Enhanced Adsorption of Malachite Green Using Chitosan-grafted-poly(acrylic acid)/MWCNTs Hydrogel Nanocomposite: Synthesis, Characterization and Kinetic Studies

Abstract

This study investigates the synthesis and application of a chitosan-grafted-poly(acrylic acid)/carboxylated multi-walled carbon nanotubes hydrogel nanocomposite (CS-g-p(AA)/MWCNTs-COOH) for the removal of Malachite Green (MG) dye from aqueous solutions. The nanocomposite was synthesized via free-radical copolymerization and characterized using FTIR and FESEM, confirming successful grafting and carbon nanotube incorporation. Adsorption studies revealed that equilibrium was achieved within 40 minutes, with the process following pseudo-second-order kinetics (R² = 1.0000), suggesting chemisorption as the rate-limiting step. The effect of various parameters including contact time, pH, temperature, and initial dye concentration was systematically investigated. FTIR analysis before and after adsorption demonstrated significant spectral changes, indicating strong interactions between the dye and the composite through multiple mechanisms including electrostatic attractions, hydrogen bonding, and π-π stacking. FESEM images further confirmed successful adsorption, showing dye molecule aggregates on the composite surface with reduced porosity. This eco-friendly nanocomposite demonstrates significant potential for efficient removal of synthetic dyes from industrial effluents.