Adsorptive removal of methylene blue onto MFe2O4: kinetics and isotherm modeling

Abstract

In this study, ferrites nanoparticles of formula MFe2O4 (M = Co, Zn, and 50% Co/50% Zn) were synthesized and characterized by X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and the N2 adsorption–desorption technique. The magnetic properties were studied using a vibration sample magnetometer, and the magnetic susceptibility was measured as a function of temperature. Among the specimens evaluated, CoFe2O4 has the largest saturation magnetization (66.380 emu/g), and ZnFe2O4 exhibits the largest surface area (120.1 m2/g). The prepared nanoparticles were investigated as adsorbents for the removal of methylene blue (MB) from an aqueous solution at different contact times, pH, and initial concentrations. The influence of the adsorption conditions was examined, finding that the adsorption process is favored in alkali conditions and high MB concentration. The Langmuir and Freundlich models fit the adsorption data of CoFe2O4 and the composite, whereas only the Freundlich model fits the experimental results of ZnFe2O4. The adsorption kinetics of MB adsorption onto MFe2O4 is better described by pseudo-first-order and pseudo-second-order models than by an intraparticle diffusion model.