Reaction Kinetics, Mechanisms and Catalysis最新文献

In response to the pressing challenges in various fields, particularly healthcare and infection prevention, this research explores the synthesis, characterization, and assessment of ZnO–Ag nanocomposites for antibacterial properties. Employing a solvothermal method, silver nanoparticles were incorporated into hydrothermally synthesized zinc oxide nanorods, aiming to harness their synergistic antibacterial effects. The research systematically analyses the nanocomposites, unveiling their structural and compositional features. Antibacterial potential is evaluated through agar well diffusion assay, demonstrating increased efficacy against diverse bacteria. With implications extending to biomedical applications, these nanocomposites emerge as promising contenders for infection prevention in healthcare settings.

The impact of different concentrations of natural antioxidants (curcumin) on the thermal stability of UHMWPE (ultra-high molecular weight polyethylene) is examined via the thermogravimetric (TGA/DTA) technique, in the temperature region 50–600 °C at a 5 °C/min heating rate. This work employs the model fitting (Coats and Redfern) approach to determine the optimal curcumin concentration. UHMWPE samples at optimum concentration are further subjected to three other heating rates, viz., 10, 15 and 20 °C. A bi-Gaussian asymmetric function is utilized for deconvolution to elucidate the complexities of thermal decomposition. Through deconvolution, two peaks are obtained and the activation energy corresponding to each peak is determined through two iso-conversional kinetic (Friedman and Starink) models. By utilizing activation energy, the random nucleation reaction mechanism involved in thermal decomposition is recognized. Finally, changes in entropy (left(Delta Sright)), enthalpy (left(Delta Hright)) and Gibbs free energy (left(Delta Gright)) are determined.

This study investigates the effect of coating AP with RGO on its thermal decomposition kinetics and behavior. Differential scanning calorimetry (DSC) was performed for pure AP and AP@RGO at several heating rates. DSC curves of AP@RGO for various heating rates were split into individual reactions using a mathematical deconvolution approach. The assessment of kinetic triplets of various reactions was accomplished for both AP and AP@RGO using an effective model-free approach (MFA). Deconvolution of the DSC curve for AP@RGO reveals three distinct decomposition processes, compared to only two observed in pure AP. Notably, the low-temperature decomposition reaction appears to be catalyzed by RGO, leading to a dramatic decrease in activation energy from 164 to 116 kJ/g. Conversely, the high-temperature decomposition remains uncatalyzed, with a slight increase in activation energy from 177 to 188 kJ/g. The catalytic effectiveness of RGO in the thermal decomposition process of AP fluctuates due to structural transformations within RGO and its degradation in the presence of perchloric acid.

This study investigates the potential of pomegranate peel (PP) as a raw material for synthesizing a novel biocatalyst metal oxide (BCMO) aimed at the efficient removal of methyl orange (MO) dye from aqueous solutions. The adsorption capacities of both PP and BCMO were systematically evaluated. PP was subjected to inorganic salt treatment and calcination to enhance its adsorption capacity and increase attractive forces at the nanoparticle level. The surface characteristics of the biocatalyst were thoroughly examined using FTIR, SEM, BET analysis, and EDX spectroscopy, revealing the development of a crystalline structure following treatment with Mg(NO₃)₂⋅6H₂O, along with observable changes in surface morphology and elemental composition. Under standard conditions, BCMO demonstrated a significant increase in efficiency, achieving 99.80% removal for 100 mg/L of methyl orange, compared to 44% for untreated PP at 50 mg/L. Kinetic analysis indicated a transition from pseudo-first-order to pseudo-second-order, signifying a shift from physical to chemical adsorption. This transition resulted in a substantial reduction in equilibrium time and a significant increase in maximum adsorption capacity from 17.3637 to 176.686 mg/g. Furthermore, the catalytic efficiency of BCMO was assessed over seven cycles, showing only a minor 5% reduction in efficiency, indicating its potential for practical applications. The environmental sustainability of the road was assessed using the AGREE and BAGI indicators, both of which are considered exemplary measures of environmental friendliness.

Graphical Abstract

To modify the wide bandgap and intrinsic high recombination rate of photogenerated charge carriers of Zn₂SnO₄ photocatalysts, Ag/SnO₂–Zn₂SnO₄ composites were prepared by depositing Ag nanoparticles onto cube-shaped SnO₂–Zn₂SnO₄ nanomaterials via photoreduction. The composites were characterized by XRD, SEM, EDS, TEM, XPS, and UV–Vis DRS, and their photocatalytic degradation effect on rhodamine B (Rh B) for different Ag loadings was studied, with 10%Ag/SnO₂–Zn₂SnO₄ showing the greatest effect. The UV photocatalytic degradation rate of the Rh B solution reaches 100% after 12 min of visible light irradiation and 91% after five cycles. The free radical trapping agent experiment indicated that the active substances of Ag/SnO₂–Zn₂SnO₄ photocatalysis are ·O₂⁻ and h⁺. Further, photoelectrochemical tests revealed the higher electron–hole separation efficiency and faster charge transfer rate of the composites, enhancing the formation of photoproduced carriers and photocatalytic activity.

