Preparation Of Surface Ion Imprinted Polymer Based On Mesoporous Silica Material And Study On Its Selective Separationfor Heavy Metal Ions

Owning the large specific surface area, fast mass transfer and large binding capacity, mesoporous material has been widely applied in adsorption, and especially mesoporous silica material with abundant silanol groups on the surface can be easily further functionalized. Currently, preparing the surface imprinted polymer with target recognition ability based on the mesoporous silica material has been a research hotspot in adsorption.In recent years, plenty of heavy metal ions were released into environment with industrial wastewater, which has seriously threatened the health of human and organism. It’s urgent to develop the novel surface ion imprinted polymers which possess characters of large adsorption capacity, excellent selectivity and good reusability. In this issue, we prepared three types of novel surface ion imprinted polymers based on mesoporous silica materials with different structure, with Pb(II), Cr(VI), Cu(II) as template ions, respectively, and studied their application in selective adsorption of heavy metal ions. Details below:(1) Highly selective lead ion imprinted mesoporous silica adsorbents(Pb(II)-IMS) were prepared through co-condensation pathway with 3-(γ-aminoethylamino)-propyl-trimethoxysilane(AAPTS)(Pb(II)-IMS-NN) and 3-aminepropyl-triethoxysilyl(APTES)(Pb(II)-IMS-N) as monomers, respectively. The prepared adsorbents were characterized by Fourier transmission infrared spectra(FT-IR), X-ray photoelectron spectroscopy(XPS), power X-ray powder diffraction(XRD), Transmission electron microscope(TEM), Scanning electron microscope(SEM), Thermogravimetric Analysis(TGA) and Nitrogen adsorption-desorption techniques. The results showed that the synthesized adsorbents presented highly ordered mesoporous structure and excellent thermal stability. Comparing with Pb(II)-IMS-N, Pb(II)-IMS-NN performed a higher adsorption capacity in a series of static and dynamic adsorption experiment, and was further applied to a continuous fixed-bed column study at different conditions. It was found that breakthrough time of the fixed-bed increased with the increase in bed depth, but decreased with increasing flow rate and initial Pb(II) concentration, and the dynamic adsorption data was more consistent with the Thomas model than Adams-Bohart model. Furthermore, the Pb(II)-IMS-NN showed more excellent recognition and binding affinity toward the target lead ions than Pb(II)-IMS-N.(2) Treating 3-methacryloxypropyltrimethoxy-silane(MPS) modified SBA-15 as matrix, we developed a novel Cr(VI) anion surface imprinting polymer(Cr(VI)-IIP) with dual functional monomers of methacrylic acid(MAA) and 4-vinyl pyridine(4-VP). A series of characterization(i.e. FT-IR, EDS, SEM, TEM, Power-XRD, N2 adsorption-desorption analysis and TGA) showed Cr(VI)-IIP was successfully prepared and the mesoporous structure was well maintained after imprinting polymerization. The batch static adsorption study demonstrated Cr(VI)-IIP exhibited the optimum adsorption performance in the condition of pH 2.0 and 25 oC in aqueous solution, and the maximum adsorption capacity was 96.32 mg g-1. The experimental data of adsorption kinetics and the isothermal adsorption process of Cr(VI)-IIP accorded with pseudo-second-order model and the Langmuir model, respectively. Selectivity experiments confirmed that Cr(VI)-IIP owned an excellent recognition ability for Cr(VI) among the competition ions(i.e. Cr(III), Cu(II), Cd(II) and Ni(II)). In the fixed-bed study, Cr(VI)-IIP showed an ideal dynamic adsorption capacity for Cr(VI) with an efficiently reusability.(3) Depending on a general protocol for the making of surface-imprinted core-shell microparticles via a RAFT-mediated approach, we developed a novel Cu(II) imprinted polymer with magnetic mesoporous silica nanosphere(γ-Fe2O3@meso-SiO2) as support. Attributing to the controlled/living polymerization mechanism of the RAFT polymerization process, the Cu(II) imprinted polymer prepared by RAFT polymerization(IIP-RAFT) represented more well-defined morphology, more mono-dispersed properties, and much higher magnetic responsiveness, comparing to the Cu(II) imprinted polymer prepared by traditional free-radical polymerization(IIP-TP). Moreover, in the static saturation binding experiments, a higher binding capacity of IIP-RAFT(210.29 mg g-1) was also found than IIP-TP(144.84 mg g-1). Afterwards, a series of adsorption experiments was carried out to systematacially evaluate the adsorption performance of the as-prepared IIP-RAFT. And the results showed that IIP-RAFT exhibited an excellent selectivity, good reusability and desirable dynamic adsorption behavior, which could be an ideal candidate sorbent for the removal of Cu(II) in the real wastewater.