Aluminium Sulfate

About Aluminium sulfate

Aluminium sulfate, also known as cake alum or aluminium salt, is a chemical matter with the formula Al₂(SO₄)₃. It is applied in various industries, such as the wastewater treatment industry, water purification, and paper industry. Aluminium sulfate appears as white crystalline solid and is odorless. It is hygroscopic and hence, able to absorb and retain water from the surroundings. It is also water-soluble, non-volatile, and non-flammable. It is extremely acidic such that it can burn human skin and also corrodes metal. When dissolved in water, pH can be less than two.

Aluminium sulfate is dangerous if inhaled or swallowed. The inhalation will cause coughing and potentially shortness of breath. Eating or swallowing aluminium sulfate can cause severe irritation of the intestines and stomach. Ingestion will induce vomiting, nausea, and diarrhea. Upon contact with skin or eyes, it will cause irritation, redness, itching, and pain. Besides that, adding water to aluminium sulfate can cause sulfuric acid to form. Manufacturing Process  In industrial product, the synthesis of aluminium sulfate is carried out in several stages:  • Mixing aluminium hydroxide with sulfuric acid Sulfuric acid is fed into a heat-resistant and acid-resistant reaction vessel. Aluminium hydroxide is then added to the vessel and is heated to a high temperature of about 100°C to 130°C. The concentration of sulfuric acid added to the mixture must be high in order for the reaction to be efficient.  • Adding Nitric Acid into the vessel Recently, a more advanced method has been developed to increase the efficiency of aluminium sulfate production. This allows the reaction to be held at a lower temperature, shorter time, and can require a lower concentration of sulfuric acid without a heating source. Contrary to the method mentioned above, an additional product (nitric acid or hydrogen peroxide solution) has to be added to the reaction.  • Separate aluminium sulfate from water Concentrated aluminium sulfate solution is cooled and followed by evaporation to separate aluminium sulfate from water.

Manufacturing Process

In 1963, Carl introduced his discovery of a process for producing aluminum sulfate by reacting bauxite or aluminum oxide containing iron ore with sulfuric acid. The principle of the present invention is to increase the efficiency of the extraction process which can be used for materials other than bauxite such as kaolin. In 1981, Boisen devised a method for crystallizing a solution of aluminum sulfate so that it had the same granular size. This process uses an evaporation crystallization device

Water Treatment Industry

Aluminium sulfate is well known for wastewater treatment. Because of its non-toxicity, it is used in a water treatment reactor to purify drinking water. It is also used to maintain the stability of the lake or reservoir. Excess phosphorus in the lake water induces ‘booming algae’ which aluminium sulfate can combat this problem by reducing the phosphorus concentrations and also, maintaining the normal phosphorus concentration.

Agriculture Industry

Aluminium sulfate is used as a buffer solution for balancing of soil pH. The flower changes its color when the pH of the soil is different from the standard conditions. Gardeners even use aluminium sulfate to increase the acidity of the soil.

Other Applications

Aluminium sulfate is also used for waterproofing and to accelerate the setting of concrete. It is also used to produce antiperspirants, firefighting foaming, lubricating compositions, sizing paper, baking powder, molluscicide, material for fire retardant, catalyst, and decolorisation agent. Moreover, it is also applied as a coagulant to absorb the impurities which are removed as particulates via filtration. Aluminium sulfate is widely applied in the textile industry as well.