Adsorption efficiency of alizarin red and 2,4-dichlorphenoxyacetic acid from wastewater onto chitosan and iron oxide-coated peanut husk-activated carbon: Isothermal, kinetic, and antibacterial analyses.

In this study, a magnetic biocomposite (CS/Fe3O4-NPs@PHAC) was developed by depositing chitosan (CS) onto peanut husk-activated carbon (PHAC) using acid digestion and pyrolysis. This composite was used to remove the water contaminants (including alizarin red (AR) and 2,4-dichlorophenoxyacetic acid (2,4-D)) and for antibacterial applications. Adsorption studies showed that presence of salts reduced the efficiency, while the acidic conditions enhanced adsorptive process. Maximum adsorption capacities were found to be 389.4 mg·g-1 for AR and 353.5 mg·g-1 for 2,4-D at 313 K. Isotherm models (Langmuir, Koble-Corrigan, Freundlich) exhibited high correspondence with the equilibrium data while the kinetics analysis showed that the adsorption followed the pseudo-second-order model. The composite demonstrated excellent regeneration, stability, and eco-friendliness. Mechanistic analysis revealed interactions like hydrogen bonding, electrostatic attraction, and π-π stacking in pollutant removal. Moreover, the composite exhibited significant antibacterial activity against Staphylococcus aureus and Escherichia coli. These results highlight the dual functionality of CS/Fe3O4-NPs@PHAC for effective pollutant removal and antibacterial use, emphasizing its potential for sustainable environmental remediation and biomedical applications.