Comparing the efficiency of N-doped TiO₂ and commercial TiO₂ as photo catalysts for amoxicillin and ciprofloxacin photo-degradation under solar irradiation

Abstract

Advanced oxidation processes (AOPs) have gained traction as alternative solutions for eliminating pollutants from pharmaceutical wastewater for reuse. In this research, the performance of two photo-catalysts (Commercial TiO₂ and synthesis N-doped TiO₂) were compared in terms of the degradation of amoxicillin and ciprofloxacin from an aqueous solution using a photo-catalytic batch system under solar irradiation. The influence of five operating factors is: pH (5-11), H₂O₂ concentrations (200-600) mg/L, catalyst concentrations (25-100 mg/L), Antibiotic concentration (25-100) mg/L and reaction time (30-120 min), on the oxidation of the listed above pollutants were investigated using the central composite design (CCD) of response surface methodology (RSM). The catalyst of N-doping TiO₂ was synthesized by sol-gel method, using the urea (CH₄N₂O) as a nitrogen source. The resulting material was analyzed using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Additionally, it can be observed from the analysis of the characteristics of N-doped TiO₂ the homogenous dispersion of nitrogen molecules, small particle sizes, and energy-gap reduction, prompting a 6% increase in antibiotic degradation compared with Com. TiO₂. In the RSM analysis, the ideal conditions were found to be a pH of 5, H₂O₂ conc. of 400 mg/L, catalyst conc. of 50 mg, and antibiotics conc. of 25 mg/L for an antibiotics reduction rate of 89.31% (AMOX/Com. TiO₂/Solar), 90.2 (CFX/Com. TiO₂/Solar), 95.8% (AMOX/N-TiO₂/Solar) and 97.3% (CFX/N-TiO₂/Solar). Experimental results were in good agreement with predictions because the predicted R² matched well with the adjusted R².