Radical Chain Reaction Research Articles

Fe/Mn-MOFs with monocarboxylic acid-induced defects enhances the catalytic oxidation of calcium sulfite in desulfurization ash

The application of catalysis is an effective way to enhance calcium sulfite oxidation reactions, which is essential to the calcium-based wet flue gas desulfurization and the handle and/or utilization of the solid by-product from semi-dry desulfurization process, i.e., desulfurization ash. In this report, we present a method for constructing Fe/Mn(BDC)(DMF,OA) bimetallic catalysts with defect engineering by using monocarboxylic acids with varying chain lengths as regulators. After removing the monocarboxylic acid, the unsaturated coordinated iron and manganese active sites in Fe/Mn(BDC)(DMF,OA) become more abundant. This makes it easier to adsorb O2 and activate it into reactive oxygen species (O2–), which in turn activates the radical chain reaction and promotes the production of sulfur-oxygen free radicals(SO5−). Density functional theory (DFT) calculations show that the synergistic effect of Fe-Mn bimetallic catalysts reduces the energy barrier for SO42− formation, thereby accelerating the oxidation of sulfite. Upon addition of Fe/Mn(BDC)(DMF,OA), the oxidation rate of calcium sulfite within 3 h increased from 2.76 % to 96.09 %, compared to non-catalytic oxidation. After five cycles, the 3 h oxidation rate of calcium sulfite decreased by 10.42 % compared to the first cycle, and the higher leaching rate of Mn element was the main reason for the decrease in catalytic performance. The catalyst is non-toxic and economical, showing significant potential for resource utilization of CaSO3-containing desulfurization ash.

Carbon Free Radical (R⋅) Inactivates NF‐κB for Radical Capping Therapy

AbstractInactivating hyperactivated transcription factors can overcome tumor therapy resistance, but their undruggable features limit the development of conventional inhibitors. Here, we report that carbon‐centered free radicals (R⋅) can inactivate NF‐κB transcription by capping the active sites in both NF‐κB and DNA. We construct a type of thermosensitive R⋅ initiator loaded amphiphilic nano‐micelles to facilitate intracellular delivery of R⋅. At a temperature of 43 °C, the generated R⋅ engage in electrophilic radical addition towards double bonds in nucleotide bases, and simultaneously cap the sulfhydryl residues in NF‐κB through radical chain reaction. As a result, both NF‐κB nuclear translocation and NF‐κB‐DNA binding are suppressed, leading to a remarkable NF‐κB inhibition of up to 94.1 %. We have further applied R⋅ micelles in a clinical radiofrequency ablation tumor therapy model, showing remarkable NF‐κB inactivation and consequently tumor metastasis inhibition. Radical capping strategy not only provides a method to solve the heat‐sink effect in clinic tumor hyperthermia, but also suggests a new perspective for controllable modification of biomacromolecules in cancer therapy.

Carbon Free Radical (R⋅) Inactivates NF-κB for Radical Capping Therapy.

Inactivating hyperactivated transcription factors can overcome tumor therapy resistance, but their undruggable features limit the development of conventional inhibitors. Here, we report that carbon-centered free radicals (R⋅) can inactivate NF-κB transcription by capping the active sites in both NF-κB and DNA. We construct a type of thermosensitive R⋅ initiator loaded amphiphilic nano-micelles to facilitate intracellular delivery of R⋅. At a temperature of 43 °C, the generated R⋅ engage in electrophilic radical addition towards double bonds in nucleotide bases, and simultaneously cap the sulfhydryl residues in NF-κB through radical chain reaction. As a result, both NF-κB nuclear translocation and NF-κB-DNA binding are suppressed, leading to a remarkable NF-κB inhibition of up to 94.1 %. We have further applied R⋅ micelles in a clinical radiofrequency ablation tumor therapy model, showing remarkable NF-κB inactivation and consequently tumor metastasis inhibition. Radical capping strategy not only provides a method to solve the heat-sink effect in clinic tumor hyperthermia, but also suggests a new perspective for controllable modification of biomacromolecules in cancer therapy.

