TWO APPROACHES FOR REDUCING WASTED ‘RED MUD’: POSSIBILITY OF UPGRADING BAUXITE AND THE ‘RED MUD’

Red mud is one of the most difficult solid wastes to be reduced and/or recycled from old days in Japan, and many papers have been published for the treatment. However, few commercial plants have operated until now owing to the high cost and low effectiveness of the processing. Our approach can be divided into two categories, one is reducing the amount of red mud by upgrading bauxite and the other one is upgrading the red mud itself for utilization as a raw material of cement and/or iron & steel making industries. To achieve the former objective, we made detail investigation on the existent state of the bauxite ore of Gove mine, Australia, which was imported in Japan at the largest amount. We have found that gibbsite phase, g-Al(OH)₃, in the ore was covered by kaolinite phase, Al₂Si₂O₅(OH)₄, and had the possibility to reduce kaolinite content by applying selective surface grinding. To achieve the latter objective, to upgrade the red mud itself, we applied several stages of wet high intensity magnetic separation in a circuit and found the possibility to improve iron content with relatively high recovery. Titanium is one of the major impurities to be reduced from red mud, the existent state (involving mineral species), and the behavior in the circuit of magnetic separation was also clarified.