Kinetic and thermodynamic studies on the adsorption of tetracycline onto graphene

The graphene(GR) was prepared via a facial oxidation-reduction method,and its adsorption behavior with tetracycline(TC) was also studied.The characterization results,such as X-ray diffraction and transmission electron microscopy(TEM) observations,showed that the synthesised GR possessed laminated structure and high surface area.The effects of pH,adsorption time and temperature on the interaction between TC and GR were investigated by the equilibrium adsorption method.The results were fitted by the equation of adsorbent kinetics and isothermal curve.The optimal pH condition for the adsorption process ranged from 4.0 to 7.0.The adsorption reached at the balanced state in 20 minutes and the adsorption process could be well described by the pseudo second order model.The maximum adsorption capacity was respectively 172.1,278.2,467.6 mg/g at 293,303,313 K.The adsorption process was spontaneous and endothermic in nature,which could be described well by Freundlich isotherm.The electrostatic interaction,van der Waals forces and π-based interaction might be the adsorption mechanisms of TC adsorption on GR.