Peroxide Activation Research Articles

Water hyacinth derived biochar for polycyclic aromatic hydrocarbons removal and oxidative stress study

Polycyclic aromatic hydrocarbons (PAHs), highly concerned emerging contaminant, are priority persistent organic pollutants (POPs) adversely affect the ecological health of marine sediments. These pollutants have attracted widespread attention because of their potential toxicological effects on aquatic organisms and subsequent threats to human health. In this study, an advanced oxidation process for the remediation of PAH-contaminated sediments was developed by the activation of calcium peroxide (CaO2; CP) using a green catalyst prepared from water hyacinth biochar (WHBC), and the associated biochar-driven cellular oxidative stress was highlighted. The catalytic capacity of WHBC was determined at pyrolysis temperature between 300 and 900 °C. WHBC prepared 700 °C (WHBC700) and CP removed 74% of PAHs from the sediment matrix. Results of antioxidant activity evaluation after exposure to WHBC at doses between 400–4000 and 1000–4000 mg L−1 in human hepatocarcinoma cell lines (HepG2) for 24 h showed enhanced glutathione peroxidase (GPx) and catalase (CAT) activities, respectively. Increase in mRNA levels of superoxide dismutase (SOD) genes was also observed after WHBC exposure (400–4000 mg L−1), implying that the oxidative damage caused by reactive oxygen species (ROS) was inhibited by elevating the cellular antioxidant activity. This study attempted to demonstrate an effective waste-to-resource strategy for remediating PAH-polluted sediment in addition to understanding the potential environmental effects of antioxidant activity and gene expression of carbon-based catalysts on HepG2.

Nitrogen and boron co-doped lignin biochar for enhancing calcium peroxide activation toward organic micropollutants decontamination in waste activated sludge and related microbial structure dynamics

This study synthesized dual heteroatom nitrogen and boron-co-doped lignin-based biochar (NB-LGBC) for calcium peroxide (CP) activation to enhance the removal of organic micropollutants (OMPs), namely, 4-nonylphenol (4-NP) from waste activated sludge (WAS). NB-LGBC/CP enhanced 4-NP degradation by arriving at 83 % removal in 12 h. The NB-LGBC/CP system degraded 4-NP via a synergistic interaction (HO•, O2•− radicals, and singlet oxygen) and electron transfer due to the N–B–C bonding configurations. Results of fluorescence excitation-emission matrix (FEEM) analysis revealed significantly increase in biodegradable organics from treated WAS mixture. NB-LGBC/CP treatment enriched alkaliphilic bacterium associated with the predominance of the genus Desulfonatronum within the phylum Proteobacteria in the WAS, which improved the biological treatment capacity of 4-NP. Thus, NB-LGBC in HR-CAOP will be a novel approach for WAS decontamination.

OsGLP3-7 positively regulates rice immune response by activating hydrogen peroxide, jasmonic acid, and phytoalexin metabolic pathways.

Although germin-like proteins (GLPs) have been demonstrated to participate in plant biotic stress responses, their specific functions in rice disease resistance are still largely unknown. Here, we report the identification and characterization of OsGLP3-7, a member of the GLP family in rice. Expression of OsGLP3-7 was significantly induced by pathogen infection, jasmonic acid (JA) treatment, and hydrogen peroxide (H2 O2 ) treatment. OsGLP3-7 was highly expressed in leaves and sublocalized in the cytoplasm. Overexpression of OsGLP3-7 increased plant resistance to leaf blast, panicle blast, and bacterial blight, whereas disease resistance in OsGLP3-7 RNAi silenced plants was remarkably compromised, suggesting this gene is a positive regulator of disease resistance in rice. Further analysis showed that OsGLP3-7 has superoxide dismutase (SOD) activity and can influence the accumulation of H2 O2 in transgenic plants. Many genes involved in JA and phytoalexin biosynthesis were strongly induced, accompanied with elevated levels of JA and phytoalexins in OsGLP3-7-overexpressing plants, while expression of these genes was significantly suppressed and the levels of JA and phytoalexins were reduced in OsGLP3-7 RNAi plants compared with control plants, both before and after pathogen inoculation. Moreover, we showed that OsGLP3-7-dependent phytoalexin accumulation may, at least partially, be attributed to the elevated JA levels observed after pathogen infection. Taken together, our results indicate that OsGLP3-7 positively regulates rice disease resistance by activating JA and phytoalexin metabolic pathways, thus providing novel insights into the disease resistance mechanisms conferred by GLPs in rice.

