Degradation Of P-nitrophenol Research Articles

Mn-Fe Dual-Metal Assemblages on Carbon-Coated Al2O3 Spheres for Catalytic Ozonation Oxidation: Structure, Performance, and Reaction Mechanism.

Catalysts with high catalytic activity and low production cost are important for industrial application of heterogeneous catalytic ozonation (HCO). In this study, we designed a carbon-coated aluminum oxide carrier (C-Al2O3) and reinforced it with Mn-Fe bimetal assemblages to prepare a high-performance catalyst Mn-Fe/C-Al2O3. The results showed that the carbon embedding significantly improved the abundance of surface oxygen functional groups, conductivity, and adsorption capacity of γ-Al2O3, while preserving its exceptional mechanical strength as a carrier. The prepared Mn-Fe/C-Al2O3 catalyst exhibited satisfactory catalytic ozonation activity and stability in the degradation of p-nitrophenol (PNP). Electron paramagnetic resonance (EPR) and quenching experiments reveal that radical ( ⋅ OH and ⋅ O2 ⋅ ) and nonradical oxidation (1O2) dominated the PNP degradation process. Theoretical calculations corroborated that the anchored atomic Fe and Mn sites regulated the local electronic structure of the catalyst. This modulation effectively promoted the activation of O3 molecules, resulting in the generation of atomic oxygen species (AOS) and reactive oxygen species (ROS). The economic analysis on Mn-Fe/C-Al2O3 revealed that it was a cost-competitive catalyst for HCO. This study not only deepens the understanding on the reaction mechanism of HCO with transition metal/carbon composite catalysts, also provides a high-performance and cost-competitive ozone catalyst for prospective application.

Nano gold catalyst preparation and it’s p-nitrophenol catalytic degradation properties

Abstract Cacumen platyclade extracts were utilized as the reducing agent to prepare Au/Al2O3 composites. XRD, BET, SEM, TEM were employed to characterize the properties of the catalyst. The catalytic activity of Au/Al2O3 was studied by using NaBH4 as the reducing agent and nitrophenol as the pollutant. The results showed that the Au/Al2O3 catalyst, calcinated at 400 °C, exhibited the highest catalytic activity. With a catalyst dosage of 1 g L−1, 2 mL NaBH4 of 0.15 mol L−1 could degrade 96.5 % nitrophenol in 21 min at 298 K, with a reaction constant of 0.16 min−1. Furthermore, the p-nitrophenol degradation ratio decreased by 0.8 % after ten cycles.

Kinetics of continuously catalyzed peroxymonosulfate in a fixed-bed reactor

Most studies have been conducted in batch reactors. Therefore, understanding the catalytic reaction kinetics and mass transfer in continuous catalytic reactors is essential for the design of heterogeneous catalysts and optimisation of catalytic degradation processes in heterogeneous systems. In this research, granular catalysts (Co-600/AlSi-0.25/AP) is used to investigate the kinetic constants and mass transfer resistance for the continuous catalytic decomposition of peroxymonosulfate (PMS) and degradation of p-nitrophenol (PNP) in a fixed bed reactor. The flow rate is 5 mL/min and reaction temperature is 30 °C, intrinsic kinetic constants of PMS decomposition and PNP degradation are 48 and 195 kg−1·min−1·L, respectively, which are 20–30 times of the apparent kinetic constants of PMS decomposition and PNP degradation in fixed bed reactors, respectively. The decomposition rates of PMS and PNP are controlled by mass transfer, and the reaction takes place in the diffusion-controlled regime. The mass transfer kinetic model based on the plug-flow model shows a good agreement between the calculated data and the experimental data. Which indicate that PMS decomposition and pollutant degradation in a fixed-bed reactor can be predicted by mass transfer kinetic modelling, guide the design of catalysts and the optimisation of heterogeneous catalytic reaction system in a fixed-bed reactor.

