Predicting the Adsorption of Indoor VOCs onto Commercial Activated Carbon Based on Linear Solvation Energy Relationship

Abstract

Volatile organic chemicals (VOCs) are well-known indoor pollutants and are one of the top risks to human health. In this study, we chose commercial activated carbon (CAC) as adsorbents, which are used widely for the removal of indoor formaldehyde. The adsorption equilibria of six VOCs [benzene, toluene, p-xylene, chlorobenzene, acetone, and methyl ethyl ketone (MEK)] onto CAC at the environmentally relevant temperatures [35°C–55°C (308–328 K] were measured, and adsorption isotherms were fitted with the Dubinin-Astakhov (DA) equation. Molar polarizability, molar refraction, molar volume, and parachor were used to calculate the affinity coefficient (β), with benzene as the reference. The predicted results of the adsorption capacity with calculating characteristic energy (E) based on β were not applicable well for polar adsorbates because both nonspecific and specific interactions were included during their adsorption. Considering different types of adsorption interaction, we adopted the linear solvation energy relationship (LSER) approach to analyze adsorption interaction and predict E for VOCs adsorption. The results showed that adsorption capacities of VOCs could be predicted effectively, and the average root-mean-square error between the predicted and experimental data was 4.52%. Finally, we further predicted the adsorption capacity of benzene and acetone at a ppb concentration (<100 ug/L), which corresponded to the indoor concentration of VOCs. And the predicted results were verified by adsorption characteristic curves at 155°C and 175°C (428 and 448 K), with data at different temperatures and concentrations falling essentially onto a single curve. This study is meaningful because it presents a useful prediction method of adsorption capacities for VOCs with different properties on CAC more quickly and conveniently.