Dual roles of CO2*- for degrading synthetic organic chemicals in the photo/ferrioxalate system.

In this study, the relative importance of the dual reaction pathways of CO2*- in the photo/ferrioxalate system, where it acts both as a reductant for reducing the ferric ion and as an agent for the formation of H(2)O(2), was investigated as a function of the concentrations of ferrioxalate and oxygen. We studied the two competitive reactions of CO2*- in the photo/ferrioxalate system, which depend on the relative concentrations of ferrioxalate to oxygen, with the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), which was used as a target pollutant. At high concentrations of ferrioxalate, almost all of the CO2*- reacted with ferrioxalate to reduce Fe(III) to Fe(II), whereas at low concentrations of ferrioxalate, a majority of the CO2*- contributed to the formation of H(2)O(2), as a result of its reaction with oxygen, which allows the Fenton reaction to occur without any external supply of H(2)O(2).