In a circular economy concept, where more than 300 million tons of mining and quarrying wastes are produced annually, those are valuable resources, supplying metals that are extracted today by other processes, if innovative methods and processes for efficient extraction of these elements are applied. This work aims to assess microbiological and chemical spatial distribution within two tailing basins from a tungsten mine, using a MiSeq approach targeting the 16S rRNA gene, to relate microbial composition and function with chemical variability, thus, providing information to enhance the efficiency of the exploitation of these secondary sources. The tailings sediments core microbiome comprised members of family Anaerolineacea and genera Acinetobacter, Bacillus, Cellulomonas, Pseudomonas, Streptococcus and Rothia, despite marked differences in tailings physicochemical properties. The higher contents of Al and K shaped the community of Basin 1, while As-S-Fe contents were correlated with the microbiome composition of Basin 2. The predicted metabolic functions of the microbiome were rich in genes related to metabolism pathways and environmental information processing pathways. An in-depth understanding of the tailings microbiome and its metabolic capabilities can provide a direction for the management of tailings disposal sites and maximize their potential as secondary resources.

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Medium and highly sulfidic tailings are high-volume wastes that can lead to severe environmental damage if not properly managed. Due to the high content of sulfide minerals, these tailings can undergo weathering if put in contact with oxygen and water, generating acid mine drainage (AMD). The moderate-to-high sulfide content is also an important technical limitation for their implementation in the production of construction materials. This paper reviews the use of sulfidic tailings as raw material in construction products, with a focus on cement, concrete, and ceramics. When used as aggregates in concrete, this can lead to concrete degradation by internal sulfate attack. In building ceramics, their implementation without prior treatment is undesirable due to the formation of black reduction core, efflorescence, SOx emissions, and their associated costs. Moreover, their intrinsic low reactivity represents a barrier for their use as supplementary cementitious materials (SCMs) and as precursors for alkali-activated materials (AAMs). Nevertheless, the production of calcium sulfoaluminate (CSA) cement can be a suitable path for the valorization of medium and highly sulfidic tailings. Otherwise difficult to upcycle, sulfidic tailings could be used in the clinker raw meal as an alternative raw material. Not only the SO3 and SiO2-rich bulk material is incorporated into reactive clinker phases, but also some minor constituents in the tailings may contribute to the production of such low-CO2 cements at lower temperatures. Nevertheless, this valorization route remains poorly explored and demands further research.

Mining and quarrying waste is the second largest waste stream in Europe. Sulfidic ore processing residues (tailings) pose a large challenge, because they contain hazardous metal(loid)s and because they can lead to acid mine drainage. However, mine tailings also contain valuable base, precious, and critical metals, which can be used in different technological applications, as well as silicates and clay minerals that offer possibilities for use in building materials. In the present study, the potential use of mine tailing material, from the inactive Pb-Zn mine of Plombières (Eastern Belgium), in 3 ceramic products (roof tiles, blocks, and pavers) was assessed, taking into account production parameters, product quality, and environmental performance. After a detailed physical, mineralogical, and chemical characterization of the mine tailing material and the original raw materials, different mixtures were prepared on a lab scale, in which primary raw materials (e.g., clay and sand) were replaced by 5, 10, or 20 wt% of the fine tailing material. The technical, chemical, and aesthetical properties of each ceramic body were assessed, as well as their environmental performance, considering a 2 nd life scenario, where shaped building materials are demolished and recycled as aggregates. High additions of tailing material in clay roof tiles (10 and 20 wt%) and clay blocks (20 wt%) resulted in technical and aesthetical problems. On the contrary, paver mixtures containing 10 and 20 wt% of tailing material showed better technical properties and satisfying chemical and aesthetical characteristics.