Iodine Production

Iodine is extracted from water and oil deposits as well as from mother waters of saltpeter production. Mineralized water contains 0.001-0.01% iodine in iodides. It is acidified by sulphuric or hydrochloride acid until reaching pH 2.5-3.5 and then is treated by Cl₂ or NaNO₂ solution for extracting elemental iodine. The extracted element is absorbed by activated coal or anionites from which it is blown out by air (air desorption method). Iodine from the coal is washed out by NaOH obtaining NaI и NaIO₃ and from anionites it is extracted by mixture of Na₂SO₃ and NaCl. Elemental iodine is extracted from the solutions with 2-3% NaI exposing them to H₂SO₄ and some oxidizer such as chlorine. In air desorption method the iodine-containing air is mixed with SO₂ which, in the presence of humidity, makes mixture of HI (approx. 10%) and H₂SO₄, from which iodine is isolated. It is then refined by sublimation or smelting under H₂SO₄ layer.

Saltpeter mother waters, which contain NaIO₃, are treated by SO₂. Iodine may be recovered also from seaweeds ashes.