Leveraging Propargyl Sulfides as Radical Trappers for the Synthesis of Sulfonyl Allenes

AbstractThis work showcases a novel visible‐light mediated allenylation protocol employing propargyl sulfides as a pioneering radical trapping methodology. A diverse array of substituted sulfonyl allenes were successfully synthesized under mild conditions with commendable levels of chemo‐ and regio‐selectivity. Mechanistically, this process entails the formation of sulfonyl radicals, their subsequent addition to alkynes, the subsequent elimination of S‐centered radicals, and Cl‐atom abstraction, thereby facilitating the propagation of this radical chain reaction.

Efficient calcium sulfite oxidation treatment by a highly active iron-manganese bimetallic metal-organic frameworks (MOFs)

Calcium sulfite (CaSO3) oxidation is the key step in the resource utilization of flue gas desulfurization (FGD) ash waste. However, under natural conditions the oxidation rate of CaSO3 is very low, limiting its conversion into calcium sulfate, an acceptable product for construction material. This study was devoted to the investigation of the synthesis and performance of a bimetallic MOFs with potential catalytic activity, namely, Fe/Mn(BDC)(DMF,F) catalysts. A combination of techniques including SEM, EDS, XRD, FT-IR, etc. were used to characterize the catalysts. The excellent catalytic performance examined in a gas-liquid-solid three-phase oxidation system are due to the special flexible respiratory architecture and homogeneous distribution of active sites, which allows the reactants to fully contact with the catalyst. Mn incorporated in the backbone of the metal-organic framework significantly enriches the catalytic active species that participate in a radical chain reaction with activated SO32- as ·SO3-, which in turn generates the key radical ·SO5- that reacts with SO32- to form SO42-. In the presence of Fe/Mn(BDC)(DMF, F)-13, the oxidation ratio of CaSO3 could reach 90.71%, which is more than 30-fold compared to non-catalytic oxidation and almost 5 times the effects of the single metal Fe(BDC)(DMF, F) catalyst. In addition, the study of kinetics shows that the oxidation rate of Fe/Mn(BDC)(DMF,F)-13 can reach 0.042 mmol·L-1·s-1 with an apparent activation energy of 10.86 kJ/mol. The oxidation rate is mainly affected by reaction temperature, pH value, catalyst concentration, and air flow rate. This study provides a potentially sustainable way for utilization of CaSO3-containing desulfurization ash.

Thermal decomposition mechanism of lithium methyl carbonate in solid electrolyte interphase layer of lithium-ion battery

To predict the early stages of thermal runaway and improve the safety of lithium-ion batteries, it is necessary to examine the elementary reaction steps for the thermal decomposition of individual solid electrolyte interphase (SEI) components. This study elucidates a detailed decomposition mechanism of lithium methyl carbonate (LMC) which is one of SEI components and accounts for the majority of SEI components formed in commercial electrolytes. The detailed reaction mechanism for the thermal decomposition of LMC is proposed based on the in-situ/ex-situ experiments and density functional theory calculations. LMC underwent six reactions before finally converting to Li2CO3 at 300 °C. To supplement the reliability of the proposed reaction mechanism, the actual gas composition measured using mass spectrometry (MS) are compared with the chain reactions of radicals generated through the thermal decomposition reactions, which is calculated using GRI-MECH 3.0, a gas-phase reaction mechanism. The methodology proposed in this study can be used both for analyzing the reaction mechanisms of different SEI components and their coupling effects with the electrolyte in the future. Understanding these reaction mechanism sets will help us to understand the degradation reactions of real complex SEI and the initial self-heating stage during thermal runaway.

Initiation and Carbene Induced Radical Chain Reactions in CH2F2 Pyrolysis.

