| Rare earth elements(REEs)are widely used in superconducting,aerospace,electronic products,chemical sensors,catalysis,fertilizer and other fields because of their unique electronic layer structure,spectral characteristics,more coordination number,and several excellent optical,electrical,magnetic,and thermal properties.With the consumption of rare earth resources and the pollution caused in the mining and application process,the separation and enrichment technology of rare earth resources has been kinds of important applications in the recycling,analysis and detection of rare earth resources.Therefore,many researchers devoted theirselves to develop and reseach the above technology.In this thesis,the functional ligand N,N-dioctyl diglycolic acid(DODGA)was synthesized from diglycolic acid.The solid phase extraction(SPE)materials modified by DODGA were prepared by chosing the amidation coel-shell Fe3O4@SiO2,the chromatography silica gel and the chromatographic silica gel as supporting materials.SEM,TEM,BET,FTIR,TG,XPS and other instrumental methods were used to characterize the morphology and the modification amount of the ligand on the SPE materials.Isothermal adsorption experiment and adsorption kinetic experiment were taken to investigate the adsorption process of SPE materials.Three different SPE materials were respectively applied to the enrichment of REEs,column chromatography separation and chromatographic analysis.The main research contents include the following aspects:(1)The amide podands ligand DODGA was designed and synthesized.The extraction performance of DODGA on 16 REEs was studied through liquid-liquid extraction experiment.The chemical structure of DODGA was identified by NMR,MS and IR.The effects of different kinds of inorganic acids,ligand concentration,extraction temperature and interfering ions on extraction capability of DODGA were investigated.Experimental results showed that DODGA had the best extraction performance in 1mol·L-1 HNO3,and the extraction ratio of 16 REEs could reach more than 90%.The coordination number of La,Ce,Pr,Nd with DODGA was 2,and the coordination number of other 12 REEs was 3.By changing the concentration of KNO3 and determining the change of the distribution ratio,the coordination number of La,Ce,Pr,Nd with nitrate ion is 1,and that of other 12 REEs is 2.The computational chemical results showed that DODGA forms complexes with REEs ions as a spontaneous process,and with the interfering ions as a non-spontaneous process.DODGA was prefer to form complexes with REEs to achieve selective extraction.(2)Magnetic mesoporous nanoparticles Fe3O4@mSiO2-DODGA were successfully prepared by using super-paramagnetic ferric oxide nanoparticles as SPE supporting materials,and were applied to the enrichment of REEs.Fe3O4@mSiO2-DODGA exhibited homogeneous spherical morphology,with mesoporous structure in the surface layer.The ligand DODGA was successfully modified to the surface of nanoparticles with the content of 367 mol·g-1.When the concentration of HNO3 was 2 mol·L-1,the adsorption ratio of Fe3O4@mSiO2-DODGA on 16 REEs reached the maximum.With 0.01 mol·L-1 EDTA as the eluent,16 REEs could be completely desorbed.In the solution with a concentration of 2 mol·L-1 HNO3,the Fe3O4@mSiO2-DODGA nanoparticles exhibited good stability.After repeated usage for 5 times,their initial adsorption capacity remained 88.25?92.63%,with no significant decrease in the adsorption ratio.Fe3O4@mSiO2-DODGA nanoparticles have also shown excellent resistance to co-existing interfering ions and could selectively adsorb REEs in complex samples.The adsorption kinetic data fitting was consistent with the quasi-second-order model.The adsorption isotherm data was consistent with the Langmuir isotherm model,indicating that the adsorption process of Fe3O4@mSiO2-DODGA nanoparticles to REEs was a single layer adsorption on the uniform surface,which was controlled by chemical adsorption and also physical diffusion.(3)Column chromatographic silica gel was selected as the solid phase support material to successfully prepare SG@DODGA to fill the chromatographic column,which was applied to separate 16 REEs and realize the baseline separation of La,Ce,Pr and Nd.Characterization showed that the ligand binding amout in SG@DODGA was approximately 322 mol·g-1.Adsorption kinetics showed that SG@DODGA could achieve full adsorption of REEs with amount of 126.33 mg·g-1 within 100 min.The adsorption kinetics of SG@DODGA for 16 REEs was attributed to the quasi-second-order kinetic model.The adsorption isotherm was fitted with the Freundlich isotherm model.The adsorption process was a single layer chemical adsorption on heterogeneous surfaces.The adsorption thermodynamics data showed that the value of the ?G° was negative,the ?H°and?S°was positive.The adsorption process is endothermic,spontaneous,and entropy increase process.The temperature rise is conducive to the adsorption process.SG@DODGA as stationary phase of the column chromatography loaded in the column to separate 16 kinds of REEs,obtain the breakthrough curve.The column capacity of chromatography column to various REEs is not obvious.The primary separation of 16 REEs could be realized by using subsection washing method.The baseline separation of La,Ce,Pr and Nd could be realized by increasing column length.(4)Take commercial silicon HP@Amino as solid phase supporting material to prepare silica particles HP@DODGA and fill high performance liquid chromatography column that can be used to separate REEs and establish analysis method.The modified DODGA ligands are approximately 219 mol·g-1.The full adsorption of REEs could be achieved within 90 min,with the adsorption amount up to 106.12 mg·g-1.The adsorption kinetic data of HP@DODGA for 16 REEs were consistent with the quasi-second-order kinetic model.The adsorption isotherm number was consistent with the Langmuir isotherm model.The adsorption process was a single layer chemical adsorption on the homogeneous surface.HP@DODGA silica gel particles were used to fill the HPLC column(ID 4.6mm×25 mm,10 ?m).The Arsenazo III was used as the post derivative to establish the HPLC separation system.The gradient elution conditions and mobile phase of 2-hydroxyisobutylic acid(HIBA)aqueous solution with a concentration of 50 mM?150 mM and methanol were investigated.A liquid chromatography method for the analysis of 15 REEs was established.Within the range of 10?250 mg·L-1,the coefficient linearity index is more than 0.9,and the recovery is from 85.7%to 96.7%.It has been applied to the quantitative analysis of REEs in real... |
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