Reactive oxygen species aided photocatalytic degradation of tetracycline using non-metal activated carbon doped TiO2 nanocomposite under UV-light irradiation

Abstract

The degradation of an antibiotic drug was investigated by low-cost nanocomposite material. The visible light responsive non-metal activated carbon doped TiO2 nanocomposite photocatalyst with wide band gap energy was synthesized via the co-precipitation method with an equal mass ratio of activated carbon and TiO2. Under optimal conditions, the photocatalytic experiment was carried out in a batch reactor in the presence of irradiation of 15W UV light. A significant effect of carbon caused a notable reduction in the optical band gap of doped with TiO2. The composite showed the maximum removal of 87.6% tetracycline drug in 45 min. The optimal catalyst dose and drug concentration were found to be 1.25 g and 100 mg/L, respectively, but the optimal reaction time, 45 min, and pH = 6.5 are very significant in the presence of UV light. The kinetic experimental data showed the best fitting for both pseudo-first-order (ka = 21.83 min−1) and pseudo-second-order (0.23 g/g min) models with a high accuracy based on R2 values. Freundlich model showed a maximum adsorption capacity (qm) of 94.87 (mg/g) for tetracycline drug removal on the heterogeneous surface with higher accuracy (R2 = 0.999) than the Langmuir model. Adsorption followed by degradation was shown at optimized pH, while intraparticle diffusion phenomena act as the rate-limiting step. Moreover, a proposed drug degradation mechanism based on the formation of hydroxyl free radicals is suggested, and LC–MS analysis identified fourteen intermediate products during drug degradation. At the same time, the antibacterial activity test showed that the generated degradation products were less toxic compared to the tetracycline molecule.