Acid mine drainage in the uranium mine at the Caldas Municipality (MG) has been occuring for over 20 years. This drainage has a pH of around 3.0 and contains metals and non-metals. The current acid water treatment uses lime to increase the pH and precipitates the contaminants before discharging the water into the environment. This procedure generates a sludge that is currently disposed into the mine pit which is flooded with acidic water. The present study aims at the characterization of 3 different samples, identified as Lama Antiga (old sludge), Lama da Cava (pit sludge) and Lama Fresca (fresh sludge), by using the TGA/DTA, electron microprobe, standard classification procedures NBR 10005 and NBR 10006. The characterization focused on determining the morphological phases and elemental composition in order to correlate them with the migration of contaminants. Ettringite, calcite and gypsum were identified as the majority phases. The sludges were classified as non-hazardous, but not inert. Studies on the uranium bioavailability showed that it is easily dissolved as most of this metal is present in the labile fraction. The radiological characterization showed that all samples are below the clearance value, according to PR-3.01/001.
Characterization of sludge; uranium; acid mine drainage
