Photodegradation of organic pollutants catalyzed by iron species under visible light irradiation

Abstract

The green oxidation technology is the most economically attractive and environmentally friendly oxidation technique in the treatment of organic pollutants. Photocatalytic degradation of organic pollutants by iron species is a desired green oxidation technique due to using hydrogen peroxide or ideally molecular oxygen as oxidant and water as solvent. However, the system has some disadvantages. The reaction has to be performed in acidic conditions in order to avoid Fe ion precipitation and iron sludge will be accumulated in the reaction. Moreover, the utilization of H₂O₂ means a high cost and risks in the storage and transportation and organic pollutants can not be completely mineralized. In this perspective, we report a systematic investigation of the improvement in the Fenton system for treatment of organic pollutants in water. Several strategies have been studied on the Fenton system for overcoming the above mentioned shortcomings and enhance the efficiency. For example, in order to extend the application of the Fenton system and perform it at neutral pH, iron complexes were used to replace the Fe²⁺/Fe³⁺. Moreover, iron complexes have a strong absorption in the visible region, which leads to decomposition of colorless organic pollutants under visible light irradiation. Iron complexes with special structures can activate molecular O₂ instead of H₂O₂ under mild conditions and the supported iron species maintains a high catalytic activity after repeated use and can be reused simply by filtration. Finally, prospects for further work required to be performed for its practical application is discussed.