Key Reactive Species Research Articles

Understanding the chemical kinetics for plasma in liquid: Reaction mechanism of ethanol reforming in microwave discharge

Toward understanding the chemical nature of fuel reforming in liquid phase discharge, a novel kinetic model with being governed by both mass and energy equations was developed for the first time. The model reliability was verified by experimental results for ethanol reforming with water by microwave discharge plasma in liquid (MDPL). The reaction kinetics of ethanol in MDPL were revealed quantitatively. It illustrated that the key reactive species in the MDPL were H, OH, HCO, C and C x H y radicals, which induced the productions of H 2 , CO and hydrocarbons (CH 4 and C 2 H 2 ). The rate determining steps for ethanol conversion were identified as dehydrogenizing ethanol to C 2 H 5 O firstly, and then splitting to CH 2 O and CH 3 radicals. Those two species of CH 2 O and CH 3 governed the formation of CO and hydrocarbons respectively. In addition, the kinetic control mechanism for ethanol reforming in MDPL determined that ethanol was converted by mixed routes of pyrolysis and steam reforming at low initial ethanol molar concentration in liquid ( C e t h L <50%), and it was converted via only pyrolysis route at C e t h L >50%. Water in the liquid supplied OH radical promoting the conversion of C x H y to CO, thereby it regulated the reaction pathway transition between pyrolysis and steam reforming. The energy transfer pathway for discharge power to chemical energy, very important but never discussed for plasma reforming in liquid, was also simulated. It revealed that a very competitive energy efficiency of ∼85% for ethanol reforming was achieved in the MDPL. • Ethanol reforming was mainly induced by radicals of H, OH, HCO, C and C x H y . • Three reaction pathways for ethanol conversion in plasma were predicted. • Ethanol pyrolysis is the major reaction route for ethanol conversion. • The rate determining step was revealed as ethanol dehydrogenated to C 2 H 5 O. • An excellent energy efficiency of 85% was reached.

Strategic Design of a WO3/PdOx-Carbon Shell Composite Photocatalyst: Visible Light-Mediated Selective Hydrogenation of 5-Hydroxymethylfurfural

The development of visible light-assisted heterogeneous selective hydrogenation by utilizing solvents as a H2 source is a sustainable and energy-saving approach. Here, we have synthesized an efficient WO3/PdOx-carbon shell composite photocatalyst via the solution combustion method (SCM). The catalyst showed excellent activity for 5-hydroxymethylfurfural (HMF) hydrogenation in H2O/MeOH (3:1) under visible light (λ ≥ 420 nm) without the use of a pressurized external hydrogen support. The primary product was identified as 5-bis(hydroxymethyl)furan (BHMF) with a yield of 79.2%, which is regarded as a valuable feedstock for polymer industries. The minor hydrogenolysis product 5-methylfurfuryl alcohol (MFA) was also observed in proton NMR with a yield <20%. Our findings reveal that conversion efficiency (>95%) and selectivity (86.9%) increase drastically along with the pH range of the reaction medium, i.e., 7.5–8.2. The photocatalyst was embedded with both quantum-sized (0.6%) Pd particles (<5 nm) and PdO. After a series of experiments, we found that the uniform dimension (10 nm) of carbon shell benefits the stability of Pd particles (catalytic active site) and enhances charge carrier mobility. The photocatalyst is durable and reusable for up to more than six cycles without any significant loss in its activity. The progress of the reaction and key reactive species (•OH) were systematically investigated by proton NMR kinetic studies and electron paramagnetic resonance (EPR) spectroscopy. The possible reaction pathway was investigated and explored. These studies may contribute to serving as a cost-effective alternative method for a hydrogenating agent at an ambient condition without the use of a pressurized external hydrogen/temperature support under visible light.

Synthesis and Characterization of an α-Fe2O3-Decorated g-C3N4 Heterostructure for the Photocatalytic Removal of MO.

