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 \xD0\xB8 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. |