High Reaction Rate Constant Research Articles

Coupling ultrafine plasmonic Co3O4 with thin-layer carbon over SiO2 nanosphere for dual-functional PMS activation and solar interfacial water evaporation

Photothermal materials afford growing interest in environmental governance, especially for addressing complicated environmental issues including the purification of wastewater and regeneration of freshwater together. Here, we constructed a dual-functional photothermal nanosphere by integrating ultrafine plasmonic Co3O4 (∼10 nm) into an N-doping carbon layer over silica nanosphere (SiO2@Co/C). Biocompatible dopamine coating induces the incorporation of Co precursor and activity optimization of metal species over the SiO2 nanosphere during the synthetic process. In this way, the SiO2 nanosphere maintains the stable configuration of the carbon coating thin layer to accommodate the local interfacial Co3O4 catalytic active substances. Impressively, this catalyst also owns a well-developed interconnecting N-containing network structure, unconventional redox cycle pair of Co(II)/Co(III), and significant metal-carbon interaction. A controlled thermal procedure (500–800 °C) was implemented to tune the optimized activity state of the catalyst. Under these merits, advanced oxidation process (AOPs) through activating persulfate by the obtained materials to degrade organic pollutants was performed in the presence/absence of sunlight, further validating the appreciable photothermal effect to improve the catalytic thermodynamic behavior. The reaction parameters ad anion interference were studied in detail, and SiO2@Co/C-600 can completely degrade bisphenol A (BPA) (30 mg L-1) with a high reaction rate constant of 0.722 min-1 and a low reaction activation energy of Ea (19.4 kJ/mol), and also shows superior mineralization activity for some stubborn pollutants, including oxytetracycline (OTC), 2,4-dichlorophenol and tetracycline (TC) through the reinforced photothermal approach. Besides, SiO2@Co/C-600 shows multiple functions in interfacial solar water evaporation application (1.36 kg m-2 h-1, 81.59 %), revealing great potential value of purification and regeneration of water in the complex pollution condition. This work gives the possibility for the next-generation versatile and competitive photothermal environmental governing materials.

Potencial da capacidade de retenção de um reservatório Neotropical (Estado de São Paulo, Brasil)

Abstract: Aim Man-made reservoirs lead to several changes in their downstream rivers that depend on the hydraulic characteristics of the reservoirs. However, their multiple uses can also provide facilities that influence the ecosystem services that they provide. This study addressed the potential ability of a Neotropical reservoir to trap chemical species aiming to assess the role of these ecosystems to mitigate pollution. Methods Retention capability modeling was examined for a small subtropical reservoir with high hydraulic retention time (> 100 days). The temporal ranges of 9 physical and chemical water variables over a five-year period were used to calculate the mass balance and to determine the retentive capability (alpha parameter) of the Itupararanga Reservoir (São Paulo State, Brazil). To explain the long-term mass balance of these variables, it was assumed that the reservoir is a completely mixed system with a step input. Results The highest values of parametrized alpha (high retention capability) occurred in wet months (up to 500 mm) for all variables. High reaction rate constants (k) and low hydraulic flushing suggested that sink processes prevail over the export ones, mainly for total phosphorus. The rainfall pattern showed minor importance for trapping elements. Conclusions In the Neotropics, hydraulic characteristics of the ecosystem (e.g., low area:volume ratio) are a tool for pollution management in man-made reservoirs.

Steam catalytic cracking and lump kinetics of naphtha to light olefins over nanocrystalline ZSM-5 zeolite.