This study describes the preparation of graphitic carbon nitride (g-C3N4), hematite (α-Fe2O3), and their g-C3N4/α-Fe2O3 heterostructure for the photocatalytic removal of methyl orange (MO) under visible light illumination. The facile hydrothermal approach was utilized for the preparation of the nanomaterials. Powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) were carried out to study the physiochemical and optoelectronic properties of all the synthesized photocatalysts. Based on the X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance (DRS) results, an energy level diagram vs. SHE was established. The acquired results indicated that the nanocomposite exhibited a type-II heterojunction and degraded the MO dye by 97%. The degradation ability of the nanocomposite was higher than that of pristine g-C3N4 (41%) and α-Fe2O3 (30%) photocatalysts under 300 min of light irradiation. The formation of a type-II heterostructure with desirable band alignment and band edge positions for efficient interfacial charge carrier separation along with a larger specific surface area was collectively responsible for the higher photocatalytic efficiency of the g-C3N4/α-Fe2O3 nanocomposite. The mechanism of the nanocomposite was also studied through results obtained from UV-vis and XPS analyses. A reactive species trapping experiment confirmed the involvement of the superoxide radical anion (O2•−) as the key reactive oxygen species for MO removal. The degradation kinetics were also monitored, and the reaction was observed to be pseudo-first order. Moreover, the sustainability of the photocatalyst was also investigated.

Critical Review of UV-Advanced Reduction Processes for the Treatment of Chemical Contaminants in Water.

UV-advanced reduction processes (UV-ARP) are an advanced water treatment technology characterized by the reductive transformation of chemical contaminants. Contaminant abatement in UV-ARP is most often accomplished through reaction with hydrated electrons (eaq -) produced from UV photolysis of chemical sensitizers (e.g., sulfite). In this Review, we evaluate the photochemical kinetics, substrate scope, and optimization of UV-ARP. We find that quantities typically reported in photochemical studies of natural and engineered systems are under-reported in the UV-ARP literature, especially the formation rates, scavenging capacities, and concentrations of key reactive species like eaq -. The absence of these quantities has made it difficult to fully evaluate the impact of operating conditions and the role of water matrix components on the efficiencies of UV-ARP. The UV-ARP substrate scope is weighted heavily toward contaminant classes that are resistant to degradation by advanced oxidation processes, like oxyanions and per- and polyfluoroalkyl substances. Some studies have sought to optimize the UV-ARP treatment of these contaminants; however, a thorough evaluation of the impact of water matrix components like dissolved organic matter on these optimization strategies is needed. Overall, the data compilation, analysis, and research recommendations provided in this Review will assist the UV-ARP research community in future efforts toward optimizing UV-ARP systems, modeling the eaq --based chemical transformation kinetics, and developing new UV-ARP systems.

Enhanced peroxymonosulfate activation for Orange I degradation by g-C3N4/AgFeO2 composite in water

The construction of heterogeneous catalysts with high efficiency is significant for the degradation of persistent contaminants. Herein, the g-C3N4/AgFeO2 composite was fabricated and its composition, morphology and structure were systematically characterized. g-C3N4/AgFeO2 exhibited boosting peroxymonosulfate (PMS) catalytic performance on the degradation of Orange I (OI) than pure AgFeO2. It was optimized that the elimination of OI could be enhanced to 91%, with a kinetic rate of 0.076 min−1. Such enhancement was attributed to the increment of low-valent metal species (Ag0/Ag+, Fe2+/Fe3+) on AgFeO2 surface after coupling with g-C3N4, additionally, the synergy of g-C3N4 and AgFeO2 endowed the g-C3N4/AgFeO2 composite with higher conductivity and more electron transfer, thereby promoting effective PMS decomposition. The leaching of metal ions in the g-C3N4/AgFeO2/PMS system was suppressed, which brought superior reusability and stability. It was verified that 1O2、O2•-、SO4•- and •OH acting as the key reactive oxygen species contributed to the OI removal. Our findings provided valuable insights into the design of efficient and stable g-C3N4-based organometallic composites for advanced oxidation processes.

