sulfamethoxazole degradation pathways were illustrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel nitrogen-doped graphene cubes (NGCs) were synthesised. • The lightweight NGCs were employed for sulfamethoxazole (SMX) degradation. • Identification of reactive oxygen species was conducted. • Comprehensive mechanistic studies on SMX degradation were performed. As a sustainable and green approach, carbocatalysis, a metal-free strategy, has shown exceptional results in advanced oxidation processes (AOPs). Nonetheless, the recovery of these catalysts has been a major shortcoming over the years. Herein, three-dimensional nitrogen-doped graphene macrostructures (3D-NGMs), in the form of macro cubes, were synthesised by a simple cross-linking and thermal annealing procedure, after which they were employed in the activation of peroxydisulfate (PS) for the degradation of sulfamethoxazole (SMX). The catalytic cubes were loaded with different amounts of nitrogen precursor to investigate the role of nitrogen configuration in the sp2 hybridised carbon network on AOPs. NGC3 cubes with optimum N-loading exhibited outstanding performance for SMX degradation owing to their optimum N/C ratio. Various reaction parameters were studied to optimise the catalytic system. Comprehensive studies on the radical generation were done and illustrated the dominance of the non-radical pathway leading to the proposal of a possible reaction mechanism for SMX. This study not only suggests the role of nitrogen doping on graphene macrostructures but also provides novel insights into macro catalysis to overcome the recovery challenges posed by nano catalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen-doped reduced graphene oxide beads (NrGOb) were fabricated by a one-step self-assembly strategy. • The lightweight NrGOBs and peroxymonosulfate system presented high activity in oxidative degradation of organic pollutants. • The catalytic beads were packed in a fixed-bed column reactor to maintain a continuous process. • Reactive radicals were identified by the quenching tests and electron paramagnetic resonance spectra. • Mechanistic studies on peroxymonosulfate activation and degradation pathways of hydroxybenzoic acid were performed. Metal-free graphene-based catalysts have demonstrated excellent performance in advanced oxidation processes (AOPs). However, the recovery and reusability of these nanocatalysts are still a major issue. In this study, three dimensional (3D) nitrogen-doped reduced graphene oxide beads (NrGOb) were synthesized via a self-assembly method and then applied in heterogeneous activation of peroxymonosulfate (PMS) for the oxidation of hydroxybenzoic acid (HBA). The materials (NrGOb) were annealed at various temperatures ranging from 500 to 1000 °C, and the resulting NrGOb derived from 800 °C (NrGOb-800) exhibited the best performance for PMS activation. To avoid the challenging recovery, the degradation experiments were also performed in a packed-bed catalytic reactor. Various reaction parameters were investigated to optimize the efficiency of the system. Electron paramagnetic resonance (EPR) and quenching tests were carried out to differentiate the contribution of reactive radicals (SO 4 •- and •OH) in the degradation process and then aided in illustrating the degradation mechanism. Finally, the stability and reusability of the catalytic beads were investigated. The efficiency slightly declined with increased cycles; however, catalyst regeneration would be able to partially restore the active sites. The results suggest the feasibility of exploiting graphene-based macrostructures on the AOPs platform for the degradation of organic pollutants in commercial wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Membrane separation and sulfate radicals-based advanced oxidation processes (SR-AOPs) can be combined as an efficient technique for the elimination of organic pollutants. The immobilization of metal oxide catalysts on ceramic membranes can enrich the membrane separation technology with catalytic oxidation avoiding recovering suspended catalysts. Herein, nanostructured Co 3 O 4 ceramic catalytic membranes with different Co loadings were fabricated via a simple ball-milling and calcination process. Uniform distribution of Co 3 O 4 nanoparticles in the membrane provided sufficient active sites for catalytic oxidation of 4-hydroxybenzoic acid (HBA). Mechanistic studies were conducted to determine the reactive radicals and showed that both SO 4 •− and •OH were present in the catalytic process while SO 4 •− plays the dominant role. The anti-fouling performance of the composite Co@Al 2 O 3 membranes was also evaluated, showing that a great flux recovery was achieved with the addition of PMS for the fouling caused by humic acid (HA). [Display omitted] • Co 3 O 4 integrated ceramic membranes were fabricated via a simple ball-milling and sintering approach. • Catalytic oxidation of 4-hydroxybenzoic acid was conducted in a crossflow membrane reactor. • Both SO 4 •− and •OH were present in the degradation with SO 4 •− as the dominant species. • Anti-fouling performance of the membranes was observed. [ABSTRACT FROM AUTHOR]