Synthesis of quaternized magnetic chitosan and adsorption performance for methyl orange from aqueous solution

Chitosan is considered an excellent carrier material with great potential due to its good biocompatibility, abundant reserves, and high chemical reactivity. However, chitosan's chemical instability and low mechanical strength limit its applications. In this study, quaternized magnetic chitosan (QMCS) was prepared by modifying magnetic chitosan microspheres (MCS) with quaternary ammonium. The obtained adsorbent was characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The effect of pH value and adsorbent dosage on the adsorbent's performance was investigated. The experimental results indicated that QMCS exhibited superior adsorption performance for methyl orange (MO) compared to MCS. At 298 K and pH 4, the adsorption capacity of QMCS for a 125 mg L^-1 methyl orange (MO) solution reached 486.13 mg g^-1, with a removal efficiency of 99.38%. The adsorption behavior of the adsorbent towards MO was in good agreement with the Langmuir isothermal model and the quasi-second-order kinetics model. The mechanism of adsorption may be attributed to electrostatic interactions and ion exchange. The synthesis of QMCS was simple, environmentally friendly, and has significant potential for water pollution treatment.