Revealing Intrinsic Relations Between Cu Scales and Radical/Nonradical Oxidations to Regulate Nucleophilic/Electrophilic Catalysis

AbstractCopper/carbon catalysts under different electron‐transfer regimes can evolve both radical and nonradical pathways in peroxide activation. However, the underlying trigger to manipulate the transition in between is unclear. Herein, it is revealed that Cu species in a state of sub‐nanometre particles (SNPs, < 1 nm) exhibits an electrophilic nature, which is opposite to its nucleophilic nature at a larger scale (nanoclusters, > 1 nm). This switch between nucleophile/electrophile nature leads to distinct catalytic mechanisms in activating peroxymonosulfate, i.e., nonradical 1O2 surface‐bound upon Cu SNPs and unleashed radical •OH induced by Cu nanoclusters. The vacancy defects of biomass‐derived carbon can stabilize Cu SNPs via a CuVC configuration, circumventing the contemporary difficulties in coordinating/preserving MetalNC bonding. Depth profiling, chemical probes, and charge density difference modeling support the regulable electroactive nature over modulated Cu scales. This featured system is applied for tetracycline degradation, and Cu SNPs demonstrates the highest efficacy with their better peroxymonosulfate confinement in nonradical regime (88.9% removal, nucleophilic activation). Comparatively, severe Cu leaching caused by radical erosion (44.8% removal, electron‐donation) is undesirable. Overall, a regulable heterogeneous catalysis is unraveled over carbon‐supported Cu sites through scaling modulation and defect engineering. This study illuminates a promising path for customizing biomass‐derived Cu‐based catalysts to achieve versatile catalysis.

Adsorption of anionic and cationic dyes from aqueous solutions on fly ash-based porous geopolymer

<p>Fly ash, solid waste from coal-fired power plant, had been utilized as raw material for porous geopolymer by alkaline activation and addition of hydrogen peroxide (H2O2) blowing agent. Porous geopolymer had higher surface area and total pore volume compared to fly ash and geopolymer without blowing agent, namely 45.511 m2 g-1 and 0.05131 cc g-1, respectively. Porous geopolymer was applied as adsorbent for anionic dyes Eriochrome Black T (EBT) and cationic dyes Methyl Violet (MV) from aqueous solutions. In this paper, factors affecting adsorption process such as adsorbent dosage, pH, time, and initial concentration were studied, in addition to adsorption kinetics and isotherm studies. Adsorbent dosage, time, and initial concentration factors had the same effect on the adsorption process for both EBT and MV dyes. The optimum removal efficiency was obtained at adsorbent dosage of 2 g L-1 and adsorption time of 90 minutes. The increase of the initial concentration of dyes would decrease the removal efficiency. For pH factor, adsorption of EBT dyes was better at pH of 2, while adsorption of MV dyes was better at pH of 10. Both adsorption of EBT and MV dyes by porous geopolymer followed pseudo-second-order kinetics model and Langmuir isotherm model with maximum adsorption capacity of 45.454 mg g-1 and 49.261 mg g-1, respectively.</p>

Single atom catalyst-mediated generation of reactive species in water treatment.