Fe Single-Atom Catalyst for Efficient and Rapid Fenton-Like Degradation of Organics and Disinfection against Bacteria.

The Fenton-like reaction has great potential in water treatment. Herein, an efficient and reusable catalytic system is developed based on atomically dispersed Fe catalyst by anchoring Fe atoms on nitrogen-doped porous carbon (Fe SA/NPCs). The catalyst of Fe SA/NPCs exhibits enhanced performance in activating peroxymonosulfate (PMS) for organic pollutant degradation and bacterial inactivation. The Fe SA/NPCs + PMS system demonstrates a high turnover frequency of 39.31 min-1 in Rhodamine B (RhB) degradation as well as a strong bactericidal activity that can completely sterilize an Escherichia coli culture within 5min. Meanwhile, the degradation activity of RhB by Fe SA/NPCs is improved up to 28 to 371-fold in comparison with the controls. Complete degradation of RhB can be achieved in 30 s by the Fe SA/NPCs + PMS system, demonstrating an efficiency much higher than most traditional Fenton-like processes. Experiments with different radical scavengers and density functional theory calculations have revealed that singlet oxygen (1 O2 ) generated on the N-coordinated single Fe atom (Fe-N4 ) sites is the key reactive species for the effective and rapid pollutant degradation and bacterial inactivation. This work innovatively affords a promising single-Fe-atom catalyst/PMS system for applying Fenton-like reactions in water treatment.

Characteristics of Volatile Organic Compounds in the Pearl River Delta Region, China: Chemical Reactivity, Source, and Emission Regions

Volatile organic compounds (VOCs) are important precursors of photochemical ozone and secondary organic aerosol (SOA). Here, hourly variations of ambient VOCs were monitored with an online system at an urban site (Panyu, PY) in the Pearl River Delta region during August–September of 2020 in order to identify reactive VOC species and major sources of VOCs, OH loss rate (LOH), SOA formation potential (SOAFP), and corresponding emission source regions. The average concentration of VOCs at PY was 31.80 ± 20.82 ppbv during the campaign. The C2–C5 alkanes, aromatics, and ≥C6 alkanes contributed for the majority of VOC, alkenes and aromatics showed the highest contribution to LOH and SOAFP. Further, m/p-xylene, propene, and toluene were found to be the top three most reactive anthropogenic VOC species, with respective contributions of 11.6%, 6.1%, and 5.8% to total LOH. Toluene, m/p-xylene, and o-xylene constituted a large fraction of calculated SOAFP. Seven major sources were identified by using positive matrix factorization model. Vehicle exhaust made the most significant contribution to VOCs, followed by liquefied petroleum gas and combustion sources. However, industrial-related sources (including industrial solvent use and industrial process emission) had the largest contribution to LOH and SOAFP. By combining source contribution with wind direction and wind speed, the regions of different sources were further identified. Based on high-resolution observation data during ozone pollution, this study clearly exhibits key reactive VOC species and the major emission regions of different VOC sources, and thus benefits the accurate emission control of VOCs in the near future.

Highly efficient UV/H2O2 technology for the removal of nifedipine antibiotics: Kinetics, co-existing anions and degradation pathways.

