Effective removal of Pb(II) using magnetic Co0.6Fe2.4O4 micro-particles as the adsorbent: Synthesis and study on the kinetic and thermodynamic behaviors for its adsorption

Abstract

• The adsorbent of Co 0.6 Fe 2.4 O 4 micro-particles were synthesized by a simple method. • The adsorbent shows relatively high adsorption capacity for the removal of Pb(II). • The Pb(II) adsorbed Co 0.6 Fe 2.4 O 4 micro-particles could be easily isolated by magnetic separation. • The adsorption kinetics could be fitted well by the pseudo-second-order model. • The Pb(II) adsorption onto Co 0.6 Fe 2.4 O 4 micro-particles is endothermic and spontaneous. Magnetically separable adsorbent composed of Co 0.6 Fe 2.4 O 4 micro-particles were successfully prepared by thermal decomposition of the Co 0.6 Fe 2.4 C 2 O 4 ·2H 2 O. The as-prepared samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray energy dispersive spectroscopy (EDS). The specific surface area of the sample is determined to be 97.155 m 2 g −1 , with uniform pore size distribution centering at about 7.432 nm. The as-obtained Co 0.6 Fe 2.4 O 4 micro-particles exhibits ferromagnetic behavior at room temperature, which makes it magnetically separable under external magnetic field. The as-obtained magnetic Co 0.6 Fe 2.4 O 4 micro-particles exhibits excellent adsorption capacity and high adsorption rate for the removal of Pb(II) in aqueous solution. The maximum adsorption capacity of Pb(II) is up to 80.32 mg g −1 and 88% of the Pb(II) can be removed within the initial 30 min of contact time. The effects of contact time, initial pH, ionic strength and temperature on the adsorption behavior of Pb(II) were systematically investigated. The kinetics of the adsorption process follows the pseudo-second-order model and is controlled by the film diffusion process. The equilibrium data can be fitted well using the Langmuir isotherm model, suggesting that the uptake of Pb(II) ions is a mono-layer adsorption process. Meanwhile, the mean free energy E calculated by D-R isotherm model demonstrates that the adsorption process is implemented via the chemical ion-exchange mechanism. The thermodynamic studies illustrate that the adsorption process is endothermic and spontaneous in nature.