Eco-Friendly Magnetic Nanocomposite for Mordant Black 17 Removal: Optimization via Central Composite Design

This work targets removal of the hazardous azo dye Mordant Black 17 (MB-17) from water using a green-synthesized magnetic Fe⁰/Fe₃O₄/chitosan (FMC) nanocomposite. The FMC material was prepared by immobilizing Fe⁰/Fe₃O₄ within a chitosan matrix using Camellia sinensis leaf extract as a natural reducing agent, and was characterized by SEM, FT-IR, XRD, EDX, and VSM to confirm its morphology, structure, and magnetic separability. Batch adsorption experiments, supported by equilibrium, kinetic, and thermodynamic analyses, were coupled with Central Composite Design (CCD) to optimize operating conditions for hazard mitigation. MB-17 uptake onto FMC followed the Langmuir isotherm and pseudo-second-order kinetic model, indicating monolayer, chemisorption-controlled adsorption with a maximum capacity of 66.36 mg g⁻¹ and a removal efficiency of up to 98.7% under optimized conditions. Thermodynamic parameters showed that the process is spontaneous and endothermic within the investigated temperature range. Comparative tests demonstrated that FMC vastly outperforms its individual components, with removal efficiencies of 98.7% for FMC versus 43.9, 31.3, and 37.6% for chitosan, Fe⁰, and Fe₃O₄ nanoparticles, respectively, highlighting a strong synergistic effect between the biopolymer matrix and redox-active iron phases.