VANADIUM MINING
VANADIUM :
Vanadium is a soft and ductile, silver-grey metal. It has good quality resistance to corrosion by alkalis, sulfuric and hydrochloric acid. It oxidizes eagerly at about 933? K (660 C). Vanadium has good structural strength and a low fission neutron cross section, making it useful in nuclear applications. Although a metal, it shares with chromium and manganese the property of having valency oxides with acid properties.
Common oxidation states of vanadium include +2, +3, +4 and +5. A popular experiment with ammonium vanadate NH4VO3, reducing the compound with zinc metal, can demonstrate colorimetrically all four of these vanadium oxidation states. An oxidation state of +1 is rarely seen.
Most continental waters show a vanadium concentration of less than 3 ppb. However, the groundwater of Mt. Fuji contains a very high concentration of vanadium-up to 150 ppb. This vanadium is solubilized from the basalt by the groundwater. The vanadium content in Mt. Fuji becomes higher at places nearer the summit and deeper in the ground. Recently this high-vanadium water of Mt. Fuji has been sold by many companies as an agent to cope with diabetes. However, there is no concrete evidence for its efficacy. The rainbow trout living in the Mt. Fuji water showed much higher accumulation of vanadium in kidneys and bone.
Powdered metallic vanadium is a fire hazard, and unless known otherwise, all vanadium compounds should be measured highly toxic. Generally, the higher the oxidation state of vanadium, the more toxic the compound is. The most dangerous compound is vanadium pentoxide.
MINING AND PROCESSING :
The major ores of vanadium are patronite (VS4), carnotite [K2(UO2)2(VO4)3H2O], and vanadinite [Pb5(VO4)3Cl]. Since much of the vanadium present in the igneous rocks occurs in the relatively insoluble trivalent state, substituting for ferric iron in ferromagnesium silicates, magnetite (an iron ore), ilmenite (a titanium ore), and chromite, the ore deposits mined for vanadium are rare. Some of the other sources of the metal include ash from the combustion of fossil fuel, slag from phosphate ore, the aluminum ore bauxite, etc.
The world's largest mines of vanadium covers the titaniferous magnetite reserves in regions such as the Bushveld of South Africa, the Kachkanar Massif of the Ural Mountains,and China's Szechwan province. The carnotite ores found in the sandstones of the Colorado Plateau are significantly mined for vanadium and uranium.
Vanadium is normally found within magnetite iron ore deposits, and is usually mined as a byproduct and not as a primary mineral. Since vanadium is essentially mined as the by-product of the ores that are mined, the mining methods suitable to those ores are taken into consideration. Vanadium is often collaborated with titanium, which is separated as an impurity during processing. The higher the titanium content in the ore, the harder it is to extract the vanadium metal. The resultant is always found to be vanadium pentoxide, a compound which can be used in certain applications or in producing ferrovanadium to be used in steel.
HOW IS VANADIUM OBTAINED?
Vanadium is never found unbound in nature and is considered to be the 20th most abundant element in the earth's crust. Since it is not found individually as a metal, it occurs in about 65 different minerals. Patronite, vanadinite, carnotite and bauxite are some of those vanadium containing minerals. Even in carbon containing deposits such as crude oil, coal, oil shale and tar sands, vanadium is known to have its presence.
The general process of obtaining vanadium from its ores is in the form of vanadium pentoxide (V2O5) through performing a variety of processes like smelting, leaching, and roasting after which the pentoxide is reduced to ferrovanadium or vanadium powder. Very pure vanadium metal resembles titanium with respect to certain physical properties of being corrosion resistant, hard, and steel gray in colour.
EXTRACTING AND REFINING :
Generating Vanadium pentoxide from various ores
The vanadium containing titaniferous magnetite ore is mined, crushed and partially reduced with coal and then melted in a rotary furnace. This results in a slag which contains most of the titanium and a pig iron which contains most of the vanadium.The slag is removed and the molten pig iron is blown with oxygen to produce a new slag which contains 12-24 percent vanadium pentoxide (V2O5). This compound is used in the further processing of the metal.
When it comes to extraction from the carnotite ore, it requires leaching the ore concentrate for 24 hours completely together with hot sulfuric acid and an oxidant such as sodium chlorate, following which vanadium is obtained as a co-product with uranium. After clearing the solids, the leachate is fetched into a solvent extraction circuit where the uranium is removed in an organic solvent consisting of 2.5 percent-amine, 2.5-percent isodecanol and 95 percent kerosene. Vanadium which remains in the obtained raffinate is fed into a second solvent extraction circuit. This vanadium is cleared with a 10 percent soda ash solution and ammonium sulfate mixed with it is precipitated. The ammonium metavanadate precipitate obtained is then filtered, dried, and calcined to produce Vanadium pentoxide.
Most of the vanadium-bearing ores or slags are crushed, ground, screened, and mixed with a sodium salt such as sodium chloride or sodium carbonate for the production of vanadium pentoxide. This charge is then roasted at about 850?C to convert the oxides to sodium metavanadate, which can be leached in hot water. By acidifying the leachate with sulfuric acid, the vanadium is precipitated as sodium hexavanadate. This compound, known as red cake, can be fused at 700?C to yield technical-grade vanadium pentoxide which is of at least 86 percent purity. Further purification can take place by dissolving it in an aqueous solution of sodium carbonate. The iron, aluminum, and silicon impurities in the red cake precipitate from the solution upon adjusting the acidity levels in the next stage. By adding ammonium chloride, the vanadium is precipitated as ammonium metavanadate. After filtration, the precipitate is calcined to produce highly pure Vanadium pentoxide which is greater than 99.8 percent.
