Aluminium sulfate, also known as cake alum or aluminum salt, is a chemical matter with the formula Al2(SO4)3. It is applied in various industries, such as waste water treatment industry, water purification and paper industry. Aluminum sulfate is an odorless white or off-white crystalline solid. It is hygroscopic, water soluble, non-volatile, non-flammable and extremely acidic.
Various Form of Alumminum Sulphate:
Alumnium sulphate Ferric – This forms contains about 1-3% of Ferric Oxide (Fe2O3).Aluminium sulphate Ferric is available in various forms
Alumnium sulphate Non-Ferric – This forms contains only 0.01%(max) of Ferric Oxide (Fe2O3). Aluminium sulphate Non- Ferric is available in various forms.
Generally, aluminum sulfate can be synthesized by mixing aluminum hydroxide, Al(OH)3. The latter reacts with sulfuric acid, H2SO4 and produce aluminium sulphate. In industrial scale, the production of aluminum sulfate is carried out in several stages:
1. Mixing aluminum hydroxide with sulfuric acid
Sulfuric acid is fed into the reaction vessel which is heat resistant and acid resistant. Then aluminum hydroxide is added to the vessel and heated. However, the aluminum sulfate manufacturing methods above requires high temperature (about 100°C to 130°C) and takes more time to produce (about 10 minutes to 2 hours) which makes it less efficient. Further, to increase the efficiency, high concentration of sulfuric acid as the reactant is necessary in this process.
2. Adding Nitric Acid into the vessel
Recently, a more advanced method has been developed to increase the efficiency of aluminum sulfate production, which can be held at a lower temperature, shorter time, and lower concentration of sulfuric acid without using a heating source. In this process, another compound is added to the reaction, which is nitric acid or hydrogen peroxide solution.
3. Separate aluminum sulfate from water
The product is obtained from the reaction vessel is concentrated aluminum sulfate diluted in water. To separate aluminum sulfate from water, the solution is cooled and is followed by evaporating process.