Peroxydisulfate oxidation of PCBs, chlorobenzenes, and MGP waste

The peroxydisulfate anion is a strong oxidant that can be activated to create the sulfate radical, a stronger oxidant with an oxidation potential of 2.6V. In these studies peroxydisulfate was evaluated as an oxidant for in situ chemical oxidation on a variety of aromatic contaminants. The peroxydisulfate was activated thermally and by reactions with iron (II) to oxidize polychlorinated biphenyls (PCBs), chlorobenzenes, and manufactured gas plant (MGP) waste. Thermally activated peroxydisulfate creates two sulfate radicals per peroxydisulfate anion, whereas iron (II) activated creates one sulfate radical and one sulfate anion.; A study with a 5,156 mug/L Aroclor 1242 solution treated with a 0.125 M sodium peroxydisulfate solution over 48 h showed no oxidation of PCBs at 20°C; however, 86% of the PCBs were oxidized at 40°C, and 98% were oxidized at 60°C. In the solutions where oxidation occurred, the less chlorinated PCB congeners degraded at a faster rate than the more chlorinated PCB congeners. A study on a soil with 44 mg/kg Aroclor 1242 and treated with a 0.20 M sodium peroxydisulfate solution over 96 h showed no oxidation of PCBs at 50°C, but 95% of the PCBs were oxidized at 60°C. Unlike the aqueous solutions, the PCB congeners in the soil samples were oxidized at the same rate.; Though the iron (II) activation of peroxydisulfate creates only one sulfate radical per peroxydisulfate anion, its advantage for in situ chemical oxidation application is that it proceeds at lower temperatures. However a disadvantage of this reaction is that the sulfate radical can react with surplus iron (II) instead of with the contaminant causing the reaction to stall. Therefore, sequential addition of small quantities of iron (II) was required to continuously reactivate the reaction.; The chelating agent citric acid was added to the iron (II) in an attempt to moderate the reaction and avoid the need for sequential addition of iron (II). The addition of citric acid dramatically increased the oxidation of all of the aromatic contaminants. A study on a soil with 620 mg/kg of chlorobenzene showed that all of the chlorobenzene was oxidized within 4 d. (Abstract shortened by UMI.)...