Developments in chemical separation of iron ore

Major impurity elements in iron ore are silicon, aluminum, phosphorus, and sulfur. Often, a chemical separation is the only method able to remove phosphorus from iron ores. Phosphorus can occur as phosphorus-containing minerals (e.g., apatite) and being finely dispersed in hematite in oolitic ironstones or in goethite in goethite–hematite banded iron formation ores. An acid leach can remove phosphate present as discrete minerals and associated with hematite in oolitic ironstones. With goethitic ores, a heating treatment before a caustic or acid leach is necessary to make the phosphorus accessible to chemical separation. The amount of phosphorus removed increases with an increasing heating temperature up to 1300 °C. Silica, alumina, and sulfur usually are removed along with the phosphorus.