This study investigates the degradation of nifedipine (NIF) by using a novel and highly efficient ultraviolet light combined with hydrogen peroxide (UV/H2O2). The degradation rate and degradation kinetics of NIF first increased and then remained constant as the H2O2 dose increased, and the quasi-percolation threshold was an H2O2 dose of 0.378 mmol/L. An increase in the initial pH and divalent anions (SO42- and CO32-) resulted in a linear decrease of NIF (the R2 of the initial pH, SO42- and CO32- was 0.6884, 0.9939 and 0.8589, respectively). The effect of monovalent anions was complex; Cl- and NO3- had opposite effects: low Cl- or high NO3- promoted degradation, and high Cl- or low NO3- inhibited the degradation of NIF. The degradation rate and kinetics constant of NIF via UV/H2O2 were 99.94% and 1.45569 min-1, respectively, and the NIF concentration = 5 mg/L, pH = 7, the H2O2 dose = 0.52 mmol/L, T = 20 ℃ and the reaction time = 5 min. The ·OH was the primary key reactive oxygen species (ROS) and ·O2- was the secondary key ROS. There were 11 intermediate products (P345, P329, P329-2, P315, P301, P274, P271, P241, P200, P181 and P158) and 2 degradation pathways (dehydrogenation of NIF → P345 → P274 and dehydration of NIF → P329 → P315).

Facile synthesis of MgS/Ag2MoO4 nanohybrid heterojunction: Outstanding visible light harvesting for boosted photocatalytic degradation of MB and its anti-microbial applications

In this paper, a novel MgS/Ag 2 MoO 4 nanocomposite (NCs) was synthesized for the evaluation of photocatalytic performance and anti-microbial activity. The particle was characterized using FT-IR, PL, HR-TEM, EDAX, XRD, XPS, SAED, UV–vis DRS, ESR, and EIS. The performance of the photocatalyst was improved by shift in band gap to 2.76 eV compared to its individual counter parts. The photocatalytic performance of MgS/Ag 2 MoO 4 NCs was much better than MgS and Ag 2 MoO 4 as individual particles. The reaction rate constant for degrading MB by MgS/Ag 2 MoO 4 was 0.011 min −1 . The degradation efficiency of MgS/Ag 2 MoO 4 (90%) was about 1.5 and 2.2 times greater than bare Ag 2 MoO 4 (62%) and MgS (41%). The photocatalytic degradation efficiency remains same with 90% efficiency after performing the reusability test for six consecutive cycles under visible light irradiation and the particles maintained photo stability even after 6 cycles. The strong interactions between the interfacial surfaces are responsible for the increase in charge separation owing to the superior activity of MgS/Ag 2 MoO 4 NCs. The mechanism was established for this enhanced activity and the key reactive species, such as hydroxyl and superoxide radicals plays a major role in the photocatalytic process. The antimicrobial activity was evaluated against E. coli and B. subtilis and the activity of Ag 2 MoO 4 was good compared to NCs and MgS. The synthesized NCs are found to be good alternative as a visible light driven photocatalyst. • MgS/Ag 2 MoO 4 NCs was synthesized by fast and facile sono-chemical method. • NCs formation improved the photocatalytic activity compared to its individual counter parts. • Achieved an effective interface transfer and separation of photoinduced electrons and holes. • The generation of both super oxide and hydroxyl radicals involved in the photocatalytic degradation. • Excellent antibacterial activity shown against E. coli and B. subtilis .

An anaerobic-applicable Bi2MoO6/CuS heterojunction modified photocatalytic membrane for biofouling control in anammox MBRs: generation and contribution of reactive species

The anaerobic (anoxic) environment in anaerobic membrane bioreactors (AnMBRs) largely limits the antifouling application of aerobic-applicable photocatalysts, calling for preparation of anaerobic-applicable photocatalytic membranes, and exploration of generation and contribution mechanisms of reactive species under anaerobic (anoxic) condition. Herein, novel visible-light photocatalytic membranes (B2) were prepared by modifying pristine membranes (B0) with hollow flower-like Bi2MoO6/CuS heterojunctions to explore production and antifouling function of reactive species in anammox MBRs. During 157-d operation under waterproof lights irradiation, the average fouling cycle of B2 extended to 228.5% of B0, while their total nitrogen removal efficiencies (TNRE) were comparable and maintained at 0.85–0.9. The energy against the membrane fouling resistance were saved about 18.4% by filtering with B2. By adding scavengers of reactive species in flux recovery tests, photocatalytic generated ·OH, h+ and e− were testified to be responsible for the alleviated membrane fouling, whereas ·OH (rather than ·O2−) was qualitatively and quantitatively proved to be the key reactive oxygen species produced by B2. Compared with B0, the degradation and inactivation capabilities of reactive species on B2 brought about 47.7% lower organic foulant by decomposing protein, polysaccharide and lipid; and contributed to 76.1% lower total bacteria, 51.0% higher necrotic cells, and 29.1% higher esterase-inactivated cells. Furthermore, the photocatalytic membranes showed satisfactory stability and biocompatibility, providing powerful support for their long-term usage in MBRs as a low-carbon and eco-friendly strategy. The systematic insights into reactive species contribution for fouling alleviation by the anaerobic-applicable photocatalytic membrane offer valuable instructions for extended antifouling application of photocatalysis in AnMBRs.

