Rapid, Selective and Efficient Cationic Dye Removal Using a Poly(Acrylic Acid‐Co‐Styrene Sulfonate)/Electrospun Carbon Nanofiber Hybrid Hydrogel

ABSTRACT Hydrogel‐based adsorbents are promising for pollutant removal, offering a 3D porous structure, tunable surface properties, and high‐water permeability, enabling efficient contaminant adsorption. This study investigated the synthesis, characterization, and adsorption capacity of electrospun carbon nanofiber‐incorporated poly(sodium‐4‐styrene sulfonate‐co‐acrylic acid) hydrogel (ECNFs@PSA) for removing organic dyes from aqueous solutions. The incorporation of ECNFs significantly enhanced the hydrogel's physical properties and adsorption performance. The adsorption performance of PSA and ECNFs@PSA was evaluated through batch studies using methylene blue (MB) as a representative cationic dye. Experimental parameters including pH range (3–10), MB concentration (500–1000 mg/L), contact duration (5–300 min), and temperature variation (30°C–45°C) were systematically investigated to assess their influence on MB removal efficiency. The pseudo‐first‐order model provided the best kinetic fit, indicating physical adsorption dominance. The Langmuir–Freundlich isotherm most accurately described the equilibrium data, revealing heterogeneous surface adsorption with multilayer characteristics. The ECNFs@PSA hydrogel exhibited rapid methylene blue (MB) adsorption, reaching equilibrium within 28 min with an enhanced capacity of 874.36 mg/g—significantly outperforming the pristine PSA hydrogel (819.63 mg/g, 96 min). FTIR and reusability study confirmed that MB adsorption occurred primarily through electrostatic interactions (via –COO − /–SO 3 − groups) and π–π stacking with ECNFs' graphitic structure. Notably, ECNFs@PSA demonstrated excellent selectivity for cationic dyes, with > 99% removal efficiency under alkaline conditions. These findings demonstrate that ECNFs@PSA is a highly effective, physically driven adsorbent with potential for sustainable wastewater treatment applications, particularly for cationic dye removal.