AbstractMagnetic chitosan composite microparticles (MCCPs) were successfully prepared using a simple one-step co-precipitation method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). The experimental results showed that the particles possessed a honeycomb-like porous structure and had super-paramagnetic properties, with a saturation magnetization of about 33.3 emu/g. Congo red (CR), an anionic azo dye, was used to investigate the adsorption properties of the MCCPs. The adsorption kinetics data and isotherms produced from these experiments indicated that CR adsorption onto the MCCPs was best fitted with a pseudo-second-order kinetic equation and was well described by the Langmuir model. Thermodynamic parameters such as the changes in Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also estimated; the results revealed that the adsorption process was spontaneous and endothermic. The regeneration studies demonstrated that the MCCPs can be used as a reusable adsorbent for CR adsorption from aqueous solution. The molecular similarity between chitosan and cellulose suggests that the present results might serve as a model of what might be achieved with a cationic derivative of cellulose.