Cd(II)-imprinted polymer sorbents prepared by combination of surface imprinting technique with hydrothermal assisted sol-gel process for selective removal of cadmium(II) from aqueous solution

A new ion-imprinted thiocyanato-functionalized silica gel sorbents was synthesized by the combination of a surface imprinting technique with a hydrothermal-assisted sal-gel process with Cd(II) as the template, 3-thiocyanatopropyltriethoxysilane (TCPTS) as the functional monomer, and epichlorohydrin as the cross-linking agent (IIP-TCPTS/SiO2) for the selective removal of Cd(II) from aqueous solution. The Cd(II)-imprinted thiocyanato-functionalized silica sorbents was characterized by FTIR, SEM, nitrogen adsorption and the static adsorption-desorption experiment method. The results showed that the maximum static adsorption capacity of IIP-TCPTS/SiO2 sorbents prepared by hydrothermal heating method was 2.3 times as much as the conventional heating method. The IIP-TCPTS/SiO2 sorbents offered a fast kinetics for the adsorption and desorption of Cd(II). The static uptake capacity and selectivity coefficient of IIP-TCPTS/SiO2 sorbents were higher than those of the non-imprinted sorbents. IIP-TCPTS/SiO2 sorbents had a substantial binding capacity in the range of pH 4.2-8.6 and could be used repeatedly. The Langmuir adsorption model was more favorable than the Freundlich adsorption model. Kinetic studies indicated that the adsorption followed a pseudo-second-order model. Various thermodynamic parameters such as Delta G degrees, Delta H degrees and Delta S degrees were evaluated with results indicating that this system was a spontaneous and endothermic process. The results showed that IIP-TCPTS/SiO2 sorbents could be employed as an effective material for the selective removal of Cd(II) from aqueous solutions. (C) 2011 Elsevier B.V. All rights reserved.