Tandem modified Fenton oxidation and bioremediation to degrade lubricant-contaminated soil

Abstract

Several remediation technologies were evaluated in this study to efficiently break down lubricant in contaminated soil, including chemical oxidation, bioremediation, and the combination of chemical oxidation and bioremediation. The chemical oxidation batch experiment results indicated that when soil pH was acidified to 3.0, traditional Fenton's oxidation most effectively removed lubricant in contaminated soil. However, this method may cause permanent damage to the ecosystem since it requires acidic soil conditions. Further experimentation showed that by adding citric acid to traditional Fenton's oxidation, this modified Fenton's process oxidized the lubricant even more efficiently, by forming an effective chelation and preventing the production of ferric oxide precipitates, all under neutral soil conditions. In the bioremediation tests, results showed that lubricant degradation efficiencies improved by adding peptone and glutamate salt, since they served as nutrients for the soil microbes. Overall, the combination of a 56 d biopile with ammonium chloride and monosodium glutamate, followed by a modified Fenton's oxidation, was found to be the optimal degradation approach in lubricant-contaminated soil, with a promising 99.2% removal efficiency for an initial concentration of 10,000 mg kg−1 of lubricant.