UV–Visible Light Driven Photocatalytic Degradation of Ciprofloxacin by N,S Co-doped TiO2: The Effect of Operational Parameters

Abstract

Photocatalytic degradation using TiO2 is one of the most effective techniques for treating residual emerging compounds present in water. However, practical applications are limited since it only absorbs ultraviolet irradiation. Nitrogen and sulfur (N, S) co-doped TiO2 nanomaterials (N,S-TiO2) were prepared by a controlled sol–gel method; the characterization and photocatalytic activity have been studied for the removal of ciprofloxacin antibiotic under UV–Visible light. The interstitial doping of nitrogen and sulfur substitute oxygen and titanium into the TiO2 lattice, which increases the valence band and decreases the conduction band, respectively. The lowest value band-gap of 2.5 eV and the crystallite size of 5.13 nm compared to other available synthesis methods was observed on N,S-TiO2 which allowed to broaden the light absorption to the visible region. The low level electron and hole recombination was related by the N, S doping. The optimal ciprofloxacin removal was obtained at pH 5.5, a dosage of 0.05 g, initial concentration of 30 mg L−1 with a removal efficiency of 78.7%. A comparison of the effectiveness of antibiotic treatment of N,S-TiO2 with synthetic TiO2 and commercial TiO2 was also made, taking the potential for regeneration into account. The photocatalytic degradation of ciprofloxacin catalyzed by N,S-TiO2 was described by pseudo-first-order kinetics.