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[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]

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]

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]