Extraction of Molybdenum

Between 40% and 50% of the roasted concentrate is converted to ferromolybdenum, either by means of an electric furnace or by a thermite process. The thermite process involves ignition of a mixture of the roasted concentrate with aluminium and an iron source (iron ore and ferrosilicon) together with a flux. The resulting ferromolybdenum contains between 55% and 70% of molybdenum, and is used in alloy steel and cast iron manufacture. Some of the roasted concentrate is converted to briquettes by pressing with a pitch binder. The briquettes, weighing about 5 kg., are also used in manufacture of alloy steels and cast irons. 

Purified molybdic oxide is produced by volatilisation in a stream of air in sand-hearth furnaces at about 1200°C. Molybdic oxide melts at 795°C, but its vapour pressure is very high, and the volatilisation process is sometimes referred to as sublimation rather than distillation. The product is a fine powder containing from 99.5% to 99.97% of molybdenum trioxide. 

Ammonium molybdate is manufactured by dissolving technical molybdic oxide in hot ammonia. It can be highly purified to over 99.9% purity, and 

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Under the conditions described above, the formation and extraction of molybdenum (IV) bromide proceed at the rate of ca. 0.086 g. hour-1 or 2.1 g. day-1. For example, 6.85 g. of the tribromide afforded 7.53 g. of tetrabromide after an extraction... 

Fujii, T., Yamana, H., Watanabe, M., Moriyama, H. 2001. Extraction of molybdenum from nitric acid by octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide. Solvent Extr. IonExch. 19 (1) 127-141. 

Y. Bal, K. E. Bal, G. Cote, and A. Lallam. Characterization of the solid third phases that precipitate from the organic solutions of aliquat (r) 336 after extraction of molybdenum)VI) and vanadium(V). Hydrometallurgy, 75(1-4) 123-134, 2004. 

Chelex-100 and Permutit S 1005 are also suitable for complete extraction of molybdenum from sea water. MoO2- is quantitatively removed from the resins by elution with 4 N ammonia 56>. 

Extraction. — The extraction of molybdenum salts from native ores may be accomplished in several ways, some of the methods which are in actual use bang secret. Naturally, the method selected will depend upon the kind of ore, the other metals present, and various other considerations. Some of the available methods are outlined as follows —... 

II. From wulfenite the extraction of molybdenum presents greater difficulties because of the larger number of metals present. This consideration and the facts that wulfenite has a small molybdenum content and is at the same time much more rare than molybdenite, have led to the prediction 3 that wulfenite will not become an important source of molybdenum. On the other hand the wulfenite has the advantage of containing other valuable metals, the recovery of which materially decreases the cost which must be assessed to the molybdenum. Previous to 1915 most of the American material was obtained from wulfenite, but fully 90 per cent of the present supply comes from molybdenite.4... 

Karimian, N., and Cox, F. R. (1978). Adsorption and extractability of molybdenum in relation to some chemical properties of soils. Soil Sci. 

Jackson, D. R., and Meglen, R. R. (1975). A procedure for extraction of molybdenum from soil with anion-exchange resin. Soil ScL Soc. Am. J. 39 373-4. 

Figure 146 Extraction of molybdenum as a function of pH. A the Mo-dithiol system B the Mo-8-hydroxyquinoline system (O) MIBK (D) DIBK (A) isoamyl alcohol. (Adapted from L. H. J. Lajunen and A. Kubin, Talanta, 1986, 33 265)...

Martynkovd, K. Komendova, R. Fisera, M. Sommer, L. Solid phase extraction of molybdenum on modified octadecyl silica sorbents in the presence of cationic surfactants and on silica-based anionic exchanger and its determination by... 

A similar trend was found concerning the extractability of molybdenum by ammonia solution [41]. Signals due to bulk M0O3 were neither detected in the X-ray diffractograms nor in the UV-Vis spectra of the impregnated faujasites [40,41,43]. Corma et al., by means of IR spectroscopy, observed an interaction of molybdenum species incorporated in USY with all hydroxyls except the external silanol groups [39]. Furthermore,they found similar nsi/n o ratios at the surface and in the bulk from which they concluded that molybdenum species (as depicted in Fig. 1) are well dispersed in the zeolite pore system. 

The extraction of titanium is still relatively costly first the dioxide Ti02 is converted to the tetrachloride TiCl4 by heating with carbon in a stream of chlorine the tetrachloride is a volatile liquid which can be rendered pure by fractional distillation. The next stage is costly the reduction of the tetrachloride to the metal, with magnesium. must be carried out in a molybdenum-coated iron crucible in an atmospheric of argon at about 1100 K ... 

The most important compound of Mo (TV) is molybdenum disulfide [1317-33-5] M0S2 (21). The layered stmcture of M0S2 is reflected in the flat plate-like hexagonal gray-black crystaUites found in natural and synthetic samples. The stmcture consists of pairs of close-packed layers of sulfur which are echpsed with respect to each other. The close-packed sulfur surfaces are naturally hydrophobic, which faciUtates the extraction of M0S2 ore by flotation. 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

Reclamation, Disposal, and Toxicity. Removal of poisons and inorganic deposits from used catalysts is typically difficult and usually uneconomical. Thus some catalysts are used without regeneration, although they may be processed to reclaim expensive metal components. Used precious metal catalysts, including automobile exhaust conversion catalysts, are treated (often by the suppHers) to extract the metals, and recovery efficiencies are high. Some spent hydroprocessing catalysts may be used as sources of molybdenum and other valuable metals. 

