Molybdenum separation

The recent report of the reaction of Mo2(02CCH3)4 with 2,6-dimethoxy-phenyllithium to form Mo2(DMP)4 is highly significant in view of the resulting value determined for the molybdenum-molybdenum separation in this dimer (90). 

Laurinat, J.E. 2007. SASSE modeling of a uranium/molybdenum separation flowsheet. WSRC-STI-2007-00111. 

Silver and gold do not alloy with molybdenum platinum can take at least 16 per cent, of the metal into solid solution near the melting-point, but on cooling the molybdenum separates out. ... 

Molybdenum Separation [5.1,5.31,5.33,5.35]. If sodium sulfide is added to the neutral or slightly alkaline sodium tungstate solution, the molybdate ion is converted to... 

Common alloying elements include nickel to improve low temperature mechanical properties chromium, molybdenum, and vanadium to improve elevated-temperature properties and silicon to improve properties at ordinary temperatures. Low alloy steels ate not used where corrosion is a prime factor and are usually considered separately from stainless steels. 

Both oae-step and two-step oxidation processes are known. A number of catalyst systems are known most use a molybdenum compound as the main component. The acryhc acid is esterified with alcohol to the desired acryhc ester ia a separate process (63—66). 

Flotation or froth flotation is a physicochemical property-based separation process. It is widely utilised in the area of mineral processing also known as ore dressing and mineral beneftciation for mineral concentration. In addition to the mining and metallurgical industries, flotation also finds appHcations in sewage treatment, water purification, bitumen recovery from tar sands, and coal desulfurization. Nearly one biUion tons of ore are treated by this process aimuaHy in the world. Phosphate rock, precious metals, lead, zinc, copper, molybdenum, and tin-containing ores as well as coal are treated routinely by this process some flotation plants treat 200,000 tons of ore per day (see Mineral recovery and processing). Various aspects of flotation theory and practice have been treated in books and reviews (1 9). 

Minerals and Metals. HCl is consumed in many mining operations for ore treatment, extraction, separation, purification, and water treatment (see Mineral recovery and processing). Significant quantities are also used in the recovery ofmolybdenum (see Molybdenum and molybdenum alloys) and gold (see Gold and gold compounds). This market consumed about 36 thousand metric tons in 1993. 

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

The goal of lubrication is elimination of this wear and minimizing friction otherwise encountered in dry sliding. This is accompHshed ideally with complete separation of the mbbing surfaces with a full film of lubricant. When complete hill-film separation is impossible, surface chemical effects of a lubricating oil and its additives, or solid-film lubricants such as graphite and molybdenum sulfide, can assist. 

Reduction to Solid Metal. Metals having very high melting points caimot be reduced in the Hquid state. Because the separation of a soHd metallic product from a residue is usually difficult, the raw material must be purified before reduction. Tungsten and molybdenum, for instance, are prepared by reduction of a purified oxide (WO, MoO ) or a salt, eg, (NH2 2 G4, using hydrogen. A reaction such as... 

Copper and silver combined with refractory metals, such as tungsten, tungsten carbide, and molybdenum, are the principal materials for electrical contacts. A mixture of the powders is pressed and sintered, or a previously pressed and sintered refractory matrix is infiltrated with molten copper or silver in a separate heating operation. The composition is controlled by the porosity of the refractory matrix. Copper—tungsten contacts are used primarily in power-circuit breakers and transformer-tap charges. They are confined to an oil bath because of the rapid oxidation of copper in air. Copper—tungsten carbide compositions are used where greater mechanical wear resistance is necessary. 

After epoxidation, propylene oxide, excess propylene, and propane are distilled overhead. Propane is purged from the process propylene is recycled to the epoxidation reactor. The bottoms Hquid is treated with a base, such as sodium hydroxide, to neutralize the acids. Acids in this stream cause dehydration of the 1-phenylethanol to styrene. The styrene readily polymerizes under these conditions (177—179). Neutralization, along with water washing, allows phase separation such that the salts and molybdenum catalyst remain in the aqueous phase (179). Dissolved organics in the aqueous phase ate further recovered by treatment with sulfuric acid and phase separation. The organic phase is then distilled to recover 1-phenylethanol overhead. The heavy bottoms are burned for fuel (180,181). 

