Three-dimensional rGO/CNT/g-C3N4 macro discs as an efficient peroxymonosulfate activator for catalytic degradation of sulfamethoxazole.

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-C3N4) 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.

Cobalt oxide functionalized ceramic membrane for 4-hydroxybenzoic acid degradation via peroxymonosulfate activation.

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 Co3O4 ceramic catalytic membranes with different Co loadings were fabricated via a simple ball-milling and calcination process. Uniform distribution of Co3O4 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 SO4•- and •OH were present in the catalytic process while SO4•- plays the dominant role. The anti-fouling performance of the composite Co@Al2O3 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).

Versatile heterojunction of gold nanoparticles modified phosphorus doped carbon nitride for enhanced photo-electrocatalytic sensing and degradation of 4-chlorophenol.

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.

Highly dispersive Ru confined in porous ultrathin g-C3N4 nanosheets as an efficient peroxymonosulfate activator for removal of organic pollutants.

Ru species were loaded on a two-dimensional (2D) material of graphitic carbon nitride (2D g-C3N4) to serve as the efficient AOP catalysts. The catalytic activity was closely related to the dispersion degree of Ru, as determined by the inherent nanoarchitecture of the supporting material. Ultrathin g-C3N4 nanosheets with a unique porous structure were fabricated by further thermally oxidizing and etching bulk g-C3N4 (bCN) in air. Homogeneous dispersion of Ru species was successfully achieved on the porous few-layered g-C3N4 nanosheets (pCN) by stirring, washing, freeze drying and annealing processes to obtain Ru-pCN catalysts, whereas bCN or multilayered g-C3N4 (mCN) led to the aggregation of Ru nanoparticles in Ru-bCN and Ru-mCN materials. The conventional impregnation method also caused the resulting Ru-pCN-imp catalyst with undesirable Ru aggregation in spite of employing pCN. The optimal 4.4Ru-pCN removed 100% of 2,4,6-trichlorophenol (TCP) within only 3 min, superior to its counterpart samples, and exhibited remarkable degradation efficiencies for methyl orange, neutral red, 4-chlorophenol, tetracycline and oxytetracycline. Mechanistic studies suggested that four radicals, e.g., •OH, SO4• -, O2• - and 1O2 were generated during the peroxymonosulfate (PMS) activation, in which SO4• - and 1O2 played a major role.

Binder free 3D core-shell NiFe layered double hydroxide (LDH) nanosheets (NSs) supported on Cu foam as a highly efficient non-enzymatic glucose sensor.

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.

Heterogeneous activation of peroxymonosulfate by Co-doped Fe2O3 nanospheres for degradation of p-hydroxybenzoic acid.

Environmental remediation has become more effective when using nanotechnologies. In this study, iron oxide (α-Fe2O3) nanospheres with different cobalt doping levels (xCo-Fe2O3) were synthesised and applied in the heterogeneous activation of peroxymonosulfate (PMS) for the degradation of p-hydroxybenzoic acid (p-HBA). The catalyst (3Co-Fe2O3) 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 (SO4•- and •OH) was confirmed by electron paramagnetic resonance (EPR) spectra, whereas partial contribution of oxygen anions and singlet oxygen (O2•-, 1O2) 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.