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/FeO-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 for AR and 353.5 mg·g 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/FeO-NPs@PHAC for effective pollutant removal and antibacterial use, emphasizing its potential for sustainable environmental remediation and biomedical applications.