S-Denitrosylase-Like Activity of Cyclic Diselenides Conjugated with Xaa-His Dipeptide: Role of Proline Spacer as a Key Activity Booster.

This study developed dipeptide-conjugated 1,2-diselenan-4-amine (1), i. e., 1-Xaa-His, as a new class of S-denitrosylase mimic. The synthesized compounds, especially 1-Pro-His, remarkably promoted S-denitrosylation of nitrosothiols (RSNO) via a catalytic cycle involving the reversible redox reaction between the diselenide and its corresponding diselenol ([SeH,SeH]) form with coexisting reductant thiols (R'SH), during which the [SeH,SeH] form as a key reactive species reduces RSNO to the corresponding thiol (RSH). Structural analyses of 1-Pro-His suggested that the peptide backbone of [SeH,SeH] is rigidly bent to form a γ-turn, possibly including an NH⋅⋅⋅Se hydrogen bond between the imidazole ring of His and selenol group, thus stabilizing the [SeH,SeH] form thermodynamically, and dramatically enhancing the catalytic activity. Furthermore, the synthetic compounds were found to prohibit S-nitrosylation-induced protein misfolding in the presence of RSNO, eventually implying their potential as a drug seed for misfolding diseases caused by the dysregulation of the S-denitrosylation system.

A comprehensive study on the heterogeneous electro-Fenton degradation of tartrazine in water using CoFe2O4/carbon felt cathode

In this study, cobalt ferrite coated carbon felt (CoFe2O4/CF) was synthesized by solvothermal method and applied as cathode for electro-Fenton (EF) treatment of tartrazine (TTZ) in water. The materials were characterized by SEM, XRD, FTIR, CV, and EIS to explore their physical, chemical, and electrical properties. The effects of solvothermal temperature and metal content on the TTZ removal were examined, showing that 220 °C with 2 mM of Co and 4 mM of Fe precursors were the best synthesis condition. Various influencing factors such as applied current density, pH, TTZ concentration, and electrolytes were investigated, and the optimal condition was found at 8.33 mA cm−2, pH 3, 50 mgTTZ L−1, and 50 mM of Na2SO4, respectively. By radical quenching test, ▪, 1O2, and HO were recognized as the key reactive oxygen species and the reaction mechanism was proposed for the EF decolorization of TTZ using CoFe2O4/CF cathode. The reusability and stability test showed that the highly efficient CoFe2O4/CF cathode is very promising for practical application in wastewater treatment, especially for dyes and other recalcitrant organic compounds to improve its biodegradability.

