Reaction Kinetics, Mechanisms and Catalysis最新文献

In this study, Bentonite-Ag₃PO₄ (BAP) material was synthesized via the co-precipitation method, and its photocatalytic activity was evaluated for the degradation of Rhodamine B (RhB) at a concentration of 10 mg/L in a 300 mL solution under simulated UV irradiation. The synthesized material was characterized using various techniques, including X-ray diffraction, Fourier-transform infrared spectrometry, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), UV–Vis diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller (BET) surface area analysis. The photocatalytic activity of BAP at a concentration of 1 g/L exhibited excellent performance, achieving 100% degradation of RhB after 90 minu under simulated UV_{365 nm} irradiation. The charge carrier pathway was investigated using scavengers for photogenerated holes (h⁺), hydroxyl radicals (HO^⋅), and superoxide radicals (({text{O}}_{2}^{cdot -})), such as ethylenediaminetetraacetic acid (EDTA), isopropanol (IPA), and benzoquinone (BQ).

This study investigated the reinforcement of unsaturated polyester resin (UPR) with montmorillonite (MMT) nanoclay, delving into the effects of organic modification using cationic benzododecinium chloride (DDBAC) in contrast to anionic octadecanoic acid (SOD), aiming to discern their contributions. The investigation delves into the curing kinetics of UPR incorporating organically modified clay, initiated by methyl ethyl ketone peroxide (MEKP), and accelerated by cobalt octoate (CoO). Exploiting dynamic differential scanning calorimetry (DSC), the study employs advanced isoconversional methods, namely Trache-Abdelaziz-Siwani (TAS) and Vyazovkin's method coupled with the compensation effect (Vya/CE), to assess the kinetic parameters of the cure reactions. The incorporation of modified nanoclays into the UPR resulted in a significant reduction in the activation energy barrier for the redox reaction. Specifically, the activation energy decreased from 118 kJ/mol for the pristine UPR to 94 kJ/mol for the UPR/MMT-SOD system and 82 kJ/mol for the UPR/MMT-DDBAC system. Furthermore, the thermal decomposition reaction of the two modified UPR systems also exhibited a decrease in activation energy. The pristine UPR had an activation energy of 126 kJ/mol, which is reduced to 88 kJ/mol for the modified UPR systems. Consistently, a decline in the pre-exponential factor is noted, indicating a lowered frequency of collisions between reacting entities, transitioning from 1.39 × 10¹⁵ and 3.09 × 10¹⁶ s⁻¹ in the pristine unsaturated polyester resin to 4.61 × 10⁹ and 4.96 × 10¹⁰ s⁻¹ in the UPR/MMT-SOD system for the redox and thermal decomposition reactions. Thermogravimetric analysis elucidates heightened stability in the formulated UPR systems following the incorporation of modified nanoclay.

This research explores the synthesis of Cu–Ni bimetallic nanoparticles (NPs) via KC₈-driven reduction method at various refluxing time and aiming to evaluate their catalytic efficiency in the reduction of p-nitrophenol (p-NP) to p-aminophenol (p-AP). The incorporation of Ni into the Cu matrix has been critical in influencing the thermal, morphological, catalytic, and kinetic properties of the NPs. The bimetallic NPs were characterized using a suite of analytical techniques X-ray diffraction (XRD), selected area electron diffraction (SAED)-transmission electron microscopy, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller (BET). XRD revealed a crystallite size of 10.3 nm while structural and surface analyses confirmed the formation of uniformly dispersed NPs ranging 15–25 nm in size, a specific surface area of 280.82 m² g⁻¹, and a pore volume of 0.231 cc g⁻¹. Our findings revealed that Cu–Ni NPs subjected to a 30-min reflux exhibited a significantly enhanced catalytic activity with a rate constant of 0.112 ± 0.02 s⁻¹. Further optimization of the refluxing time highlights a critical window for maximizing catalytic efficiency. Intercalated KC₈-reduced Cu–Ni NPs have shown promising electrochemical performance, especially as anode materials for lithium-ion batteries. However, this research emphasizes the critical role of optimizing refluxing time to maximize catalytic efficiency, providing important insights into the design of advanced catalysts for environmental remediation and chemical synthesis applications.

