Tratamento de drenagem ácida de minas mediante coagulante orgânico : estudo do lodo formado

Abstract

Acid mine drainage (AMD) is an environmental problem arising from coal mining activity, since it is responsible for reaching the environment through soil leaching and water contamination. This problem has been the subject of studies by environmental entities that, through research and treatment and control methods, seek to mitigate the problem. Thus, the present work aims to treat AMD through the neutralization/precipitation method, using quicklime to control and adjust the pH and the TANFLOC-SG coagulant, an organic polymer responsible for sedimenting the particles in suspension in the solution. In addition, to study the behavior of the organic coagulant during the treatment in order to verify the effects of order and inversion in the addition of chemical reagents on physicochemical parameters such as pH, electrical conductivity, total dissolved solids (TDS), dissolved oxygen (DO) and concentration of iron ions pre and post treatment of AMD. The use of the TANFLOC-SG + calcium hydroxide dosage increased the pH from 3.01 to 8.81 and decreased the turbidity from 36.3 (NTU) in the crude sample to 6.05 in the treated sample, while the electrical conductivity did not suffer major variations, regardless of the order of addition and even in relation to the untreated sample, with conductivity values of 3.71 mS/cm in the treated sample, 4.47 mS/cm in the crude AMD and 5.61 mS/cm in the effluent treated only with the coagulant. As for dissolved oxygen, the value found in the previously homogenized crude AMD effluent was 7.05 ppm and, after treatment with TANFLOC-SG + calcium hydroxide, 3.5 ppm, while it was 5.61 ppm for the sample only with TANFLOC–SG. Finally, in view of the study on the composition of the sludge, possible applications and the improvement of some parameters, the use of the organic coagulant generated a sludge with a specific mass of 1.118 g/cm³ and, together with quicklime, of 1.220 g/cm³, while treatments using aluminum sulfate generate sludge with a specific mass of approximately 2.54 g/cm³. Aiming at industrial use, it is necessary to carry out the X-Ray diffraction technique in order to identify the oxide compounds and forms of iron present in the sludge for later beneficial use.