Synthesis and evaluation of an ion-imprinted functionalized sorbent for selective separation of cadmium ion

An ion-imprinted functionalized sorbent for selective separation of Cd2+ from aqueous solution was prepared by molecular imprinting technique in combination with the sol-gel process. The procedures involved the synthesis of mesoporous silica through hydrolysis of tetraethoxysilicate with cetyltrimethylammonium bromide as the structure director, the complex formation between Cd2+ and 3-mercaptopropyltrimethoxysilane, and subsequent co-hydrolysis and co-condensation of the complex with the mesoporous silica. After template Cd2+ was removed with hydrochloric acid, specific cavity for selective recognition of Cd2+ was left. The selectivity of the sorbent was investigated by a batch competitive ion-binding experiment using an aqueous Cd2+ and Pb2+ mixture. The largest selectivity coefficient for Cd2+ in the presence of Pb2+ was found to be over 67, the largest relative selectivity coefficient between Cd2+ and Pb2+ over 18. The uptake capacity and selectivity coefficient of the imprinted functionalized sorbent are higher than those of the nonimprinted sorbent. The sorbent offered a fast kinetics for the extraction/stripping of Cd2+ and good recyclability.