Time-Dependent Degradation and Kinetic Analysis of Total Petroleum Hydrocarbons in Crude Oil-Contaminated Soil Using Fenton’s Reagent Treatment

Abstract

Soil contamination by petroleum hydrocarbons poses significant environmental and health risks, necessitating efficient remediation strategies. This study evaluates the 60-day efficacy of Fenton’s reagent (H?O?/Fe²?) in degrading total petroleum hydrocarbons (TPH) in crude oil-contaminated soil, addressing the scarcity of long-term assessments. Soil samples spiked with Bonny Light crude oil (33,194 ± 2.90 mg/kg initial TPH) were treated with Fenton’s reagent at concentrations of 5–40 ppm. Degradation kinetics were analyzed using zero-, first-, second-, and two-compartment first-order models. Gas chromatography revealed that natural attenuation reduced TPH by 61% over 60 days, while Fenton’s reagent achieved 70–99.9% removal, depending on concentration and duration. Higher doses (30–40 ppm) yielded near-complete degradation (19.2–10.5 mg/kg residual TPH) by day 60, meeting regulatory thresholds. Kinetic modeling identified the two-compartment first-order model as optimal (R² = 0.987–0.999), reflecting biphasic degradation: rapid oxidation of labile hydrocarbons (e.g., alkanes) and slower breakdown of recalcitrant fractions (e.g., asphaltenes). The fast-degrading fraction’s half-life decreased from 8.5 days (untreated) to 3.2 days (40 ppm), while the slow fraction’s half-life dropped from 77.0 to 16.5 days, demonstrating Fenton’s enhanced efficacy for persistent compounds. A concentration-time synergy was observed: 30 ppm balanced efficiency and cost, achieving 99.8% removal, while lower doses (5–10 ppm) required extended timelines. These findings highlight Fenton’s reagent as a robust solution for rapid TPH remediation, with practical implications for tailoring treatments to site-specific needs. The study advances understanding of long-term degradation dynamics and provides a kinetic framework for optimizing petroleum-contaminated soil remediation.

Introduction

Soil contamination by petroleum hydrocarbons, especially total petroleum hydrocarbons (TPHs), poses a significant environmental threat due to their toxicity, persistence, and negative impact on soil health and ecosystems. Conventional remediation techniques like bioremediation and excavation have limitations such as long treatment times, high costs, or soil damage. Advanced oxidation processes (AOPs), particularly Fenton’s reagent (a mix of hydrogen peroxide and iron catalysts), have emerged as effective alternatives due to their ability to rapidly degrade complex hydrocarbons via hydroxyl radicals.

This study investigates the 60-day efficacy of Fenton’s reagent at various concentrations (5–40 ppm) on crude oil-contaminated soil collected from Nigeria. Natural attenuation reduced TPH levels by about 61% over 60 days, while Fenton’s reagent treatments achieved up to 99.9% TPH removal, with degradation rates increasing alongside reagent concentration. The degradation followed a biphasic pattern: rapid removal of labile hydrocarbons early on, followed by slower breakdown of recalcitrant compounds.

Kinetic modeling showed the degradation process fits well with first-order and two-compartment models, helping optimize treatment protocols. Despite promising results, challenges such as soil acidification at low pH and potential ecological impacts from residual reagents remain. The study highlights the need for balancing efficient contaminant removal with soil ecosystem preservation, recommending further long-term evaluations.

Conclusion

Both natural attenuation and Fenton-driven oxidation effectively reduce TPHs in contaminated matrices. The latter method, particularly at 30–40 ppm, offers a robust solution for rapid remediation. This has significant implications for restoration of oil-contaminated sites to near-pristine conditions, which is often a goal for remediation projects in sensitive ecosystems. Time and Fenton’s reagent concentration synergistically govern TPH degradation. Higher concentrations (30–40 ppm) achieve rapid remediation (1–14 days), ideal for urgent scenarios, while lower doses (5–10 ppm) coupled with extended treatment (30–60 days) offer cost-effective solutions for long-term projects. The comprehensive kinetic analysis through multiple models reveals that TPH degradation in crude oil-contaminated soil follows a complex, biphasic pattern that is best described by the two-compartment first-order model. Fenton\'s reagent significantly enhances degradation rates for both readily degradable and recalcitrant fractions, with a more pronounced effect on the latter. These findings have important implications for remediation strategy development, suggesting that chemical oxidation approaches like Fenton treatment can substantially accelerate the cleanup of petroleum-contaminated soils, particularly for addressing persistent hydrocarbon fractions that typically limit remediation timeframes. Future work should explore the effects of soil mineralogy and organic carbon content on rate constants to refine predictive models for diverse field conditions. Field applications must balance these factors against site-specific constraints, such as soil type and contaminant profile, to optimize remediation outcomes.

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Copyright

Copyright © 2025 Kerian K. Dimgba, Babatunde T. Ogunyemi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.