OZONATION OF VOCS IN THE PRESENCE OF HUMIC-ACID AND SOILS

The oxidation of several VOCs in the presence of humic acid and soil is described in this paper. It was found that while ozone does react appreciably with humic acid, as indicated by significant changes in the spectral characteristics of humic acid, the TOC levels in these solutions changed by only 3% or less. The oxidation of four olefinic VOCs occurred in solutions containing up to 120 mg/L humic acid, however, the extent to which each of the compounds reacted is very much compound specific. The effect of pH and ozone dosage on these reactions was considered. The effects of pH were weak for all compounds except trichloroethane. Ozone dosage had a significant effect on the extent to which each of the VOCs was oxidized, although no simple relationship between ozone dosage and the amount of VOC which reacted could be obtained. Complete oxidation of cis-dichloroethylene by ozone (22 mg/L) occurred in solutions containing 1.0 g of Eustis soil suspended in 10.0 mL water. However, only 40% oxidation of tetrachloroethylene was achieved using an ozone dosage of 17.3 mg/L when 1.0 g of Eustis soil was present. The results obtained in this study strongly suggest that the influence of free radicals, generated during the decomposition of ozone, on the oxidation of VOCs is significant. The work described here suggests that ozone may be applicable for the treatment of contaminated soils and waters containing high concentrations of naturally occuring organic matter.