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Evaluating the activated carbon filter's performance in removing gaseous pollutants is essential to determining the filter maintenance schedule for indoor environments. This paper describes the development of a mathematical model to predict an activated carbon filter's performance for removing mixtures of ozone and volatile organic compounds (toluene and limonene) at their low-level concentrations in typical indoor environments. Mass transfer equations were employed to estimate the filter's dynamic behaviour by including the reaction rates of ozone with carbon surfaces and the reactive volatile organic compound, as well as the adsorption isotherm for a single volatile organic compound or binary mixtures of volatile organic compounds. The reaction rate constant for the ozone-limonene reaction was calculated by fitting the model to the experiment results of their binary mixture at 9 ppm of limonene and 0.1 ppm of ozone. Additionally, the ozone-exposed filters at 0.1 ppm were used to perform adsorption tests to determine the parameters of the Dubinin-Radushkevich isotherm using experimental results at 9, 30, 50, 70, and 90 ppm of volatile organic compounds. The Dubinin-Radushkevich isotherm was extended using the volume exclusion theory to consider the effect of by-products on the removal modelling of the binary mixture of ozone and limonene and the ternary mixture of ozone, limonene, and toluene. The model was able to show the reduced accessibility of the surface of activated carbon for reaction with ozone because of the adsorption of volatile organic compounds and generated by-products (keto-limonene and carvone). The initial influence is of minor magnitude; however, as the surface load intensifies, its significance can progressively amplify over time. Pre-exposing the filter to ozone prior to conducting adsorption tests was able to capture the average change in the adsorption properties of the filter. These considerations in the modelling result in a remarkable predictive capability in determining the breakthrough behaviour of the filter in removing the binary or ternary mixture of ozone and volatile organic compounds at various concentrations. The insignificant effect of the homogeneous reaction between ozone and limonene for the investigated experimental setup was confirmed by comparing the predictions made by the proposed model with those made by another model that considers the homogeneous reaction. Finally, the sensitivity analysis revealed that the model is more sensitive to adsorption isotherm parameters compared to the reaction kinetic parameter between ozone and limonene. • The removal of mixtures of ozone and VOCs was predicted by a mathematical model. • The D-R isotherm was extended to include the effect of generated by-products. • The model was validated for binary and ternary mixtures of ozone and VOCs. • The importance of the gas-phase reaction was negligible for the tested system. • A sensitivity analysis was performed on parameters affected by measurement errors. [ABSTRACT FROM AUTHOR]

The application of high-area C-cloth electrodes as effective adsorbent materials in organic solvents and in aqueous/organic solvent mixtures was studied using aniline and pyridine as model adsorbate solutes. These were selected in relation to understanding the adsorption and electrosorption behaviours of organic pollutants in such aqueous/non-aqueous mixtures and to development of methodology for clean-up of organic solvents or industrial waste-waters. The adsorption/electrosorption processes were followed by in situ UV-spectroscopy which also provided dynamical data for easy kinetic analysis. Large differences in the (apparent) double-layer capacity of the C-cloth observed in ethanol (EtOH), n-propanol, and acetonitrile (MeCN), in relation to that in water, suggest the significance of differences of solution conductivity determining the distributed electrolytic resistance in the pores of the C matrix, as in the model of de Levie. Adsorption of both aniline and pyridine was found to be significantly promoted by either galvanostatic or potentiostatic polarization of the C-cloth electrode, as previously found for aqueous solutions. Introduction of organic solvents into aqueous solution was shown to have strong positive or negative effects on the electrosorption processes depending on the respective solvents and adsorbates used, and the role of hydrophobic effects in adsorption from aqueous media. A common enhancement of extents of adsorption of both aniline and pyridine in each of the organic solvents investigated was also found by measurements of adsorption on open-circuit followed by electrosorption upon polarization. [Copyright &y& Elsevier]

Removal of aniline, 2,2′-bipyridyl, 4,4′-bipyridyl and their protonated cations from dilute aqueous solutions, simulating polluted waste-waters, by adsorption and electrosorption at high-area carbon cloth (C-cloth) electrodes is described. The adsorption behaviour and kinetic parameters for rates of adsorption of these solutes at high-area porous-C electrodes were followed and evaluated in situ by means of UV spectrophotometry. The results obtained show that the above neutral adsorbates have stronger affinity over their protonated cations for the surface of C-cloth electrodes. Polarization of the C-substrate electrodes leads to a great increase in both rates and extents of adsorption for each of the adsorbates investigated but complete adsorptive removal of aniline and 2,2′-bipyridyl was attained only under certain conditions. The extents of adsorptive removal of the adsorbates and the rate-constants for such processes are summarized quantitatively. Polarization electrosorption under slow alternating positive/negative conditions or combination of open-circuit adsorption with polarizing electrosorption procedures dramatically enhanced the extents of adsorption in most cases, leading to complete removal of the adsorbate from solution in each of the cases of aniline, 2,2′-bipyridyl, 4,4′-bipyridyl and their singly protonated cations under various conditions. The latter observation is valuable for the development of methodologies for purification of industrial waste-waters. [Copyright &y& Elsevier]

