Radical Path Research Articles

Fe-N-coordinated graphene-like honeycomb porous carbon as an extremely effective catalyst for catalytic oxidation

In this study, Fe/N co-doped graphene-like honeycomb porous carbon (Fe-NC)was produced and used for the activating PMS to degrade TC. The Fe-NC catalyst has shown high activity in the TC degradation by activated PMS, with an efficiency of up to 94 % in 30 min. while the blank catalyst without N and Fe doping exhibited the lowest performance with 47.3 % TC degradation. Moreover, other operational factors of Fe-NC catalysts were also investigated to evaluate its catalytic activity. The burst experiments and electron paramagnetic resonance (EPR) experiments demonstrated that free radical paths (O2·-) and non-free radical paths (1O2) coexist inside the Fe-NC/PMS system. The experiment results and degradation mechanism analysis revealed that N species(Pyridine N, Graphite N,Fe-Nx) and iron species (Fe0) were possible to be the active species of catalysts. Furthermore, Fe-NC/PMS system was investigated for possible pathway of TC degradation by liquid mass spectrometry (LC-MS), and the presence of intermediates was analyzed for toxicity magnitude by ECOSAR software.

Synergetic sludge conditioning by US enhanced Fe2+ activated sodium persulfate: Physicochemical properties and mechanisms

Efficient dewatering of sewage sludge is an energy- and carbon-saving procedure for sludge treatment in wastewater treatment facilities. The ultrasound-coupled divalent iron ion activated persulfate process can effectively promote sludge dewatering and improve organic substance content. Under the action of ultrasound (US 50 w/L), divalent iron ions (Fe2+) 200 mg/g (TS), and persulfate (PDS) 200 mg/g (TS) for 60 min, the capillary suction time (CST) was reduced by 79.74%, and the moisture content of the dewatered sludge cake reached 56.51 wt%. The organic carbon content of treated sludge was also four times higher than the original sludge and types were richer in short-chain volatile species in US/Fe2+/PDS. Moreover, the correlation analysis found that the relationship of between CST and SV30, Zeta and lactate dehydrogenase (LDH) were positive correlation, and the relationship of SCOD and TC were positively correlated with the PN (SB-EPS). Mechanistic studies showed that the US/Fe2+/PDS system could produce oxygen activators by US coupling Fe2+ to strengthen the effect of activated PDS strongly, while the sulfate radicals (SO4·-) radical was a dominant role. The cracking mechanism is divided into two pathways effectively degraded the macromolecule EPS into a small-molecule acid and further reduced the water-holding interfacial affinity as follow: (1) the radical path dominated by hydroxyl radicals (·OH), SO4·-, and superoxide radical (O2·-); (2) the non-radicals dominated by monoclinic oxygen (1O2). Afterwards, the electrostatic force and interfacial free energy were reduced, resulting in enhanced self-flocculation and mobility to enhanced dewaterability. These findings demonstrated the US/Fe2+/PDS system had significant advantages in sludge cracking and provided theoretical support for its practical application.

Mediating peroxymonosulfate activation path in Fenton-like reaction via doping different metal atoms into g-C3N5

Peroxymonosulfate (PMS) could be activated by either radical path or non-radical path, how to rationally mediate these two routines was an important unresolved issue. This work has introduced a simple way to address this problem via metal atom doping. It was found that Fe-doped nitrogen-rich graphitic carbon nitride (Fe-C3N5) exhibited high activity towards PMS activation for tetracycline degradation, and the degradation rate was 3.14 times higher than that of Co-doped nitrogen-rich graphitic carbon nitride (Co-C3N5). Radical trapping experiment revealed the contributions of reactive species over two catalysts were different. Electron paramagnetic resonance analysis further uncovered the non-radical activation path played a dominated role on Fe-C3N5 surface, while the radical activation path was the main routine on Co-C3N5 surface. Density functional theory calculations, X-ray photoelectron spectroscopy analysis, and electrochemical experiments provided convincing evidence to support these views. This study supplied a novel method to mediate PMS activation path via changing the doped metal atom in g-C3N5 skeleton, and it allowed us to better optimize the PMS activation efficiency.

New insights into sulfite activation by amorphous Fe1−xNixS for RhB removal: the synergistic effect of free radical and non-free radical pathway

Ni doping broadens the pH response range and accelerates the electron transfer rate, so that Fe1−xNixS/sulfite can remove RhB through the synergistic effect of free radical and non-free radical paths under different pH conditions.

