Byproducts minerals/ores

Chemical processes produce complex mixtures of compounds from various feedstocks. Proper operation of chemical reactors often requires that the feed contain only certain species in specified ratios. Thus, separation and purification of species from feedstocks, whether petroleum, coal, mineral ores, or biomass, must be accomplished. Similarly, a mixture leaving a reactor must be separated into purified products, byproducts, unreacied feed, and waste materials. Separation processes ate also of importance where no reaction is involved as in seawater desalination by reverse osmosis, crystallization, or evaporation in the fractionation of crude petroleum or in the drying of solids or devolalization of polymers where diffusion within a porous solid is of importance. 

After mining, the raw ore is finely crushed and ground and undergoes a froth flotation ben-eficiation process to concentrate and separate celestine from byproduct minerals (e.g., barite). Then, the concentrate ore is reduced by pyrolysis in a kiln to strontium sulfide (i.e., SrS or black ash). The black ash is then dissolved in pure water, and the aqueous solution is treated with sodium carbonate to precipitate the strontium-carbonate crystals. After the strontianite crystals are removed and dried, the strontianite undergoes a calcination, evolving carbon dioxide and giving anhydrous strontium oxide (i.e., SrO, strontia). Strontium metal can be obtained either by thermal reduction of this strontium oxide with molten aluminum in a vacuum or by fused strontium chloride electrolysis. 

As a specific illustration reference may be drawn to molybdenum reserve scenario in the United States. The reserves are mainly grouped under five categories (i) primary, (ii) byproduct of copper ores, (iii) co-product of copper-molybdenum ores, (iv) by-product of tungsten ores, and (v) by-product of uranium ores. These have been presented and briefly elaborated in Table 1.14. It may finally be recorded by way of summary that the present day molybdenum sources in the world today seem to be principally of two main kinds first, the large-tonnage, low-grade, disseminated type of deposit in which molybdenite is the principal economic mineral second, the deposits in which molybdenite occurs as a by-product in... 

Sulfuric acid is often made as a byproduct of the mining of naturally occurring metal sulfide ores (mineral deposits). To purify a metal from an ore, the ore is heated in a process called smelting. 

Phosphates. The two major phosphate bearing ores are monazite and xenotime, the former being a source of light lanthanides and the latter a source of the heavy rare earths, see Table IV. Deposits in the form of heavy mineral sands are the major source of monazite. They are usually exploited as a byproduct of rutile, ilmenite, and zircon mining operations. 

Silver is widely distributed throughout the world. It rarely occurs in native form, but is found in ore bodies as silver chloride, or more frequently, as simple and complex sulfides. In former years, simple silver and gold-silver ores were processed by amalgamation or cyanidation processes, The availability of ores amenable to treatment by these means has declined. Most silver is now obtained as a byproduct or coproduct from base metal ores, particularly those of copper, lead, and zinc. Although these ores are different in mineral complexity and grade, processing is similar. 

Tantalum is found in a number of oxide minerals, which almost invariably also contain niobium (columbium). The most important tantalum-bearing minerals are tantalite and columbite. which are variations of the same natural compound (Fe, Mn)(Ta, Nb Og. Much of the tantalum concentrates has been obtained as a byproduct from tin mining in recent years, tin slags, which are a byproduct of the smelting of cassiierite ores, such as those found in the Republic of Congo. Nigeria, Portugal. Malaya, and Thailand have been an important raw material source for tantalum. 

The solvent extraction of rare-earth nitrates into solutions of TBP has been used commercially for the production of high-purity oxides of yttrium, lanthanum, praseodymium and neodymium from various mineral concentrates,39 as well as for the recovery of mixed rare-earth oxides as a byproduct in the manufacture of phosphoric acid from apatite ores.272 273 In both instances, extraction is carried out from concentrated nitrate solutions, and the loaded organic phases are stripped with water. The rare-earth metals are precipitated from the strip liquors in the form of hydroxides or oxalates, both of which can be calcined to the oxides. Since the distribution coefficients (D) for adjacent rare earths are closely similar, mixer—settler assemblies with 50 or more stages operated under conditions of total reflux are necessary to yield products of adequate purity.39... 

World sulfur reserves. The earth s crust contains about 0.6% S, where it occurs as elemental S (brimstone) in deposits associated with gypsum and calcite combined S in metal sulfide ores and mineral sulfates as a contaminant in natural gas and crude oils as pyritic and organic compounds in coal and as organic compounds in tar sands (Tisdale and Nelson, 1966). The elemental form commonly occurs near active or extinct volcanoes, or in association with hot mineral spings. Estimates by Holser and Kaplan (1966) of the terrestrial reservoirs of S suggest that about 50% of crustal S is present in relatively mobile reservoirs such as sea water, evaporites, and sediments. The chief deposits of S in the form of brimstone and pyrites are in Western European countries, particularly in France, Spain, Poland, Japan, Russia, U.S.A., Canada, and Mexico. World production of S in the form of brimstone and pyrites was approximately 41 Tg in 1973 other sources accounted for about 8 Tg, making a total of 49 Tg (Anon, 1973). Byproduct S from sour-gas, fossil fuel combustion, and other sources now accounts for over 50% of S used by western countries, as shown in Fig. 9.1. This percentage may increase as pollution abatement measures increase the removal of SO2 from fossil fuel, particularly in the U.S.A. Atmospheric S, returned to the earth in rainwater, is also a very important source of S for plants. 

