Comparative Study of Different BC-nZVI/Oxidant Systems: Remediation of BaP and Cr(VI) in Contaminated Soils

Soil co-contamination by organic pollutants and toxic metals has become an increasingly prominent environmental concern worldwide, largely driven by intensive industrial and anthropogenic activities. In this study, BC-nZVI coupled with three oxidants—persulfate (PS), BS, and hydrogen peroxide (HP)—was evaluated for the simultaneous remediation of BaP and Cr(VI) co-contaminated soil. Among the tested systems, BC-nZVI/BS exhibited the best overall performance, achieving 77.7% BaP removal and 97.6% Cr(VI) reduction, followed by BC-nZVI/HP and BC-nZVI/PS. Among the three systems, the BC-nZVI/BS system maintained comparatively stable remediation performance over the tested pH range. Coexisting Cr(VI) exerted a pronounced synergistic effect on BaP degradation in the BC-nZVI/BS system, likely via promoting oxidant activation. Six classes of intermediates with simpler structures than BaP were tentatively identified, indicating the progressive transformation of BaP during the remediation process. Post-treatment characterization revealed the presence of Cr 2 O 3 , FeCr 2 O 4 , and Cr(OH) 3 , suggesting that Cr(VI) was predominantly removed through reductive precipitation to Cr(OH) 3 . Overall, the BC-nZVI/BS system showed promising potential for the remediation of BaP-Cr(VI) co-contaminated soils.