In situ iron activated persulfate oxidative fluid sparging treatment of TCE contamination--a proof of concept study.
In situ chemical oxidation (ISCO) is considered a reliable technology to treat groundwater contaminated with high concentrations of organic contaminants. An ISCO oxidant, persulfate anion (S(2)O(8)(2-)) can be activated by ferrous ion (Fe(2+)) to generate sulfate radicals (E(o)=2.6 V), which are capable of destroying trichloroethylene (TCE). The property of polarity inhibits S(2)O(8)(2-) or sulfate radical (SO(4)(-)) from effectively oxidizing separate phase TCE, a dense non-aqueous phase liquid (DNAPL). Thus the oxidation primarily takes place in the aqueous phase where TCE is dissolved. A bench column study was conducted to demonstrate a conceptual remediation method by flushing either S(2)O(8)(2-) or Fe(2+) through a soil column, where the TCE DNAPL was present, and passing the dissolved mixture through either a Fe(2+) or S(2)O(8)(2-) fluid sparging curtain. Also, the effect of a solubility enhancing chemical, hydroxypropyl-beta-cyclodextrin (HPCD), was tested to evaluate its ability to increase the aqueous TCE concentration. Both flushing arrangements may result in similar TCE degradation efficiencies of 35% to 42% estimated by the ratio of TCE degraded/(TCE degraded+TCE remained in effluent) and degradation byproduct chloride generation rates of 4.9 to 7.6 mg Cl(-) per soil column pore volume. The addition of HPCD did greatly increase the aqueous TCE concentration. However, the TCE degradation efficiency decreased because the TCE degradation was a lower percentage of the relatively greater amount of dissolved TCE by HPCD. This conceptual treatment may serve as a reference for potential on-site application.
Liang
Chenju
C
Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Rd., Taichung City 402, Taiwan. cliang@dragon.nchu.edu.tw
Lee
I-Ling
IL
D002712:Chlorides / Q000737:chemistry; D004867:Equipment Design; D005609:Free Radicals; D007501:Iron / Q000737:chemistry; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D013431:Sulfates / Q000737:chemistry*; D013997:Time Factors; D014241:Trichloroethylene / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification; D047392:beta-Cyclodextrins / Q000737:chemistry
D002712:Chlorides; D005609:Free Radicals; D013431:Sulfates; D014874:Water Pollutants, Chemical; D047392:beta-Cyclodextrins; C069025:sulfate radical; D014241:Trichloroethylene; D007501:Iron; D010100:Oxygen