Study On Photo-catalytic Fluorescence For The Determination Of Trace Uranium In Water Environment And Application

This chapter introduces the hygiene significance and the research status of the methods for the determination of trace uranium in water environment at home and abroad.The basic concepts and principles for the molecularly imprinted polymer and dual cloud point extraction technology in sample preparation were introduced.And the basic principles and the quantitative analysis basis for the new photo-catalytic resonance fluorescence methods of health inspection for the determination of trace uranium were expounded.Chapter 2:In the chapter,two kinds of salophens（Sal）withdifferent solubilities,Sal1 and Sal2,have respectively been designed and synthesized,and they all can combine with uranyl to form stable“uranyl-salophens”complexes:U-Sal1 and U-Sal2.Among them,U-Sal1with hydrophobicity was used as ligand to extract uranium in complex samples by dual cloud point extraction（dCPE）,and U-Sal2 with hydrophilicity was used as photo-catalyst for the determination of uranium by photo-catalytic resonance fluorescence（RF）method.The photo-catalytic characteristic of U-Sal2 on the oxidized pyronine Y（PRY）by potassium bromate which leads to the decrease of RF intensity of PRY was studied.The reduced value of RF intensity of reaction system（ΔF）is in proportional to the concentration of uranium（c）,and a novel photo-catalytic RF method was developed for the determination of trace uranium（VI）after dCPE.The combination of photo-catalytic RF techniques and dCPE procedure endows the presented methods with enhanced sensitivity.Under optimal conditions,the linear calibration curves range for 0.224 to 2.4 ng mL^-1,the linear regression equation wasΔF=241.69 c(ng mL^-1)+239.05 with the correlation coefficient r=0.9956.The limit of detection was 0.066 ng mL^-1.The proposed method was successfully applied for the determination of uranium in samples with the recover of 96.8¹03.5%.Chapter 3:A novel core（Fe₃O₄）-shell（SiO₂）magnetic nano-particle with surface uranyl molecularly imprinted polymer coating was prepared via a sol-gel process.Firstly,the UO₂²⁺-salophens complexes（U-Sal）was synthesized,which was used as a template.Then,tetraethyl orthosilicate was used as the cross-linker and 3-aminoprophyltriet-hoxysilane as functional monomter,and the resulted molecularly imprinted polymer film was coated on the surface of nano Fe₃O₄@SiO₂particals in presence of template molecular(UO₂²⁺-salophens).A kind of magnetic core shell nanoparticle surface uranyl molecular imprinted polymer particles has been synthesized,which would be used for selectivly solid phase extraction of trace uranium in complex samples.The magnetic uranyl molecular imprinted polymer（MUMIP）was characterized by Fourier transform infrared spectroscopy,scanning electron microscopy and X-ray diffraction.The uranyl could be removed from the imprinted polymer by acid leaching.The adsorption propertties of UMIP for uranyl were evaluated by the equilibrium-adsorption method.And the optimum adsorption experimental conditions were studied.The results showed that UMIP has high adsorption capacity for uranyl and could be repeatedly used.Chapter 4:A new heterogeneous photo-catalytic resonance fluorescence method with the system of RhG-KIO₄-H₃PO₄-UMIP was established based on that the uranium in the sample solution can be adsorbed and enriched by magnetic uranyl molecularly imprinted polymer particles（UMIP）.Under certain conditions,UMIP can be used to quantitatively adsorb and separate uranyl ions from solution.And on its surface,the[UO₂²⁺-Sal]complexes with special structures would be formed,which shows strong photo-catalytic activity.The oxidation of RhG by potassium periodate could be accelerated by the photo-catalysis of the UMIP particles adsorbed uranium,which results in the resonance fluorescence decreased significantly.The resonance fluorescence changeΔF increases with the increases of uranium concentration,which shows the concentration of uranium can be measured.Found that under optimal conditions,the maximum wavelength of the resonance fluorescence was at 537nm,and there was a good linear relationship bestow the change values of the resonance fluorescence intensity（ΔF）and the uranium concentration around the scope of 0.4⁸.0μg·L^-1,the regression equations of the standard curye wasΔF=495.03(μg·L^-1)-492.78,r=0.9955.New method for easy,equipment simple and little pollution,detection limits were lowered,applies to the determination of uranium in water samples.