Question

What is the use of Bayer’s process in leaching?

Answer 1

Hint: As we know that the Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and this process of refining and extracting aluminium from ores was developed by Carl Josef Bayer, hence named as Bayer’s process. So here we have to explain the use of Bayer’s process in leaching.

Complete answer:
Let us first discuss about Bayer’s process followed by use of Bayer’s process in leaching as follows:-
-Bayer’s process: It is the principal industrial process of refining bauxite to produce alumina (aluminium oxide). Bauxite is the most important ore of aluminium and it contains only 30 to 60 percent of aluminium oxide whose chemical formula is . The rest is a mixture of silica, variety iron oxides and titanium dioxide. This must be purified before it can be refined to aluminium metal.
-So we can say that Bayer’s process is used for leaching of aluminium metal and this process takes place as follows:-
The extraction process converts the aluminium oxide contained in the ore to soluble sodium aluminate as shown below:-
$A{{l}_{2}}{{O}_{3}}~+\text{ }2\text{ }NaOH\text{ }\to \text{ }2\text{ }NaAl{{O}_{2}}~+\text{ }{{H}_{2}}O$
Now the alkaline solution was cooled and treated by bubbling $C{{O}_{2}}$ gas through it i.e., a method by which aluminium hydroxide precipitates as follows:-
$2\text{ }NaAl{{O}_{2}}~+\text{ }3\text{ }{{H}_{2}}O\text{ }+\text{ }C{{O}_{2}}~\to \text{ }2\text{ }Al{{\left( OH \right)}_{3}}~+~N{{a}_{2}}C{{O}_{3}}$
Lastly pure aluminium oxide is produced from aluminium hydroxide by heating it at very extreme temperature in rotary kilns or fluid flash calciners. This process is shown below:-
$2~Al{{\left( OH \right)}_{3}}~\to ~A{{l}_{2}}{{O}_{3}}~+\text{ }3~{{H}_{2}}O$.
-So from the above data we can say that Bayer’s process is used for leaching of aluminium.

Note:
-Remember that when bauxites have more than 10% silica then the Bayer’s process becomes uneconomic as the formation of insoluble sodium aluminium silicate takes place which reduces yield and hence another process must be chosen.
-Also understand the chapter extraction of metals and metallurgy to solve these types of questions.