Graphical abstract

Spray pyrolysis successfully synthesizes doped and co-doped thin films using the formula Al_xZn_0.06Co₃O₄ (x = 0.0, 0.01, 0.02, 0.03, 0.04, and 0.05). So, the prepared samples were examined for structural, surface morphology, optical, and photocatalytic properties using X-ray diffraction (XRD), scanning electron microscope (SEM) analyses, and ultraviolet–vsible spectrophotometer (UV–Vis). X-ray diffraction (XRD) analysis of all the samples verifies the presence of a single-phase spinel cubic structure, devoid of further heterogeneity or structural transition. The direct band gap E_g2 has decreased to 2.04 eV. Methylene blue (MB) degradation in sunshine shows that Al_xZn_0.06Co₃O₄ has substantially better photocatalytic activity than Zn_0.06Co₃O₄, with a maximum removal efficiency of 95.1% in 4 h. This contribution also presents a postulated mechanism for the photocatalytic activity of Zn_0.06Co₃O₄ thin films. Therefore, it is verified that the doped and co-doped Al_xZn_0.06Co₃O₄ thin films may be a cost-effective and environmentally safe catalyst for photocatalytic water purification. Consequently, it is verified that the doped and co-doped Al_xZn_0.06Co₃O₄ thin films may be a cost-effective and ecologically safe catalyst for photocatalytic water purification.

Waste fig fruit, an eco-friendly, available, and not toxic, has been used as active carbon for the first time in the elimination of methylene blue dye from its aqueous solution, which was never reported previously. The fig fruit activated carbon (FFAC) has been obtained and then characterized using several techniques, such as field-emission scanning electron microscopes (FE-SEM), X-ray diffraction, Brunauer–Emmett–Teller, and Fourier transform infrared spectroscopy (FTIR). As a part of the practical experiments, temperatures, initial concentrations, FFAC amount, contact time, pH solution, activation agent, and volume solution were studied as factors that can change adsorption parameters. Nevertheless, the pH of the solution was checked at the following values: pH3, pH7, pH9, and pH10, the initial concentration of methylene blue dye was studied at various concentrations: 40, 60, 80, 100, and 120 mg/L. Furthermore, the adsorption temperatures of the solution were checked at the following degrees: 15, 30, 40, and 50 °C. The adsorption capacity value for fig fruit active carbon was 115 mg/g for 0.06 g and 55 mg/g for 0.02 g. Moreover, the correlation coefficient of the Langmuir isotherm model was 0.9911, so the process of adsorption prefers it. It was observed that pseudo-first order kinetics is the preferred to achieve the process with a rate constant of 0.0332 min^˗1. Thermodynamically, the process of adsorption was completely spontaneous, and the Gibbs free energy ranged between − 7.88 and − 15.16 kJ/mol. A monolayer has formed in the adsorption process. Additionally, the maximum capacity of adsorption (Q_m) was 63.38 mg/g. The fig fruit active carbon, an environmentally friendly adsorbent for methylene blue dye, acquired good performance in the adsorption process.

The performance of Al/Fe-pillared clay as a heterogeneous Fenton-type catalyst for the oxidative degradation of paracetamol was firstly studied in this research. The Al/Fe-pillared clay was synthesized by using bentonite and intercalating solution prepared by alkaline hydrolysis of a mixture of AlCl₃ and FeCl₃ (Al/Fe 10/1 mol/mol, OH/(Fe+Al) 2.0). The solid was then heated at 500 °C for 2 h and characterized by FTIR, XRD, SEM and low temperature nitrogen adsorption analysis. The clay pillarization resulted in the formation of micropores and a threefold increase in the specific surface area.The degradation rate was studied by the decrease in paracetamol concentration measured by HPLC. Al/Fe-pillared clay showed high activity in the Fenton degradation of paracetamol: the catalytic reaction rate increased 25 times compared to the non-catalytic reaction, which was caused by the formation of ∙OH and ∙HO₂ radicals, as shown by tests using radical scavengers. It was found that the rate and efficiency of paracetamol degradation depended on pH, the ratio of paracetamol and hydrogen peroxide concentrations, the catalyst content and temperature. The optimal conditions were determined, allowing to achieve high efficiency of paracetamol degradation and high catalyst stability (Fe leaching was less 1 ppm). 100% paracetamol removal was achieved in 90 min at pH 4.0, a stoichiometric amount of H₂O₂ ([H₂O₂]/[PCT] 21 mol/mol), 1 g/L catalyst, 50 °C. Al/Fe-pillared was used in three consecutive cycles without regeneration and loss of activity. The results showed that Al/Fe-pillared clay could be a promising heterogeneous Fenton catalyst for the removal of pharmaceutical pollutants from wastewater.

