Long-chain PFAS removal from industrial wastewater via microporous carbide-derived carbon

Per - and polyfluoroalkyl substances (PFAS), particularly perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA), are widespread in aquatic environments and pose significant environmental and health risks. Their strong carbon‑fluorine bonds hinder degradation by conventional treatment methods, necessitating effective remediation strategies. Although adsorption is a promising approach, conventional adsorbents often suffer from limited capacity, slow kinetics, and reduced performance in complex water matrices. Carbide-derived carbons (CDCs), with their ultra-microporous structure and high specific surface area (1081.8 m 2 /g), have demonstrated strong potential for contaminant removal, yet their application to PFAS adsorption remains unexplored. In this study, CDC was evaluated as a high-performance adsorbent for long-chain PFAS removal. Adsorption experiments reached maximum capacities of 950.7 mg/g for PFOA and 1218.5 mg/g for PFNA, with adsorption approaching equilibrium at ~60 min. PFNA exhibited higher affinity than PFOA due to its longer perfluoroalkyl chain, which strengthens hydrophobic interactions, promotes multilayer aggregation on CDC surfaces, and enhances adsorption via electrostatic effects. Isotherm analysis indicated heterogeneous adsorption involving both monolayer and multilayer behavior, while kinetics followed a fractal pseudo-first-order model, suggesting diffusion-controlled processes. Thermodynamic results confirmed a spontaneous and endothermic mechanism. CDC exhibited good reusability, maintaining over 85% removal after five regeneration cycles. High performance was retained in the presence of competing ions, with PFOA and PFNA removals of 84.6–95.5% and 86.1–95.7% in anionic solutions, and 88.5–93.7% and 89.9–95.3% in cationic solutions, respectively. Up to 90% removal was maintained at NaCl concentrations of 0.001–0.1 M. In PFAS-spiked industrial wastewater, CDC achieved 89.8% and 92.5% removal of PFOA and PFNA, demonstrating strong selectivity in complex matrices. Overall, CDC shows strong potential as a robust, regenerable, and an effective candidate for long-chain PFAS adsorption in real-world water treatment systems. • Longer-chain PFNA exhibited higher affinity for carbide-derived carbon than PFOA. • Maximum capacities reached 950.7 mg/g (PFOA) and 1218.5 mg/g (PFNA). • Equilibrium was attained within 60 min via heterogeneous, diffusion-limited adsorption. • High removal was achieved in saline, ion-competitive systems and after five adsorption cycles. • Adsorption driven by electrostatic, hydrophobic, diffusion, hydrogen bonding, ion-exchange interactions.