Specific Reaction Rate Research Articles

Rapid Iodination Kinetic Studies of o-Toluidine in Aqueous Medium: A Pharmacokinetic Insight from QSAR and Molecular Docking of its Iodo Product with Cytochrome P450

The kinetic data of uncatalyzed rapid iodination of o-toluidine using molecular iodine in aqueous medium was investigated by employing hydrodynamic voltammetry (HV) technique. The frequency factor, activation energy and entropy change accompanying the reaction were evaluated. The reaction followed second order kinetics that had a half-life of 90 s and specific reaction rate 888.87 M s–1 at 22.1 ºC. The iodo product was formed via the green route in the aqueous solvent. The physico-chemical characteristics, lipophilicity, water solubility and pharmacokinetic parameters were derived by QSAR analysis. The docking of the iodo product with cytochrome P450 exhibited steric and physiological complementarity of the ligand-protein interface through hydrogen bonding and pi-pi stacking interactions, indicating that the product exhibited metabolic activity was similar to the existing drugs.

Mechanistic understanding of oxygen spillover enables efficient propane combustion over Pt/AlSOx catalyst

Understanding of the mechanism of saturated alkanes catalytic combustion is crucial for the petrochemical industrial exhaust elimination. Noble metals are commonly proposed to be the active sites for C–H bond activation of saturated alkanes, whereas the critical role of support is largely underestimated. Herein, we reveals a novel pathway for propane activation and combustion on acidic support of Pt catalyst, driven by oxygen spillover, which differs significantly from previously reported reaction mechanisms. Specifically, the Pt/AlSOx-I catalyst was prepared by pyrolyzing the Al2(SO4)3 sol–gel to obtain the acidic micro-mesoporous AlSOx support, followed by loading the Pt active sites using wetness impregnation. In comparison to Pt catalysts supported by Al2O3 nanoparticles (10 nm) or commercially available common γ-Al2O3, the Pt/AlSOx-I catalyst demonstrates superior catalytic activity for propane combustion. It is found that gaseous oxygen species activated on Pt active sites spillovers to acidic support of Pt/AlSOx-I and then drives propane to activation and further oxidation on acidic support, thereby remarkably decreasing the apparent activation energies (Ea) from 112.4 to 72.0 kJ·mol−1. Kinetic results suggest that the negative effect of oxygen competitive adsorption is weakened because propane can be activated on the acidic AlSOx support. Additionally, high proportion of metallic Pt species benefits to gaseous oxygen activation as observed on Pt/AlSOx-R, leading to the further increased catalytic activity with highest specific mass reaction rate of 170.2 μmol gPt−1 s−1 and TOFPt of 0.289 s−1 at 220 °C. Our primary results provide novel insights into revealing the reaction mechanism of saturated alkanes combustion on dual active sites.

Oxygen vacancy-mediated Mn2O3 catalyst with high efficiency and stability for toluene oxidation

Oxygen vacancy engineering in transition metal oxides is an effective strategy for improving catalytic performance. Herein, defect-enriched Mn2O3 catalysts were constructed by controlling the calcination temperature. The high content of oxygen vacancies and accompanying Mn4+ ions were generated in Mn2O3 catalysts calcined at low temperature, which could greatly improve the low-temperature reducibility and migration of surface oxygen species. DFT theoretical calculations further confirmed that molecular oxygen and toluene were easily adsorbed over defective α-Mn2O3 (222) facets with an energy of −0.29 and −0.48 eV, respectively, and corresponding OO bond length is stretched to 1.43 Å, resulting in the highly reactive oxygen species. Mn2O3-300 catalyst with abundant oxygen vacancies exhibited the highest specific reaction rate and lowest activation energy. Furthermore, the optimized catalyst possessed the outstanding stability, water tolerance and CO2 yield. In comparison with the fresh Mn2O3-300 catalyst, the physical structure and surface property of the used catalyst remained almost unchanged regardless of whether undergoing the stability test at consecutive catalytic runs as well as high temperature, and water resistance test. In situ DRIFTS spectra further elucidated that introducing the water vapor had little effect on the reaction intermediates, indicating the excellent durability of the defect-enriched catalyst.

