The usage of Metal Organic Frameworks for the removal of PFAS from water

Abstract

This project encompases the green synthesis of two Metal Organic Frameworks (MOFs), along with an evaluation of their efficacy to remove PFAS from water. The included MOFs are UiO-66, synthesized in propylene carbonate (PC), and MOF-808, synthesized in water, alongwithperflourooctanoic acid(PFOA),andtriflouroaceticacid(TFA)asthechosenPFAS substances. To enable this, multiple methods of analysis and characterization are used. With the premiss of previously published papers, solvothermal synthetic methods are deve loped. PXRD, TGA and FTIR are utilized as characterization methods along with gas sorp tion, where the BET-theory was used to estimate the apparent surface area of the MOFs. The data from the PXRD and the FTIR are similar to the simulated data for both UiO-66 and MOF-808. However, for UiO-66, the TGA and the apparent surface area show deviations. Simultaneously, the MOFs’affinityforPFASisevaluatedthroughsorbtionexperimentswith prepared stock solutions of PFAS. To study this, a 19F-NMR is used, with which the sorption capacity and kinetics are determined. To evaluate these, both the amount of MOF to PFAS, along with the sorption over different time intervals, are included. Evaluating the PFAS sorption experiments,MOF-808exhibitsthebestaffinityforbothPFOA andTFA,removingapproximately89%and58%respectively.Saturationisreachedwithin10 min. UiO-66 also shows good sorption, though with smaller capacity, removing approxima tely 86% of PFOA and 36% of TFA, with saturation reached within 20 min. However, UiO-66 reaches saturation faster for PFOA. The sorption follows pseudo-second-order kinetics. The roles of the solvents are discussed further with respect to the results, and thus pos sible areas of improvement of the project. Additionally, the reusability of recovered MOF materials is discussed as a potential direction for future studies.