•The kinetics of CO2 adsorption/desorption of a magnetite-based sorbent was studied.•Dynamic breakthrough experiments were performed in a lab-scale fixed bed reactor.•Pseudo-first order, ...pseudo-second order, and Avrami’s kinetic models were applied.•Film diffusion, intraparticle diffusion and surface reaction are the main diffusion mechanisms involved.•The dynamic CO2 adsorption behavior has been investigated with a deactivation model.
The CO2 adsorption and desorption kinetics of a magnetite-based sorbent, CB-FM, obtained coating a low-cost carbon black (CB) with magnetite fine particles (FM), has been systematically and thoroughly investigated for the first time under post-combustion capture operating conditions. Experimental data of CO2 uptake (18–150 °C) and extent of CO2 desorption (200–260 °C) have been fitted to different apparent kinetic models, namely pseudo-first-order, pseudo-second-order and Avrami’s fractional-order kinetic models. The mechanism of CO2 adsorption on CB-FM in terms of controlling mass transfer resistances, interparticle diffusion, intraparticle diffusion and Boyd’s film-diffusion models has been also investigated. Finally, a two-constants deactivation model has been adopted to simulate the dynamic breakthrough curves.
In this paper, a new kinetic model considering both oxidation and volatilization kinetics is established and applied to analyze the oxidation of SiC-B4C-xAl2O3 ceramics and other systems in various ...oxidation conditions. The effects of diffusion area and volume changes during the oxidation process are considered in this model. The physical meaning of each parameter in this model is explicit and simple. According to this model, the diffusion coefficient of species and the corresponding diffusion activation energy are easily available. The practicability of this model is well verified by the experimental data of SiC-B4C-xAl2O3 and other systems oxidized under different conditions. In addition, the practice shows that the model is applicable not only to the systems where oxidation and volatilization coexist, but also to the system where only oxidation plays a major role. We hope the model proposed in this work can be used in other materials with more complex environments.
●A new kinetic model is established and applied to the oxidation analysis of various systems.●The model quantitatively considers the effects of oxidation and volatilization.●This more comprehensive model has wider application and better accuracy.
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•Adsorption empirical kinetic models and mass transfer kinetic models were reviewed.•The physical meanings and applications of 16 adsorption kinetic models were analyzed.•The model ...validity evaluation equations were summarized based on literature.•A user interface for solving kinetic models was developed based on Excel software.
Adsorption technology has been widely applied in water and wastewater treatment, due to its low cost and high efficiency. The adsorption kinetic models have been used to evaluate the performance of the adsorbent and to investigate the adsorption mass transfer mechanisms. However, the physical meanings and the solving methods of the kinetic models have not been well established. The proper interpretation of the physical meanings and the standard solving methods for the adsorption kinetic models are very important for the applications of the kinetic models. This paper mainly focused on the physical meanings, applications, as well as the solving methods of 16 adsorption kinetic models. Firstly, the mathematical derivations, physical meanings and applications of the adsorption reaction models, the empirical models, the diffusion models, and the models for adsorption onto active sites were analyzed and discussed in detail. Secondly, the model validity evaluation equations were summarized based on literature. Thirdly, a convenient user interface (UI) for solving the kinetic models was developed based on Excel software and provided in supplementary information, which is helpful for readers to simulate the adsorption kinetic process.
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•Acetaminophen removal in the Fe2+/persulfate system was comprehensively studied.•A kinetic model based on unsteady state was constructed to predict acetaminophen removal.•Both SO4− ...and HO contributed to acetaminophen removal and SO4− was the dominant oxidant.•Cl2− also accounted for the removal of acetaminophen in the presence of Cl−.•Degradation pathway of acetaminophen was proposed.
