Effect of GO on oxytetracycline and Cu2+ co-adsorption in a yellow–brown soil

Abstract

Coexistence of nanoparticles with organic–inorganic pollutants in soil can lead to changes in their environmental behaviour. Here, graphene oxide (GO), oxytetracycline (OTC), and Cu²⁺ were selected as typical pollutants, to elucidate the regulatory mechanism of GO on the adsorption behaviours of OTC and Cu²⁺ in yellow–brown soil through characterisation techniques, including XPS and FT-IR. The findings indicated that coexistence with GO improved the adsorption capacity of OTC or Cu²⁺ in both single and co-adsorption systems. In the single system, GO incorporation augmented the π-π interaction of the OTC aromatic ring with the soil C=O groups and the hydrogen bonding of the OTC hydroxyl group with the Si-O groups; conversely, for Cu²⁺, GO intensified the electrostatic attraction of Cu²⁺ to the soil –OH and Si-O groups. In the OTC + Cu²⁺ system, Cu²⁺ facilitated OTC adsorption via a “bridging effect,” while GO incorporation augmented hydrogen bonding between OTC and soil –OH and complexation with Al/Fe-O, while Cu²⁺ inhibited the hydrogen bonding between OTC and soil Si-O. For Cu²⁺, the incorporation of GO intensified complexation between Cu²⁺ and soil C=O and electrostatic interactions with –OH during the co-adsorption of OTC and Cu²⁺. Additionally, OTC enhanced the electrostatic interaction between Cu²⁺ and soil.