EVALUATION OF THE CAPACITY OF CEMENT KILN DUST AND FLY ASH FOR THE NEUTRALIZATION OF ACIDIC MINE TAILINGS

The production of acid mine drainage (AMD) is considered as a serious problem for the mining industry. The oxidation of sulphide minerals causes the production of sulfuric acid resulting in a decrease in pH. This decrease causes the mobilization of metals; these very high concentrations may be a threat to the receiving environment. Abandoned Kettara Mine (Central Jebilet, Morocco), that has been chosen as a pilot site contains 3Mt of the residues that generate acidic leachates with a pH between 2.9 and 1.5 (Nfissi et al., 2011). The acidification potential (AP) of that is between 51 and 453kg CaCO3/t while that the net of neutralization potential (NNP) ranges from -453 to -22.5 Kg CaCO3/t (Hakkou et al., 2008a). In order to control the AMD in this mine, we opted a protocol based on the use of cement kiln dust (CKD) from the Lafarge cement of Bouskoura (Region of Casablanca) and fly ashes (FA) of the thermal power plant of Jorf Lasfar at El Jadida city (Coastal city 90km south-west from Casablanca). The main objective of this study is to enhance the value of these industrial by-products considered as wastes for rehabilitation of mine sites. A mineralogical and physico-chemical characterization of these materials has been done and supplied promising results as to their effectiveness in stabilizing tailings. Indeed, these are highly alkaline with a high net neutralizing capacity which is in the order of 900.63 kg CaCO3/t CKD and 243.75 kg CaCO3/t for FA. CKD and FA have a high neutralization potential and would constitute the main component of amendment alkali and/or covering that may reduce greatly the effects of DMA in this semi-arid climate mine and in other similar sites.