Investigating the Inhibitory Factors of Sucrose Hydrolysis in Sugar Beet Molasses with Yeast and Invertase

Sugar beet molasses is a low-value byproduct from the sugar industry. It contains significant amounts of sucrose (approx. 50% (w/w)), which can be used for many different applications, for example, as feedstock for the production of fuel (as ethanol) and biobased chemicals such as 5-hydoxymethyl furfural (HMF). To produce platform chemicals, sucrose is hydrolyzed into its monomeric C6 sugars: glucose and fructose. When comparing the hydrolysis rates of molasses with a pure sucrose solution, the specific reaction rate is much slower (Qp/x,60min = 93 and 70 gprod L−1 h−1 gcell−1 for pure sucrose and crude molasses, respectively) at the same sucrose concentration (300 g/L) and process conditions. To clarify why molasses inhibits the enzymatic hydrolysis rate, the influence of its viscosity and inorganic and organic composition was investigated. Also, the effects of molasses and treated molasses on pure enzymes, invertase (from Saccharomyces cerevisiae, 0.05 mg/mL), compared with hydrolysis using whole cells of Baker’s yeast (3 mg/mL), were tested. The results indicate an inhibitory effect of potassium (Qp/x,60min = 76 gprod L−1 h−1 gcell−1), generally at high salt concentrations (Qp/x,60min = 67 gprod L−1 h−1 gcell−1), which could be correlated to the solution’s high salt concentrations and possibly the synergistic effects of different ions when applying concentrations that were four times that in the molasses. Also, the viscosity and sucrose purity seem to have an effect, where pure sucrose solutions and thick juice from the sugar mill yielded higher hydrolysis rates (Qp/x,60min = 97 gprod L−1 h−1 gcell−1) than molasses-type solutions with a higher viscosity (Qp/x,60min = 70–74 gprod L−1 h−1 gcell−1). Attempting to further understand the effects of different components on the invertase activity, an in silico investigation was performed, indicating that high salt concentrations affected the binding of sucrose to the active site of the enzyme, which can result in a lower reaction rate. This knowledge is important for future scale-up of the hydrolysis process, since reduced hydrolysis rates require larger volumes to provide a certain productivity, requiring larger process equipment and thereby higher investment costs.

Integrated influence of sulfide modification on the reactivity of nanoscale zero-valent iron towards decabromodiphenyl ether under an electromagnetic field

Individual application of sulfide modification and electromagnetic field (EMF) can enhance the reactivity of nanoscale zero-valent iron (nZVI), yet the potential of both in combination is not clear. This work found that the reactivity of nZVI towards decabromodiphenyl ether was significantly enhanced by the combined effect of sulfidation and EMF. The specific reaction rate constant of nZVI increased by 7 to 10 times. A series of characterization results revealed that the sulfidation level not only affects the inherent reactivity but also the magnetic-induced heating (MIH) and corrosion (MIC) of nZVI. These collectively influence the degradation efficiency of nZVI under EMF. Sulfidation generally diminished the MIH effect. The low degree of sulfidation (S/Fe = 0.1) slightly reduced the MIC effect by 21.4%. However, the high degree of sulfidation (S/Fe = 0.4) led to significantly enhanced MIC effect by 107.1%. For S/Fe = 0.1 and 0.4, the overall enhancement in the reactivity resulting from EMF was alternately dominated by the contributions of MIH and MIC. This work provides valuable insights into the MIH and MIC effects about the sulfidation level of nZVI, which is needed for further exploration and optimization of this combined technology.

