Hierarchically imprinted organic-inorganic hybrid sorbent for selective separation of mercury ion from aqueous solution

A new type of hierarchically organic-inorganic hybrid sorbent was prepared by a double-imprinting approach for the selective separation of Hg(II) from aqueous solution. In the imprinting process, both mercury ions and surfactant micelles (cetyltrimethylammonium bromide, CTAB) were used as templates, N-[3-(trimethoxy-silyl)propyl]ethylenediamine (TPED) as functional monomer, and tetraethoxysilane (TEOS) as cross-linking agent. The mercury ions and surfactant were removed from sorbent via acid leaching and ethanol extraction, respectively. The adsorption property and selective recognition ability of the sorbents were studied by equilibrium-adsorption method. Results showed that in the presence of Cu(II) or Cd(II) the biggest selectivity coefficient of the imprinted sorbents for Hg(II) was over 100, which is much higher than those of non-imprinted sorbents. The largest relative selectivity coefficient (k′) of the ion-imprinted functionalized sorbent between Hg(II) and Cu(II) was over 300, and between Hg(II) and Cd(II) over 200. The uptake capacities and the selectivity coefficients of the hierarchically imprinted sorbent were much higher than those of the sorbent prepared without CTAB template. Furthermore, the new imprinted sorbent possessed a fast kinetics for the removal of Hg(II) from aqueous solution with the saturation time less than 5 min, and could be used repeatedly. This sorbent has been successfully applied to the separation and determination of the trace Hg(II) in real water samples and those spiked with standards. This new sorbent can be used as an effective solid-phase extraction material for the selective preconcentration and separation of Hg(II) in environmental samples.