Like the other alkali metals, cesium is a soft, silvery metal, but it appears golden if it has been exposed to small amounts of oxygen. It is not found in its metallic state in nature it is obtained as a byproduct of lithium processing of the mineral lepidolite. Its most significant ore is pollucite, and the world s largest pollucite deposit is found in Bernic Lake, Manitoba, Canada. Cesium s average crustal abundance is about 3 parts per million. Cesium is the most electropositive stable element and will ignite if exposed to air. Cesium burns blue in the flame test. 

Cd has a low abundance, with only 10 of the Earth s crust composed of the element. (Wells, 1984). The natural occurrence of Cd is referred to in Table 6.1 (Bbhm and Schafers 1990). Cd minerals are scarce, but as a result of its similarity to Zn, Cd occurs by isomorphous replacement in almost all Zn ores. Methods of isolation involve floating and roasting Cd is invariably a byproduct of Zn and Pb, and is usually separated from Zn by distillation or by precipitation from sulfate solutions by Zn dust ... 

Mineral supplements are sold as organic or inorganic salts of metals synthesized by the chemical industry. Because minerals are generally recovered by mining ores or from byproducts of chemical processes, their use as nutritional supplements may not result in a mineral form that can be taken up by the body—one that is readily bioavailable. Some metals such as selenium and chromium are also offered as complexes with yeast to give a more organic nature to the products. ... 

Though Finland lacked deposits of coal, oil and many minerals, it did possess natural resources suitable for chemical production. In the 1910s, a new, rich copper mine at Outokumpu was opened its ore contained sulphur pyrites, among other things. However, the most valuable resources for the chemical industry were timber and water power. Processing staple wood products gave the forest industries opportunities to extract various chemicals as byproducts. Hydroelectricity was a new energy source for the electrochemical industries at the time. 

In nature thorium is commonly present as monazite, a lanthanide phosphate mineral that contains 1-15% ThOi and usually 0.1-1% UgOg. Thus, thorium is often produced as a byproduct together with rare earth metals and uranium. There are several production methods (see, e.g., Ritcey 2006). The choice of method depends not only on the composition of the ore but also on whether thorium is the main product or a by-product. 

The relative abundance of zinc in the Earth s crust is about 75 mg/kg (i.e., ppm wt.), less than vanadium, nickel, and chromium. Major zinc minerals are the sulfide sphalerite or blende [ZnS, cubic], smithsonite [ZnCOj, trigonal], and hemimorphite or calamine [Zn SijO/OHjj.HjO, monoclinic] and franklinite [ZnFe O, cubic]. Of these mainly the sphalerite is used as zinc ore. Moreover, in ore deposits, sphalerite is often associated with galena and pyrite, and because it contains nonnegligible amounts of impurities such as Cd, In, and Ge, sphalerite is the principal source of these metals as byproducts. In 2002, the world zinc concentrate production totaled ca. 8.728 x 10 tonnes of contained zinc. With roughly 233 mines operating worldwide, the Asia-Pacific region, with 108 mines and 3.794 X 10 tonnes per annum, and the Americas, with 82 mines and 3.803 x 10 tonnes annualy,... 

Beryl is a byproduct of other minerals occurring in pegmatites such as spodumene and lepi-dolite and is normally recovered through hand sorting. Commercial beryl contains roughly 10 wt.% BeO (i.e., 3.6 wL% Be metal), while bertrandite ore deposits are mined by an open-pit method, such as the US ore deposits of Delta in Utah, processed by Brush Wellman. 

The only common cadmium mineral, greenockite CdS, is almost always associated with the zinc ore mineral sphalerite. The average ratio between zinc and cadmium in these types of ores is 400 1, which means that the cadmium content is 0.25% with reference to zinc. Of the total output of cadmium in the world, about 80% comes as byproduct from primary zinc production and a small amount comes from lead production. The remaining part, about 20%, is obtained from cadmium scrap and other secondary sources, such as for instance dust generated by recycling of iron and steel scrap. 

Bismuth is even more rare in the earth s crust than antimony. Its content is 0.0085 g/tonne and it is the 71 most abundant element. It occurs in nature partly native as metal but mainly as the sulfidic minerals bismuthinite Bi Sj and tetradymite (telluric bismuth) Bi Te S. An oxidic mineral is bismite (bismuth ocher) BijOj. Bismuth is mainly obtained as a byproduct in the production of lead, copper and tungsten. In the working of sulfidic ores, bismuth concentrates are roasted to oxides, which are reduced by charcoal. Distillation in vacuum gives highly pure bismuth. 

The principal raw material source for sulfuric acid production is SO obtained on burning sulfur. In addition, the main minerals of many metals, for example, zinc, lead, copper and silver, are sulfides. A significant quantity of SOj is also obtained as a byproduct from the metallurgical treatment of these ores. Partly this is a result of laws restricting SO emissions, but partly it is also due to the desire to improve process economics. Sulfur dioxide is oxidized to the trioxide SOj in the contact process at 450°C. A catalyst is used, which has rnain component. SOj is absorbed... 

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