Gold Tailings Research Articles

Effects of gold tailings dosage and polyvinyl alcohol fibre content on the frost resistance of ECC

The effects of gold tailings and polyvinyl alcohol (PVA) fibre on the frost resistance of engineered cementitious composites (ECC) were investigated. The ECC were made with three gold tailings dosages and four PVA fibre contents. A water/binder (w/b) ratio of 0.28 was used for all mixtures. Surface damage, mass loss, relative dynamic elastic modulus, compressive strength and damaged layer thickness (DLT) were investigated to assess the frost resistance of the ECC. The results showed that the effect of gold tailings on the frost resistance of the ECC was marginal, but the frost resistance increased with an increase in PVA fibre content. The ECC with the addition of gold tailings had the same excellent frost resistance as those without gold tailings, indicating that it is feasible to replace silica sand with gold tailings at up to 100% replacement. A model to predict the DLT in ECC as a function of gold tailings dosage and freeze–thaw cycles was developed.

Ca-bentonite/polymer blends to compose GCLs for effective containment of mining leachates

This study investigates the swelling potential of blends of a Brazilian sodium-activated calcium bentonite with linear structure polymers and a cross-linked structure polymer in contact with aggressive mining solutions (sodium hydroxide, calcium chloride, simulated bauxite liquor, copper tailing and gold tailing leachates). Results showed that the polymer addition contributed to the swelling of the bentonite under aggressive solutions. The effectiveness of the polymers varied with the permeant liquid and concentration. Sodium Polyacrylate and Carboxymethyl Cellulose proved the most effectiveness in bentonite swelling capacity. Research presents valuable insights into the chemical compatibility of bentonitepolymer blends when exposed to aggressive liquids.

Linking laboratory quasi-steady state strengths to field scale performance of tailings

Current state of practice for the assessment of liquefied strengths of tailings relies primarily on empirical or semi-empirical correlations based on penetration testing. That is, despite liquefied strength being arguably the most important strength parameter for the design of brittle tailings storage facilities, there is much less success or acceptance of the use of laboratory element tests to support strength selection compared to other forms of strengths inferred in geotechnical engineering. This is particularly the case for tailings at a state near or slightly dense of the critical state line (CSL) for which there is ample evidence of field-scale flow liquefaction but where laboratory element tests often behave in a manner inconsistent with such field-scale response – at least at large strains. The current paper examines the quasi steady state (QSS) strength of sands and tailings for which the CSL has been measured, linking the observed strengths to inferred in situ behaviour through the state parameter. Particular focus is placed on QSS strengths obtained from simple shear tests carried out within a hollow cylinder torsional shear system where the stress state in the test is a better representation of in situ below-slope conditions that the triaxial compression test. In particular, the marked effect of intermediate principal stress on the QSS in sands is highlighted. Alternatively, the negligible anisotropy seen in a sandy silt gold tailings, and the potential implications in the context of QSS strengths and field-scale behaviour, are examined and emphasised.

Characterization of Gold in Complex Historical Refractory Tailings for Enhanced Process Optimization

ABSTRACT Historical gold tailings show promise as a secondary resource amid declining primary deposits, yet conventional cyanidation falls short, resulting in recoveries below 90%. An essential pre-treatment process is crucial for optimal recovery, contingent on understanding the complex mineralogy of the tailings. This study employs a multidisciplinary approach to thoroughly analyze gold’s refractory behavior in complex historical tailings. Using operational mineral fractions, cyanide bottle roll tests, aqua regia digestion, diagnostic leaching, and chemical and mineralogical analyses, the research draws material from Witwatersrand’s extensive tailings reservoirs. These reservoirs, exemplifying complexity, exhibit a recovery rate of less than 50% through cyanidation. Findings reveal limited cyanide-amenable gold, with recoveries ranging from 14–61% at ∼0.05 g/t, primarily as micron to nano-sized native gold particles hosted in the slimes mineral fraction (<40 µm). Higher susceptibility to cyanide leaching is observed in recoveries ranging from 14–74% compared to 10–54% in light mineral fractions (<2.95 g/cm3). Non-cyanide amenable forms, such as sulfides and silicates, contribute to refractory behavior at 4–38% (∼0.09 g/t) and 11–32% (∼0.05 g/ton) respectively, with varying gold distributions across different tailings dumps. This suggests that a pre-treatment step, combined with tailored leaching in the metallurgical flowsheet, would substantially improve gold recoveries beyond 60%. The investigations in this study provide a valuable analytical tool for determining the amenability of complex historical gold tailings to different pretreatments, optimizing gold recovery, contributing to sustainable resource management, and maximizing the utilization of this valuable gold resource.

