Mine Tailings Research Articles

Profile of Bacterial Communities in Copper Mine Tailings Revealed through High-Throughput Sequencing.

Mine-tailing dumps are one of the leading sources of environmental degradation, often with public health and ecological consequences. Due to the complex ecosystems generated, they are ideal sites for exploring the bacterial diversity of specially adapted microorganisms. We investigated the concentrations of trace metals in solid copper (Cu) mine tailings from the Ovejería Tailings Dam of the National Copper Corporation of Chile and used high-throughput sequencing techniques to determine the microbial community diversity of the tailings using 16S rRNA gene-based amplicon sequence analysis. The concentrations of the detected metals were highest in the following order: iron (Fe) > Cu > manganese (Mn) > molybdenum (Mo) > lead (Pb) > chromium (Cr) > cadmium (Cd). Furthermore, 16S rRNA gene-based sequence analysis identified 12 phyla, 18 classes, 43 orders, 82 families, and 154 genera at the three sampling points. The phylum Proteobacteria was the most dominant, followed by Chlamydiota, Bacteroidetes, Actinobacteria, and Firmicutes. Genera, such as Bradyrhizobium, Aquabacterium, Paracoccus, Caulobacter, Azospira, and Neochlamydia, showed high relative abundance. These genera are known to possess adaptation mechanisms in high concentrations of metals, such as Cd, Cu, and Pb, along with nitrogen-fixation capacity. In addition to their tolerance to various metals, some of these genera may represent pathogens of amoeba or humans, which contributes to the complexity and resilience of bacterial communities in the studied Cu mining tailings. This study highlights the unique microbial diversity in the Ovejería Tailings Dam, including the discovery of the genus Neochlamydia, reported for the first time for heavy metal resistance. This underscores the importance of characterizing mining sites, particularly in Chile, to uncover novel bacterial mechanisms for potential biotechnological applications.

Compressive strength, durability, and resilient modulus of cement-treated magnetite and hematite iron ore tailings as pavement material

The extraction and processing of iron ore produce significant amounts of mine tailings, causing environmental problems that require storage in reservoirs or dams. Using these materials in construction helps minimize their adverse impacts. This study analyzed the geotechnical properties of Magnetite and Hematite iron ore tailings (MIOT, HIOT) from the Golgohar mine in Sirjan, Iran. Two IOTs were compacted using the Standard Proctor technique after being treated with 5, 7, and 9 % Portland cement. Following curing time, treated samples were tested at different stress levels for resilient modulus. Based on the results, to meet strength and durability requirements, cement-treated MIOT needs 9 % cement. Contrastingly, only 5 % of the cement for cement-treated HIOT met the criterion. The resilient moduli of untreated MIOT and HIOT materials heavily rely on the confining pressure, resulting in a minimal decrease in modulus by increasing deviatoric stress. The effect of cement on resilient modulus is more pronounced in high confining stresses than in low confining stresses in MIOT and HIOT materials. A comparison of different non-linear models showed that ‘Universal’ model is the best fit for laboratory results of cement-treated MIOT and HIOT materials, as it accounts for hardening and softening behavior.

Conceptual design of tailings dam and stability assessment

This work aims to present and discuss a conceptual project of mining tailings dam. Therefore, specific topics on tailings dams are visited and the characterization of materials constituting such structure is reviewed in the literature. Based on parameters available in the literature, a hypothetical dam was schematized and its stability was assessed via computational analysis (limit equilibrium and finite element flow analysis). Assessing eventual design changes (additional dam heightening) and hypothetical situations (collapses in the internal drainage), it is concluded that the schematic conceptual design presents itself viable and stable given the proposed geometry and the properties of materials considered. The importance of the internal drainage system for the dam´s stability was also identified.

