Efficient oriented interfacial oxidation of petroleum hydrocarbons by functionalized Fe/N co-doped biochar-mediated heterogeneous Fenton for heavily contaminated soil remediation

Abstract

In this study, a novel alkylbenzenized Fe/N co-doped biochar (ABD-Fe/N@BC) catalyst was successfully fabricated by sequential pyrolysis and hydrothermal methods. Compared with traditional heterogeneous Fenton catalysts, this catalyst presented a higher adsorptive and catalytic activity to alkanes (11689 mg/kg) and polycyclic aromatic hydrocarbons (PAHs: 8554 mg/kg) in two soil with different contents of soil organic matter (SOM) (S1:10.38%; S2: 4.14%). Therefore, macro-alkanes and PAHs could be simultaneously adsorbed on ABD-Fe/N@BC surface through hydrophobic and π-π interactions to form a highly efficient oriented interfacial oxidation system. As a result, the ABD-Fe/N@BC/H2O2 system exhibited the most effectiveness for total petroleum hydrocarbons (TPHs) removal with 18505.74 and 19610.55 mg/kg oxidation amounts in S1 and S2, equal to 91.42 and 96.88% oxidation efficiencies, respectively. Thus, the “adsorption - oxidation” mode contributed to settling the inhibitory effect of SOM on TPHs oxidation. By contrast, only 35.39 and 46.86% TPHs oxidation efficiencies were reached in the EDTA-Fe2+/H2O2 system, while the SOM oxidation efficiencies were up to 50.11 and 69.43% in S1 and S2, respectively, which was around 3.4-fold than that of ABD-Fe/N@BC/H2O2 system. Furthermore, compared to EDTA-Fe2+/H2O2 system, the ABD-Fe/N@BC/H2O2 system characterized stronger anti-interference ability to other coexisting substances. Additionally, the •OH formed on the surface of ABD-Fe/N@BC by activating H2O2 predominantly induced the oxidation of alkanes and PAHs. Besides, O2•− was another critical reactive oxygen species responsible for PAHs oxidation. This study provided a promising novel heterogeneous Fenton catalyst to efficiently remediate heavily multicomponent petroleum hydrocarbons contaminated soil, especially rich in SOM.