Water is one of the most essential components in the sustainable development goals (SDGs) of the United Nations. With worsening global water scarcity, especially in some developing countries, water reuse is gaining increasing acceptance. A key challenge in water treatment by conventional treatment processes is the difficulty of treating low concentrations of pollutants (micromolar to nanomolar) in the presence of much higher levels of inorganic ions and natural organic matter (NOM) in water (or real water matrices). Advanced oxidation processes (AOPs) have emerged as an attractive treatment technology that generates reactive species with high redox potentials (E0) (e.g., hydroxyl radical (HO˙), singlet oxygen (1O2), sulfate radical (SO4˙-), and high-valent metals like iron(IV) (Fe(IV)), copper(III) (Cu(III)), and cobalt(IV) (Co(IV))). The use of single atom catalysts (SACs) in AOPs and water treatment technologies has appeared only recently. This review introduces the application of SACs in the activation of hydrogen peroxide and persulfate to produce reactive species in treatment processes. A significant part of the review is devoted to the mechanistic aspects of traditional AOPs and their comparison with those triggered by SACs. The radical species, SO4˙- and HO˙, which are produced in both traditional and SACs-activated AOPs, have higher redox potentials than non-radical species, 1O2 and high-valent metal species. However, SO4˙- and HO˙ radicals are non-selective and easily affected by components of water while non-radicals resist the impact of such constituents in water. Significantly, SACs with varying coordination environments and structures can be tuned to exclusively generate non-radical species to treat water with a complex matrix. Almost no influence of chloride, carbonate, phosphate, and NOM was observed on the performance of SACs in treating pollutants in water when nonradical species dominate. Therefore, the appropriately designed SACs represent game-changers in purifying water vs. AOPs with high efficiency and minimal interference from constituents of polluted water to meet the goals of water sustainability.

Reaction landscape of a mononuclear MnIII-hydroxo complex with hydrogen peroxide.

Peroxomanganese species have been proposed as key intermediates in the catalytic cycles of both manganese enzymes and synthetic catalysts. However, many of these intermediates have yet to be observed. Here, we report the formation of a series of intermediates, each generated from the reaction of the mononuclear MnIII-hydroxo complex [MnIII(OH)(dpaq2Me)]+ with hydrogen peroxide under slightly different conditions. By changing the acidity of the reaction mixture and/or the quantity of hydrogen peroxide added, we are able to control which intermediate forms. Using a combination of electronic absorption, 1H NMR, EPR, and X-ray absorption spectroscopies, as well as density functional theory (DFT) and complete active space self-consistent field (CASSCF) calculations, we formulate these intermediates as the bis(μ-oxo)dimanganese(III,IV) complex [MnIIIMnIV(μ-O)2(dpaq2Me)2]+, the MnIII-hydroperoxo complex [MnIII(OOH)(dpaq2Me)]+, and the MnIII-peroxo complex [MnIII(O2)(dpaq2Me)]. The formation of the MnIII-hydroperoxo species from the reaction of a MnIII-hydroxo complex with hydrogen peroxide mimics an elementary reaction proposed for many synthetic manganese catalysts that activate hydrogen peroxide.

Heterogeneous activation of peroxide via acid-modified red mud for the degradation of phenol

Heterogeneous activation of peroxide via acid-modified red mud for the degradation of phenol

Electronic structure contributions to O-O bond cleavage reactions for MnIII-alkylperoxo complexes.

Synthetic manganese catalysts that activate hydrogen peroxide perform a variety of hydrocarbon oxidation reactions. The most commonly proposed mechanism for these catalysts involves the generation of a manganese(III)-hydroperoxo intermediate that decays via heterolytic O-O bond cleavage to generate a Mn(V)-oxo species that initiates substrate oxidation. Due to the paucity of well-defined MnIII-hydroperoxo complexes, MnIII-alkylperoxo complexes are often employed to understand the factors that affect the O-O cleavage reaction. Herein, we examine the decay pathways of the MnIII-alkylperoxo complexes [MnIII(OOtBu)(6Medpaq)]+ and [MnIII(OOtBu)(N4S)]+, which have distinct coordination environments (N5- and N4S-, respectively). Through the use of density functional theory (DFT) calculations and comparisons with published experimental data, we are able to rationalize the differences in the decay pathways of these complexes. For the [MnIII(OOtBu)(N4S)]+ system, O-O homolysis proceeds via a two-state mechanism that involves a crossing from the quintet reactant to a triplet state. A high energy singlet state discourages O-O heterolysis for this complex. In contrast, while quintet-triplet crossing is unfavorable for [MnIII(OOtBu)(6Medpaq)]+, a relatively low-energy single state accounts for the observation of both O-O homolysis and heterolysis products for this complex. The origins of these differences in decay pathways are linked to variations in the electronic structures of the MnIII-alkylperoxo complexes.

