Removal and stabilization of PFAS and As(V) co-contamination in soils by fluorine-functionalized biochar

The prevalent PFAS and heavy metals (such as arsenic) co-contaminated soils, resulting from industrial activities, present a considerable remediation challenge as conventional single-function materials are often ineffective. In this study, a fluorine-iron dual-functionalized biochar (FMBC) was prepared via a magnetite impregnation-fluorosilane grafting strategy, which integrates multiple binding modes: grafted perfluoroalkyl chains provide hydrophobic and F-F interaction zones for capturing PFAS tails; loaded Fe oxides offer positively charged electrostatic and coordinative sites to attract the anionic headgroups of PFAS, while simultaneously capturing As(V) through electrostatic attraction, coprecipitation, and complexation. 1:10FMBC exhibited a higher PFOS sorption (75.91 mg/g) compared to raw biochar (0.63 mg/g), achieving 99.9%, 95.3%, and 65.7% removal for PFOS, PFOA, and PFHxS, showing notable chemical stability, and maintaining efficient PFAS-As(V) removal across various water matrices. DFT calculations reveal that synergy of F-F interactions and electrostatic attraction governs the chain-length-dependent sorption of PFAS. In column tests with co-contaminated soils, 1.0 wt% 1:10FMBC was estimated to reduce the cumulative release of PFAS and As(V) over 20 years by 75.8-99.4% and 31.8-82.9%, suggesting competitive performance among reported amendments. This work validates that the design of multifunctional biochar is an effective pathway for stabilizing PFAS-As(V) co-contaminated soils, offering a technological option for field-scale remediation.