selenates

Selenates are salts of selenic acid that contain the selenate anion SeO4^2-. They are the selenium analogues of sulfates and are typically formed by combining a metal cation with the SeO4^2- ion. Common selenates include sodium selenate Na2SeO4, potassium selenate K2SeO4, ammonium selenate (NH4)2SeO4, and magnesium selenate MgSeO4. The selenium in SeO4^2- is in the +6 oxidation state, and the anion adopts a tetrahedral geometry. Selenates are generally white, odorless solids that are highly soluble in water; in aqueous solution they exist predominantly as SeO4^2- over a wide pH range.

Selenates can be prepared by oxidation of selenium compounds or by neutralization of selenic acid with suitable bases; they can also arise naturally in oxidized selenium-bearing ore deposits and in selenium-rich waters.

In applications, sodium selenate is the most widely used selenate salt, notably as a dietary selenium source in animal feeds and as a trace-element fertilizer. Selenates can be reduced to selenite (SeO3^2-) or to elemental selenium under reducing conditions, a factor relevant to processing and environmental chemistry.

Safety: selenium compounds can be toxic at elevated concentrations and must be handled with appropriate care to avoid ingestion or inhalation. Waste should be managed according to hazardous-substance regulations.