Hydroxy Radical Research Articles

Buffered Hydroxyl Radical for Photocatalytic Non‐Oxidative Methane Coupling

Hydroxy radical (•OH) is a prestigious oxidant that allows the cleavage of strong chemical bonds of methane but is untamed, leading to over‐oxidation of methane and waste of oxidants, especially at high methane conversion. Here, we managed to buffer •OH in an aqueous solution of photo‐irradiated Fe3+, where •OH almost participates in methane oxidation. Due to the interaction between Fe3+ and SO42−, the electron transfer from OH− to excited‐state Fe3+ for •OH generation is retarded, while excessive •OH is consumed by generated Fe2+ to restore Fe3+. When combined with a Ru/SrTiO3:Rh photocatalyst, the buffered •OH converts methane to C2+ hydrocarbons and H2 with formation rates of 246 and 418 μmol h−1, respectively. The apparent quantum efficiency reaches 13.0 ± 0.2%, along with 10.2% methane conversion and 81% C2+ selectivity after 80 hours of reaction. Overall, this work presents a strategy for controlling active radicals for selective and efficient photocatalysis.

Buffered Hydroxyl Radical for Photocatalytic Non-Oxidative Methane Coupling.

Hydroxy radical (•OH) is a prestigious oxidant that allows the cleavage of strong chemical bonds of methane but is untamed, leading to over-oxidation of methane and waste of oxidants, especially at high methane conversion. Here, we managed to buffer •OH in an aqueous solution of photo-irradiated Fe3+, where •OH almost participates in methane oxidation. Due to the interaction between Fe3+ and SO42-, the electron transfer from OH- to excited-state Fe3+ for •OH generation is retarded, while excessive •OH is consumed by generated Fe2+ to restore Fe3+. When combined with a Ru/SrTiO3:Rh photocatalyst, the buffered •OH converts methane to C2+ hydrocarbons and H2 with formation rates of 246 and 418 μmol h-1, respectively. The apparent quantum efficiency reaches 13.0 ± 0.2%, along with 10.2% methane conversion and 81% C2+ selectivity after 80 hours of reaction. Overall, this work presents a strategy for controlling active radicals for selective and efficient photocatalysis.

A Preliminary Investigation of Thermally Stable Schiff Base Metal Complexes for Hyperthermia: Synthesis and Biological Evaluation.

A novel Schiff base ligand (L), bearing N2O2 donor sites, was derived from the condensation of 5-chloromethylisophthaldehyde and phenylpropanolamine (PPA). Mononuclear Co(II), Cu(II), and Zn(II) complexes were synthesized and were characterized by FTIR, UV-Vis, 1H NMR, ESI-mass spectroscopy, molar conductance, and thermal and electrochemical studies. The thermal investigation revealed that the complexes were stable up to 150-250 °C and began to degrade in stages, resulting in the development of respective metal oxides. The Coats-Redfern integration method was used to calculate the kinetic and thermodynamic parameters, the energy of activation (Ea), and changes in enthalpy (∆H), entropy (∆S), and free energy (∆G) for each step of the degradation processes. For stage I decomposition, the calculated activation energy values of the complexes follow the order of Ea [Cu(L)] > Ea [Co(L)(H2O)2] > Ea [Zn(L)]. The influence of the temperature on the efficacy of antioxidant activities of the complexes with DPPH assay, ABTS assay, and hydroxy radical assay was investigated at various concentrations using ascorbic acid (AA) as the reference. Antioxidant activity was assessed at multiple temperatures to ascertain whether these complexes may be applied in radiation therapy enhanced with hyperthermia and found to be stable. Subsequently, the Cu(II) complex (C2) demonstrated a greater cytotoxicity (IC50 = 5.16 µM) than Co(II), Zn(II), and conventional cisplatin when in vitro cytotoxicity was evaluated against the MCF-7 cell line using the MTT method. Analyses of the thermal stability and ROS scavenging ability of complexes have demonstrated that these complexes have potential in hyperthermic radiation therapy.

Degradation of Cylindrospermopsin Spiked in Natural Water (Paranoá Lake, Brasília, Brazil) by Fenton Process: A Bench-Scale Study.

