Polyethyleneimine Modified Magnetic Microcrystalline Cellulose for Effective Removal of Congo Red: Adsorption Properties and Mechanisms

In this study, microcrystalline cellulose modified with Fe3O4 and polyethyleneimine (Fe3O4/MCC-PEI(70K-5)) was synthesized for Congo red (CR) adsorption. Various batch experiments were conducted to explore the effects of initial concentration, contact time, solution pH, and cationic concentration. The results showed that the adsorption process of CR onto Fe3O4/MCC-PEI(70K-5) were spontaneous and endothermic, and strictly followed pseudo-second-order and Freundlich models. The equilibrium time of CR adsorption onto Fe3O4/MCC-PEI(70K-5) at 298 K was 100 min and the maximum adsorption capacity was 862.25 mg/g. Zeta-potential, XPS, and FT-IR analyses proved that the adsorption behavior was primarily ascribed to the electrostatic interactions between Fe3O4/MCC-PEI(70K-5) and CR molecules. Additionally, Fe3O4/MCC-PEI(70K-5) has a good performance of regeneration and reuse, which maintained a high adsorption capacity even after five consecutive regenerations.