Aluminiumsulfat

Aluminiumsulfat, or aluminum sulfate, is an inorganic compound with the formula Al2(SO4)3. It typically forms a white, hygroscopic solid and readily dissolves in water, yielding acidic solutions. In aqueous solutions, aluminum ions hydrolyze to form gelatinous aluminum hydroxide, which acts as a coagulant to remove suspended particles.

Production and occurrence: Aluminum sulfate is produced by reacting aluminum hydroxide or alumina with sulfuric acid: 2 Al(OH)3 + 3 H2SO4 → Al2(SO4)3 + 6 H2O. It can also be obtained from processing of bauxite or alumina with sulfuric acid. In water, it behaves as a source of Al3+ and forms various hydroxy-sulfate species depending on pH.

Properties: The compound is highly soluble in water and forms polymeric hydroxy-sulfate species in solution. It is typically encountered as a white crystalline or granulated solid and is used in concentrated solutions for industrial applications. As a Lewis acid, it provides aluminum ions that drive coagulation and flocculation processes in solution.

Applications: The principal use is as a coagulant in municipal and industrial water and wastewater treatment, where it neutralizes charges on colloids and promotes sedimentation. In the paper industry it is used as a sizing and retention agent to improve drainage and retention of fines. It also has historical uses as a mordant in dyeing and in leather tanning.

Safety and environmental aspects: Aluminum sulfate is corrosive to skin and eyes and can cause irritation on contact. Ingestion or inhalation should be avoided. In the environment, releases of sulfates can affect aquatic systems; handling and disposal should follow appropriate regulations.

---