Innovative nanocomposites for pollutant capture: Adsorption of rhodamine B dye using polyaniline-coated chitosan trisodium citrate nanocomposites.

Wastewater contamination by organic dyes, especially Rhodamine B (RhB), possess a significant environmental challenge. This study explores a novel bio sorbent for the removal of RhB dye from contaminated water, using chitosan trisodium citrate-modified magnetic nanoparticles (Fe₃O₄@CSTSC@PANI) coated with polyaniline. The nanocomposite was characterized by FT-IR, XRD, HRTEM, SEM, BET surface analysis. The UV-visible spectroscopy was used to monitor the adsorption of dye on the nanocomposite. The Fe₃O₄@CSTSC@PANI nanocomposite exhibits a spherical core-shell morphology with a size range of 29-53 nm, a BET surface area of 13.099 m/g, and high reusability. The pore area of the material increased from 0.8058 m/g at 15.29 Å radius to 10.65 m/g at 1310.89 Å, with a corresponding change in pore volume from 0.0006.16 cc/g to 0.0227 cc/g. This shows the significant contribution of the porous and mesoporous structures of polyaniline-coated chitosan trisodium citrate (nanocomposites) to the adsorption performance for pollutant capture such as Rhodamine B dye. Adsorption studies showed optimal RhB removal of 97.2 % at near neutral pH. Adsorption was most optimal at pH 6-9, with the highest efficiency near neutral pH, which facilitates electrostatic interactions. High temperature (10-70 °C) promoted the endothermic adsorption process, improving the dye uptake. The optimal adsorbent dosage (0.21-1.6 g/L) and equilibrium contact time (30-840 min) were determined. The nanocomposite material showed good recovery, maintaining high efficiency after 4 reuse cycles, demonstrating its practicality in sustainable environmental remediation. The adsorption mechanism was elucidated by isotherm and kinetic studies, which revealed that the process followed a pathway dominated by chemisorption facilitated by the interaction between polyaniline-coated chitosan nanocomposites and Rhodamine B dye molecules. This is the synergistic effect of electrostatic attraction, hydrogen bonding and π-π interactions, confirming the strong affinity of the mixture for the dye.