Synthesis and Characterization of Customizable Polyaniline-Derived Polymers and Their Application for Perfluorooctanoic Acid Removal from Aqueous Solution

Exploring selective, high-affinity adsorbents is a priority for the development of improved per- and polyfluoroalkyl substance (PFAS) remediation technologies. We hypothesize that affinity and selectivity of secondary amine hydrophobic polymers for perfluorooctanoic acid (PFOA) can be tailored by modifying the polymer surface charge and hydrophobic backbone. We synthesized an array of pyrrole and several aniline derivatives with different substitutions on the aniline ring. We characterized these polymers using a multifaceted approach, including surface areas, charge densities, and molecular structures using N₂−BET adsorption, electrophoretic mobility, as well as infrared- and X-ray spectroscopy techniques. The affinity and selectivity of these polymers for PFOA were then tested across a wide range of aqueous solution pH values and interpreted based on the characterization data. We found that a balance between the addition of hydrophobic substitutions to the polymer backbone and the presence of cationic amine groups provides the highest affinity of the new adsorbents to PFOA. The data also indicate that conformational changes in polymer tertiary structure can regulate the balance between electrostatic and hydrophobic adsorption mechanisms. Among the tested polymers, poly-o-toluidine, polyaniline, and poly-o-anisidine are the most promising adsorbents.