Catalytic Activation of Hydrogen Peroxide Using Highly Porous Hydrothermally Modified Manganese Catalysts for Removal of Azithromycin Antibiotic from Aqueous Solution

Hydrogen peroxide catalytic activation holds great promise in the treatment of persistent pollutants. In this study, the novel Mn-Acacair/Al, Mn-Acacarg/Al and Mn-BTCarg/Al catalysts, supported on Al2O3, were applied for rapid hydrogen peroxide activation and azithromycin antibiotic removal. The catalysts were prepared by the calcination-hydrothermal method under air or argon atmosphere. The characterization confirmed that the modification of manganese with acetylacetonate and benzene-1,3,5-tricarboxylic acid (H3BTC) O-donor ligands highly improves the catalyst porosity, amorphousity, and abundance of coordinately unsaturated sites, which facilitate the generation of reactive oxygen species. The hydrogen peroxide activation and azithromycin removal reached 98.4% and 99.3% after 40 min using the Mn-BTCarg/Al catalyst with incredible stability and reusability. Only a 5.2% decrease in activity and less than 2% manganese releasing in solutions were detected after five regeneration cycles under the optimum operating conditions. The removal intermediates were identified by LC-MS/MS analysis, and the pathways were proposed. The hydroxylation and decarboxylation reactions play a key role in the degradation reaction.

Ice-templated synthesis of tungsten oxide nanosheets and their application in arsenite oxidation

Tungsten oxide (WO3) nanosheets were prepared as catalysts to activate hydrogen peroxide (H2O2) in arsenite (As(III)) oxidation. Ice particles were employed as templates to synthesize the WO3 nanosheets, enabling easy template removal via melting. Transmission electron microscopy and atomic force microscopy revealed that the obtained WO3 nanosheets were plate-like, with lateral sizes ranging from dozens of nanometers to hundreds of nanometers and thicknesses of <10 nm. Compared to that of the WO3 nanoparticle/H2O2 system, a higher efficiency of As(III) oxidation was observed in the WO3 nanosheet/H2O2 system. Electron spin resonance spectroscopy, radical quenching studies, and As(III) oxidation experiments under anoxic conditions suggested that the hydroperoxyl radical (HO2●) acted as the primary oxidant. The WO3 nanosheets possessed numerous surface hydroxyl groups and electrophilic metal centers, enhancing the production of HO2● via H2O2 activation. Various anions commonly present in As(III)-contaminated water exhibited little effect on As(III) oxidation in the WO3 nanosheet/H2O2 system. The high oxidation efficiency was maintained by adding H2O2 when it was depleted, suggesting that the catalytic activity of the WO3 nanosheets did not deteriorate after multiple catalytic cycles.

Degradation of petroleum pollutants in oil-based drilling cuttings using an Fe2+-based Fenton-like advanced oxidation processes.