This study investigates the reaction pathways and kinetics to comprehend the catalytic cracking of dodecane, a heavy naphtha model compound, over the nanocrystalline ZSM-5 catalyst in the presence and absence of steam with the aim of increasing olefin production. The nanocrystalline zeolite was characterized using XRD and BET, and the surface acidity was measured by NH3-TPD and Py-FTIR. The steam treated ZSM-5 contributed to an increase in pore volume with extra-framework alumina, resulting in highly catalytic active sites and hence higher olefin selectivity. The high conversion of dodecane (>90%) was achieved during catalytic cracking in the presence and absence of steam. In the presence of steam, the short pores of nano ZSM-5 led to an increase in the naphtha-to-olefin conversion with lesser dry gas and coke formation. The activation energies of primary cracking in the presence and absence of steam were slightly different. Lower activation energies through secondary cracking routes and higher reaction rate constants were obtained via assisted-steam catalytic cracking, promoted the selectivity towards light olefin products. Meanwhile the hydrogenation and alkylation reactions toward LPG and C5+ were favored in the absence of steam. Moreover, the ZSM-5 nano zeolite pores promoted more β-scission reactions, resulting in higher selectivity towards ethylene and dry gas.

TiO2 Nanowires on TiO2 Nanotubes Arrays (TNWs/TNAs) Decorated with Au Nanoparticles and Au Nanorods for Efficient Photoelectrochemical Water Splitting and Photocatalytic Degradation of Methylene Blue

In this study, TiO2 nanowires on TiO2 nanotubes arrays (TNWs/TNAs) and Au-decorated TNWs/TNAs nanostructures are designed and fabricated as a new type of photoanode for photoelectrochemical (PEC) water splitting. The TNWs/TNAs were fabricated on Ti folds by anodization using an aqueous NH4F/ethylene glycol solution, while Au nanoparticles (NPs) and Au nanorods (NRs) were synthesized by Turkevich methods. We studied the crystal structure, morphology, and PEC activity of four types of nanomaterial photoanodes, including TNWs/TNAs, Au NPs- TNWs/TNAs, Au NRs-TNWs/TNAs, and Au NPs-NRs-TNWs/TNAs. The TiO2 and Au-TiO2 samples exhibited pure anatase phase of TiO2 with (0 0 4), (1 0 1), and (1 0 5) preferred orientations, while Au-TiO2 presented a tiny XRD peak of Au (111) due to a small Au decorated content of 0.7 ± 0.2 at.%. In addition, the samples obtained a well-defined and uniformed structure of TNAs/TNWs; Au NPs (size of 19.0 ± 1.9 nm) and Au NRs (width of 14.8 ± 1.3 nm and length of 99.8 ± 15.1 nm) were primarily deposited on TNWs top layer; sharp Au/TiO2 interfaces were observed from HRTEM images. The photocurrent density (J) of the photoanode nanomaterials was in the range of 0.24–0.4 mA/cm2. Specifically, Au NPs-NRs- decorated TNWs/TNAs attained the highest J value of 0.4 mA/cm2 because the decoration of Au NPs and Au NRs mixture onto TNWs/TNAs improved the light harvesting capability and the light absorption in the visible-infrared region, enhanced photogenerated carriers’ density, and increased electrons’ injection efficiency via the localized surface plasmon resonance (LSPR) effect occurring at the Au nanostructures. Furthermore, amongst the investigated nanophotocatalysts, the Au NPs-NRs TNWs/TNAs exhibited the highest photocatalytic activity in the degradation of methylene blue with a high reaction rate constant of 0.7 ± 0.07 h−1, which was 2.5 times higher than that of the pristine TNWs/TNAs.

NdCoO3 nanostructures as promising candidate photocatalysts for boosting visible-light-driven photocatalytic degradation of organic pollutants

In this research, a perovskite-type neodymium cobaltite (NdCoO 3 ) was successfully fabricated by a facile and affordable co-precipitation method. Different surfactants and solvents, such as ethylene glycol, water, and ethanol, were also applied throughout this preparation for morphological studies. The outcomes demonstrated that homogenous morphology was obtained in the presence of ethylene glycol and sodium dodecyl sulfate (SDS) with an average diameter of 51.8 nm. Based on the results of UV-Vis spectroscopy, NdCoO 3 has a relevant bandgap (2.84 eV) associated with the visible region and can be used as a catalyst in the photodegradation procedure. The photocatalytic performance data showed that this compound has a high ability to degrade cationic (malachite green 79.7%) and anionic (phenol red 75.2%) dyes in high value. We investigated the effect of several parameters, such as dye types, dye concentration, and Nd 2 O 3 as a by-product on the efficiency. The scavenger test has shown that •O 2 − plays a major role in degradation. The kinetic studies have shown that the higher reaction rate constants (k=0.013 min ‒1 ) provide the best photocatalytic performance.

