Semi-empirical Kinetic Model Research Articles

Kinetic modelling of UVC and UVC/H2O2 oxidation of an aqueous mixture of antibiotics in a completely mixed batch photoreactor

The removal kinetics of an aqueous mixture of thirteen antibiotics (i.e., ampicillin, cefuroxime, ciprofloxacin, flumequine, metronidazole, ofloxacin, oxytetracycline, sulfadimethoxine, sulfamethoxazole, sulfamethazine, tetracycline, trimethoprim and tylosin) by batch UVC and UVC/H2O2 processes has been modeled in this work. First, molar absorption coefficients (ε), direct quantum yields (Φ) and the rate constants of the reaction of antibiotics with hydroxyl radical (kHO•) (model inputs) were determined for each antibiotic and compared with literature data. The values of these parameters range from 0.3 to 21.8 mM−1 cm−1 for ε, < 0.01 to 67.8 mmol·E−1 for Φ and 3.8 × 109 to 1.7 × 1010 M−1 s−1 for kHO•. Second, a regression model was developed to compute the rate constants of the reactions of the antibiotics with singlet oxygen (k1O₂) from experimental data obtained in batch UVC experiments treating a mixture of the antibiotics. k1O₂ values in the 1–50 × 106 M−1 s−1 range were obtained for the antibiotics studied. Finally, a semi-empirical kinetic model comprising a set of ordinary differential equations was solved to simulate the evolution of the residual concentration of antibiotics and hydrogen peroxide (model outputs) in a completely mixed batch photoreactor. Model predictions were reasonably consistent with the experimental data. The kinetic model developed might be combined with computational fluid dynamics to predict process performance and energy consumption in UVC and UVC/H2O2 applications at full scale.

Development of a novel semi-empirical kinetic model applied to photocatalysis under UVC and solar radiation

Development of a novel semi-empirical kinetic model applied to photocatalysis under UVC and solar radiation

Hardwood Branch Char Gasification with CO2: Characterization of Reactivity and Proposal of a Semiempirical Kinetic Model

Hardwood Branch Char Gasification with CO₂: Characterization of Reactivity and Proposal of a Semiempirical Kinetic Model

Study on semi-empirical kinetic model of serial compound gasification process for high moisture solid waste

Study on semi-empirical kinetic model of serial compound gasification process for high moisture solid waste

Experiments and modeling of fluidized bed steam-biomass char gasification with a red-mud oxygen carrier at particle scale for chemical looping

Chemical Looping Combustion (CLC) of biomass provides a low-cost way for CO2 negative emission. It creates complex multi-component flows including solids of oxygen carrier and fuel, and gasses of steam and/or CO2 as well as other gasification products. Experiments and modeling of steam-gasification of biomass char were investigated using a low-cost red mud as oxygen carrier materials. Effects of temperature, steam concentration, H2 inhibition on chemical reaction kinetics and mass transfer were experimentally investigated and modeled. A self-designed macro-TGA was used to detect its oxidization kinetics under isothermal conditions. The red mud oxygen carrier reduced inhibitory effect of H2 on carbon reaction, thus enhancing char conversion remarkably. With the neglect of the external mass limitation on char conversion, the reaction kinetics during reduction process was calculated by an experimentally-fitted function, expressing the char conversion. Pore structure evolution during the char conversion on kinetics was considered and its function was obtained based on the experimental results. The radial gas profiles under the bed of red mud particles by the solution of interparticle and external mass transfer coupled with the kinetics of char gasification were obtained, revealing the whole process of char conversion in CLC process. A semi-empirical kinetic model, including both of chemical and diffusion processes, provided a good insight of oxidation reaction kinetics, which was proven to be better than the classic models. The experimental data and modeling results got high agreement in both reduction and oxidation reactions.

An improved gasification kinetic model for biochar with high alkali and alkaline earth metals content

In this study, to investigate the effect of medium temperature devolatilization (MTD) on biomass gasification kinetics and build an improved kinetic model that can accurately describe the gasification of MTD-char, the isothermal steam gasification experiments were performed by using a thermogravimetric analyzer on corn stalk and its MTD-chars obtained at 200–550 °C. The results demonstrate that the wide divergence in the influences of alkali and alkaline earth metal (AAEM) on the gasification under different conversion rates (x) led to the fitting error of the random pore model for corn stalk gasification process, and this fitting error was more significate in the MTD-char with higher AAEMs content. Accordingly, a semi-empirical kinetic model, namely RPM+, which is suitable for biomass gasification with high AAEMs content, especially the MTD-char, was developed, the catalytic effects of AAEMs on biomass gasification were accurately described by the mutual coupling of AAEMs content, x and an activity parameter (ka) in RPM+. This study is of great significance to the process simulation and equipment design of biomass staged gasification. The results provide the theoretical foundation for realizing the high-value utilization of biomass with high AAEMs content through gasification.

