Synthesis of Fe-, Co-doped TiO2/vermiculite for enhanced antibiotic adsorption and photocatalytic degradation

Herein, Fe-, Co-doped TiO2 semiconductors dispersed on acid-modified vermiculite were successfully synthesized using sol-gel method. The photocatalytic activity and adsorption capacity of Fe-, Co-doped TiO2 catalysts were evaluated through the removal of ciprofloxacin antibiotic in water. Fe-, Co-doped TiO2/Vermiculite (Ver) were mesoporous materials with specific surface areas of 162.7 m2/g (Fe-doped TiO2), and 172.7 m2/g (Co-doped TiO2/Ver). The combination between Fe-, Co-doped TiO2 and Ver resulted in an improved visible light absorption, with band gap energy decreasing from 3.31 eV (TiO2), to 2.02 eV (Fe-doped TiO2), and 1.79 eV (Co-doped TiO2), enhancing the photocatalytic performance and absorption capacity. The Fe-, Co-doped TiO2/Ver achieved 96.1 % of ciprofloxacin (50 mg/L) removal by photocatalytic process. Anions inhibited photocatalytic activity with the following order Cl− > H2PO4− > I−, while HO• and h+ were primary reactive species generated. Adsorption process followed the Freundlich isotherm (R2 > 0.99) and pseudo-second-order kinetics (R2 > 0.98), suggesting the involvement of physico-chemical adsorption processes. The photodegradation process adhered to pseudo-first-order kinetics, with a maximum rate constant of 0.43 min−1. Co-, Fe-doped TiO2/Ver maintained good ciprofloxacin removal efficiencies after three reused cycles, demonstrating its high stability. This study presents a promising approach for removing antibiotic residues from water.