Regenerable polyaniline-chitosan composite bead for efficient adsorption of per- and polyfluoroalkyl substances from water

In this study, novel polyaniline-chitosan (PANI-CS) composite beads were synthesized and systematically evaluated as adsorbents for per- and polyfluoroalkyl substances (PFAS) removal from aqueous solutions. PANI-CS beads were developed to overcome the low surface area and low adsorption capacity of chitosan, while providing a mechanically stable, bead-form structure that enhances adsorption performance and is better suited for practical continuous-flow water treatment systems. The PANI-CS beads achieved > 95% removal of five representative PFAS with varying structures and chain lengths within 24 h, demonstrating adsorption kinetics comparable to the commercial PFAS-selective resin while offering potential cost and sustainability advantages. Column breakthrough studies, including both rapid small-scale column tests (RSSCT) and bench-scale fixed-bed experiments, validated the adsorbent's scalability and practical applicability for continuous-flow systems. RSSCT further showed that the PANI–CS bead outperformed commercial granular activated carbon by exhibiting delayed PFAS breakthrough. Moreover, the adsorbent exhibited excellent reusability, with 0.1 M HCl achieving over 99% desorption of perfluorobutanoic acid and 87% desorption of perfluorooctanoic acid after four adsorption-desorption cycles—a critical advantage over many single-use PFAS adsorbents. Molecular dynamics simulations revealed that PFAS adsorption is predominantly governed by electrostatic interactions, with additional contributions from van der Waals forces. Overall, these findings identify PANI-CS beads as a promising sustainable adsorbent for PFAS remediation, combining high adsorption capacity, rapid kinetics, excellent reusability, and mechanistic insights that advance the rational design of next-generation polymer-based adsorbents.