Molybdenum-Containing Minerals

Ilsemannite Molybdenum oxides M0O2.4Mo03(variable) 

Chillagite Lead tungsto-molybdate 3PbW04.PbMo04 

Braithwaite pointed out that China and the Confederation of Independent States were now introducing substantial quantities of by-product molybdenum. The estimated ore reserves in the CIS alone are about 1.6 x 10 tonnes, with a moiybdenum content varying from 0,015% to 0.09%. This represents a total molybdenum content of about 800,000 tonnes not previously included in Western estimates. Inclusion of similar quantities from China and the remainder of the Far East would raise the estimated world total to about seven to nine million tonnes. 

Prior to 1925 the production of molybdenum was very irregular. It was only about 100 tonnes in 1914, reached 8,000 tonnes in 1918, and virtually ceased from 1920 to 1925. Since then it has increased dramatically , to 2,200 tonnes in 1933, 9,000 tonnes in 1938, 31,000 tonnes in 1943, 58,000 tonnes in 1966, and more than 100,000 tonnes by 1989. During the nineteen seventies the demand for molybdenum in the Western world had outstripped the supply , as shown in Table 2.2, and several important new mines were brought into operation. 

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There are many molybdenum-containing minerals in nature but only one of them, molybdenite, molybdenum disulfide, MoSj (Figures M36 and M37) has any economic importance. Typically, molybdenite occurs in an environment of silica-rich intrusive rocks, consolidated from magma beneath the surface of the earth. 

Niobium metal is typically gray or dull silver in color. It is one of the refractory metals along with tantalum, tungsten, molybdenum, and rhenium, due to its very high melting point. It is estimated that niobium has a natural occurrence in Earth s crust of approximately 20 parts per milhon (ppm). The largest niobium-containing mineral reserves are located in Brazil and Canada. 

The reaction conditions used in the first phase (sump phase) are generally temperatures of 400 to 500 °C and pressures ranging from 100 to 700 bar. Molybdenum and tungsten oxides are commonly used as catalysts, together with iron compounds. In the /G-hydrogenation process, Bayer-mass ( red mud ), a by-product of bauxite processing, was used as an iron catalyst. Coals which contain mineral compounds with the necessary catalytic activity can be hydrogenated without the addition of catalysts. 

Thorium occurs in thorite and in thorianite. Large deposits of thorium minerals have been reported in New England and elsewhere, but these have not yet been exploited. Thorium is now thought to be about three times as abundant as uranium and about as abundant as lead or molybdenum. Thorium is recovered commercially from the mineral monazite, which contains from 3 to 9% Th02 along with rare-earth minerals. 

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). 

Under unusual circumstances, toxicity may arise from ingestion of excess amounts of minerals. This is uncommon except in the cases of fluorine, molybdenum, selenium, copper, iron, vanadium, and arsenic. Toxicosis may also result from exposure to industrial compounds containing various chemical forms of some of the minerals. Aspects of toxicity of essential elements have been pubhshed (161). 

A U.S. Bureau of Mines survey covering 202 froth flotation plants in the United States showed that 198 million tons of material were treated by flotation in 1960 to recover 20 million tons of concentrates which contained approximately 1 billion in recoverable products. Most of the worlds copper, lead, zinc, molybdenum, and nickel are produced from ores that are concentrated first by flotation. In addition, flotation is commonly used for the recoveiy of fine coal and for the concentration of a wide range of mineral commodities including fluorspar, barite, glass sand, iron oxide, pyrite, manganese ore, clay, feldspar, mica, sponumene, bastnaesite, calcite, garnet, kyanite, and talc. 

T ike metals minerals also exhibit typical crystalline structures. As an example, the structure of molybdenite is shown in Figure 1.17. It is hexagonal with six-pole symmetry and contains two molecules per unit cell. Each sulfur atom is equidistant from three molybdenum atoms and each molybdenum atom is surrounded by six sulfur atoms located at the comers of a trigonal prism. There are two types of bonds that can be established between the atoms which constitute the molybdenite crystal stmcture. They are the covalent bonds between sulfur and molybdenum atoms and the Van der Waals bonds between sulfur-sulfur atoms. The Van der Waals bond is considerably weaker than the covalent sulfur-molybdenum bond. This causes the bonds of sulfur-sulfur to cleave easily, imparting to molybdenite the property of being a dry lubricant. Molybdenite adheres to metallic surfaces with the development of a molecular bond and the friction between metallic surfaces is replaced by easy friction between two layers of sulfur atoms. 

Molybdenum is not found naturally in its elemental form. It is obtained primarily from the mineral molybdenite (MoS2), which contains an average 59.9% of molybdenum. It is the only source of molybdenum which accounts for most of the world s molybdenum supply. Processing flowsheet of molybdenum from this commercial source into principal commercial forms is illustrative of the wide and diverse applications of molybdenum and its chemicals (Figure 1.19). 

MinCore Inc., a private mineral exploration company based in Toronto, Canada, is currently exploring the Tameapa property in Sinaloa Mexico, that contains two advanced mineral prospects separated by 2.5 km, named Pico Prieto (copper-molybdenum porphyry) and Venado (structurally-controlled porphyry... 

Physical Form, brown to black oily liquid new mineral-based crankcase oil contains petrochemicals (straight-chain hydrocarbons, aromatic hydrocarbons, and polyaromatic hydrocarbons or PAH) plus stabilizers and detergents including zinc dithiophosphate, zinc diaryl or dialkyl dithiophosphates (ZTDP), calcium alkyl phenates, magnesium, sodium, and calcium sulfonates, tricresyl phosphates, molybdenum disulfide, heavy metal soaps, cadmium, and zinc. ... 

The publications and correspondence of Bergman and Scheele contain interesting allusions to the de Elhuyar brothers, to Hjelm, and to the early history of the metals tungsten and molybdenum which they discovered. The presence of a new metal in pitchblende was recognized by Klaproth in 1789, but it remained for Peligot half a century later to isolate uranium. Chromium, now the most familiar element of the group, was the last to be discovered when the immortal French chemist Vauquelin finally isolated it in 1798 from a Siberian mineral. For further information about tungsten see pp. 284-301. 

When Klaproth dissolved some pitchblende in nitric acid and neutralized the acid with potash, he obtained a yellow precipitate which dissolved in excess potash. Klaproth concluded correctly that the mineral must contain a new element, which he named in honor of the new planet, Uranus, which Herschelhad recently discovered (12). He then attempted to obtain metallic uranium just as Hjelm had prepared metallic molybdenum. By strongly heating an oil paste of the yellow oxide in a charcoal crucible, he obtained a black powder with a metallic luster, and thought he had succeeded in isolating metallic uranium (29). For over fifty years the elementary nature of his product was accepted by chemists, but in 1841 Peligot showed that this supposed uranium metal was really an oxide. 

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