Performance and mechanism of co-doped Ce–Mn perovskite for degradation of tetracycline via heterogeneous photocatalysis coupled PMS oxidation

In this work, CeMn1-xMxO3 (M = Cu, Fe and Co) perovskites were synthesized and used as efficient heterogeneous catalyst for degrade of tetracycline chloride (TC-HCl) via photocatalysis coupled peroxymonosulfate (PMS) oxidation under visible-light illumination. Metal doping significantly improved the catalytic activity of perovskites. The CeMn0.6Co0.4O3/PMS/Vis system demonstrated excellent performance that 96.4% of 60 mg/L of TC-HCl was degraded within 30 min with a high reaction rate constant of 0.136 min−1, which is about 4.3 times higher than that of CeMnO3, and almost 4.4 times higher than that of pure PMS. Results confirmed the addition of Co led to mixed valence states of Mn (III)/Mn (Ⅳ) and Co (II)/Co (III) in the perovskite structure, promoting the electron transfer from the CeMn0.6Co0.4O3 to PMS. Moreover, CeMn0.6Co0.4O3 exhibited good stability over a wide pH range (3.0–11.0). The rapid transformation of Co (II)/Co (III) redox pairs is critical for PMS activation as the limiting step. Superoxide radicals (•O2−), electron (e−) and sulfate radical (SO4−•) were the dominant oxidative species responsible for removing TC-HCl. This work proposed some new insights to understand the heterogeneous reaction mechanism during PMS oxidation and photocatalytic process and promote the development of perovskites catalyst for removal of organic pollutants.

Investigating the reactivity of TiOx and BDD anodes for electro-oxidation of organic pollutants by experimental and modeling approaches

The reactivity of two non-active anodes (BDD and TiOx) for the removal of organic pollutants from water was investigated and compared. A mathematical model for electro-oxidation of organic compounds was developed by considering (i) an analytical expression of the spatial distribution of •OH concentration at non-active anodes, (ii) mass transport through the diffusion boundary layer and (iii) both direct electron transfer and •OH-mediated oxidation for degradation of organic pollutants. The model was calibrated from experimental data using, for example, terephthalic acid as •OH probe molecule or ethanol as •OH quencher during paracetamol degradation. Calculation of the fraction of current ascribed to the different possible reactions as well as a sensitivity analysis allowed for highlighting the key mechanisms and limiting phenomena. Degradation of organics occurs almost exclusively through •OH-mediated oxidation under mass transport limitation and for sufficiently high reaction rate constants. Improvement of degradation kinetics strongly depends on mass transport enhancement of organic compounds to the reaction zone at the electrode surface. Competition between the mother molecule and degradation by-products for reaction with •OH did not significantly affect degradation kinetics under mass transport limitation. Direct electron transfer can potentially become important in presence of large amounts of •OH scavengers or for organic compounds that react slowly with •OH (k < 105 m3 mol−1 s−1). Results also showed that the implementation of a suitable •OH quenching experiment required the use of a concentration of ethanol of at least 100 mM for experiments performed at 5 mA cm−2 and with a concentration of target pollutant of 0.1 mM.