High temperature dissociations of organic molecules typically involve a competition between radical and molecular processes. In this work, we use a modeling, experiment, theory (MET) framework to characterize the high temperature thermal dissociation of CH2F2, a flammable hydrofluorocarbon (HFC) that finds widespread use as a refrigerant. Initiation in CH2F2 proceeds via a molecular elimination channel; CH2F2→CHF+HF. Here we show that the subsequent self-reactions of the singlet carbene, CHF, are fast multichannel processes and a facile source of radicals that initiate rapid chain propagation reactions. These have a marked influence on the decomposition kinetics of CH2F2. The inclusion of these reactions brings the simulations into better agreement with the present and literature experiments. Additionally, flame simulations indicate that inclusion of the CHF+CHF multichannel reaction leads to a noticeable enhancement in predictions of laminar flame speeds, a key parameter that is used to determine the flammability of a refrigerant.

The critical roles of surface-bound radicals in the nickel phosphide/biochar-persulfate catalytic oxidation system for tetracycline removal: The synergistic catalysis between nickel phosphides and biochar

Exploring efficient and cost-effective heterogeneous persulfate (PS) oxidation systems is meaningful for addressing recalcitrant organic pollutants in wastewater. Herein, nickel phosphide/biochar (NixP/biochar) composite, with Ni12P5 as the predominant crystalline phase, is firstly synthesized utilizing a biomass phosphorus source, phytic acid (PA). NixP/biochar demonstrates outstanding catalytic capacity in activating PS for removing tetracycline (TC). At 1 mM PS, 0.15 g/L catalyst, and pH 7.0, 94.55 % of TC (20 mg/L) can be removed within 180 min, markedly superior to Fe-, Cu-, and Co-based phosphide/biochar composites. The NixP/biochar-PS system exhibits superior catalytic degradation efficiency (>94.00 %) against varying concentrations (1–20 mg/L) of TC and robustly resists interferences from complex water matrices, including sodium humate solution, surface water, anions (>90.00 %). The ideal catalytic efficiency is ascribed to surface-bound radicals (including SO4-• and •OH), with •O2– and 1O2 assisting in. Density functional theory (DFT) calculations indicate that due to the electron donations from Ni, P, and C, S2O82- may undergo homolysis to produce the surface-bound SO4-•, which may induce the generation of other reactive oxygen species (ROSs) through radical chain reactions. Besides, the electronic structures and work functions of NixP in NixP/biochar composites can be modulated by the biochar, enhancing the catalytic selectivity of NiP, Ni2P, and Ni12P5 with Ni as the electron-donating center, while diminishing that of P-centered Ni3P. These findings may serve as a reference for the theoretical study of Ni-based catalysts and the practical application of NixP in AOPs.

Urchin-like Ni-Fe-Mo sulfide: An effective electrochemical calcium sulfite activator for tetracycline degradation

Sulfite is deemed as a promising precursor to produce highly reactive species for contaminants remediation. Herein, the urchin-like Ni-Fe-Mo sulfide (NiFeMoSx) was anchored in-situ on nickel foam as a cathode to activate CaSO3 for efficient degradation of tetracycline (TC) under natural condition. The degradation efficiency reached 92.7% within 60 min, which was about 1.81 times higher than that of the electro-Fenton process based on NiFeMoSx. The beneficial performance came from the synergistic activation of CaSO3 by simultaneous rapid redox cycles of Fe(II)/Fe(III) and Ni(II)/Ni(III) on the NiFeMoSx cathode. Specifically, the primary intermediates Fe(II)-HSO3- and Ni(II)-SO32- triggered a series of radical chain reactions, accompanied the reduction of Ni(III)/Fe(III) by electrochemistry and electron donor of Mo(IV) and S2- on the surface of the catalyst. The regeneration of the Fe(II)/Ni(II) was quickly realized and subsequently triggered the chain reactions, which would accelerate the formation rate of reactive species, such as SO4∙−, ·OH, O2∙− and 1O2, of which 1O2 and O2•- played important roles on degradation TC. This work provides a promising application for the efficient removal of persistent organic pollutants by metal sulfide activated sulfite.

