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Syntheses of Novel Chelating Resins with N and S Atoms and Their Application in Analysis of Rare Earth Metalals in Astragalus

Author: MengZuo
Tutor: XiongChunHua
School: Zhejiang Technology and Business University
Course: Of Food Science
Keywords: Chelating resin Rare earth metal Synthesis Adsorption Separation Detection
CLC: TS207.5
Type: Master's thesis
Year: 2010
Downloads: 77
Quote: 0
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Abstract


In China, with a large number of applications of agricultural rare earth, rare earth metal accumulation in vegetative foods has cause a major issue of safety. Therefore, detection methods of rare earth content in food are more and more concerned. As difficult separation, serious matrix interference effects as well as limited samples use in detection of rare earth metals, although many instrument analysis methods possess high sensitivity and selectivity such as ICP-OES and ICP-AES, still a need for sample pre-concentration to achieve the instrument detection limit. At present, owning to national standard spectrophotometry in the higher detection limit of rare earth and only detection the total amount of rare earth, samples must be separation and preconcentration to improve the time effectiveness, sensitivity and specificity of the spectrophotometry. In view of this, the combination of chelating resin preconcentration with the above two kinds of detection methods (viz. spectrophotometry and ICP-OES method) are applied and compared in determination of rare earth content of the samples. It not only can widen the spectrophotometric application field, but also provide a basis for the further development of national standards detection.In this paper, research on chelating resins and these adsorption to reare earth metals were reviewed, and the preparation of a series of crosslinked polystyrene matrix resins as well as these adsorption performance which were studied by researchers were enumerated. Aim at separation and preconcentration of metals, five kinds of resin were synthesized by anchoring heterocyclic into crosslinked polystyrene. The adsorption behaviors to rare earth ions were studied by static and dynamic adsorption. Subsequently, two methods of determination of cerium ion by spectrophotometry and ICP-OES are proposed and compared for using chelating resins in preconcentration and separation in astragalus.1. In this thesis, five novel chelating resins were synthesized by chloromethylated polystyrene beads as matrix, functionalized with heterocyclic ligands. The nitrogen in amide (-NH2) and sulphur in sulfhydryl (-SH) of ligands coordinated with matrix. Five kinds of chelating resins are divided into N-containing and S-containing based on the above coordination atom. The influences of various reaction conditions such as reaction solvent, reaction temperature and molar ratio of reagents on the quality of resins were studied. The N atom content of the resins, the functional group capacities and percentages of functional group conversation of the resins were determined by elemental analysis. The resin structures were confirmed by IR. The synthetic resins were on the thermal decomposition by TGA instrument to investigate the thermal stability, and verify their synthetic scheme.2. The adsorption properties of five resins for rare earth metals were systematically investigated by means of static and dynamic method. The experimental results with static method showed that both PAR and IAR with carbonyl group for Ce3+have excellent adsorption selectivity, maximum adsorption capacity is 107mg/g,87.3mg/g, respectively; 2-MPR containing mercapto-group for Nd3+, Pr3+, Ce3+have a good adsorption, the maximum adsorption capacity is 99.1mg/g,65.5mg/g, 56.7mg/g, respectively. Metal ions adsorbed on resins could be eluted completely by 4.0mol/L HC1. And resins had favorable repetitive property. Kinetics functions, thermodynamics functions and the adsorption isotherms in different temperature were studied. The results fitted for Langmuir and Freundlich equations. The adsorption process followed with second-order kinetics. The adsorption process was endothermic and chemical. From the study of dynamic adsorption, the dynamic saturated adsorption capacity of resins as follows:PAR for Ce3+, IAR for Ce3+, 2-MPR for Nd3+, Pr3+, Ce3+were 115mg/g,92.3mg/g,102mg/g,77.1mg/g, 60.2mg/g, respectively. Dynamic adsorption coincided with Thomas model.3. Two methods of determination of cerium by spectrophotometry and ICP-OES are proposed and compared for using chelating resins in preconcentration and separation in astragalus. Experimental results show that, through the chelating resin separation and enrichment, the data of above two methods are basically the same in the detection of cerium.

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CLC: > Industrial Technology > Light industry,handicrafts > Food Industry > General issues > Food standards and testing > Determination of food contamination
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