A novel control system approach to enhance the efficiency of solar photo-Fenton microcontaminant removal in continuous flow raceway pond reactors

This work presents a control approach for the continuous flow operation of the solar photo-Fenton process in raceway pond reactors designed for micropollutant (MP) removal from urban wastewater treatment plant secondary effluents. The control system was designed using the mechanistic and semiempirical kinetic model of the photo-Fenton process at acidic pH developed and validated in previous work. Afterwards, a simulation study to demonstrate the viability of the control system was conducted under different operating conditions (hydraulic residence time and liquid depth) for solar irradiance and water temperature variation over the year. Two liquid depths (10 and 20 cm) and two hydraulic residence times (15 and 30 min) were selected as operating conditions to study the system performance for different MP removal control setpoints (70 % and 90 %). For 90 % MP removal setpoint, cost efficiency reductions of up to 21 % were reached, which denotes that the process efficiency is significantly influenced by the control setpoint. This is because highly demanding MP removal setpoints are achieved through high non-linear reagent consumption, resulting in low operating cost efficiencies of the process. On the other hand, cost efficiency improvements from 45 to 50 % were achieved when an 70 % MP removal setpoint was adopted, when comparing the manual operation of the process with the automatic mode. The presented results demonstrate not only the feasibility of implementing an automatic approach for the solar photo-Fenton process, but also the need for an optimised, efficient and controlled operation to upgrade its competitiveness versus conventional technologies.

Kinetics Study of Alumina Leaching from Ogbunike Clay Using Hydrochloric Acid

The kinetics study of alumina leaching from ogbunike clay was carried out using a solution of hydrochloric acid (HCl) for alumina dissolution. Variations in process parameters such as calcination temperature, leaching temperature, acid concentration, particle size, and solid-to-liquid ratio were considered for the leaching of alumina. The shrinking core model was used to analyze the experimental data. Alumina removal is feasible with 24.035% extractable alumina, and this can improve the economic value of ogbunike clay, which can be an alternative raw material in Nigeria’s aluminum industries. According to the data the dissolution rate increases with increasing calcination temperature, leaching temperature and acid concentration and decreasing particle size and solid-to-liquid ratio. The statistical and graphical analysis revealed that the dissolution followed the product layer diffusion-controlled semi-empirical kinetic model. The activation energy was calculated to be 18.36 kJ/mol for HCl. The optimum conditions for the dissolution of the alumina in HCI include activation temperature of 700 ⁰C for 60 minutes, leaching temperature of 90 ⁰C, HCl concentration of 3 M, particle size of 75 µm, and the solid-liquid ratio of 0.2 g/ml yielding the alumina dissolution rate of 84.72%. The kinetic data can be used to construct large-scale manufacturing equipment.

Continuous Synthesis of 5-Oxohexanenitrile in a Microreactor: From Kinetic Study to Reactor Modeling

Synthesis experiments of 5-oxohexanenitrile through the addition of acetone to acrylonitrile at the temperature range of 200–230 °C were carried out in a microreactor. Based on the experimental data, a semiempirical kinetic model was established and validated. According to the developed kinetic model, the effects of the molar ratio of acetone to acrylonitrile, the concentration of N-propylamine, and the initial water content were further investigated. By coupling the semiempirical kinetics with the plug flow reactor model, studies on the effect of the reactor diameter, the residence time, and the reaction temperature were performed to shed some light on the design and optimization of the industrial tubular reactors for the production of 5-oxohexanenitrile.

Influence of tetraalkylammonium salts on the adsorption kinetics of bovine serum albumin in aqueous solutions at the air-liquid interface

Bovine serum albumin adsorption dynamics in water and in aqueous solutions of tetramethylammonium bromide, hexyltrimethylammonium bromide octyltrimethylammonium bromide, decyltrimethylammonium bromide, and dodecyltrimethylammonium bromide at the air-liquid interface was studied at a temperature of 298.15 K.The kinetics of the adsorption process of the biomolecule in water and in the aqueous alkylammonium solutions was investigated following the changes in surface tension with time. The measurements were performed on a high-precision drop volume tensiometer.The surface pressure data were adjusted with two of the most used semi-empirical kinetic models that describe the process of adsorption and allow the determination of the equilibrium adsorption parameters.The results in water and in the aqueous solutions containing tetraalkylammonium salts show that the adsorption kinetics is well described by a model consisting of three steps in which the transport of the protein in the initial stage is diffusion controlled. After some time, the rate is determined by the adsorption and the penetration of the protein at the air-liquid interface and the rearrangement of the protein at the interface; the evolution of both processes is described by steps that follow first-order rate equations.The results indicate that the overall adsorption process of bovine serum albumin BSA in water and the aqueous alkylammonium salts solutions is controlled by the second step which is the slowest of the three steps; it corresponds to the adsorption and penetration of the biomolecule at the air-liquid interface.