System-wide coordination and communication of lipid metabolism atlas revealed cytotoxicity of epoxy triglyceride in deep-frying oil

The epoxy triglycerides generated by oxidation, cyclization, and free radical chain reaction of unsaturated dietary oils during deep-frying are demonstrated to have cytotoxicity and can induce lipid metabolism related diseases. Metabolic diseases are usually characterized by metabolic abnormalities in different tissues, however, the relationship between changes in intratissue coordination and communication induced by epoxy triglycerides and specific pathogenic mechanisms remains largely unknown. We conducted lipid metabolomics analysis across six different tissues in C57BL/6J mice, including the medial prefrontal cortex, interscapular brown adipose tissue, epididymal white adipose tissue, liver, intestine, and heart. Normal diet intake demonstrated a high degree of association between lipid metabolites, indicative of cross-communication and cooperation among various tissues and organs, while, a global correlation that was disrupted and restructured by epoxy triglycerides intake. Examination of blood samples revealed that epoxy triglycerides enhanced bacterial translocation from the gut to the systemic circulation, consequently stimulating the TLR4/CD36/NF-κB pathway. In summary, this study found that epoxy triglyceride upsets the comprehensive coordination and information exchange of lipid metabolism, providing a fresh perspective for future research on the systemic metabolic network and identifying metabolic disease markers and associated mechanisms induced by deep-frying oil.

A multifunctional tannic acid binder for 5.0 V LiNi0.5Mn1.5O4 electrodes and its interfacial characterization

Due to the higher working voltage of spinel LiNi0.5Mn1.5O4 (LNMO), the electrolyte degrades at high potentials, leading to the generation of numerous alkyl radicals.The transition metals will dissolve under high-voltage reactions, resulting in an unstable LNMO/electrolyte interface, ultimately deteriorating the battery’s cycling performance. In this study, a PAALi-TAc composite binder was obtained through the crosslinking of polyphenolic hydroxides Tannic acid (TAc) with PAALi. The electrode fabricated using this binder achieved a maximum capacity of 132.6 mAh g−1 at a 1 C rate. After 100 cycles, the capacity remained at 130.3 mAh g−1, with a retention rate of 98.2%. Even after 400 cycles, the capacity was maintained at 113.2 mAh g−1, with a retention rate of 85.3%. During the 400 cycles of high-current fast charge and discharge at 5 and 10 C, the capacity retention rates were 89.3% and 88.0%, respectively. The PAALi-TAc binder played a crucial role in establishing a compatible electrolyte interface by terminating the free radical chain reactions and chelating the excess dissolved metals in high-voltage LNMO//Li batteries, and this led to improved cycling and rate performance.

Wood consolidation through an epoxy‐acrylic gamma‐crosslinked three‐dimensional system

AbstractEmerging technologies based on polymeric materials are progressively developed in order to preserve and consolidate cultural heritage artifacts. In this study, we aimed to obtain a hybrid polymer reliant on two types of thermosets that undergo irreversible crosslinking via ionizing radiation‐induced polymerization, the polymer's structure and characteristics being tailored using specific dose rates, doses, linear energy transfer and monomers ratio, in order to achieve the established performance requirements. Here, we demonstrate a covalently bonded 3D hybrid diepoxy‐triacrylic polymer that is chemically and dimensionally stable, intending to use it as a consolidant of highly degraded wooden artifacts in order to mitigate oxygen inhibition from radical chain reactions, to increase chemical and thermal stability, as well as to obtain a stiffer consolidated artifact, therefore more resistant to deformation. Various types of analytical techniques such as Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy, Mass Spectrometry or Thermal analysis were performed in order to support our strategy and predictions regarding the synergistic effect given by gamma irradiation‐driven crosslinking through simultaneous cationic and radical chain growth polymerization reaction mechanisms. We achieved a homogenous polymeric formulation and wood‐polymer composite materials with high modulus of elasticity, therefore providing up to a twofold increase in Young's modulus in the consolidated wood, a good chemical resistance to various solvents and outstanding thermal resistance up to 381°C. Consequently, the consolidation methodology, as well as mechanical testing, analytical and morphological characterization of the resulted composite will be discussed. Apart from consolidating cultural heritage wooden artifacts, this synthetic route and impregnation methodology provide opportunities for wood‐polymer composites in a wealth of applications as reinforced wood‐based materials.