Effect of MoS2 Morphology on the Photocatalytic Degradation of 4-Nitrophenol to Aminophenol

Nitroaromatic compounds are frequently detected as contaminants in industrial or agricultural wastewaters. Wastewater discharge contributes to nitrophenol pollution of the aquatic environment. Toxicity and carcinogenicity of 4-nitrophenol cause serious impact on water bodies. The present study is devoted to investigates the photocatalytic degradation of p-nitrophenol to aminophenol by MoS2 photocatalyst. MoS2 nanoparticles were synthesized via a hydrothermal process and further characterized by using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), High resolution transmission microscopy (HRTEM), UV-Visible spectroscopy, Brunauer–Emmett–Teller (BET), and X-ray photoelectron spectroscopy (XPS). X-ray analysis revealed the presence of 2H phase of MoS2 and XPS analysis determined its various oxidation states. Fourier Transformation Infra-Red Spectroscopy (FTIR) and Thermogravimetric analyses (TGA) were used to study the functional group and thermal stability. UV-Visible spectroscopy was used to study the degradation of 4-nitrophenol and reaction kinetics. Investigation results showed a significant effect of nanosheets over nanoflower morphology for degradation efficiency of 4 nitrophenol to aminophenol under natural Sunlight.

PH dependence of reactive oxygen species generation and pollutant degradation in Fe(II)/O2/tripolyphosphate system

It has been reported that tripolyphosphate (TPP) can effectively enhance the activation of O2 by Fe(II) to remove organic pollutants in the environment. However, the influence of solution pH on the generation and conversion of reactive oxygen species (ROS) and their degradation of pollutants in the Fe(II)/O2/TPP system needs further investigation. In this study, we demonstrated that O2•– and •OH were the main ROS responsible for degradation in the system at different pH conditions, and their formation rates were calculated using a steady-state model. Experiments combined with density functional theory (DFT) calculations showed that the p-nitrophenol (PNP) degradation pathway in the Fe(II)/O2/TPP system is regulated by solution pH. Specifically, at pH = 3, the existence of Fe(II) in the solution is dominated by [Fe(II)(HTPP)2]2−, which leads to a rapid conversion from O2 and HO2• to generate •OH, and PNP is primarily oxidatively degraded. However, at pH = 5/7, [Fe(II)(TPP)2]4− is taking the lead with which O2•– is accumulated in the solution due to the slow conversion to •OH in this condition, and the PNP is mainly reductively degraded. This study proposes a new strategy to achieve the targeted oxidative/reductive removal of different types of pollutants by simply varying the solution pH in the Fe(II)/O2/TPP system.

Hydrothermally Synthesized TiO2 Nanowires and Potential Application in Catalytic Degradation of p-Nitrophenol

Hydrothermally Synthesized TiO2 Nanowires and Potential Application in Catalytic Degradation of p-Nitrophenol

Microenvironment modulation of biocatalyst derived from natural cellulose of wheat straw for enhancing p-nitrophenol degradation via boosting peroxymonosulfate activation

Defect-rich nitrogen-doped biocatalyst (B-NC) was synthesized from natural cellulose of wheat straw using straightforward mechanical method and one-step pyrolysis approach. In contrast to the nitrogen-doped biocatalyst (NC), by leveraging the synergistic effects of nitrogen dopants and surface defects, the microenvironment-modulated B-NC exhibited the enhanced mass transfer efficiency and a significant improvement in reactivity for p-nitrophenol degradation (111 %–196 %). The catalyst's exceptional performance primarily arose from graphitic N, pyridinic N and CO active sites, which mainly derived from the cellulose structure of wheat straw and nitrogen dopants. Electron paramagnetic resonance and quenching tests confirmed that the B-NC/peroxymonosulfate system generated more reactive species (SO4•−, •OH, O2•−, and 1O2) during p-nitrophenol degradation, surpassing the NC/peroxymonosulfate system. Additionally, both density functional theory calculations and electrochemical experiments provided evidence of peroxymonosulfate strongly adsorbing onto B-NC's defect sites, facilitating the formation of catalyst/peroxymonosulfate* complexes and promoting electron transfer processes. This research provides valuable insights into the regulation of defects in nitrogen-doped biocatalyst derived from natural cellulose, presenting a promising solution for remediating refractory organic pollutants.