A novel sub-pilot-scale direct-contact ultrasonic dehydration technology for sustainable production of distillers dried grains (DDG)

DDG is a major source of protein, calcium, phosphorus, and sulfur is arguably the most important byproduct of the bioethanol industry with increasing demand over the past few years. Reducing energy consumption in the DDG production process and energy recovery from DDG is vital for sustainable bioethanol productions. In this paper, a novel direct-contact multi-frequency, multimode, and modulated (MMM) ultrasonic dryer (US) was developed for the first time and has been applied in dehydration of wet distillers’ grain (WDG). Ultrasonic drying (US) was combined with a convective airflow (HA) at different temperatures of 25 (room temperature), 50 and 70 °C to evaluate the impact of US, HA, and US + HA on drying kinetics, activation energy, chemical compositions, microstructure, and color of DDG. Semi-empirical kinetic models were developed and evaluating drying performances showed that the application of ultrasound significantly enhanced the drying rate and decreased the drying time (by 46%), especially at low drying temperatures. The activation energy for moisture removal in the presence of ultrasound was about 50% of that without ultrasound. The final dried distillers' grains product processed by ultrasonic drying had a brighter color, a higher available protein, a higher digestible protein (the lowest acid detergent insoluble crude protein), and a better surface profile with no compromise on minerals and fiber contents.

Industry-scale production of a perovskite oxide as oxygen carrier material in chemical looping

How to upscale the production of oxygen carrier particles from laboratory level to industrial level is still challenging in the field of chemical looping. The upscaled oxygen carrier must maintain its physical and chemical properties. In the present contribution, a spray drying granulation protocol was developed to produce a perovskite oxygen carrier (CaMn0.5Ti0.375Fe0.125O3-δ) at an industrial scale. The micro-fluidized bed thermogravimetric (MFB-TGA) experiments were performed to measure the oxygen uncoupling and redox reaction kinetics under the fluidization state with enhanced heat and mass transfer, and the obtained experimental data at different temperatures were fitted by a fluidized-bed reactor coupled with a semi-empirical kinetic model. The physical and chemical properties of granulates were compared with those of the same perovskite composition prepared at the laboratory level. The results show the volume fraction of particle size at 75–500 μm is greater than 90% for the upscaled granulats, and the particles show no degradation in reactivity and no agglomeration for more than 20 redox cycles at high temperatures. The heterogeneous reaction rates are high, especially for the oxidation, e.g. it only spent ∼ 5 s to achieve full oxidation. Low attrition index of 3.74 wt% was found after the five-hour attrition test. The industrial-scale particles possess similar chemical and physical properties as the laboratory-scale particles with regards to the reaction kinetics, attrition index, crystalline phase, etc. The required bed inventories and fan energy consumption were finally estimated and found to be lower than other oxygen carriers reported in the literature.

Machine learning for high-fidelity prediction of cement hydration kinetics in blended systems

The production of ordinary Portland cement (OPC), the most broadly utilized man-made material, has been scrutinized due to its contributions to global anthropogenic CO2 emissions. Thus — to mitigate CO2 emissions — mineral additives have been promulgated as partial replacements for OPC. However, additives — depending on their physiochemical characteristics — can exert varying effects on OPC’s hydration kinetics. Therefore — in regards to more complex systems — it is infeasible for semi-empirical kinetic models to reveal the underlying nonlinear composition-property (i.e., reactivity) relationships. In the past decade or so, machine learning (ML) has arisen as a promising, holistic approach to predict the properties of heterogeneous materials, even without an across-the-board comprehension of the underlying composition-properties correlations. This paper describes the use of a Random Forests (RF) model to enable high-fidelity predictions of time-dependent hydration kinetics of OPC-based systems — more specifically [OPC + mineral additive(s)] systems — using the system’s physiochemical attributes as inputs. Results show that the RF model can also be used to formulate mixture designs that satisfy user-imposed kinetics-related criteria. Lastly, the presented results can be expanded to formulate mixture designs that satisfy target kinetic criteria, even without knowledge of the underlying kinetic mechanisms.