In this study, the removal of acetaminophen (ACT) in the Fe2+/persulfate system has been comprehensively evaluated. A kinetic model has been established based on the principal reactions. Good accordance between the experimental data and the predicted results under different operational conditions including molar ratio of Fe2+ to persulfate, initial pH, initial ACT concentration, the presence of chloride, under natural water matrices and the mixture of ACT, amoxicillin and pyridine, evidences the validity of the proposed kinetic model. The rate constants for ACT reacting with SO4− and HO were determined as (1.80 ± 0.17) × 109 M−1 s−1 and (3.26 ± 0.41) × 109 M−1 s−1, respectively. SO4− was evidenced to be the primary radical accounting for ACT removal through both kinetic model calculation and the scavenging results, using either methanol or tert-butyl alcohol. The optimum molar ratio of Fe2+ to persulfate for ACT removal was determined to be 5:4. The removal rate of ACT was little affected by initial pH due to the rapid decrease of solution pH caused by the hydrolysis of iron ions. Cl− has a dual effect on the removal of ACT, and Cl2− rather than SO4− is proposed as the dominant radical for ACT removal at 10.0 mM Cl−. Possible degradation pathways are also proposed based on the detected intermediates.
•Revised workflow to determine biomass compositions via thermogravimetric analysis.•Improved independent parallel reaction model by constraining parameter boundaries.•The biomass tested was pine, ...birch, and oak woods, switchgrass, and pine bark.•The compositions using the new method were within 8 wt% of the literature values.
The determination of biomass composition via thermogravimetric analysis (TGA) has been a subject of considerable interest for many years. The current work proposes a revised workflow for determining the amounts of cellulose, hemicellulose, and lignin in biomass by combining TGA under an inert atmosphere with analyses of extractives and ash. An independent parallel reaction (IPR) model used for the deconvolution of the derivative thermogravimetry data was improved by constraining model parameters, i.e., thermal decomposition kinetic parameters and char fractions of cellulose, hemicellulose, and lignin, with values compiled from the literature using statistical analysis. The workflow is developed and demonstrated using cellulose and starch mixtures and then applied to biomass with varying levels of ash, including pine, birch, and oak wood, switchgrass, and pine bark. Using extractive-free biomass in the new TGA-IPR workflow improved the composition results compared with untreated biomass. The compositions determined by this method agreed well with values reported in the literature (within approx. 8 wt%) for the tested samples. The results demonstrate improved biomass composition accuracy using an accessible and rapid TGA-based approach.
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The properties of metal hydride materials will be significantly degenerated by the poisoning effect of impurity gases such as CO, O2, H2S, etc. However, there are few reports on the poisoning kinetic ...model of metal hydride, which is important for the high-purity hydrogen purification and production from industry H2-contained waste gas. Hence, in this work, a novel poisoning hydrogen absorption kinetic model for metal hydride running in the CO + H2 mixture gas is developed, which considers the effect of poisoning on the volume growth rate of the product phase based on classical Johnson-Mehl-Avrami model. The novel model is also validated by comparison with experimental data of hydrogen absorption of LaNi4.3Al0.7 in a hydrogen atmosphere containing CO (∼0.1% v/v). The comparison results showed good agreement between model and experiment in the temperature range of 323–403 K. Based on experimental data and model, the reaction mechanism and rate-controlling steps of LaNi4.3Al0.7 hydrogenation process with 0.1%v/v CO were further uncovered.
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•A novel poisoning hydrogen absorption kinetic model is developed and validated.•The poisoning factor related to the temperature is introduced into the kinetic model.•The effect of impurities becomes weakened with the rise of temperature.•Hydrogenation rate-controlling step under CO + H2 depends on surface CO absorption/desorption.
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•A general kinetic model of biomass supercritical water gasification was developed.•The kinetic model was validated successfully based on results from real biomass.•Temperature played ...the most important role in producing gaseous species.•The effect of residence time on gas formation was found to be minor.•SCWG of lignin produced the highest yield of hydrogen.
