(465f) Investigation of the Properties of MOFs for Adsorption of PFOS: Comparative Study of MIL 101 (Cr), MIL 101 (Cr)-AC, MIL 101 (Cr)-NH2 , & MIL-53(Al) BPDC with Activated Carbon

With the introduction of Per- and Polyfluoroalkyl Substances (PFAS) in the early 90s for various applications such as firefighting foams, non-stick cookware, and stain-resistant fabrics, there has been growing concern about its existence in water due to its harmful health effects on human and animals over time. The chemical and thermal stability of PFAS makes the breakdown difficult and PFAS environmental persistence makes the removal challenging. Among all techniques, the adsorption methodology has proved to be an efficient and economical way to the reduction of PFAS in water. Different adsorbent including classical activated carbon and new generation of adsorbent such as metal organic frameworks (MOFs) have been used for the removal of short-chain (C<6) and long-chain (C>7) PFAS. In this work, we performed perfluorooctane sulphonic acid (PFOS) adsorption at different pH (4-10) using different adsorbent including superfine Activated Carbon (SFAC) and various MOFs including MIL 101 (Cr), MIL 101 (Cr)-AC, MIL 101 (Cr)-NH₂, MIL-53(Al)-biphenyl-4,4’-dicarboxylic acid (Al-BPDC) and performed comparative analysis to investigate the effective parameters governing the PFOS adsorption with respect to MOF physicochemical properties and adsorption process operation conditions. The adsorbents characteristics such as morphology and size (using Scanning Electron Microscopy), crystallinity (using X-ray powder diffraction (XRD)), surface area and pore volume (using Brunauer–Emmett–Teller (BET)), surface charge, and functional groups (using Fourier-transform infrared spectroscopy (FTIR)) were analysis and were used for justification of adsorption performance and adsorption mechanism of each adsorbent. Based on performance, SFAC with around 93% PFOS removal (pH 4-6) showed supreme performance over other MOFs followed by Al-BPDC (86%) > MIL 101-AC (80%) > MIL 101 (65%) > MIL 101-NH₂ (20%). This behavior was explained based on the the presence of extensively large pore size in SFAC that would adsorb PFOS and hydrophobic interactions between SFAC and PFOS that made it an excellent source for PFOS adsorption. On the other hand, the interaction between MOFs and PFOS was mostly dominated by electrostatic interaction.