Carbochlorination of Aluminum from Non-Bauxite Sources

There has been increased interest in the United States in developing the technology to recover aluminum from non-bauxite sources stemming from a need to develop domestic aluminum sources.^{1, 2} Several domestic sources of aluminum have been defined by the U.S. Bureau of Mines;³ the types and approximate tonnages of these are listed in Table I. Patterson and Dyni⁴ of the U.S. Geological Survey identified several additional non-bauxite sources of aluminum, including alunite (37% Al₂O₃), dawsonite (35% Al₂O₃), and coal ash (8–40% Al₂O₃). The U.S. Bureau of Mines has indicated that the future aluminum resources consist mainly of anorthosites, and has listed research on the recovery of alumina from kaolin, anorthite, and dawsonite as a major objective.⁵ It is also interesting to note that there has been a discussion of the importance of finding a method for processing lunar anorthite to produce construction materials for space.⁶ Research on recovering aluminum from non-bauxite sources in Minnesota was initiated due to an interest in total resource utilization by way of by-product recovery of the large potential source of plagioclase from the tailings of copper-nickel processing. The plagioclase contained in the Duluth gabbro deposit has a composition between albite (soda feldspar) and anorthite (lime feldspar) and coresponds closely to labradorite. The tailings contain about 65% plagioclase which can be separated by high-gradient magnetic separation to produce a concentrate containing more than 28% alumina with an iron content less than 0.5%.⁷