Kinetic Model Research Articles

Anchored Chitosan-Functionalized Magnetite Nanoparticles for Crystal Violet Decolorization from Aqueous Samples.

In this research, 3-(triethoxysilyl)propyl isocyanate (TESPIC) functionalized chitosan was successfully synthesized to fabricate silica-coated magnetite nanoparticles (Fe3O4@SiO2-CS MNPs). The synthesized MNPs were characterized using XRD, FT-IR, SEM, and TEM instruments and were utilized for the decolorization of Crystal Violet cationic dye (CV). The affecting variables controlling CV removal efficiency were investigated using the Taguchi fractional factorial design method (L16 array). Under the optimized removal conditions (adsorbent amount = 0.12 g (4.8 g L-1), pH = 4, ionic strength = 0.05 mol L-1 NaCl, and 30 min stirring), 98.2% of the CV dye was eliminated. The kinetic and equilibrium adsorption isotherms were explained by the pseudo-second-order kinetic (R2 = 0.999) and Freundlich isotherm models, respectively. MATLAB's fmincon function as an efficient solution was applied in order to compare the Redlich-Peterson three-parametric isotherm model with two-parametric models. Moreover, the Fe3O4@SiO2-CS-TESPIC MNPs showed recyclability and reusability for subsequent runs. The findings confirmed that these functional MNPs can be considered as proper adsorbents for the removal of CV dye from the aqueous solutions.

A Consistent Kinetic Fokker–Planck Model for Gas Mixtures

We propose a general multi-species Fokker–Planck model. We prove consistency of our model: conservation properties, positivity of all temperatures, H-Theorem and the shape of equilibrium as Maxwell distributions with the same mean velocity and temperature. Moreover, we derive the usual macroscopic equations from the kinetic two-species BGK model and compute explicitly the exchange terms of momentum and energy.

Evaluation of Biochemical Methane Potential and Kinetics of Organic Waste Streams for Enhanced Biogas Production

Organic waste has the potential to produce methane gas as a substitute for petrol-based fuels, while reducing landfilling and possible environmental pollution. Generally, anaerobic digestion (AD) is used only in wastewater treatment plants as a tertiary stage of sewage sludge treatment, generating a fraction of the energy that such process plants require. In this study, four different wastes—food waste (FW), dairy industry waste (DIW), brewery waste (BW), and cardboard waste (CBW)—were tested for biogas production. The biochemical methane potential (BMP) of each sample was evaluated using an automatic methane potential system (AMPTS). Operating parameters such as pH, temperature, total solids, and volatile solids were measured. Experiments on the anaerobic digestion of the samples were monitored under mesophilic conditions (temperature 37 °C, retention time 30 days). Specific methane yields (SMYs), as well as the theoretical methane potential (BMPth), were used to calculate the biodegradability of the substrates, obtaining the highest biodegradability for BW at 95.1% and producing 462.3 ± 1.25 NmL CH4/g volatile solids (VS), followed by FW at an inoculum-to-substrate ratio (ISR) of 2 at 84% generating 391.3 NmLCH4/g VS. The BMP test of the dairy industry waste at an inoculum-to-substrate ratio of 1 was heavily inhibited by bacteria overloading of the easily degradable organic matter, obtaining a total methane production of 106.3 NmL CH4/g VS and a biodegradability index of 24.8%. The kinetic modeling study demonstrated that the best-fitting model was the modified Gompertz model, presenting the highest coefficient of determination (R2) values, the lowest root means square error (RMSE) values for five of the substrates, and the best specific biogas yield estimation with a percentage difference ranging from 0.3 to 3.6%.

Oxidative degradation of chitosan by Fe-MCM-41 heterogeneous Fenton-like system

We herein disclosed an efficient multiphase Fenton-like catalytic system for oxidative degradation of chitosan. By utilizing Fe-MCM-41, featured with regular mesoporous structure and high specific surface area, the activation efficiency of H2O2 was significantly enhanced and the chitosan degradation efficiency proved by 28.1% higher than the conventional system using H2O2 alone. Under optimized conditions (5 g/L chitosan, 0.5 g/L Fe-MCM-41, 0.16 mol/L CH3COOH, 0.86 mol/L H2O2, 50 °C, 140 min), the viscosity reduction rate of chitosan reached an impressive 98.2%. Among the catalysts tested, Fe-MCM-41 with a loading factor of x = 0.12 demonstrated optimal degradation performance. After four recycles, the degradation efficiency maintained > 93.6%, demonstrating its excellent stability and recyclability for potential industrial applications. Kinetic studies provided further elucidation of the reaction mechanism, which indicated that the degradation process of chitosan followed a first-order kinetic model, with an apparent activation energy (Ea) of 48.91 kJ/mol. This novel and efficient strategy for chitosan degradation, addressed the challenges of catalyst recovery and secondary pollution typically associated with traditional Fenton systems, and posed broad application potential for polysaccharide material processing.