The frequency and intensity of harmful cyanobacterial blooms have increased in the last decades, posing a risk to public health since conventional water treatments do not effectively remove extracellular cyanotoxins. Consequently, advanced technologies such as the Fenton process are required to ensure water safety. The cyanotoxin cylindrospermopsin (CYN) demands special attention, as it is abundant in the extracellular fraction and has a high toxicological potential. Hence, this study aimed to assess the application of the Fenton process for the oxidation of CYN spiked in natural water from Paranoá Lake (Brasília, Brazil). The H2O2/Fe(II) molar ratio was evaluated from 0.2 to 3.4, with an optimum molar ratio of 0.4, achieving a CYN degradation efficiency of 97.8% when using 100 µM of H2O2 and 250 µM of Fe(II). The CYN degradation efficiency, using 75 µM of H2O2 and 187.5 µM of Fe(II), decreased by increasing the initial pH (from 96.2% at pH 2 to 23.0% at pH 9) and the initial CYN concentration (from 93.7% at 0.05 µM of CYN to 85.0% at 0.2 µM of CYN). At the optimum H2O2/Fe(II) molar ratio of 0.4, the hydroxy radical scavengers tested (124.3 µM C of algogenic organic matter, 5 mg L-1 of humic acid, and 513.3 µM of methanol) did not considerably affect the CYN degradation, reaching a maximum CYN degradation reduction from 98.3% to 82.2%.

Enhanced H2S removal efficiency using CuO/Al2O3 catalyst impregnated with Ca(NO3)2: Influence of calcination temperature and mechanistic insights

A series of Ca(NO3)2-CuxO/Al2O3 catalysts with different calcination temperatures were designed to remove H2S effectively. Experimental and characterization results indicate that the calcination temperature can influence the catalyst's specific surface area, basic sites, and oxygen vacancies (VOs) concentration, thereby promoting its desulfurization performance. The Ca(NO3)2-CuxO/Al2O3 catalyst, calcined at 230 °C, exhibits an optimal surface structure. It demonstrates optimal H2S desulfurization performance at a temperature of 60 °C and relative humidity of 60 %, achieving a removal capacity of 486.67 mg/g. The VOs in CuxO (CuO and Cu2O) induce a unique catalytic of H2O, which generates hydroxy radicals (·OH) to oxidize the H2S anion to S. The introduction of Ca2+ provides basic sites to buffer pH, and NO3- with H+ removes H2S through cyclic oxidation, significantly enhancing the desulfurization performance of the Cu-based catalyst. The CaO-CuxO/Al2O3 catalyst, calcined at 700 °C, suffers from a deteriorated catalyst structure, leading to the rapid formation of desulfurization by-products due to the presence of CaO covering the catalyst surface. This diminishes the effectiveness of Cu, significantly impairing the catalyst's desulfurization performance (150.47 mg/g). Consequently, desulfurization mechanisms of Ca(NO3)2-CuxO/Al2O3 and CaO-CuxO/Al2O3 are proposed, offering effective strategies for the design and optimization of subsequent high-efficiency catalysts.

Development of miniaturized fluorometric system for the detection of 4-hydroxybenzoic acid and benzoic acid in skincare products based on peroxidase-like catalysts

4-Hydroxybenzoic acid (PHBA) and benzoic acid are common preservatives in many skincare products. However, their excessive, long-term consumption can adversely affect internal and external organs. Herein, a small-volume fluorometric analysis method for preservatives, using PHBA and benzoic acid as model targets, was developed for the first time using Ni-MnFe-layered double hydroxides (Ni-MnFe-LDHs) as peroxidase-like mimics. Based on the intrinsic peroxidase-like activity of Ni-MnFe-LDHs, in the presence of preservatives, the generated hydroxy radical (•OH) from H2O2 decomposition was then consumed by PHBA or benzoic acid to form phenoxy radical, resulting in less •OH to oxidize o-phenylenediamine (OPD). On the other hand, in the absence of PHBA or benzoic acid, Ni-MnFe-LDHs and generated •OH could effectively catalyze OPD into the yellow-fluorescent product 2, 3-diamino phenazine. The fluorescence change of the solution captured by a smartphone under a UV-controlled lightbox was inversely related to preservative concentration. The detection platform was miniaturized using a 96-well plate. Under optimal conditions, with a total volume of only 100 µL, the developed sensing platform can quantitatively detect PHBA and benzoic acid in the concentration ranges of 0.008–1.0, with a limit of detections of 0.0011 and 0.0036 mmol L−1 for PHBA, and 0.0011 and 0.0040 mmol L−1 for benzoic acid, respectively. Our proposed method was successfully validated by quantitatively analyzing the residual preservatives in skincare samples, and the results showed agreement with those obtained using high-performance liquid chromatography.