Oil-based drilling cuttings (OBDC) contain a large amount of total petroleum hydrocarbon (TPH) pollutants, which are hazardous to the environment. In this study, Fe2+-activating hydrogen peroxide (Fe2+/H2O2), peroxymonosulfate (Fe2+/PMS), and peroxydisulfate (Fe2+/PDS) advanced oxidation processes (AOPs) were used to treat OBDC due to the difference in the degradation capacity of TPH caused by the type of free radical generated and effective activation conditions observed for the different oxidants studied. The results showed that the oxidant concentration, Fe2+ dosage, and reaction time in the three AOPs were greatly positively correlated with the TPH removal rate in a certain range. The initial pH value had a significant effect on the Fe2+/H2O2 process, and its TPH removal rate was negatively correlated in the pH range from 3 to 11. However, the Fe2+/PMS and Fe2+/PDS processes only displayed lower TPH removal rates under neutral conditions and tolerated a wider range of pH conditions. The optimal TPH removal rates observed for the Fe2+/H2O2, Fe2+/PMS, and Fe2+/PDS processes were 45.04%, 42.75%, and 44.95%, respectively. Fourier transform infrared spectrometer and gas chromatography-mass spectrometer analysis showed that the alkanes in OBDC could be effectively removed using the three processes studied, and their degradation ability toward straight-chain alkanes was in the order of Fe2+/PMS > Fe2+/PDS > Fe2+/H2O2, among which Fe2+/PMS exhibited the optimal removal effect for aromatic hydrocarbons. Scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction results showed no significant changes in the elemental and mineral composition of OBDC before and after treatment. Therefore, this study provided a theoretical reference for the effective degradation of TPH pollutants in OBDC.

The Baeyer–Villiger Oxidation of Cycloketones Using Hydrogen Peroxide as an Oxidant

Baeyer–Villiger oxidation can synthesize a series of esters or lactones that have essential application value but are difficult to be synthesized by other methods. Cycloketones can be oxidized to lactones using molecular oxygen, peroxy acids, or hydrogen peroxide as an oxidant. Hydrogen peroxide is one of the environmental oxidants. Because of the weak oxidation ability of hydrogen peroxide, Bronsted acids and Lewis acids are used as catalysts to activate hydrogen peroxide or the carbonyl of ketones to increase the nucleophilic performance of hydrogen peroxide. The catalytic mechanisms of Bronsted acids and Lewis acids differ in the Baeyer–Villiger oxidation of cyclohexanone with an aqueous solution of hydrogen peroxide as an oxidant.

N-Doped TiO2 Coupled with Manganese-Substituted Phosphomolybdic Acid Composites As Efficient Photocatalysis-Fenton Catalysts for the Degradation of Rhodamine B.

The effectiveness of photocatalytic and Fenton reactions in the synergistic treatment of water pollution problems has become indisputable. In this paper, nitrogen-doped TiO2 was selected as the catalyst for the photocatalytic reaction and manganese-substituted phosphomolybdic acid was used as the Fenton reagent, the two of which were combined together by acid impregnation to construct a binary photocatalysis-Fenton composite catalyst. The degradation experiments of the composite catalyst on RhB indicated that under UV-vis irradiation, the composite catalyst could degrade RhB almost completely within 8 min, and the degradation rate was 19.7 times higher than that of N-TiO2, exhibiting a superior degradation ability. Simultaneously, a series of characterization methods were employed to analyze the structure, morphology, and optical properties of the catalysts. The results demonstrated that the nitrogen doping not only expanded the photo response range of TiO2 but reduced the work function of TiO2, which facilitated the transfer of electrons to the loaded Mn-HPMo side and further promoted the electron-hole separation efficiency. In addition, the introduction of Mn-HPMo provided three pathways for the activation of hydrogen peroxide, which enhanced the degradation activity. This study provides novel insights into the construction of binary and efficient catalysts with multiple hydroxyl radical generation pathways.

Magnetic biochar pyrolyzed from municipal sludge for Fenton-like degradation of thiamethoxam: Characteristics and mechanism

