THE TREATMENT AND UTILIZATION OF RED MUD: A PRODUCT OF BAYER PROCESS

Andrejcak, M., Soucy, G. and Forté, G.

Metal production generates various forms of by-products. Disposal of these by-products can not only represent a problem of economics (high-cost for disposal and maintenance) but also an ecological problem (possible environment contamination). Therefore, there is now a major effort being made towards by-products treatment and recycling of its valuable components. Red mud and Fe-Ti slag are by-products of alumina and titania production, respectively. The following paper presents a review of red mud treatment patents, and some results of recent research work, the main purpose of which was to find a suitable method for the economical treatment of a mixture of red mud and Fe-Ti slag. Special attention has been given to a method developed for the recovery of valuable red mud components. This process involves the selective leaching of the ‘wastes’ mixture (red mud + Fe-Ti slag) by direct sulphuric acid contact, followed by hydrometallurgical, thermal or other kinds of processing, to recover valuable species, such as Fe2O3, TiO2, Al2O3 and Na2O. X-ray diffraction, TGA-DTA/DSC, ICP-mass spectroscopy and scanning electron microscopy techniques have also been used to determine physical, chemical and mineralogical characteristics of the red mud and the Fe-Ti slag. Thermodynamic values of the proposed chemical system (red mud + Fe-Ti slag) are also presented. FactSageTM 5.2 software was used to create E-pH diagrams. Finally a process flowsheet for valuable species recovery is proposed.