Economical magnetic activated carbon for methylene blue removal from water

Abstract

This study investigates an easy synthesis method of magnetic activated carbon (Fe₃O₄/AC) composites by ultrasonic mechanical blending of Fe₃O₄ particles and activated carbon (AC) powder at different mass ratios. The materials with the best performance were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), specific surface and porosity analyzer (BET), hysteresis loop meter (VSM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS). The as-prepared Fe₃O₄/AC was used to remove the contaminant methylene blue (MB) from solution. The effects of initial solution pH, material dosage, and temperature on MB removal were studied. A series of batch experiments demonstrated that the Fe₃O₄/AC with a mass ratio of Fe₃O₄ to AC = 1:5 showed a higher adsorption capacity of 251.3 ± 2.0 mg/g at 20 °C and pH = 6.5. Isotherm and kinetic studies indicated that the MB adsorption onto Fe₃O₄/AC was exothermic in a chemical monolayer adsorption process. The purification mechanism of Fe₃O₄/AC was investigated, FT-IR results showed that MB molecules adhered to Fe₃O₄/AC after purification. From the results of XPS full spectrum and high resolution spectrum, the possible purification mechanism is inferred as follows: electronic transfer between =N⁺ in MB and CO/C─O in Fe₃O₄/AC, as well as π-π interaction between the skeleton sheet of Fe₃O₄/AC and aromatic ring of MB. This study provides the theoretical reference and experimental basis for recovery and utilization of easily-obtained Fe₃O₄/AC to remove MB from wastewater.