Adsorptive removal of cationic dye from aqueous solutions using activated carbon prepared from Crataegus monogyna/sodium alginate/polyaniline composite beads: Experimental study and molecular dynamic simulation

This study presents a novel composite beads, AC@Alg-PANI, consisting of activated carbon (AC) derived from Crataegus monogyna , sodium alginate (Alg), and polyaniline (PANI), tested for the removal of methylene blue (MB). The physicochemical characteristics of the composite beads were analyzed using methods such as pH PZC , FTIR, TGA/DTA, SEM, and BET. Moreover, factors affecting the adsorption of MB, such as initial pH, dye concentration, adsorbent weight, ionic strength, and temperature, were also explored. A full factorial design was implemented to identify the optimum conditions for removal, which were found to be a pH of 6, an adsorbent amount of 100 mg, and a dye concentration of 100 mg/L. The isotherm data indicated that the adsorption of MB by AC@Alg-PANI follows the Langmuir model, with a maximum adsorption capacity of 774.6 mg/g. The adsorption kinetics followed the pseudo-first-order model, indicating that the adsorption process is physical in nature. The thermodynamic results suggest that MB adsorption on AC@Alg-PANI was favorable, spontaneous, and endothermic. Additionally, after five regeneration cycles, the composite beads demonstrated excellent recyclability for MB dye removal with high efficiency. Furthermore, molecular dynamics simulations (MDS) of the adsorption energy highlighted the physically spontaneous nature of the process, involving various weak interactions, including van der Waals forces, intermolecular interactions, hydrogen bonding, and pi-electron interactions.