Enrichment and degradation of tetracycline using three-dimensional graphene/MnO2 composites

It is a great challenge to realize the effective removal and transform of emerging pharmaceuticals from aquatic environment. In this study, MnO2 was used as a catalyst to achieve the degradation of tetracycline (TC) in situ on the surface of three-dimensional graphene (3DG). The removal of TC were also evaluated at different temperature, pH and inorganic ions. Due to the synergistic effect of 3DG and MnO2, TC could be efficiently removed by 3DG/MnO2 composites. The removal data were fitted well with rate-retarded model, indicating that the adsorption of reaction products on the surface of 3DG/MnO2 composites could lead to saturation of surface and less reactive sites. Moreover, the reaction of TC with 3DG/MnO2 was endothermic, and reaction rate decreased with the increase of pH, due to the changes of properties of 3DG/MnO2 and TC. Inorganic ions could compete with TC for vacancy or the reactive sites on 3DG/MnO2 surface to inhibit the removal of TC. This work develops a potentially effective carbon material for simultaneous enrichment and degradation of organic pollutants and provides a new sustainable approach for wastewater treatment.