Preparation of Graft Cd²⁺ Ion-Imprinted Membrane and Its Recognition Selectivity

By using ethylenediamine (EDA) as the reagent, aminated microfiltration membrane of polysulfone (AMPSF) was prepared through chemical modification of chloromethylated polysulfone microfiltration membrane (CMPSF). Then surface-initiating system of -NH₂/S₂O₈^2- was constituted at the interface between AMPSF membrane and aqueous solution using AMPSF membrane as basement membrane, sodium p-styrene sulfonate (SSS) as functional monomer, Cd²⁺ as template ion, and N, N-methylene double acrylamide (MBA) as cross linker. Graft Cd²⁺ ion-imprinted membrane (GIIM) was then prepared through the method of graft/crosslinking-polymerizing and simultaneous ion imprinted on the membrane surface. Fourier transform infrared spectroscopy (FT-IR) was adopted to determine the structure of the graft Cd²⁺ ion-imprinted membrane, scanning electron microscope (SEM) was used to observe the cross-sectional morphology of the GIIM, and optical microscope (OM) was used to observe the surface morphology of the GIIM. Furthermore approaches like static binding, competitive adsorption, separation and osmosis were adopted to examine the performance of the imprinted membrane in recognition selectivity and osmotic separation of Cd²⁺. Results indicate that the Cd²⁺ ion-imprinted membranes with grafting type have sound performances in binding affinity, recognition selectivity and osmotic separation of Cd²⁺. The combination capacity of the GIIM reaches as high as 1.41 mmol/cm², and the penetration capacity of the GIIM reaches as high as 0.95 mg/mL. The selection coefficients of the imprinted membrane to Cd²⁺, which are relative to the reference ion Pb²⁺ and Zn²⁺, are 9.97 and 11.9 respectively. As a result, the imprinted membrane is expected to provide an effective way for the selective separation of Cd²⁺ in waste water.