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 N-2 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 (Y-1), CIP degradation (Y-2) and APAP degradation (Y-3). 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 Lh(-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 (Y-1 = 64.60%, Y-2 = 80.58% and Y-3 = 50.12%). Finally, the intermediate by-products of the drugs formed in the degradation process were identified using the GC-MS technique. (C) 2017 Elsevier Ltd. All rights reserved.