Tuning the pore structure and hydrophobicity to unravel the adsorption mechanism of polycyclic aromatic hydrocarbons onto carbon materials

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in water, soil, and air, posing significant risks to human health. Yet little is known about whether the large molecular size of PAHs could hinder the understanding of their adsorption dynamics and the universality of the adsorption mechanism remains unclear. Low-cost adsorbents with different pore structures and hydrophobic properties were prepared, and the adsorption process and feasible adsorption sites of PAHs were investigated. The results showed that the more developed pore structure promoted the diffusion of PAHs. Adsorbents with high affinity for PAHs obtained better performance due to the π-π interaction and the sieving of groove areas formed by folds, and the equilibrium adsorption capacity was 99.9 and 98.9 mg/g for NAP, 9.42 and 9.53 mg/g for PHE, 0.929 and 0.887 mg/g for PYR. Meanwhile, the pseudo second-order kinetic model and Freundlich isotherm model could fit the actual adsorption process. Moreover, XlogP3 or E_HOMO emerged as good descriptors in QSAR. Hydrogen bond basicity and hexadecane-air partition coefficient of organic pollutants play a dominant role in the adsorption stage. This study lays a theoretical foundation for screening adsorbents and provides novel support to explore the adsorption mechanism of PAHs.