Bisulfite enhances p-nitrophenol degradation by zero-valent iron under oxic conditions: Combination of indirect reduction by superoxide radical and direct reduction

Advanced oxidation processes based on the combination of zero-valent iron (ZVI) and S(IV) have been extensively investigated for oxidative degradation of organic pollutants, but little attention has been paid to their reducing capacities in the presence of oxygen. This work found bisulfite (BS) could greatly enhance the degradation of p-nitrophenol (PNP) by ZVI under oxic conditions and PNP was only reduced to p-aminophenol without further degradation. A combination of indirect reduction by superoxide radical (O2•–) and direct reduction by ZVI was verified as the mechanism of PNP degradation. Highly oxidizing species, such as hydroxyl radical (HO•) and sulfate radical (SO4•−), were also produced in the ZVI/BS system under oxic conditions but did not contribute to pollutant degradation perhaps due to the rapid consumption by reducing substances like BS ions and the released Fe2+. BS concentration, ZVI dosage, initial solution pH and coexisting anions (CO32–, PO43– and Cl–) affected the degradation of PNP. ZVI lost the reactivity after used for three times because of the production of goethite and lepidocrocite covered on its surface. This study will provide a new insight into degradation of organic pollutants in ZVI/BS system under oxic conditions.

Insights into performance and mechanism of CuCo2O4/MXene composite as an efficient peroxymonosulfate activator for p-nitrophenol degradation

The slow redox cycle during oxidation and the toxicity risk due to leaching of metal ions greatly hinder the practical application of transition metal-based catalysts in advanced oxidation processes. In this study, a novel layered-structured CuCo2O4/MXene composite was prepared by self-assembling CuCo2O4 spinel with two-dimensional MXene and used as a heterogeneous catalyst based on peroxymonosulfate (PMS) activation for the oxidative degradation of p-nitrophenol (4-NP). Benefiting from its unique structure, the degradation efficiency of 4-NP by CuCo2O4/MXene-activated PMS was close to 100 % within 10 min at the initial pH 7.0. Quenching experiments and electron paramagnetic resonance demonstrated that both radical (SO4•- and •OH) and non-radical (1O2) pathways were involved in the degradation of 4-NP. X-ray photoelectron spectroscopy analysis showed that the introduction of MXene could significantly promote the efficient redox cycling of Cu2+/Cu+ and Co3+/Co2+ on the catalyst surface, thus providing a continuous driving force for the PMS activation. More importantly, CuCo2O4/MXene exhibited good ionic interference resistance, high stability and low metal ion leaching rate, suggesting its potential practical application. This work not only demonstrates that CuCo2O4/MXene is a promising catalyst for the degradation of organic pollutants by PMS activation, but also provides a new idea for the development of efficient PMS-activated catalysts for pollutant degradation.

Phosphate ligand-mediated production of reactive oxygen species during oxygenation of Fe(II)-phosphate complexes

Reactive oxygen species (ROS) production upon the oxygenation of reduced iron minerals is of critical importance to redox cycles of Fe and the fate of refractory organic contaminants. The environmental impact factors during this process, however, have been underappreciated. In this study, prominently enhanced production of hydroxyl radicals (•OH) was observed by oxygenation of Fe(II) with 5–50 mM phosphate. The results of spin trap electron spin resonance (ESR) experiment showed that Fe(II)-phosphate complexes facilitated the generation of •OH. The degradation experiment of p-nitrophenol (PNP) confirmed that •OH formation was dominated by a consecutive one-electron O2 reduction (90.2–96.9 %), and the quantification of PNP degradation products revealed that Fe(II)/phosphate molar ratios regulated the O2 activation pathways for O2•− or •OH production. The further experimental and theoretical investigation demonstrated that the coordination of phosphate with Fe(II) plays a dual role in ROS generation that facilitated O2•− formation by lowering the energy barrier for Fe(II) oxidation and altered the reaction pathway of •OH formation due to its occupation of sites for electron transfer. The present work highlights an important role of natural oxyanions in O2 activation by Fe(II) and raises the possibility of in situ degradation of contaminants in subsurface environment.

