Red Mud Minimization by Iron Removal

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9714594 Schlesinger The objective of this research is to demonstrate the use of partial reduction as a means of removing the iron from "red mud", produced in the purification of aluminum using the Bayer process. Red mud contains high ferric-oxide, resulting in its name, as well as significant percentages of alumina, soda, silica, lime and titania, and might prove a valuable source of these materials. Currently red mud is disposed of at sea or in shallow lagoons along ocean shores or river banks. Because of the less-hazardous nature of red mud, little research attention has been given to reducing the volume of disposed material or the recovery of its constituents. Several characteristics of red mud make the development of an economically viable treatment process difficult, e.g. the moisture content, the extremely fine particle size and the refractory nature of most of its constituents. One of the most challenging aspects lies in finding a way of separating the iron it contains (in the form of hematite). Several techniques have been attempted, but they have been unsuccessful because of their high energy requirements and because they produce a slag which is difficult to process further. This research is aimed at reducing the hematite to magetite or wustite, which are ferromagnetic and can be recovered by low-gradient magnetic separation processes. This would require lower furnace temperatures, reducing energy costs and minimizing interaction among the other constituents in the mud. The research program will focus on bench-scale reduction experiments varying the type of mud, reduction temperature and the choice and amount of reducing agent; quantitative process mineralogy techniques will be used to assess the degree of reduction achieved and to generate a characterization profile of U.S. red muds. A second focus involves demonstrating the use of low-gradient magnetic separation in recovering iron from the partially reduced materials. Recent advances in magnetic separation have shown promise in iron recovery from other fine-grained process wastes and their integration into a red mud treatment process will help create a viable alternative to present disposal and recovery techniques. ***