International Journal of Chemical Kinetics最新文献

The latest developments in the adsorption of organic dyes by adsorbents (metal oxides, modified metal oxides) were addressed in this review study. The main goal of this paper is to sort out the dispersion information of adsorbent materials, which are often employed in organic dye adsorption. The review dedicated to the specific dyes adsorption using various adsorbent (metal oxides, modified metal oxides). The review covers the adsorption process including parameters, kinetics, and isotherms. The review gives the brief information of Congo red (CR) adsorption using metal oxide nano-adsorbents which provide readers with massive dye specific collection. For the first time, several metal-doped materials that absorb organic dyes are summarized and addressed. The review includes adsorption of organic dyes using single metal oxide, bimetallic oxide, trimetallic oxide, and modified metal oxide. This study also summarized the effects of critical factors such as pH, initial dye concentration, adsorbent dosage, contact time, and temperature on dye adsorption utilizing metal oxide nano-adsorbents. In addition, the kinetic and applied isotherm models have been discussed. Finally, a few recommendations are made for further research on adsorbent materials.

Non-isothermal thermogravimetric tests of Terminalia chebula (Helikha) were conducted under inert N₂ gas environment for temperatures (25–900°C) at heating rates of 10, 20, 35, and 55°C min⁻¹. Kinetic triplet approximated employing five iso-conversional methods namely, differential Friedman method (DFM), distributed activation method (DAEM), Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), and Starink (STK). Average values of activation energy (kJ mol⁻¹) and frequency factor (min⁻¹) calculated by the five models were 227.11, 2.98 × 10²¹ for DFM; 229.21, 4.63 × 10²¹ for KAS; 227.11, 3.81 × 10²⁰ for OFW; 225.54, 1.15 × 10¹⁸ for STK; and 227.33, 3.02 × 10²⁰ for DAEM respectively over the conversion range up to 0.8. In the kinetics study, correlation coefficient (R²) of greater than 0.97 is noticed in the conversion range of α = 0.1–0.8 for all models. From thermodynamic analysis, average values of ΔH (kJ mol⁻¹), ΔG (kJ mol⁻¹), and ΔS (kJ mol⁻¹ K⁻¹) for DAEM: 221.8, 179.69, and 0.065; for DFM: 236.40, 179.37, and 0.089; for KAS: 221.8, 179.69, and 0.065; for OFW: 220.22, 179.72, and 0.063; and for STK: 222.02, 179.68, and 0.066 were estimated to assess viability and reactivity of the process. Criado's master plots revealed that the data obtained from pyrolysis of selected biomass was followed a multistep reaction pathway.

The hybrid molecule phenylthiazolidine derivatives and probucol were kinetically examined as antioxidants (AOs) in scavenging tert-butylperoxyl radical (t-BuOO^•) with comparable to the reference AO, butylated hydroxytoluene (BHT). The anti-t-BuOO^• reactivity of phenylthiazolidine derivatives and probucol was established using the direct kinetic electron paramagnetic resonance (EPR) technique with pulse reactant injection. Absolute values of the bimolecular reaction rate constants and antiradical capacities of the studied compounds were measured from −63 to 0°C. The main antiperoxylradical sites of the compounds under study were revealed.

High removal ability of t-BuOO^• by (2-(4-hydroxyphenyl)thiazolidine), 4-[thiazolidin-2-yl]benzene-1,2-diol, 2-(4-hydroxyphenyl)thiazolidine-4-carboxylic acid and probucol was connected with the reaction of hydrogen atom abstraction from phenolic OH group.

Weaker antiperoxylradical reactivity of 2-phenylthiazolidine was connected with the slower reaction of hydrogen atom abstraction from benzylic C–H bond in reference to nitrogen and sulfur atoms compared with the phenolic OH group. It is found that sulfide groups had much weaker participation in antiperoxylradical reactivity of the studied compounds. It is concluded that removal of alkylperoxyl radicals by oxidizable phenylthiazolidine derivatives and probucol may partially account for biological activity of their compounds.

A large amount of furnace slag is produced from steelmaking every year. The resultant by-products will severely damage the natural environment and ecosystems if not treated properly. Businesses worldwide have thus been striving for slag recycling and solving various complex problems. In this study, basic oxygen furnace slag (BOFS) was regarded as an adsorbent to adsorb phosphate in water. In addition to a physical–chemical property analysis of the by-products, the present study explored the performance of basic oxygen furnace slag in adsorbing phosphorous (P) with different size settings, and observed the surface structure of fused basic oxygen furnace slag.The results revealed that free-state Ca accounts for the majority in basic oxygen furnace slag content, demonstrating the removal of nearly all phosphorous in water. The results of Fourier-transform infrared spectroscopy (FT-IR) on basic oxygen furnace slag with >200 mesh size revealed complex wave crests at the fingerprint region (570–980 cm⁻¹). The result signifies that the basic oxygen furnace slag samples comprise strong Si─O and O─Si─O bonds within silicate minerals. Moreover, basic oxygen furnace slag samples with a particle size >200 mesh contain very high content of lime (CaO) (reaching 49.5%). This property fully demonstrates that basic oxygen furnace slag samples in a small particle size were more active as an aggregate. This study found that the Langmuir adsorption isotherm model (R² = 0.997) is slightly better than the Freundlich adsorption isotherm model (R² = 0.984), which shows that the process in which basic oxygen furnace slag adsorbs P is monolayer adsorption, and the adsorption energy is more uniformly distributed among BOFS samples. This study also found that basic oxygen furnace slag samples melted at 1200°C can effectively encapsulate some heavy metal pollutants and form stable glassy slag. The change proved that a fused basic oxygen furnace slag sample could effectively encapsulate heavy metal pollutants and formed glassy-state slag with high stability. This mechanism would reduce the likelihood of heavy metal leaching when basic oxygen furnace slag serves as a subgrade aggregate, permeable material, or concrete aggregate in the future.

