Preparation and Characterization of Thiourea-Containing Silica Gel Hybrid Materials for Hg(II) Adsorption

Thiourea-containing silica gel hydrid materials (HO-SG-GPTS-TS and HE-SG-GPTS- TS) were prepared by homogeneous and heterogeneous methods for Hg(II) adsorption. Structures of HO-SG-GPTS-TS and HE-SG-GPTS-TS were confirmed by FTIR, C-13 NMR, Si-29 NMR, SEM, TGA, and porous structure analysis. Homogeneous preparation is demonstrated to be more efficient than heterogeneous one to load more functional groups and therefore shows better adsorption property. The optimal adsorption pH was 6 for the adsorbent. Kinetics of adsorption was well fitted by a pseudo-second-order model and dominated by film diffusion process. The isotherm adsorption was best described by Langmuir isotherm model and processed by chemical mechanism. Thermodynamics implied the adsorption was spontaneous and endothermic. Selective adsorption indicated HO-SG-GPTS-TS exhibited excellent selectivity for Hg(II) in the binary system contains Pb(II), Ni(II), and Co(II).