Mesoporous Si-WO3-supported Pt catalysts with high catalytic performance and excellent water resistance for toluene oxidation

Reducing emissions of volatile organic compounds (VOCs) is an integral part of improving the quality of the atmospheric environment. Catalytic oxidation has become an effective means of treating low and medium concentration VOCs exhausts due to its advantages in terms of removal efficiency, energy saving and environmental protection. Due to the unique inherent properties of supported precious metal catalysts, they show good catalytic efficiency in VOCs emission reduction. In this study, the mesoporous Si-WO3 support was first synthesized by the P123-assisted sol-gel method, and the xPt/Si-WO3 catalysts with the actual loadings (x = 0.19, 0.48, and 0.81 wt%) of Pt nanoparticles (NPs) were then obtained, physicochemical properties of these materials were characterized using a variety of techniques, and their catalytic activities and water resistance for the oxidation of toluene were evaluated. The results showed that Pt NPs with an average particle size of 2.3−3.3 nm were highly dispersed on the mesoporous Si-WO3 support, and the 0.81Pt/Si-WO3 sample exhibited the highest catalytic activity for toluene oxidation at a space velocity of 20,000 mL/(g h) (T50% = 167 °C and T90% = 180 °C; specific reaction rate at 160 °C = 8.54 µmol/(gPt s), turnover frequency (TOFPt) at 160 °C = 1.67 × 10−3 s−1, and apparent activation energy = 45 kJ/mol). The good catalytic performance of 0.81Pt/Si-WO3 was associated with its large surface area, well dispersed Pt NPs, high adsorbed oxygen species concentration, large toluene adsorption capacity, and strong interaction between Pt NPs and mesoporous Si-WO3. The 0.81Pt/Si-WO3 sample possessed excellent water resistance, and the introduction of 5 vol% or 10 vol% water vapor to the reaction system enhanced toluene oxidation since part of water vapor participated in the oxidation of toluene. In addition, the toluene oxidation pathway might obey the sequence of (adsorbed toluene + adsorbed oxygen species) → benzyl alcohol → (benzoic acid and benzaldehyde) → maleic anhydride → (carbon dioxide and water).

Impact of Pickering Emulsions Composition on Lipase Catalyzed Peroxyacetic Acid Synthesis

AbstractDue to the need for environmental protection and sustainability, there has been a rising need to replace the traditionally harsh oxidative functionalization process, which is essential for syntheses of various organic compounds, by biocatalysis. However, the investigated alternative processes are still challenged with enzyme instability and/or low specific reaction rate. Due to these still existing challenges and the recognition of Pickering emulsions as an efficient platform for continuous biphasic biocatalysis, the first, enzymatic step of the lipase catalyzed oxidative functionalization was investigated in bioactive Pickering emulsions. The study focused on the impact of Pickering emulsion composition such as the volume phase fraction, type and concentration of the nanoparticles and enzymes on continuous peroxyacetic acids synthesis. The type of nanoparticles used and Candida antarctica lipase B concentration significantly impacted the process while the other named parameters only had a marginal influence.

Identification of reaction intermediates in the decomposition of formic acid on Pd.

Uncovering the role of reaction intermediates is crucial to developing an understanding of heterogeneous catalysis because catalytic reactions often involve complex networks of elementary steps. Identifying the reaction intermediates is often difficult because their short lifetimes and low concentrations make it difficult to observe them with surface sensitive spectroscopic techniques. In this paper we report a different approach to identify intermediates for the formic acid decomposition reaction on Pd(111) and Pd(332) based on accurate measurements of isotopologue specific thermal reaction rates. At low surface temperatures (∼400 K) CO2 formation is the major reaction pathway. The CO2 kinetic data show this occurs via two temporally resolved reaction processes. Thus, there must be two parallel pathways which we attribute to the participation of two intermediate species in the reaction. Isotopic substitution reveals large and isotopologue specific kinetic isotope effects that allow us to identify the two key intermediates as bidentate formate and carboxyl. The decomposition of the bidentate formate is substantially slower than that of carboxyl. On Pd(332), at high surface temperatures (643 K to 693 K) we observe both CO and CO2 production. The observation of CO formation reinforces the conclusion of calculations that suggest the carboxyl intermediate plays a major role in the water-gas shift reaction, where carboxyl exhibits temperature dependent branching between CO2 and CO.

