Leaching of iron from Bauxite (experiment)

Aim

Leaching kinetics for removal of iron from low grade bauxite (Gibbsite) with HCl acid.

Apparatus required

1. Beakers 
2. Conical flask
3. Ultrasonic resonance spectrophotometer

Chemicals required

1. Gibbsite ore
2. $1$N HCl acid 
3. distilled water

Theory and principle of the experiment

Bauxite ores include minerals such as Gibbsite (Al$_2$O$_3$.3H$_2$O), Boehmite ($\gamma$ - Al$_2$O$_3$.3H$_2$O), Diasporite ($\alpha$ - Al$_2$O$_3$.H$_2$O) and Alumina (Al$_2$O$_3$) and higher concentration of impurities such as iron oxides and silica. Bauxite ore having high iron content is also used as starting material for the production of aluminium, once the removal of iron is achieved. Favorable bauxite ore will not have high contents of impurities such as iron oxides and silica. The removal of iron is important for two reasons. Low iron bauxite  having less than about $2\%$ Fe$_2$O$_3$ finds application in the production of refractory and removal of iron from bauxite prior to the Bayer's process reduces the disposal amount of red mud and provides high alumina content. 

In this experiment we use Hydrochloric acid to leach out the iron completely, given by the reaction 

Fe$_2$O$_3$ $+$ 6HCl $\longrightarrow$ 2FeCl$_3$ $+$ 3H$_2$O

Procedure and Observation.

1. A calculated amount of the ore was taken in the beaker.
2. $10$ ml of HCl and $90$ ml of distilled water was added in the beaker.
3. Different concentration ratios of HCl and water were added to different beakers. They were added to different beakers. They are left to react for some time.
4. This series of solutions were taken to a spectrophotometer and the absorbance of each solution was measured.

Results

HCl leached Fe at a higher concentration more effectively.

Precautions

Standard safety protocols apply for handling acids and use of spectrophotometer.