Simplification of plasma chemistry by means of vital nodes identification

Cold atmospheric plasmas have great application potential due to their production of diverse types of reactive species, so understanding the production mechanism and then improving the production efficiency of the key reactive species are very important. However, plasma chemistry typically comprises a complex network of chemical species and reactions, which greatly hinders identification of the main production/reduction reactions of the reactive species. Previous studies have identified the main reactions of some plasmas via human experience, but since plasma chemistry is sensitive to discharge conditions, which are much different for different plasmas, widespread application of the experience-dependent method is difficult. In this paper, a method based on graph theory, namely, vital nodes identification, is used for the simplification of plasma chemistry in two ways: (1) holistically identifying the main reactions for all the key reactive species and (2) extracting the main reactions relevant to one key reactive species of interest. This simplification is applied to He + air plasma as a representative, chemically complex plasma, which contains 59 species and 866 chemical reactions, as reported previously. Simplified global models are then developed with the key reactive species and main reactions, and the simulation results are compared with those of the full global model, in which all species and reactions are incorporated. It was found that this simplification reduces the number of reactions by a factor of 8–20 while providing simulation results of the simplified global models, i.e., densities of the key reactive species, which are within a factor of two of the full global model. This finding suggests that the vital nodes identification method can capture the main chemical profile from a chemically complex plasma while greatly reducing the computational load for simulation.

Preparation and photocatalytic antibacterial mechanism of porous metastable β-Bi2O3 nanosheets

Effective and safe application of antibacterials has always been an important aspect for their usage. High-efficiency photocatalytic technology driven by visible light for antibacterial action constitutes a practical solution for antibacterial agents and will not harm the human body or the environment. While most studies on β-Bi2O3 materials with good photocatalytic properties under visible light are conducted in the field of optoelectronics, their potential and mechanism as photocatalytic antibacterial agents have not yet been fully explored. Herein, we report the performance of sheet-like metastable β-Bi2O3 material with rich oxygen vacancies and high electron-hole separation efficiency in antibacterial processes, as well as a preliminary exploration of its antibacterial mechanism. The results revealed that the antibacterial activity of the product against E. coli greatly improved in comparison with commercially available α-Bi2O3 owing to its excellent structure and optical properties. In addition, gradient experiments and scavenger experiments have confirmed that the main antibacterial effect of β-Bi2O3 originates from reactive oxygen species (ROS), and the superoxide radical, ·O2−, of generated ROS is the key reactive species in the antibacterial process. Through the detection of lipid peroxidation and bacterial respiratory-chain dehydrogenase activity, several pathways were identified for the excellent antibacterial activity of the product.

Oceanic phytoplankton are a potentially important source of benzenoids to the remote marine atmosphere

Benzene, toluene, ethylbenzene and xylenes can contribute to hydroxyl reactivity and secondary aerosol formation in the atmosphere. These aromatic hydrocarbons are typically classified as anthropogenic air pollutants, but there is growing evidence of biogenic sources, such as emissions from plants and phytoplankton. Here we use a series of shipborne measurements of the remote marine atmosphere, seawater mesocosm incubation experiments and phytoplankton laboratory cultures to investigate potential marine biogenic sources of these compounds in the oceanic atmosphere. Laboratory culture experiments confirmed marine phytoplankton are a source of benzene, toluene, ethylbenzene, xylenes and in mesocosm experiments their sea-air fluxes varied between seawater samples containing differing phytoplankton communities. These fluxes were of a similar magnitude or greater than the fluxes of dimethyl sulfide, which is considered to be the key reactive organic species in the marine atmosphere. Benzene, toluene, ethylbenzene, xylenes fluxes were observed to increase under elevated headspace ozone concentration in the mesocosm incubation experiments, indicating that phytoplankton produce these compounds in response to oxidative stress. Our findings suggest that biogenic sources of these gases may be sufficiently strong to influence atmospheric chemistry in some remote ocean regions.

Ti-Catalyzed and -Mediated Oxidative Amination Reactions.