Synergistic degradation of p-nitrophenol using peroxymonosulfate activated with a bimetallic Mn3O4–Cu2O catalyst: Investigation of strong interactions between metal oxides

The use of efficient, eco-friendly catalysts is essential for activating peroxymonosulfate (PMS) to degrade organic contaminants in aqueous media. In this study, we developed a novel approach to fabricating bimetallic MnCu catalysts (Mn:Cu molar ratios: 10:1, 5:1, 3:1, and 2:1) comprising tetragonal Mn3O4 and cubic Cu2O. MnCu-5:1 exhibited superior catalytic activity for the degradation of p-nitrophenol (PNP) using PMS because of the synergistic interplay between Mn and Cu. Experimental and density functional theory (DFT) calculation data revealed that the mixed valence states and strong interactions between Mn and Cu in the MnCu-5:1 system increased the electron transfer efficiency and promoted electron transfer to PMS. The results of quenching experiments elucidated a primary radical mechanism and minor nonradical pathway for the PNP degradation over the MnCu-5:1/PMS system. DFT calculations confirmed a relatively high adsorption energy of the Mn3O4–Cu2O (MnCu) composite, indicating enhanced catalytic performance. The superior reactivity of the composite was verified by analyzing its density of states and electrostatic difference potential. Our findings offer fresh perspectives for harnessing the synergistic potential of less toxic mixed metal oxides for controlling catalytic properties and help achieve a better understanding of the activation mechanism for contaminant degradation over MnCu catalysts.

Nanoscale zero-valent iron/biochar composites containing persistent free radicals (PFRs) for degradation of p-nitrophenol.

Despite the vital roles of Fe0/biochar composites in the Fenton-like systems for eliminating pollutants that have been recognized, the contributions of persistent free radicals (PFRs) of carbon-based materials are typically overlooked. In this study, the high-PFR-containing biochar nanoiron composites were prepared (nZVI/500), and the in situ generation of hydroxyl radicals (·OH) and degradation of p-nitrophenol (PNP) were investigated. The results showed that nZVI/500 could effectively remove PNP in solution within the pH range of 3-8. Quantitative experiments of ·OH presented that, compared with low PFRs-containing composites, nZVI/500 could generate 64.6µM ·OH in 60min without any extra energy consumption. Mechanistic studies revealed that (1) both PFRs and Fe0 are able to utilize dissolved oxygen to generate H2O2 in situ; (2) PFRs can promote the cycling of Fe3+/Fe2+ in the system due to their strong electron exchange ability; and (3) PFRs directly transfer electrons to H2O2; therefore, the presence of PFRs accelerates the generation of ·OH in the system and facilitates the removal of PNP. This study provides an important theoretical basis and technical reference for expanding the application of PFR-rich carbon-based materials to remove environmental pollutants.