Aqueous phase selective C[dbnd]O hydrogenation of cinnamaldehyde over bimetallic RuCo catalysts with electronic and geometric modification

Aqueous phase selective hydrogenation of cinnamaldehyde (CALD), as a representative α,β-unsaturated aldehyde, into cinnamyl alcohol (CALA) has been investigated over monometallic Ru and bimetallic RuCo catalysts on pristine h-BN support. Using water as the solvent, the optimal 0.5%Ru-1.1%Co/h-BN catalyst exhibits 510 h−1 specific reaction rate and 78.9 % CALA selectivity as well as good recycling stability at 100 °C. Based on the structure characterizations of catalysts, metal nanoparticles consisting of metallic Ru0 and partially oxidized Ruδ+ sites are uniformly dispersed on h-BN thin sheets. In comparison to monometallic catalysts, additive Co metals in bimetallic RuCo/h-BN catalysts play significant geometric and electronic modification roles on Ru active sites depending on the Ru/Co ratio, and therefore remarkably enhances the preferential activation of CALD CO bond and selectivity of CALA product as well as accelerates the catalytic reaction. Furthermore, the hydrogen dissociative activation ability of various Ru and RuCo catalysts was evaluated, while the superior catalytic performance in water than other commonly used solvents was also clarified and discussed.

Automatic mechanism generation for the combustion of advanced biofuels: A case study for diethyl ether

AbstractAdvanced biofuels have the potential to supplant significant fractions of conventional liquid fossil fuels. However, the range of potential compounds could be wide depending on selected feedstocks and production processes. Not enough is known about the engine relevant behavior of many of these fuels, particularly when used within complex blends. Simulation tools may help to explore the combustion behavior of such blends but rely on robust chemical mechanisms providing accurate predictions of performance targets over large regions of thermochemical space. Tools such as automatic mechanism generation (AMG) may facilitate the generation of suitable mechanisms. Such tools have been commonly applied for the generation of mechanisms describing the oxidation of non‐oxygenated, non‐aromatic hydrocarbons, but the emergence of biofuels adds new challenges due to the presence of functional groups containing oxygen. This study investigates the capabilities of the AMG tool Reaction Mechanism Generator for such a task, using diethyl ether (DEE) as a case study. A methodology for the generation of advanced biofuel mechanisms is proposed and the resultant mechanism is evaluated against literature sourced experimental measurements for ignition delay times, jet‐stirred reactor species concentrations, and flame speeds, over conditions covering φ = 0.5–2.0, P = 1–100 bar, and T = 298–1850 K. The results suggest that AMG tools are capable of rapidly producing accurate models for advanced biofuel components, although considerable upfront input was required. High‐quality fuel specific reaction rates and thermochemistry for oxygenated species were required, as well as a seed mechanism, a thermochemistry library, and an expansion of the reaction family database to include training data for oxygenated compounds. The final DEE mechanism contains 146 species and 4392 reactions and in general, provides more accurate or comparable predictions when compared to literature sourced mechanisms across the investigated target data. The generation of combustion mechanisms for other potential advanced biofuel components could easily capitalize on these database updates reducing the need for future user interventions.

Controllable hydrogen release from NH3BH3 hydrolysis over Ru ultrafine particles stabilized on agriculture waste-derived carbon

Simultaneously considering cost, safety and catalytic efficiency, the development of a cost-effective and high-performance catalyst is significant and challenging for controllable hydrogen release from ammonia borane (AB, NH3BH3) hydrolysis. In this work, Ru ultrafine particles are evenly and firmly stabilized on wheat straw-derived porous carbon through a facile procedure. Specifically, attributed to the abundant co-doping of heteroatoms (namely, N and O) and suitable hierarchical porous structure of WSC-1.0 with large specific surface area (1000 m2 g−1), which is prepared with a mass ratio of 1: 1 for K2CO3 to the pre-carbonized biomass waste, as well as high dispersion (32.6%) of Ru ultrafine particles with an average size of 1.4 ± 0.3 nm, the optimal Ru/WSC-1.0 displays exceptional catalytic performance in the hydrolysis of AB. The corresponding turnover frequency (TOF) and specific reaction rate (rB) are 167.7 min−1 and 4.07 × 104 mL min−1 gRu−1, respectively, and the apparent activation energy is 40.94 kJ mol−1. Upon adding NaOH (1.0 M), the hydrolysis rate can be remarkably accelerated (TOF = 401.4 min−1, rB = 9.75 × 104 mL min−1 gRu−1). The isotope experiments show that the scission of an O-H bond in H2O by oxidative addition is the decisive step in this reaction. Impressively, the effective “on-off” control for the hydrolytic dehydrogenation reaction over Ru/WSC-1.0 can be easily realized by introducing certain amounts of Zn(NO3)2 and EDTA-2Na, separately. Our work delivers a facile approach for efficient utilization of agricultural wastes and offers a robust and cost-effective catalyst for the controllable hydrogen evolution from AB hydrolysis.

