Adsorption of Hg2+ by thiol functionalized hollow mesoporous silica microspheres with magnetic cores

Novel hollow mesoporous silica spheres with magnetic cores (HMSMCs) were successfully synthesized by using hybrid magnetic carbon (Fe3O4/C) spheres as templates. The microspheres were further functionalized with (3-mercaptopropyl)trimethoxysilane (MPTS) to produce thiol functionalized HMSMCs (SH-HMSMCs), and their ability to absorb traces of toxic Hg2+ was evaluated. The characterization results revealed that the hollow microspheres were 250-300 nm in diameter. The thickness of the shell was about 50 nm, in which contained an inner core of Fe3O4 crystallites with a size of about 10 nm. It was also found that the saturation magnetization of the sample was 62.5 emu g(-1) and the BET surface area was 421 m(2) g(-1). These magnetic hybrid silica microspheres with thiol functional groups were found to have a high affinity to Hg2+, and were able to reduce even a low concentration of Hg2+ (<1 mg L-1) down to about 0.53 mu g L-1, which was less than the Hg2+ content in the drinking water standard. The super strong affinity towards Hg2+ was attributed to the synergistic effect of the thiol groups and the unique structure of the microspheres. Moreover, the microspheres as adsorbents could be easily separated by an external magnetic field, and the adsorbed Hg2+ on the adsorbents could be removed by using hydrochloric acid, thus the adsorbents are readily reusable.