The above procedure may be adapted to the determination of molybdenum in steel. Dissolve a 1.00 g sample of the steel (accurately weighed) in 5 mL of 1 1 hydrochloric acid and 15 mL of 70 per cent perchloric acid. Heat the solution until dense fumes are evolved and then for 6-7 minutes longer. Cool, add 20 mL of water, and warm to dissolve all salts. Dilute the resulting cooled solution to volume in a 1 L flask. Pipette 10.0 mL of the diluted solution into a 50 mL separatory funnel, add 3 mL of the tin(II) chloride solution, and continue as detailed above. Measure the absorbance of the extract at 465 rnn with a spectrophotometer, and compare this value with that obtained with known amounts of molybdenum. Use the calibration curve prepared with equal amounts of iron and varying quantities of molybdenum. If preferred, a mixture of 3-methylbutanol and carbon tetrachloride, which is heavier than water, can be used as extractant. 

Toluene-3,4-dithiol, usually called dithioP, yields a slightly soluble, dark-green complex, (CH3.C6H3.S2)3Mo(VI), with molybdenum(VI) in a mineral acid medium, which can be extracted by organic solvents. The resulting green solution is used for the colorimetric determination of molybdenum. 

Add to the sample solution (containing 1 -25 g of Mo) 4 mL of 1 3 sulphuric acid, 3 drops of 85 per cent phosphoric(V) acid, and 0.5 g of citric acid. Dilute with water to 20 mL and add 2 mL of dithiol solution. Allow to stand at room temperature for 2 hours. Extract the molybdenum complex with 13 mL and 10 mL portions respectively of re-distilled butyl acetate, and make up to 25.0 mL with this solvent in a graduated flask filter through glass wool if not entirely clear. Determine the absorbance of the solution at 670 nm. Prepare a calibration curve as detailed in Section 6.14. 

The reaction is quenched by the addition of 1.28 g (2.94 mmol) of molybdenum pentoxidc/pyridinc/UMPA, and the yellow slurry is stirred initially at OX (30 min), then for 45 min at 25 X. The mixture is added to 1 N sodium hydroxide and extracted with diethyl ether. The ethereal solution is washed with brine, dried over Na,S04 and concentrated in vacuo to give 0.705 g (100%) of an oily, light-yellow solid. Analysis of the crude aldol adduct by 1 C NMR and analytical HPLO (Waters, Radial Pak, 8 mm x 10 cm, silica gel, ethyl acetate/hexane, 15 85) indicates only one. un-diastereomer (2X3S ) accompanied by approximately 10% of the two ethyl acetate/hexane affords fine white needles yield 0.359 g (57%) mp 155.5 156.5X (a]u -92.5 (c = 0.0294, CHCfi). 

In the determination of molybdenum in uranium alloys containing 2.5% molybdenum,20 the uranium had to be removed because its high absorbance made the method insensitive. After a single solvent extraction, the molybdenum could be determined with a standard deviation... 

A preparation of the third nitrogenase from A. vinelandii, isolated from a molybdenum-tolerant strain but lacking the structural genes for the molybdenum and vanadium nitrogenases, was discovered to contain FeMoco 194). The 8 subunit encoded by anfG was identified in this preparation, which contained 24 Fe atoms and 1 Mo atom per mol. EPR spectroscopy and extraction of the cofactor identified it as FeMoco. The hybrid enzyme could reduce N2 to ammonia and reduced acetylene to ethylene and ethane. The rate of formation of ethane was nonlinear and the ethane ethylene ratio was strongly dependent on the ratio of nitrogenase components. 

The molybdenum cofactor was liberated from D. gigas AOR, and under appropriate conditions was transferred quantitatively to nitrate reductase in extracts of Neurospora crassa nit-1 mutant) to yield active nitrate reductase 217). On the basis of molybdenum content, the activity observed for reconstitution with molybdenum cofactor of D. gigas was lower (25%) than the values observed for the procedure using extractable molybdenum cofactor of XO, used as reference. This result can now be put in the context of the difference in pterin present (MPT-XO and MCD-AOR) 218). 

Primary Mined particularly for the molybdenum contained in the ores. In some instances, molybdenum could be the only valuable metal recovered from the ore. The Questa deposit in New Mexico is mined exclusively for molybdenum content. In other deposits molybdenum may be the main product recovered together with one or more products. In these deposits the molybdenum content alone would allow for a profitable operation. The ore at the Climax mine in Colorado is of this type. Currently, monazite, pyrite, tin, and tungsten are recovered from the ore none of these by-products exists singly nor together in sufficient quantity so that the ore could be mined profitably merely for the extraction of one or all of these by-products. 

Co-product of copper molybdenum ores In these ores neither copper nor molybdenum occurs in large enough quantity for the ore to be mined profitably for the extraction of just one. Operation would be profitable when both are recovered. 

C. K. Gupta, Extractive Metallurgy of Molybdenum, CRC Press, Florida, USA, 1992. 

Zhang, P. W. Inoue, K. Yoshizuka, K. Tsuyama, H. Extraction and selective stripping of molybdenum(VI) and vanadium(IV) from sulfuric acid solution containing aluminum(III), cobalt(II), nickel(II) and iron(III) by LIX 63 in Exxsol D80. Hydrometallurgy 1996, 41, 45-53. 

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