Efficient degradation of p-nitrophenol from water by enhancing dielectric barrier discharge (DBD) plasma through ozone circulation: Optimization, kinetics and mechanism

Non-thermal dielectric barrier discharge (DBD) plasma has received great attention for degradation of persistent organic pollutants such as p-nitrophenol (PNP). However, the feasibility of the DBD implementation is not clear due to its high energy consumption and relatively low degradation efficiency. In this research, a novel strategy was suggested based on re-circulation of the generated O3 in the DBD system to enhance the PNP degradation efficiency and energy yield. The potential mechanism and possible pathway of PNP degradation were studied by EPR, ESR, DFT and GS-MS analytical tests. According to the results, the PNP degradation efficiency and energy yield increased from 57.4% to 94.4% and from 0.52 to 1.18 g kW−1h−1, respectively through ozone circulation into the DBD reactor. This was due to the more release of long-lived and short-lived reactive species (ROS) in the DBD-O3 system by the O3 circulation. The variations in pH (4–10), initial concentration (50–90 mg L−1), and the presence of co-existing substances in the water matrix had minimal impact on the DBD-O3 system, in comparison to the conventional system. The biological toxicity evaluation revealed that the hybrid DBD-O3 system transform PNP to less toxic intermediates. This study proposes a promising strategy to improve the utilization of DBD for the degradation of PNP.

Facile microwave-assisted synthesis of Sb2O3-CuO nanocomposites for catalytic degradation of p-nitrophenol

Recently, bimetallic nanocomposites have been prepared and used in the fields of sensing, catalysis, energy and medicine. However, there are few reports on the preparation and application of new antimony-metal nanocomposites based on two-dimensional antimonene (AM). Herein, Sb2O3-CuO nanocomposites were facilely synthesized by using microwave-assisted heating the mixture solution of AM and Cu2+ ions and utilized for catalytic degradation of p-nitrophenol (PNP). Interestingly, in the mixed solution of AM and various metal ions (Cu2+, Co2+, Mn2+), only the mixture of AM and Cu2+ ions showed efficient fading and absorption reduction effects on PNP after being heated. A series of characterization on morphology and elemental composition confirmed that the nanocomposites obtained after microwave heating was composed of Sb, Cu, O elements (namely Sb2O3-CuO), and was a layered structure loaded with numerous irregular particles. Compared with other catalysts, the nanocomposite has higher catalytic efficiency (the rate constant of 1.07 s−1), and was capable of degrading 96 % of PNP with only 3 s reaction. Electron spin resonance spectroscopy and liquid chromatography-mass spectrometry analysis demonstrated that the copper-mediated Fenton-like reaction in the nanocomposites induced hydroxyl radicals which can efficiently attack and degrade PNP. This study presents a novel approach to the synthesis of antimony-metal nanocomposites and provides a potential solution for the treatment of organic pollutants.

Rational design of g-C3N4-based photocatalysts with intramolecular donor-acceptor structures for deep oxidation of emerging organic micropollutants

An in-situ route for the fabrication of intramolecular electron donor-acceptor (D-A) structured g-C3N4 photocatalysts is developed by the preorganization of urea with the precursor of electron donor units, such as 4-iodobenzaldehyde, 5-bromo-2-thiophenaldehyde and 5-bromo-2-furaldehyde, followed by thermal polymerization. In the resulting benzene unit-, thiophene unit- and furan unit-based D-A structured g-C3N4 photocatalysts, namely, BHCNx, SCNx, and OCNx, the incorporated electron donor units (i.e., benzene units, thiophene units and furan units) link with the electron acceptors (i.e., heptazine units) through CN and CN covalent bonds. In comparison of bulk g-C3N4, all D-A structured g-C3N4 display notably enhanced visible-light photocatalytic oxidation activity in the degradation of emerging organic micropollutants, p-nitrophenol (PNP) and methylparaben (MPB), in which the apparent first-order kinetic constant of the optimized BHCN2, SCN2, and OCN2 is 1.6, 3.0 and 6.8 times higher than bulk g-C3N4 for PNP degradation and 1.9, 3.4 and 2.6 times higher than bulk g-C3N4 for MPB degradation. Importantly, the micropollutants can be not only degraded but also mineralized completely. The catalysts are also robust in the removal of mixed emerging organic micropollutants in pharmaceutical wastewater, exhibiting potential of dealing with organic micropollutants in wastewater. Mechanism studies reveal that the unique intramolecular charge transfer process in the catalysts enhances visible-light harvesting capacity, boosts directional transfer of the photogenerated charges and increases adsorption towards oxygen molecules. These collective improvements can maximum utilization the photogenerated electrons and holes to yield plentiful reactive oxygen species for deep oxidization of the pollutants.

