Highly selective and efficient removal of lead with magnetic nano-adsorbent: Multivariate optimization, isotherm and thermodynamic studies.

2-Hydroxyethylammonium sulfonate immobilized on γ-Fe2O3 nanoparticles (γ-Fe2O3-2-HEAS) was synthesized by the reaction of n-butylsulfonated γ-Fe2O3 with ethanolamine. The structure of the resulting product was confirmed by fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) spectrometry, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), elemental analysis, N2 adsorption-desorption and vibrating sample magnetometer (VSM) techniques. The supported ionic liquid on γ-Fe2O3 was applied as a new and green adsorbent to remove Pb(II) from aqueous solution. The effect of adsorption parameters such as pH, shaking time and amount of the adsorbent were investigated using two level three factor (2(3)) full factorial central composite design with the help of Design-Expert, Stat-Ease Inc. version 9.0 software. The significance of independent variables and their interactions were tested by means of the analysis of variance (ANOVA) with 95% confidence limits (α=0.05). The thermodynamic parameters of the adsorption process are estimated. It is found that the process is exothermic and spontaneous. The Langmuir and Freundlich models have been also applied to evaluate the removal efficiency and the data were correlated well with the Freundlich model.