Ferroptosis Inducing Co(III) Polypyridine Sulfasalazine Complex for Therapeutically Enhanced Anticancer Therapy.

Despite significant improvements in the treatment of cancerous tumors in the last decades, cancer remains one of the deadliest diseases worldwide. To overcome the shortcomings of currently applied chemotherapeutic treatments, much research efforts have been devoted towards the development of ferroptosis inducing anticancer agents. Ferroptosis is a newly described form of regulated, non-apoptotic cell death that is associated with high potential inside the clinics. Herein, the chemical synthesis and biological evaluation of a Co(III) polypyridine sulfasalazine as a ferroptosis inducer is reported. Upon entering the cancerous cells, the metal complex primarily accumulated in the mitochondria, triggering the production of hydroxy radicals and lipid peroxides, ultimately causing cell death by ferroptosis. The compound demonstrated to eradicate various monolayer cancer cells as well as colon carcinoma multicellular tumor spheroids. To the best of our knowledge this study reports on the first example of a Co(III) complex that is capable of inducing ferroptosis.

Acceleration of Diffusion in Ab Initio Nanoreactor Molecular Dynamics and Application to Hydrogen Sulfide Oxidation.

The computational description of chemical reactivity can become extremely complex when multiple different reaction products and intermediates come into play, forming a chemical reaction network. Therefore, computational methods for the automated construction of chemical reaction networks have been developed in the last decades. One of these methods, ab initio nanoreactor molecular dynamics (NMD), is based on external forces enhancing reactivity by e.g., periodically compressing the system and allowing it to relax. However, during the relaxation process, a significant simulation time is required to allow energy to dissipate and molecules to diffuse, making this part of the NMD simulation computationally intensive. This work aims to improve NMD by accelerating the diffusion process in the relaxation phase. We systematically investigate the speedup of reaction discovery gained by diffusion acceleration, leading to a factor of up to 28 in discovery frequency. Diffusion-accelerated nanoreactor molecular dynamics (DA-NMD) is then used to construct a reaction network of hydrogen sulfide oxidation under atmospheric conditions, where reactions are automatically detected by a change in the bond order and bond distance. A reaction network of 108 molecular species and 399 elementary reactions was constructed starting from hydrogen sulfide, hydroxy radicals, and molecular oxygen covering a broad variety of sulfur-oxygen chemistry and oxidation states of the sulfur atom ranging from -II to +VI.

Optimization of the Process of Extracting Polysaccharides from Agrocybe aegerita and In Vitro Antioxidant and Anti-Aging Tests.

The extraction process of crude polysaccharides from Agrocybe aegerita was optimized, and the antioxidant and anti-aging effects of the crude polysaccharides were evaluated. The optimal extraction parameters for the polysaccharide were identified using the response surface methodology. The DPPH, hydroxy radical, and superoxide anion radical scavenging capacities were evaluated to determine the antioxidant properties of the AAPs. The effects of the AAPs on the lifespan, head-swing frequency, swallowing frequency, body-bending frequency, and stress resistance of Caenorhabditis elegans were determined. The optimal extraction conditions included a solid-to-liquid ratio that resulted in an extraction solution concentration of 0.034 g/mL, an extraction temperature of 92.64 °C, and an extraction time of 2.82 h. Under these conditions, the yield of the AAPs was 11.325% ± 0.996%. The IC50 of the AAPs for superoxide anion radical scavenging was 4.693 mg/mL. The AAPs reached their maximum activity at concentrations of about 2 mg/mL for DPPH and 5 mg/mL for the hydroxyl radical. The AAPs could prolong the lifespan and improve locomotion and the stress resistance of C. elegans. Our findings illustrate the potential of AAPs as an anti-aging and antioxidant agent, highlighting the use of this natural compound in the fields of food and pharmacology.

