Effects of copper and lead on the sorption and desorption behaviors of benzene onto humic acids and black carbons

View large Download slide View large Download slide Close modal Due to rapid urbanization and industrialization, combined pollution caused by BTEX (benzene, toluene, ethylbenzene, and xylene) and heavy metals has become ubiquitous in soils, which would pose serious health risks to humans. However, the effects of heavy metals on the sorption and desorption behaviors of BTEX have not been fully elucidated. In this study, the effects of Cu 2+ and Pb 2+ ions on the sorption and desorption of benzene onto humic acids and black carbons were investigated. The results showed that Cu 2+ and Pb 2+ ions significantly reduced the sorption capacity, slowed down the sorption rate, and made the desorption less hysteretic of benzene on both humic acids and black carbons. Furthermore, the inhibitory effects by Pb 2+ were significantly stronger than those of Cu 2+ . By combining the results of Fourier transform infrared spectroscopy and the site energy distribution model, it can be speculated that the hydration shells of Cu 2+ and Pb 2+ ions partially cover the surface of humic acids and black carbons, blocking their micropores and shielding sorption sites, consequently inhibiting the sorption of benzene. This study highlights that coexisting metal cations can significantly influence the fate of BTEX in soils. The coexistence of Cu 2+ and Pb 2+ ions inhibits benzene sorption and makes desorption less hysteretic onto humic acids (HAs) and black carbon (BCs). The hydration shells of Cu 2+ and Pb 2+ ions hinder the interaction between benzene molecules and the sorption sites. The adsorbed Cu 2+ and Pb 2+ ions block the pores of HAs and BCs and inhibit the pore-filling process of benzene.