Magnetic ion-imprinted and –SH functionalized polymer for selective removal of Pb(II) from aqueous samples

A magnetic ion-imprinted polymer (Fe 3 O 4 @SiO 2 -IIP) functionalized with –SH groups for the selective removal of Pb(II) ions from aqueous samples was synthesized by surface imprinting technique combined with a sol–gel process using 3-mercaptopropyl trimethoxysilane as monomer, tetraethyl orthosilicate as cross-linking agent, and Pb(II) ion as template. The Fe 3 O 4 @SiO 2 -IIP was characterized by infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectrometry. Fe 3 O 4 @SiO 2 -IIP showed higher capacity and selectivity than that of Fe 3 O 4 @SiO 2 -NIP. The effects of initial concentration of Pb(II) and pH of medium on adsorption capacity of Fe 3 O 4 @SiO 2 -IIP were studied. The experimental data fits well with the Langmuir adsorption isotherm. The maximum Pb(II)-sorption capacity calculated from Langmuir isotherm is 32.58   mg/g and 16.50   mg/g for Fe 3 O 4 @SiO 2 -IIP and Fe 3 O 4 @SiO 2 -NIP, respectively. Kinetics studies show that the adsorption process obeys a pseudo-second-order kinetic model with high correlation coefficient ( R 2   =   0.9982). The separation factor of Fe 3 O 4 @SiO 2 -IIP for Pb(II)/Cu(II), Pb(II)/Zn(II), and Pb(II)/Co(II) are 50.54, 52.14, and 37.39, respectively. The adsorption thermodynamic parameters Δ G , Δ H and Δ S were −4.98   kJ/mol, 3.27   kJ/mol and 28.84   J/mol/K, respectively. In addition, the spent Fe 3 O 4 @SiO 2 -IIP can be refreshed by simple washing with aqueous HCl solution, and there is no significant decrease in adsorption capacity after a test of up to five cycles, demonstrating that the Fe 3 O 4 @SiO 2 -IIP is stable and reusable.