Aluminium Sulphate Reaction With Water

When aluminium sulphate (chemical formula: Al2(SO4)3) is added to water, it undergoes a chemical reaction known as hydrolysis. Hydrolysis is a process in which a compound reacts with water to form new compounds.

The reaction between aluminium sulphate and water can be represented by the following chemical equation:

Al2(SO4)3 + 6H2O → 2Al(OH)3 + 3H2SO4

In this reaction, the aluminium sulphate dissociates into its constituent ions in water. The aluminium ion (Al3+) combines with water molecules to form aluminium hydroxide (Al(OH)3). The sulfate ion (SO42-) combines with hydrogen ions (H+) from water to form sulfuric acid (H2SO4).

The resulting solution turns acidic due to the formation of sulfuric acid. The aluminium hydroxide formed is insoluble in water and forms a gelatinous precipitate. This precipitate can trap suspended particles in water, making them easier to remove through filtration or sedimentation.

Aluminium sulphate is commonly used as a coagulant in water treatment plants for this reason. It helps to clarify water by removing impurities and suspended particles. However, excessive use of aluminium sulphate can lead to increased levels of aluminum in drinking water, which is a health concern. Therefore, it is important to regulate the amount of aluminium sulphate used in water treatment processes.