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Tailings

Tailings are finely ground residues of extractive (mining) industries which are generated from the processes of crushing/milling and of separating the valuable fraction from the uneconomic/ undesirable fraction of an ore (also known as mineral beneficiation). They consist of ground rock and mineral beneficiation process effluents.

Their characteristics vary significantly and are mainly dependent on the ore mineralogy (e.g. sulfidic tailings, bauxite tailings, coal tailings, etc). According to the Raw Materials Scoreboard, the extractive industry generates the second-largest waste stream in the EU, a part of which is hazardous.
The handling of tailings usually involves storage at the surface in the form of piles or underground (backfill). Consequently, the disposal of tailings is of utmost importance since it’s connected to major environmental impacts, particularly in the case of abandoned mines. Acid mine drainage (AMD) is the most widespread problem associated with sulfidic tailings. More specifically, AMD is a liquid effluent, which is generated due to the oxidation of pyrite minerals and other sulfate metals upon exposure of tailings to air, water and microbial activities. The main features of AMD are extreme acidity (1<pH<3) with an enhanced concentration  of heavy metals.  Generally, it’s very difficult to prevent the exposure of tailings to air, water and bacteria and therefore to avoid the generation of AMD. As a result, remediation approaches have been developed that involve the neutralization and the detoxification of this acidic effluent in order to prevent the negative environmental impacts of AMD to soils and natural water receivers.
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tailings

In order to mitigate the potential environmental impacts associated with the disposal of tailings, the EU commission has deployed the Extractive Waste Directive along with the Seveso III Directive, which focuses on accident risks and the Best Available Techniques (BATs) on the management of tailings and waste – rock.  Furthermore, extractive wastes fall under the provisions of EU’s waste management legislation framework, which is based on a hierarchical approach: prevention, re-use, recycling, recovery, and disposal. However, the recovery of valuable metals from tailings has not been fully developed yet, for reasons of economic and technological feasibility and therefore it’s a major challenge.

The MSCA-ETN SULTAN project focuses on the remediation and reprocessing of sulfidic mining wastes both of abandoned and active mines and  is in line with the provisions of the EU’s waste management legislation. The scientific goal of the SULTAN team is to develop cutting-edge methodologies to assess the resource potential of the tailings in Europe, to recover valuable metals, detoxify and to design novel green construction materials from them. Can we achieve these goals? Stay tuned, more blogs are coming!

Sources and further reading

  • G. Naidu, S. Ryu, R. Thiruvenkatachari, Y. Choi, S. Jeong, and S. Vigneswaran, “A critical review on remediation, reuse, and resource recovery from acid mine drainage,” Environ. Pollut., vol. 247, pp. 1110–1124, 2019. https://doi.org/10.1016/j.envpol.2019.01.085
  • Bernd G. Lottermoser, Mine Wastes- Characterization, Treatment and Environmental Impacts, Springer- Verlag Berlin Heidelberg 2010. ISBN 978-3-642-12418-1

 

 

 

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