Hierarchical Fe₃O₄@Mg/Al-LDH@Chitosan Nanocomposite for Rapid and Reusable Congo Red Adsorption from Complex Water Systems

Abstract

Synthetic dye contamination represents a persistent challenge in wastewater management due to the chemical stability and toxicity of these compounds. This study presents the synthesis and evaluation of a magnetically recoverable nanocomposite composed of magnetite, layered double hydroxide (LDH), and chitosan (Fe₃O₄@LDH@CS) for the removal of Congo Red from aqueous systems. The material was prepared using a microwave-assisted approach designed to enhance synthesis efficiency and reduce energy consumption. Comprehensive characterization (XRD, FTIR, SEM, and TGA) confirmed the successful integration of magnetite nanoparticles within an LDH matrix stabilized by chitosan, resulting in a structurally robust and porous hybrid adsorbent. Batch adsorption experiments demonstrated high removal efficiencies (>95%) across a broad pH range, with optimal performance near neutral conditions. Kinetic analysis indicated that adsorption followed a pseudo-second-order model, suggesting chemisorption as the dominant mechanism, while isotherm modeling supported monolayer adsorption behavior. Thermodynamic parameters revealed that the process is spontaneous and endothermic, with improved adsorption at elevated temperatures. The nanocomposite maintained high performance over multiple regeneration cycles and showed strong applicability in real water matrices, including industrial wastewater and seawater. These findings highlight the potential of Fe₃O₄@LDH@CS as an efficient and reusable adsorbent for practical dye remediation applications.