Potential use of scheelite mining residue in landfill cover systems

ABSTRACT

ABSTRACT: The use of mining residues within production chains, such as civil construction, is an important environmental solution for the management of mining activities. Researchers have shown that different types of mining residues can be incorporated into some types of geotechnical works, fulfilling the function of hydraulic barrier. In this scenario, the use of scheelite residue in landfill works could be an environmentally sustainable solution for this material. This work aimed to evaluate the technical viability of using scheelite mining residues as a compacted coating with hydraulic barrier function in waste landfill covering systems. For this, samples of fine and coarse residues generated during the scheelite processing were collected at the Brejuí Mine, in Currais Novos (Rio Grande do Norte). Subsequently, four materials were defined to be studied, one composed exclusively by the fine residue (F100) and three others formed by mixing the two collected residues (F75G25, F50G50, and F25G75). After that, physical characterization, compaction, hydraulic conductivity tests on flexible wall permeameters, X-ray Flourescence Spectroscopy/X-ray Powder Diffraction and Scanning electron microscope were performed on each sample. As a result of the tests, the saturated permeability values obtained for F100 and F75G25, being 2.18x10⁻⁸ and 7.07x10⁻⁸ m.s, respectively, comply with the requirements of international standards, and, thus, proved to be viable for the intended application as hydraulic barrier in landfill covering. As for the other composites, although they have not been successful in their intended use, they could be applied for other purposes within a waste landfill, as regularization and/or protection layers. The results obtained demonstrate the technical viability of the intended use of the material.

Keywords:
cover system; landfill; mining residue; sustainability; hydralic conductivity