Adsorptive/electrosorptive removal of pyidinium (PyH+), N-methylpyridinium (PyMe+), 1,4-pyrazine (Prz) and PrzH+, and 1-quinoline (Qul) and QulH+ from simulated waste-waters was investigated in 0.1 M H2SO4, 0.1 M KH2PO4+KOH (pH 7.0) buffer and 0.1 M KOH solutions using quasi-3-dimensional, high area C-cloth electrodes as interfaces. The adsorption/electrosorption, monitored kinetically by in situ UV spectrophotometric techniques, follows first-order kinetics. Rates of adsorption of the above N-heterocyclic solutes are enhanced by polarization of the C-electrodes, preferably by negative currents. Reversible electrosorption was observed in 0.1 M H2SO4 or in 0.1 M KH2PO4+KOH (pH 7.0) buffer solution for pyridinium cations (PyMe+ and PyH+), leading to the possibility of easy and in situ regeneration of the surfaces of C-cloth electrodes in practical adsorptive removal applications. Negative, and alternate positive and negative polarization were found to have a strong and particular effect in promoting extents of adsorption for N-heterocyclic compounds such as PyMe+, Prz and Qul in buffer (pH 7) and KOH solutions, leading to complete removal in those cases. [Copyright &y& Elsevier]

The adsorption and electrosorption/desorption behavior of pyridine (Py) was studied for potential applications to the purification of industrial waste-waters. The use of high-area carbon cloth (C-cloth) electrodes as quasi-3-dimensional interfaces, coupled with in situ UV–Vis spectrophotometric techniques and scanning kinetics for quantitatively monitoring the adsorption/desorption processes and simultaneously obtaining kinetic parameters are described. The conversion of Py to PyH+, which decreases the removal efficiency, takes place in non-buffered electrolyte solution due to pH changes but is eliminated in a HOAc+NaOAc buffer (pH 6.8) solution. Rapid and complete removal of Py is then achieved by anodic polarization. Under controlled potential, Py removal rates are lower than those for galvanostatic polarization where changes of potential arise due to double-layer charging. [Copyright &y& Elsevier]

• The Doong and Yang model was improved to be used for non-ideal mixture adsorption. • The gas-phase diffusion was confirmed to be insignificant for the tested systems. • Isotherm's curvature controls the selection of approximations for internal transfer. • As the inlet concentration increases, the breakthrough curves become steeper. • At higher velocities, 100% breakthrough times and initial efficiencies decline. Carbon-based filters are commonly used to remove volatile organic compounds from indoor air environments. Assessing the filter performance, such as its ability to remove specific pollutants or its efficiency, is crucial to improve air quality in the indoor environment. However, conducting experiments to evaluate the performance of filters for removing volatile organic compounds from indoor air environments can be difficult and time-consuming due to their low indoor concentrations and the presence of complex mixtures of these pollutants. Dynamic models have been used to assist in evaluating the performance of filters for indoor environment applications. In this study, iterative and non-iterative methods were applied to the Dubinin-Radushkevich isotherm, and then they were incorporated into the mass transfer models to represent the adsorption behaviour of a binary mixture of volatile organic compounds (toluene-limonene and toluene- methyl ethyl ketone mixture). Experimental results of binary mixtures containing 9 parts per million volume of each compound were used to measure Dubinin-Radushkevich constants in the iterative method, whereas single-component adsorption experimental results were used in the non-iterative method. Afterwards, the model's predictions were compared with the experimental results at 0.1 parts per million volume of each compound. The non-iterative method could predict the filter performance for the removal of the toluene and limonene mixture, but there was a systematic deviation for the binary mixture of toluene and methyl ethyl ketone. However, the iterative method, which considers the lateral interaction between the adsorbates, could predict the breakthrough of the filter for the non-ideal mixture of toluene and methyl ethyl ketone correctly. Comparative modelling confirmed the negligible significance of gas-phase diffusion. Also, the comparison between the comprehensive model (Fick's diffusion for internal mass transfer) and two approximate solutions (linear and quadratic driving force models for internal mass transfer) exhibited the applicability of these intraparticle mass transfer approximations in specific conditions. Finally, the parametric study showed that as the particle size increases, the 100% breakthrough time and initial breakthroughs increase for each component of the binary mixture. However, increasing the air velocity leads to a reduction in 100% breakthrough times and initial efficiencies. At higher inlet concentrations, the breakthrough curves become steeper. Furthermore, the occurrence of the overshoot phenomenon was observed with increasing thickness. [ABSTRACT FROM AUTHOR]