Selective electrochemical extraction of copper from multi-metal e-waste leaching solution and its enhanced recovery mechanism

Recycling activity for waste electrical and electronic equipment is always accompanied with leaching solution containing copper. Its selective extraction is of environmental and economic significance, and is beneficial for subsequent resource purification procedure. Compared with techniques such as chemical precipitation and solvent extraction, potentiostatic electrodeposition is outstanding with the advantage of high selectivity, electron as clean reagent, and minimal chemical usage. However, key factors affecting copper electrodeposition behavior as well as its kinetic process remain unclear, which blocks its further application. In this study, selective copper electrochemical extraction from multi-metal leaching solution of waste liquid crystal display panels is explored. Copper electrodeposition is analyzed from electrochemical and mass transport point of view, and the main results are summarized: (i) copper can be first electrodeposited due to its higher reduction potential compared with indium; (ii) applied potential and agitation are the most influential factors towards space-time yield and current efficiency; (iii) a semi-empirical kinetic model could quantitatively describe the influence of agitation and the time-current-concentration relationship. The model-predicted extraction rate agreed well with experimental data throughout electrodeposition; (iv) electrodeposition experiments show over 95% of copper can be selectively extracted as ultrafine copper powder (~150 nm) at 0.05 V (vs. SHE).

Functionalized magnetic nanoparticles Fe3O4@SiO2@PTA (PTA = (2-pyrimidylthio)acetic acid) for efficient removal of mercury from water

Functionalized magnetic nanoparticles were prepared by anchoring (2-pyrimidylthio)acetic acid on to the surface of the silica coated Fe3O4 (Fe3O4@SiO2) nanoparticles by acid amide coupling reaction. These nanoparticles were characterized on the basis of powder-XRD, FTIR, FESEM, HRTEM and EDX analysis. The adsorption property of these functionalized nanoparticles (Fe3O4@SiO2@PTA) was investigated in water with a large number of metal ions and anions, which revealed that it selectively adsorbs Hg2+ with high efficiency (920 mg/g). The desorption of Hg2+ from Fe3O4@SiO2@PTA-Hg2+ was successfully carried out with the aid of EDTA and the process was repeated three times successfully to examine its reusability. The adsorption of Hg2+ was also investigated with the variation of pH in the range 2–8 and maximum adsorption was noted at the pH 7.0. Detail study on adsorption suggests that out of the two adsorption isotherm models, Langmuir and Freundlich, the former one (Langmuir) fits better in this case. Detail kinetic study on the adsorption process was also carried out and the data fitted with both the two semi-empirical kinetic models, pseudo-first-order and pseudo-second order, out of which the pseudo second-order model exhibited excellent fitting with correlation coefficient R2 = 0.99 for all concentrations of Hg2+. Finally, on the basis of experimental data, the mechanism for interaction of Hg2+ with Fe3O4@SiO2@PTA nanoparticle is discussed.

Leaching kinetics of potassium and aluminum from phosphorus-potassium associated ore in HCl-CaF2 system

The leaching behaviours of potassium and aluminum from phosphorus-potassium associated ore in HCl-CaF2 media were investigated at temperature from 60 to 90 °C. The higher dissolved fraction of potassium compared with aluminum was found in this study though they were mainly incorporated into the same mineralogical phase of potash feldspar in the ore. Moreover, the dissolved fraction of potassium was always higher than aluminum in all the investigated conditions due to the existence of secondary precipitation phase such as amorphous alumino-silicate or the formation of insoluble AlF complex in the leaching process. In addtion, the leaching kinetic data were successfully examined by a semiempirical kinetic model based on the classical shrinking core model. It was found that there are two distinct stages in the leaching process and the kinetics of both stages follows the semiempirical kinetic model with chemical reaction being the rate-controlling step. The activation energies for potassium and aluminum from the ore were 39.031 and 44.260 kJ·mol−1 at first leaching stage, and 59.274 and 62.944 kJ·mol−1 at second leaching stage, respectively.

