Degradation of mixture of three pharmaceuticals by photocatalytic ozonation in the presence of TiO₂/montmorillonite nanocomposite: Simultaneous determination and intermediates identification

This study addressed the simultaneous degradation of mixture of three pharmaceuticals including metronidazole (MET), ciprofloxacin (CIP) and acetaminophen (APAP) through the photocatalytic ozonation system. TiO₂ nanoparticles were immobilized onto montmorillonite (MMT) support irradiated by UVA light in the presence of ozone. The samples were characterized by XRF, SEM, TEM, PL and N₂ adsorption-desorption analysis. A rapid and sensitive chemometrics technique was then developed for the simultaneous determination of the three pharmaceuticals in their mixtures during the photocatalytic ozonation process. A UV-vis spectrophotometer was used for recording the absorption of the pharmaceuticals. The concentration of these pharmaceuticals was successfully determined using a PLS method, despite the severe overlap of their spectra. A central composite design (CCD) was utilized to analyze, model and optimize the effect of each operational parameter on multiple responses including MET degradation (Y₁), CIP degradation (Y₂) and APAP degradation (Y₃). A multi response optimization approach based on a global desirability function (DF) of the factors was employed to simultaneously maximize the response factors. 25 mg L^-1 MET, 5 mg L^-1 CIP, 5 mg L^-1 APAP, 10 L h^-1 ozone flow rate and a 15 min of reaction time were found to be the ideal conditions at which the degradation of these pharmaceuticals could be simultaneously maximized (Y₁ = 64.60%, Y₂ = 80.58% and Y₃ = 50.12%). Finally, the intermediate by-products of the drugs formed in the degradation process were identified using the GC-MS technique.