Facile preparation of novel Fe-BTC@PAN nanofibrous aerogel membranes for highly efficient continuous flow degradation of organic dyes

Catalysts synthesized by immobilization of iron-based metal–organic frameworks (MOFs) on nanofibrous aerogel membranes (NFAMs) have great potential for practical applications in treatment of organic wastewaters. In this work, an ultralight Fe-BTC@polyacrylonitrile (PAN) NFAM with three-dimensional (3D) hierarchical porous structure was prepared by a green and facile in-situ growth strategy at room temperature. It was used as a catalytic membrane in a filtrationdevice for testing the degradation of methylene blue (MB). The comprehensive characterization of the Fe-BTC@PAN NFAM confirmed the in-situ growth of Fe-BTC on NFAM. Combining the advantages of both MOFs and NFAMs, the as-obtained Fe-BTC@PAN NFAM, as a heterogeneous Fenton-like catalyst, exhibited excellent catalytic performance towards degradation of methylene blue (over 98.3% of MB could be removed within 120 min with high reaction rate constant of 0.0284 min−1). The effects of H2O2 concentration, initial pH, temperature, and MB concentration on the catalytic performance were investigated. Moreover, the removalefficiency remained up to 90% over multiple cycles with negligible iron leaching (less than0.5 mg/L), which indicated catalyticstabilitywithgoodreusability. Furthermore, the plausible reaction mechanism was proposed. Hence, this study provides promising insights into the rational design of high-performance 3D MOF-based Fenton-like catalyst for treatment of organic wastewaters.

Fluorescent probes for monitoring myeloperoxidase-derived hypochlorous acid: a comparative study

MPO-derived oxidants including HOCl contribute to tissue damage and the initiation and propagation of inflammatory diseases. The search for small molecule inhibitors of myeloperoxidase, as molecular tools and potential drugs, requires the application of high throughput screening assays based on monitoring the activity of myeloperoxidase. In this study, we have compared three classes of fluorescent probes for monitoring myeloperoxidase-derived hypochlorous acid, including boronate-, aminophenyl- and thiol-based fluorogenic probes and we show that all three classes of probes are suitable for this purpose. However, probes based on the coumarin fluorophore turned out to be not reliable indicators of the inhibitors’ potency. We have also determined the rate constants of the reaction between HOCl and the probes and they are equal to 1.8 × 104 M−1s−1 for coumarin boronic acid (CBA), 1.1 × 104 M−1s−1 for fluorescein based boronic acid (FLBA), 3.1 × 104 M−1s−1 for 7-(p-aminophenyl)-coumarin (APC), 1.6 × 104 M−1s−1 for 3’-(p-aminophenyl)-fluorescein (APF), and 1 × 107 M−1s−1 for 4-thiomorpholino-7-nitrobenz-2-oxa-1,3-diazole (NBD-TM). The high reaction rate constant of NBD-TM with HOCl makes this probe the most reliable tool to monitor HOCl formation in the presence of compounds showing HOCl-scavenging activity.

Probing the Role of Cysteine Thiyl Radicals in Biology: Eminently Dangerous, Difficult to Scavenge.

Thiyl radicals are exceptionally interesting reactive sulfur species (RSS), but rather rarely considered in a biological or medical context. We here review the reactivity of protein thiyl radicals in aqueous and lipid phases and provide an overview of their most relevant reaction partners in biological systems. We deduce that polyunsaturated fatty acids (PUFAs) are their preferred reaction substrates in lipid phases, whereas protein side chains arguably prevail in aqueous phases. In both cellular compartments, a single, dominating thiyl radical-specific antioxidant does not seem to exist. This conclusion is rationalized by the high reaction rate constants of thiyl radicals with several highly concentrated substrates in the cell, precluding effective interception by antioxidants, especially in lipid bilayers. The intractable reactivity of thiyl radicals may account for a series of long-standing, but still startling biochemical observations surrounding the amino acid cysteine: (i) its global underrepresentation on protein surfaces, (ii) its selective avoidance in aerobic lipid bilayers, especially the inner mitochondrial membrane, (iii) the inverse correlation between cysteine usage and longevity in animals, (iv) the mitochondrial synthesis and translational incorporation of cysteine persulfide, and potentially (v) the ex post introduction of selenocysteine into the genetic code.

