Iron (II) Activated Persulfate Oxidation of MGP Contaminated Soil

Abstract

The persulfate anion (S2O8 2−) is a strong oxidant with a redox potential of 2.01 V. However, when mixed with iron (II), it is capable of forming the sulfate radical (SO4 −.) that has an even higher redox potential (E o = 2.6 V). In these studies the sulfate radical was investigated to determine if it was a feasible oxidant for the destruction of BTEX and PAH compounds found in MGP contaminated soil. The sulfate radical was generated by either the sequential addition of iron (II) solutions or by a single addition of a citric acid chelated iron (II) solution. The sequentially added iron destroyed 86% of the total BTEX concentration and 56% of the total PAH concentration in the soil. The citric acid chelated iron destroyed 95% of the total BTEX concentration and 85% of the total PAH concentration. A second dose of persulfate and citric acid chelated iron (II) resulted in the destruction of 99% of the total BTEX concentration and 92% of the total PAH concentration. In both the sequential and chelated iron studies the lower molecular weight BTEX compounds were oxidized to a greater extent than the higher molecular weight BTEX compounds, whereas the oxidation of PAH compounds showed no preference to molecular weight.