Co-disposal of industrial wastes to obtain an inert material for environmental reclamation

The present work deals with the treatment of red mud from Eurallumina Bayer plant with gypsum, in order to obtain an inert which might be disposed wit hout risk. The proposed process has particular concern in the local contest in which the Bayer plant is located. In fact, some power plants or fluorid e production plants, that are present nearby the Eurallumina plant, might b e economic sources of gypsum. Moreover, the inert material resulting from t he proposed process should be disposed in the old mine sites, also present in the same area, and than re-vegetated, thus effectively contributing to a n environmental reclamation of this territory. The present work compares the characteristics of effluents obtained by leac hing with water, beds of either red mud coming from the thickening filters of the Bayer plant (RMF) or from the holding ponds (RMP), or their mixtures with gypsum. The results obtained up to now show that the process is able to lower pH at values near 9, which is stable to further leaching runs. Also the physical characteristics of the resulting material are enhanced, in terms of both p article size distribution and hydraulic permeability. The addition of 10% s andy soil is sufficient to give permeability in the order of 10(-4) cm/s, w hich is typical of sandy soil.