Pesticide pollution is an arduous challenge encountered in the field of industrial wastewater treatment. As a Fenton-like metal catalyst, multifunctional biochar has attracted more and more attention in the dissolution of insoluble organic chemical pollutants. In this study, the magnetic municipal sludge biochars(MSDBC)were synthesized by one-step pyrolysis of sludge from sewage treatment plant. The biochars prepared at different temperatures have great differences in surface functional groups and composition of iron phase. MSDBC prepared at 400 °C has a better catalytic oxidation capacity, while MSDBC prepared at 800 °C has a stronger adsorption capacity. The reason is that the morphology and iron phase composition distribution of biochar are different. More pore structures were formed on the surface of biochar prepared at 800 °C, which not only has better adsorption performance, but also makes the impregnated Fe3+ enter the interior of biochar and transform during pyrolysis. However, the iron phase of MSDBC prepared at 400 °C is mostly located on the surface and the content of Fe2+ is higher. Notably, iron compounds embedded in the magnetic biochar have been proved to be the main catalysts for activating hydrogen peroxide (H2O2) to produce hydroxyl radicals (·OH). Radical quenching experiment and electron paramagnetic resonance (EPR) detection confirmed the production of ·OH and its important role in the oxidative degradation of thiamethoxam (THX). In the THX degradation, MSDBC/H2O2 Fenton-like system showed excellent effect at neutral pH environment. Finally, the innovative use of MSDBC/H2O2 Fenton-like technology in the degradation of complex actual wastewater showed good practicability and stability. This research provides a new idea for the treatment of pesticide wastewater.

Transition metal phosphides for heterogeneous Fenton-like oxidation of contaminants in water

• Transition metal phosphides (MPs) are attractive heterogeneous Fenton-like catalysts. • Metalloid structure and superior conductivity of MPs favor interfacial catalysis. • Metal redox cycling are accelerated by electron supply from reductive phosphide. • Electron- and photo-Fenton processes assist Fenton-like oxidation of pollutants. The development of low cost, efficient materials for heterogeneous Fenton-like catalysis continues to be an active area of research for water treatment. Over the past few years, transition metal phosphides (MPs) have witnessed rapid development and their application fields are rapidly expanding from photocatalytic water splitting to advanced oxidation. The unique metalloid structure and superior electron conductivity of these materials endow them with significantly raised catalytic activity for interfacial reactions relative to their corresponding oxyhydroxides, although the existing studies are still at laboratory scale and the insufficient mechanical study and material engineering are still key barriers to practical application. In this review, we summarize the progress in MPs-based heterogenous Fenton-like processes by introducing the fundamentals and catalytic performances of various MPs for activation of hydrogen peroxide, persulfate or dioxygen, both under normal and electro-assisted or photo-assisted scenarios. In addition, we discuss the remaining challenges for their practical water treatment application and offer perspectives on possible future research directions.

Oxidative removal of oxytetracycline by UV-C/hydrogen peroxide and UV-C/peroxymonosulfate: Process optimization, kinetics, influence of co-existing ions, and quenching experiments

Oxytetracycline (OTC) is a tetracycline group antibiotic with high environmental pollution potential and is resistant to conventional treatment processes. This study provides an environmentally friendly and efficient OTC treatment by ultraviolet (UV)-based advanced oxidation processes. UV irradiation was used for the activation of hydrogen peroxide (HP) and peroxymonosulfate (PMS). In the first stage of the study, control experiments were conducted and the effect of initial pH on the UV/HP and UV/PMS in OTC removal was evaluated. In the following part, variables of the UV/HP and UV/PMS were optimized by the Box-Behnken design. The optimum conditions of the UV/HP process were as follows: 6.5 mg/L initial OTC concentration, 3.50 mM HP dose, and 45.4 min reaction time. The optimum parameters of the UV/PMS process were: 5 mg/L initial OTC concentration, 3.69 mM PMS dose, and 42.75 min reaction time. 72.8 % and 50.96 % OTC removal efficiency were achieved with the validation experiments by the UV/PMS and UV/HP processes, respectively. Kinetic studies showed that Cl− and HCO3− ions have a positive effect whereas SO42− has a negligible effect on the reaction rate of both processes. NO3− has a positive effect on the UV/HP process and a negligible effect on the UV/PMS process. According to the radical scavenging experiments, hydroxyl radicals were dominant in the UV/HP process while in the UV/PMS process both hydroxyl and sulfate radicals were involved. Both processes were effective in OTC removal; however, the UV/PMS process is more efficient and cost-effective.

