Adsorption is regarded as an efficient and simple operative technique for mitigation of per- and polyfluoroalkyl substances (PFASs). Among various adsorbent materials, biochar has attracted comprehensive attention because of its superior performance, low cost, and production from a variety of biomass and solid wastes. However, further improvement of biochar for adsorption of PFAS needs to be investigated for its practical application along with understanding of the underlying mechanisms. In this study, FeCl3 was applied for activating the dairy manure and Bermuda grass-derived biochars to increase adsorption of e perfluorooctanoic acid (PFOA) in DI water and real wastewater. Interestingly, FeCl3 -driven activation decreased the surface area of both biochars while increasing the adsorption of PFOA, alluding FeCl3 activation introduced extra adsorptive sites. The detailed analysis of biochar properties indicated that the enhancement would be mainly due to the surface complexation of PFOA-Fe-CO groups on on Fe@MBC surface. The adsorption was facilitated at lower pH, alluding to a dominant role of electrostatic attraction. Furthermore, adsorption isotherm, kinetics and model-fittings indicated the adsorption was mainly driven by chemical adsorption on a heterogeneous surface, which matches our previous deduction for the mechanisms. Efficient adsorptive removal of PFOA was achieved at low concentration in both RO and wastewater effluent. Thermal and alkaline desorption could regenerate Fe@MBC effectively indicating its promising reusability. Overall, this study sheds light on the elimination of PFAS pollution by iron- engineered biochar and the underlying mechanisms associated with adsorption of PFAS.

Novel engineered biochar for removal of perfluorooctanoic acid in water: Adsorption, regeneration, and mechanisms

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