Production of Ferrovanadium
Ferrovanadium which contains about 35-80 percent vanadium is produced by an experiment which requires melted scrap iron, a mixture of Vanadium pentoxide, aluminum, and a flux to be added and heated in an electric arc furnace. The flux required can either be calcium fluoride or calcium oxide. In the course of time, the aluminum metal forms a slag and is converted to alumina, whereas the Vanadium pentoxide is reduced to vanadium metal, which is dissolved in the molten iron. The heat supply required for this exothermic oxidation-reduction reaction must develop a kindling temperature of 950?C. The heating is stopped and the electrodes are withdrawn until the reaction is completed. They are then reinserted into the molten slag, after which the furnace is reheated to improve settling of the ferrovanadium.
The same can be obtained by performing the aluminothermic process in a refractory-lined steel pot or water-cooled copper crucible where a charge of Vanadium pentoxide along with iron oxide and aluminum is ignited with a barium-peroxide fuse or a magnesium ribbon.
Obtaining of Vanadium metal
Pure vanadium metal can be obtained by metallothermically reducing vanadium pentoxide. This can be done either by calcium reduction method or aluminothermic process. In the calcium reduction method, an exothermic reaction is carried out in a sealed vessel where calcium chloride is used as a flux and the vanadium metal is obtained in the form of droplets or beads. This process requires a large amount of reducing agent and produces the metal in the range of 75-80 percent. In the aluminothermic process, Vanadium pentoxide is mixed with aluminum powder and heated in an electric furnace or ignited in a refractory-lined vessel using barium peroxide as the booster. The vanadium obtained in this case can be further purified by electron-beam melting.
TOP VANADIUM PRODUCING COUNTRIES:
Vanadium is a silvery metal used in steel alloys, as a catalyst and in nuclear reactors. The world's total vanadium production comes mainly from five countries:
1.China: China is the world's leading producer of vanadium, producing 54,000 metric tons in 2019. The majority of China's production is from the iron-vanadium ore deposit in the Sichuan province.
2.Russia: Russia is the second-largest producer of vanadium, producing roughly 21,000 metric tons in 2019. The majority of Russia's vanadium production comes from the Kachkanar mine in the Sverdlovsk region.
3.South Africa: South Africa is the third-largest producer of vanadium, producing roughly 17,000 metric tons in 2019. The majority of South Africa's production comes from the Bushveld igneous complex.
4.Brazil: Brazil is the fourth-largest producer of vanadium, producing roughly 7,000 metric tons in 2019. The majority of Brazil's production comes from the Carajas mine in the Amazon region.
5.Australia: Australia is the fifth-largest producer of vanadium, producing roughly 4,000 metric tons in 2019. The majority of Australia's production comes from the Windimurra mine in the state of Western Australia.
USES OF VANADIUM :
Titanium-aluminum-vanadium alloy is used in jet engines and in high-speed aircrafts.
Vanadium foil is used in cladding titanium to steel.
Vanadium-gallium tape is used in superconducting magnets.
Vanadium pentoxide is used in ceramics and as a catalyst for the production of sulfuric acid.
Vanadium-steel alloys are used in the making of armour plate, axles, tools, piston rods and crankshafts.
When mixed with gallium, vanadium is used to manufacture super-conductive magnets used as high field inserts.
Being highly rust resistant, it is used in making different springs, tools and heavy industry equipment.
It is also used as an agent to fix the colour on fabric and thus dyeing and synthetic fabrics use vanadium.
ANNUAL VANADIUM USAGE :
Vanadium is a chemical element primarily used in steel alloys, to improve their strength and durability. It is also used in other alloys, such as titanium and aluminum, to improve their corrosion resistance and other properties. In addition, vanadium is used as a catalyst in the production of sulfuric acid and other chemicals and as an additive in some pigments and dyes.
The primary use of vanadium is in the production of specialty steels and alloys. Vanadium can be added to steel to increase its strength and toughness while reducing its weight. This is a major application for vanadium, as it is found in the majority of steel alloys used in the construction of buildings and bridges. Vanadium-containing alloys are also used in the production of aircraft, automobiles, and other machines.
In addition, vanadium is used in the production of titanium alloys. Titanium alloys are lightweight and strong, and they are used in the aerospace and medical industries. Vanadium helps improve the corrosion resistance of these alloys, making them more suitable for use in harsh environments.
VANADIUM PRODUCTION IN THE WORLD :
It is concluded that there is no demand for pure vanadium on a large scale, and the isolation of the metal is therefore not an industrial process. Even on a small scale basis, the operation is attained with a certain difficulty, accompanied by very high temperatures necessary for the reduction of vanadium compounds and the tendency for re-oxidation to take place. Much of the world's vanadium production is extracted from vanadium-bearing ultramafic gabbro bodies. According to sources, about 85 percent of the world's vanadium comes from three major countries: South Africa, China and Russia. History has it that some of the world's important vanadium mines include the Bushveld complex in South Africa; the high-grade Maracas mine in Brazil and EVRAZ's Vanady Tula mine in Russia which is the largest European producer of vanadium pentoxide and ferrovanadium alloys.
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