Novel iron bound to soil organic matter catalyzes H2O2 to oxidize long-chain alkanes effectively in soil

In order to explore the removal mechanism of long-chain alkanes in the Fenton system with iron bound to soil organic matter (Fe-SOM), this study carried out 16 groups of experiments to compare the oxidation efficiency of the long-chain alkanes in the Fenton system with Fe-SOM and with typical Fe (Fe unbound to SOM) (total petroleum hydrocarbon (TPH) concentration was 9068 mg/kg). The results showed that the long-chain alkanes removal (C21-C30) in the Fenton system with Fe-SOM was up to 361-380 mg/kg (73%-77%), which was 1.6 times higher than that achieved in the Fenton system with typical Fe. The highest removal efficiency of the long-chain alkanes was for C27, i.e., up to 77%, which indicated that the long-chain alkanes in soil could be removed with a high efficiency in the Fenton system with Fe-SOM. Compared with Fenton system with typical Fe, Fenton system with Fe-SOM can achieve a higher removal efficiency of the long-chain alkanes and a lower residual concentration of long-chain alkanes in aqueous phase. In this system, the H2O2 decomposition is rapid, and the existence of the hydroxyl radicals (OH) is short. The results indicated that the long-chain alkanes oxidation in Fe-SOM system is different from the indirect oxidation in a typical Fe system. This non-indirect oxidation with Fe-SOM was not limited by the short existence of the OH, and these were the reasons for highly efficient oxidation of the sorbed long-chain alkanes in soil.