Fluidized bed reactor for 4-chlorophenol photodegradation via solar and visible radiation using ZnO/g-C3N4/carbon xerogel as a photocatalyst

This study investigates the feasibility of employing a fluidized bed reactor for the degradation of 4-chlorophenol (4CP), considering multiple operational parameters (type of radiation, fresh inlet flow rate and recycle flow rate). The selection of the ZnO/g-C3N4/carbon xerogel as photocatalyst, a choice motivated by the improved charge transfer and increased catalyst activity under visible radiation provided by the presence of carbon xerogel and g-C3N4, was previously determined through tests conducted in a jacketed batch reactor under visible radiation, in which the ternary material efficiency was compared to their constituting counterpart materials. The semiconductors constituting the unary, binary, and ternary materials were chosen based on considerations of availability, sustainability, and abundance in nature. The use of the proposed fluidized bed reactor brings advantages in scalability, distribution of irradiated light and overall costs when compared to commonly used batch reactors, whereas the investigation of the flow parameters involved in such process is of great importance to understand and optimize the efficiency of the pollutant degradation process. Regarding the ternary photocatalyst, X-ray diffractometry (XRD) revealed the presence of zinc oxide's hexagonal crystalline structure. Moreover, additional characterization using Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS) confirmed the presence not only of ZnO but also of carbon xerogel and g-C3N4 in the composite. From the photodegradation experiments, it was determined that the optimal fresh inlet flow rate to achieve the best degradation, as well as the recycle flow rate for this purpose, were 0.07 and 25 L h−1, respectively. Mathematical simulations described that the model that best fits the system's behavior considers the specific reaction rate as dependent on the concentration of the catalyst in the medium.

ZIF-8 incorporated CeO2-CdS quantum dots @ 2D g-C3N4 nanosheets as a staggered type II heterojunction for decolouration of a set of dyes

Dye toxins, emitted by industries, pose a significant threat to living beings and aquatic life by absorbing light radiation and inhibiting the growth of essential bacteria and microbes, making their removal crucial for health of living beings and flora and fauna. This research endorsed a hydrothermal synthetic route for the photocatalyst CeO2/CdS/g-C3N4 @ZIF8 (or CCdGZ) fabrication to remove a set of hazardous dyes from wastewater streams. Corresponding Analytical methods evaluated the successfully developed CCdGZ photocatalyst's structural, morphological, and compositional properties. Powder X-ray photoelectron (PXRD) analysis showed the structural properties of CCdGZ and the quantum dot nature of the CeO2-CdS hybrid in the heterostructure with a crystallite size of 0.16 nm. The photocatalyst's optical responses were examined using UV–vis spectrophotometry and the UV-diffuse reflectance spectroscopy (UV-DRS) technique. Tauc's plot determined the energy band gap of the CCdGZ to be ∼2.64 eV, confirming a slight modification of the valence band (VB) and conduction band (CB) edges of the moieties CeO2, CdS, and g-C3N4. Thus, the heterostructure's moieties synergised to produce photocatalytic degradation. Under visible light irradiation, the photocatalyst CCdGZ photodegraded Victoria blue R (VBR) dye by 96.54% in 55 min. Photodegradation followed pseudo-first-order kinetics with a specific reaction rate of 0.06159 min−1 {coefficient of determination (R2) = 0.99847}. The corresponding TOC removal was 83.27%, while COD got reduced to 78.98% of its initial magnitude. Multiple reaction parameters, heterostructure reusability (over 89% efficient till the 5th run), the scavengers' experiment, inorganic ion effects, and water matrices were also evaluated. The study concludes with a photocatalytic reaction mechanism that explains the moieties' roles. This study designs a heterostructure photocatalyst that disintegrates emerging non-degradable organic pollutants in the UV–visible range, is recoverable, and has better photostability.