Exploring the accumulation capacity of dominant plants based on soil heavy metals forms and assessing heavy metals contamination characteristics near gold tailings ponds

Heavy metal contamination of soil commonly accompanies problems around gold mine tailings ponds. Fully investigating the distribution characteristics of heavy metals and the survival strategies of dominant plants in contaminated soils is crucial for effective pollution management and remediation. This study aims to investigate the contamination characteristics, sources of heavy metals (As, Cd, Pb, Hg, Cu, Zn, Cr, and Ni) in soils around gold mine tailings ponds areas (JHH and WZ) and to clarify the form distribution of heavy metals (As, Cd, Pb, Hg) in contaminated plots as well as their accumulation and translocation in native dominant plants. The results of the study showed that the concentrations of As, Pb, Cd, Cu, and Zn in soil exceeded the national limits at parts of the sampling sites in both study areas. The Nemerow pollution index showed that both study areas reached extreme high pollution levels. Spatial analysis showed that the main areas of contamination were concentrated around metallurgical plants and tailings ponds, with Cd exhibiting the most extensive area of contamination. In the JHH, As (74%), Cd (66%), Pb (77%), Zn (47%) were mainly from tailings releases, and Cu (52%) and Hg (51%) were mainly from gold ore smelting. In the WZ, As (42%), Cd (41%), Pb (73%), Cu (47%), and Zn (41%) were mainly from tailings releases. As, Cd, Pb, and Hg were mostly present in the residue state, and the proportion of water-soluble, ion-exchangeable, and carbonate-bound forms of Cd (19.93%) was significantly higher than that of other heavy metals. Artemisia L. and Amaranthus L. are the primary dominating plants, which exhibited superior accumulation of Cd compared to As, Pb, and Hg, and Artemisia L. demonstrated a robust translocation capacity for As, Pb, and Hg. Compared to the concentrations of other forms of soil heavy metals, the heavy metal content in Artemisia L correlates significantly better with the total soil heavy metal concentration. These results offer additional systematic data support and a deeper theoretical foundation to bolster pollution-control and ecological remediation efforts in mining areas.

Gold tailings-solar salt shape-stabilized phase change materials for medium-high temperature thermal energy storage

Gold tailings (GT) are a form of industrial solid waste generated by gold production that occupy large areas of land and cause a significant environmental burden. This study accordingly prepared a novel composite phase change material (CPCM) for medium-high temperature thermal energy storage using a hybrid sintering method to combine GT as the base material with solar salt (SS) as the phase change material. The resulting gold tailings composite phase change materials (GT-CPCM) was able to retain up to 45 wt% of SS without leakage. The results of an X-ray diffraction analysis suggested excellent chemical compatibility between the GT and SS, and scanning electron microscopy demonstrated an even distribution of SS within the GT structure. A mechanical characterization of GT-CPCM specimens revealed a maximum compressive strength of 36.66 MPa. Furthermore, the maximum latent heat of the GT-CPCM was 45.01 J/g, its thermal conductivity was 0.435 W/(m·K), and its energy storage density was 563.01 J/g within 25–400 °C. Critically, the GT-CPCM specimens had good cycling reliability after 100 thermal cycles. Thus, the mechanical and thermal properties of this novel CPCM make it ideal for waste heat recovery with the benefit of utilizing GT as a resource.