Performance of stabilized copper mine tailings with freeze-thaw and wet-dry seasonal cycles

Approximately 3.44 billion tons of copper mine tailings (MT) were produced globally in 2018 with an increase of 45% from 2010. Significant efforts are being made to manage these tailings through storage facilities, recycling, and reuse in different industries. Currently, a large portion of tailings are managed through the tailing storage facilities (TSF) where these tailings undergo hydro-thermal-mechanical stresses with seasonal cycles which are not comprehensively understood. This study presents an investigative study to evaluate the performance of control and cement-stabilized copper MT under the influence of seasonal cycles, freeze-thaw (F-T) and wet-dry (W-D) conditions, representing the seasonal variability in the cold and arid regions. The control and cement-stabilized MT samples were subjected to a maximum of 12 F-T and 12 W-D cycles and corresponding micro-and-macro behavior was investigated through scanning electron microscope (SEM), volumetric strain (εv), wet density (ρ), moisture content loss, and unconfined compressive strength (UCS) tests. The results indicated the vulnerability of Copper MT to 67% and 75% strength loss reaching residual states with 12 F-T and 8 W-D cycles, respectively. Whereas the stabilized MT retained 39%–55% and 16%–34% strength with F-T and W-D cycles, demonstrating increased durability. This research highlights the impact of seasonal cycles and corresponding strength-deformation characteristics of control and stabilized Copper MT in cold and arid regions.

Reconstructing the Spill Propagation of the Aznalcóllar Mine Disaster

AbstractThe mine pond failure of Los Frailes (Aznalcóllar, Spain) was one of the most catastrophic mining-related disasters worldwide. Despite having been analysed from different disciplines, there have been only two attempts to simulate the propagation of the spill. In both cases, the spill was reconstructed using poor or incorrect topographical data, assuming a spilled hydrograph at the breaking point, and considering the fluid as water. In this research, new pre-failure topographical data were obtained combining field data with remote sensing techniques. These data were used to estimate the spilled hydrograph at the breaking point utilising a two-dimensional hydrodynamic numerical tool. Finally, due to the nature of the spilled fluid, two different attempts of reconstructing the spill propagation process of the Aznalcóllar mine disaster were performed. First, the fluid was considered as water with a suspended sediment load (26–660 g/L), i.e. assuming Newtonian fluid flow. Then the fluid was assumed to be mud-like (non-Newtonian fluid flow). These new simulations revealed that using a Newtonian fluid model, such as water with or without sediment, produced the best results in matching observed and simulated data. The non-Newtonian approach (muds) performed poorly. This suggests the spill behaved more like a concentrated sediment-laden flow than a mud-like one, possibly due to changes in fluid behaviour caused by the mine tailings in the pond after the failure.

Vermicompost Improves Growth of Tree Species in Different Stages of Ecological Succession Under Iron Mine Tailings

Vermicompost Improves Growth of Tree Species in Different Stages of Ecological Succession Under Iron Mine Tailings

Biogeochemical stability of organic covers and mine wastes under climate change simulated mesocosms.

Mine environments in boreal and sub-boreal zones are expected to experience extreme weather events, increases in temperature, and shifts in precipitation patterns. Climate change impacts on geochemical stability of tailings contaminants and reclamation structures have been identified as important climate-related challenges to Canadian mining sector. Adapting current reclamation strategies for climate change will improve long-term efficiency and viability of mine tailings remediation/restoration strategies under a changing climate. Accordingly, mesocosm experiments were conducted to investigate associations of climate-driven shifts in microbial communities and functions with changes in the geochemistry of organic covers and underlying tailings. Our results show that warming appears to significantly reduce C:N of organic cover and promote infiltration of nitrogen into deeper, unoxidized strata of underlying tailings. We also observed an increase in the abundance of some nitrate reducers and sulfide oxidizers in microbial communities in underlying tailings. These results raise the concern that warming might trigger oxidation of sulfide minerals (linked to nitrate reduction) in deeper unoxidized strata where the oxygen has been eliminated. Therefore, it would be necessary to have monitoring programs to track functionality of covers in response to climate change conditions. These findings have implications for development of climate resilient mine tailings remediation/restoration strategies.