Construction of Visible light Driven Z-Scheme 1D/1D p-CuBi2O4/n-CdWO4 Heterojunction Nanocomposite for Effective Degradation of Organic Pollutants

The effective separation and harnessing of photoinduced charge carriers in photocatalysis are significant challenges. The present study aims to overcome this obstacle by developing a Z-scheme heterojunction between a p-type CuBi2O4 (CBO) and a n-type CdWO4 (CWO) through a straightforward heat treatment method. The powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM) results revealed the successful formation of heterostructures. The photocatalytic efficiency of the materials was assessed by selecting an anionic methyl orange (MO) and cationic Rhodamine-B (Rh–B) dyes under visible light irradiation. Among all the materials, 85 wt% CBO + 15 wt% CWO (CBO/CWO-15) heterostructure exhibited superior photocatalytic activity (90 %) corresponding to 90 and 45 times higher than the pristine CBO and CWO, respectively. The positively charged photocatalyst surface attracts a greater number of MO dye molecules than Rh–B, thereby enhancing the degradation of MO over Rh–B. The scavenger results confirmed the involvement of hydroxy (OH•) and superoxide (O2−•) radicals in the degradation of MO. The rate constant of CBO/CWO-15 (0.01061 min−1) was 64 and 39 times higher than those of CBO (0.00016 min−1) and CWO (0.00027 min−1), respectively. The photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) analyses substantiated the improved charge separation in the CBO/CWO-15 composite, establishing the Z-scheme mechanism. Cycling experiments over four cycles demonstrated consistent stability of the CBO/CWO-15 composite. The study provides an in-detail plausible mechanism of MO degradation. This type of Z-scheme composite material has potential applications in environmental remediation for the effective removal of organic pollutants and antibiotics from wastewater.

Introducing oxygen cacancies to tune Cu2O by Sn ion-doped for high-effective photocatalytic degradation of norfloxacin in wastewater

Photocatalytic materials have attracted considerable attention owing to its positive environmental impact and efficiency in wastewater treatment. Herein, tin (Sn)-doped copper oxide (Cu2O) photocatalysts were successfully synthesized via a facile hydrothermal approach. The doping of Sn ions into the Cu2O lattice promoted the formation of more oxygen vacancies, which increased the separation efficiency of photogenerated carriers and enhanced photocatalytic activity. Moreover, the presence of Sn ions enhanced light absorption and the specific surface area of Cu2O, and reduced photogenerated carriers recombination. The synergistic effect of the abovementioned advantages, induced excellent photocatalytic activity to the as-prepared catalysts. Tin chloride (30 mg)-doped Cu2O showed optimal photocatalytic properties with the highest norfloxacin degradation rate of 83.9 % in 140 min under visible light irradiation. Hydroxy radicals played a major role during degradation as demonstrated by the capturing of active species experiment and EPR testing. Photocatalytic mechanisms and possible degradation pathways were proposed based on Perdew-Burke-Ernzerhof and high-performance liquid chromatography-mass spectrometry techniques. The toxicity analyses of the intermediates proved their low toxicity. Repeated cycling experiments confirmed the excellent stability of the catalysts. This work provides a feasible strategy for fabricating high-performance Cu2O-based photocatalysts.

Synergistically enhanced photocatalytic properties of Co3O4-G/GO nanocomposites: unravelling their interactions and charge-transfer dynamics using XAS.

Metal oxide composites with graphene/graphene oxide have increasingly gained popularity in enhancing the photocatalytic degradation of several existing harmful dyes. Moreover, identifying the role of carbon networks and their interactions in composite formation would assist in the design and development of photocatalysts. In the present study, we investigated the role of carbon networks in improving photocatalytic properties. Electronic structure analysis of cobalt oxide-graphene (C2)/graphene oxide (C3) nanocomposites using XAS suggested possible charge transfer from cobalt oxide nanoparticles to the carbon network during composite formation. The photocatalytic degradation of C3 towards phenol dye (1×10-3M) was >50% and improved the degradation rate with k = 0.231 h-1.In the quest to understand the mechanism unfolding on its surface, in situ XAS under UV-visible irradiation was performed, which shed light on delayed excitonic recombination in the synthesized nanocomposites. This enabled hydroxy radicals (˙OH) to play a preeminent role in the cleavage of the phenol ring and its intermediaries. Based on these observations, a detailed mechanism for charge transfer occurring during nanocomposite formation and the mechanism involved in the enhanced photocatalytic activity of the nanocomposite photocatalyst towards phenol degradation under the influence of UV-visible irradiation are discussed.

