Fast Direct Oxidation of All Alkanes in Soil by Hydrophilic Fe-SOM

Abstract

ABSTRACT Conventional Fenton chemical oxidation was more difficult to directly oxid all alkanes of long, mid and short-chain alkanes in oil-contaminated soil. To investigate the direct and fast oxidation mechanism of all alkanes in the soil by the fast oxidation group using two different soils for the direct oxidation experiments. The results showed that the hydrophilic Fe-SOM rich in hydrophilic groups could directly oxidize all alkanes in the soil with a high removal rate of total petroleum hydrocarbons (TPH) (59.0%–72.5%). Similarly, for the oxidation of long-chain alkanes (C23-C30), the fast oxidation group in which the hydrophilic Fe-SOM was located had higher removal rates (52%-64%). Regarding long chain oxidation per unit hydroxyl radicals (•OH) intensity, the fast oxidation group was significantly higher than the slow oxidation group (1.3–4.2 times). The results revealed a well-linear fit (r2 = 0.97, 0.81) for total iron and FeOOH with hydrophilic groups such as C=O and C-O-C in the fast oxidation group regarding content. Hydrophilic Fe-SOM enabled the rapid decomposition (51% − 88%) of H2O2 in the presence of hydrophilic promoters such as humic acid (49%−79%). The hydrophilic groups and hydrophilic promoters made the •OH generated by decomposition collide and react with pollutants rapidly to maximize the •OH in the liquid phase. The TPH removal efficiency per the unit intensity of •OH in the fast oxidation group was 3.74 times higher than in the slow oxidation group. The long-chain removal efficiency was 4.2 times higher than that in the slow oxidation group. The above results indirectly proved that the oxidation reaction in the fast oxidation group occurred at the petroleum pollutants and also demonstrated that the technology is an in situ oxidation technology. This technology can directly oxidize all petroleum hydrocarbons in the soil and has excellent engineering application value.