Understanding PFAS Adsorption: How Molecular Structure Affects Sustainable Water Treatment

Per- and polyfluoroalkyl substances (PFASs) are a broad group of synthetic chemicals characterized by strong carbon–fluorine bonds, making them highly persistent and widely distributed in the environment. Their chain length and functional head groups, such as sulfonate and carboxylate groups, determine key molecular properties like hydrophobicity, acidity, and sorption behavior. These properties significantly impact the effectiveness of PFAS removal from water systems. This review provides a structural classification of PFASs and explores removal strategies, with a particular emphasis on adsorption. It examines sustainable adsorbents, including both natural materials (e.g., cellulose, chitosan, lignin, and cyclodextrins) and engineered synthetic materials (e.g., covalent organic frameworks, metal–organic frameworks, and molecularly imprinted polymers). The discussion highlights important parameters such as chain length and functional chemistry, as these can greatly influence removal efficiency. Furthermore, the discussion addresses the adsorption mechanisms-such as electrostatic attraction, hydrophobic interaction, and fluorophilic interactions-to show how they contribute in different systems. By combining structural insights with adsorption performance data, this review aims to help design and select sustainable, high-performance adsorbents for efficiently reducing PFASs in contaminated water.