Fabrication of Tubelike Co3O4 with Superior Peroxidase-Like Activity and Activation of PMS by a Facile Electrospinning Technique

Activation of peroxymonosulfate by α-MnO2 for Orange Ⅰ removal in water

Developing high-efficiency catalysts for peroxymonosulfate (PMS)-based advanced oxidation processes is important for eliminating pollutants in water. Herein, α-MnO₂ with major exposed {110} and {100} facets prepared via a hydrothermal method were used as catalysts to activate PMS for the degradation of Orange Ⅰ (OⅠ). α-MnO₂-100, with more abundant surface hydroxyl groups and greater reductive ability, performed remarkably better than α-MnO₂-110 for degrading OⅠ. OⅠ removal of 86.20% was obtained in the α-MnO₂-100/PMS system. The apparent rate constant of OⅠ removal over α-MnO₂-100 was 2.11 times higher than that of α-MnO₂-110. The effects of PMS concentration, catalyst dosage, OⅠ concentration, initial pH, anions and humic acid (HA) on OⅠ degradation in the α-MnO₂-100/PMS system were systematically investigated. Quenching experiments and electron paramagnetic resonance (EPR) demonstrated that SO₄^•-, •OH, O₂^•- and ¹O₂ were the reactive oxygen species (ROS) in the α-MnO₂-100/PMS system. Moreover, the possible degradation pathway of OⅠ in the α-MnO₂-100/PMS system was proposed. This work provides an ideal metal oxide catalyst for sewage remediation.

Enhancement strategies for efficient activation of persulfate by heterogeneous cobalt-containing catalysts: A review

As a clean and efficient technology for the degradation of organic contaminants, sulfate radical based advanced oxidation processes (SR-AOPs) have attracted more and more attention in the past decades. Cobalt is regarded as the most reactive and efficient non-noble metal catalyst for the activation of persulfate including peroxymonosulfate (PMS) and peroxydisulfate (PDS) to produce sulfate radicals. Due to the limitations of homogeneous catalytic systems, the heterogeneous cobalt-containing catalysts have been emerged and rapidly developed. Various strategies have been schemed to further enhance the activation ability of persulfate by heterogeneous cobalt-containing catalysts. This paper provides an overview on the recent progress in enhancement strategies for the highly efficient activation of persulfate by heterogeneous cobalt-containing catalysts. With a brief introduction on the chemistry and feature of sulfate radical reactions catalyzed by homogeneous Co²⁺/Co³⁺ species, the main strategies for enhancing persulfate activation by heterogeneous cobalt-containing catalysts are summarized, such as surface and morphology design, multiple reactive centers design, organic-inorganic hybrids and heterostructure composites. Future perspectives of heterogeneous SR-AOPs systems catalyzed by cobalt-containing catalysts are outlined.

The synergistic interactions of reaction parameters in heterogeneous peroxymonosulfate oxidation: Reaction kinetic and catalytic mechanism

The reaction parameters including catalyst dosage, oxidant amount, initial contaminant concentration and pH etc. play the crucial roles in the heterogeneous persulfate oxidation processes, while the synergistic interactions among these reaction parameters are still obscure. We herein took an efficient heterogeneous persulfate oxidation system "bimetallic Mn_xCo_3-xO₄ solid solution (MnCo) activated peroxymonosulfate (PMS)" for carbamazepine (CBZ) removal from water. MnCo/PMS system exhibited outstanding performance that CBZ was completely removed within 10 min. The CBZ degradation performance was ascribed to the radical oxidation of SO₄^·- and O₂·^-, the nonradical oxidation of ¹O₂, the redox cycles between Mn and Co species and synergistic interactions among MnCo, PMS and CBZ. By monotonously or synchronously adjusting the MnCo dosage, PMS amount and initial CBZ concentration, the inherent connections of different reaction parameters were established. Strong and different synergistic interactions between MnCo and PMS, and among MnCo, PMS and CBZ, were existed due to the formation of three different reaction modes when reaction parameters met certain conditions. The features of the modes were "two-stage, the following auto-deceleration", "one-stage, constant velocity" and "two-stage, the following auto-acceleration". This discovery may provide new insights into the synergistic interactions of reaction parameters in advanced oxidation processes for wastewater treatment.

2D N-Doped Porous Carbon Derived from Polydopamine-Coated Graphitic Carbon Nitride for Efficient Nonradical Activation of Peroxymonosulfate

Nitrogen-doped carbon materials attract broad interest as catalysts for peroxymonosulfate (PMS) activation toward an efficient, nonradical advanced oxidation process. However, synthesis of N-rich carbocatalysts is challenging because of the thermal instability of desirable nitrogenous species (pyrrolic, pyridinic, and graphitic N). Furthermore, the relative importance of different nitrogenous configurations (and associated activation mechanisms) are unclear. Herein, we report a "coating-pyrolysis" method to synthesize porous 2D N-rich nanocarbon materials (PCN-x) derived from dopamine and g-C₃N₄ in different weight proportions. PCN-0.5 calcined at 800 °C had the highest surface area (759 m²/g) and unprecedentedly high N content (18.5 at%), and displayed the highest efficiency for 4-chlorophenol (4-CP) degradation via PMS activation. A positive correlation was observed between 4-CP oxidation rates and the total pyridinic and pyrrolic N content. These N dopants serve as Lewis basic sites to facilitate 4-CP adsorption on the PCN surface and subsequent electron-transfer from 4-CP to PMS, mediated by surface-bound complexes (PMS-PCN-0.5). The main degradation products were chlorinated oligomers (mostly dimeric biphenolic compounds), which adsorbed to and deteriorated the carbocatalyst. Overall, this study offers new insights for rational design of nitrogen-enriched carbocatalysts, and advances mechanistic understanding of the critical role of N species during nonradical PMS activation.

