Rare earths, use

The tonnages of the rare earths used are, of course, a function of the vitality of the nodular iron industry. That future looks promising indeed. In 1959, production of nodular iron castings was less than 170 thousand tons (36). By 1978, over 2.9 million tons of nodular iron castings were produced (37). 

Overall, the total monetary volume of rare earths used for U.S. CRT phosphor manufacture is 20-25M. The volume by weight is only roughly 1% of total rare earth production, but the monetary volume is large because of the high value of Eu O.. and Y 0 compared to other rare earth oxides, and the high purity required of phosphor grade chemicals. 

Although the garnet compositions used in memories contain rare earths, the total rare earth use in magnetic films is not sufficient to make much impact on the rare earth market. The use of gadolinium oxide in substrate crystals is another matter. It has been estimated that by 1990 the annual use of Gd203 for GGG substrates will reach 40 metric tons, about twice the present rate (21). 

Methods were developed for the separation of Am and Cm using HPMBP-TOPO143, for the separation of the Am-Cm pair from rare earths using HTTA-TBP135, for the... 

Solvent extraction studies for the separation of rare earths using crown ethers are summarized in Table 3.9. 

In the mid-1960s liquid—liquid extraction processes were introduced and today all large-scale commercial production is done in this way. An aqueous solution of the Ln3+ ions is extracted in a continuous countercurrent process into a nonpolar organic liquid containing tri-n-butylphosphine oxide or bis(2-ethylhexyl)phosphinic acid (DEHPA). Typical separation factors for adjacent rare earths using DEHPA are 2.5 per extraction step so that under automatic multistep or countercurrent conditions purities of 99 to 99.9% are routinely achieved. 

For wet ashing of the dentin, transfer the weighed sample to a Kjeldahl flask and treat with 3 mL of 2 1 mixture of suprapure nitric acid (65% v/v) and perchloric acid (63% v/v). Digest slowly at a low heat initially and then raise the temperature to 180°C till a clear solution is obtained and the white fumes are given off. Cool and dilute the contents to volume with ultra-pure water. The solution can be used for determination of major, minor and trace elements including iron, lead, manganese, zinc, tin, barium, cadmium, copper, vanadium, strontium and the rare earths using F-AAS, F-AES, and ICP methods. 

Shimizu et al. (2005) studied the dissolution of rare earths using supercritical carbon dioxide containing TBP complexes with nitric acid and water. By diluting the TBP HN03 H20 complex with anhydrate TBP, they succeeded in preventing the generation of aqueous droplets accompanied by the dissolution of metal oxides. More than 99% of yttrium and europium were dissolved after static operation for 120 min at 15 MPa and 60 °C. 

Table 20.8 Cost and availability of rare earth used in SOFC...

These functions have been calculated from first principles by several authors [25, 26] for both the transition metals and the rare earths. Using these values and Eqs. (3.26) and (3.27) it is possible to calculate the paramagnetic contribution to the differential scattering cross section and remove it. 

The first successfiil ion-exchange separation of rare earths using 5% dtric add-ammonium citrate eluant at low pH carried out on either H -state or NHj-state resin beds was reported in a collection of nine sdentific papers in 1947 (Tompkins et al. 1947, Spedding et al. 1947a-c, Marinsky et al. 1947, Harris and Tompkins 1947, Ketelle and Boyd 1947, Boyd et al. 1947, Tompkins and Mayer 1947). This technique, however, was uneconomical for moderate- or large-scale rare earth separation. 

Donohue (1977) described the photochemical separation of Eu from other rare earths using a low pressure mercury lamp with no filter at 185nm and with a Vycor filter at 254 nm, and an ArF excimer laser operating at 193 nm. Equimolar mixtures (0.01 M) of binary or ternary lanthanide perchlorates and 0.05 M K2SO4 in 10% isopropanol were used in the experiments. The separation factors for the binary mixture Eu/Ln varied from 1 for Eu/Pr to > 200 for Eu/Tm. 

Numerous toxicity tests, including some using primates (see, e.g., Ji et al. 1988), have been reported and their results have firmly testified that REE is, within normal range, convincingly safe . A special issue of the Journal of the Chinese Rare Earth Society, published in September, 1985, reported thirteen experimental studies of REE toxicity, from which it was concluded (Ji 1985) that the possible harmful effect of trace rare earths used in agriculture on human health was almost non-existent . 

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