Promoting targeted oxidation of medium- and long-chain alkanes in oil-contaminated soil by organic matter passivation

Abstract

In this study, soil organic matter (SOM) passivation was used to suppress SOM reactivity, reduce free-radical consumption, and achieve the efficient targeted oxidation of petroleum hydrocarbons. Passivation treatment significantly enhanced the oxidation efficiency, with total petroleum hydrocarbon (TPH) oxidation reaching 12036.24 mg/kg, a 1.33-fold increase compared to that of unpassivated soil. The oxidation levels of short-chain (C₁₁–C₁₇), medium-chain (C₁₈–C₂₄), and long-chain (C₂₅–C₃₀) alkanes were 3940.50, 5627.02, and 2468.71 mg/kg, respectively, showing 1.21-fold, 1.58-fold, and 1.98-fold improvements compared to those of unpassivated treatment. Three-dimensional excitation-emission matrix fluorescence spectroscopy indicated that passivation reduced both the SOM content and free-radical allocation rate by 28.05%, confirming reduced oxidant consumption. Fourier-transform infrared spectroscopy revealed a significant decrease in the absorbance of C–O–C, C=O, and O–H functional groups, which can contribute to improved oxidation efficiency. In addition, molecular analysis performed using the Multiwfn and VMD software indicated that passivation altered the electrostatic potential on the surface of organic matter molecules, reducing their reactivity with hydroxyl radicals and providing a theoretical basis for the passivation mechanism. In conclusion, the targeted-oxidation technology based on SOM passivation coupled with the Fenton reaction can enhance the remediation efficiency of petroleum-contaminated soil while reducing cleanup costs. Moreover, this technical approach provides critical support for the development of efficient remediation strategies for soils with complex contamination.

Graphical abstract

Keywords

Petroleum-contaminated soil / Efficient targeted oxidation / Multiwfn mechanism analysis / Passivation / Medium–long-chain petroleum

Highlight

	● Passivation raised soil TPHs oxidation to 12036.24 mg/kg, 1.33× pre-treatment.
	● After passivation, SOM’s consumption of •OH dropped to 26.44%.
	● Reduced C–O–C, C=O, and O–H absorbance is key to enhanced TPHs oxidation.
	● Al3+ masks SOM active sites, boosting TPHs oxidation efficiency.
	● Multiwfn analysis shows passivation lowers organic matter •OH reactivity.

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