Uniqueness of the Normal Consolidation Line for Gold Tailings

Abstract Depending on the stress state, mine tailings are generally accepted to be susceptible to static liquefaction. A common method to assess the in situ stress state of tailings in relation to static liquefaction susceptibility involves the use of the state parameter. Because most tailings materials are normally consolidated (NC), this type of assessment requires knowledge about the normal consolidation line (NCL). It has been shown experimentally that the uniqueness of the NCL is vastly different for fine-grained and coarse-grained soils, with clays usually exhibiting a unique NCL and clean sands exhibiting an infinite number of parallel NCLs. Gold tailings, a sandy silt, fall between clays and clean sands, and there are limited experimental data regarding their compression behavior over a range of initial void ratios. This lack of data results in inconsistent interpretation of the uniqueness of the NCL for gold tailings in the industry. This can influence the results of designs and safety evaluations of tailings dams. In this study, a number of oedometer tests were conducted on gold tailings sourced from an active tailings dam in South Africa. Several specimens were prepared at various initial densities and were consolidated in small increments to a high effective stress. The oedometer tests were supplemented with triaxial compression tests, from which a unique critical state line was identified. Across the oedometer and triaxial tests, it was found that the behavior of the NC and overconsolidated samples was consistent with that typically observed for fine-grained soils. Therefore, for practical purposes, it appears that the gold tailings tested can be viewed in a framework with a unique NCL. No significant influence of particle crushing was noted.

Chemical sterilisation and vetiver grass performance on gold tailings dump chrono-toposequences at Muriel mine, Zimbabwe

Chemical sterilisation and vetiver grass performance on gold tailings dump chrono-toposequences at Muriel mine, Zimbabwe

First insight into the natural biodegradation of cyanide in a gold tailings environment enriched in cyanide compounds

The disposal of mining wastes that contain cyanide are dumped in tailings from gold extraction is a public concern in mining countries such as South Africa. Many studies have shown the potential of microorganisms to degrade cyanide. However, no in-situ exploration, in tailings contaminated with cyanide, of the capability of indigenous microorganisms to act as a natural barrier for cyanide attenuation has been performed. Here we aim to combine geochemical and metagenomics techniques to reveal the genomic machinery of indigenous bacteria to degrade cyanide in gold tailings. Indigenous bacteria (i.e., Alicyclobacillus, Sulfobacillus, Acinetobacter, Achromobacter, and among others) pose the genomic machinery to trigger hydrolytic cyanide degradation using enzymes such as nitrilase, nitrile hydratase (Nhase) and thiocyanate. It seems that the lack of nitrogen sources induces the use of cyanide, which would contribute to its natural attenuation in the gold tailings. Therefore, the bacteria identified could represent the first barrier for the detoxification and degradation of cyanide in the outermost layer of the tailings.

Recovery of Tellurium from Cyanide Leaching Gold Tailings and the Leaching Mechanism of Lead Telluride

Recovery of Tellurium from Cyanide Leaching Gold Tailings and the Leaching Mechanism of Lead Telluride

Determination of Natural Radioactivity Levels and Resultants Radiological Hazard from Soil Samples around Gold Mining Area in Ijesa-land South-Western Nigeria

Activity concentration levels and some radiological parameters owing to natural radioactivity in the soil samples randomly obtained in gold tailing sites in Ijesa­-land Southwestern Nigeria were analyzed. Analyzed results from 30 soil samples using multi-channeled NaI gamma detector show that the activity concentration of 233U; ranged from 17.42 0.54 to 49.892.42 BqKg-1; 232Th ranged from 22.10 4.70 to 76.557.44BqKg-1 and 40K; ranged from 307.0023.90 to 693.5851.50 BqKg-1 in the samples were measured. The mean absorbed dose rate calculated was marginally higher than the world average of 59nGyh-1. The average annual effective dose rate (outdoor) for all samples ranged from 0.08 + 01. 11mSv.y-1 with a mean of 0.07 which stays far below the permitted worldwide limit of 1mSv.y-1hy by International Commission on Radiation Protection (ICRP 2010). The calculated hazard indices for external and internal remained to be lower than unity signifying that mineworkers and individuals active in such area are not exposed radiation hazard.

