Insights into interface mechanism of three typical antibiotics onto the graphene oxide/chitosan composite: Experimental and theoretical investigation

Abstract

The general application of antibiotics has brought a series of negative impacts on human health and the environment, which has aroused widespread public attention to their removal from aqueous systems. In this study, a chitosan (CS)-linked graphene oxide (GO) composite (GO-CS) was synthesized by a modified hummers/solvothermal method. It was separated from the mixed aqueous phase by low-speed centrifugation, thereby endowing the GO with high separation efficiency in water. The adsorption of tetracycline (TC), norfloxacin (NOR), and sulfadiazine (SDZ) by GO-CS were then studied by experimental techniques and theoretical calculations. In batch experiments at 298 K and optimal pH, the adsorption capacities of TC, NOR, and SDZ were 597.77, 388.99, and 136.37 mg/g, respectively, which were far better than those of pristine graphene oxide. The spectra results illustrated that the adsorption process was mainly contributed by the interactions between antibiotics and functional groups (carboxyl, hydroxyl, and amino groups) of GO-CS. Furthermore, density functional theory calculations showed that electrostatic interaction and hydrogen bonds were of vital importance for the uptake of the antibiotics; the former was extremely important for TC adsorption. This research provides theoretical references for the removal of antibiotics by graphene-based composite materials, thus offering their promising application in environmental remediation.