Characterization and Reprocessing of Artisanal and Small-Scale Gold Mine Tailings

Characterization and Reprocessing of Artisanal and Small-Scale Gold Mine Tailings

Assessment of Cement Mortar Strength Mixed with Waste Copper Mine Tailings (CT) by Applying Gradient Boosting Regressor and Grid Search Optimization Machine Learning Approach

Growing environmental concerns and resource scarcity, the construction industry must investigate sustainable materials that reduce waste while improving building material properties. This study investigates the viability of using waste copper mine tailings (CT) as a partial replacement for river sand in cement mortar, assessing the impact on mechanical strength and developing a predictive model using a Gradient Boosting Regressor (GBR) and Grid Search Optimization (GSO). Copper tailings mix designs ranging from 0% to 50% replacement by volume (river sand) were developed, with a constant cement quantity while varying the proportions of sand and tailings. The experiments were carried out at Poornima University in Jaipur, using standard protocols to prepare specimens and measure their compressive strength for 0% CT to 50% CT as volume percent in the mixture. The results showed that the addition of copper tailings up to 20% (3CT2) had highly increased the mortar strength, while mix design 6CT3 showed the best strength at 30% CT. Beyond this threshold, strength declined, thus indicating an optimal replacement level. In the final step of the research, the GBR-GSO-based machine learning approach was employed for developing the predictive model for compressive strength in mortar with different contents of copper tailing for mix types 3CT and 6CT. The predictions obtained by the developed model were in very good agreement with empirical data, thus supporting the potential of machine learning to predict material performance for guiding the use of unconventional additives in construction. It could be said that this work not only represents the material properties of copper-tailing-infused mortar but also showcases state-of-the-art machine learning techniques in the building materials science domain while opening new paths for more innovative and sustainable building practices.

Novel Use of Concentrated Solar Thermal Energy for Producing Highly Thermal Activated Materials for CCUS via Mineral Carbonation of Mine Waste

An assessment of the levelised cost and associated CO2-eq emissions for the thermal activation of serpentine mine tailings to be used as activated feedstock for CCUS processes via mineral carbonation, is reported here for the first time. Two main technological scenarios were assessed, based on either direct fuel sources heating (natural gas and hydrogen) or indirect, CST-based heating with a back-up burner and storage to provide continuous operations, for a 200 ton/hr of processed ore and a targeted roasting ore temperature of 700°C. For CST-based systems, 3 different solar input scales, namely 50, 150 and 450 MWth, were considered, and simulations performed over a year timeline with a 10 minutes time step, using Mt Keith Nickel mine in Western Australia as the reference location. The analysis highlighted that the proposed CST-hybrid plant layout can achieve similar cost to that of fuel-only cases with current Australian fuel prices for natural gas and hydrogen, with lower CO2-eq emissions, and a parity cost with fuel-only scenarios of some 16 USD/GJ. The proposed CST-hybrid plant layout was also identified as the potential, preferred route over direct CST routes to achieve 24/7 continuous heat supply while retaining fine tuning of activation temperature, given a very narrow temperature window of activation for the chosen mine tailings for mineral carbonation processes.

Stabilization of Pb/Zn mine tailings by modified fly ash: characterization, performance, and mechanism.

The presence of heavy metals in mine tailings poses a serious threat to the surrounding environment. In this study, we aimed to stabilize Pb/Zn-containing mine tailings using modified fly ash (FA) with various alkali solutions. Notably, the modification of FA with Na2SiO3 (NaSi-FA) resulted in the most significant structure changes. To understand the adsorption mechanism of Pb and Zn by modified FA, batch adsorption experiments were conducted. Doubling the adsorption capacity for both Pb and Zn was observed in the modified FA samples compared to unmodified samples. These results could be attributed to the enhanced surface area and porous structure, providing more anchor sites for the heavy metal ions. Additionally, the adsorption of Pb and Zn was found to follow the Langmuir isotherm and pseudo-second order kinetic. Molecular dynamics simulations further supported the notion that Pb and Zn ions could effectively exchange with Na ions within the N-A-S-H gel network, ultimately solidifying them in its structure. Stabilizing Pb/Zn tailings with NaSi-FA resulted in a significant decrease in the leaching of Pb and Zn. Specifically, the leading amount decreased by 55.2% for Pb and 35.3% for Zn, showcasing the superior performance of this stabilization method. This reduction in leaching indicates effective compliance with environmental regulations regarding the containment of Pb and Zn.