Solid Lewis acid-base pair catalysts constructed by regulations on defects of UiO-66 for the catalytic hydrogenation of cinnamaldehyde

A series of highly-defective UiO-66 were synthesized and utilized as catalyst in the hydrogenation of cinnamaldehyde (CALD) to cinnamylalcohol (CALH) in isopropanol. The physico-chemical properties of the catalysts were characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis and N2 adsorption-desorption. It was found that there are two kinds of atomic Lewis acid-base pairs existing in the defective UiO-66, exactly Zr4+-O2- and Zr4+-OH-, which are active sites for CALD hydrogenation to form CALH. UiO-66–0.3 with the most defects shows a much higher reaction rate constant, which is 5.5 times that of UiO-66–2.0, and gives the best CALD conversion of 85.5% and CALH selectivity of 94.0% at 140 ℃ after 3 h. The acid-base synergistic catalysis mechanism was proposed. Moreover, the defective UiO-66 showed good recyclability for up to 7 cycles with retention of catalytic activity as well as structural stability.

Bipolar Membranes for Ion Management in (Photo)Electrochemical Energy Conversion

Conspectus(Photo)electrochemical energy conversion is important in the development of a carbon-neutral energy economy because it can provide a pathway for mitigating the intermittency of renewable energy sources such as wind and solar. In order to operate efficiently, these technologies, which include photoelectrochemical cells, water and CO2 electrolyzers, fuel cells, and redox flow batteries, require fast charge transfer kinetics at the electrode/electrolyte interface as well as robust ion management in the electrolyte.In conventional electrolyzers and fuel cells, the electrolyte is strongly acidic or basic and ionic current is carried by H+ or OH– ions. In contrast, photoelectrodes and electrocatalysts for water splitting are often studied in buffered solutions. The question of ion balance in these systems led us to analyze the polarization losses due to ion concentration gradients in cells that employed various buffer–membrane combinations. Continuously driving the buffer ions across an ionomer membrane not only lowers the buffer capacity of an aqueous electrolyte but also introduces pH gradients that result in significant energy losses.To address the problem, we and other groups have studied the use of reverse-biased bipolar membranes (BPMs) in (photo)electrolytic cells. BPMs consist of an anion exchange layer (AEL) laminated with a cation exchange layer (CEL) and are usually equipped with a catalytic layer in between to accelerate the water dissociation reaction. At the AEL/CEL interface, water dissociates into protons and hydroxide ions, which replenish those consumed at the cathode and anode. Compared to conventional water electrolyzers with proton/anion exchange membranes (PEM/AEM), BPM electrolyzers provide the unique advantage of continuously operating the cathode and anode under different pH conditions, which is desirable when the two electrode reactions have different pH requirements.BPMs also enable the use of buffered electrolytes at pH values that are optimized for electrode stability and product selectivity in applications such as CO2 electrolysis. Product crossover losses and CO2 pumping can be dramatically reduced in BPM-based CO2 electrolyzers, relative to conventional alkaline membranes, by electrostatic repulsion (of anionic products) and electroosmotic drag (for neutral products). BPM-based gas fed CO2 electrolyzers can achieve high current density, but they suffer from low Faradaic efficiency (FE) due to the acidic local environment of the CEL. This problem can be mitigated by adding an aqueous buffering layer or by creating a weak acid cation exchange film on the CEL face of the membrane.The use of BPMs in fuel cells and redox flow batteries offers some interesting advantages. Configurations with both reverse and forward bias have been studied, but forward bias has been favored due to material compatibility, reaction kinetics, and thermodynamic considerations. The net reaction at the AEL/CEL interface is the acid–base neutralization reaction, which has a high inherent reaction rate constant, but in the BPM is limited to a nanometric space-charge layer and requires efficient catalysis to achieve high current density. Understanding the mechanism of the acid–base neutralization and the opposite process, the water dissociation reaction, will be essential for improving the performance of forward-biased BPMs. This Account reviews our current understanding of the working mechanisms of BPMs and discusses how we can use them to effectively manage ions for various (photo)electrochemical applications.