Axial nitrogen-coordination engineering over Fe-Nx active species for enhancing Fenton-like reaction performance

Activating hydrogen peroxide (H2O2) to produce hydroxyl radical (•OH) (Fenton-like process) is of great importance in heterogeneous catalytic oxidations. However, most of transition metal nano-catalysts as well as recently reported carbon supported Fe-N4 single atom catalysts (SACs) suffer from unsatisfactory catalytic performance. Herein, a novel Fe1/C3N4 SAC with Fe-N5 active site was constructed. Using this SAC, the electron/structure-symmetry of Fe-N4 site can be broken by axial nitrogen-coordination, which transforms less active Fe-N4 species into highly active Fe-N5 species in Fenton-like reaction. Specifically, Fe-N5 site exhibits an unprecedented activity for 3,3′,5,5′-tetramethylbenzidine oxidation, which is at least one order of magnitude more active than reported Fe-N4/C SACs. Mechanism studies reveal that the unique role of axial nitrogen-coordination over Fe-Nx sites is to change the adsorption behavior of H2O over Fe-N5 site without influencing H2O2 activation. This discovery provides a new approach for rationally designing efficient catalysts in Fenton-like reactions.

Rotating ring-disk electrode method to evaluate performance of electrocatalysts in hydrogen peroxide activation via rapid detection of hydroxyl radicals

One-electron electrochemical reduction of hydrogen peroxide (H2O2) is an effective way to produce hydroxyl radical (•OH), whose yield is greatly dependent on the performance (activity and selectivity) of electrocatalysts. However, the current method to evaluate the performance of electrocatalysts is limited by time-consuming and less sensitive method of •OH detection. Herein, we propose an online rotating ring disk electrode (RRDE) method to evaluate the performance of electrocatalysts in H2O2 activation by rapidly detecting •OH. This method is implemented by determining the current signals on the disk and ring electrodes: the generated •OH from H2O2 reduction on the disk electrode (induce negative disk currents) reacts with H2O2 to produce superoxide radical (O2•−), which migrates to and is oxidized on the ring electrode and generates positive ring currents. The relevance of the ring currents to O2•− and •OH is proved by radical quenching tests and kinetic analysis. The performance of five electrocatalysts were evaluated by both the RRDE method and the terephthalic acid (TPA) fluorescence method, and the consistent results verify the applicability of the RRDE method. Hence, this work facilitates the development of high-performance electrocatalysts for H2O2 activation and bring insights for RRDE-based electroanalytic chemistry.

Oxidative Desulfurization of Real High-Sulfur Diesel Using Dicarboxylic Acid/H2O2 System

From the perspective of pollution, economics, and product quality, it is very important to find an efficient way to minimize the sulfur content of petroleum products such as gasoline and diesel. In this work, an effective, inexpensive, and simple oxidative desulfurization system based on hydrogen peroxide activation by three dicarboxylic acids which have different carbon numbers (i.e., malonic acid, succinic acid, and glutaric acid) was utilized for the desulfurization of a real diesel sample with high organic sulfur-containing compounds. The desulfurization process was based on the oxidation of sulfur compounds in diesel fuel to the corresponding sulfones followed by acetonitrile extraction of the sulfones. To select the optimal experimental conditions, the effects of several parameters, including temperature, catalyst H2O2 dosages, and treatment time, were investigated. The results showed that the developed system was effective in desulfurizing real diesel fuel with high sulfur content. With an initial total sulfur content of about 8104 mg/L, the desulfurization rate from the diesel sample reached more than 90.9, 88.9, and 93%, using malonic acid, succinic acid, and glutaric acid, respectively. The optimum parameters such as reaction temperature, reaction time, H2O2 (50 w/w%), and carboxylic acid dosage for oxidative desulfurization were determined to be 95 °C, 6 h, 10 mL, and 0.6 g, respectively. The conversion of refractory sulfur compounds into extractable sulfone forms was verified using gas chromatography. Moreover, the kinetic study confirmed that the designed reaction system follows the pseudo-first-order kinetic model.