How is alumina obtained from bauxite? Also, write the reqired balanced chemical reaction for the same.
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Solution!!
Alumina is obtained from bauxite during the extraction of aluminium in Bayer's process. Aluminum is extracted from its main ore bauxite Al₂O₃.2H₂O.
Bauxite is grinded finely and heated to remove volatile impurities. It is then heated under pressure with concentrated caustic soda solution for 2 to 8 hours at 140°C to 150°C (leaching).
Al₂O₃.2H₂O + 2NaOH → 2NaAlO₂ + 3H₂O
Bauxite dissolves and forms sodium meta aluminate because of the amphoteric nature of aluminium, leaving behind insoluble impurities called red mud. Red mud is removed by filtration.
On diluting sodium meta aluminate with water and cooling to 50°C, it gets hydrolysed to give aluminium hydroxide as a precipitate.
NaAlO₂ + 2H₂O → NaOH + Al(OH)₃ ↓
The precipitate is filtered, washed, dried and ignited at 1000°C to get alumina (Al₂O₃).
2Al(OH)₃ → Al₂O₃ + 3H₂O
Answer:
==>First, after the bauxite is crushed, washed and dried, it is dissolved with caustic soda at high temperatures. ... Finally, the aluminum hydroxide is washed of any remaining caustic soda and heated to remove excess water. After this process, alumina (aluminum oxide) emerges as a fine white powder.
==>The solution of Sodium aluminate is filtered cooled and neutralised by passing CO2 gas and hydrated Al2O3 is precipitated by seeding. 3. Hydrated alumina is filtereds dried and heated to get pure alumina (Al2O3).
Explanation:-
==>Bauxite ore is the world’s primary source of aluminum. The ore must first be chemically processed to produce alumina (aluminum oxide). Alumina is then smelted using an electrolysis process to produce pure aluminum metal. Bauxite is typically found in topsoil located in various tropical and subtropical regions. The ore is acquired through environmentally responsible strip-mining operations. Bauxite reserves are most plentiful in Africa, Oceania and South America. Reserves are projected to last for centuries.
Take-Away Facts
Aluminum must be refined from ore
Although aluminum is the most common metal found on Earth (totaling 8 percent of the planet’s crust), the metal is too reactive with other elements to occur naturally. Bauxite ore, refined through two processes, is the primary source of aluminum.
Land conservation is a key industry focus
An average of 80 percent of the land mined for bauxite is returned to its native ecosystem. Topsoil from the mining site is stored so it can be replaced during the rehabilitation process.
Reserves will last for centuries
Although demand for aluminum is increasing rapidly, bauxite reserves, currently estimated at 40 to 75 billion metric tons, are projected to last for centuries. Guinea and Australia have the two largest proven reserves.
A wealth of bauxite reserves
Vietnam may hold a wealth of bauxite. In November 2010, the prime minister of Vietnam announced the country’s bauxite reserves may total up to 11 billion tons.
Bauxite 101
Bauxite ore is the world’s main source of aluminum
Bauxite is a rock formed from a reddish clay material called laterite soil and is most commonly found in tropical or subtropical regions. Bauxite is primarily comprised of aluminum oxide compounds (alumina), silica, iron oxides and titanium dioxide. Approximately 70 percent of the world’s bauxite production is refined through the Bayer chemical process into alumina. Alumina is then refined into pure aluminum metal through the Hall–Héroult electrolytic process.
Mining bauxite
Bauxite is usually found near the surface of terrain and can be strip-mined economically. The industry has taken a leadership role in environmental conservation efforts. When the land is cleared prior to mining, the topsoil is stored so it can be replaced during rehabilitation. During the strip-mining process, bauxite is broken up and taken out of the mine to an alumina refinery. Once mining is complete, the topsoil is replaced and the area undergoes a restoration process. When the ore is mined in forested areas, an average of 80 percent of the land is returned to its native ecosystem.
Production and reserves
More than 160 million metric tons of bauxite are mined each year. The leaders in bauxite production include Australia, China, Brazil, India and Guinea. Bauxite reserves are estimated to be 55 to 75 billion metric tons, primarily spread across Africa (32 percent), Oceania (23 percent), South America and the Caribbean (21 percent) and Asia (18 percent). The United States has small amounts of bauxite ore located in Arkansas, Alabama and Georgia. However, very little mining is done in the United States today.
Looking forward: Continued improvement in environmental restoration efforts
Environmental restoration goals continue to advance. A biodiversity-restoration project under way in Western Australia provides a leading example. The goal: to reestablish the equivalent level of plant species richness in rehabilitated areas equal to the un-mined Jarrah forest. (A Jarrah forest is tall open forest. Eucalyptus marginata is the dominant tree.)
Les Baux, the Home of Bauxite
Bauxite was named after the village of Les Baux by Pierre Berthe. This French geologist found the ore in nearby deposits. He was the first to discover that bauxite contained aluminum.