Preparation and selection of low-cost biomaterials for the quaternary treatment of wastewater effluent for PFAS removal

Per- and polyfluoroalkyl substances (PFAS) are a class of contaminants of emerging concern (CECs) that have attracted great attention in recent years because of their potential risks to human health, ecosystems, wildlife, and the environment. They are known for their high persistence and pass through conventional wastewater treatment processes, contaminating water bodies and soil. In this study, sixteen activated carbons prepared from different biomass residues were evaluated for PFAS removal from synthetic water and real wastewater effluent and compared with the commercial activated carbon NORIT. The adsorption performance of the three selected PFAS (PFOA, PFPeA, and PFBS), which are the most frequently detected in the aquatic environment, was evaluated. Then, the most effective adsorbent was identified and selected. The biomaterial JM-K2CO3 (prepared from locally sourced saltmarsh plant Juncus maritimus) demonstrated the highest adsorption efficiency of these PFAS in synthetic matrices and real wastewater effluent. Contrary to expectations, the presence of impurities and coexisting pollutants in real wastewater matrices did not adversely affect adsorption performance. Instead, enhanced removal efficiencies were achieved compared with those obtained in the synthetic Milli-Q water matrix. In addition, a positive synergetic effect of the three PFAS mixture was observed compared to individual removal. Finally, a kinetic and isothermal study of JM-K2CO3 was performed. The equilibrium was reached after 20 hours and proved to be very promising for PFAS removal, especially for long-chain PFAS such as PFOA. Nevertheless, it exhibited consistently high performance towards short-chain PFAS, highlighting its potential for use in final wastewater polishing stages and for integration with other advanced treatment technologies.