Rare earth metal specific

The secret that makes this process work is no surprise, the catalyst. Those that work include some of the noble metals, specifically, platinum or palladium, a rare earth metal like cerium or neodynium (are they rare or what ) on alumina, or a non-noble metal like chromium on a silica-aluminum support. 

Various processes separate rare earths from other metal salts. These processes also separate rare earths into specific subgroups. The methods are based on fractional precipitation, selective extraction by nonaqueous solvents, or selective ion exchange. Separation of individual rare earths is the most important step in recovery. Separation may be achieved by ion exchange and solvent extraction techniques. Also, ytterbium may be separated from a mixture of heavy rare earths by reduction with sodium amalgam. In this method, a buffered acidic solution of trivalent heavy rare earths is treated with molten sodium mercury alloy. Ybs+ is reduced and dissolved in the molten alloy. The alloy is treated with hydrochloric acid, after which ytterbium is extracted into the solution. The metal is precipitated as oxalate from solution. 

By contrast, the industrial user must view any raw material purchase in terms of its cost effectiveness and in the case of rare earth metals this frequently requires the adoption of low purity specifications. Therefore, in the context of the industrial applications to which reference will be made, the term pure will be taken to include all metals having a purity of not less than 95% - the balance being predominately other rare earths. But before considering the applications in detail it is perhaps of value to have some appreciation of the size of the market for these metals. 

In addition, there are certain metals involving 4f- or 5f-states, formerly called Kondo metals and now described as heavy-fermion materials, which have a very large electronic specific heat and may be described as crystals in which every rare-earth metal is envisaged, coherently, in a Kondo-type spin flip. 

However, a large number of complexing agents of all kinds with chemistries designed for specific metal ions have been reported in the literature. The tertiary amine Alamine 336 is widely used to transport anions such as U02(S04)4- and CfiOj [44-46], The macrocyclic crown ether family has also been used to transport alkali and rare earth metals [47,48] ... 

R,R rare earth metal Y electronic specific heat coefficient... 

Crystal field levels in rare earth metals have been determined by measurements of properties such as (i) specific heat, (ii) Van Vleck susceptibility, (iii) magnetization in high magnetic fields, (iv) paramagnetic resonance, (v) Mossbauer effect, (vi) inelastic neutron scattering and (vii) miscellaneous methods. 

Commercially available zeolite A and X from Zeolites and Allied Products Mumbai India was used as the starting material without any further purification. For exchanging with transition and rare earth metal ions, the zeolite was mixed with 0.1M aqueous solution of the specific cation and refluxed at 80 C for 4 hours. The zeolite was filtered and washed with distilled water until the washings were free from ions and used for the adsorption measurements after diying. The percentage of ion exchange was determined by Atomic Adsorption Spectroscopy after acid digesting the sample. 

To improve the solubility of metal ion, the commonly used method is including a metal ion-ligating functional group in structure of one of the ions named task-specific ionic liquids, which play dual role as hydrophobic solvent and as extractant. Visser et al. [191,192] presented new thiourea, urea, and thioether derivatives of ILs designed to extract heavy metal ions (e.g., Hg + and Cd ), and the same methods have been used to the extraction and separation of rare earth metals by Chen et al. [210,211]. 

Tml2, Dyh and Ndh have also been used in an acetonitrile/amine coupling reaction, which produced amidines of general formula MeC (=NH)NR R R R2 = H, Me H, iPr H, fBu Et2). The reaction is sub-stoichiometric in rare-earth diiodide but not really catalytic since part of the produced amidine remained tightly held aroimd the rare-earth metal it could be liberated by heating a trivalent intermediate formulated as Rl2(amidine)4(amidinate) (R = Nd, Dy, Tm) imder vacuum, and the residue could be recycled to produce more amidine. This reaction is not specific of the divalent iodides since many rare-earth triiodides were also effective. In the case of dysprosium and diethylamine, an intermediate trivalent amidine complex has been isolated and structurally characterised in the form of the zwitterionic [Dy MeC(=NH)NEt2 4][(I)3] (Bochkarev et al., 2007) (Figure 9). 

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