Preparation And Studies On Adsorption Properties Of Th(iv) Ion Imprinted Polymers

Thorium, which is an important radioactive element widely distributed over the earth's crust, can provide supplement to the insuffieient uranium resources effectively in the future, so it has broad prospects for nuclear power. However, thorium not only has chemical toxicity like other heavy metals do, but aslo is hazardous causing many environmental problems. Therefore, the development of the reliable methods for the determination and recovery of thorium in environmental and geological samples is of a particular significance. Direct determination of thorium is still difficult, owing to thorium's trace concentration in nature and presence of interferential matrix. At present, one of the methods, to solve the problem, is using a sample pretreatment teehnique including separation and preconcentration. Solid-phase extraction(SPE) is today the most popular method of the sample preparation. Unfortunately, the common materials of SPE are usually having poor selectivity for separation of coexistent metal ions, which can be solved by ion-imprinting technique. An especially appealing feature of the imprinted polymers is their potential to have the affinity and selectivity analogous to antibodies, while retaining several benefits including stability in harsh environments such as high temperatures and pressures. A particularly promising application of ion-imprinted polymers is the SPE preconcentration of analytes present in trace amouts and the separation from other coexisting species or complex matrix, which may lead to selective environmental clean up of analytes, not achievable by the conventional methods. Thereby, this work is focused on the preparation of Th(IV) ion imprinted polymers and the research of the properties of SPE. This dissertation consists of three parts, as follows:1. A brief overview is given for the profile and the methods of separation and preconcentration of Th(IV), the principle of Molecular(Ion) Imprinting Iechnology, the preparation of Molecular(Ion) Imprinted Polymers, and the studies in the rapidly developing and exciting area of IIPs-SPE.2. A new pyrazole derivative 1-phenyl-3-methylthio-4-cyano-5-acrylicacid- carbamoyl-pyrazole(PMTCAACP) was synthesized and chosen as a complexing monomer for the preparation of surface-grafted ion-imprinted polymers for selective solid phase extraction of thorium(IV). Polymerizable double bond was introduced to silica gel surface by amidation reaction between NH2 and maleic anhydride. The experimental conditions, kinetics, thermodynamics, and mechanism for the adsorption of Th(IV) on the imprinted polymers were investigated in detail. The obtained ion-imprinted particles for Th(IV) showed excellent selectivity and high affinity. The maximum static and dynamic adsorption capacity of the ion-imprinted polymers (IIPs) for Th(IV) was 64.8 and 37.4 mg/g, respectively. The relative selectivity coefficient values of the imprinted adsorbent for Th(IV)/U(VI), Th(IV)/Ce(III), Th(IV)/La(III), and Th(IV)/Zr(IV) were 72.9, 89.6, 93.8, and 137.2 times greater than non-imprinted matrix, respectively. The enhancement factor of 20.2, the detection limit of 0.43μg/L, and the precision of 2.47% (n=7) of the method under the optimized conditions were obtained. The prepared IIPs were shown to be promising for solid phase extraction coupled with UV-Vis spectrophotometry for determination of trace Th(IV) in real samples.3. A novel ion-imprinted adsorbent for selective preconcentration of thorium(IV) based on a surface of silica gel was prepared by a surface-grafted technique with methacrylic acid(MAA) as a functional monomer. The property of separation and preconcentration for Th(IV) onto the imprinted polymers was investigated. The obtained imprinted particles for Th(IV) exhibited specific recognition and relatively rapid kinetic process. The maximum static and dynamic adsorption capacity of the ion-imprinted polymers (IIPs) for Th(IV) was 33.2 and 17.3 mg/g, respectively. The relative selectivity coefficients of the imprinted polymers for Th(IV)/U(VI), Th(IV)/Ce(III), Th(IV)/La(III), and Th(IV)/Zr(IV) were 58.8, 107, 106.4, and 151.7, respectively. With a series of samples loading flow rate of 3 mL/min for preconcentration, an enrichment factor of 14.6 and the detection limit of 0.59μg/L were obtained. The relative standard deviation of the method under optimum conditions was 2.1% (n=7). The prepared IIPs were shown to be promising for solid phase extraction coupled with UV-Vis spectrophotometry for determination of trace Th(IV) in real water samples.