Advanced Chitosan‐Based Nanocomposites for Simultaneous Removal of Anionic and Cationic Dyes: Process Optimization, Mechanistic Modeling, and Regeneration Study

ABSTRACT

The uncontrolled discharge of synthetic dyes from industrial effluents remains a critical challenge due to their resistance to conventional treatment processes. Although adsorption has been widely explored, limited studies address the simultaneous removal of oppositely charged dyes with clear mechanistic interpretation and regeneration feasibility. In this study, chitosan‐based binary and ternary composites incorporating graphene oxide and polypyrrole were strategically synthesized for removal of cationic and anionic dyes. The ternary composite has maximum removal efficiencies of 95.72% for methylene blue and 99.36% for tartrazine. Kinetic analysis revealed that adsorption follows the pseudo‐second‐order model while equilibrium data were best described by Langmuir, Tempkin, Toth, Redlich, and Sips models suggesting monolayer adsorption on a heterogeneous surface. Thermodynamic parameters indicated a negative enthalpy (−8.217 to −30.488 kJ/mol) and Gibbs free energy (−4.727 to −16.018 kJ/mol) confirming spontaneous and exothermic nature while negative entropy (−2.591 to −48.686 J/mol K) suggests increased order at the solid–liquid interface during adsorption. Mechanistic interpretation revealed that adsorption is governed by a combination of electrostatic attraction, ππ interactions, hydrogen bonding, and surface complexation. The composite exhibited excellent reusability (48.63%–51.90% removal efficiency after five cycles). Therefore, the engineered chitosan‐based composites present a robust and regenerable adsorbent for industrial wastewater treatment applications.