Sulfate
Overview
Sulfate is a polyatomic anion with the empirical formula SO4^2−. It consists of a central sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The sulfate ion carries a negative two charge and is the conjugate base of the bisulfate (or hydrogen sulfate) ion, HSO4−, which is the conjugate base of H2SO4, sulfuric acid.
Chemical Properties
Sulfate is a stable species in many environments, but can be reduced to sulfide by the process of respiration in microorganisms. Sulfate is also the product of oxidation of sulfide, as from pyrite (iron sulfide) by weathering or treatment with oxidizing agents. Commercial quantities of sulfates are prepared by this method: sulfur dioxide, made by combustion of sulfur, is oxidized to sulfur trioxide, which combines with water to make sulfuric acid.
Biological Role
In biological systems, sulfate ions serve many functions. Sulfate is involved in the metabolism of sulfur. It is released into the atmosphere by the burning of fossil fuels and the smelting of mineral ores that contain sulfur. The sulfate ion can be absorbed by plants and algae. It is present in dilute sulfuric acid, a strong acid, and in naturally occurring hot springs, where it is produced by the reaction of sulfur with water.
Industrial Applications
Sulfate is a common component of many minerals and chemical compounds. It is used in numerous industrial processes and is a major component of gypsum, a mineral used in construction. Sulfate is also used in the production of detergents, paper, and glass, and in the treatment of water and wastewater.
Environmental Impact
The environmental impact of sulfate is significant. It is a major contributor to acid rain, which can damage forests and acidify water bodies, leading to the death of aquatic life. Sulfate particles in the atmosphere also contribute to air pollution, which can cause respiratory problems in humans and animals.