| Surface imprinting technique, which was based on molecular imprinting technology, make the recognition site on the surface of supported material, so that, it can improve the binding rate between recognition site and template molecular, and enhance the extraction efficiency of imprinted material. Surface imprinted materials, which possess not only higher selectivity but also faster binding kinetics, have been widely used in separation field of trace elements.Thorium,which is the most abundant radioactive element in nature, is widely applied to the purpose of commerce and industry, especially in nuclear energy. But as is known to us, thorium poses a significant threat to the ecosystem and especially to people due to the severe radioactive and toxicological effects on living organisms even at very low level. So, precise determination and extraction of trace thorium in environmental and geological materials is particularly significant. However, the direct determination of thorium by the instrumental techniques including atomic absorption spectrometry (AAS), and inductively coupled plasma atomic emission spectrometry (ICP-AES) is still difficult because of the very trace content and the presence of complex matrix. Pre-concentration and selective separation of thorium prior to its photometric determination is required for the high sensitivity and selectivity of analytical method. Molecular imprinted polymer-solid phase extraction (MIP-SPE) is a kind of sampling pre-treatment which aim at the separation and pre-concentration of trace material in complex samples. Therefore, the work is focused on the selective solid phase extraction and separation of trace thorium with surface imprinting technique, this dissertation consists of three parts, as follows:1. Comprehensive analysis and introduction are given for the principle of molecular imprinting technique and ion imprinting technique, progress in surface imprinted material and the determination and separation of thorium in recent years.2. A novel ion imprinted material based on modified silica was prepared by grafted copolymerization with thorium(IV) chosen as template ion. The structure of the prepared imprinted polymer was characterized by SEM and BET, the imprinted polymer's adsorption behavior and the selectivity were systematically studied by static and column method. Under optimal condition, the maximum adsorption capacity was 56.8 mg g-1, the relative selectivity coefficient values of the imprinted adsorbent for Th(IV)/La(III), Th(IV)/Ce(III) and Th(IV)/U(VI) were 78.3, 82.6 and 50.8. The proposed method was applied to determination of thorium in real samples and natural water samples. Moreover, the precision and the detection limit were 2.19% and 0.54μg L-1, respectively.3. A new type of surface imprinted material for selective separation of thorium was prepared using thorium (IV)-4-vinylpyridine-MPABAP complex as template, EGDMA as a cross-linker and AIBN as initiator. The results showed that the maximum adsorption capacity was 59.2 mg g-1, the adsorption of Th(IV) on IIP reached saturation values within 15 min, which fitted well with Lagergren first kinetic model. The relative selectivity coefficient values of the imprinted adsorbent for Th(IV)/La(III), Th(IV)/Ce(III) and Th(IV)/U(VI) were 86.8, 92.3 and 56.3. The precision and detection limit of the proposed method with the obtained imprinted material as adsorbent was 1.9% and 0.57μg L-1, respectively, and it was applied to determination of thorium in environmental water samples with satisfactory results.
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