Effect of water matrix on photocatalytic degradation and general kinetic modeling

Abstract Photocatalysis employing TiO 2 nanoparticles was studied to assess the effect of aqueous matrix nature in the degradation of clofibric acid (CFA) under UV-A radiation. Aeroxide TiO 2 -P25 at 0.50 g/L was the most effective catalyst among those tested, with a CFA degradation of 98.5% after 15 min. The CFA photodegradation in environmental waters (tap, mineral, river and recycled wastewater) and in the presence of inorganic (NaCl, FeCl 3 , FeCl 2 , AlCl 3 , CaCl 2 , Al 2 (SO 4 ) 3 , Fe 2 (SO 4 ) 3 , Na 2 SO 4 , NaHCO 3 , and Na 2 CO 3 ) and organic compounds (humic acids, and a surfactant) commonly found in real waters was compared to that obtained in pure water. In general, the removal efficiency decreased with inorganic salts, especially with sulfates and carbonates (>70% deactivation), and also in environmental waters (>90%). A general kinetic model has been developed to describe the CFA photodegradation depending on the type and concentration of substances present in water. The first-order kinetic constants were estimated by defining a characteristic parameter for each ion species tested in the aqueous matrix. High correlation ( R 2  > 0.99 in most cases) was observed between experimental CFA concentrations and those predicted by the model.