Simultaneous monitoring of photocatalysis of three pharmaceuticals by immobilized TiO₂ nanoparticles: Chemometric assessment, intermediates identification and ecotoxicological evaluation

In this study, the photocatalytic degradation of a mixture of three pharmaceuticals, Metronidazole (MET), Atenolol (ATL) and Chlorpromazine (CPR), was quantified simultaneously during the UV/TiO₂ process. The investigated TiO₂ was Millennium PC-500 immobilized on ceramic plates by sol-gel based method. The partial least squares modeling was successfully applied for the multivariate calibration of the spectrophotometric data. The central composite design was applied to model and optimize the UV/TiO ₂ process. Predicted values of removal efficiency were found to be in good agreement with experimental values for MET, ATL and CPR (R2 = 0.947 and Adj-R² = 0.906, R² = 0.977 and Adj-R² = 0.960 and R² = 0.982 and Adj-R² = 0.969, respectively). The optimum initial concentration of pharmaceuticals, reaction time and UV light intensity was found to be 10 mg L^-1, 150 min and 38.45Wm ^-2, respectively. The main degradation intermediates of pharmaceuticals produced in this process were identified by GC-MS technique. The chronic ecotoxicity of pharmaceuticals was evaluated using aquatic species Spirodela polyrrhiza prior to and after photocatalysis. The TOC results (90% removal after 16 h) and ecotoxicological experiments revealed that the photocatalysis process could effectively mineralize and reduce the ecotoxicity of the pharmaceuticals from their aqueous solutions.