Effect of pyrophosphate on the dechlorination of tetrachloroethene by the Fenton reaction

The effectiveness of Fenton's reagent for the remediation of contaminated sandy soils is affected by the precipitation and sorption of Fe species in soil/water systems. We investigated the ability of pyrophosphate to maintain Fe in solution and thus enhance the dechlorination of tetrachloroethene (PCE) by the Fenton reaction. The results of the experiments showed that pyrophosphate could significantly increase the concentrations of Fe in aqueous solutions and enhance the dechlorination of PCE. The dechlorination rate of PCE in the presence of pyrophosphate was found to decrease with time, which was attributed to both the conversion of Fe(II) to Fe(III) and the decrease of aqueous Fe concentration. In comparison to organic chelating agents, pyrophosphate appeared to be more stable and thus catalyzed the dechlorination of PCE for a longer time. The extended dechlorination (>120 h) was attributed to the solubilization of Fe and the stabilization of H2O2 caused by the addition of pyrophosphate.