Traceability and dispersion of highly toxic soluble phases from historical mine tailings: insights from Pb isotope systematics

Dispersion of potentially toxic elements associated with efflorescent crusts and mine tailings materials from historical mine sites threaten the environment and human health. Limited research has been done on traceability from historical mining sites in arid and semi-arid regions. Pb isotope systematics was applied to decipher the importance of identifying the mixing of lead sources involved in forming efflorescent salts and the repercussions on traceability. This research assessed mine waste (sulfide-rich and oxide-rich tailings material and efflorescent salts) and street dust from surrounding settlements at a historical mining site in northwestern Mexico, focusing on Pb isotope composition. The isotope data of tailings materials defined a trending line (R2 = 0.9); the sulfide-rich tailings materials and respective efflorescent salts yielded less radiogenic Pb composition, whereas the oxide-rich tailings and respective efflorescent salts yielded relatively more radiogenic compositions, similar to the geogenic component. The isotope composition of street dust suggests the dispersion of tailings materials into the surroundings. This investigation found that the variability of Pb isotope composition in tailings materials because of the geochemical heterogeneity, ranging from less radiogenic to more radiogenic, can add complexity during environmental assessments because the composition of oxidized materials and efflorescent salts can mask the geogenic component, potentially underestimating the influence on the environmental media.

Heavy Metal Contamination in Rhizosphere of Plants at a Decommissioned Gold Mine Tailings Dam

Heavy Metal Contamination in Rhizosphere of Plants at a Decommissioned Gold Mine Tailings Dam

The potential of phosphate mine tailings in the remediation of acidic Pb-contaminated soil

We investigated the potential of tailings from phosphate mining, consisting of phlogopite, carbonate minerals calcite and dolomite, and residues of apatite, to serve as a stabilizing agent in the remediation of Pb-contaminated soil in situ or on-site. In a 2.5-year field trial, test plots located in a former shooting range area were surface-treated with the tailings and analyzed for tailings-induced changes in Pb solubility and thus potential mobility within the soil profile. The factors and mechanisms controlling tailings-induced changes in Pb solubility in various soil types, and the susceptibility of Pb to leaching down the soil profile following the treatment, were investigated in supplementary laboratory-scale experiments carried out with horizon-specific soil samples collected from the field site. In the tailings-treated soil, the dissolution of the carbonate fraction of the tailings and the subsequent increase in soil pH contributed to the displacement of shot-derived Pb2+ ions by the carbonate-derived calcium ions (Ca2+) and the adsorption of Pb2+ by soil organic matter and Al, Fe, and Mn (hydr)oxide surfaces. Moreover, the apatite fraction of the tailings formed poorly-soluble compounds with Pb, particularly in soils high in exchangeable Pb2+ with respect to their cation exchange capacity. Consequently, the Pb solubility in tailings-treated soils substantially decreased. The reduction in Pb solubility was most evident in the organic topsoil high in Pb. Despite the liming effect of the tailings, and the susceptibility of Pb to form organic complexes conducive to solubilization upon an increase in pH, we found no evidence of tailings-induced leaching of Pb down the soil profile.

Metal bioaccumulation and translocation potential of three herbal plant species at mine tailings

Phytoremediation as a technique for cleaning soil contaminated with potentially toxic metals uses plants that can absorb them, and then translocate and accumulate them in above-ground parts. Its effectiveness depends on the selection of adequate plants. Therefore, this study aimed to investigate the potential of three wild herbaceous plant species (Holcus lanatus L., Agrostis alba L., and Eupatorium cannabinum L.) growing on mine tailings for phytoremediation applications. The content of selected metals in soil and plant samples was determined by flame atomic absorption spectrophotometer. The research results indicate that the content of Pb and Cu in the soil of the rhizosphere of the studied species was higher than their remediation values, after the exploitation of polymetallic ore (lead-zinc-copper), which made the tailings an ecological hazard. The species H. lanatus proved to be a good candidate for the phytoaccumulation of Cr, and the species A. alba of Ca, while the species E. cannabinum proved to be phytoaccumulator of all tested metals in the researched mine tailings. Potential for phytoextraction applications were shown by the species H. lanatus for Cd, Cu, Mg and Ni, and A. alba for Cd and Zn.

