Ultrasonic assisted photocatalytic process for degradation of ciprofloxacin using TiO₂-Pd nanocomposite immobilized on pumice stone

Herein, Pumice (PM)-TiO₂-Pd nanocomposite as an efficient catalyst was prepared by modified sol-gel method and used for sonophotocatalytic removal of ciprofloxacin (CIP). Various analyses were used to investigate the properties of the catalysts. Based on the SEM results, the TiO₂ and Pd nanoparticles on the PM surface were immobilized regularly without aggregation. Also, the crystalline structure and functional groups of PM-TiO₂-Pd nanocomposite were identified successfully by XRD and FTIR analyses. The bandgap energy of 2.52, 3.17, and 3.29 eV were calculated for PM-TiO₂-Pd, PM-TiO₂, and PM indicating higher sonophotocatalytic activity of PM-TiO₂-Pd nanocomposite. 79.44 % of CIP was removed within 120 min of treatment time using in the optimum condition ([PM-TiO₂-Pd] = 0.5 g/L, [CIP]₀ = 20 mg/L and pH = 6). By adding radical scavengers like EDTA, CrO₃, formic acid, and enhancers like K₂S₂O₈ and H₂O₂ the degradation efficiency was as follows respectively: 37.72, 31.71, 28.29, 88.78, and 72.43%. The reusability and stability of the composite after four consecutive runs was decreased only 9.44%. Also, 8 intermediate byproducts generated under sonophotocatalytic degradation of CIP by PM-TiO₂-Pd nanocomposite were identified.