Preparation of low-cost green engineered cementitious composites (ECC) using gold tailings and unoiled PVA fiber

The current study aims to establish low-cost green engineered cementitious composites (ECC) using gold tailings, unoiled PVA fiber and large-volume fly ash. Through compression test, four-point bending test, direct tensile test, matrix fracture toughness test and single-crack tensile test, the mechanical properties of ECC were explored. It is found that incorporation of gold tailings leads to the enhanced compressive strength and reduced ductility. When quartz sand was fully replaced by gold tailings, the compressive strength increased by 19.5%, the strain capacity decreased by 22.3%, the deflection decreased by 15.8% but no obvious change occurred in first crack stress as well as tensile strength. A rougher surface of unoiled PVA leads to reduced slip hardening response. At micro-scale, replacement of the quartz sand using gold tailings leads to higher complementary energy (Jb’) available for strain hardening during the crack development and reduced matrix fracture energy (Jtip) for crack initiation. This contributes to the increased pseudo strain-hardening PSHE (=Jb’/Jtip) index and ductility. When fiber content is 2.0%, the values of PSHS (=σ0/σfc) index reached 1.2, which ensures the saturated multi-joint cracking behavior.

Experimental and theoretical studies of the mechanism of oxidation of arsenopyrite in the presence of hydrogen peroxide

Arsenopyrite, which is a typical gold-bearing mineral, is widely distributed in gold tailings. In this study, we have examined the surface morphology of arsenopyrite before and after oxidation, the types of oxidation products, and the oxidation mechanism. We have carried out froth flotation and contact angle measurements and found that the wettability, which is a descriptor of the hydrophilicity of the arsenopyrite surfaces, increases with the levels of surface oxidation. X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition before and after oxidation, which has demonstrated that both Fe(II) and As(III) oxidize to Fe(III) and As(V), respectively. The microscopic changes of the surface at the atomic level were also examined by atomic force microscopy (AFM), which indicated that the oxidation products gradually and partially cover the surface of the arsenopyrite upon reaction with hydrogen peroxide. These observations explain why the arsenopyrite XPS signal and the uniform change in wettability do not vanish completely during oxidation. Finally, density functional theory (DFT) calculations were used to describe the oxidation of the surface As atoms by the O of the chemisorbed hydrogen peroxide molecules. The computational results also show that the hydrogen peroxide dissociates into two hydroxyl groups that coordinate the Fe and As atoms on the surface of the arsenopyrite. The results of this study have important implications for the reuse of gold tailings containing arsenopyrite.

In-situ grown SiC whiskers enhance flame retardancy of alkali-activated gold tailings geopolymer composite coatings by incorporating expanded graphite

Herein, a gold tailings-based flame-retardant coating blended with zinc phytate (ZnPA)/β-cyclodextrin (β-CD)/expanded graphite (EG) is prepared by the sol-gel method. The coating is used in flame-retardant plywood. It explores the efficient recycling of industrial solid waste. Firstly, the microstructure analysis reveals that EG forms in-situ SiC ceramic whiskers in the solid solution of orthosilicate and pyrophosphate. Meanwhile, the synergistic flame-retardant effect is explained through morphological characterization and pyrolysis kinetics analysis. Adding 2 wt% EG significantly improves the flame retardancy of the coating, as evidenced by a decrease in the peak of heat release rate (p-HRR) and an increase in the fire performance index (FPI). The p-HRR decreases from 104.67 kW·m−2 to 75.08 kW·m−2, while the FPI increases from 2.11 s·m2·kW−1 to 3.51 s·m2·kW−1. Moreover, the pyrolysis kinetics is modeled using the Zhuralev-Lesokin-Tempelman (Z.-L.-T.) three-dimensional diffusion-reaction model, revealing an increase in Eα from 74.90 to 85.82 kJ·mol−1 in the temperature range of 674–890 °C. The coating exhibits 60% formaldehyde adsorption performance. Therefore, this study proposes a new in-situ whisker synergistic flame-retardant system and sheds light on the potential applications of new geopolymers in the sustainable development of the green flame-retardant field.

