Highly efficient removal of chlorotetracycline from aqueous solution using graphene oxide/TiO2 composite: Properties and mechanism

The extensive usage of chlorotetracycline (CTC) has caused the persistence of antibiotic residues in aquatic environments, resulting in serious threat to human health and ecosystems. In this study, graphene oxide/titanium dioxide (GO/TiO 2 ) nanocomposite was successfully synthesized via in situ hydrolysis of tetra- n -butyl titanate (Ti(BuO) 4 ) to TiO 2 particles on GO sheets and used as adsorbent for efficient adsorptive removal of CTC from aqueous solution. The prepared GO/TiO 2 was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transformed infrared (FT-IR), Raman spectroscopy and X-ray photoelectron (XPS). Adsorption kinetics, isotherms and thermodynamics were systematically investigated to evaluate the adsorption properties of GO/TiO 2 . Adsorption mechanism was further analyzed by FT-IR, UV–vis and XPS. The results indicated that adsorption kinetics closely followed the pseudo-second order model; the maximum adsorption capacity determined by Langmuir model was 261.10   mg   g −1 at 298   K and the thermodynamic studies revealed that the adsorption of CTC onto the GO/TiO 2 was a spontaneous and endothermic process. Moreover, the interactions between CTC and GO/TiO 2 were presumed to be ligand exchange between CTC and TiO 2 , while the π-π electron donor-acceptor interaction, hydrogen bond and cation-π bonding were constructed between CTC and GO. Finally, the prepared GO/TiO 2 was successfully applied for the efficient removal of CTC from Wu River water.