The Photo-Fenton System

Abstract

The photo-Fenton system is an advanced oxidation technology for the oxidative degradation of recalcitrant organic contaminants in water, which is based on the photochemistry of iron complexes and the Fenton reaction. The efficiency of the photo-Fenton system in degrading water contaminants is mainly determined by the kinetics of the photochemical reactions of Fe(III) complexes. Under UV and visible light illumination, Fe(III) complexes undergo photochemical reduction to yield Fe(II) and a radical via ligand-to-metal charge transfer. The produced Fe(II) is used to generate reactive oxidants (mainly hydroxyl radical) responsible for the degradation of contaminants by reaction with hydrogen peroxide (i.e., the Fenton reaction). Fe(III) complexes exhibit different photochemical properties regarding light absorption and quantum yield, and their speciation is affected by different factors such as pH, temperature, and types of ligands. As a result, such factors affect the degradation of water contaminants by the photo-Fenton system. There have been numerous studies regarding application of the photo-Fenton system to water treatment. However, the practical use of the photo-Fenton system in the field is still limited due to several drawbacks. To improve the applicability of the photo-Fenton system, more progress must be made in both the fundamental and technical aspects of its use.