Breaking the Bound of Cocoon -- A Comparative Study on Black Female Identity in Sula and Yearning

In the influential work, Yearning: Race, Gender, and Cultural Politics, Bell Hooks scrutinizes prevailing Black feminist discourses, emphasizing the hegemony of white feminists, intersecting forms of oppression, and the consequential loss of subjectivity. Nevertheless, hooks innovative analysis encounters limitations when addressing the complexities within a literary context. This study conducts a comparative analysis of Black female identity construction, exploring the applicability of hooks theoretical framework to Sula, a novel by African American author Toni Morrison. This paper seeks to clarify alleged contradictions and evaluate hooks theory in three key aspects: the common predicament of Black female identity, the process of identity formation, and the relationship between identity and social class divisions. The analysis uncovers the necessity of acknowledging the shortcomings of hooks arguments when applied to Black feminist literature, such as its inattention to the profound inner struggle originating from cultural constraints in authentic experiences of Black females. Due to distinct writing contexts and backgrounds, Bell Hooks and Toni Morrison diverge in their perspectives on Black female identity, necessitating a closer examination to steer Black feminism towards a more radical path in the future.

Shorten migration distance of ROS and accelerate electron transfer by engineering dual Lewis acid sites for synergistic activation of PMS toward rapid TC degradation

Shortening the migration distance of reactive oxygen species (ROS) and accelerating electron transfer are promising strategies for boosting the performance of catalysts to activate peroxymonosulfate (PMS). Herein, metallic Lewis acid and non-metallic Lewis acid co-doped graphitic carbon nitride (Co,B-C3N4) are successfully prepared by one-step calcination for synergistically enhanced PMS activation. Cobalt sites significantly accelerated the electron transfer process. Boron acts as an adsorption site for the contaminants, extensively reducing the distance that ROS needs to migrate. Therefore, Co,B-C3N4 demonstrates exceptional PMS activation capability, successfully degrading 99% of tetracycline (TC) in just 6 min with a rate constant reaching 0.407 min−1. Moreover, Co,B-C3N4 still displayed outstanding catalytic performance in complex water environments and long-term cycling conditions. Density Functional Theory (DFT) calculation and mechanism studies demonstrated that non-free radical path (direct electron transfer process and 1O2) plays a dominant role. This work provides a feasible strategy for designing PMS activation catalysts.

Co-Mn-Fe spinel-carbon composite catalysts enhanced persulfate activation for degradation of neonicotinoid insecticides: (Non) radical path identification, degradation pathway and toxicity analysis

The extensive utilization of neonicotinoid insecticides (NNIs) in agricultural practices ultimately poses a significant threat to both the environment and human health. This work focuses on the efficient degradation and detoxification of the representative NNI, thiamethoxam (THX), and explores the underlying mechanism using a Co-Fe-Mn mixed spinel doped carbon composite catalyst activated persulfate. The findings demonstrate that the composite effectively degrades THX, achieving a degradation rate of 95% in 30 mins, while requiring only a fraction (one-sixteenth) of the oxidant dosage compared to pure carbon. The study aimed to examine the negative impact of reactive halogens on reactive oxygen species within a saline environment. The degradation byproducts were linked to the presence of two common electron-withdrawing groups, namely halogens and nitro in the THX molecule. It was hypothesized that the degradation process was primarily influenced by C-N bond breaking and hydroxylation occurring between the diazine oxide and 2-chlorothiazole rings. Consequently, dehalogenation and carbonylation processes facilitated the elimination of halogenated components and pharmacophores from the THX, leading to detoxification. In addition to the identified free radical pathway including SO4•−, •OH and O2•− contributed to THX degradation, the participation of non-radical pathways (1O2 and electron transfer) were also confirmed. The efficacy of detoxification was further validated through toxicity assessment, employing quantitative conformation relationship prediction and microbial culture utilizing Bacillus subtilis.

Jasmine waste derived biochar as green sulfate catalysts dominate non-free radical paths efficiently degraded tetracycline

Because of the potential environmental harm caused by the extensive application of tetracycline (TC), this study used jasmine waste rich in organic matter as a precursor and one-step carbonization into metal-free carbon-based materials to efficiently activate peroxymonosulfate (PMS) toward degrading TC. The jasmine waste biochar (JWB) with a heating rate of 10 °C min−1 and a heating temperature of 700 °C was selected as the most suitable material based on its catalytic performance. The effects of catalyst dose, PMS dose, initial pH value, coexisting inorganic anions and TC concentration on the JWB/PMS/TC system were thoroughly optimized. The results showed that the degradation efficiency of TC by JWB/PMS system was 90%. Meanwhile, the combination of electron paramagnetic resonance, masking experiments and X-ray photoelectron spectrometry confirmed that JWB degraded TC mainly through the non-radical radical pathway of 1O2 oxidation and mediated the electron transfer to PMS. In addition, some degradation products were analyzed by LC-MS and possible degradation pathways of the system were proposed. Therefore, this paper proposes a novel method for recycling jasmine waste and providing a low-cost catalyst for the oxidation treatment of refractory organic matter.