Synthesis of Silica-Based Imprinted Ionic from Rice Husk Ash for Adsorption of Ni(II)

Imprinted ionic synthesis through the sol-gel process for Ni (II) adsorption has been carried out. Sodium silicate from rice husk ash (NaSiO3(RHA)), N1-(3 Trimethoxysilylpropyl) diethylenetriamine (TMPDT) and Ni (II) are stirred, then 6 M HCl is added until a gel forms. Furthermore, 0.1 M EDTA and 0.1 M HNO3 were added to the dry gel to release Ni (II) to form-imprinted ionic material (SiO2-TMPDT-Ni-Imp). The material was characterized using FTIR, SAA, and SEM-EDX. FTIR characterization of SiO2-TMPDT-Ni-Imp indicated the appearance of-OH, -CH, -Si-O-and-NH absorption. The SAA characterization results show a surface area of 18.091 m2/g, a total pore volume of 0.033 cc/g, and an average pore radius of 16.739 Å. The optimum conditions for Ni (II) adsorption by SiO2-TMPDT-Ni-Imp are pH four and a contact time of 100 minutes. The appropriate adsorption kinetic model for the absorption of Ni (II is pseudo-second order with an adsorption capacity of 6.9 mg/g. Keywords: Silica, imprinted ionic, rice husk ash, adsorption, Ni (II)

Validated kinetic modelling of ladle furnace process for predicting inclusions in API steel grade

A kinetic model of ladle furnace (LF) process is developed in C++ format using the FactSage database and ChemApp subroutines. The model considers all the process parameters such as ferroalloy and slag dissolution, wire additions, electrical arcing, steel/slag reactions, reoxidation due to slag eye opening, heat exchange between metal/slag, and refractory dissolution. Further, a correlation for inclusion removal rate was developed as a function of argon flow rate, using discrete phase method (DPM) in Computational Fluid dynamics (CFD). Lollypop samples from steel bath and slag samples were collected from the plant for API steel grade for chemical analysis and inclusion characterisation. At LF_in, the inclusions found were mostly alumina spinel with very low amount of Mg (∼3%), followed by spinel at intermediate stage having ∼15 wt. % of Mg and after Ca treatment, inclusions transformed into CaS and Calcium Aluminate type of inclusions. Overall inclusion weight fraction varied from 136 ppm at LF_in to 93 ppm at LF_out. The model calculations were found to give very good prediction for steel and slag chemistry, and inclusion global composition as compared to the plant results. Predicted temperature was found with an accuracy of ± 5 oC, while the calculated inclusion weight fraction was having an accuracy of ±12 ppm.

A modeling analysis on industrial radial-flow packed-bed reactors for the catalytic dehydrogenation of long-chain normal paraffins: Appraisal of the modeling approach

Catalytic dehydrogenation of long-chain normal paraffins is the most attractive route for producing of linear alkyl benzene. To make this happen, the radial-flow packed-bed reactors are employed as one of the most efficient currently available technologies. Simplifying assumptions that are sometimes imposed on reactor models to reduce the computational cost may also significantly decrease the accuracy of simulations. Here, it is decided to shed light on this matter by assessing the effect of typical model-simplifying assumptions on simulation results. To this end, one- and two-dimensional semi-homogeneous models are used to simulate an industrial-scale radial-flow packed-bed dehydrogenation reactor under isothermal and adiabatic conditions. Simulations are designed in four 1D isothermal, 1D adiabatic, 2D isothermal, and 2D adiabatic modes to compare different modeling strategies and investigate the effect of flow distribution on the reactor performance. An appropriate LHHW kinetics model is considered for paraffin dehydrogenation and the main associated side reactions over a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst. The model equations are solved numerically using the finite element method by COMSOL Multiphysics CFD software. The results show a 1–3 % discrepancy between the predictions of one- and two-dimensional models for feed conversion under isothermal and adiabatic conditions. In contrast, the comparison of isothermal and adiabatic results for each one- and two-dimensional models indicate a discrepancy of 33–36 %. Furthermore, the two-dimensional model shows a low non-uniformity in flow distribution under reaction conditions (∼ 0.175), which has a trivial negative effect on paraffin conversion.