Electrospun Foamlike NiO/CuO Nanocomposites with Superior Catalytic Activity toward the Reduction of 4-Nitrophenol

Foamlike NiO/CuO nanocomposites were prepared using a simple electrospinning technique combined with appropriate calcination. By tuning the Ni/Cu molar ratio (1:2, 1:1, and 2:1) in the initial material, different NiO/CuO nanocomposites were obtained. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherms were used to characterize the composites. Furthermore, they were investigated as catalysts for the reduction of 4-nitrophenol (4-NP) in the presence of NaBH₄. The test results demonstrate that the nanocomposite with Ni/Cu = 1:1 presents the best catalytic activity for its high content of surface oxygen vacancy and specific surface area.

Colorimetric method for glucose detection with enhanced signal intensity using ZnFe2O4-carbon nanotube-glucose oxidase composite material

In this paper, a composite material comprised of ZnFe2O4 nanomaterial, carbon nanotubes (CNT) and glucose oxidase (GOD) was synthesized and used for glucose detection. ZnFe2O4-CNT was formed by a one-step solvothermal approach using acid-treated CNT as precursor, then GOD was linked to it by coupling reaction between -NH2 and -COOH. After addition of glucose, which is oxidized by GOD, the intermediate product (H2O2) further oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) substrate and forms a blue product. This process was accelerated in the presence of peroxidase-mimic ZnFe2O4 nanomaterial and the detected signal intensity was correspondingly enhanced. The linear detection range of glucose was 0.8 to 250 μM, with a limit of detection of 0.58 μM. This may originate from (1) the limited diffusion of intermediate species, which resulted in enhanced local concentrations of reaction compounds; (2) enhanced electron transmission among CNT, GOD and ZnFe2O4; (3) the synergistic enhancement of catalytic activity of ZnFe2O4 compared with other metal oxides; (4) the high loading capacity of ZnFe2O4-CNT for GOD molecules, because of its high surface-to-volume ratio. Meanwhile, this method has reasonable selectivity, stability and reusability and can be used for real serum detection, which may be useful for the development of sensitive biosensors.

Hierarchical mesoporous cobalt silicate architectures as high-performance sulfate-radical-based advanced oxidization catalysts

Self-sacrificial biomass-derived silica is a rising and promising approach to fabricate large metal silicates, which are practical water treatment agents ascribed for easy sedimentation and separation. However, the original biomass architecture is difficult to be maintained and utilized. Furthermore, sufficient ion diffusion pathways need to be created to satisfy massive mass transport in large bulk materials. Herein, a series of metal silicates, including cobalt silicate (CoSiO_x), copper silicate, nickel silicate, iron silicate, and magnesium silicate, are synthesized from Indocalamus tessellatus leaf as the biomass-derived silica source and investigated as catalysts in sulfate-radical-based advanced oxidization processes (SR-AOPs) for the first time. Among them, CoSiO_x presents an analogical sandwich structure as a leaf-derived template of micron-level size. More importantly, the interior hollow nanotubes assembled by small nanosheets provide numerous pathways for ion diffusion and remarkably promote the mass transport in such large bulk materials. Owing to the combination of the unique structure with the high reactivity of Co (II) toward peroxymonosulfate, CoSiO_x exhibits excellent catalytic performance with 0.242 and 0.153 min^-1 rate constants for the removal of methylene blue and phenol, respectively, which outperforms/is comparable to that of the reported nanomaterials toward organic contaminants in SR-AOPs.

Carbon fiber-assisted iron carbide nanoparticles as an efficient catalyst via peroxymonosulfate activation for organic contaminant removal

The introduction of carbon fibers enhances the ability of iron carbide nanoparticles to activate PMS to remove contaminants.

The efficiency and mechanism of dibutyl phthalate removal by copper-based metal organic frameworks coupled with persulfate

Copper-based metal organic framework (Cu-BTC) was prepared and used to remove dibutyl phthalate (DBP) in the presence of persulfate (PS). The surface characteristics, textural properties, and stability of activated Cu-BTC (denoted as Cu-BTC-A) were evaluated by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N2 physical adsorption-desorption, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The effects of parameters such as initial pH, PS concentration, catalyst dosage, and free-radical quenchers have been investigated. The results showed that DBP could be removed in a wide pH range by Cu-BTC-A via mechanisms of adsorption and heterogeneous catalytic reaction. Unfortunately, the DBP removal was not completed because of radical scavenging reactions in Cu-BTC-A cages where PS can enter freely but DBP is blocked outside. Another explanation was that Cu-BTC-A showed a low adsorption capacity for DBP because the molecular size of DBP (15.84 × 11.00 × 7.56 Å) is larger than microporous cages (approximately 9 × 9 Å in diameter) of Cu-BTC-A.