This study investigated mathematical modeling and optimization of the xylene isomerization reaction in a commercial adiabatic reactor. The proposed model, consisting of a set of algebraic and ordinary differential equations, is based on a heterogeneous one-dimensional steady-state formulation. To verify the proposed model, the simulation results have been compared to available data from an industrial reactor. A good agreement has been found between the simulation and plant data. The genetic algorithm (GA) method is applied to optimize the reactor operating conditions considering the para-xylene (p-xylene) mole fraction in reactor outlet as the main objective function. According to the simulation results, there is an optimum initial temperature for maximizing the objective function. In the optimization process, the p-xylene mole fraction was enhanced by 3.0% at an optimized feed temperature of 678.04K.

In the present work, using on-the-fly classical trajectory calculations along with quantum chemical computation, we have shown that HO$�{}_2^{•}$+O₃→ OH^•+2O₂ reaction can be a potential source of the vibrationally excited OH radical. The investigation suggests that OH radical will be majorly produced in ν=1 and ν=2 states. We have also shown that the vibrationally hot OH radical is key in interpreting the observed branching fraction of ¹⁶OH^• in the gas phase experiment of Nelson and Zahniser (J. Phys. Chem. 1994, 98, 2101–2104). Lastly, we have discussed the atmospheric implications of title reaction by comparing it with other chemical reactions known to produce hot OH radical in the atmosphere.

The combustion chambers of direct-fired supercritical CO₂ power plants operate at pressures of approximately 300 bar and CO₂ dilutions of up to 96%. The rate coefficients used in existing chemical kinetic mechanisms are validated for much lower pressures and much smaller concentrations of CO₂. Recently, the UoS sCO₂ 1.0 and UoS sCO₂ 2.0 mechanisms have been developed to better predict ignition delay time (IDT) data from shock tube studies at pressures from 1 to 260 bar in various CO₂-containing bath gas compositions. The chemistry of the methyldioxy radical (CH₃O₂) has been identified as an essential combustion intermediate for methane combustion above 100 bar, where mechanisms missing this species begin to vastly overpredict the IDT. The current literature available on CH₃O₂ is very limited and often concerned with atmospheric chemistry and low-pressure, low-temperature combustion. This means that the rate coefficients used in UoS sCO₂ 2.0 are commonly determined at sub-atmospheric pressures and temperatures below 1000 K with some rate coefficients being over 30 years old. In this work, the rate coefficients of new potential CH₃O₂ reactions are added to the current mechanism to create UoS sCO₂ 2.1 It is shown that the influence of CH₃O₂ on the IDT is greatest at high pressures and low temperatures. It has also been demonstrated that CO₂ has very little effect on the chemistry of CH₃O₂ at 300 bar meaning that CH₃O₂ rate coefficients can be determined in other bath gases, reducing the impact of non-ideal effects such as bifurcation when studying in a CO₂ bath gas. The updated UoS sCO₂ 2.1 mechanism is then compared to high-pressure IDT data and the most important reactions which require reinvestigation have been identified as the essential next steps in understanding high-pressure methane combustion.

The study of thermodynamics and kinetics of leaching rare earth elements (REEs) is a fundamental aspect in understanding the mechanism behind the leaching process. Leaching of REEs from coal ash with aqueous solution of organocarboxylic acid is a heterogeneous fluid-particle system. In the present study, the leaching mechanisms of these three potential organocarboxylic acids, tartaric acid, lactic acid, and citric acid were examined over a range of temperature (30–90°C) at various leaching durations. The kinetic data thus obtained were found to follow deviation from the conventional shrinking core model (SCM). A mixed mechanism model was deduced to be the optimum fit to the data with high precision (R² > 0.95) and desired graphical linearity with closer interception to the origin. Aluminosilicate matrix remained unaltered after acid treatment which is the unchanged core concluded as from the kinetic mechanism. Morphological analysis using Scanning Electron Microscope (SEM) and particle size determinations were suggestive of significant reduction in grain size post leaching with organocarboxylic acids, tartaric acid being the most effective of all.

Adsorption studies of decolorization of Acid blue dye by using novel adsorbents of preformed flocs of Aluminum Sulphate, Ferric Chloride, and Ferrous Sulphate were carried out through non-flow batch sorption studies. The influence of pH, equilibrium contact time, and floc dose on color removal was studied. Kinetic and equilibrium studies were carried out to know the efficacy of adsorbents in the decolorization of an aqueous solution of C.I. Acid blue 113 dye. In order to probe into the mechanism involved in the decolorization of dye solution, FTIR and SEM studies were conducted. The Langmuir isotherm was well fitted to the equilibrium data implying that there is monolayer formation in the process of sorption. Kinetic data fitted well to pseudo second order which states that chemisorption is the rate limiting step in the adsorption process. The adsorption capacity of preformed flocs of aluminum sulphate, ferric chloride, and ferrous sulphate were found to be 450 mg/g, 500 mg/g, and 125 mg/g. FTIR and SEM studies shows that there is adsorbent-dye complex formation in the adsorption process of decolorization of Acid dye with preformed flocs.