Development and characterisation of orally disintegrating flurbiprofen tablets using SeDeM-ODT tool.

In this study, SeDeM-ODT parametric tests were performed to determine the use of ludipress as a directly compressible tableting excipient for the development of a flurbiprofen orally disintegrating tablet. The preformulation features of different formulations (F1 -F9) were analyzed by the SeDeM-ODT tool which showed that all the powder blends were appropriate for direct compression since all the blends had index of good compressibility and bucodispersibility (IGCB) values above 5, signifying direct compression is the most appropriate method. The powder blend of the optimized formulation was assessed by the DSC-TGA technique. The optimization of nine different formulations blends of orally disintegrating tablets (ODTs) was prepared in various ratios by the implementation of design of experiments (DoE), using the central composite design by selecting ludipress (X1) (49-55%) and croscarmellose sodium (X2) (1-5%) while hardness, friability, and disintegration tests were selected as responses. The optimized formulations were evaluated by various tests and the results indicated that all the formulations were found to be in adequate range. Formulations were subjected to stability studies at accelerated states following ICH guidelines. Shelf life was found to be 51.144-56.186 months. Results of multiple-point dissolution studies revealed that formulations followed the Higuchi kinetic model. This study revealed that the SeDeM-ODT tool has been successfully used to determine the compression behavior of active compounds and their powder blends for the direct compression (DC) method in formulating flurbiprofen-ODT tablets.

Dehydrogenation of n-butane to butadiene-1,3: 3. Kinetics of regeneration of coked aluminochromium catalyst

The kinetics of coke burning off at temperatures of 525–650 °C on a K-CrOx/γ-Al2O3 catalyst for single-stage dehydrogenation of n-butane to butadiene-1,3, similar to the industrial one, was studied. It was shown that under the studied conditions, the coke burning off reaction is described by a first-order kinetic equation with respect to oxygen and coke with an observed activation energy of ~93 kJ/mol. The adequacy of the kinetic model was confirmed by the coincidence of the calculated and experimental results.

Preparation and NH3 adsorption behavior of porous magnesium oxychloride cement-based SrCl2

In addressing challenges in Selective Catalytic Reduction (SCR) systems in vehicles, the development of novel SrCl2 composite materials with high ammonia adsorption and structural stability is crucial. In this context, we employed the porous magnesium oxychloride cement (PMOC) as a carrier material, successfully fabricating a mesoporous PMOC-SrCl2 material via solution impregnation technology. Simultaneously, we employed various characterization techniques such as XRD, full-pore analysis, TG, SEM, TEM, and EDS to examine the material. We conducted static adsorption assessments on numerous candidate materials at 0.1Mpa and 293.15 K. The synthesized C3 series material (Mass ratio of SrCl2 to PMOC = 10:3), solution impregnated for 1 h, exhibited exceptional ammonia adsorption capacity (up to 38.01 mmol·g−1). Through model fitting of experimental data, we discovered that the adsorption process of this material closely aligns with the pseudo-second-order kinetic model and the Langmuir model. Over an adsorption time span of 180 min, the adsorption rate of the composite material increased by 129 % compared to pure SrCl2. In the cycle performance testing phase, we observed that the material exhibited no significant degradation in performance after undergoing 10 cycles of adsorption/desorption. This structurally stable, cost-effective, and readily accessible high-efficiency ammonia adsorption material undoubtedly possesses immense potential to solve the application challenges of ammonia adsorption materials within automotive selective catalytic reduction systems.

Investigation of the iridium adsorption process with functionalized magnetic nanoparticles using triisobutylphosphine sulfide extractors

In this research work, the adsorption process of iridium using magnetic nanoparticles functionalized with Cyanex 471X has been investigated. In this regard, parameters affecting the adsorption process such as pH, initial concentration of iridium ions, contact time and adsorbent dosage were assessed. According to the results, pH 6, adsorbent dosage 1.2 g/L, initial concentration of iridium of 10 mg/L, and contact time of 10 min were selected as optimal conditions for iridium adsorption by this synthesized magnetic nanosorbent. The kinetics of the adsorption process was studied, and it was found that the adsorption reaction follows the pseudo-second-order kinetic model with the correlation coefficient of 0.9960. Also, experimental studies indicated that the Langmuir adsorption isotherm model best matches the experimental data (R2 = 0.9961). The maximum adsorption capacity of the nanosorbent for iridium adsorption was estimated to be 35.34 mg/g by the Langmuir isotherm. With the thermodynamic analysis of the adsorption process, it was found that this process is endothermic and spontaneous. In addition, in the investigation of iridium adsorption and desorption, HCl/HNO3 solution with a concentration of 1.5 M was selected as suitable eluent.

