PFAS as emerging pollutants in the environment: A challenge with FAU type and silver-FAU exchanged zeolites for their removal from water

The adsorption efficiency of Zeolites Y (FAU-type topology) with different silica/alumina ratio towards perfluorooctanoic acid (PFOA, C8HF15O2) and perfluorooctane sulfonate (PFOS, C8F17SO3H), was investigated by combining batch adsorption and synchrotron X-ray powder diffraction (XRPD) analyses. Adsorption isotherms show that the saturation capacity of Y390 as-synthesized and Ag-exchanged sample, was for PFOA was ~43% and ~62%, and for PFOS was ~17% and ~32% in weight respectively. XRPD Rietveld refinements provided the exact location of PFOA and PFOS in the zeolites network before and after functionalization with Ag. PFAS are located at the center of the supercage, H- bonded to both co-adsorbed water molecules and framework oxygen atoms. Y-PFOA/PFOS and AgY-PFOA/PFOS oligomers strongly interact with oxygen atoms of the zeolite framework, thus immobilizing the pollutants in the zeolite microporosity. These findings indicated that these materials can be successfully used for the decontamination of water from perfluoroalkyl chemicals. Additionally, introduction of Ag onto zeolites could confer combined antifouling and adsorption properties thus exhibiting improved performances compared to zeolite as single compounds thus working synergistically in removal of PFAS from water.