Commercial coal production in the southern region of Brazil (comprising the Paraná, Santa Catarina, and Rio Grande do Sul states) has been occurring since the beginning of the twentieth century. Regarding the Santa Catarina coalfields, about 60% -65% of the ROM coal is discharged at dump deposits as waste. These wastes can lead to the formation of acid mine drainage (AMD), a source of ground and surface water pollution. One of the technologies used for preventing AMD consists of the alkaline additive method. Thus, the aim of this work was to study, at laboratory scale, the DAM control by blending coal waste with a metallurgical slag. A coal-tailing sample was collected from a coal mine, and the slag was obtained from a semi-integrated steel plant. Static tests were carried out by the acid-base account method to determine the balance between the acid-producing and acid-consuming (neutralizing) mineral components of the samples. Kinetic tests were conducted in humidity cells, following the ASTM D 5744-96 method, for a period of 80 weeks. The results showed that the coal tailing generates AMD. However, environmental problems can be minimized by mixing the coal waste with the metallurgical slag in 1:1 or 1:1.5 proportions. The kinetic experiments proved that, in this condition, the lixiviation presents a higher pH and a lower concentration of acidity, metals, and sulfate. Finally, it is possible to conclude that the blending slag in coal tailing deposits can be a viable alternative for DAM control in coal mining.

ResumoOs rejeitos gerados na mineração de carvão, sob condições atmosféricas e a possível presença de bactérias acidofílicas proporcionam a oxidação primária do sulfeto de ferro, formando sulfatos e ácido sulfúrico. Com a redução do pH da água, ocorre a mobilização de metais contidos no material, gerando a drenagem ácida de mina (DAM). A DAM causa um impacto nocivo na qualidade da água superficial ou subterrânea. Uma das tecnologias de prevenção da geração da DAM consiste no método de aditivos alcalinos. Assim, o objetivo do presente trabalho foi avaliar o controle da DAM pela mistura de rejeito de carvão com escória de aciaria elétrica do forno panela. A metodologia utilizada baseou-se nos ensaios estáticos e ensaios cinéticos. Os resultados demonstram que o rejeito de carvão gera DAM. Contudo os problemas ambientais podem ser em grande parte resolvidos pela mistura do rejeito com a escória na proporção acima de 10:10. Os ensaios cinéticos demonstram que, nessa condição, ocorre aumento do pH e redução do potencial redox e sulfatos na água lixiviada. Desta forma, a disposição conjunta de escória de aciaria elétrica do forno panela com rejeito de carvão é uma alternativa viável para o controle da geração de DAM em minerações de carvão. Abstract The waste generated in coal mining, under atmospheric conditions and the possible presence of acidophilic bacteria provides the primary oxidation of iron sulfide, forming sulfates and sulfuric acid. With the reduction of the water pH, the mobilization of metals contained in the material occurs, generating acid mine drainage (AMD). The AMD causes an adverse impact on surface or groundwater quality. One of the technologies to prevent the AMD is the alkaline additives method. The objective of this study was to evaluate the AMD control by mixing tailings with the ladle slag of electric steelmaking. The used methodology was based on static tests and kinetic assays. The results demonstrate that coal tailings generates AMD. However, the environmental problems can be largely solved by mixing the waste with the slag in the ratio of 10:10. The kinetic experiments demonstrate that, in this condition, there is an increase of pH and a reduction on the redox potential and in the sulphate in the leach water. Thus, the combined disposal of ladle slag of electric steelmaking with coal waste is a viable alternative to control the generation of AMD in coal mining.

Commercial coal production in the southern region of Brazil (comprising the Paraná, Santa Catarina, and Rio Grande do Sul states) has been occurring since the beginning of the twentieth century. Regarding the Santa Catarina coalfields, about 60% -65% of the ROM coal is discharged at dump deposits as waste. These wastes can lead to the formation of acid mine drainage (AMD), a source of ground and surface water pollution. One of the technologies used for preventing AMD consists of the alkaline additive method. Thus, the aim of this work was to study, at laboratory scale, the DAM control by blending coal waste with a metallurgical slag. A coal-tailing sample was collected from a coal mine, and the slag was obtained from a semi-integrated steel plant. Static tests were carried out by the acid-base account method to determine the balance between the acid-producing and acid-consuming (neutralizing) mineral components of the samples. Kinetic tests were conducted in humidity cells, following the ASTM D 5744-96 method, for a period of 80 weeks. The results showed that the coal tailing generates AMD. However, environmental problems can be minimized by mixing the coal waste with the metallurgical slag in 1:1 or 1:1.5 proportions. The kinetic experiments proved that, in this condition, the lixiviation presents a higher pH and a lower concentration of acidity, metals, and sulfate. Finally, it is possible to conclude that the blending slag in coal tailing deposits can be a viable alternative for DAM control in coal mining.