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

Abstract

• FeS@BC/PS system showed enhancement removal of petroleum hydrocarbons in soil. • Biochar prevented FeS aggregation and enhanced stability and removal efficiency. • Higher degradation rate was found for n-alkane compared to PAHs. • SO 4 Â · - is mainly responsible for petroleum hydrocarbons degradation. 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 ( S O 4 · - ) produced by PS during activation. Based on the characterization and data analysis, a possible activation mechanism is proposed: the reduction of Fe 2+ /Fe 3+ and the activation of BC as an electron transfer mediator promote the generation of S O 4 · - . 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.