Preparation of thermo-sensitive surface ion-imprinted polymers based on multi-walled carbon nanotube composites for selective adsorption of lead(II) ion

A novel thermo-sensitive lead ion-imprinted polymers (IIPs) based on multi-walled carbon nanotubes(MWCNTs) was prepared by reverse suspension polymerization, using chitosan (CS), hydroxyethyl methacrylate and N-isopropylacrylamide as the polymeric monomers, Pb(II) as the template and glutaraldehyde as the crosslinking agent. The chemical structure, morphology and magnetic properties were characterized by Fourier transform infrared spectrometer(FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), thermogravimetry (TGA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The adsorption properties of IIPs were investigated by ultraviolet spectrophotometr (UV-vis) and atomic absorption spectrophotometry (AAS). The results showed that IIPs had obvious temperature sensitivity, and the adsorption capacity and the adsorption equilibrium time of imprinted polymers could be controlled by changing the temperature. The maximum adsorption capacity of IIPs for Pb2+ reached 83.20 mg/g at 35 degrees C. The adsorption process was more in accord with the pseudo second-order kinetic and the Langmuir isotherm adsorption model. The selectivity coefficients of Pb2+/Cu2+, Pb2+/Cd2+, Pb2+/Zn2+ and Pb2+/Ni2+ were 15.66, 59.50, 24.79 and 20.52, respectively, indicating that IIPs had excellent selective adsorption for Pb2+. In addition, IIPs was recycled 6 times, and the adsorption capacity was not obviously reduced. The electrochemical properties of ion-imprinted carbon paste electrodes (CPE/IIPs) were characterized by cyclic voltammetry (CV), and CPE/IIPs exhibited excellent electrochemical performance.