Uranium molybdate

Uranium Molybdates.—Uranyl nioh bdate, UO2M0O4, is obtained as a white amorphous precipitate when ammonium molybdate is added to uranyl nitrate solution in the dark. It is reduced to uranous molybdate. U(Mo04)2, becoming green by the action of ethyl or methyl alcohol or acetic acid, and dissolves in mineral acids with a yellovush-... 

The U-Mo-0 binaiy oxide system was first studied by Kovba and Trunov [14,15]. These authors reported existence of several U-Mo oxocompounds with different stoichiometries U2M0O8, UM0O5, UM02O8, UM07O22, and UM011O35. Later stractural studies demonstrated that, in their structures, either U or Mo coordination polyhedra polymerize to form extended stractural units and these compounds should be considered as complex oxides rather than uranium molybdate salts. Similar stractural features have also been observed for complex oxides in the U-W-0 and U-Mo-W-0 systems [16-21]. 

Moluranite is another uranium molybdate with at least some reduced uranium.It is also very dark in colour, showing brown only in very thin fragments. It shows no X-ray pattern and appears to be amorphous or possibly metamict. It occurs in fine fissures in granulated albitite associated with molybdenite and other sulphides, brannerite and other U-Mo compounds. It is only known from one locality. 

Rupnitskaya L. S. Calcium uranium molybdate, Ca(U02)3 (Mo04)3(OH)2-8H20. Reference 11, 286. 

For the extraction of Tc from molybdemun irradiated by neutrons or separated from uranium fission products, inorganic sorbents, especially aliuninum oxide have widely been applied. In preparing a Tc generator from irradiated molybdenum , MoOj is dissolved in cone, nitric acid, the solution is diluted and passed through an aluminum oxide column. The column is then eluted by 0.2 N H2SO4 to extract Tc. If molybdenum is adsorbed by AljOj as molybdatophos-phate instead of molybdate, the exchange capacity of molybdenum increases from... 

In the 1960s, a number of binary oxides, including molybdenum, tellurium, and antimony, were found to be active for the reactions and some of them were actually used in commercial reactors. Typical commercial catalysts are Fe-Sb-O by Nitto Chemical Ind. Co. (62 -64) and U-Sb-O by SOHIO (65-67), and the former is still industrially used for the ammoxidation of propylene after repeated improvements. Several investigations were reported for the iron-antimony (68-72) and antimony-uranium oxide catalysts (73-75), but more investigations were directed at the bismuth molybdate catalysts. The accumulated investigations for these simple binary oxide catalysts are summarized in the preceding reviews (5-8). 

Asphaltic Sandstone from Lodeve-Mas Alary, Herault, France. This rock of Permian age contains, together with uraninite, secondary uranium minerals, sulfides, molybdates, etc. (12, 15) (Figure 3). 

Molybdenum can also be recovered economically from some uranium leach liquors, particularly those of the USA. When uranium is stripped from amine extractants by solutions of sodium chloride, any molybdenum present remains in the organic phase, and can be subsequently recovered by being stripped into a solution of sodium carbonate. A process has been operated in which the strip liquor is acidified to a pH value of 4.5 and the molybdenum is reextracted into a solution of quaternary amine chloride in kerosene.218 The extracted metal is stripped into a solution containing sodium hydroxide and sodium chloride to produce liquors containing 30-40 g of molybdenum per litre, from which calcium molybdate can be precipitated by the addition of calcium chloride. 

Shortly after the introduction of the bismuth molybdate catalysts, SOHIO developed and commercialized an even more selective catalyst, the uranium antimonate system (4). At about the same time, Distillers Company, Ltd. developed an oxidation catalyst which was a combination of tin and antimony oxides (5). These earlier catalyst systems have essentially been replaced on a commercial scale by multicomponent catalysts which were introduced in 1970 by SOHIO. As their name implies, these catalysts contain a number of elements, the most commonly reported being nickel, cobalt, iron, bismuth, molybdenum, potassium, manganese, and silica (6-8). 

In comparison to the bismuth molybdate and cuprous oxide catalyst systems, data on other catalyst systems are much more sparse. However, by the use of similar labeling techniques, the allylic species has been identified as an intermediate in the selective oxidation of propylene over uranium antimonate catalysts (20), tin oxide-antimony oxide catalysts (21), and supported rhodium, ruthenium (22), and gold (23) catalysts. A direct observation of the allylic species has been made on zinc oxide by means of infrared spectroscopy (24-26). In this system, however, only adsorbed acrolein is detected because the temperature cannot be raised sufficiently to cause desorption of acrolein without initiating reactions which yield primarily oxides of carbon and water. 

Christie et al. (45) and Pendleton and Taylor (46) have recently reported the results of propylene oxidation over bismuth molybdate and mixed oxides of tin and antimony and of uranium and antimony in the presence of gas-phase oxygen-18. Their work indicated that for each catalyst, the lattice was the only direct source of the oxygen in acrolein and that lattice and/or gas-phase oxygen is used in carbon dioxide formation. The oxygen anion mobility appeared to be greater in the bismuth molybdate catalyst than in the other two. 

Molybdenum and its uses. Molybdenite, molybdenum trioxide, ammonium molybdate. Wolfram (tungsten) and its uses. Scheelite, CaWO, and wolframite, (Fe,Mn)W04. Wolfram carbide. Uranium and its ores pitchblende, car-notite. Sodium diuranate, uranyl nitrate. Nuclear fission. 

The frequent occurrence of vanadium in uranium minerals renders the separation of these two metals of importance. One method in use is based on the solubility of uranyl nitrate in ether, %vhilst vanadic and also molybdic and tungstic acids are insoluble. A solution containing these substances may therefore be evaporated to drjmess, and the uranyl salt extracted from the residue with ether. Another method depends upon the fact that uranyl nitrate is readily soluble, whilst vanadium compounds are insoluble, in acetic acid of 95 per cent, strength to which nitric acid has been added in the proportion 1 20. ... 

FsMoOK , Molybdate(V), pentafluorooxo-, dipotassium, 21 170 F5LI, Uranium(V) fluoride, -, 21 163 FeAgAs, Arsenate, hexafluoro-, silver, 24 74... 

GA. Without additional anions or H2O 7.GB. With additional anions and/or H2O 7.H Uranium and uranyl molybdates and wolframates 7.HA.With 7.HB.With... 

In nitric acid solution containing uranium, plutonium, zirconium, molybdenum and other fission products, precipitation of zirconium molybdate occurs preferentially. Solutions containing only zirconium and molybdenum yield the "same" precipitated mater-... 

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