Performance of different oxidants in the presence of oxisol: Remediation of groundwater contaminated by gasoline/ethanol blend

Abstract In this study, Na 2 S 2 O 8 , K 2 S 2 O 8 , H 2 O 2 , and CaO 2 were tested for the remediation of groundwater contaminated by a gasoline/ethanol blend. In fuel spills, groundwater acquires high organic carbon content and a considerable amount of BTEX (benzene, toluene, ethylbenzene, xylene), and can be treated using In Situ Chemical Oxidation. Batch tests were conducted to select the best oxidant, which establishes, in the presence of oxisol (soil rich in iron), the proper conditions for the generation of radicals. The results indicated that the H 2 O 2 added was scavenged in the process and that CaO 2 , which releases H 2 O 2 slowly, achieved the best removal results. However, this compound has low solubility, forms precipitates and increases pH to 12. Therefore, Na 2 S 2 O 8 was selected instead, once it achieved good removal results, worked at low pH values and had slow kinetics, making it suitable for groundwater remediation. Tests revealed that the concentration of iron in a ferriferous oxisol promotes proper oxidant activation, achieving 99% BTEX removal and 45% COD removal. GC–MS analysis of the oxidized samples showed the formation of intermediates (e.g. acetic acid and 1-acetic anhydride with formic acid) indicating the pathway of remediation. Despite such remarkable results, soil control sample achieved considerable DOC removal, suggesting that the use of ISCO may speed the remediation process, but the soil itself has a mechanism to degrade this kind of organic matter.