Recovery of nitrate from water streams using amine-grafted and magnetized SBA-15

Mesoporous silica SBA-15 was modified using amine-grafting and magnetization to enhance its nitrate adsorption capacity and to render the spent silica particles recoverable from the working solution after use. Such modifications result in an outstanding adsorbent for recovering nitrate from water streams by adding high adsorption ability and easy handling to the intrinsic properties of SBA-15. When the molar ratio of SBA-15 to 3-aminopropyltriethoxysilane (APTES) is 10 : 3 during amine-grafting, the resulting SBA-15G-4 sample exhibits the highest nitrate adsorption capacity (44.9 mg/g) among the tested materials. The other sample, 67-SBA-15MG, which was magnetized with iron nitrate content of 67 wt% of SBA-15, exhibits sufficient magnetic force for recovery from the working solution, while maintaining ～81% of nitrate adsorption capacity of the corresponding amine-grafted SBA-15G-5. Furthermore, the 67-SBA-15MG material retains its adsorption capacity and magnetic strength after ten adsorption/desorption cycles, indicating excellent characteristics as a magnetically recyclable adsorbent for recovering nitrate.