The ore which is purified by leaching process is:
Zinc blende
Bauxite
Calamine
Haematite
The correct option is: (B): Bauxite.
Bauxite is the ore that is purified by the leaching process, specifically the Bayer process. The Bayer process is used to extract aluminum oxide (alumina) from bauxite ore, which is the main source of aluminum metal. Let's justify why bauxite is purified by the leaching process:
Composition of Bauxite: Bauxite is a naturally occurring mineral that contains various impurities, including iron oxides, silica, titanium dioxide, and other elements. The primary component of bauxite is aluminum oxide (alumina).
Desired Product - Alumina: The primary goal of purifying bauxite is to extract alumina, which serves as a precursor for aluminum metal production. Alumina is a white powder that is rich in aluminum oxide (Al2O3).
Bayer Process - Leaching: The Bayer process is a hydrometallurgical method used to extract alumina from bauxite. In this process, crushed bauxite ore is mixed with a concentrated solution of sodium hydroxide (NaOH) at elevated temperatures and pressures. This mixture is then subjected to leaching, where alumina dissolves into the alkaline solution while other impurities remain insoluble.
Leaching Mechanism: The leaching process in the Bayer process involves a reaction between the sodium hydroxide solution and the alumina present in bauxite:
Al2O3 + 2NaOH → 2NaAlO2 + H2O
This reaction forms sodium aluminate, which is soluble in the alkaline solution, while the impurities such as iron oxides and silica remain as solids and can be separated.
Separation and Precipitation: After the leaching step, the solution is allowed to settle to separate the insoluble impurities from the soluble sodium aluminate solution. The sodium aluminate solution is then further processed to precipitate out pure alumina by controlling the pH and temperature of the solution.
Alumina to Aluminum Metal: The extracted alumina can be further processed to obtain aluminum metal through electrolysis in the Hall-Héroult process, which involves the reduction of alumina using electric current.
In summary, bauxite is purified by the leaching process, specifically the Bayer process, to extract alumina (aluminum oxide) from the ore. The leaching process involves the dissolution of alumina in a sodium hydroxide solution, while other impurities remain insoluble. This extracted alumina serves as a crucial precursor for the production of aluminum metal.
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