Effect of saturation confining pressure on accessible density and shear behaviour of sandy silt tailings

Significant reduction in the brittleness of sandy silt/silty sand tailings at high stresses has frequently been observed in laboratory element testing due to curvature of the critical state line and the limiting compression curve. This has led to discussions regarding the range of effective stresses across which such materials can exhibit brittle undrained shearing such that flow liquefaction could occur. However, much testing of such tailings appears to involve saturation of the tailings under relatively low-confining stresses. This differs from the potential in situ loading within a filtered tailings stack, where material placed in a loose, unsaturated state may be subjected to significant overburden pressures prior to potential subsequent saturation. A series of isotropically consolidated triaxial tests were carried out on sandy silt gold tailings to investigate the effects of the saturation process of loose moist-tamped specimens occurring at different confining stresses. The tests indicated much looser states were achievable when saturation occurred at higher confining pressures, with resulting undrained shearing for such specimens being of similar magnitudes of brittleness as observed in flow liquefaction case histories. Consideration of saturation overburden pressure of filtered tailings stacks therefore appears warranted.

Customized copper/cobalt-rich ferrite spinel-based construction ceramic membrane incorporating gold tailings for enhanced treatment of industrial oily emulsion wastewater

New ceramic membranes (CM) using environment-oriented materials instead of rare materials are more attractive and easier to large-scale engineering and promotion. In this study, the feasibility of customizing low-cost and robust CM, is investigated by sintering typical available solid wastes (Fe-S-rich gold tailings and Si-rich marine shellfish powder) as the matrix with copper/cobalt-rich precursors. Analysis results indicate that the precursors (Cobaltate and Cuprate) with the proposed ratio (1:1 by mass, 1300 °C) can be chemically stable crystallized in the more durable structure of customized copper/cobalt-rich ferrite spinel-based construction CM (CM-(Cu-Co)Fe2O4). The composite membrane can operate stably and consumes no additional energy. After detailed characterization of the pore structure, the purification treatment of industrial oily wastewater (rejection rate > 99.9), emulsion oily wastewater (rejection rate > 97.9) and alizarin red wastewater (rejection rate > 99.3) was fully evaluated. Surprisingly, the waste-to-resource CM of CM-(Cu-Co)Fe2O4 exhibits significant heavy metal iron ion removal performance (>94%) due to electrostatic attraction and adsorption. The successful preparation and application of environment-oriented multifunctional CM from a typical solid waste matrix provide a promising strategy of resource recovery for beneficial utilization of ordinary solid wastes with stock as ceramic raw materials.

Removal and Reclamation of Trace Metals from Copper and Gold Mine Tailing Leachates Using an Alkali Suspension Method

Leachates from mine tailing ponds, which usually contain a variety of metallic ions, are highly toxic to human and ecological health. The common methods used to remove those trace metallic are difficult due to the extremely acidic conditions and the diverse kinds of metals in mine tailing leachates. Herein, we proposed an economical and efficient soil-assisted alkali suspension approach to remove and reclaim the trace metals. Under the optimum conditions, more than 98% of Cu2+, Zn2+, and Cr3+, and 93% of Cd2+ were removed from authentic copper and gold tailing leachates. Multiple characterizations indicated that the quick removal of trace metal ions from leachates was mainly due to the formation of amorphous hydroxides which are easily adsorbed by soil particles. Additionally, small quantities of metal ions and organic matter complexes were formed, which contributed to the removal of trace metals. Furthermore, most of the adsorbed trace metal in authentic tailing leachate can be reclaimed by a simple acid treatment. Life cycle assessment analysis demonstrated the environmental sustainability of this alkali suspension method due to its smaller contribution to global warming. This study provides an efficient and low-cost approach for the disposal and recycling of toxic mine tailing leachates.

