Hydrous ferric oxides
Hydrous ferric oxides, also called hydrous iron oxides and iron oxide-hydroxides are hydrous oxide inorganic compounds.
They may be found as a class of minerals that form from the weathering of minerals that contain iron and hydroxides, and weakly bound water. They are poorly crystalline, highly porous and have large surface areas. They usually occur as very small particles and tend to become more crystalline as they age because they are thermodynamically unstable. They have an affinity for organic and inorganic pollutants, which has led to an interest in using them as sorbents for the treatment of effluents and polluted water. Hydrous iron oxides include ferrihydrite, akaganéite, feroxyhyte, goethite, lepidocrocite and limonite.
They may also be precipitated in highly porous poorly crystaline or amorphous forms and therefore be good adsorbents used eg in water treatment.