Engineering Mn–O strength in manganese oxide catalyst to enhance propane catalytic oxidation

Developing highly active and thermally stable transition-metal-oxide catalysts for light alkane catalytic oxidation is of great importance but very challenging. In the work, the catalytic performance for propane deep oxidation was significantly enhanced on the Mn1NixOy solid solution catalyst by weakening the Mn–O bond strength of manganese oxide. The characterization results combined with DFT calculations demonstrated that the introduction of Ni could create additional defect sites, resulting in a significant improvement of the adsorption and the activation of both propane and oxygen molecules. The optimal Mn1Ni0.15Oy catalyst exhibits abundant oxygen vacancies with low MnO bond strength, high redox ability and oxygen mobility, which account for its superior activity. Specifically, the specific reaction rate on Mn1Ni0.15Oy is three times higher than that on pure Mn2O3. Moreover, a Mn1Ni0.15Oy/cordierite monolithic catalyst was made by wash-coating method, and exhibited remarkable catalytic performance and stability on catalytic oxidation of propane during the 45 days (1080 h) on stream, even after tens of high temperature thermal shocks (up to 650 ℃), which declared to be satisfied for practical industrial applications. This work will shed light on designing high-efficiency and long-life environmental catalyst for VOCs elimination.

A novel porous and highly efficient Fe-Ce-Co nanoparticles anchored in biochar derived from coconut husk for photo-Fenton degradation of binary mixtures of dyes

In this study, Fe-Ce-Co@BC, a biochar-based nanocatalystmaterial, was synthesized and used for the photocatalytic decomposition of hazardous dyes (Rhodamine B and Methylene Blue) in open exposure to the sun. The Fe-Ce-Co@BC photocatalyst was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray analysis (EDAX) and high-resolution transmission electron microscopy (HRTEM), in order to determine its structure, composition and morphology. For an accurate evaluation of the nanocatalyst sample's optical characteristics, UV–visible (UV–vis) spectrophotometry was used. The photocatalytic ability of the as-synthesized nanocatalyst was evaluated by analyzing dye degradation under visible light irradiation. Data from SEM, TEM, XRD, HRTEM, and XPS showed that the expected nano-catalyst had formed. From the nanocatalyst band-gap position, it implies a substantial decrease in the rate of electron-hole recombination and thereby improved charge separation. Thus, it turned out that the nanocatalyst's effective photocatalytic activity had resulted from the synergistic interactions between the various moieties. Under visible light irradiation for 35 and 25 min, the photocatalyst was observed to degrade the developing organic water pollutants RhB and MB by 94.24 ± 1.21% and 96.34 ± 1.42%, respectively. Pseudo-first order kinetics were used to guide the photodegradation, with specific reaction rates of 0.1117 and 0.1364 min−1, respectively. Investigations have also been done into how other factors, including contact duration, catalyst dosage, starting concentration, and water matrices, affect degrading performance. The current study achieves its goal of creating a nano-photocatalyst with excellent photostability and reusability that is effective in the visible area of the electromagnetic spectrum and can break down emergent, non-biodegradable organic components water pollutants.