The head of the femoral component then articulates with an ion-bombarded, HDPE, high walled, acetabular liner which fits iato a screwed ia, machined, titanium, chromium—cobalt—molybdenum or vanadium—aluminum metallic alloy hydroxyapatite-coated acetabular shell/cup. Each of the separate parts of the modular system for total hip arthroplasty is manufactured ia several different sizes. 

A number of substances, such as the most commonly used sulfur dioxide, can reduce selenous acid solution to an elemental selenium precipitate. This precipitation separates the selenium from most elements and serves as a basis for gravimetry. In a solution containing both selenous and teUurous acids, the selenium may be quantitatively separated from the latter by performing the reduction in a solution which is 8 to 9.5 W with respect to hydrochloric acid. When selenic acid may also be present, the addition of hydroxylamine hydrochloride is recommended along with the sulfur dioxide. A simple method for the separation and deterrnination of selenium(IV) and molybdenum(VI) in mixtures, based on selective precipitation with potassium thiocarbonate, has been developed (69). 

As the result of the performed investigations was offered to make direct photometric determination of Nd microgram quantities in the presence of 500-fold and 1100-fold quantities of Mo and Pb correspondingly. The rare earth determination procedure involves sample dissolution in HCI, molybdenum reduction to Mo (V) by hydrazine and lead and Mo (V) masking by EDTA. The maximal colour development of Nd-arsenazo III complex was obtained at pH 2,7-2,8. The optimal condition of Nd determination that was established permit to estimate Nd without separation in solution after sample decomposition. Relative standard deviations at determination of 5-20 p.g of Nd from 0,1 g PbMoO are 0,1-0,03. The received data allow to use the offered procedure for solving of wide circle of analytical problems. 

The pulp from this grinding proeess is introdueed into a floating proeess to whieh water and ehemieal reaetants are added. This proeess results in a eolleetive eoneentrate, Cu-Mo, eontaining approximately 30% eopper and 1% molybdenum. In a follow-up proeess, the eopper and sulfur-molybdenum eoneentrate are separated. 

Important differences distinguish the molybdenum and tungsten systems. In aqueous solution, equilibration of the molybdenum species is complete within a matter of minutes whereas for tungsten this may take several weeks it also transpires that whereas the basic unit of most isopolymolybdates is an MOg octahedron with a pair of cis-terminal oxygens, that of the isopolytungstates is more commonly an MOg octahedron with only one terminal oxygen. The two must therefore be considered separately. 

Of the many molybdenum sulfides which have been reported, only MoS, M0S2 and M02S3 are well established. A hydrated form of the trisulfide of somewhat variable composition is precipitated from aqueous molybdate solutions by H2S in classical analytical separations of molybdenum, but it is best prepared by thermal decomposition of the thiomolybdate, (NH4)2MoS4. MoS is formed by heating the calculated amounts of Mo and S in an evacuated tube. The black M0S2, however, is the most stable sulfide and, besides being the principal ore of Mo,... 

Molybdates yield sparingly soluble orange-yellow molybdyl oxinate with oxine solution the pH of the solution should be between the limits 3.3-7.6. The complex differs from other oxinates in being insoluble in organic solvents and in many concentrated inorganic acids. The freshly precipitated compound dissolves only in concentrated sulphuric acid and in hot solutions of caustic alkalis. This determination is of particular interest, as it allows a complete separation of molybdenum from rhenium. 

Molybdenum(VI), vanadium(V), mercury, and iron interfere permanganates, if present, may be removed by boiling with a little ethanol. If the ratio of vanadium to chromium does not exceed 10 1, nearly correct results may be obtained by allowing the solution to stand for 10-15 minutes after the addition of the reagent, since the vanadium-diphenylcarbazide colour fades fairly rapidly. Vanadate can be separated from chromate by adding oxine to the solution and extracting at a pH of about 4 with chloroform chromate remains in the aqueous solution. Vanadium as well as iron can be precipitated in acid solution with cupferron and thus separated from chromium (III). 

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