Preparation of quaternary ammonium magnetic chitosan microspheres and their application for Congo red adsorption.

In this study, novel green in situ quaternary-ammonium-functionalized magnetic chitosan microspheres (IQMCM) were synthesised. The resulting adsorbent was characterised by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, X-ray photoelectron spectroscopy, and zeta potential analysis. The characterization results indicated that the IQMCMs possessed spherical morphology and superior specific thermal stability, magnetic properties, and surface charges. Batch adsorption experiments revealed that the adsorption capacities of the IQMCM microspheres to Congo red (CR) was 630.21 mg/g at a dosage of 0.15 g/L, temperature of 333 K, pH of 5.0, and initial dye concentration of 100 mg/L, and the corresponding removal rate reached 94.53 %. According to the kinetics, adsorption isotherms, and thermodynamics experiment results, the adsorption of CR dye coincided with a spontaneous endothermic monolayer chemisorption process. After saturated adsorption, this magnetic adsorbent could be rapidly separated from water and reused with little adsorption capacity loss. Overall, these results show that IQMCMs are potentially applicable in wastewater treatment.