Development of in-situ treatment processes for the sustainable remediation of PFAS-contaminated groundwater

In the field of environmental remediation, emerging contaminants pose a significant challenge due to their persistence, diverse chemical properties, and limited effectiveness of conventional treatment methods. Among these, per- and polyfluoroalkyl substances (PFAS) stand out as a particularly concerning class of synthetic, highly fluorinated organic compounds, widely used in industrial and consumer applications due to their thermal and chemical stability, hydrophobicity, and surfactant properties. However, their persistence in the environment, high mobility in water, and potential toxic effects—including endocrine disruption, carcinogenesis, and immunotoxicity—have raised global concerns. Regulatory agencies in the United States and Europe have imposed strict limits on PFAS concentrations in drinking water, increasing the urgency for effective remediation technologies. Conventional treatment methods, such as activated carbon adsorption, reverse osmosis, ion-exchange resins, and advanced oxidation processes, have demonstrated limitations, particularly in the removal of short-chain PFAS, which exhibit lower sorption affinity and higher mobility in water. In this research, biochar derived from the pyrolysis of pinewood was investigated as a low-cost, sustainable alternative for PFAS removal. Biochar was studied at different pyrolysis temperatures (850°C and 1000°C) and modified through functionalization with a quaternary ammonium surfactant (CTAB) to enhance adsorption capacity. The research focused on both long-chain (e.g., PFOA, PFOS) and short-to-intermediate-chain (e.g., PFBA, PFBS, PFHxA, PFHxS) PFAS to comprehensively evaluate adsorption performance. Adsorption experiments were conducted using a continuous flow-reactor system, a hybrid approach between batch and column studies, which provides a dynamic and reproducible assessment of adsorption efficiency under controlled conditions. This setup allowed for a direct comparison between biochar and conventional activated carbon, demonstrating the potential of biochar to overcome limitations observed in existing treatment technologies. The study also evaluated the effects of PFAS molecular structure, hydrophobicity, and functional group variations on adsorption efficiency, along with the impact of competitive interactions in mixed-PFAS solutions. The results highlight the potential use of biochar as a viable alternative for PFAS remediation, with implications for large-scale water treatment applications. By optimizing pyrolysis conditions and surface functionalization, biochar could serve as an environmentally friendly, cost-effective adsorbent capable of mitigating PFAS contamination in diverse water matrices.