Abstract
For several years, IPEN/CNEN-SP has been working in the separation of the Rare Earth (RE) elements. A simple and economic procedure for the purification of technical grade cerium concentrate is described. The highly pure cerium dioxide is designed to be used as spectrochemical standard. It is obtained by association of the fractional precipitation technique, in the system RECl3/NH4OH/ Air/H2O2, to enrich the cerium up to 90% and then it is upgraded by ion exchange technique to 99.99% CeO2. The quality control warranty was accomplished by inductively coupled mass spectrometry (ICP-MS) and neutron activation analysis. The collected values for the accompanying Rare Earth elements in a CeO2 sample are the following (ppm): La(36), Pr(19), Nd(161), Sm(11), Eu(5.3), Gd(113), Tb(89), Dy(2), Ho(0.05), Er(1), Tm(<0.05), Yb(11), Lu(19) and Y(2.1), respectively. The purity of this cerium oxide is comparable to the international spectrographic standards.
Highlights
Making use of the gained experience in Rare Earth (RE) fractionation and in obtaining pure oxides, work is in progress to prepare some spectrochemically pure oxides to serve as standards
When contaminated with traces of praseodymium, for instance, the cerium oxide acquires a dark-yellow-orange color. This test was helpful during the fractionation by the elution of the Rare Earths from the resin
The authors describe in this paper a method successful for the purification of Rare Earths by ion exchanger chromatography without the use of a retaining ion
Summary
Researchers at IPEN/CNEN-SP have been working, for several years, with the individual separation of Rare Earth (RE) elements, aiming to assist, with the obtained products, an internal demand in other research areas.[1,2,3,4,5,6] Making use of the gained experience in Rare Earth (RE) fractionation and in obtaining pure oxides, work is in progress to prepare some spectrochemically pure oxides to serve as standards. Ltd. was the producer of mixed Rare Earth chlorides, the bulk of the production being exported. Cerium dioxide is getting more and more importance nowadays as an efficient component of polishing powder. Producer of polishing powder based upon the Rare Earth material, including cerium dioxide.[7,8] The use of cerium dioxide as promoter for nickel based catalysts for steam reforming of methane[9] and as oxygen storage component in automotive three-way catalysts has been studied.[9] The preparation of spectrochemically pure cerium oxide involves two steps. Starting from Rare Earth chloride mixtures, supplied by NUCLEMON, the cerium is separated using the NH OH/. Natural mixed Rare Earth chlorides, having the following composition and manufactured industrially from the Brazilian monazites, were supplied by NUCLEMON, São Paulo. Plasma power Cooling gas flow Auxiliary gas flow Nebulizer gas flow Nebulizer Spray Chamber Sample orifice, Pt Conical Skimmer orifice Resolution Points per peak Scan mode
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