What is the Initiating Reaction for the Lipid Radical Chain Reaction System That Can Induce Ferroptotic Cell Death at the Lower Oxygen Content?

The neural cell death in cerebral infarction is suggested to be ferroptosis-like cell death, involving the participation of 15-lipoxygenase (15-LOx). Ferroptosis is induced by lipid radical species generated through the one-electron reduction of lipid hydroperoxides, and it has been shown to propagate intracellularly and intercellularly. At lower oxygen concentration, it appeared that both regiospecificity and stereospecificity of conjugated diene moiety in lipoxygenase-catalysed lipid hydroperoxidation are drastically lost. As a result, in the reaction with linoleic acid, the linoleate 9-peroxyl radical-ferrous lipoxygenase complex dissolves into the linoleate 9-peroxyl radical and ferrous 15-lipoxygenase. Subsequently, the ferrous 15-lipoxygenase then undergoes one-electron reduction of 13-hydroperoxy octadecadienoic acid, generating an alkoxyl radical (pseudoperoxidase reaction). A part of the produced lipid alkoxyl radicals undergoes cleavage of C-C bonds, liberating small molecular hydrocarbon radicals. Particularly, in ω-3 polyunsaturated fatty acids, which are abundant in the vascular and nervous systems, the liberation of small molecular hydrocarbon radicals was more pronounced compared to ω-6 polyunsaturated fatty acids. The involvement of these small molecular hydrocarbon radicals in the propagation of membrane lipid damage is suggested.

Thermal Runaway Inhibition of Adipic Acid Green Synthesis Based on a Radical Chain Reaction Mechanism

Thermal Runaway Inhibition of Adipic Acid Green Synthesis Based on a Radical Chain Reaction Mechanism

Ultrasound-driven radical chain reaction and immunoregulation of piezoelectric-based hybrid coating for treating implant infection

The poor efficiency of US-responsive coatings on implants restricts their practical application. Immunotherapy that stimulates immune cells to enhance their antibacterial activity is expected to synergize with sonodynamic therapy for treating implant infection effectively and safely. Herein, US-responsive hybrid coatings composed of the oxygen-deficient BaTiO3 nanorod arrays and l-arginine (BaTiO3-x/LA) are designed and prepared on titanium implants for sonocatalytic therapy-cooperated immunotherapy to treat Methicillin-resistant Staphylococcus aureus (MRSA) infection. BaTiO3-x/LA can generate more oxidizing reactive oxygen species (ROS, hydroxyl radical (·OH)) and reactive nitrogen species (RNS, peroxynitrite anion (ONOO−)). The construction of nanorod arrays and oxygen defects balances the piezoelectric properties and sonocatalytic capability during US treatment. The generated piezoelectric electric field provides a sufficient driving force to separate electrons and holes, and the oxygen defects attenuate the electron-hole recombination efficiency, consequently increasing the yield of ROS during the US treatment. Moreover, nitric oxide (NO) released by l-arginine reacts with the superoxide radical (·O2−) to produce ONOO−. Since, this radical chain reaction improves the oxidizing ability between bacteria and radicals, the cell membrane (argB, secA2) and DNA (dnaBGXN) are destroyed. The bacterial self-repair mechanism indirectly accelerates bacterial death based on the transcriptome analysis. In addition to participating in the radical chain reaction, NO positively affects macrophage M1 polarization to yield potent phagocytosis to MRSA. As a result, without introducing an extra sonosensitizer, BaTiO3-x/LA exhibits excellent antibacterial activity against MRSA after the US treatment for 15 min. Furthermore, BaTiO3-x/LA facilitates macrophage M2 polarization after implantation and improves osteogenic differentiation. The combined effects of sonodynamic therapy and immunoregulation lead to an effective and safe treatment method for implant-associated infections.