Co3O4 Catalysts for Complete Toluene Oxidation: Review including Meta-Analysis of Catalyst Activity Data

Designing highly active catalysts for the oxidation of volatile organic compounds (VOCs) involves fine-tuning the catalytic surface and improving its interaction with VOCs. The present review assesses various studies conducted in the last decade on Co3O4 catalysts for the complete oxidation of toluene (C7H8) and provides information on the synthesis and physicochemical characterization of these catalysts. Taking this one step further, data from the literature were carefully chosen for an extensive meta-analysis aiming at elucidating the structure sensitivity of toluene oxidation over Co3O4 catalysts. Specifically, the specific reaction rate was calculated and correlated with the physicochemical properties of the catalysts, namely, the specific surface area, faceting, and Co3+/Co2+ ratio. Based on this analysis, the specific surface area does not exert a significant impact on the specific activity of Co3O4 catalysts for the total oxidation of toluene. Instead, the specific reaction rates are influenced by the morphology, surface concentration, exposed crystallographic planes, and oxidation state of cobalt cations. These factors determine the catalyst’s specific activity by creating defects, oxygen vacancies, or oxygen species with different reactivities. It was also found that a high surface Co3+/Co2+ ratio is necessary for achieving high catalytic performance in the oxidation of VOCs.

Effect of manganese addition to Ni-Cu oxides on properties and activity in the oxidation of volatile organic compounds

Transition metal oxides are suitable for the total oxidation of harmful volatile organic compounds. The effect of Mn addition to Ni-Cu oxides was investigated to determine the optimum cation composition for achieving high catalytic performance in the total oxidation of ethanol and toluene, which were chosen as model volatile organic compounds. Single component (Ni, Cu, Mn), binary Ni-Cu, and ternary (Ni-Cu-Mn) oxide catalysts with various Ni:Cu and Ni:Cu:Mn molar ratios were prepared by precipitation of aqueous nitrate solutions followed by calcination at 500 °C in air. The catalysts were characterized by AAS, powder XRD, Raman spectroscopy, N2 adsorption, H2-TPR, and XPS spectroscopy. The addition of Mn to Ni-Cu oxides led to the formation of Ni-Cu-Mn mixed oxides with spinel structure and Ni-Mn mixed oxides (Ni6MnO8, NiMnO3). On the other hand, the Ni-Cu catalysts contained a mixture of NiO and CuO. In the H2-TPR experiments, the Ni-Cu-Mn oxides were reduced at lower temperatures compared to the binary Ni-Cu catalysts. The catalytic performance of Ni-Cu-Mn oxide catalysts was higher than that of the Ni-Cu catalysts. As the Mn concentration increased, the concentration of metal-bound oxygen raised, while the concentration of oxygen vacancies slightly decreased. A linear correlation was revealed between the surface concentrations of oxygen vacancies determined by XPS and specific reaction rates in ethanol and toluene oxidation over the Ni-Cu and Ni-Cu-Mn catalysts. For the Ni-Cu-Mn mixed oxides and the mixture of Ni and Cu oxides, a synergistic effect was found in the oxidation of both model compounds.

A novel hybrid continuous-flow wastewater treatment for lamotrigine degradation by combining enzymatic and photo-oxidative reactions

In response to the increasing occurrence of lamotrigine (LMG) in wastewater, low removal efficiency of conventional treatments, and the need for advanced and innovative approaches, our work aimed to develop and optimize a hybrid enzymatic-photo-oxidative treatment. The coupling of immobilized homemade peroxidase and UVC/H2O2 was first studied in batch mode. The hybrid reactions resulted in 100 % removal and a first-order specific reaction rate of 0.142 min−1 at 80 mg L−1 of H2O2. Subsequently, our research focused on treatment optimization in a flat-plate reactor operated in continuous flow. Response surface methodology revealed that maintaining a UVC dose of 3240 mJ cm−2 allows >90 % removal across a wide range of H2O2 concentrations. The experiment with LMG-spiked effluent confirmed the effectiveness of the proposed treatment for removing the antiepileptic from a real matrix. The proposed degradation pathway shows that the system can oxidize lamotrigine by sequential reactions with additional dechlorination steps not yet reported. Furthermore, only the hybrid reactions showed environmental safety, as confirmed by cytotoxicity studies. Notably, our study evaluated, for the first time, the coupling of enzymatic and photo-oxidative reactions in a single reactor operated in continuous-flow mode. The operational flexibility suggests its potential application for wastewater treatment facilities.