Using natural systems evidence to test models of transformation of montmorillonite

Safety functions for the clay buffer in a repository for high-level radioactive waste (HLW) are fulfilled if the presence of montmorillonite with high swelling capacity and low permeability is maintained in the long-term. The transformation of montmorillonite to the non-swelling mineral illite is addressed in most safety assessments by using simple semi-empirical kinetic models, but this approach contrasts with all other near-field geochemical modelling activities that employ a full description of thermodynamic and kinetic mineral-fluid processes. The consistency of these two modelling approaches has been studied by simulating the montmorillonite to illite transformation in the marine sediment profile penetrated by the Ocean Drilling Program (ODP) Site 1174, offshore Japan. Illite in mixed-layer smectite-illite increases from 20% at <700 m below seafloor (mbsf) to 89% at 1100 mbsf. Illitization of smectite at Site 1174 using the semi-empirical approach has been shown by previous authors to provide a satisfactory match to the gradual change of illite content with depth, albeit with significant differences between model variants.In comparison, the approach used in the current study was to simulate the mineralogical and fluid chemical evolution of a ‘packet’ of a typical fluid-saturated sediment using a model involving full kinetic and thermodynamic treatment of mineral dissolution-precipitation reactions, along a temperature-time burial curve defined by published thermal conductivity data for Site 1174. The results of these simulations showed that the onset of illitization at a depth of 700 mbsf could be matched, but that the overall rate of conversion was significantly more rapid than observed, or as modelled by the simple semi-empirical kinetic approach. The onset and rate of illite growth was strongly linked to the rate of transformation of amorphous silica to quartz. Geochemical model simulations therefore err on the side of conservatism, but may produce unrealistic estimates of illitization. This comparison demonstrates that models involving full kinetic and thermodynamic treatment of mineral dissolution-precipitation reactions must be carefully applied to simulate other transformation reactions of montmorillonite relevant to the geological disposal of HLW, such as those arising from the interaction of montmorillonite with iron/steel, cement and/or groundwater.

Homogeneous synthesis of hydroxylamine hydrochloride via acid-catalyzed hydrolysis of nitromethane

A continuous homogeneous synthesis of NH2OH·HCl was achieved and well described with a segmented semi-empirical kinetics model.

Hydrogen production from palm kernel shell: Kinetic modeling and simulation

The hydrogen production process from palm kernel shell (PKS) is modeled and simulated by a steady-state gasification system using Aspen PLUS®. The kinetic parameters of the gasification are determined by employing thermogravimetric analysis (TG/DTG) using two gasifying agents (CO2 and steam) and applying three semi-empirical kinetic models to interpret the experimental results (linear model, grain model, and volumetric model). The process was subjected to different temperatures (750–950 °C) and different compositions of the steam/biomass ratio (S/B) (0–2.5). It is obtained that the linear model and the grain model have the best R2 with the gasification results of the PKS with steam (0.966) and CO2 (0.965), respectively. The steam reaction kinetic parameters obtained were E=125.79KJ/mol and A=26.23s−1, and for the reaction with CO2, they were E=99.87KJ/mol andA=6.3s−1. The production yield of H2 (109 g H2/PKS kg) is reached at the highest temperature (950 °C) and the lowest S/B ratio (0). It is concluded that the model can predict with greater precision the hydrogen composition in the syngas, with a 0.135 mean square error, compared to other authors that present a 0.282 mean square error.

Predicting the solubility enhancement of amorphous drugs and related phenomena using basic thermodynamic principles and semi-empirical kinetic models.

The accurate prediction of the solubility enhancement offered by neat amorphous drugs and amorphous solid dispersions, over their crystalline (API) counterparts, has been discussed in several landmark works dating back at least two decades. Against this backdrop, an assessment of the current state-of-the-art for rigorously, yet simply (circumventing computational methods), determining the amorphous:crystalline solubility ratio based on thermo-analytical quantities is presented herein. Included in this work is a brief survey of the literature together with a discussion of the advantages and shortcomings of some of the most popular approaches, to-date. While the focus is on neat amorphous drugs, both before and after moisture sorption, the methodology presented is readily extended to more complex (e.g. ternary) systems that form a single, homogeneous phase. Six key questions are addressed in the context of how to most accurately determine the amorphous:crystalline solubility ratio: (1) How is the lattice energy of the crystalline phase assessed? (2) What is the role of heat capacity? (3) How does the pKa impact the solubility ratio prediction (for ionizable drugs)? (4) How does one incorporate the effects of moisture sorption on the amorphous phase? (5) How might one characterize (predict) the rate of drug recrystallization under various conditions (since the duration of the solubility enhancement is a kinetic phenomenon)? (6) What is the best approach for linking the (loss in) solubility enhancement to the Tg-lowering of the amorphous drug (by water) and vice-versa? In addressing these questions, this work aims to put forth a standardized methodology for determining the amorphous solubility enhancement with improved accuracy.