Aluminium sulfate

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  Aluminium sulfate
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  Aluminum sulfate floc in lake sediment

Aluminium Sulfate

Aluminium sulfate is a chemical compound with the formula Al_(SO_)_. It is a white crystalline solid that is soluble in water and is mainly used as a coagulating agent in the purification of drinking water and wastewater treatment plants, and also in paper manufacturing.

Chemical Properties

Aluminium sulfate is an ionic compound consisting of two aluminium cations (Al__) and three sulfate anions (SO___). It is commonly found in its hydrated form, Al_(SO_)_·nH_O, where n can vary. The most common hydrate is the octadecahydrate, Al_(SO_)_·18H_O.

Production

Aluminium sulfate is produced by reacting aluminium hydroxide with sulfuric acid. The reaction is as follows:

2 Al(OH)_ + 3 H_SO_ _ Al_(SO_)_ + 6 H_O

This reaction is exothermic and produces a solution of aluminium sulfate, which can be crystallized to obtain the solid form.

Uses

Water Treatment

In water treatment, aluminium sulfate is used as a coagulant to remove impurities by causing them to clump together into larger particles, which can then be removed by sedimentation and filtration. This process is known as flocculation.

Paper Manufacturing

In the paper industry, aluminium sulfate is used to improve the sizing of paper. It helps in the retention of fine particles and improves the paper's resistance to water.

Other Uses

Aluminium sulfate is also used in the textile industry for dyeing and printing fabrics, in the food industry as a firming agent, and in gardening to lower the pH of soil.

Safety

Aluminium sulfate is generally considered safe when handled properly, but it can cause irritation to the skin, eyes, and respiratory tract. It should be handled with appropriate protective equipment.

Related Pages

• Aluminium hydroxide
• Sulfuric acid
• Coagulation (water treatment)
• Flocculation