Adsorption and electrochemical behavior investigation of methyl blue onto magnetic nickel-magnesium ferrites prepared via the rapid combustion process

Abstract As a widely used water-soluble azo dye, methyl blue has aroused widespread concern for its environmental problems. In this paper, magnetic nickel-magnesium ferrites were deemed as a promising dye adsorbent, and they could be synthesized through a rapid combustion process. The properties of the nanoparticles were acquired by the scanning electron microscope (SEM), the energy dispersive spectroscopy (EDS), the X-ray diffraction (XRD), the vibrating sample magnetometer (VSM), the high resolution transmission electron microscopy (HRTEM), the N2 adsorption-desorption isotherms, and the Fourier transform infrared spectroscopy (FTIR). The structure analysis demonstrated that the average particle size of magnetic nickel-magnesium ferrites was 59.2 nm, the saturation magnetization was 34.1 A·m2/kg and the specific surface area was 94.69 m2/g. After investigating the ratio of nickel to magnesium and the key parameters affecting the properties of ferrites, the adsorption of methyl blue onto the nanoparticles was discussed. Adsorption kinetics and isotherm models were employed to fit the relevant data, and the adsorption capacity of nanoparticles on methyl blue reached 306.4 mg/g when the initial concentration of methyl blue was 900 mg/L. The effect of pH value on the adsorption was explored, and seven cycles of the sample were recorded. Subsequently, the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) curves of the nanoparticles before and after adsorption were measured. To sum up, nickel-magnesium ferrites had the advantages of low cost, magnetic separation, facile preparation, high adsorption efficiency, and reusability, which suggested it had a broad application prospect in the field of dye removal.