Polyaniline as an Integrated Amine-Redox Platform for Reversible Electrosorption and Energy-Efficient PFAS Remediation: From Molecular Mechanisms to System Integration

Abstract

Advanced water treatment technologies must integrate material function with mechanistic understanding to achieve effective and sustainable contaminant remediation. Here, we introduce polyaniline (PANI) as an integrated amine-redox platform that enables reversible electrosorption of per- and polyfluoroalkyl substances (PFAS). By tuning its redox and protonation states, PANI switches between electrostatic and hydrophobic binding modes, allowing controllable capture and release. Spectroscopic analyses combined with molecular dynamics simulations uncover the mechanistic basis of this redox- and pH-dependent affinity: emeraldine states facilitate fast, reversible uptake via electrostatic interactions, whereas leucoemeraldine favors slower, irreversible hydrophobic binding. At the system level, a scalable flow-cell platform achieved >90% PFOA removal from 100 ppb feed solutions of both synthetic electrolyte and real wastewater. Within an adsorb-desorb-defluorinate strategy, reversible electrochemical capture and release concentrated PFOA 7.6-fold, generating an enriched stream suitable for downstream anodic oxidation. Subsequent treatment with a boron-doped diamond anode delivered an 88% defluorination ratio, nearly double that of direct oxidation, while reducing overall energy demand by more than 20-fold. These findings highlight the value of amine-redox materials that combine simplicity, reversibility, and mechanistic clarity, and demonstrate how electrosorption can bridge separation and destruction in energy-efficient treatment of dilute contaminants.