Eco-Friendly Green Approach to the Biosorption of Hazardous Dyes from Aqueous Solution on Ragweed (Ambrosia artemisiifolia) Biomass

The presented research includes the preparation, characterization, and implementation of magnetic biosorbent (Fe3O4/RWB), obtained from ragweed (Ambrosia artemisiifolia) biomass. Fe3O4/RWB was examined for the removal of a hazardous dye, malachite green (MG), from an aqueous solution in a batch system. The effects of the experimental parameters—initial dye concentration (10–300 mg/L), contact time (0–120 min), biosorbent dose (1–5 g/L), initial pH (2–10), ionic strength (0–1 mol/L), and temperature (298–318 K) on dye biosorption—were studied. The results showed that increases in biosorbent dose, contact time, and initial pH led to an increase in biosorption efficiency, while the increase in initial dye concentration, the ionic strength, and temperature had the opposite effect. The biosorption kinetics for MG on Fe3O4/RWB were analyzed with pseudo-first-order, pseudo-second-order, and Elovich kinetic models, while the Langmuir, Freundlich and Temkin isotherm models were used for equilibrium data analysis. It was observed that the MG biosorption followed the pseudo-second-order kinetic model, whereas the Langmuir model was the best fit for the equilibrium biosorption data of MG, with a Qmax of 34.1 mg/g. the desorption of MG from Fe3O4/RWB indicated reusability in five adsorption/desorption cycles, good performance, and potential in practical applications.

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Modeling of fluence-dependent hole-burned spectra and hole-growth kinetics using multiple two-level system model.

Numerical formalism is presented that perfectly describes resonant low-temperature hole-burned spectra (including zero-phonon holes, ZPHs) and spectral hole-growth dynamics of Al-phthalocyanine tetrasulphonate embedded in hyperquenched glassy water films over more than seven orders of fluence magnitude (0.4 µJ/cm2-5.9 J/cm2). Frequency changes during spectral hole-burning (HB) are traditionally explained with the help of a single extrinsic two-level-system (TLSext) associated with impurity molecules. The new multiple two-level system (n-TLSext) models and data analysis presented in this work show that each chromophore in an amorphous medium can couple with multiple independent TLSext, which maintain perfect photo-memory, allowing a full return of the photoproduct to the initial ("preburn") state. Modeling reveals that the experimentally observed narrow photoproduct peak at higher energies, in close vicinity of the zero-phonon hole (ZPH), reflects a dynamical feature of the HB process populating so-called "terminal" states (states that do not interact with laser excitation). Within the n-TLSext model, each chromophore possesses multiple possibilities to create a photoproduct when in interaction with the burning laser, i.e., chromophores can interact with burning laser-light multiple times until reaching the terminal states. Due to phonon-assisted absorption, terminal states are typically at higher energies than the ZPH, in agreement with the hole burned spectra reported for many molecules embedded in various amorphous solids. However, many HB systems reveal both blue- (high-energy) and red-shifted (low-energy) antiholes (i.e., photoproducts). We suggest that future modeling of resonant holes in various proteins using our n-TLSext model will provide more insight on the complexity of the protein energy landscape.

Nonlinear dispersion analysis using dynamic traveling wave model in chemical kinetics

Nonlinear dispersion analysis using dynamic traveling wave model in chemical kinetics

Rationalised experiment design for parameter estimation with sensitivity clustering

Quantitative experiments are essential for investigating, uncovering, and confirming our understanding of complex systems, necessitating the use of effective and robust experimental designs. Despite generally outperforming other approaches, the broader adoption of model-based design of experiments (MBDoE) has been hindered by oversimplified assumptions and computational overhead. To address this, we present PARameter SEnsitivity Clustering (PARSEC), an MBDoE framework that identifies informative measurable combinations through parameter sensitivity (PS) clustering. We combined PARSEC with a new variant of Approximate Bayesian Computation-based parameter estimation for rapid, automated assessment and ranking of experiment designs. Using two kinetic model systems with distinct dynamical features, we show that PARSEC-based experiments improve the parameter estimation of a complex system. By its inherent formulation, PARSEC can account for experimental restrictions and parameter variability. Moreover, we demonstrate that there is a strong correlation between sample size and the optimal number of PS clusters in PARSEC, offering a novel method to determine the ideal sampling for experiments. This validates our argument for employing parameter sensitivity in experiment design and illustrates the potential to leverage both model architecture and system dynamics to effectively explore the experimental design space.

