A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, a scientific process of separating two or more substances in order to obtain purity. At least one product mixture from the separation is enriched in one or more of the source mixture's constituents. In some cases, a separation may fully divide the mixture into pure constituents. Separations exploit differences in chemical properties or physical properties (such as size, shape, charge, mass, density, or chemical affinity) between the constituents of a mixture.
35-480: A sieve , fine mesh strainer , or sift , is a tool used for separating wanted elements from unwanted material or for controlling the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet material. The word sift derives from sieve . In cooking, a sifter is used to separate and break up clumps in dry ingredients such as flour , as well as to aerate and combine them. A strainer (see Colander ), meanwhile,
70-496: A sodium hydroxide solution at a temperature of 150 to 200 °C (300 to 390 °F). At these temperatures, the aluminium is dissolved as sodium aluminate (the Bayer process ). The aluminium compounds in the bauxite may be present as gibbsite (Al(OH) 3 ), boehmite (AlOOH) or diaspore (AlOOH); the different forms of the aluminium component will dictate the extraction conditions. The undissolved waste, bauxite tailings , after
105-450: A moist slurry forms in the can, then there is a likelihood for the cargo to liquefy; although conversely, even if the sample remains dry it does not conclusively prove that it will remain that way, or that it is safe for loading. Bauxite is the main source of the rare metal gallium . During the processing of bauxite to alumina in the Bayer process , gallium accumulates in the sodium hydroxide liquor. From this it can be extracted by
140-461: A petition against the mining of bauxite that was signed by 135 accomplished and well known "Intellectuals". This petition helped unite the scattered anti-bauxite movement into a unified opposition against the state. These acts of governmental defiance were met with repressive state actions. Many domestic online reporters were arrested, and legislative action was taken to repress scientific research. Most of India's bauxite ore reserves, which are among
175-446: A self-cleaning strainer instead of a basket strainer or a simplex strainer due to limitations of simple filtration systems. The self-cleaning strainers or filters are more efficient and provide an automatic filtration solution. Sieving is a simple technique for separating particles of different sizes. A sieve such as used for sifting flour has very small holes. Coarse particles are separated or broken up by grinding against one another and
210-470: A small scale, as in a laboratory for analytical purposes, or on a large scale, as in a chemical plant . Some types of separation require complete purification of a certain component. An example is the production of aluminum metal from bauxite ore through electrolysis refining . In contrast, an incomplete separation process may specify an output to consist of a mixture instead of a single pure component. A good example of an incomplete separation technique
245-458: A temperature in excess of 1,000 °C (1,830 °F). This aluminium oxide is dissolved at a temperature of about 960 °C (1,760 °F) in molten cryolite . Next, this molten substance can yield metallic aluminium by passing an electric current through it in the process of electrolysis, which is called the Hall–Héroult process , named after its American and French discoverers. Prior to
280-499: A variety of methods. The most recent is the use of ion-exchange resin . Achievable extraction efficiencies critically depend on the original concentration in the feed bauxite. At a typical feed concentration of 50 ppm, about 15 percent of the contained gallium is extractable. The remainder reports to the red mud and aluminium hydroxide streams. Bauxite is also a potential source for vanadium . The social and environmental impacts of bauxite extraction are well documented. Most of
315-455: A wooden sieve might be made from wood or wicker . Use of wood to avoid contamination is important when the sieve is used for sampling. Henry Stephens, in his Book of the Farm , advised that the withes of a wooden riddle or sieve be made from fir or willow with American elm being best. The rims would be made of fir, oak or, especially, beech . A sieve analysis (or gradation test)
350-665: A youth march. In 2020, A Rocha Ghana also sued the government over the drilling in the reserve after they failed to provide a statement explaining their actions. In early 2009, the Vietnamese Government proposed a plan to mine remote regions of the central highlands. This proposal was highly controversial and sparked a nationwide debate and the most significant domestic conflict since the Vietnam War . Government scientists, journalists, religious leaders, retired high level state officials, and General Võ Nguyên Giáp ,
385-448: Is oil refining. Crude oil occurs naturally as a mixture of various hydrocarbons and impurities. The refining process splits this mixture into other, more valuable mixtures such as natural gas , gasoline and chemical feedstocks , none of which are pure substances, but each of which must be separated from the raw crude. In both complete separation and incomplete separation, a series or cascade of separations may be necessary to obtain
