Adsorption of a Four-Component Mixture of Volatile Organic Compound Vapors on Modified Activated Carbons

Abstract

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.