Visible-light promoted photoredox catalysis in flow: addition of biologically important α‑amino radicals to michael acceptors.

Visible light promoted photoredox catalyzed formation of α-amino radicals from cyclic tertiary amine compounds and their subsequent addition to Michael acceptors performed in flow conditions allowed access to a wide range of functionalized N-aryl-substituted tetrahydroisoquinolines (THIQs) and N-aryl-substituted tetrahydro-β-carbolines (THBCs). Visible light in conjunction with Ru(bpy)3Cl2 photocatalyst allowed the formation and high reactivities of α-amino radicals in flow conditions at room temperature. These reactions gave valuable products with high efficiencies; some previously unavailable reaction pathways photo or thermal reaction conditions; i.e. direct synthesis of 1-substituted (THBCs) via α-amino radical path were successfully realized in flow. The use of custom-made FEP tube microreactor proved to be the key to succesfull α-amino-radical formation and overall reaction performance in flow. Three types of light transparent custom-made microfluidic devices were tested, among them glass/silicon and FEP type reactor showed very good results in the conversion of tested compounds. Plausible reaction mechanism is proposed in accordance with known principles of photo activation of tertiary amines. Visible light promoted C(sp3)-H functionalization of N-aryl-protected tetrahydroisoquinolines and N-aryl-protected tetrahydro-β-carbolines in microflow conditions via a-amino radical pathway with various coupling partners in excellent yields and efficiencies.

Photocatalytic conversion of MB dye using Co3O4 QDs‐Ag2MoO4 as an active heterojunction photocatalyst under visible light irradiation

Herein, the preparation of Co3O4 QDs‐Ag2MoO4 (AMO) heterojunction was reported by a facile hydrothermal method and characterized by physicochemical methods such as Fourier transformed infrared (FT‐IR), X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM), differential reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and UV–Vis. The SEM images show that AMO particles and Co3O4 QDs‐AMO have a morphology of 3D‐hexagons and nanosheets accumulated on the surface of 3D‐hexagons with an average of 36 and 28 nm in size, respectively. The Co3O4 QDs‐AMO photocatalyst was used toward the conversion of methylene blue with a removal percentage of 91%, which is 15 times more than pure AMO. The higher photoactivity of Co3O4 QDs‐AMO heterojunction should be assigned to its lower charge recombination rate compared with pure AMO nanoparticles. This heterojunction photocatalyst was removed from the mixture reaction and reused five times without a considerable decline in activity. Furthermore, a postulated mechanism by the hydroxyl radical (°OH) path was proposed.

Kinetic Mechanism for Simulating the Temperature and Pressure Effect on the Explosive Decomposition of Acetylene by ReaxFF Molecular Dynamics

AbstractIn the utilization of acetylene as the raw material in chemical engineering, understanding its pyrolysis mechanism is a vital issue in avoiding its explosion. The ReaxFF MD simulation was adopted to investigate the pyrolytic behavior of acetylene at various temperatures and pressures. The simulation results revealed that the pyrolysis mechanism of acetylene could be divided into three temperature ranges: (i) T<1200 K, where homogenous molecular polymerization of acetylene occurs, producing polymerization products primarily C4H4 and C6H6; (ii) 1200<T<1800 K, where the free radical path competes with the molecular path, and free radicals such as C2H3⋅ and C4H3⋅ participate in the polymerization reaction; (iii) T>1800 K, where the acetylene molecule is cracked, and H⋅ and C2H⋅ drive the formation of polyacetylene and hydrogen. Finally, a reaction network for the pyrolysis of acetylene to yield compounds below C10 is generated through the identification, quantification, and evaluation of the reaction trajectory. The kinetic model of acetylene pyrolysis has been dramatically improved and supplemented, which is in satisfactory agreement with experimental values.

