Magnetic Fe3O4/Fe‐Mn binary oxide/bentonite nanocomposite—a novel adsorbent for removal of reactive red 195 dye from water

Abstract

In this study, a nanocomposite, Fe3O4/Fe‐Mn binary oxide/bentonite (FFMB), was synthesized, characterized and evaluated its adsorption behavior of azo Reactive Red 195 dye (RR‐195) in aqueous solution. The results of characterization (X‐ray diffraction, Fourier transform infrared spectroscopy, field emission scanning and transmission electron microscopies, vibration‐sample magnetometer, etc.) demonstrate that FFMB consists of Fe3O4 core and Fe2O3‐MnO2 binary oxide shell, which are distributed relatively uniformly on the exfoliated bentonite support with BET surface area of about 188 m2 g−1. It exhibits superparamagnetic properties with saturation magnetization of 39.6 emu g−1. The results of batch adsorption experiments show that the material has high ability of RR‐195 adsorption in terms of both adsorption rate and capacity. The adsorption efficiency was highest at pH 2–3. The adsorption process followed the pseudo‐second‐order kinetics and Langmuir isotherm models with a rather high maximum adsorption capacity of 163.4 mg g−1. Besides, Weber–Morris kinetic and Temkin isotherm models also provide useful insight into the adsorption mechanism. The material shows a good reusability. After 5 adsorption–desorption cycles the adsorption efficiency reached about 75% of the first cycle and the saturation magnetization decreased insignificantly. These results reveal that FFMB can become an alternative adsorbent for azo dye removal from wastewaters.