Enhanced denitrification and p-nitrophenol removal performance via hydrophilic sponge carriers fixed with dual-bacterial: Optimization, performance, and enhancement mechanism

Effective treatment of industrial wastewater containing complex pollutants, such as nitrate (NO3--N) and organic pollutants, remains a significant challenge to date. Here, a strain Nocardioides sp. ZS2 with denitrification and degradation of p-nitrophenol (PNP) was isolated and its culture conditions were optimized by kinetic analysis. Hydrophilic sponge carriers were prepared using polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and chitosan (CS) to construct bioreactors. Furthermore, to further enhance the PNP degradation and denitrification performance of bioreactors, Pseudomonas stutzeri GF2 with denitrification capability was introduced. The results revealed that the removal efficiencies of PNP and NO3--N reached 97.9 % and 91.9 %, respectively, when hydraulic retention time (HRT) of 6 h, C/N of 2.0, and pH of 6.5. The bioreactor exhibited stable denitrification performance even with fluctuations in the influent PNP concentration. The potential functional prediction results revealed that the abundance of amino acids, fatty acids, and carbohydrates increased as the influent C/N decreased, reflecting a tendency of the microbial community to adjust carbon source utilization to maintain cell growth, metabolic balance, and resist adverse C/N environments. This research provides new insights into the effective removal of organic pollutants and NO3--N in wastewater treatment.

Kinetic study of p-nitrophenol degradation with zinc oxide nanoparticles prepared by sol–gel methods

Three zinc oxides (ZnO A, B, C) with similar spherical morphology but different sizes are synthesized by sol–gel methods. A kinetic study is carried out on the photocatalytic activity of these three ZnO, through the degradation of p-nitrophenol (PNP). A mathematical model is developed and the rate constants of the three catalysts are determined. To understand the parameters influencing the kinetics, the catalysts are reduced to the surface of an isolated particle (assuming perfect dispersion conditions where all catalytic active sites are available) whose size is determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). However, by considering the real case (not a perfect dispersion), it appears that the size of the aggregates induced by the synthesis methods play a more important role in the catalytic activity of the three ZnO samples than defects. A discussion on the formation of these aggregates highlights the importance of the synthesis parameters, like the solvent or the surfactant used to obtain a high dispersion. The dispersion plays a crucial role in photocatalytic efficiency, with kinetics three times higher for the catalyst with the best dispersion. Also, as shown by photoluminescence and X-ray photoelectron spectroscopy (XPS), the type and amount of defects play an important role in the photocatalytic performance. ZnO A and B show a defect peak at 620 nm whereas ZnO C shows a defect peak at 680 nm, suggesting a different type of defect on the surface of the catalyst that reduces the photocatalytic performance. Electron paramagnetic resonance (EPR) measurements are performed to identify the type of radicals involved in PNP degradation. The results show that the catalyst with the best dispersion produces the highest amount of hydroxyl radicals. Finally, photoluminescence and XPS analyses underline the type and the amount of defects for the three photocatalysts.

