Synthesis of organo-functionalized magnetic microspheres and application for anionic dye removal

Organo-functionalized microspheres with the mesoporous silica shell and magnetic core (Fe3O4) have been successfully prepared by using a simple method for removing anionic dye pollutants, e.g., solvent green 7 (SG 7) from wastewaters. Transmission electron microscope (TEM), N-2 adsorption analysis, FTIR, thermal gravimetric analysis (TGA) and zeta potential measurements are used to structurally characterize the microspheres, which are evaluated to be magnetizable, with a diameter of about 290 nm and an average pore diameter of 2.57 nm. Zeta potential data in the pH range between 2 and 10 suggest that the microspheres are with positive charge due to the modified cetyltrimethylammonium bromide (CTAB) on magnetic core. Additionally, the adsorption results exhibit a high adsorption capacity and separation convenience, and therefore with the help of an applied magnetic field the microspheres can be used as powerful adsorbent for anionic dye pollutants removal. The pseudo-second-order kinetic model provides the best correlation of the experimental data. Furthermore, the experimental results show that both electrostatic interaction and physical adsorption are possible for the mechanisms of SG 7 removal. (C) 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.