(582e) Comparison of Fluorine Functionalization Strategies in MOFs for the Removal of Poly- and Perfluoroalkyl Substances from Water
AIChE Annual Meeting
2021
2021 Annual Meeting
Separations Division
Molecular and Data Science Modeling of Adsorption II
Monday, November 15, 2021 - 2:10pm to 2:30pm
Poly- and perfluoroalkyl substances (PFAS) have been extensively used in clothing, cosmetics, packaging, furniture, cookware, and firefighting industries. Due to the presence of highly stable C–F bonds in their molecular structure, PFAS are highly resistant to degradation. As a result, these compounds can accumulate in the environment and cause pollution. Efficient methods are sought for the removal of PFAS from water.
Perfluorooctanoic acid (PFOA) is one of the most commonly utilized PFAS. In this work, by using molecular simulation methods, we compare fluorine functionalization strategies that can be used for creating MOF materials that are effective in the removal of PFOA from water. We identify four different approaches in the literature: 1) Synthesis of MOFs that has inorganic fluorinated building units, 2) Functionalization of organic ligands with fluorine, 3) MOFs with a mix of pores which have hydrophobic and hydrophilic character 4) Coordination of fluorinated alkyl chains to open metal sites.
The adsorption of PFOA from water in several MOF structures developed by using the aforementioned fluorine functionalization approaches have been studied with Monte Carlo simulations in the canonical (NVT) and grand canonical (GCMC) ensembles. Radial distribution functions (RDF), Henry's coefficients and adsorption loading of PFOA and water have been calculated. For each strategy, we discuss the advantages and the disadvantages by comparing the results and explain the mechanism of separation. In most cases, PFOA and water compete for the same preferred adsorption sites and the separation process is driven by entropic effects.