Titanium is an attractive metal for catalytic reaction development: it is earth-abundant, inexpensive, and generally nontoxic. However-like most early transition metals-catalytic redox reactions with Ti are difficult because of the stability of the high-valent TiIV state. Understanding the fundamental mechanisms behind Ti redox processes is key for making progress toward potential catalytic applications. This Account details recent progress in Ti-catalyzed (and -mediated) oxidative amination reactions that proceed through formally TiII/TiIV catalytic cycles.This class of reactions is built on our initial discovery of Ti-catalyzed [2 + 2 + 1] pyrrole synthesis from alkynes and azobenzene, where detailed mechanistic studies have revealed important factors that allow for catalytic turnover despite the inherent difficulty of Ti redox. Two important conclusions from mechanistic studies are that (1) low-valent Ti intermediates in catalysis can be stabilized through coordination of π-acceptor substrates or products, where they can act as "redox-noninnocent" ligands through metal-to-ligand π back-donation, and (2) reductive elimination processes with Ti proceed through π-type electrocyclic (or pericyclic) reaction mechanisms rather than direct σ-bond coupling.The key reactive species in Ti-catalyzed oxidative amination reactions are Ti imidos (Ti≡NR), which can be generated from either aryl diazenes (RN═NR) or organic azides (RN3). These Ti imidos can then undergo [2 + 2] cycloadditions with alkynes, resulting in intermediates that can be coupled to an array of other unsaturated functional groups, including alkynes, alkenes, nitriles, and nitrosos. This basic reactivity pattern has been extended into a broad range of catalytic and stoichiometric oxidative multicomponent coupling reactions of alkynes and other reactive small molecules, leading to multicomponent syntheses of various heterocycles and aminated building blocks.For example, catalytic oxidative coupling of Ti imidos with two different alkynes leads to pyrroles, while stoichiometric oxidative coupling with alkynes and nitriles leads to pyrazoles. These heterocycle syntheses often yield substitution patterns that are complementary to those of classical condensation routes and provide access to new electron-rich, highly substituted heteroaromatic scaffolds. Furthermore, catalytic oxidative alkyne carboamination reactions can be accomplished via reaction of Ti imidos with alkynes and alkenes, yielding α,β-unsaturated imine or cyclopropylimine building blocks. New catalytic and stoichiometric oxidative amination methods such as alkyne α-diimination, isocyanide imination, and ring-opening oxidative amination of strained alkenes are continuously emerging as a result of better mechanistic understanding of Ti redox catalysis.Ultimately, these Ti-catalyzed and -mediated oxidative amination methods demonstrate the importance of examining often-overlooked elements like the early transition metals through the lens of modern catalysis: rather than a lack of utility, these elements frequently have undiscovered potential for new transformations with orthogonal or complementary selectivity to their late transition metal counterparts.

Life Cycle Assessment of Nitrogen Circular Economy-Based NOx Treatment Technology

Humans are significantly perturbing the global nitrogen cycle, leading to excess reactive nitrogen in the environment. Nitrogen oxides as a key reactive nitrogen species are mainly controlled by selective non-catalytic reduction and selective catalytic reduction. Converting nitrogen oxides to ammonia, defined as ReNOx, emerges as an alternative method under a disparate design concept. However, little is known about its overall environmental performance. In this study, we conducted for the first time a life cycle assessment of ReNOx. Compared with the eco-index in the condition of 200 °C with a conversion rate of 95%, it would increase substantially in the condition of 160 °C with a conversion rate of 80% and in the case without a sound NH3 treatment. Feedstock format change, adsorption material performance deterioration, and recovery rate decline would increase the eco-index by 8%, 12%, and 18%, respectively. The eco-index was decreased by 31% in the optimized scenario with a renewable energy source and an increased conversion rate. The environmental impacts were compared with traditional methods at impact, damage, and eco-index levels. Finally, the implications on process arrangement in the flue gas system, the externality for power generation, and the contribution to the nitrogen circular economy were examined. The results can serve as a reference for its developers to improve the technology from the environmental perspective.

