Application for the Quality Evaluation of Recovered Rare Metals/Rare earth elements

The recycling of "urban mines" has recently attracted attention. In industrial products such as household appliances, often discarded in large quantities in a big city, there actually exist scarce resources similar to the precious resources found in a mine; hence the term “urban mine”. The Hitachi polarized Zeeman atomic absorption spectrophotometer (AAS) is expected to play an active role in the field of urban mine recycling for the impurity analysis, etc., of a recovered rare metal.

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Did you know that the recycling of cellular phones is being promoted?

These days, the recovery, and recycling for effective use, of metals called "rare metals" found in the urban mine is attracting attention. Although the amount or use of rare metals is less than metals such as copper, zinc, aluminum, etc., rare metals are used in various products such as cars, compact music players, PCs, cell phone liquid crystal panels and rechargeable batteries, etc., depending on the characteristics of each metal. In Japan, this use maintains strong competiveness of the manufacturing industry. However, in many cases, these metals are unevenly distributed in certain countries and areas and can therefore be hard to obtain, and susceptible to the high risks of price fluctuation. In these situations, the stability of supply and establishment of recycling technology have long been expected.

	Thirty-one different kinds of metals designated as rare metals by the Ministry of Economy, Trade and Industry
	Ni Nickel ●  Ta Tantalum ●  Zr Zirconium ●  Bi Bismuth ●  Cr Chromium ●  Ge Germanium ●  Re Rhenium    In Indium ●  Mｎ Manganese ●  Sr Strontium ●  Li Lithium ●  Cs Caesium    Co Cobalt ●  Sb Antimony ●  B Boron ●  Rb Rubidium    W Tungsten ●  Pt、Pd Platinum ●  Ga Gallium ●  Tl Thallium ●  Mo Molybdenum ●  FeTiO3 Lumenyte    Ba Barium ●  Hf Hafnium ●  V Vanadium ●  TiO2 Rutile    Se Selenium ●    Nb Niobium ●  Be Beryllium ●  Te Tellurium ● rare earth elements Sc, Y, La●, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu
	● :A hollow cathode lamp (Reference used for measuring other rare metals as impurities in a rare metal)

	The Hitachi polarized Zeeman AAS can be used to analyze metal impurities in a rare metal in the increasingly attractive field of recycling.
	After refinement, a rare metal may accidentally get mixed in with residue and become hard to extract. Use of an electronic substrate in the recovery process may introduce many harmful substances, while on the other hand, the appropriate processing may be costly. Thus, while a recycling method has been discussed, the analysis of impure metal is also required for quality evaluation of the collected rare metal. There are many matrices to consider in the impurity analysis of a rare metal, and more than a few of the elements are hard to measure by ICP or ICP-MS. For the measurement of to approximately eight elements, an atomic absorption photometer may be more advantageous than ICP or ICP-MS for quality evaluation during impurity analysis, etc., of a collected rare metal, with respect to the following; (1) A robust matrix (2) A low introduction cost and running cost of the system (3) Easy pre-processing and use The Hitachi Z-2010 series polarized Zeeman AAS adopts the stability of the baseline seen with the "polarized Zeeman background correction method" and the "dual detection system" for frame analysis and graphite analysis, thereby attaining high sensitivity. For graphite furnace analysis, an easy-to-use XY stage autosampler supports automatic analysis.
	With the standard automatic QC measurement function, it is possible to automatically check items related to QC such as the calibration curve check and repeatability. When a sample concentration is high, the sample will be diluted automatically and remeasured. In addition, the clean cover provided as part of the standard equipment helps reduce outside contamination.

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	Analysis of Dy in Neodymium Magnet
	Dy is added to neodymium magnet used for high performance motors of hybrid cars to improve the high temperature properties. Dy is a rare metal and its use in the collection and recycling technology for waste household electric appliances so-called urban mines is drawing attention. In the ICP emission spectrometry, care should be taken for the spectral interferences by Fe, etc. Its absorption wavelength is difficult to be corrected by the D2 lamp correction atomic absorption method. However, by using the atomic absorption spectrometry with the polarized zeeman correction, it can be analyzed without spectral interferences.

[Preparation] One neodymium magnet (φ9 × 2 mm, approx. 0.93 g) was heated to dissolve in 10 mL of nitric acid and the volume was made up to 50 mL with purified water. The solution prepared as above was diluted to 1/5 for the measurement.

	Analysis of Co in Zirconium Oxide
	Zirconium oxide is a raw material for refractory materials, optical glasses, and white pigments. It is also used as a raw material for dye-sensitized wet solar cells and fuel cells, which are recently drawing attention. In the electrothermal atomic absorption method with the polarized zeeman correction, cobalt contained at a μg/L level in a solution highly concentrated with zirconium can be accurately analyzed without the interference by zirconium, the main component.

[Preparation] 0.50 g of the sample was placed in a fluoropolymer beaker. 2 mL of hydrofluoric acid was added and the mixture was heated to dissolve on a hot plate. After cooling, the volume was made to 50 mL with purified water. Pyrotube C HR cuvette was used.

Zirconium oxide can also be dissolved in sulfuric acid. However, the solution of hydrofluoric acid can be analyzed at a sensitivity 2 times higher compared with the solution of sulfuric acid. In addition, the analysis is more stable as the deterioration of the cuvette is less.