Adopting a green method for the synthesis of gold nanoparticles on cotton cloth for antimicrobial and environmental applications

In this research, a simple and green approach towards preparation of biogenic gold nanoparticles on cotton cloth (AuNPs-CC) was developed. It was found that the hydroxyl functional groups of the cellulose macromolecules, abundantly available in cotton, slowly reduced the Au ions to nanoparticles. To help accelerate the kinetic process of AuNPs formation, a Citrus limon juice concentrate was utilized. The samples were characterized by field emission scanning electron microscope (FESEM), energy-dispersive spectroscopy (EDS) and other spectroscopic methods. The FESEM images directly showed the ~22 nm size AuNPs attached to the cotton cloth fibers. The XPS and XRD confirmed the formation of biogenic AuNP over CC surface. The pristine-CC and AuNPs-CC were studied for their antibacterial properties using their different strains. Moreover, AuNPs-CC was used as a catalyst in the pollutants degradation (para- and ortho-nitrophenol) in their aqueous solutions. The AuNP-CC catalyzed the p-NP and o-NP reductions with high reaction rate constants. Moreover, the Citrus limon assisted synthesized AuNP-CC has antibacterial activities for pathogenic bacteria.

Optimization of TiO2 immobilized – Reduce graphene oxide photocatalyst toward organic compounds in aqueous medium

In this work, a one-pot hydrothermal route was synergistically applied for TiO2 immobilized reduced graphene oxide (TiO2/rGO) facilitation. The material was characterized by modern analysis methods and studied the photocatalytic performance with methylene blue (MB) in the water. The characteristic results expressed that TiO2 in truncated octahedral bipyramidal structure with 4–25 nm was disseminated onto the rGO base. Simultaneous effects of the reaction temperature, pH, adsorption time, photocatalytic time, MB concentration, and catalyst dosage on the MB photodegradation of TiO2/rGO were also conducted by full factorial experimental design according to Placket–Burman and Box–Behnken designs. At room temperature, after 2h–adsorption and photodegradation with MB concentration of 23 mg/L in pH of 10 solution and 20 mg catalyst, nearly 100% of MB was productively decomposed out of the medium with a relatively high reaction rate constant. The photocatalytic performance showed an excellent impact toward other types of organic contaminants with the above condition, indeed affirming an extensive use in wastewater treatment with organic pollutants.

The Synthesis of Pt-CNTs Nanocatalyst Promoted by Visible Light and Catalytic Reduction of &lt;i&gt;4&lt;/i&gt;-Nitrophenol

Photochemistry to prepare platinum nanoparticles (Pt NPs) is an essential way to control Pt NPs catalyst size distribution. This article reports a series of morphologically controlled syntheses of Pt NPs loaded on modified carbon nanotube (Pt-CNTs). In the synthesis, Polyethylene glycol (PEG) participates in reactions both as a reducing agent and a stabilizer. Visible light irradiation was adopted as a kinetic controlling approach. Typical 4-nitrophenol (4-NP) reduction was adopted to probe the catalytic performances. Characterizations prove that visible light irradiation is an effective way to control the reaction process. In the optimized reaction conditions, i.e., when the ratio PEG:H2O is 1:9, and the pH is 10, the as-prepared Pt NPs are consequently in a very narrow sized distribution with an average diameter of 1.29 nm. The Pt-CNTs present a high reaction rate constant of 0.624 min-1 in the catalytic reduction of 4-NP. All the research results are beneficial for exploring more green chemistry and facile photochemical approaches in the controlled preparation of Pt nanocatalysts.

