Application of ball milling technology in removal of PFAS and ball milling modified materials: A review

Abstract

Perfluoroalkyl or polyfluoroalkyl substances (PFAS), as an emerging pollutant, are highly stable compounds due to the strong and highly polar carbon-fluorine bonds (C-F), which makes PFAS highly resistant to degradation, and further cause adverse effects on human and environmental health. It is imperative to develop a technology to efficiently remove PFAS from the environment media. The ball milling technology can produce high mechanochemical force, which had been developed to efficiently degrade or destruct PFAS. Adding the composite materials as a kind of supporter during the ball milling can improve the degradation percentage of PFAS. The significant destruction of PFOA and PFOS were observed during ball milling and the removal efficiency obtained >90 %. Additionally, the co-ball milling with some reagents like CaO, KOH and SiO₂ can effectively break the strong bond of C-F of PFAS in the soil, for example, removal efficiency of 6:2 fluorotelomer sulfonate (6:2FTS) reached 100 % when KOH co-milled with PFOA, PFOS and 6:2FTS in a planetary ball mill (PBM). Especially, the composited material of biochar doped with nitrogen, phosphorus, iron or other elements using ball milling enhanced adsorption capacity for dyes, heavy mental and antibiotics. N-rich biochar (BC) had the best adsorption capacity of 575.0 mg g^-1 methylene blue (MB) than that of ZnO or alkaline modified materials. In this paper, ball milling modified biochar materials and ball mill technology for remediation of soil and sediment contaminated with PFAS, comparisons of removal efficiency and ecological risks of materials were summarized. Till now, the destruction of PFAS in a variety of soils by ball milling has not been fully studied yet. In the future, some more efficient remediation technology of ball milling and sustainable materials need be further developed to treat the soil polluted with PFAS and ether substitutes for PFASs.