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#1732765399000420-548: Is a form of sieve used to separate suspended solids from a liquid by filtration . Some industrial strainers available are simplex basket strainers , duplex basket strainers , T-strainers and Y-strainers . Simple basket strainers are used to protect valuable or sensitive equipment in systems that are meant to be shut down temporarily. Some commonly used strainers are bell mouth strainers , foot valve strainers , basket strainers. Most processing industries (mainly pharmaceutical, coatings and liquid food industries) will opt for
455-423: Is a practice or procedure used (commonly used in civil engineering or sedimentology ) to assess the particle size distribution (also called gradation) of a granular material. Sieve sizes used in combinations of four to eight sieves. Separation process Processes are often classified according to the particular properties they exploit to achieve separation. If no single difference can be used to accomplish
490-453: Is one of the only two upland evergreen forests in Ghana, and makes up a significant portion of the remaining 20% of forested habitat left in Ghana. The Atewa range falls under the jurisdiction of Akyem Abuakwa Traditional Area and is overseen by the king known as Okyenhene. In 2013, an NGO called A Rocha Ghana held a summit with the forestry and water resource commission, the minister of lands,
525-515: Is reddish-brown, white, or tan. In 1821, the French geologist Pierre Berthier discovered bauxite near the village of Les Baux in Provence , southern France . Numerous classification schemes have been proposed for bauxite but, as of 1982 , there was no consensus. Vadász (1951) distinguished lateritic bauxites (silicate bauxites) from karst bauxite ores (carbonate bauxites): In
560-534: The Boké Region of Guinea have caused in 35 conflicts which include movements of revolts and road blockades. These conflicts have resulted in the loss of human life, the destruction of heavy machinery, and damage to government buildings. The Atewa range in Ghana, classified as an ecologically important forest reserve with an area of 17,400 hectares (43,000 acres), has been is a recent site of conflict and controversy surrounding baxuite mining. The forest reserve
595-582: The Boké Region of Guinea, there has been a significant increase in bauxite mining pressure on the local population. This has resulted in potable water issues, air pollution, food contamination, and land expropriation disputes due to improper compensation. Bauxite mining has led to protests, civil unrest, and violent conflicts in Guinea, Ghana, Vietnam, and India. Guinea has a long history of mining related conflicts between communities and mining companies. Between 2015 and 2018, new bauxite mining operations in
630-520: The Ghana Integrated Bauxite and Aluminium Development Authority Act that would create the legal framework required to develop and establish an integrated bauxite industry. In may of that year, the government began drilling deep holes in the reserve. These actions sparked several protests, including a 95-kilometre (59 mi) march from the reserve to the presidential palace, an informational billboard campaign led by A Rocha Ghana, and
665-463: The free surface effect can cause the cargo to shift rapidly inside the hold and make the ship unstable, potentially sinking the ship. One vessel suspected to have been sunk in this way was the MS Bulk Jupiter in 2015. One method which can demonstrate this effect is the "can test", in which a sample of the material is placed in a cylindrical can and struck against a surface many times. If
700-417: The aluminium minerals gibbsite ( Al(OH) 3 ), boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite (FeO(OH)) and haematite ( Fe 2 O 3 ), the aluminium clay mineral kaolinite ( Al 2 Si 2 O 5 (OH) 4 ) and small amounts of anatase ( TiO 2 ) and ilmenite ( FeTiO 3 or FeO·TiO 2 ). Bauxite appears dull in luster and
735-410: The aluminium compounds are extracted contains iron oxides , silica , calcia , titania and some un-reacted alumina . After separation of the residue by filtering, pure gibbsite is precipitated when the liquid is cooled, and then seeded with fine-grained aluminium hydroxide . The gibbsite is usually converted into aluminium oxide , Al 2 O 3 , by heating in rotary kilns or fluid flash calciners to
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#1732765399000770-638: The case of Jamaica , recent analysis of the soils showed elevated levels of cadmium , suggesting that the bauxite originates from Miocene volcanic ash deposits from episodes of significant volcanism in Central America. Australia is the largest producer of bauxite, followed by Guinea and China . Bauxite is usually strip mined because it is almost always found near the surface of the terrain , with little or no overburden . Increased aluminium recycling , which requires less electric power than producing aluminium from ores, may considerably extend
805-410: The desired end products. In the case of oil refining, crude is subjected to a long series of individual distillation steps, each of which produces a different product or intermediate . Bauxite Bauxite ( / ˈ b ɔː k s aɪ t / ) is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium . Bauxite consists mostly of