Achieving excellent and durable CO2 electrolysis performance on a dual-phase fuel electrode in solid oxide electrolysis cells

Conversion of CO2 into valuable chemicals through solid oxide electrolysis cells (SOECs) is a promising technology towards efficient utilization of CO2 and reducing its emission. However, the well-established Ni-cermet fuel electrode is not applicable for high-concentration or pure CO2 electrolysis due to the Ni oxidation and coking issues. Here, we report that a novel nominal Pr0.2Ca0.8Fe0.8Ni0.2O3-δ perovskite fuel electrode, which is self-assembled into Pr(Ca)Fe(Ni)O3-δ perovskite and Ca2Fe2O5 brownmillerite dual-phase composite during the calcination process, possesses efficient CO2 electrolysis activity. The presence of Ca2Fe2O5 with abundant oxygen vacancies significantly improves CO2 chemical adsorption and activation and Pr(Ca)Fe(Ni)O3-δ serves charge carrier matrix, and consequently leads to a high CO2 reduction reaction rate constant of 1.104 × 10−4 cm−1 at 800 °C as determined by the electrical conductivity relaxation method. The electrochemical performance of pure CO2 electrolysis is investigated in model SOECs, exhibiting an excellent current density of 0.648 Acm−2 at 1.5 V and 800 °C. Moreover, the cell shows no noticeable degradation under two constant current densities of 0.421 Acm−2 at 800 °C and 0.3 Acm−2 at 700 °C for nearly a total of 300 h. The present study reveals a novel strategy to develop dual-phase Pr(Ca)Fe(Ni)O3-δ-Ca2Fe2O5 materials as a reliable electrode for pure CO2 electrolysis.

Математическое моделирование процесса гидроочистки дизельного топлива на основе кинетических характеристик его фракций

The principles of mathematical modeling of the diesel fuel hydrotreatment process as a multicomponent reaction system are considered. Feedstock containing a large number of organosulphuric components from the standpoint of increasing the level of model adequacy and calculation accuracy can be characterized by the total sulfur content in the raw material as a whole (1), the total sulfur content in pseudocomponents in the feedstock or its narrow fractions (2), the concentration of individual organosulphuric substances (3). It is shown that in cases 1 and 2, the concept of the reaction rate constant as a constant that characterizes the physico-chemical process is degenerate, and in calculations it should be considered as a kinetic characteristic that takes into account the inhomogeneity of the chemical process over time. As the hydrogenated feedstock comes into contact with the hydrogen-containing gas, the most active organosulfuric components with a high reaction rate constant are first hydrogenated on the catalyst, and at the final stage of the process, the less active components with a low reaction rate constant are hydrogenated. Examples of calculating the dependence of the kinetic characteristic and the total sulfur content in the hydrogenate in two broad fractions of diesel fuel on the time of contact of the reaction medium with the catalyst and the subsequent compounding of the fractions into diesel fuel.

Development of Sunlight-Driven Reduced Graphene Oxide (rGO)/CeO₂-CuO Nanofibrous Photocatalyst for Efficient Removal of Organic Dyes.

