Ethanol washing of PAH-contaminated soil and Fenton oxidation of washing solution

Abstract

As a means to remediate soil contaminated by polycyclic aromatic hydrocarbons, we investigated a combined process involving ethanol washing followed by a Fenton oxidation reaction. Artificial loamy soil was contaminated with various representative polycyclic aromatic hydrocarbons (i.e., fluorene, anthracene, pyrene, benzo(b)fluoranthene, or benzo(a)pyrene) at concentrations ten times higher than regulatory soil standards of The Netherlands or Canada, and then washed four times in ethanol, which reduced the concentration of polycyclic aromatic hydrocarbon contamination to below the regulatory standard. Fenton oxidation of ethanol solutions containing anthracene, benzo(a)pyrene, pyrene, acenaphthylene, acenaphthene, benz(a)anthracene, benzo(j)fluoranthene, or indeno(1,2,3-cd)pyrene showed a removal efficiency of 73.3%–99.0%; by contrast, solutions containing naphthalene, fluorene, fluoranthene, phenanthrene, or benzo(b)fluoranthene showed a removal efficiency of 9.6%–27.6%. Since each of the nonremediated polycyclic aromatic hydrocarbons, excluding benzo(b)fluoranthene, are easily biodegradable, these results indicate that the proposed treatment can be successfully applied to polycyclic aromatic hydrocarbon-contaminated soil that does not contain high concentrations of benzo(b)fluoranthene. The main reaction products resulting from Fenton oxidation of ethanol solutions containing anthracene or benz(a)anthracene were anthraquinon or benz(a)anthracene-7,12-dione, respectively; while 1,8-naphthalic anhydride was produced by solutions of acenaphthylene and acenaphthene, and 9-fluorenone by a fluorene solution.