Green synthesis of magnetic activated carbon-chitosan composite for multi-heavy metal removal

This study is novel in integrating magnetic recovery, multi-metal adsorption capability, and validation under realistic water conditions within a single composite system. Discharges of heavy metal-contaminated wastewater into the environment have increased due to rapid industrialization and population growth, posing major threats to ecosystems and human health. Therefore, in this study, to effectively and simultaneously remove numerous heavy metals from aqueous solutions, a multifunctional activated carbon/Fe 3 O 4 -chitosan composite was successfully developed via a green synthesis method. The composite combines the strong metal-binding functional groups of chitosan, the magnetic recoverability of Fe 3 O 4 nanoparticles, and the large surface area and porosity of activated carbon to produce a synergistic structure with improved adsorption performance and usability. A porous surface morphology, a well-developed pore structure, a uniform elemental distribution, an abundance of hydroxyl and amine functional groups responsible for metal binding, and adequate magnetic flexibility for quick separation were all revealed by characterization analyses that verified the successful formation of AC/Fe 3 O 4 -chitosan composite. Moreover, in a multi-component system in which all metals coexisted simultaneously, batch experiments conducted at an initial metal concentration of 105 mg/L, adsorbent dosage of 50 mg, contact time of 60 min, pH 7.0, and temperature of 55 °C showed removal efficiencies of 90.2% for arsenic, 75.78% for chromium, 70.72% for aluminum, 55.12% for boron, and 30.5% for lithium. The composite enables rapid and contactless magnetic separation, eliminating the need for filtration or centrifugation. Additionally, the performance was validated using real water matrices, accounting for competing ions and organic matter. In conclusion, the results show that the developed composite provides a practical, efficient, and magnetically recoverable approach to treat complex wastewaters contaminated with heavy metals, indicating its great potential for long-term environmental remediation applications. • Synthesized magnetic AC-chitosan composite efficiently removes multiple heavy metals. • Box-Behnken design is utilized to evaluate the combined effects of operational parameters. • Characterization analyses confirmed a composite with a high surface area of 147 m 2 /g. • Optimized conditions achieved high removal efficiencies: As 93%, Al 70%, Li 50%, B 75%, Cr 85%. • The composite exhibits promising results for sustainable multi-metal removal from waters.