High-resolution XAFS Method At SSRf BL14W1Beamline And Its Application

Since the appearance of the synchrotron radiation, synchrotron radiation techniquesare becoming important experimental techniques of scientific researches gradually.XAFS technique is one of the most important synchrotron radiation techniques andhas been developed rapidly. New experimental techniques, such as QXAFS, GIXAFSand so on, have emerged. The development of new methods of XAFS technique isimportant for scientific researches.XAFS beamline (BL14W1) at Shanghai Synchrotron Radiation Facility (SSRF) is ageneral purpose XAFS beamline. It is mainly used for XAFS tests. Now XAFSbeamline have a variety of testing methods for XAFS, such as transmission mode,lytle fluorescence mode，SDD detector mode etc.. The development of high-resolutionXAFS method can not only expand the experimental techniques of beamline, but alsosolve some questions that conventional XAFS methods cannot solve.The high-resolution XAFS spectrometer is composed of a spherically curvedsilicon crystal, a detector and a sample. The analyzing plane is horizontal. The bentcrystal, the sample and the detector are located on the Rowland circle. It is used tostudy the spectrum from the electronic transitions. Generally it is mainly used toobtain the Kβ1,3and its satellite spectrum. The obtainment of these spectra can beachieved by using high energy resolution method. Generally speaking, the energyresolution of conventional XAFS method is not more than120eV. It is difficult (evenimpossible) to distinguish these spectra. But these spectra contain important structuralinformation such as spin state and orbit coupling. We can get some information thatconventional XAFS method cannot obtain through high-resolution emission spectraand absorption spectra.The first part of this thesis discussed high-resolution XAFS method at Bl14W1beamline. High-resolution XES and XAFS spectra were obtained. The following isthe main content of this part:1. Design of high-resolution XAFS method at BL14W1beamline;2. Introduction of hardware of high-resolution XAFS spectrometer;3. Introduction of software of high-resolution XAFS spectrometer. It is based on theexisting software Labview; 4. Installation and test of high-resolution XAFS spectrometer. Test of theperformance of the spectrometer through the emission spectra of Mn compounds;5. Optimization of the resolution and signal-to-noise ratio for high-resolutionXAFS method.The resolution of the emission spectrum about3eV can be obtained through theoptimization. The testing results indicated that high-resolution XAFS method hadbeen achieved at BL14W1beamline in SSRF. It reached the international level ofsimilar instruments.The second part of this thesis discussed the high-resolution XAFS method appliedto the field of environment. Mechanism and microstructure of Eu(III) interaction withγ-MnOOH by a combination of batch and high resolution EXAFS. In the context ofsafety of nuclear waste repositories and for the assessment of radionuclide fate andmobility in the natural environment, understanding of the interaction mechanism andmicrostructure of radionuclides at the interface is of great importance to assess theinterfacial behavior of radionuclides in the natural environment. The chemicalproperty of Eu(III) is very similar to other lanthanides and actinides, thus we canunderstand other lanthanides and actinides interfacial behavior through Eu(III). Thework is listed in the following part:Preparation and characterization of chemicals was carried out. The results showedthat the prepared solution of Eu and γ-MnOOH met experimental requirements.Adsorption experiments about Eu(III) interaction with γ-MnOOH. The resultsindicated that Eu(III) interaction with γ-MnOOH by sorption process was mainly dueto inner-sphere surface complexation.XAFS investigation of interaction mechanism and microstructure about Eu(III)interaction with γ-MnOOH through high-resolution XAFS method. This result wasconsistent with the macroscopic adsorption results.In this experiment, the fluorescence peak Lα of Eu(III) and Mn which is difficult tobe discriminated using conventional XAFS technique was discriminated. It formedthe basis of the studies on such complex systems.The utility of high-resolution EXAFS technique has been well-demonstrated in thepresent study. The results of this work are important to understand thephysicochemical behavior of the interested radionuclides in the natural environment.