Sulfatjonen

Sulfatjonen, commonly called the sulfate ion, is the dianion of sulfuric acid with the chemical formula SO4^2−. In aqueous solution it behaves as a tetrahedral ion, with sulfur in the +6 oxidation state. Through resonance, the four S–O bonds share the negative charge, giving a stable, highly soluble ion that forms salts with many metal cations.

Sulfate occurs widely in nature. It is a major component of minerals such as gypsum (calcium sulfate dihydrate) and anhydrite, and it is abundant in seawater and many soils. It is produced in nature by the oxidation of sulfide minerals and can be released by volcanic activity and the decomposition of organic material. In the environment, sulfate can be transported over long distances in water and air and contributes to the overall sulfur cycle.

Chemically, sulfate salts are typically highly soluble in water; they are generally unreactive under normal conditions but participate in acid–base and complexation reactions. In biology, sulfate is essential for the synthesis of many biomolecules. Organisms use sulfate in sulfation reactions to modify proteins, carbohydrates, and xenobiotics, and certain microorganisms couple sulfate reduction to energy metabolism in anaerobic conditions.

Industrial use is extensive. Sodium sulfate is used in detergents, pulp and paper processes, and glass manufacturing; calcium sulfate is used as a building material (plaster) and soil conditioner; magnesium sulfate (Epsom salt) has medical and agricultural applications. Sulfates also occur as salts in many minerals and products (for example gypsum and epsomite).

Safety and environmental aspects: sulfate salts are of relatively low toxicity, but high concentrations in drinking water or wastewater can have laxative effects and contribute to water hardness. Atmospheric sulfate contributes to acid rain and related environmental impacts. See also sulfate-reducing bacteria.