Enhanced adsorption of tetracycline antibiotics from pharmaceutical wastewater on expanded graphite composites modified by metal oxide

Tetracycline (TC), a major pollutant in water, has an adverse effect on ecosystem and human health. Thus, it is urgent to remove but still remains a challenging. In this work, a new adsorbent of MnO 2 decorated on sodium hypochlorite treated expanded graphite (MnO 2 /TEG) was developed by an in situ hydrothermal method, which exhibited a highly removal rate of 99.2% to pharmaceutical wastewater treated by flocculation. The structure and morphology of the adsorbent was studied by detailed physical characterization. Meanwhile, the main influencing factors on the adsorption behavior such as pH value, concentration, temperature of the solution, adsorption time, metal oxide species and MnO 2 loading amount were also investigated in detail. It was found that the electrostatic adsorption between Mn 4+ in MnO 2 /TEG and dimethylamino groups in TC molecules played an important role during the adsorption process. These excellent properties proved that the novel composite could be applied to remove TC residues in pharmaceutical wastewater.