Non-covalent self-assembly synthesis of AQ2S@rGO nanocomposite for the degradation of sulfadiazine under solar irradiation: The indispensable effect of chloride

In this study, the effect of chloride ion (Cl−) on the degradation of sulfadiazine (SDZ) was evaluated using reduced graphene oxide (rGO) modified with sodium anthraquinone-2-sulfonate (AQ2S) photocatalyst (AQ2S@rGO), which was prepared in a one-pot hydrothermal synthesis. AQ2S molecules are small organic photoactive components, that are intercalated and immobilized on the rGO surface through noncovalent π-π stacking. Under solar light, SDZ effectively underwent 99 % photodegradation within 150 min in a Cl−-rich solution (0.5 mol/L). The AQ2S@rGO system exhibited an excellent photocatalytic removal ability for some typical contaminants. SDZ degradation was driven by 3AQ2S*. Superoxide radicals (O2−) and dichlorine radicals (Cl2−) were found to be the dominant reactive species, whereas OH and 1O2 have minor roles. Density functional theory (DFT) calculations confirmed the interactions between AQ2S and rGO, and the electronic structural characteristics between Cl− and AQ2S@rGO. The AQ2S@rGO composite has great potential for use in treating micropollutants under saline water conditions under solar irradiation.