Recovery of alumina from anorthosite by an HC1-F-gas sparging crystallization process

"The Bureau of Mines is investigating the recovery of alumina from domestic nonbauxitic resources including anorthosite. The United States has large reserves of anorthosite, but its aluminum content is less than 50 pct soluble in acid, unless a source of fluoride is added to the acid. A flowsheet that includes leaching with hcl and fluoride followed by crystallization of alcl3.6H20 from the pregnant liquor by hcl gas injection was designed. Approximately 90 pct of the aluminum values were recovered from the anorthosite when a ratio of 0.14 Mole of fluorine per mole of aluminum was used. Sodium chloride is cocrystallized with the alcl3.6H20 but is removed by water washing of the al2o3 product. A material balance is given based on results of laboratory studies of the unit operations." - NIOSHTIC-2NIOSHTIC no. 1000309