Sustainable cycling and mechanism of Co(II)/Co(IV)/Co(III) with S(IV) highly triggered by Co(IV) in E/Co(II)/S(IV) for enhanced removal of reactive brilliant red X-3B

The massive discharge and inadequate treatment of dye wastewater have led to the extensive accumulation of azo dyes in natural water bodies, which is a severe threat to human health. In this study, a novel homogeneous electrochemical system, denoted E/Co(II)/S(IV), was developed by the incorporation of an electric field and cobalt/sulfite. Notably, the decontamination efficiency of the E/Co(II)/S(IV) system for reactive brilliant red X-3B (X-3B) was 95.14 % within 10 min, which was accomplished by utilizing only a trace amount of Co(II). The entire process exhibited an exceptionally low energy consumption of only 0.331 kWh/m3. Single-factor experiments were conducted to explore the influence of various operational parameters and water matrix components on the system decontamination efficiency. By combining the chelator EDTA and chemical probe PMSO, the presence of Co(III) and Co(IV) was detected. The results showed that Co(IV) mainly triggered the chain reaction. The activation products of S(IV), including SO3•−, SO4•−, SO5•− and HO∙, played a dominant role in the degradation of X-3B, with SO4•− having the most substantial contribution. Under anodic oxidation, Co(II) underwent double-electron transfer, leading to the conversion of Co(II) into Co(IV). Subsequently, Co(IV) activated S(IV) via a single-electron transfer mechanism, initiating a free radical chain reaction. During the reaction, Co(IV) transformed into Co(III) and Co(II), thus achieving the Co(II)/Co(IV)/Co(III) cycle. The generation of oxygen as a result of the electrochemical process offers a viable solution for addressing the issue of hypoxia stemming from the rapid activation of S(IV). The active sites in the X-3B molecule were elucidated through density functional theory predictions, and three degradation pathways for X-3B were identified via mass spectrometry analysis. The toxicological characteristics of both X-3B and its degradation products were comprehensively assessed using toxicity estimation software tool and algal culture experiments. This research offers valuable insights into the refinement of cobalt/sulfite systems and introduces innovative concepts for electrochemical applications, which have broad-reaching implications for dye wastewater purification.

FORMULASI MASKER GEL PEEL OFF EKSTRAK BUNGA TELANG (Clitoria ternatea L.) SEBAGAI ANTIOKSIDAN ALAMI

Natural ingredients containing antioxidant compounds can be made in the form of a peel-off gel mask which can help care for facial skin. Butterfly pea flowers (Clitoria ternatea L.) contain flavonoid anthocyanin compounds which can break the chain reaction of free radicals. The aim of this research is to determine the antioxidant activity of butterfly pea flower extract and the preparation of butterfly pea peel off gel mask. The peel off gel mask formulation uses butterfly pea flower extract with a concentration of 5%. Testing for antioxidant activity uses the DPPH method. Physical characteristics assessment includes organoleptic tests, homogeneity observations, spreadability tests, viscosity tests, drying time tests, and preparation pH tests. Based on the research results, the IC50 value of telang flower extract is 43.68 ppm in the very strong category and the IC50 value of the peel-off gel mask preparation is 307.71 ppm in the inactive category. This research shows that the ethanol extract of butterfly pea flowers has potential as a natural antioxidant.

A preliminary study on a new approach for measurement of the antioxidant capacity of single molecules in food

