Activated carbon/Mn0.6Zn0.4Fe2O4 composites: Facile synthesis, magnetic performance and their potential application for the removal of methylene blue from water

Abstract

Activated carbon/Mn0.6Zn0.4Fe2O4 (AC/MZF) composites were synthesized by a facile bonding method and were used as adsorbents for the removal of methylene blue (MB) dye from water. The structure, morphology and magnetic properties of the as-prepared composites were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and with a vibrating sample magnetometer. The results indicated that Mn0.6Zn0.4Fe2O4 particles were bonded with the activated carbon in the composite. The composite adsorbents exhibited a clear hysteretic behavior under an applied magnetic field, which allowed their magnetic separation from water. Batch experiments were carried out to investigate the adsorption isotherms and kinetics of MB on the composite. The experimental data fitted well with the Freundlich model. The 1/n (where n is the Freundlich constant) values of MB adsorption by AC/MZF were in the range of 0.1024–0.1419, showing that the adsorption process was favorable. The adsorption kinetics were found to follow the pseudo-second-order kinetic model. The mean free energy evaluated through the Dubinin–Radushkevich model was below 8kJmol−1, which indicates physisorption. Additionally, it was found that the adsorption of MB on AC/MZF was a spontaneous endothermic physical process according to thermodynamic calculations. AC/MZF could be recovered well using 3wt.% H2O2, and its adsorption capacity could preserve an excellent level of 274.0mgg−1 after five runs. It was indicated that the as-prepared composites could be used as promising and effective adsorbents for the removal of MB from water.