Ceria(CeO_(2))nanoparticles were successfully synthesized via a simple complex-precipitation route that employs cerium chloride as cerium source and citric acid as precipitant.The elemental analysis results of carbon,hydrogen,oxygen,and cerium in the precursors were calculated,and the results revealed that the precursors were composed of Ce(OH)_(3),Ce(H_(2)Cit)_(3),or CeCit.X-ray diffraction analysis showed that all ceria nanoparticles had a face-centered cubic structure.With the molar ratio of citric acid to Ce^(3)+(n)of 0.25 and pH of 5.5,the specific surface area of the sample reached the maximum value of 83.17 m^(2)/g.Ceria nanoparticles were observed by scanning electron microscopy.Selected area electron diffraction patterns of several samples were obtained by transmission electron microscopy,and the crystal plane spacing of each low-exponent crystal plane was calculated.The ultraviolet(UV)–visible transmittance curve showed that ceria can absorb UV light and pass through visible light.Among all samples,the minimum average transmittance of ultraviolet radiation a(UVA)was 4.42%,and that of ultraviolet radiation b(UVB)was 1.56%.
Emulsification troubled normal extraction process of rare earths due to the existence of non-rare earth impurities, especially Si, Al and Fe. Against this background, the effect of emulsification caused by Si, Al and Fe on the La extraction with saponification P507 （2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester） in chloride medium was systematically investigated. A series of experiments were carried out to study the relationship of the extraction capacity of La and the concentration of impurities. ZPM-203 polarizing microscope was applied to investigate the morphology of emulsification, and the cation exchange extraction mechanism of Fe and Al as well as La was clarified by IR spectra. The results showed that a low concentration of Si in organic phase would aggravate the emulsification with Al, and the formation of ME （micro emulsion） and club-shaped polymer would result in emulsification in the extraction of mixtures of Si and Al, single Fe, respectively. Furthermore, the accumulation of impurity such as Si, Al and Fe in the organic phase would severely reduce the extraction capacity of La simultaneously.
