Iron bound to soil organic matter catalyzes H2O2 to oxidize crude oil in soil

Under the action of hydrogen peroxide, soil organic matter (SOM) can transform dissolved iron (Fe2+) into the solid phase. Solid iron is bound to SOM (Fe-SOM), and two components are included: iron oxides bound to SOM (Fe-SOM oxides) and organic iron bound to SOM (organic Fe-SOM). In oil-contaminated soil samples with Fe-SOM, total petroleum hydrocarbon (TPH) was degraded by 67%; however, in oil-contaminated soil samples without Fe-SOM, the degradation of TPH was only 6%. In oil-contaminated soil samples with Fe-SOM, 73-86% of the primary alkanes (C14-C22 composed 67.5% of TPH) were removed, whereas only 45-65% of the C12-C13 and C22-C30 alkanes were removed. The 11 types of alkanes (C12-C13 and C22-C30) accounted for only 32.5% of TPH. Obviously, the degradation of TPH by Fe-SOM is independent of its hydrophobicity in the solid phase. The results also demonstrated that at a higher content of Fe-SOM, more hydroxyl radical (OH) was produced in the solid phase and more TPH was degraded. A large number of OH are generated near iron-SOM-oil interface.