Theoretical Investigation on Water-Free, Water- and Self-Assisted H-Abstraction Reactions from Dimethylamine by Hydroxy Radicals.

Accurate branching ratios of the H-abstraction reactions from dimethylamine (DMA) by OH radicals are important in understanding the atmospheric fate of DMA. In this work, the reaction kinetics of the water-free, water-assisted, and self-assisted H-abstraction reactions between DMA and OH radicals are accurately determined using the multipath canonical variational theory with the small-curvature tunneling correction, to explore the catalytic effects of the reactant (DMA) and product (water). To choose a suitable method that well describes the current reaction systems, various combinations with seven DFT methods and six basis sets are first evaluated, and the M08-HX/ma-TZVP method is identified as the most appropriate, with a mean unsigned deviation of 0.9 kcal mol-1 against the gold-standard CCSD(T)/CBS(T-Q) method. Based on the determined potential energy surfaces with the considerations of ground-state structures and specific-reaction parameters of zero-point energies, rate constants and branching ratios are calculated in a wide temperature range. The calculations show that the participation of water and DMA can lead to three-body complexes with a lower energy and influence the energy barriers, but neither of them shows the catalytic effect on the H-abstraction reactions in terms of kinetics. Additionally, the branching ratio analysis demonstrates that the product distribution is significantly altered in the presence of DMA and water.

Investigation of hydrogen/air co-flow jet flame propagation mechanism in supersonic crossflow

The design of fuel injection schemes is crucial for improving the combustion performance of high-Mach number scramjet. To clarify the feasibility of the coaxial jet injection scheme, high fidelity Large Eddy Simulation of the supersonic coaxial jet flame is conducted. The simulations are in good agreement with the experimental results in terms of time-averaged velocity, temperature, and species distribution. Auto-ignition phenomenon and the characteristics of partially premixed flame are well captured. The introduction of co-flow air increases the vorticity magnitude close to the injection port and downstream near-wall region, which results in a 400 K rise in the time-averaged temperature on the downstream near-wall region and a 4% increase in the proportion of premixed combustion near the injection port. Moreover, the instantaneous distribution of hydroxy radical indicates that the spanwise width of the windward reaction shear layer is reduced utilizing the coaxial jet scheme. Chemical kinetic analysis is applied to reveal the propagation mechanism of partially premixed flames. Thermal explosion is the chemical explosion mode for all coaxial jet flame front, which are dominated by a high-temperature reaction path. The low-temperature reaction path mainly exists in the transverse jet injection port, downstream near-wall region of the single transverse jet and co-flow lifted flame base. These significant findings provide valuable insights for the potential engineering application of the coaxial jet injection scheme to a high Mach number scramjet.

Sustainable photoelectrocatalytic oxidation of antibiotics using Ag–CoFe2O4@TiO2 heteronanostructures for eco-friendly wastewater remediation

Developing high-performance and durable catalysts presents a significant challenge for oxidizing toxic inorganic and pharmaceutical compounds in wastewater. Recently, there has been a surge in the development of new heterogeneous catalysts for degrading pharmaceutical compounds, driven by advancements in electrocatalysts and photoelectrocatalysts. In this study, a plasmonic Ag nanoparticles decorated CoFe2O4@TiO2 heteronanostructures have been successfully designed to fabricate a high-performing photoelectrode for the oxidation of pharmaceutical compounds. The developed Ag–CoFe2O4@TiO2 possessed a higher electrochemical stability and effectively harvested the UV to visible and NIR radiation in sunlight which generates the enormous photochemical reactive species that involved in the oxidation of ibuprofen in wastewater. Under direct sunlight irradiation, Ag–CoFe2O4@TiO2 achieved complete oxidation of ibuprofen in wastewater at 0.8 V vs RHE. This indicates that metallic Ag nanoparticles are involved in the charge separation and transport of charge carriers from the photoactive sites of CoFe2O4@TiO2, promoting the generation of abundant hydroxy, oxy, and superoxide radicals that actively break the bonds of ibuprofen. Additionally, oxidation agents such as urea and H2O2 were utilized to enhance the formation of superoxide ions and hydroxyl radicals, which rapidly participate in the oxidation of ibuprofen. Significantly, testing for recyclability confirmed the stability of the Ag–CoFe2O4@TiO2 photoanode, ensuring its suitability for prolonged use in photoelectrochemical advanced oxidation processes. Integrating Ag–CoFe2O4@TiO2 photoanodes into water purification systems could enhance economic feasibility, reduce energy consumption, and improve efficiency.

