High adsorption behavior and photoregeneration of modified graphite oxide-titanium dioxide nanocomposites for tetracycline removal in water

To integratedly utilize adsorption technology and photocatalytic degradation for tetracycline (TTC) removal, a series of graphite oxide (GO)-titanium dioxide (TiO2) nanocomposites coupled with Sr(OH)2/SrCO3 were synthesized, of which GTiSr-81 (mass ratio = 8:1:1) exhibited potent adsorption and photocatalytic activities. Loose multilayer lamellar structure and macropore structure probably contribute to GTiSr-81?s high adsorption capacity; both Sr(OH)2/SrCO3 and GO improve the photocatalytic ability of TiO2. High adsorption (96.9 %) and very small desorption (<4.6 %) of TTC on GTiSr-81 were achieved. Pseudo-second-order kinetic could well describe the TTC adsorption process onto GTiSr-81, as well as Freundlich isotherm models, demonstrating a chemical adsorption mechanism and heterogeneous surface of GTiSr-81. Thermodynamic studies showed that TTC adsorption by GTiSr-81 was a spontaneous and endothermic process. Lower solution pH and ionic strength favored the adsorption of TTC onto GTiSr-81. The photocatalytic degradation study showed that GTiSr-81 had a strong photocatalytic degradation ability for TTC, with a degradation rate of 98.1 %. Antibacterial tests of the TTC solution suggested that the antibacterial activity was only caused by TTC and had no correlation with the degradation intermediates of TTC. After five adsorption?photoregeneration cycles, the adsorption efficiency of TTC on GTiSr-81 was still as high as 83.4 %, which proved that GTiSr-81 possessed potential and substantial reuse properties. ? 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.