Enhanced degradation of petroleum hydrocarbons in soil by FeS@BC activated persulfate and its mechanism

Rapid degradation of petroleum hydrocarbons by chemical oxidation is currently facing lots of environmental concerns, and green activation methods are highly needed. This study investigated the degradation of total petroleum hydrocarbons (TPHs), polycyclic aromatic hydrocarbons (PAHs), and n-alkanes in soil by FeS@BC and FeS activated persulfate (PS). Various controlling factors including FeS to biochar (BC) mass ratio, PS dosage, FeS@BC dosage, and initial pH were examined. The optimal parameters were obtained by single-factor experiments. Under the optimal condition, the removal rates of TPHs, PAHs, and n-alkanes by a FeS@BC/PS system were 61.83 %, 78.17 %, and 91.56 %, respectively, which were much higher than those of a FeS/PS system (47.91 %, 51.20 %, and 79.31 %, respectively). Radical quenching experiment and Electron Paramagnetic Resonance (EPR) revealed that the dominant active substance is sulfate free radical (SO4 center dot-) produced by PS during activation. Based on the characterization and data analysis, a possible activation mechanism is proposed: the reduction of Fe2+/Fe3+ and the activation of BC as an electron transfer mediator promote the generation of SO4 center dot-. This study demonstrates that the FeS@BC/PS system has a promoting effect on the degradation of petroleum hydrocarbons in soil, which has great potential for remediation of petroleum-contaminated soil.

Automated summary

This study investigated the degradation of petroleum hydrocarbons in soil using FeS@BC and FeS activated persulfate (PS). The results showed that the FeS@BC/PS system had a higher removal rate for total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and n-alkanes compared to the FeS/PS system. Radical quenching experiment and Electron Paramagnetic Resonance revealed that the dominant active substance is sulfate free radical produced by PS during activation. The FeS@BC/PS system has great potential for the remediation of petroleum-contaminated soil.