title: Enhanced bioremediation of oil contaminated soil by graded modified Fenton oxidation.
abstract: Graded modified Fenton's (MF) oxidation is a strategy in which H2O2 is added intermittently to prevent a sharp temperature increase and undesired soil sterilization at soil circumneutral pH versus adding the same amount of H2O2 continuously. The primary objective of the present study was to investigate whether a mild MF pre-oxidation such as a stepwise addition of H2O2 can prevent sterilization and achieve a maximum degradation of tank oil in soil. Optimization experiments of graded MF oxidation were conducted using citric acid, oxalic acid and SOLV-X as iron chelators under different frequencies of H2O2 addition. The results indicated that the activity order of iron chelates decreased as: citric acid (51%) > SOLV-X (44%) > oxalic acid (9%), and citric acid was found to be an optimized iron chelating agent of graded MF oxidation. Three-time addition of H2O2 was found to be favorable and economical due to decreasing total petroleum hydrocarbon removal from three time addition (51%) to five time addition (59%). Biological experiments were conducted after graded MF oxidation of tank oil completed under optimum conditions mentioned above. After graded oxidation, substantially higher increase (31%) in microbial activity was observed with excessive H2O2 (1470 mmol/L, the mol ratio of H2O2:Fe2+ was 210:1) than that of non-oxidized soil. Removal efficiency of tank oil was up to 93% after four weeks. Especially, the oil fraction (C10-C40) became more biodagradable after graded MF oxidation than its absence. Therefore, graded MF oxidation is a mild pretreatment to achieve an effective bioremediation of oil contaminated soil.
authors.affiliation: School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China. xujinlan@xauat.edu.cn
authors.forename: Jinlan
authors.initials: J
authors.lastname: Xu
authors.forename: Lei
authors.initials: L
authors.lastname: Xin
authors.forename: Tinglin
authors.initials: T
authors.lastname: Huang
authors.forename: Kun
authors.initials: K
authors.lastname: Chang
mesh_terms: D001673:Biodegradation, Environmental; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000032:analysis / Q000737:chemistry; D010084:Oxidation-Reduction; D010578:Petroleum / Q000382:microbiology*; D012989:Soil Pollutants
chemical_list: C045076:Fenton's reagent; D010578:Petroleum; D012989:Soil Pollutants; D006861:Hydrogen Peroxide; D007501:Iron