Constitutive modelling of unsaturated gold tailings subjected to drying and wetting cycles

AbstractThe strength and deformation properties of tailing materials are strongly affected by their hydromechanical history including the cycles of desiccation and re‐saturation they undergo due to the often layered deposition process. The current study reviews the fundamental characteristics of some of the commonly used constitutive models for partially saturated soils, namely Barcelona Basic Model (BBM), Glasgow Coupled Model (GCM), and a dilatancy‐based model by Buscarnera and Nova Model (BNM) in predicting the hydromechanical response of tailing materials. In particular, we investigate the strength and shortcomings of each model and compare their capability of capturing the salient trends during drying/wetting cycles, as well as during shearing. Based on comparison with experimental data, modifications are suggested for the models, specifically related to a realistic formulation of the water retention curve and its hysteresis. The results point to a potential trade‐off in the accuracy of the constitutive models in capturing the volumetric responses during the drying/wetting cycles on one hand, and the stiffness and strength characteristics during the shearing phase on the other.

Effect of Ca and Mg on the properties of foamed ceramics prepared with multisolid waste

AbstractWith vanadium tailings and lead‐zinc tailings as the main raw materials, gold tailings, waste glass powder, other fluxes and SiC foaming agents are added to prepare foamed ceramics. The effects of Ca and Mg in the fluxes of calcite, talc, and dolomite on the appearance, pore size, porosity, bulk density, and compressive strength of the samples were investigated and the mechanisms of the effects were analyzed. The XRD results showed that the sample consisted primarily of quartz, albite, augite, and a small amount of corundum. Calcite favors the formation of the augite phase, talc favors the formation of the albite phase, and dolomite combines the advantages of both. The formation of albite reduces the viscosity of the melt, and the formation of augite greatly enhances the strength of foamed ceramics. It has been shown that by adding 8% dolomite, a foaming ceramic with a bulk density of .561 g/cm3, a porosity of 62.77% and a compressive strength of 10.823 MPa can be prepared, resulting in a low‐cost, lightweight and high strength foamed ceramic partition.

Microstructure and mechanical behavior of cemented gold/tungsten mine tailings-crushed rock backfill: Effects of rock gradation and content

Without appropriate and responsible waste management in place, the cursory storage of tailings and waste rocks on the surface can cause devastating damage to the planet's ecosystems. To proactively manage or abolish the damage, some techniques such as mine backfill have been already used repeatedly in mines. Microstructure and strength behavior of cementitious tailings-crushed rock backfill (CTCRB) with gold/tungsten tailings and rock contents (e.g., 10%, 20%, 30%, 40%, and 50%) were conducted in this study by using both UCS (unconfined compressive strength) tests (e.g., peak strengths, stress-strain curves, failure modes) and SEM micro-graphs. Key conclusions were shown that: when gradation and content of crushed rock was considered as 1–3 mm and 50% respectively, the UCS value of gold tailings based backfills was 1.02 MPa. In contrast, the UCS value of tungsten mine tailings based backfills was 1.36 MPa when the amount of crushed rock within the filling matrix became 10%. Tungsten tailings based backfills were more sensitive to crushed rock gradation than gold tailings based backfills. CTCRB's stress-strain curvatures were up-concave in the step of pore compaction. With the increase in the content and gradation of crushed rock, tungsten tailings based backfills showed swelling and crushing in complete destruction. Tailings' particle size, crushed rock content and gradation utterly affected the failure modes of CTCRB. Ettringite/CSH gel was found to be the leading hydration materials in the backfill matrix. The micro-cracks within CTCRB specimens were unfavorably correlated with its UCS data. To conclude, this study's main outcomes could give a significant guide for CTCRB's industrial uses.