Investigating the Analgesic Effect of Flavonoid Rich Fraction from Pteris quadriaurita: Evidence from In-silico, In-vitro and In-vivo Studies

Pteris quadriaurita, a highly significant underutilized plant species that was widely recognized for its ethnobotanical and ethnomedicinal properties. The work aimed to estimate the flavonoid-rich fraction of P. quadriaurita (PQFRF), which was typically used to alleviate pain, for its antioxidant profile and associated analgesic effectiveness. In-silico molecular docking and PRIME MM-GB/SA studies were performed to analyze the binding pattern of nine bioactive substances identified by gas chromatography-mass spectrometry (GC-MS). The plant’s antioxidant activities were tested in-vitro using DPPH, ferricreducing antioxidant power, Superoxide anion radical, and hydroxy radical scavenging tests. For in-vivo analgesic research, the hot plate model, acetic acid-induced writhing, and tail flicking models were utilised. PQFRF was found to be equipotent to the reference medication in the studied peripheral and central analgesic models at a maximal dose of 50 mg/kg.

Simultaneous Protonation and Metalation of a Porphyrin Covalent Organic Framework Enhance Photodynamic Therapy.

Covalent organic frameworks (COFs) have been explored for photodynamic therapy (PDT) of cancer, but their antitumor efficacy is limited by excited state quenching and low reactive oxygen species generation efficiency. Herein, we report a simultaneous protonation and metalation strategy to significantly enhance the PDT efficacy of a nanoscale two-dimensional imine-linked porphyrin-COF. The neutral and unmetalated porphyrin-COF (Ptp) and the protonated and metalated porphyrin-COF (Ptp-Fe) were synthesized via imine condensation between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin and terephthalaldehyde in the absence and presence of ferric chloride, respectively. The presence of ferric chloride generated both doubly protonated and Fe3+-coordinated porphyrin units, which red-shifted and increased the Q-band absorption and disrupted exciton migration to prevent excited state quenching, respectively. Under light irradiation, rapid energy transfer from protonated porphyrins to Fe3+-coordinated porphyrins in Ptp-Fe enabled 1O2 and hydroxyl radical generation via type II and type I PDT processes. Ptp-Fe also catalyzed the conversion of hydrogen peroxide to hydroxy radical through a photoenhanced Fenton-like reaction under slightly acidic conditions and light illumination. As a result, Ptp-Fe-mediated PDT exhibited much higher cytotoxicity than Ptp-mediated PDT on CT26 and 4T1 cancer cells. Ptp-Fe-mediated PDT afforded potent antitumor efficacy in subcutaneous CT26 murine colon cancer and orthotopic 4T1 murine triple-negative breast tumors and prevented metastasis of 4T1 breast cancer to the lungs. This work underscores the role of fine-tuning the molecular structures of COFs in significantly enhancing their PDT efficacy.

Quantifying bimolecular reaction kinetics of isoprene hydroxy peroxy radical: From dry to highly humid atmospheric environment