A novel alkali-slag cemented tailings backfill: Recycling of soda residue and calcium carbide slag

In order to address the safety and environmental concerns associated with high disposal cost and low disposal rate associated with mine tailings, low-cost cemented paste backfills (CPBs) were prepared from solid wastes such as calcium carbide slag (CS), soda residue (SR), ground granulated blast-furnace slag (GGBS) and iron tailings (TA) in this study. The effects of mass concentration of filling slurry, GGBS content, activator dosage, and SR proportion on the mechanical properties of CPBs were studied. The results showed that a flow of 235.8 mm and 28-d compressive strength of 2.3 MPa for the freshly mixed slurry could be attained with 75 % mass concentration, 14 % GGBS content, an activator-to-binder ratio of 0.4, and a CS-to-SR ratio of 3:7. The strength of CPBs first increased and then decreased with the increasing of activator dosage or SR proportion contents, and reached the optimal value for the activator-to-binder ratio of 0.4 and SR of 70 % – 75 %. Microstructural analyses by TG-DTG, FTIR, SEM-EDS, and XRD revealed that mainly C-(A)-S-H gel, hydrotalcite (HT), and Friedel's salt (FS) were formed as the hydration products in CS-SR synergistically-activated GGBS paste. The Ca2+ dissolved from CS facilitated GGBS hydration to generate the C-(A)-S-H gels and further reacted with Cl− in SR and [Al(OH)6]3− dissolved from GGBS to generate FS. The combined effect of C-(A)-S-H gel and FS enhances the strength of CPBs. When the percentage of SR is in the range of 70–75 %, the synergistic excitation of slag by alkali slag and calcium carbide slag is superior, and the matrix structure is denser.

Microbial-mediated metal(loid) immobilization in mulch-covered tailings

Mulch coverage of mining tailings can create anaerobic conditions and consequently establish an anoxic environment that promotes the metabolic processes of anaerobic microorganisms. This anoxic environment has the potential to decrease heavy metal mobility and bioavailability. While tailings exposed to sunlight have been extensively studied, research on the effects of microbial-mediated geochemical cycling of heavy metals in mulch-covered tailings is scarce. This study aimed to examine the effects of mulch coverage-induced alterations in the structures of tailing microbial communities on the biogeochemical processes associated with heavy metals. Mulch coverage significantly reduced the pH of the tailings and the tailings exhibited heavy metal bioavailability. Random forest analysis demonstrated that mulch coverage-induced changes in the As/Cd-contaminated fractions and nutrients (total organic carbon and total nitrogen) were the most crucial predictors of microbial diversity and ecological clusters in the tailings. Notably, different from direct metal(loid) immobilization, mulch coverage can facilitate heavy metal immobilization in tailings by promoting microbial-mediated Fe, S, and As reduction. Overall, this study demonstrated that mulch coverage of tailings contributed to a reduction in heavy metal mobilization, which can be attributed to shifts in microbial-mediated Fe, S, and As reduction processes.The study provides valuable insights into the potential of mulch coverage as a remediation strategy and underscores the importance of microbial-mediated processes in managing heavy metal pollution in tailing systems.

Microstructure evolution and mechanical behavior of foamed cement-based tail backfills under varying fiber types and concentrations.