Supercritical water gasification (SCWG) utilizes water as the reaction medium to convert biomass into a mixture of gases (i.e., H2, CO2, CO, CH4, and other short-chain hydrocarbons) at typical operating temperature ≥ 400 °C and pressure ≥ 23 MPa. Understanding kinetics of SCWG processes is critically important for future development and scale-up application of the SCWG technology. Thus, this study aimed to develop a general kinetic model to predict the yields of gases from SCWG of various lignocellulosic feedstocks with varying contents of cellulose, hemicellulose and lignin. The model was established based on the experimental results from K2CO3-catalyzed SCWG of various biomass model compounds including cellulose, xylan and lignin at 450–550 °C for 10–50 min, followed by validation of the model using the experimental data obtained from SCWG of real biomass (i.e., corn stalk and pinewood) under same reaction conditions. The validation results showed that the general kinetic model developed could accurately predict the yields of gases from real biomass SCWG and the quantitative influences of temperature and residence time on the gas yield in biomass SCWG. Additionally, the kinetic model has been validated other SCWG data in the literature obtained with various facilities and different lignocellulosic biomass feedstocks. The development of the general kinetic model provides an applicable way to assess the potential of SCWG of various lignocellulosic biomass feedstocks for producing combustible gases at various conditions.
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Organic dye pollution in the water environment is a problem of global concern. Adsorption is demonstrated as a promising technology to remove organic dyes from wastewater, in which ...the development of highly-efficient adsorbents is still the challenging task. Herein, we reported the facile fabrication of polyamine-based cyclophosphazene hybrid (PCP-NH2) hollow microcapsules with cross-linked structure, generated by one-step precipitation polymerization between hexachlorocyclotriphosphazene and branched polyethyleneimine, and subsequent acetone treatment. Their morphology, composition and structure were confirmed by SEM, TEM, FTIR, TGA, and XPS. The endowment of hollow PCP-NH2 microcapsules as potential adsorbents were thoroughly evaluated using eight organic dyes with different surface charges. The adsorption action of hollow PCP-NH2 microcapsules highly depends on the surfaces charges, exhibiting highly-efficient and selective adsorption behavior towards anionic dyes. Especially, The adsorption capacity of the hollow PCP-NH2 microcapsules towards anionic dyes of EY, ACBK, MO and EB reaches up to 1196.36, 1190.65, 1142.77 and 1040.92 mg/g at 25 °C, respectively. The adsorption kinetics shows a better fit to pseudo second-order kinetic model, compared to pseudo-first-order kinetic and Weber’s intraparticle diffusion models. The adsorption equilibrium data followed the Langmuir isotherm well. The adsorption thermodynamic experiments demonstrated that adsorption was a physisorption process with endothermic and spontaneous characteristic.
To better design and optimize the separation process of plant essential oils obtained by microwave-assisted hydrodistillation, it is necessary to fully understand the kinetic mechanism and ...appropriate mathematical representation of the separation process. In this paper, the kinetic models, including first-order kinetic models, second-order kinetic models, two-site kinetic models, power-law models, Peleg models, and Elovich model, for the separation of essential oils by microwave-assisted hydrodistillation are introduced, and try to explain the kinetic behavior of this method for the separation of essential oils through the assumptions, parameters and application examples of the kinetic model. Meanwhile, the most suitable kinetic models were screened according to the kinetic mechanism of essential oils obtained by this method, although these kinetic models all showed a high coefficient of determination, only first- and second-order kinetic models can reproduce the kinetic mechanism of this method under specific conditions. In addition, the effects of microwave irradiation power, liquid-solid ratio, moisture content, and particle size on the kinetic model parameters are discussed and analyzed, then the extraction rate constants, equilibrium yields, and coefficients of determination in the kinetic models all change with these factors. Therefore, it is necessary to explore new kinetic models to more comprehensively understand the kinetic mechanism of the separation of essential oils by this method, which has guiding significance for the optimal design of essential oil separation methods and the utilization of high-value processing.
•The MHD method can be approximated as only two simultaneous mechanisms.•First- and second-order kinetic models can well fit the MHD under certain conditions.•Kinetic model parameters are affected by the essential oil separation conditions.•Essential oils isolated by the MHD method are mainly derived from broken plant cells.•Adverse results such as thermal decomposition affect the kinetic mechanism of MHD.
