LABORATORY EVALUATION OF THE USE OF ALKALINE COVERS TO PREVENT ACID MINE DRAINAGE

LABORATORY EVALUATION OF THE USE OF ALKALINE COVERS TO PREVENT ACID MINE DRAINAGE Acid mine drainage (AMD) is a worldwide environmental problem. It is caused by the chemical oxidation process of materials containing sulfide minerals exposed to atmospheric conditions mediated by bacteria. Acidic waters generated in these environments can affect the quality of water bodies. Prevention and remediation methodologies are applied in order to contain AMD. As an alternative for prevention, dry covers have been studied, because remediation usually means very high costs. The objective of this study was to evaluate the effectiveness of alkaline covers to control acid generation from uranium (U) rock mining waste using leaching column systems. For this purpose, cover systems containing neutralizing agents such as red mud, limestone and lime were applied. Samples of waste rock and water were collected from the Osamu Utsumi mine, in Caldas, Minas Gerais. The waste rock, lime, limestone and red mud were subjected to chemical and mineralogical analyses. Seven leaching columns were installed for the kinetic tests: C1 (waste rock), C2 (waste rock + red mud cover), C3 (waste rock + limestone cover), C4 (waste rock + lime cover), COB2 (red mud cover), COB3 (limestone cover) and COB4 (lime cover). The leached samples were monitored for 100 days. The results showed that lime and red mud have a greater neutralizing potential. However, these neutralizing agents have the disadvantage of introducing soluble material into the leachate. Therefore, associated with alkaline industrial waste recycling, the parameters evaluated indicate the use of a mixture of red mud with disposal waste rock as a viable alternative to restrict AMD generation.