Isoprene hydroxy peroxy radicals (ISOPOO), derived from isoprene oxidation by hydroxy radicals (OH), are key intermediates for ozone and secondary organic aerosol (SOA) formation in the atmosphere. Although ISOPOO-water complexes are ubiquitous, their impacts on ISOPOO chemistry remain obscure. Here the previously overlooked water effect on the bimolecular reaction kinetics of ISOPOO was investigated in an oxidative flow reactor. The major first-generation products of ISOPOO, isoprene hydroxy hydroperoxides (ISOPOOH), methacrolein (MACR), and methyl vinyl ketone (MVK), were measured simultaneously at various relative humidity (RH) with the help of a cold trap to avoid potential losses in direct gas sampling. We found that ISOPOO reactions were accelerated significantly under wet conditions, with a greater enhancement on 1,2-ISOPOO than 4,3-ISOPOO. 1,2-ISOPOOH yield appeared faster growth with RH than 4,3-ISOPOOH. MVK yield showed an upward-downward trend with RH, while MACR yield plateaued from 30% RH. To explain the enhancement in the ISOPOOH yield from 3% to 80% RH, the overall rate constants of 1,2-ISOPOO + HO2 and 4,3-ISOPOO + HO2 reactions at 80% RH should be 13 times and twice those at 3% RH, respectively. The empirical formulas were proposed for the first time to parameterize the water effect on ISOPOO + HO2 reactions. The updated kinetics of ISOPOO reactions were incorporated in a box model to simulate the RH-dependent ISOPOOH and C4 carbonyl yields under typical atmospheric conditions. High RH can enhance the ISOPOOH yield in urban, rural, and forest areas, and promote SOA formation correspondingly. Our findings shed light on the critical role of humidity in the reactions of ISOPOO and benefit evaluating the fate of isoprene and its impacts on air quality more accurately in the ambient atmosphere.

Catalytic ozonation of 2, 4-dichlorophenoxyacetic acid wastewater by Fe-La@ZE catalyst

This study developed a salt-tolerant multimetal ozone catalyst Fe-La@Zeolite (Fe-La@ZE) and effectively catalyzed the ozone depletion of high-salinity 2,4-dichlorophenoxyacetic acid wastewater (2,4-D) and an entropy to evaluate the comprehensive gray cluster analysis model was created using catalytic ozonation conditions. Characterization results show that Fe-La@ZE has a developed pore structure and Fe and La are successfully loaded into the interior and surface of the zeolite support, which are in the form of α-Fe2O3 and La2O3. The COD removal rate of zeolite adsorption, ozone oxidation alone and catalyzed ozone oxidation with empty zeolite support are 4.9 %, 46.5 % and 57.5 %. The removal rates of COD, total phenol and 2,4-dichlorophenol by catalytic ozonation under the conditions of pH = 0.89, ozone dose of 0.2 g/L, catalyst filling rate of 10 % and height to diameter ratio of the reactor 6:1 are 84.2 %, 87.8 % and 99.0 % respectively. Hydroxy radicals (OH) and superoxide radicals (O2) are the main active substances that catalyze the degradation of 2,4-dichlorophenol in the ozone oxidation system. Water quality characterization shows that most phenolic organic compounds and macromolecular organic acids are broken down and converted into intermediate products. The comprehensive analysis model of entropy gray clustering is used to evaluate the operating condition data of the catalytic ozonation treatment of 2,4-dichlorophenoxyacetic acid wastewater with the Fe-La@ZE catalyst and determine the optimal operating condition.

Effect of pH on the ozonolysis degradation of p-nitrophenol in aquatic environment and the synergistic effect of hydroxy radical.

Density functional theory (DFT) was employed to elucidate the mechanisms for ozonolysis reaction of p-nitrophenol (PNP) and its anion form aPNP. Thermodynamic data, coupled with Average Local Ionization Energies (ALIE) analysis, reveal that the ortho-positions of the OH/O- groups are the most favorable reaction sites. Moreover, rate constant calculations demonstrate that the O3 attack on the C2-C3 bond is the predominant process in the reaction between neutral PNP and O3. For the aPNP + O3 reaction, the most favorable pathways involve O3 attacking the C1-C2 and C6-C1 bonds. The rate constant for PNP ozonolysis positively correlates with pH, ranging from 5.47 × 108 to 2.86 × 109M-1s-1 in the natural aquatic environment. In addition, the formation of hydroxyl radicals in the ozonation process of PNP and the mechanisms of its synergistic reaction of PNP with ozone were investigated. Furthermore, the ozonation and hydroxylation processes involving the intermediate OH-derivatives were both thermodynamically and kinetic analyzed, which illustrate that OH radicals could promote the elimination of PNP. Finally, the toxic of PNP and the main products for fish, daphnia, green algae and rat were assessed. The findings reveal that certain intermediates possess greater toxicity than the original reactant. Consequently, the potential health risks these compounds pose to organisms warrant serious consideration.