Antioxidant activity refers to the rate of reaction between a specific antioxidant and a specific oxidant. On the other hand, antioxidant capacity is a measure of the quantity of a free radical in a concentration, neutralized by antioxidant molecules under examination. All common methods such as: Ferric Reducing Antioxidant Power (FRAP), Total Peroxyl Radical Antioxidant Parameter (TRAP), Oxygen Radical Absorption Capacity (ORAC), Crocin Bleaching Assay (CBA), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and others have some technical limitations. All methods, before any analytical test, require a sample preparation, which is separated into hydrophilic and lipophilic fractions. However, this already represents an artifact, because some of the properties of the biological matrix are lost. The new OXEFIN unit defined as the ratio between the electrical power of the sample and the control allows us to compare the antioxidant capacities of single substances or a mixture of them, without the use of a target molecule and equipment such as a spectrophotometer or other optical detection instruments. Moreover, we are able to detect the total antioxidant capacity in an opaque solution without sample preparation(such as food). The milks range from 2.73 ± 0.02 to 0.20 ± 0.003 at 4 ml and 4.33 ± 0.04 to 0.26 ± 0.003 at 8 ml. The berries and fruit juices range from 5350 ± 38 to 673 ± 5.8 at 4 ml and from 5220 ± 40 to 915 ± 5 at 8 ml. The method proposed in this paper represents a new approach to the antioxidant capacity measurements reducing the cost, analysis time, the amount of reagents and avoid the possible chemical interferences during the radical chain reaction.

Augmented degradation performance of dielectric barrier discharge plasma via optimized hydroxyl radical generation

Dielectric barrier discharge (DBD) plasma demonstrates significant potential for eliminating chlorinated aromatic compounds (CACs), while its commercial application has been hampered by inadequate generation and diffusion of active species. In response, this work introduced iron-biochar composites (Fe/BC) into DBD system to enhance the generation of highly oxidative hydroxyl radicals (OH) from underutilized O3 and H2O2, thereby reducing the diffusion of OH and accelerating the degradation of CACs. The results indicated that, in just 15 min, the combined system achieved remarkable degradation rates exceeding 95% for six diverse CACs, with the degradation rate constant increasing up to 4.27 times when compared to DBD alone. Moreover, the varied response of pollutants implied that the enhanced degradation efficiency was primarily facilitated by the reduced mass transfer distance between pollutants and formed OH. The activation of O3 on Lewis acidic sites not only directly promoted the generation of OH through free radical chain reactions but also indirectly induced more conversion of H2O2 into OH by facilitating the Fe3+/Fe2+ cycle. The identification of intermediates and toxicity analysis substantiated its environmental sustainability. This study offers a viable technical pathway and theoretical foundation for enhancing the efficiency of plasma-based treatment of organic wastewater.

Prediction of Hydrogen Abstraction Rate Constants at the Allylic Site between Alkenes and OH with Multiple Machine Learning Models.

Hydrogen abstraction reactions between hydrocarbons and hydroxyl radicals are important propagation steps in radical chain reactions, playing a crucial role in atmospheric and combustion chemistry. This study focuses on predicting the rate constants of the prototype of the reaction class of hydrogen abstractions, i.e., the primary allylic hydrogen abstraction from alkenes by the OH radical, via utilizing machine learning (ML) methods. Specifically, three distinct models, namely, feedforward neural network (FNN), support vector regression (SVR), and Gaussian process regression (GPR), have been employed to construct robust ML models for prediction. We proposed a novel strategy that seamlessly integrates descriptor preprocessing, a pairwise linear correlation analysis, and a model-specific Wrapper method to enhance the effectiveness of the feature selection procedure. The selected feature subset was then evaluated using two cross-validation techniques, i.e., leave-one-group-out (LOGO) and K-fold cross-validations, for each of the three ML models (FNN, SVR, and GPR) to assess their predictive and stability performance. The results demonstrate that the FNN model, trained with seven representative descriptors, achieves superior performance compared to the other two methods. For the FNN model, the average percentage deviation is 39.06% on the test set by performing LOGO cross-validation, while the repeated 10-fold cross-validation achieves a percentage prediction deviation of 19.1%. Two larger alkenes with 10 carbons were selected to test the prediction performance of the trained FNN model on primary allylic hydrogen abstraction. Results show that the kinetic predictions follow well the modified three-parameter Arrhenius equation, indicating the reliable performance of FNN in predicting hydrogen abstraction rate constants, especially for the primary allylic site. Hopefully, this work can shed useful light on the application of ML in generating chemical kinetic parameters of hydrocarbon combustion chemistry.