Coal fly ash-based copper ferrite nanocomposites as potential heterogeneous photocatalysts for wastewater remediation

Coal fly ash (CFA) based-copper ferrite nanocomposites were fabricated, characterized, and applied for the photocatalytic degradation of Methyl Orange (MO) dye. The hydrothermal synthesis route was opted for the fabrication of pristine copper ferrite nanoparticles and its CFA nanocomposites. The prepared photocatalysts were analyzed in terms of structural, surface morphology, chemical state analysis, elemental composition, and optical response. The photocatalytic activity of nanocomposites was investigated sequentially under ultraviolet light (254 nm) and influencing parameters (pH, H2O2 dose, photocatalyst content, dye initial concentration, irradiation time) were studied. The optimized conditions for photocatalytic degradation were found at pH = 5, composite dose = 100 mg/L, H2O2 = 10 mM using CFA nanocomposite and the dye was efficiently degraded within 60 min. The best degradation efficiency of ~98% was achieved using CFA-CuFe2O4 (1:1) under the optimized conditions. The key reactive species (OH, h+, and e−) for photocatalytic degradation were determined by a radical scavenging experiment and OH radicals were found to be the most effective ones. The kinetic study of Fenton oxidation processes was conducted using Behnajady-Modirshahla-Ghanbery (BMG) kinetic model. Response surface methodology was the statistical tool for the assessment of interaction effect among experimental variables.

Hydrogen peroxide is necessary during tail regeneration in juvenile axolotl.

Hydrogen peroxide (H2 O2 ) is a key reactive oxygen species (ROS) generated during appendage regeneration among vertebrates. However, its role during tail regeneration in axolotl as redox signaling molecule is unclear. Treatment with exogenous H2 O2 rescues inhibitory effects of apocynin-induced growth suppression in tail blastema cells leading to cell proliferation. H2 O2 also promotes recruitment of immune cells, regulate the activation of AKT kinase and Agr2 expression during blastema formation. Additionally, ROS/H2 O2 regulates the expression and transcriptional activity of Yap1 and its target genes Ctgf and Areg. These results show that H2 O2 is necessary and sufficient to promote tail regeneration in axolotls. Additionally, Akt signaling and Agr2 were identified as ROS targets, suggesting that ROS/H2 O2 is likely to regulate epimorphic regeneration through these signaling pathways. In addition, ROS/H2 O2 -dependent-Yap1 activity is required during tail regeneration.

Hydrogen peroxide enhanced sonophotocatalytic degradation of acid orange 7 in aqueous solution: optimization by Box–Behnken design

AbstractBACKGROUNDSonophotocatalysis has gained great attention for research into practical applications to treat refractory organic dye from wastewater. However, its degradation efficiency needs to be improved further. To further enhance the sonophotocatalytic performance, here we report a novel hydrogen peroxide (H2O2)‐assisted titania (TiO2)‐based sonophotocatalyic system (H2O2‐US‐UV/TiO2) for degradation of acid orange 7 (AO7).RESULTSEffects of operating parameters including catalyst dosage, concentration of the oxidative agents and initial pH were analyzed through a response surface method coupled with Box–Behnken experimental design (RSM‐BBD) and experiments. Introducing H2O2 into the US‐UV/TiO2 system can significantly enhance AO7 removal. A quadratic model was proposed for predicting AO7 degradation using the RSM‐BBD method, and the statistical significance of the model was confirmed by ANOVA. The real AO7 removal efficiency (95.8%) under experimental conditions of 0.5 g L−1 TiO2, 4 mmol L–1 H2O2, and initial pH 3 was comparable with the predicated value (98.6%) obtained from this model. Quenching tests revealed that the hydroxyl radical (˙OH) was the key reactive species in the sonophotocatalytic system. Degradation products including 2‐naphthol, 4‐carboxylphenylglycine, cinnamic acid and 1,10‐Decanediol were identified.CONCLUSIONAdding H2O2 improved the degradation performance of AO7 in the US‐UV/TiO2 system; H2O2 concentration was a more significant experimental factor than initial pH and TiO2 dosage. A degradation pathway of AO7 removal was suggested according to results of liquid chromatography‐mass spectrometry. The novel hybrid H2O2‐US‐UV/TiO2 system can be utilized as an efficient process for recalcitrant dye wastewater treatment. © 2021 Society of Chemical Industry (SCI).