Polyaniline chitosan beads for enhanced methyl red adsorption: Experimental and molecular simulation insights

This study proposes a novel adsorbent - polyaniline (PANI) chitosan (CS) beads - for the efficient removal of methyl red (MR) dye from aqueous solutions. Multiple synthesis strategies were explored to optimize adsorption performance. The synthesized PANI CS beads exhibited enhanced MR adsorption kinetics and capacity than traditional adsorbents such as activated carbon. The MR adsorption kinetics followed pseudo first-order model and homogeneous surface diffusion model, and the Langmuir and Freundlich isotherm models fit the equilibrium data well. The synthesized beads maintained effective performance across a range of pH conditions and in the presence of competitive organic and inorganic species, demonstrating robustness under realistic water treatment scenarios. Different regenerants were tested to evaluate the reusability of PANI CS beads, and 0.1 M HCl solution showed the best regeneration performance, maintaining their adsorption performance effectively over 6 cycles. Molecular simulation was conducted and confirmed strong MR adsorption on PANI, driven primarily by electrostatic interaction and supported by van der Waals force. The negative adsorption energy and total energy validated the adsorption spontaneity and system stability. These findings demonstrate that PANI CS beads provide a distinct advancement over the conventional adsorbent, offering a high-performance, regenerable material for practical application in water treatment.