Isotherm, kinetic and thermodynamic modelling of liquid phase adsorption of the heavy metal ions Zn(II), Pb(II) and Cr(VI) onto MgFe2O4 nanoparticles

Abstract

MgFe2O4 nanoparticles are synthesized by sol-gel method and the adsorption characteristics of these nanoparticles on the removal of Zn(II), Pb(II) and Cr(VI) ions from their aqueous solutions are analysed. The samples are characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman Spectroscopy. Batch adsorption studies are carried out to investigate the effect of adsorption parameters such as adsorbent dose, pH, temperature, contact time and initial ion concentration. The feasibility and spontaneity of the adsorption process is checked by thermodynamic analysis. Four adsorption kinetics models viz. Pseudo first-order, Pseudo second-order, Intra particle diffusion and Elovich model and four adsorption isotherm models viz Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin isotherm models are studied and employed to model the adsorption equilibrium data. All the kinetics and isotherm parameters including rate constants and maximum adsorption capacity are determined and compared. The adsorption process best fits the Pseudo-second-order kinetics model and Langmuir adsorption isotherm model. Of the three heavy metal ions studied, the adsorption of Zn(II) ions by MgFe2O4 nanoparticles exhibits the best performance, followed by Pb(II) and Cr(VI) ions respectively. By regenerability study, the extent of reuse of the MgFe2O4 nanoparticles is checked.