| It is always a research hotspot for the separation of platinum metals, because the separation methods reported previously is usually limited owing to its low efficiency, high cost or time consuming and difficulty in performance. Recently, a new material called ion imprinted polymer (IIP) has attracted much attention as the efficient sorbents for separation procedures due to its high selectivity, stability, reusability, ease of use, simplicity in preparation. In this paper, a Pd (II) ion imprinted polymer and a Ir(IV) ion imprinted polymer, both with good selectivity and high adsorption capacity, were prepared after the polymerization conditions were carefully optimized. The properties, structures and application of the resultant IIPs were also studied. This thesis mainly included three parts:1. A review was given for the basic methods of separation, enrichment and detection of palladium by consulting a large number of literatures.2. Studies on preparation, characteristics and application of a Pd(II) ion imprinted polymer(1) The bonding mechanism between PdCl42-and three functional monomers named2-acetamidoacrylic acid (AAA),2-(allylmercapto)nicotinic acid (ANA) and N-allylurea (NAU), which have not been used in the preparation of MIPs or IIPs so far as we know, were studied by ultraviolet spectrum (UV), infrared spectroscopy (IR) and computer simulation technology. The results obtained from ultraviolet spectrum indicated that a1:1complex was formed in methanol between PdCl42-and the functional monomer with the binding constant of5.30×102,1.1O×103and3.71×102for AAA, ANA and NAU, respectively. Moreover, from the results obtained by infrared spectroscopy and computer simulation technology, it could presume that the binding sites of the functional monomer to Pd(II) is oxygen atom in the carbonyl group of AAA and NAU, or nitrogen atom in the pyridine ring of ANA, which is expect to be a suitable functional monomer for the preparation of a Pd(II) ion imprinted polymer by taking the results of ultraviolet spectrum, infrared spectroscopy and computer simulation technology into considered together.(2) To optimize the polymerization conditions and methods for the preparation of Pd (II) ion imprinted polymer,22kinds of Pd(II) ion imprinted polymers were synthesized in methanol by using various polymerization methods together with different templates, functional monomers and different combinations of functional monomer (ANA) and cross-linker (EGDMA). The rebinding studies revealed that the imprinted polymer (IIP7) prepared by the precipitation polymerization with PdCl42-as template, ANA as functional monomer and the ratio of Pd (II), ANA and EGDMA as1:4:40possessed the maximum adsorption capacity (3.043mg/g) and satisfactory imprinting factor (1.32) in5mL of methanol solution containing50μg of Pd(II). At the meanwhile, adsorption isotherms, Scatchard analysis and adsorption kinetics of the resultant polymers (IIP7) were studied. Two kinds of binding sites with high-affinity and low-affinity were found in IIP7. The concerned dissociation constants of0.0915mmol/L and0.974mmol/L together with the maximum binding sites of8.253mg/g and34.37mg/g were obtained for the high-affinity and low-affinity binding sites, respectively. It was also demonstrated that the speed of adsorption of IIP7to Pd (II) is very quickly, and the saturation adsorption capacity could be reached within10min.(3) The structure and surface morphology of the obtained polymers were characterized by IR spectrum and SEM, respectively. The surface area, pore volume and average pore radius of these polymers were determined by the BET nitrogen adsorption analysis. The results suggested that the surface of IIP exhibited a more porous and rough structure than NIP, and the particle size distribution of the polymers prepared by precipitation polymerization were homogeneous.(4) An ion-imprint based solid phase extraction (IIP-SPE) method was developed by using the obtained IIP7particles as sorbent after the experimental parameters affecting the extraction efficiency and selectivity were studied carefully. The extraction experiments involved three steps, i.e. loading, washing and eluting. For loading, the sample solution was adjusted to pH7.0and passed through the column at a rotation rate of solid-phase extraction instrument of3.0rmp. After loading, the column was washed with0.5mL of aqueous solution with pH7.0, and then eluted with1mL of1.0mol L-1HCl at the same rotation rate of the instrument. To examine the reliability of the proposed IIP-SPE method, a volume of0.5mL of sample containing1.5μg of each of Rh(III), Ru(III), Pd(II), Ir(IV) and Pt(IV) was analyzed by this procedure. The results indicated the percent extraction of Pd (II) was more that80%, while only about20%of other platinum metals were extracted.3. Studies on preparation and properties of a Ir (IV) ion imprinted polymerOn the basis of the previous researches in our laboratory, a Ir(IV) ion imprinted polymer was prepared by precipitation polymerization with IrCl62-as template ion, ANA as functional monomer, EGDMA as crosslinker monomer, and the ratio of Ir(IV), ANA and EGDMA as1:5:40. The obtained IIPs(IIP5) showed a comparatively high adsorption capacity, good selectivity together with a tolerable adsorption equilibrium (30min). The adsorption capacity and imprinting factor of this IIP in5mL of methanol solution containing0.31mg of Ir(IV) was12.73mg/g and1.42.The results obtained from Scatchard analysis pointed that there are two classes of binding sites existed in IIP5with the dissociation constants of0.7370mmol/L and2.321mmol/L, and the affinity binding sites of60.88mg/g and103.0mg/g, respectively. In addition, the structure, surface morphology and pore properties were characterized by IR spectrum, SEM and BET nitrogen adsorption analysis. |
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