Mechanistic insight into cost-effective dedicated oxidation of alkanes by inactivating soil organic matter with FeOOH formed in situ

Abstract

Modified Fenton technique has been widely used to remediate soils contaminated with crude oil but significantly limited to soil organic matter (SOM) consuming oxidants. In this study, soils with developed SOM inactivation by FeOOH formed in situ were created and spiked with crude oil (total petroleum hydrocarbons (TPH): 19453 mg/kg), then treated by modified Fenton reagents. The reaction activity of hydroxyl radicals (•OH) relative to TPH (K) notably increased to 0.65 when the degree of developed inactivation of the SOM (β) was 100% (DIS-100), which was 1.45, 2.03 and 2.83-fold than that of DIS-50, DIS-15 and control (CK), respectively. Meanwhile, the higher the K, the more •OH transferred, which realized the efficient oriented oxidation of TPH. Moreover, improving the transfer of •OH from SOM to TPH was more important than increasing •OH production in soil remediation. With the β increasing to 100%, the ratio of invalid H2O2 decomposition to produce O2 decreased to 22%, equal to 25% reduction compared to CK. Therefore, when β was 100%, the utilization efficiency of H2O2 was improved to 1.48 mg/mmol, which was approximately 1.39, 3.35 and 5.43-fold higher than the efficiency got by DIS-50, DIS-15 and CK, respectively, achieving the cost-effective dedicated oxidation of TPH. In addition, the FeOOH cross-linked with SOM via Fe–O–C and Fe–N bonds to develop inactivation of SOM. In general, this study highlighted a new insight into the effect of developed inactivation of SOM on soil remediation.