This work aimed to describe the adsorption of volatile organic compound (VOC) vapor from gas streams onto WG-12 activated carbon modified with DL-malic acid. The properties of adsorbents were studied by thermogravimetric (TG) analysis, total acidity, total basicity, and elemental analysis. The adsorption behaviors of acetone and ethyl acetate for activated carbons modified with dl-malic acid were investigated at normal pressure in a fixed bed reactor. Breakthrough curves for each adsorbate were performed using gas chromatography analysis with a flame ionization detector. The adsorption capacity of acetone was within the range of 33–107 mg/g, while that for ethyl acetate was 61–277 mg/g, which indicated a higher adsorption affinity of WG-12 toward ethyl acetate. Results showed that the adsorbate molecules compete for adsorption sites, indicating the occurrence of competitive adsorption. We also found that the most effective adsorbent for the tested VOCs is WG-12 modified with dl-malic acid in the amount of 0.2 g per gram of the unmodified adsorbent and heated at 500 °C. These results will develop a purification process and reduce volatile organic compounds’ emissions.

This study aimed to describe the adsorption process of ortho-dichlorobenzene (o-DCB) onto activated carbons (ACs) and modified carbon nanotubes (CNTs) from the aqueous phase. The starting material NC_7000 carbon nanotubes were modified by chlorination (NC_C) and then by the introduction of hydroxyl groups (NC_C_B). The concentration of o-DCB in solutions was performed by UV-VIS spectrophotometry. After adsorption, the activated carbons were regenerated by extraction with organic solvents such as acetone, methanol, ethanol, and 1-propanol; the carbon nanotubes were regenerated by methanol. The degree of adsorbate recovery was determined by gas chromatography (GC) with flame ionization detection, using ethylbenzene as an internal standard. The equilibrium isotherm data of adsorption were satisfactorily fitted by the Langmuir equations. The results indicate that carbon adsorbents are effective porous materials for removing o-DCB from the aqueous phase. Additionally, activated carbons are more regenerative adsorbents than carbon nanotubes. The recoveries of o-DCB from ACs were in the range of 76–85%, whereas the recoveries from CNTs were in the range of 23–46%. Modifications of CNTs affect the improvement of their adsorption properties towards o-DCB compared to unmodified CNTs. However, the introduction of new functional groups on carbon nanotube surfaces makes the regeneration process less effective.

This work aimed to evaluate the effect of activated carbon modifications on the adsorption of volatile organic compound vapors. In this study, two commercial activated carbons WG-12 and DT0 (Grand Activated Sp. z o.o.) were modified by melamine and dl-malic acid and heat treatment. Then, the activated carbons were used as adsorbents in the adsorption of a gaseous mixture of four volatile organic compounds (acetone, ethyl acetate, toluene, n-butyl acetate) from the air. The properties of modified adsorbents were described using thermogravimetric analysis, elemental analysis, Boehm titration, and iodine number. Adsorption processes were characterized by breakthrough curves, velocities of the sorption front migration, and the Yoon–Nelson model. The study showed that surface modifications of activated carbons affect the adsorption properties of a mixture of acetone, ethyl acetate, toluene, and n-butyl acetate. The introduction of nitrogen on the surface of the activated carbons did not significantly improve the adsorption efficiency. It was identified that increasing the degree of carbonization of the activated carbon favored the adsorption of the tested adsorbates. The adsorption process of this mixture occurs by diffusion and depends on the diffusion velocity of the adsorbate molecules in the pores. It has been demonstrated that the velocity of the sorption front migration is inversely proportional to the boiling point of the adsorbates. In addition, it was found that competitive adsorption takes place in this process. Modified adsorbents can be thermally regenerated with almost 100% efficiency and reused in the next adsorption process. Furthermore, the Yoon–Nelson model can be successfully used to describe the kinetics of this process up to the point of displacement.

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