Chromate adsorption on amine-functionalized core/shell magnetic mesoporous material

The core–shell magnetic mesoporous microspheres were synthesized by a sol–gel method using cetyltrimethylammonium bromide as structure-directing agent. The microspheres were characterized by powder X-ray diffraction, N2 physical adsorption–desorption, magnetic measurements, scanning electron microscopy, transmission electron microscopy, and so on. The results show that the microspheres possess very strong magnetization, high surface area, large pore volume, and uniform accessible mesopores. The core–shell magnetic mesoporous microspheres were further amine functionalized using (3-aminopropyl) triethoxysilane (APTES), and presented positive charge under acid condition. Thus the negatively charged chromate anions can be adsorbed on the composites through electrostatic interaction. The adsorption experiment results demonstrate that the adsorption of chromate anions fit well by Langmuir isotherm and the maximum adsorption capacity reaches to 1.03 mmol Cr/g adsorbent.