840-425: The desired separation, multiple operations can often be combined to achieve the desired end. With a few exceptions, elements or compounds exist in nature in an impure state. Often these raw materials must go through a separation before they can be put to productive use, making separation techniques essential for the modern industrial economy. The purpose of separation may be: Separations may be performed on
875-488: The invention of this process, and prior to the Deville process , aluminium ore was refined by heating ore along with elemental sodium or potassium in a vacuum . The method was complicated and consumed materials that were themselves expensive at that time. This made early elemental aluminium more expensive than gold . As a bulk cargo , bauxite is a Group A cargo that may liquefy if excessively moist. Liquefaction and
910-462: The military leader of anti-colonial revolution, were among the many people across Vietnamese society who opposed the governments plans. In an attempt to stop the spread of information across the globe, the government banned domestic reporters from reporting on bauxite mining. However, reporters turned to Vietnamese language websites and blogs where the reporting and discussion continued. On April 12, 2009, several well-respected Vietnamese scholars started
945-401: The minister of the environment, and other important stakeholders. They came to the conclusion that no future government should mine bauxite in the region because the reserve is environmentally and culturally significant. In 2016, the government along with NGO's began the process of upgrading the reserved to a national park. However, that year an election took place, and before it became official,
980-492: The newly elected National Patriotic Party (NPP) rejected the plan. In 2017, the government of Ghana signed a Memorandum of Understanding with China to develop new bauxite mining infrastructure in Ghana. Although there was no official plan to mine the Atewa Forest Reserve, tensions between local communities, NGO and the government began to rise. In 2019, tensions began to reach a peak when the government presented
1015-491: The screen openings. Depending upon the types of particles to be separated, sieves with different types of holes are used. Sieves are also used to separate stones from sand. Sieving plays an important role in food industries where sieves (often vibrating) are used to prevent the contamination of the product by foreign bodies. The design of the industrial sieve is of primary importance here. Triage sieving refers to grouping people according to their severity of injury. The mesh in
1050-706: The strip mining process, the biodiversity and habitat once present in the area is completely lost and the hydrological and soil characteristics in the region are permanently altered. Other environmental impacts of bauxite mining include soil degradation , air pollution , and water pollution . Red mud is a highly alkaline sludge, with a high pH around 13, that is a byproduct of the Bayer process . It contains several elements such as sodium aluminoscilicate , calcium titanate , monohydrate aluminium, and trihydrate aluminium that do not break down in nature. When improperly stored, red mud can contaminate soil and water, which can result in local extinction of all life. Red mud
1085-466: The terrestrial and aquatic ecosystems. Historically, the Indigenous peoples living on these lands have shown resistance to development, and oppose any new bauxite mining projects in the area. This has led to violent conflicts between Indigenous communities and police. On December 16, 2000, police killed three Indigenous protestors and wounded over a dozen more during a protest over a bauxite project in
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1120-401: The top ten largest in the world, are located on tribal land. These tribal lands are densely populated and home to over 100 million Indigenous Indian peoples. The mountain summits located on these lands act as a source of water and greatly contribute to the regions fertility. The Indian bauxite industry is interested in developing this land for aluminum production, which poses great risk to
1155-436: The world's bauxite deposits can be found within 1 to 20 metres (3 ft 3 in to 65 ft 7 in) of the earths surface. Strip mining is the most common technique used for extracting shallow bauxite. This process involves removing the vegetation, top soil, and overburden to expose the bauxite ore. The overlying soil is typically stockpiled in order to rehabilitate the mine once operations have finished. During
1190-401: The world's bauxite reserves. As of 2010 , approximately 70% to 80% of the world's dry bauxite production is processed first into alumina and then into aluminium by electrolysis . Bauxite rocks are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical, and refractory. Bauxite ore is usually heated in a pressure vessel along with
1225-575: Was responsible for killing all life in the Marcal River in Hungary after a spill occurred in 2010. When red mud dries, it turns into dust that can cause lung disease, cancer and birth defects. In the tropical regions of Asia, central Africa, South America and northern Australia, there has been an increase of bauxite mines on traditional and indigenous lands. This has resulted in a number of negative social impacts on local and indigenous peoples. In
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