Industrial solid waste (mine tailings) management has emerged as the key universal ecological challenge as a result of the unceasing creation of rising waste by-products. Employing tailings makes mine fill production economical and assists resolve disposal problems. Foamed cement-based tailings backfill (FCTB) is a mine fill consisting of tailing, cement, water, and foaming agents. It provides certain advantages such as lightweight, good fluidity, and thermal insulation yet is relatively weak in strength. Additionally, FCTB's strength properties can be intensely improved by adding fibers. A total of three diverse fibers: polypropylene (PP), glass (G), and basalt (B) as well as dodecyltrimethylammonium bromide (DTAB) as a foaming agent were used to prepare fiber-reinforced foamed cementitious tailings backfill (FR-FCTB). The mechanical properties, energy evolution, ductility, and microstructure of FR-FCTB were elaborately investigated by uniaxial compression tests (UCS) and SEM. Laboratory findings demonstrate the reinforcing effect of three fibers on FCTB specimens: glass > polypropylene > basalt. FR-FCTB showed the best strength features as a fiber content of 0.3% was adopted in FCTB. At this time, the UCS performance of glass fiber-reinforced FCTBs was 0.85MPa increased by 18.1%. The addition of fibers can increase the fill's energy storage limit, slow down the discharge of elastic strain energy within the backfill, and enhance the fill's ductility and toughness. The ductility factor evaluates the degree of deterioration of filling in terms of post-peak drop, with all FR-FCTB values being greater than CTB. FR-FCTB's chief hydration product is the C-S-H gel. Fiber's bridging effect significantly rallies crack extension and thus fill's strength features. Lastly, the study's main results are instructive for the industrial application of FR-FCTB used in metallic mines.

Unveiling the Influence of Antimony Substitution on the Surface Properties and Adsorption Behavior of Ferrihydrite: From Molecular Mechanisms to Environmental Implications.

Antimony(V) substitution is common in secondary ferrihydrite, especially in mining areas and tailings. However, its impact on the adsorption behavior of ferrihydrite is still unclear. Therefore, this study investigated the influential mechanisms of Sb(V) substitution on the lattice structure and surface properties of Sb-substituted ferrihydrite (SbFh), and its adsorption of coexisting Sb(OH)6-. Antimony(V) is substituted at Fe1 sites and is primarily distributed on the surface. Substitution has opposing effects on the outer- and inner-sphere complexation of Sb(OH)6-. On one hand, substituted-Sb(V) transfers more positive charges to ≡FeOH, reducing the number of H bonds. Subsequently, the charge saturation of ≡FeOH decreases, surface charge increases, and outer-sphere complexation is promoted. On the other hand, the elevated bond valence of Sb-O increases charge saturation of ≡FeOH, reducing the charge capacity that ≡FeOH can accommodate from inner-sphere complexes. Thus, inner-sphere complexation is inhibited. Inner-sphere complexation plays a more important role, and Sb(OH)6- adsorption is inhibited. Additionally, the primary complexation modes of Sb(OH)6- transform from bidentate to monodentate complexation. This research has important implications for understanding the environmental behavior of ferrihydrite, as well as the fate and bioavailability of antimony in mining areas and tailings.

Decrease due to pollution in the rhizosphere microbial diversity can be amended by supplementation from adapted plants of another species

Manipulating the rhizosphere microbiome to enhance plant stress tolerance is an environmentally friendly technology and a renewable resource to restore degraded environments. Here we suggest a sustainable bioremediation strategy on the example of Stebnyk mine tailings storage. We consider Salicornia europaea rhizosphere community, and the ability of the phytoremediation plant Salix viminalis to recruit its beneficial microbiome to mediate the pollution stress at the Stebnyk mine tailings storage. The tailings contain large amounts of brine salts and heavy metals that contaminate the ground water and surrounding areas, changing soil biogeochemistry and causing increased erosion. The species richness of the endophytic bacterial community of S. viminalis roots was assessed based on observed OTUs, Shannon-InvSimpson, and evenness index. Our results obtained using the plant-based enrichment strategy show that biodiversity was decreased across the contamination zones and that S. europaea supplementation significantly increased the species richness. Our results also indicate that the number of dominating bacteria was not changed across zones in both S. europaea-treated and untreated bacterial populations, and that the decrease in richness was mainly caused by the low abundant bacterial OTUs. The importance of selecting the bioremediation strains that are likely to harbor a reservoir of genetic traits that aid in bioremediation function from the target environment is discussed