Utilization of waste iron sludge to achieve bifunctional magnetic and adsorptive cores for synthesizing magnetic chitosan microspheres: Arsenic decontamination and its mechanism

Environmental protection has become a pressing concern for numerous countries, with waste-to-waste strategies at the forefront. This study demonstrated the successful fabrication of bifunctional magnetic microspheres for arsenic remediation using waste iron sludge as precursor material. The synthesized material exhibited a monodisperse particle size distribution ranging from 300 to 500 μm, with a saturation magnetization of 22 emu/g ensuring efficient magnetic recovery. Maximum arsenic adsorption capacities of 21.99, 21.63, and 14.2 mg/g were observed at pH 5.7, 7.0, and 9.0, respectively, while stable adsorption performance persisted across a broad pH range (2−10).Kinetic analysis revealed close adherence to the pseudo-second-order model (R² > 0.99), complemented by Freundlich isotherm fitting suggesting multilayer adsorption. Notably, the 28.6 % reduction in zeta potential post-adsorption, coupled with enhanced adsorption capacity at elevated ionic strength, confirmed predominance of chemisorption processes through inner-sphere complexation mechanisms. Competitive adsorption experiments showed that carbonate, silicate, and phosphate ions substantially inhibited As(V) removal through ligand competition, while chloride, nitrate, and sulfate exhibited negligible effects. The material retained 76 % removal efficiency after 5 regeneration cycles, demonstrating remarkable environmental adaptability and engineering application potential. Consequently, MCMB emerged as an efficient adsorbent for arsenic removal.