The piezoelectric catalysis effect of tourmalines in the degradation of organic pollutants

The discovery of the piezoelectricity of tourmalines has been reported over three decades, but very few studies exploring the piezoelectric catalysis effect of tourmalines. Herein, the piezoelectric catalysis effect of iron-based and lithium-based tourmalines (Fe-TM and Li-TM) was studied through the degradation of Rhodamine B (RhB) and p-nitrophenol (PNP) in aqueous solution as model reaction in tourmaline/ultrasound system. In ultrasonic condition, the obvious degradation of RhB and PNP was observed and confirmed stemming from the piezoelectric catalysis effect of Fe-TM and Li-TM. Fe-TM was found to have higher surface voltage (560–590 mV) and a higher piezoelectric coefficient of 9.5 pC/N, compared to Li-TM (surface voltage: 410–450 mV; piezoelectric coefficient: 6.7 pC/N). Accordingly, high and stable piezoelectric catalysis activity was observed on Fe-TM in the degradation of RhB and PNP. Through annealing at 800 ℃ in air, Fe-TM can be converted from buergerite tourmaline into foitite tourmaline, and the piezoelectric catalysis activity was basically unchanged. In tourmaline/ultrasound system, the degradation of RhB and PNP was mainly initiated by •OH that be produced from the oxidation of water with the piezoelectric potential of tourmalines. The present work observes and confirms the piezoelectric catalysis effect of tourmalines, which could inspire the new applications and understanding of tourmalines.

Exclusion of the main role of oxygen vacancy in Cu-Mn-O/N-doped carbon catalysts for activating peroxymonosulfate to degrade p-nitrophenol (PNP) and reducing PNP in water by NaBH4

Heterogeneous catalysts based on transition metal oxides are promising for activating peroxymonosulfate (PMS) for the degradation of organic pollutants and oxygen vacancy (VO) is often considered to be important in controlling catalytic performances. Herein, Cu-Mn-O/N-doped carbon catalysts were designed by changing the atomic ratio of Cu: Mn from 5:95 to 33.3:66.7, 50:50, and 95:5, resulting in the formation of VO or copper vacancy (VCu). Unexpectedly, all these catalysts showed excellent catalytic behavior toward the oxidation of p-nitrophenol (PNP) by PMS, indicating that VO is not the main factor in determining the catalytic performance, and the synergistic effect between Cu and Mn species was suggested to be the main factor. The impact of initial pH, catalyst dosage, PMS concentration, the concentration of PNP, and inorganic anions on the removal of PNP were explored. Electron paramagnetic resonance (EPR) tests and radical scavenging experiments revealed that both radicals and non-radicals were involved in the degradation of PNP and single oxygen (1O2) was the main reactive species. The intermediates were detected by using liquid chromatography mass spectrometry (LC-MS) in the degradation process, and a possible degradation mechanism was proposed. The developed catalysts also exhibited outstanding catalytic activities toward reduction reaction of PNP to P-aminophenol (PAP) by NaBH4. These results exclude the consideration of designing high-performance Cu-Mn-O oxide catalysts with oxygen vacancies.

Oxygen vacancy-induced nonradical degradation of nitroso-containing organics in Fe3O4@N[sbnd]C electro-Fenton reaction at a wide pH range

In this work, Fe3O4-anchored nitrogen-doped carbon catalyst (Fe3O4@N–C) with abundant oxygen vacancies (Vo) and mesoporous structure was successfully synthesized for electro-Fenton (EF) catalytic process. The catalyst demonstrated impressive degradation efficiency towards nitroso-containing organics due to the superior electronic transfer of N–C skeleton and Vo, making it easier for the electron-deficient –NO2 groups to adsorb on the catalyst surface and oxidize rapidly. Typically, the degradation efficiency of p-nitrophenol (PNP) reached 95.6 % in natural pH. Notably, the catalyst exhibited excellent performance over a wide pH range (3 ∼ 11), and has strong anti-interference performance against anions and natural organic matter in water matrix. Mechanism analysis indicated that Vo could promote the formation of highly active electron-rich Fe(II) species, and promote the activation of H2O2 and O2 as additional active sites, thus, a large amount of ·OH and O2·- would be produced and then quickly converted into 1O2. As a result, 1O2 is the main reactive species for PNP degradation in Fe3O4@N–C electro-Fenton reaction. The results will provide insights into the design of high-performance catalysts for the selective oxidation of organic pollutants in wastewater.