A hybrid nanofibrous membrane photocatalysts was developed through electrospinningcarbonization method. In this work, the hybrid membrane with p-n hetero-structure consisting of CeO₂ and CuO metal-oxide nanoparticles was prepared by a hierarchical and facile approach through electrospun technique and stabilized by hydrothermal process. The obtained heterogeneous photocatalyst membrane was studied for its catalytic properties by performing several experiments using test solutions of anionic Congo red (CR) and cationic methylene blue (MB) dyes, respectively. The as-prepared Graphene-CeO₂/CuO intercalated polyacrylonitrile nanofibrous (GCPNs) membrane is characterized by using various analytical techniques and its photocatalytic degradation properties was studied by conducting batch studies and validated using the kinetics models. Furthermore, the functional group transformation, electronic transition state, binding energy values and chemical oxidation state of the GCPNs membrane before and after degradation was investigated by spectroscopic studies. The optical properties of the GCPNs membrane was further analysed by UV-VIS diffuse reflectance spectroscopy (DRS). Also, the enhanced photo-degradation behaviour of the p-n hetero-structure due to the suppression of the recombination rate of the photogenerated electron-hole pairs was confirmed by photoluminescence studies (PL). These investigations implied that the developed photocatalyst GCPN membrane follows the pseudo first-order kinetics having higher reaction rate constant. Comprehensively, the GCPN has varying dye removal capacity of 90-98% for Congo red and 30-90% for Methylene blue in which the photocatalytic degradation capacity increases with increase in dye concentration and time. The reusability studies supported the sustainability and durability of the photocatalytic membrane for longer lifetime and practical value. Henceforth, nanotechnology-based cutting-edge technology offers novel hybrid nanomaterials having excellent properties that are pre-requisite for the development of sunlight mediated nano-photocatalytic reactors in the commercial applications.

Imaging of Hydroxyl-Radical Generation Using Dynamic Nuclear Polarization-Magnetic Resonance Imaging and a Spin-Trapping Agent.

Reactive oxygen species (ROS) play an important role in cell metabolism, but they can cause oxidative damage to biomolecules. Among ROS, the hydroxyl radical (·OH) is one of the most reactive molecules in biological systems because of its high reaction rate constant. Therefore, imaging of ·OH could be useful for evaluation of the redox mechanism and diagnosis of oxidative diseases. In vivo dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) is a noninvasive imaging method to obtain spatiotemporal information about free radicals with MRI anatomical resolution. In this study, we investigated the visualization of hydroxyl radicals generated from the Fenton reaction by combining DNP-MRI with a spin-trapping agent (DMPO: 5,5-dimethyl-1-pyrroline N-oxide) for ·OH. Additionally, we demonstrated the radical-scavenging effect using four thiol-related reagents by DNP-MRI. We demonstrated that DNP enhancement could be induced by the DMPO-OH radical using the DNP-MRI/spin-trapping method and visualized ·OH generation for the first time. Maximum DNP enhancement was observed at an electron paramagnetic resonance irradiation frequency of 474.5 MHz. Furthermore, the radical-scavenging effect was simultaneously evaluated by the decrease in the DNP image value of DMPO-OH. An advantage of our methods is that they simultaneously investigate compound activity and the radical-scavenging effect.

Investigation of the methylglyoxal scavenging kinetics of different food matrices under simulated intestinal conditions

This study aimed to evaluate the potential roles of different foods to scavenge exogenous dicarbonyl compounds under simulated gastrointestinal conditions. Four food groups having different arginine, creatine, thiol, and flavonoid contents were subjected to simulated gastric and intestinal conditions together with methylglyoxal. In comparison to control, foods from group 1 (chicken, beef and egg), group 2 (walnut, hazelnut, and kidney bean) and group 3 (broccoli, onion, garlic, and cauliflower) caused a significant (p < 0.05) decrease in the concentration of methylglyoxal under gastric conditions. Egg was found as the most efficient methylglyoxal scavenger food under gastric conditions. Changes in the concentration of methylglyoxal were monitored kinetically during the intestinal phase. All foods caused significant (p < 0.05) decreases in the concentration of methylglyoxal under intestinal conditions. Chicken, beef, and broccoli were found to scavenge more than 80% of methylglyoxal during 2 h of intestinal digestion. The reaction of methylglyoxal with scavenging compounds in foods was evaluated using an irreversible bimolecular reaction model. Reaction rate constants and initial reaction rates were calculated for each food. The highest reaction rate constant was estimated as 26.6 ± 1.38 L/mol min for egg, while the highest initial reaction rate was 3.6 ± 0.42 mM/min for chicken. Foods were ranked according to their methylglyoxal scavenging rates under intestinal conditions and their scavenging potential was associated with their scavenging content.