A solvent-free, acid-free, and efficient strategy was developed for the selective preparation of 4-nitro-o-xylene (4-NOX) from the catalytic nitration of o-xylene with NO₂ mediated O₂ over BiCl₃ immobilized silicic acid catalyst (BiCl₃-SA). The results indicated that the Lewis acid BiCl₃-SA conjoined NO₂–O₂ as a composite system synergistically promotes o-xylene conversion and 4-NOX selectivity. Under optimal conditions, 52.4% of o-xylene conversion with 68.4% 4-NOX selectivity was obtained at 35 °C. The characterization demonstrated that the highly dispersed metal Bi species form stable chemical bonds with the SA surface, which can effectively inhibit the loss of metal species and generate abundant acid sites. The developed catalyst is not only inexpensive but also has excellent stability and catalytic performance. Furthermore, a plausible mechanism for the catalytic nitration of o-xylene using NO₂ as a nitration agent over BiCl₃-SA was proposed. This work provides an eco-friendly and practical protocol for improving desirable 4-NOX selectivity and reducing the discharge of acidic wastewater, with potential application prospects.

Graphical abstract

Dissolution of a Nigerian antigorite-rich dolomite ore in methanesulfonic acid (MSA) solution for its optimal industrial application was investigated. The impact of the acid concentration, reaction temperature, particle diameter as well as reaction time on the rate of the ore dissolution was examined. The magnesium recovery was 97.2% at the optimal conditions: 2.5 mol/L MSA, solid/liquid 10 g/L, 56 µm in 2 h, and reaction temperature of 75 ºC. According to the shrinking core model, test results indicated that mass diffusion was the controlling step of the overall reaction kinetics. The activation energy of 11.26 kJ mol⁻¹ gives support to this assertion. The correlation coefficient value of (⁓0.98) indicates that the workability of the proposed kinetic model is highly effective or functional. At optimal conditions, a high-purity MgO product was obtained.

In this study, we explore the advanced optical and dielectric properties of cerium dioxide nanoparticles combined with silicon nanowire (CeO₂NP/SiNW) composites. Utilizing diffuse reflectance spectra (R(λ)), we extracted key parameters such as the extinction coefficient (k), refractive index (n), electrical conductivity (σ_elc), optical conductivity (σ_opt), and dissipation factor (tan δ) within the spectral range of 330–2000 nm. Capacitance measurements revealed a p-type conduction mechanism with a flat band potential (E_fb) of − 0.02 V. X-ray diffraction (XRD) analysis confirmed the cubic phase of the CeO₂NPs, while photoluminescence (PL) studies exhibited a broad emission peak at approximately 680 nm. The morphology of the CeO₂NP/SiNW composites was meticulously analyzed using scanning electron microscopy (SEM), focusing on variations due to different SiNW etching times. Critically, the impact of SiNW length on the photodegradation efficiency of Rhodamine B was evaluated, demonstrating a remarkable 100% degradation rate for nanowires with a length of 31.52 µm. This work underscores the importance of comprehensively studying the optical, dielectric, and photoelectrochemical properties to optimize the degradation of Rhodamine B.

Density function theory (DFT) calculations are employed to investigate double transition metal atoms anchored on the defective boron nitride for N₂ reduction in this work. By comparing the stability, N₂ adsorption energy, selectivity and activity of NRR, Mn₂@d-BN with N defect, and TM₂@d-BN (TM = Fe, V, Co and Mn) with B defect are selected as candidates. Moreover, the result shows that Mn dimer anchored on BN with B defect exhibit excellent catalytic performance for nitrogen reduction via alternating mechanism, with the potential of − 0.44 V. With regard to this work, we provide a screening scheme to explore highly efficient double-atom metals catalysts for the electrocatalytic nitrogen reduction reaction.

In the present investigation, biomass-based carbon microsheets were synthesized using melamine and corn cob powder as carbon precursors. Three adsorbents were prepared: Carbon microsheets 500 (CMS-500), biomass-based carbon microsheets (BCMS-500), and BCMS-F-500, which were characterized using different analytical techniques. Synthesized adsorbents were optimized for simultaneous adsorption of Ni(II) and Cr(VI) from an aqueous solution. Adsorption was optimized by varying the values of operating parameters, including reaction pH, adsorbent and adsorbate concentration, temperature, and contact time. Maximum adsorption of Cr(VI) was achieved at pH 2 and of Ni(II) was achieved at pH 6 using a 0.5 g/L adsorbent dose and 20 mg/L for each metal concentration. The adsorption of metal ions increased with increasing temperature. The Langmuir adsorption isotherm model best fitted the adsorption of Cr(VI) with both adsorbent and Ni(II) by CMS-500. While the Freundlich adsorption isotherm models were best suited for the adsorption of Ni(II) by BCMS-500, To understand the adsorbent properties, the adsorbent was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS), and an X-ray diffractometer (XRD). CMS-500 and BCMS-500 were found to be highly effective adsorbents that can be applied for the effective management of Cr(VI) and Ni(II)-contaminated wastewater.