Catalysts based on mesoporous silica gel doped with cerium, terbium and modified with silver (Ce–Ag/MPS, Tb–Ag/MPS) were obtained by the template method. The physicochemical characteristics of the obtained catalyst were studied by low-temperature nitrogen adsorption–desorption, scanning electron microscopy, X-ray diffraction analysis, inductively coupled plasma mass spectrometry, and IR spectrometry. The possibility of using the obtained samples as effective and selective catalysts for the hydrogenation of 1-hexyne/1-hexene and 1-heptyne/1-heptene hydrocarbon mixtures (with 30% alkyne content) in the temperature range of 130–160 °C and a hydrogen pressure of 3 atm was studied. It was found that the Tb–Ag/MPS catalyst is more effective, maintaining alkene selectivity with increasing hydrogenation temperature.

Coating and extrusion methods were compared in lab-scale catalytic decomposition of chlorobenzene (CB) to increase utilization of the powdered VW/TiO₂ catalyst. As a result, when the VW/TiO₂ was coated on a cordierite by silicone gel, the obtained monolithic catalyst removed 1449 ppm g⁻¹ (per gram of actual coated VW/TiO₂) of CB at 300 °C. Since the monolithic catalyst obtained a smaller conversion (68%) than the powdered VW/TiO₂ (87%), a mechanism investigation revealed the reasons. On one hand, the binder silicon covered oxygen vacancies and decreased the reductive capacity of the VW/TiO₂. On the other hand, the coating process, such as dispersion in gel and afterward calcination, also decreased the redox property. However, these disadvantages were inevitable, and the put-forward coating method still showed a better catalytic performance than a commercial honeycomb catalyst, which only removed 237 ppm g⁻¹ of CB at 300 °C. This work supplies various potential coating methods for researchers, who would like to increase the applicability of their newly developed catalysts.

This study focuses on enhancing thermal, energetic and combustion properties of boron based solid fuel-rich propellant (SFRP) by doping boron with sodium azide. The challenges associated with boron's combustion efficiency, such as high ignition temperature and oxide film formation, are addressed. The research explores the potential of using sodium azide as a coating agent for boron in SFRP formulation. The prepared propellants based on boron and boron modified with sodium azide undergo thorough characterization for physico-chemical, thermal, energetic and combustion properties, including FTIR, RAMAN, X-ray diffraction (XRD), differential scanning calorimetry (DSC), bomb calorimetry and combustion test. Additionally, based on the results obtained by DSC tests, a comprehensive kinetic analysis was performed using iso-conversional methods, notably It-KAS and It-FWO. The obtained results confirm the positive effect of sodium azide on thermal, energetic and combustion properties of boron based SFRP.

Herein, for the very first time, barium-doped ZnO nanorods (Ba-ZnO NRs) with varying Ba concentration were fabricated using black pepper (Piper nigrum) leaf extract. X-ray diffraction (XRD) analysis revealed that the studied powder exhibits wurtzite crystal structure, and scanning electron microscope (SEM) image displays the rod-like morphology, the Ba doping changes surface roughness. As dopant content (Ba) is increased, the energy band gap decreases, which can be attributed to variations in crystallite size and substitutions of the dopant ions. In photocatalytic activity, Ba-ZnO NRs degraded antibiotic ciprofloxacin (CIP) and rhodamine B (RhB) dye more efficiently than pure ZnO NRs. Notably, CIP antibiotic and RhB dye showed 95.44 and 98.94% decomposition efficiency in 80 and 35 min under visible light, respectively, with an estimated rate constant of 0.0383 and 0.1188 min⁻¹. Based on the results of this study, Ba-ZnO NRs show promising potential for advanced wastewater treatment.