<span lang="EN-AU">An Eco-Friendly Hydrotalcite-Graphene Oxide/Chitosan Composite<span lang="EN-AU"> as a Highly Effective Adsorbent for Organic Contaminant Removal from Polluted Water

This study presents a novel design of eco-friendly hydrotalcite–graphene oxide/chitosan (MgAl–GO/CS) composite beads with a hierarchically integrated adsorption architecture for efficient azo dye removal. Unlike conventional single-component adsorbents, the developed system combines the layered anion-exchange capability of MgAl hydrotalcite, the π-conjugated structure of graphene oxide, and the proton-responsive functionality of chitosan. This study presents a novel design of eco-friendly hydrotalcite–graphene oxide/chitosan (MgAl–GO/CS) composite beads with a hierarchically integrated adsorption architecture for efficient azo dye removal. Unlike conventional single-component adsorbents, the developed system combines the layered anion-exchange capability of MgAl hydrotalcite, the π-conjugated structure of graphene oxide, and the proton-responsive functionality of chitosan into a unified bead form, enabling synergistic adsorption mechanisms. Structural characterization by SEM, XRD, and FT-IR confirmed the successful incorporation of all components, forming accessible active sites and interconnected pathways for mass transfer. Batch adsorption experiments using Methyl Orange (MO) demonstrated that removal efficiency is strongly governed by initial concentration, adsorbent dosage, temperature, and pH. Notably, under acidic conditions, protonation of chitosan amino groups significantly enhances electrostatic attraction with MO. In parallel, GO introduces π–π stacking interactions with the aromatic dye structure and hydrogen bonding via oxygenated groups, while MgAl hydrotalcite contributes through anion exchange and interlayer intercalation, a feature rarely exploited in bead-type composites. Kinetic analysis follows a pseudo-second-order model (R۲ = ۱.۰۰۰), confirming chemisorption-dominated behavior, whereas equilibrium data fit the Freundlich isotherm (R۲ > ۰.۹۸۵), indicating heterogeneous multilayer adsorption. Importantly, the optimized ۰.۲MgAl–GO/CS composite exhibits a maximum adsorption capacity of ۵۵.۸۹ mg/g, outperforming many reported chitosan-based systems. This work highlights a new strategy for integrating layered double hydroxides and graphene derivatives into biopolymer matrices, offering enhanced adsorption performance through cooperative mechanisms and providing strong potential for practical wastewater treatment applications. into a unified bead form, enabling synergistic adsorption mechanisms. Structural characterization by SEM, XRD, and FT-IR confirmed the successful incorporation of all components, forming accessible active sites and interconnected pathways for mass transfer. Batch adsorption experiments using Methyl Orange (MO) demonstrated that removal efficiency is strongly governed by initial concentration, adsorbent dosage, temperature, and pH. Notably, under acidic conditions, protonation of chitosan amino groups significantly enhances electrostatic attraction with MO. In parallel, GO introduces π–π stacking interactions with the aromatic dye structure and hydrogen bonding via oxygenated groups, while MgAl hydrotalcite contributes through anion exchange and interlayer intercalation, a feature rarely exploited in bead-type composites. Kinetic analysis follows a pseudo-second-order model (R۲ = ۱.۰۰۰), confirming chemisorption-dominated behavior, whereas equilibrium data fit the Freundlich isotherm (R۲ > ۰.۹۸۵), indicating heterogeneous multilayer adsorption. Importantly, the optimized ۰.۲MgAl–GO/CS composite exhibits a maximum adsorption capacity of ۵۵.۸۹ mg/g, outperforming many reported chitosan-based systems. This work highlights a new strategy for integrating layered double hydroxides and graphene derivatives into biopolymer matrices, offering enhanced adsorption performance through cooperative mechanisms and providing strong potential for practical wastewater treatment applications.

کلیدواژه ها:

MgAl hydrotalcite ، Chitosan ، Graphene oxide-based adsorbent ، Removal of azo dye