Remove humic acid from water quickly using only oxygen and sulfite at nickel cobalt spinel catalyst

The typical refractory organic pollutant, humic acid (HA), causes many water and wastewater treatment obstacles. In this study, a novel method was proposed to degrade HA based on the low-temperature (<100 °C) catalytic air oxidation technology (LTCAO) using the NiCo-spinel (NCO) as a catalyst and the sulfite as a promoter. Sulfite enhanced the quantity of mineralized HA to 2.4 times that without sulfite assistance, and the removal rate of total organic carbon reached 93.1% within 60 min at 90 °C. HA gradually degrades into small organic molecules and is mineralized through interfacial reactions and radical paths. Sulfite plays a triple role in these reactions. Sulfite sulfonated HA destroyed its pseudomicellar structure, making HA easily oxidized. Sulfite also coordinated with NCO and promoted the internal electronic hopping conduction of NCO because of the fast electron transfer between SO32− and the h+sites, thus accelerating the electron transfer between HA and O2 mediated by NCO. In addition, the coordinated SO32− was activated to form the radical ∙SO3−, which strengthened the oxidation of HA. This study supports a simple and green method for efficiently cleaning water and wastewater rich in HA.

Radical path transformation of the Norwegian and Tasmanian salmon farming industries

ABSTRACT This paper investigates the radicalness of industry path transformation in different geographical contexts by analysing the introduction of new technological trajectories within established industry paths. We use an analytical framework based on path dependence theory to conduct a comparative case study of the introduction of offshore farming technology in the salmon farming industry in both coastal Norway and Tasmania, Australia. We show that similar points of departure can lead to different path transformation radicalness. In each case, the transformation outcome will depend on the unique interplay between agency and regional structural components during windows of opportunity. The empirical analysis supports the importance of considering agency, regional structural components and global technology trends when investigating path transformation radicalness.

Preparation of VCo-MOF@MXene composite catalyst and study on its removal of ciprofloxacin by catalytically activating peroxymonosulfate: Construction of ternary system and superoxide radical pathway

The synergistic effect between transition metal active centers and the generation of multiple removal pathways has a significant impact on the catalytic activation efficiency of peroxymonosulfate. In this work, a kind of composite catalyst was prepared by growing VCo-metal–organic frameworks (VCo-MOF) in-situ on the surface of Ti3C2Tx by a solvothermal method. The morphology and structure are characterized by Transmission Electron Microscope (TEM), Energy Dispersion Spectrum (EDS), Atomic Force Microscope (AFM), etc. Response surface methodology was used to optimize the experimental conditions. Only 5 mg catalyst can be used to effectively activate PMS and remove 96.14 % ciprofloxacin (CIP, 20 mg/L) within 30 min. The removal effect of catalyst on CIP in different actual water environment was explored. In addition, the fluorescence spectrum test also verified the effective removal of ciprofloxacin. V-Co-Ti ternary system provides a wealth of active sites for CIP removal. Cyclic voltammetry (CV) and lear sweep voltammetry (LSV) tests showed the existence of the electron transfer pathway. The results of density functional theory (DFT) calculation show that VCo-MOF@Ti3C2Tx has excellent adsorption and activation ability for PMS. At the same time, the hydrophilicity of the catalyst makes PMS more inclined to react with water molecules, which promotes the formation of a unique superoxide radical path.

Electronic Metal-Support Interaction Directing the Design of Fe(III)-Based Catalysts for Efficient Advanced Oxidation Processes by Dual Reaction Paths.

Persistent organic pollutants (POPs) have a huge impact on human health due to their high toxicity and non-degradability. It is still of great difficulty to develop highly efficient catalysts toward the degradation of POPs. Herein, it is reported that regulating electronic structure of quasi-single atomic ferric iron (Fe(III)) in the VO2 support through the electronic metal-support interaction (EMSI) is a versatile strategy to enhance the catalytic activity. Activated Fe(III) can react with peroxydisulfate (PDS) to produce both radicals and high-valent iron (HVFe) simultaneously for the efficient and fast degradation of POPs. Density functional theory (DFT) calculations prove that the influence of EMSI promotes the electrons on Fe(III) 3d-bond center moving close to the Fermi level, facilitating the charge transfer from Fe(III) to the adsorbate. Through the control experiments, both the radical path by PDS and the HVFe path aroused by the EMSI are confirmed in the POP degradation process. Consequently, the Fe/VO2 catalyst exhibits record-breaking catalytic activity with the k-value as high as 56.7, 43.3µmol s-1 g-1 for p-chlorophenol and 2,4-dichlorophenol degradation, respectively.

Structure-Based Demystification of Radical Catalysis by a Coenzyme B12 Dependent Enzyme-Crystallographic Study of Glutamate Mutase with Cofactor Homologues.

Catalysis by radical enzymes dependent on coenzyme B12 (AdoCbl) relies on the reactive primary 5'-deoxy-5'adenosyl radical, which originates from reversible Co-C bond homolysis of AdoCbl. This bond homolysis is accelerated roughly 1012-fold upon binding the enzyme substrate. The structural basis for this activation is still strikingly enigmatic. As revealed here, a displaced firm adenosine binding cavity in substrate-loaded glutamate mutase (GM) causes a structural misfit for intact AdoCbl that is relieved by the homolytic Co-C bond cleavage. Strategically interacting adjacent adenosine- and substrate-binding protein cavities provide a tight caged radical reaction space, controlling the entire radical path. The GM active site is perfectly structured for promoting radical catalysis, including "negative catalysis", a paradigm for AdoCbl-dependent mutases.

