An ion-imprinted amino-functionalized silica gel sorbent prepared by hydrothermal assisted surface imprinting technique for selective removal of cadmium (II) from aqueous solution

Abstract A new ion-imprinted amino-functionalized silica gel sorbent was synthesized by the hydrothermal-assisted surface imprinting technique using Cd 2+ as the template, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AAAPTS) as the functional monomer, and epichlorohydrin as the cross-linking agent (IIP-AAAPTS/SiO 2 ) for the selective removal of Cd 2+ from aqueous solution, and was characterized by FTIR, SEM, nitrogen adsorption and the static adsorption–desorption experiment method. The specific surface area of the IIP-AAAPTS/SiO 2 sorbents was found to be 149 m 2 g −1 . The results showed that the maximum static adsorption capacities of IIP-AAAPTS/SiO 2 sorbents by hydrothermal heating method and by the conventional heating method were 57.4 and 31.6 mg g −1 , respectively. The IIP-AAAPTS/SiO 2 sorbents offered a fast kinetics for the adsorption and desorption of Cd(II). The relative selectivity coefficients of IIP-AAAPTS/SiO 2 sorbents for Cd 2+ /Co 2+ , Cd 2+ /Ni 2+ , Cd 2+ /Zn 2+ , Cd 2+ /Pb 2+ and Cd 2+ /Cu 2+ were 30.68, 14.02, 3.00, 3.12 and 6.17, respectively. IIP-AAAPTS/SiO 2 sorbents had a substantial binding capacity in the range of pH 4–8 and could be used repeatedly. Equilibrium data fitted perfectly with Langmuir isotherm model compared to Freundlich isotherm model. Kinetic studies indicated that adsorption followed a pseudo-second-order model. Negative values of Δ G ° indicated spontaneous adsorption and the degree of spontaneity of the reaction increased with increasing temperature. Δ H ° of 26.13 kJ mol −1 due to the adsorption of Cd 2+ on the IIP-AAAPTS/SiO 2 sorbents indicated that the adsorption was endothermic in the experimental temperature range.