Photocatalytic Degradation of Methylisothiazolinone in Water by TiO2 and TiO2/Persulfate systems with Simulated Solar Radiation

Abstract

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 significantly 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.