Ozone treatment of soil contaminated with aniline and trifluralin

Column studies were conducted to determine the ability of ozone to degrade aniline and trifluralin in soil. Ozone rapidly degraded aniline from soil under moist soil conditions, 5% (wt). Removal of 77–98% of [UL-14C]-aniline was observed from soil columns (15 ml, i.d.=2.5 cm), exposed to 0.6% O3 (wt) at 200 ml/min after 4 min. Initial ozonation products included nitrosobenzene and nitrobenzene, while further oxidation led to CO2. Ring-labeled-[UL-14C]-trifluralin removal rates were slower, requiring 30 min to achieve removals of 70–97%. Oxidation and cleavage of the N-propyl groups of trifluralin was observed, affording 2,6-dinitro-4-(trifluoromethyl)-aniline, 2,6-dinitro-N-propyl-4-(trifluoromethyl)-benzamine, and 2,6-dinitro-N-propyl-N-acetonyl-4-(trifluoromethyl)-benzamine. Base solutions revealed that trifluralin was similarly oxidized to CO2, where 72–83% of the activity recovered comprised 14CO2. Use of ozone-rich water improved contaminant removal in trifluralin-amended soil columns, but did not improve removal in aniline, pentachloroaniline, hexachlorobenzene amended soil columns, suggesting that ozonated water may improve contaminant removal for reactive contaminants of low solubility.