Photocatalytic degradation of methylisothiazolinone in water by TiO2 and TiO2/persulfate systems with simulated solar radiation

The photocatalytic decomposition of methylisothiazolinone (MIT) in water was successfully attained with TiO2 and TiO2/persulfate systems under simulated solar irradiation. The TiO2 catalysts were synthesized by sol-gel process, controlling the hydrolysis rate of titanium n-butoxide by two procedures: external addition of water and in situ production of water via esterification between ethanol and a carboxylic acid. Crystalline structure, morphology and textural properties of materials were characterized by XRD, SEM and N2 adsorption-desorption isotherms. The photocatalytic activity of the obtained catalysts for MIT degradation was proved to be signifi-cantly dependent on both the procedure of water provision for the alkoxide hydrolysis and the calcination temperature. Adding persulfate (PS) to the system resulted in a great enhancement of the MIT degradation rate, which was kept in different water matrices due to a synergistic effect between the titania catalysts and PS activation. MIT transformation products (TPs) were identified by HPLC-HRMS and a mechanism for MIT degradation was proposed. Total Organic Carbon and toxicity measurements established the complete MIT mineralization and non-toxicity of the water solution after the photocatalytic treatment.