Free Radical Assisted Photocatalytic Degradation of Antibiotics in aqueous medium: Kinetics, Transformation Products, and Toxicity Assessment

The degradation of an antibiotic drug was investigated by low-cost nanocomposite material. The visible light responsive non-metal activated carbon (AC) doped TiO 2 nanocomposite (AC/TiO 2 NC) photocatalyst with wide band gap energy was synthesized via the co-precipitation method with an equal mass ratio of AC and TiO 2 . 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 AC caused a notable reduction in the optical band gap of doped with TiO 2 . The composite AC/TiO 2 showed the maximum removal of 87.6% TCL 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 presence of UV light. The kinetic experimental data showed the best fitting for both pseudo-first-order (k a = 21.83 min − 1 ) and pseudo-second-order (0.23 g/g.min) models with a high accuracy based on R 2 values. Freundlich model showed a maximum adsorption capacity (q m ) of 94.87 (mg/g) for TCL drug removal on the heterogeneous surface with high accuracy (R 2  = 0.999) than the Langmuir model. Adsorption followed by degradation was shown at optimized pH while intraparticle diffusion phenomena acts as the rate-limiting step. Moreover, a proposed drug degradation mechanism based on the formation of HO. radical is suggested and LC-MS analysis identified fourteen intermediate products during TLC degradation. While the antibacterial activity test showed that the generated degradation products were less toxic compared to the TCL molecule.