Assessment of Bulk Oxygen Capacity and Transient Redox Behavior of Foamed Lanthanum Strontium Manganese Perovskites

Abstract Synthesis of solar thermochemical hydrogen (STCH) production redox materials with engineered structures, for example, replica foams, can enable efficient heat and mass transport and are critical for scaled-up systems. Prior work has motivated the use of lanthanum strontium manganese (LSM)-type perovskites as foamed STCH materials, but the effect of their morphology on bulk and kinetic behavior has not been reported. In this work, replica and direct foamed samples of La0.65Sr0.35MnO3-δ (LSM35) were fabricated and compared to synthesized powders and dense monoliths, and similarly synthesized CeO2-δ (ceria) foams, regarding their specific reaction rates and bulk oxygen capacity/H2 yields. Changes in oxygen capacity (Δδ) and reaction rates were measured between 1200 °C and 1400 °C by using fixed ratios of steam and hydrogen during both reduction and oxidation steps, allowing for analysis under practical high conversion conditions. Results suggest bulk behavior and reaction rates of the foamed LSM materials are comparable to their powder analogues. Differences in reaction rates were observed only when replica foamed samples were subjected to rapid laser heating (emulating conditions expected in solar furnaces), which is expected but has not been demonstrated at such a small scale. Foamed samples were further subjected to 50 redox cycles at 1400 °C to evaluate their stability. Results show no statistically significant decrease in hydrogen production for any of the foamed samples, but the direct foamed samples became brittle with time. Together, these results demonstrate the viability of replica foamed LSM perovskites for integration in scaled-up STCH systems.

Calcium oxide nanoparticles: Biosynthesis, characterization and photocatalytic activity for application in yellow tartrazine dye removal

Dyes are substances that have a high polluting potential, due to their low biodegradability and chemical stability, causing serious environmental damage when disposed of incorrectly. Yellow tartrazine (YT) dye as an environmental liability requires attention, since it causes toxic effects in fish (Danio rerio) with a potential allergic effect in humans. In this context, the present study aims to synthesize and characterize calcium oxide nanoparticles (CaO-NPs) to evaluate the photocatalytic activity for the YT photodegradation under visible irradiation. CaO-NPs were synthesized by the biosynthesis method from golden linseed (Linum usitatissimum L.) extract. Central Composite Rotational Design (CCRD 23) was used to determine the ideal condition for the photocatalytic tests. X-ray diffraction (XRD), zeta potential (ZP), physical adsorption of N2, zero charge point (pHzcp), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy by Energy Dispersive Spectroscopy (SEM-EDS), Diffuse Reflectance Spectroscopy (DRS) and Field Emission Gun – Scanning Electron Microscope (FEG-SEM) were used to the CaO-NPs characterization. Thus, CaO-NPs presented SBET = 14±0.02 m2g−1, Dp = 20.9±0.02 nm and Vp = 0.054±0.004 cm3g−1, characteristic of a mesoporous material. ATR-FTIR spectrum showed characteristic stretches of specific functional groups (–CH, –CO, C = C, Ca-O, –OH) from plant extract and metallic precursor. CaO-NPs showed pHZCP equal to 7.74, positive surface charge (+12.7 mV) and bang gap energy of 2.61 eV. FEG-SEM micrographs showed that has a small agglomeration with defined morphology, but with irregular particle size (around 48 nm), and SEM-EDS micrographs showed an elemental composition (in weight) of the 50.24% oxygen, 3.32% magnesium, 2.29% iron, 10.44% calcium, 14.07% silicon, 3.33% aluminum and 0.63% potassium. Regarding CCRD 23, the ideal condition was the pH = 7.0, [CaO-NPs] = 1.2 g/L and [YT] = 20 mg/L, with 76.2% of photodegradation and a pseudo first-order reaction specific reaction rate k = 0.089 min−1. After V cycles of CaO-NPs recycling, there was a decrease of around 22.83%, indicating a saturation of the active sites available in the nanocatalyst Therefore, CaO-NPs showed potential application for TY photodegradation to be used in wastewater treatment being an alternative nanocatalyst, meeting nanotechnology and sustainable development.