Apatite uranium

Phosphorite Deposits. Sedimentary phosphorites contain low concentrations of uranium in fine-grained apatite. Uranium of this type is considered an unconventional resource. Significant examples of these uranium ore types include the U.S. deposits in Elorida, where uranium is recovered as a by-product, and the large deposits in North African and Middle Eastern countries (16). 

Apatite exploration takes place in various regions of the World, and the most known are Kola Peninsula (Russia) and northwest Africa (Morocco). In both places, the apatite ores contain not only phosphorus as a main element but also many heavy metals, which are toxic for humans and animals. The given elements are F, As, Y, some rare earth species, Sr, Pb, Cd, Sn. The underground waters in these regions are enriched by F, Fi, Nb, some rare earth species with alkaline reaction that facilitates the migration of many ore elements. Some phosphorus containing ores are radioactive owing to the mixtures of uranium and thorium. 

Carbonate-fluor-apatite accommodates large quantities of trace elements, mainly uranium, which are potential luminescence centers. It has been proposed that uranium may occur in phosphorites in the following forms as a separate uraninite phase as an adsorbed or structurally incorporated uranyl ion as a dominantly replacement for Ca +, to be structurally incorporated... 

It is interesting to note that in magmatic apatites the luminescence of uranium containing centers have not been discovered before or after oxidizing heating. Thus it is reasonable to suppose that uranium is present mainly in the 11" + form. The U with an ionic radius of 0.97 A may be located in the apatite structure instead of Ca with the ionic radius of 0.99 A. The most likely way for achieving the excess charge compensation is the Na" for Ca " structural substitutions. 

Our study of sedimentary apatite from Israel proved that laser-induced time-resolved luminescence is a perspective tool for evaluation of sedimentary phosphate ores with high dolomite content (Gaft et al. 1993b). The idea was based on the fact that natural apatite contains several characteristic luminescence centers, which enables us to differentiate it from dolomite. The most widespread characteristic luminescence center in sedimentary apatite is uranyl (U02) with a typical vibrational green band luminescence under nitrogen laser excitation (Fig. 8.13a,b). Nevertheless, it appears that such luminescence is absent in phosphate rock samples from Florida, evidently because of extremely low uranium concentration (Fig. 8.13c,d). hi order to find potential liuninescence centers, ICP-MS analyses of Florida phosphates was accompHshed. From discovered REE, theoretically Dy + is the best candidate... 

Laboratory batch and column studies to evaluate Apatite II removal of soluble uranium from contaminated groundwater. American Chemical Society National Meeting, American Chemical Society, Division of Environmental Chemistry, 41, 109-113. 

Apatite - [COAL] (Vol 6) - [COLORANTS FORCERAMICS] (Vol 6) - [FERTILIZERS] (Vol 10) -magnetic intensity [SEPARATION - MAGNETIC SEPARATION] (Vol 21) -uranium m [NUCLEAR REACTORS - NUCLEAR FUEL RESERVES] (Vol 17)... 

Residues from uranium mining operations in Canada have been a major source of yttrium. Xenotime (YPO4) found in Malaysia is another source, as well as the ion-adsorption clay minerals in China. Some apatite deposits are unusually rich in yttrium and it also is found in gadolimte, euxenite, and samarskite. 

Eujino O, Umetani S, Matsui M. 1994. Determination of uranium in apatite minerals by inductively coupled plasma atomic emission spectrometry after solvent extraction and separation with 3-phenyl-4-benzoyl-5-isoxazolone into diisobutyl ketone. Analytica Chimica Acta 296 63-68. 

The paradox of the spatial decoupling between isotopic contamination and LILE and LREE enrichment was resolved with a numerical simulation of isotopic variations during reactive porous flow (Bodinier et al., 2004). This confirmed that the isotopic contamination (e.g., " Nd/ " Nd) by the infiltrated melt is restricted to the domain between the melt source ( = dike) and the chromatographic front of the element (neodymium)—i.e., —20 cm from the dike in the studied wall rock. Numerical experiments also showed that the fractional solidification of infiltrated melt (due to amphibole cpx precipitation) accounts for the systematic increase in thorium, uranium, LREE, and P2O5, that reach a maximum in the distal apatite-bearing wall rock (>50 cm from the... 

A pervasive grain-boundary component that is selectively enriched in highly incompatible elements, contributing 25-90% of the whole-rock budget for barium, thorium, uranium, and 10-50% for niobium and LREE in apatite-free samples. 

Apatite dominates the budget of thorium, uranium, strontium, and LREE (25-75%), when present. 

Thorium and uranium contents of apatite vary widely but are normally very high compared to other mantle phases (generally >10 ppm Table 9 Ionov et al, 1997). Apatites in MARID xenoliths tend to have lower uranium (Kramers et al, 1983), possibly due to uranium partitioning into rutile or zircon. Lead contents are the highest reported for the common mantle minerals but U/Pb is generally PUM. 

Bingen B., Demaiffe D., and Hertogen J. (1996) Redistribution of rare earth elements, thorium, and uranium over accessory minerals in the course of amphibolite to granulite facies metamorphism the role of apatite and monazite in orthogneisses from southwestern Norway. Geochim. Cosmochim. Acta 60, 1341—1354. 

Accessory minerals commonly contain high concentrations of radioactive elements, and are a common target of radiogenic isotope measurements. Specific elements include uranium (zircon, apatite, titanite, monazite, xenotime, allanite) and thorium (monazite and allanite). Each accessory mineral is stabilized in a rock via a single element or suite of related elements, specifically phosphorous (apatite), REE (allanite, monazite, xenotime), zirconium (zircon), and titanium (titanite). Trace elements also occur in the major minerals (particularly phosphorous, zirconium, and titanium), so accessory minerals participate directly in major mineral reactions (Pyle and Spear, 1999, 2000, 2003 Ferry, 2000 Pyle et al, 2001 ... 

Uranium(VI) readily precipitates in the presence of phosphate to form a number of sparingly soluble U-phosphate phases (U phases, such as saleeite, meta-autunite, and autunite) and also is removed by sorption and co-precipitation in apatite. Several studies have shown that hydroxyapatite is extremely effective at removing heavy metals, uranium, and other radionuclides from solution (Gauglitz et al., 1992 Arey and Seaman, 1999). 

Apatite was shown to be effective at removing a number of metals including uranium at Fry Canyon, Utah (US EPA, 2000b). Krumhansl et al. (2002) reviews the sorptive properties of a number of other materials for backfills around nuclear waste repositories and permeable reactive barriers. 

Sedimentary phosphate ores, such as those found in Florida and Morocco, tend to have high concentrations of uranium, whereas the opposite occurs with magmatic ores, such as apatite from Kola. Typical activity concentrations of U are 1500 Bq kg in sedimentary phosphate deposits and 70 Bq kg in apatite. U is generally found in radioactive equilibrium with its decay products. The activity concentrations of Th... 

Fluorine content of apatite between 2,3.and 4.8% by weight. Some apatites contain uranium. 

The other components of apatite (iron, aluminum, uranium) partly pass into solution as salts and are partly precipitated with the calcium sulfate. Any carbonate present produces carbon dioxide during digestion. If sedimentary noncalcined apatite is utilized, the phosphoric acid obtained is colored black by the organic impurities. 

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