Structure-Based Demystification of Radical Catalysis by a Coenzyme B12 Dependent Enzyme-Crystallographic Study of Glutamate Mutase with Cofactor Homologues.

Catalysis by radical enzymes dependent on coenzyme B12 (AdoCbl) relies on the reactive primary 5′‐deoxy‐5′adenosyl radical, which originates from reversible Co−C bond homolysis of AdoCbl. This bond homolysis is accelerated roughly 1012‐fold upon binding the enzyme substrate. The structural basis for this activation is still strikingly enigmatic. As revealed here, a displaced firm adenosine binding cavity in substrate‐loaded glutamate mutase (GM) causes a structural misfit for intact AdoCbl that is relieved by the homolytic Co−C bond cleavage. Strategically interacting adjacent adenosine‐ and substrate‐binding protein cavities provide a tight caged radical reaction space, controlling the entire radical path. The GM active site is perfectly structured for promoting radical catalysis, including “negative catalysis”, a paradigm for AdoCbl‐dependent mutases.

Self-Reaction of Acetonyl Peroxy Radicals and Their Reaction with Cl Atoms.

The rate constant for the self-reaction of the acetonyl peroxy radicals, CH3C(O)CH2O2, has been determined using laser photolysis/continuous wave cavity ring down spectroscopy (cw-CRDS). CH3C(O)CH2O2 radicals have been generated from the reaction of Cl atoms with CH3C(O)CH3, and the concentration time profiles of four radicals (HO2, CH3O2, CH3C(O)O2, and CH3C(O)CH2O2) have been determined by cw-CRDS in the near-infrared. The rate constant for the self-reaction was found to be k = (5.4 ± 1.4) × 10-12 cm3 s-1, in good agreement with a recently published value (Zuraski, K., et al. J. Phys. Chem. A 2020, 124, 8128); however, the branching ratio for the radical path was found to be ϕ1b = (0.6 ± 0.1), which is well above the recently published value (0.33 ± 0.13). The influence of a fast reaction of Cl atoms with the CH3C(O)CH2O2 radical became evident under some conditions; therefore, this reaction has been investigated in separate experiments. Through the simultaneous fitting of all four radical profiles to a complex mechanism, a very fast rate constant of k = (1.35 ± 0.8) × 10-10 cm3 s-1 was found, and experimental results could be reproduced only if Cl atoms would partially react through H-atom abstraction to form the Criegee intermediate with a branching fraction of ϕCriegee = (0.55 ± 0.1). Modeling the HO2 concentration-time profiles was possible only if a subsequent reaction of the Criegee intermediate with CH3C(O)CH3 was included in the mechanism leading to HO2 formation with a rate constant of k = (4.5 ± 2.0) × 10-14 cm3 s-1.

Japan’s Security Reforms under Abe Shinzo: Setting the Stage for Proactivism in the Indo-Pacific?

As the longest-serving Prime Minister so far, Abe Shinzo will be remembered for the unprecedented shifts he brought about in Japan’s security policies, which will most likely have a lasting impact. From creating new institutions to fundamental changes in decision-making and from constructing a new framework for defense strategy and acquisition of offensive military capabilities to deftly managing the alliance with the US, Abe has left an indelible mark. He also came up with the Indo-Pacific construct and the Quad, which have become the key facets of regional security. Abe’s initiatives are radical, but will they lead Japan to charter an equally new radical path?

Liquid Phase Oxidation of Hydrocarbons to High-Value Chemicals in Microfluidic Reactors - Prospects and Challenges.

Liquid phase oxidation (LPO) of hydrocarbon is an industrially important process to produce petrochemicals and pharmaceuticals. It follows a free radical path having initiation, propagation and termination. The initiation step is slow while the propagation and termination steps are fast. The main challenge of such process is to control product selectivity at an appreciable conversion level. With the advancement of microfluidic reactor technology, it is possible to control the free radical steps. The present contribution critically reviewed the reaction engineering aspects of LPO of hydrocarbon, the influence of microfluidic reactor design and operation on reaction mechanism, conversion and product selectivity. It also outlines the challenges associated with microfluidic reactor operation, and prospects to apply the understanding from microfluidic reactors in few sectors. The understanding from the free radical oxidation process can also be applied to any other free radical processes.