The residual tetracycline in pharmaceutical wastewater was effectively removed by using MnO2/graphene nanocomposite.

The object of this study was to remove the tetracycline (TC) residue in pharmaceutical wastewater after flocculation treatment. MnO2/graphene nanocomposite was synthesized by an in situ hydrothermal method and its TC removal rate was up to 99.4%. This nanocomposite had excellent water solubility. More importantly, the introduction of MnO2 nanorods allowed the avoidance of excessive stacking of treated graphene sheets during the adsorption process, which made the TC molecules to have more opportunities to make contact with the adsorbents. In order to eliminate the interference factors, the adsorption isotherm, kinetics, thermodynamics and mechanism were all studied in TC aqueous solution. The influence of solution pH, contact time, MnO2 loading amount, temperature and solution concentration on the adsorption process were also assessed. The main adsorption mechanism contributed to the complexation of Mn(IV) and π-π interactions of the benzene ring structure on treated graphene sheets with TC molecules.