Lanthanides source

Apatite could eventually become an important lanthanide source. Marine apatites of biological origin are surprisingly enriched in lanthanides in view of the low lanthanide contents of seawater. Lanthanides liberated during commercial production of phosphoric acid could be recovered. Lanthanide concentrations in these apatites are low compared to those of currently used ores but... 

Igneous apatites could also serve as lanthanide sources byproduct lanthanides have been recovered from a vein-type occurrence of apatite in Finland. Many igneous apatite ores are mined for fertilizer in Brazil, South Africa, and the U.S.S.R., but in none of these operations are the lanthanides extracted. More than enough tonnage of lanthanides is presently being discarded during phosphate production than is needed to meet current world needs for those elements. 

Table 4. Lanthanide and Yttrium Distribution in Mineral Sources, wt %, ...

Apatite and other phosphorites constitute a substantial resource of rare earths. The REO content is highly variable and ranges from trace amounts to over 1%. Apatite- [1306-05-4] rich tailings of the iron ore at Mineville, New York, have been considered a potential source of yttrium and lanthanides. Rare-earth-rich apatites are found at the Kola Peninsula, Russia, and the Phalaborwa complex in South Africa. In spite of low REO content apatites could become an important source of rare earths because these are processed in large quantities for the manufacturing of fertilisers (qv). 

There are few principal lanthanide deposits, and there are no minerals that are sources for cerium alone. All the lighter lanthanides occur together in any potential deposit, and processes separating the lanthanides are necessary to obtain pure cerium products. 

Bastnasite has been identified in various locations on several continents. The largest recognized deposit occurs mixed with monazite and iron ores in a complex mineralization at Baiyunebo in Inner MongoHa, China. The mineral is obtained as a by-product of the iron ore mining. The other commercially viable bastnasite source is the Mountain Pass, California deposit where the average Ln oxide content of the ore is ca 9%. This U.S. deposit is the only resource in the world that is minded solely for its content of cerium and other lanthanides. 

The yearly worldwide production of lanthanides is nearly 70,000 tons (18) measured as contained Ln oxide. The primary sources are given in Table 2. For finished products the principal supplying companies are Molycorp (United States), Rhc ne-Poulenc (France), several Japanese companies, such as Mitsubishi, Santoku, and Shinetsu, and some Chinese organi2ations. The rise of Chinese lanthanide production during the 1980s has become a significant factor in the global market picture. 

The purity of the cerium-containing materials depends on the appHcation as indicated in Table 3, and purity can mean not only percentage of cerium content but also absence of unwanted components. For some uses, eg, gasoline production catalysts, the lanthanides are often used in the natural-ratio without separation and source Hterature for these appHcations often does not explicitly mention cerium. Conversely, particulady in ferrous metallurgy, cerium is often assumed to be synonymous with rare-earth or lanthanide and these terms are used somewhat interchangeably. 

K. A. Gschneider Jr. and L. Eyring (eds.). Handbook on the Physics and Chemistry of Rare Earths, North-Holland, Amsterdam. fel. 1, (1978) to Vol. 21, (1995). An authoritative source of information on all topics associated with lanthanide elements. 

Di-rerr-butylsodium pyrrolate serves as a source of the complexes of lanthanides [93CB2657 95JOM(495)C12]. Thus, with cyclooctadienyl chlorides of samarium, thulium, and lutetium, it affords species 89 [96JOM(507)287]. The N-coordinated samarium(II) calix-pyrrole complex is known [99AG(E)1432]. 

Catalytic asymmetric aza-Diels-Alder reactions using a chiral lanthanide Lewis acid. Enantioselective synthesis of tetrahydroquinoline derivatives using a catalytic amount of a chiral source [98]... 

Nitridoborates of lanthanum and the lanthanides were obtained from reactions of lanthanide metal or lanthanide metal nitride with layer-like (a-)BN at elevated temperatures (3>1200°C). These reactions require elaborated techniques in the inert gas sample-handling and the use of efficient heating sources, such as induction heating. Only some compounds remain stable in this high-temperature segment, and the yields of such reactions are often limited due to the competing stability of binary phases, allowing only the most (thermodynamically) stable compounds to exist. 

As mentioned several times Lewis acids are highly valuable catalysts but the most commonly used ones such as aluminium chloride and boron trifluoride are highly water sensitive and are not usually recovered at the end of a reaction, leading to a significant source of waste. In recent years there has been much research interest in lanthanide triflates (trifluoro-methanesulfonates) as water stable, recyclable Lewis acid catalysts. This unusual water stability opens up the possibility for either carrying out reactions in water or using water to extract and recover the catalyst from the reaction medium. 

Scheme 10.17 illustrates allylation by reaction of radical intermediates with allyl stannanes. The first entry uses a carbohydrate-derived xanthate as the radical source. The addition in this case is highly stereoselective because the shape of the bicyclic ring system provides a steric bias. In Entry 2, a primary phenylthiocar-bonate ester is used as the radical source. In Entry 3, the allyl group is introduced at a rather congested carbon. The reaction is completely stereoselective, presumably because of steric features of the tricyclic system. In Entry 4, a primary selenide serves as the radical source. Entry 5 involves a tandem alkylation-allylation with triethylboron generating the ethyl radical that initiates the reaction. This reaction was done in the presence of a Lewis acid, but lanthanide salts also give good results. 

The only lanthanide of which there is no stable isotope — they all decompose with half-lives between 2.6 and 17.7 years. Strong beta-emitters that are used industrially as thickness gauges. Also suitable as an additive for fluorescent materials. Produced artificially in kg amounts and serves as an energy provider for satellites in radionucleide batteries. Tiny batteries are long-term energy sources for pacemakers. 

If the excess of lanthanide is sufficiently great, overloading of the transport system occurs and colloidal aggregates of large size are formed by hydrolysis. The interstitial or intracavitary formation of immobilized lanthanide colloids labeled with relatively short-lived radioisotopes was the basis for the attempted use of radioactive lanthanides as internal sources of therapeutic radiation (Kyker, 1962a, 1962b). 

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