The Preparation of Fe3O4-MnO2-SiO2-NH2 for Selective Adsorption of Pb(II) in Mixed Solution of Pb(II), Cu(II), and Ni(II)

In this paper, a novel amino-functionalized Fe3O4-MnO2-SiO2-NH2 adsorbent material was prepared by successive modifying Fe3O4 with KMnO4 and SiO2 to remove heavy metal ions in mixed solution of Pb(II), Cu(II), and Ni(II). The adsorption experiments showed that initial pH value had a significant effect on the adsorption capacity of the materials for heavy metals in solution. Moreover, the materials exhibited strong selective adsorption for Pb(II). Transmission electron microscopy (TEM) results showed that the innermost dark center was the Fe3O4 core with a thickness of about 200 nm, and the outermost light circle was a coated SiO2 shell with a thickness of about 30 nm, while MnO2 can be seen between the dark center and the light circle. Various factors affecting the uptake behavior such as contact time, temperature, pH, and initial concentration of Pb(II) were investigated. The kinetics were evaluated utilizing the Lagergren pseudo-first-order and pseudo-second-order models. The best interpretation for the equilibrium data was given by Freundlich isotherm. The recycling experiment showed that Fe3O4-MnO2-SiO2-NH2 kept its adsorption and desorption efficiencies constant over 5 cycles. Importantly, the Fe3O4-MnO2-SiO2-NH2 was able to selectively remove over 73% of Pb(II) not only in mixed solution of Pb(II), Cu(II), and Ni(II) but also remove 94.7% in only Pb(II) solution at pH 6 within 1 h.