Oriented oxidation of all alkanes by iron inactivation of hydrophilic functional groups in soil organic matter

Abstract

While extensive studies concentrated on catalyst modification in Fenton technology, few focused on functional groups of soil organic matter inactivation by iron in soil remediation. This study aimed to investigate the mechanism of oriented oxidation of total petroleum hydrocarbons (TPH) by regulating the hydrophilic functional groups of soil organic matter (SOM). The oriented oxidation experiment was conducted using petroleum hydrocarbon contaminated soil by stepwise addition of Fe ions and H2O2, with the initial TPH of 21068 mg/kg and SOM of 54000 mg/kg. The results revealed that the oxidation of TPH in the inactive Fe-SOM group was 1.9 times higher than that in the active Fe-SOM group (4059 mg/kg versus 2187 mg/kg). Conversely, the oxidation of SOM decreased by a factor of 2.4-fold in the active Fe-SOM group (7532 mg/kg versus 3153 mg/kg). Moreover, the oriented oxidation of all alkanes such as short, medium, and long-alkanes (C13-C17: 409.07 mg/kg, C18-C24: 402.17 mg/kg, C25-C30: 400.09 mg/kg) was considerable compared to active Fe-SOM group. Furthermore, based on the characterization of FT-IR, XPS and 3DEEM, the inactivation of SOM was attributed to the formation of FeOOH, Fe-C-O, Fe-N by the combination of Fe and hydrophilic functional groups. Additionally, the possible oxidation pathway was proposed by gas chromatography. The relative reaction coefficient of hydroxyl radicals (•OH) contributes to improving the oriented oxidation of all alkanes by optimizing TPH allocation after SOM inactivation. This study enriches our understanding of oriented oxidation of all alkanes in petroleum-contaminated soil.