Residue dissipation and dietary risk of cyprodinil and fludioxonil residues in green onions: ensuring safe consumption in Egypt

ABSTRACT As a vegetable commodity, onions are of considerable economic significance. They are a significant source of foreign exchange revenues in the fruit and vegetables sector, in addition to being essential for domestic consumption. However, green onions are frequently treated with multiple fungicides. As a result, there is currently a significant focus on the potential health hazards of consuming green onions, due to dietary risks and the presence of various fungicide residues. The pre-mixture fungicide cyprodinil and fludioxonil are widely used to control fungal disease in green onions. To assure consumer safety, residues in the final product must be investigated. Following Good Agricultural Practices (GAPs), field studies were carried out to investigate cyprodinil and fludioxonil dissipation and terminal residues on green onions. The concentrations of cyprodinil and fludioxonil in green onions decreased with time by a first-order kinetic model, with considerable degradation of 95.6% and 83.5%, respectively, after 14 days of single treatment at the recommended rate. According to the terminal results, it is advisable to wait for 7 days after applying the recommended dose of Switch fungicide before harvesting. The findings indicated that the presence of cyprodinil and fludioxonil residues in green onions did not pose a significant dietary risk for consumers. This study is intended to ensure the safe and proper use of cyprodinil and fludioxonil in green onions in Egypt.

Mathematical Modeling of Fluidized Bed Magnetizing Roasting of Iron Ore Fines

The fluidized bed magnetizing roasting of low‐grade iron ore fines is employed as a beneficiation technique in iron‐making and steel‐making industries. In the present work, the unreacted shrinking core reaction kinetic model is coupled with the two‐fluid and kinetic theory of granular flow gas–solid flow model to simulate magnetizing roasting of hematite to magnetite in iron ore fines using a fluidized bed reactor. The model is validated with published experimental findings. Thereafter, the influence of different process parameters such as gas temperature, composition, velocity, and particle size on the reduction fraction and rate along with mass fraction and emission is studied. The reduction rate increases with gas temperature and mass fraction while it decreases with particle size. The emission increases with gas temperature, particle size, and mass fraction. However, the influence of gas velocity on these parameters is not significant. The reduction rate and time vary from 0.0010 to 0.0067 s−1 and 65 to 553 s, respectively, at a reduction fraction of 0.5. The mass fraction and emission range from 0.80 to 0.92 and from 0.63 to 4.14 g kg−1 ore, respectively.

Microblog‐Assisted Synthesis of Schiff Base Network Polymers for SO2/Epoxide Copolymerization and Thermal Degradation Kinetics of the Products

AbstractThis study successfully prepared three environmentally friendly Schiff base network (SNW) polymers, SNW‐1, SNW‐2, and SNW‐3, using melamine and aldehyde compounds as raw materials through a microwave‐assisted synthesis method. The SNW materials were applied to catalyze the copolymerization reaction of SO2 and epoxides. Through detailed analysis of the chemical structure and properties of SNW‐1, SNW‐2, and SNW‐3, their catalytic efficiency was thoroughly investigated. Three thermal degradation kinetic models, Flynn–Wall–Ozawa (FWO), Kissinger, and Coats–Redfern, were employed to calculate the kinetic parameters of the thermal degradation of poly(cyclohexene sulfite) (PCS). Potential thermal degradation mechanisms were speculated. Additionally, the Kissinger model accurately described the thermal degradation kinetics features of PCS. Based on experimental results and kinetic analysis, this paper elucidates the potential mechanism of the copolymerization reaction of SO2 and epoxides. The study indicates that microwave‐assisted synthesis exhibits convenience and high efficiency in preparing efficient catalysts, demonstrating significant potential across various application domains.

Kinetic Model of the Synthesis of Methyl-tert-Butyl Ethers in the Presence of HY and CuBr2/HY Zeolite Catalysts

Kinetic Model of the Synthesis of Methyl-tert-Butyl Ethers in the Presence of HY and CuBr2/HY Zeolite Catalysts