Gold Tailings Research Articles

Distribution of the microbial community and antibiotic resistance genes in farmland surrounding gold tailings: A metagenomics approach.

Metal mining has caused the accumulation of waste mine tailing dumps from abandoned mines. The pollution of farmlands surrounding metal tailings by heavy metals has been a long-recognized problem. However, the distribution of antibiotic resistance genes (ARGs) in tailings and the main factors influencing this distribution have rarely been reported. In this study, a metagenomics approach was used to investigate the microbial community and ARGs present in farmland surrounding gold tailings in northern China. The results showed that the main pollutants in the farmland were As, Pb, and Cd. Proteobacteria and Actinobacteria were the dominant phyla of microbes in farmlands surrounding gold tailings. A total of 75 ARGs with 327 ARG subtypes were detected in soil samples. Macrolide-, lincosaminide-, and streptogramin B resistant genes accounted for the majority of ARGs in this study, and Actinobacteria, Proteobacteria, and Acidobacteria were the hosts of most ARGs. Partial least squares path modeling revealed that the microbial community was the most influential driver moderating the distribution of soil ARGs near tailings, and heavy metals have direct and partially indirect effects on these ARGs. In contrast to previous analyses of ARGs, our study found that mobile gene elements had a minimal impact on ARGs. Overall, this study presents a complete ARG survey that sheds light on the distribution and fate of ARGs under heavy metal contamination in farmland around gold tailings.

Heavy Metals Tolerance Potential of Fungi Species Isolated from Gold Mine Tailings in Ghana

Introduction: Heavy metal contamination has necessitated a less expensive and non-destructive clean-up technique such as mycoremediation. This study aimed to isolate, identify, and evaluate the tolerance of fungi species in different concentrations of heavy metals for their potential use in bioremediation. Materials and Methods: Fungi were isolated by serial dilution and spread plate techniques from gold tailings and their tolerance to different concentrations of As, Cd, Cr, Cu, Pb, Zn (as potential bioremediation candidates) was evaluated. Fungal radial growths were recorded daily over a 14 days’ incubation period to establish their tolerance levels using the Tolerance Index. Results: Five isolated fungi species belonged to the genera Aspergillus, Trichophyton, Rhizopus, Trametes, and Trichoderma. Except for Trichophyton rubrum, the other fungi species were tolerant to all Cr concentrations (0 – 100ppm), but no significant difference was observed in mycelia growth compared to their controls. With high tolerance index ranging from 0.91 to 1.02, Trichoderma viride and Rhizopus oryzae were tolerant to all Cu concentrations (0 – 125ppm). High tolerance was exhibited by Trametes versicolor to Cd at 25 and 50 ppm, and by Rhizopus oryzae at 25 ppm, but no significant difference was found in mycelia growth. Rhizopus oryzae tolerated all As and Pb concentrations with high tolerance index ranging from 0.81 to 1.00. It also tolerated Zn at 200-600ppm concentration with a tolerance index from 0.80 to 0.91. Conclusion: The selective nature of these fungi species for specific heavy metal tolerance indicates their potential for selective use as effective bioremediative clean up agent of heavy metals contaminated sites.

The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill

The effectiveness of mine backfilling depends on the properties of its constituents. The high cost of cement, which is commonly used as a binder in mine backfill, has led researchers to seek alternatives to partially replace it with other binders. This study investigated the potential to use nano-calcium carbonate (NCC) and natural pozzolans (zeolite and pumice) along with Portland cement (PC) in mine backfill. Two types of experimental samples were prepared: (1) gold tailings and silica sand to investigate the effect of NCC and (2) nickel tailings to investigate the effect of natural pozzolans. The unconfined compressive strength (UCS) was measured for samples cured for up to 56 days. Moreover, selected samples were subject to mercury intrusion porosimetry to investigate microstructural properties. Results show that addition of NCC did not improve the UCS of backfill prepared with gold tailings and cured for 28 days, whereas a dosage of 1% NCC in backfill samples prepared with silica sand improved UCS by 20%, suggesting that the gold tailings negatively affected strength development. Natural pozzolans, in particular, 20% zeolite, had 24% higher UCS after 56 days of curing compared to samples prepared with PC and thus have the potential to partially replace cement in mine backfill.

Utilizing gold mine tailings to produce sintered bricks

• Test materials are gold tailings and clay. • Effects of clay content, forming moisture, firing temperature and holding time. • Compressive strength, water absorption, bulk density and loss on ignition. • Single factor test and optimization experiment. Limited recycling options and large stockpiles of gold tailings lead to a series of social and environmental issues. The recycling of gold tailings is helpful for alleviating these issues. This study investigated the possibility of utilizing gold mine tailings to produce sintered bricks. In the preparation process, clay was introduced as an additive. The effects of clay content, forming moisture, and sintering parameters (such as firing temperature and holding time), on the properties of the sintered bricks were analyzed by single factor tests, and the preparation process was optimized based on the results of these tests. These results indicated that the compressive strength, water absorption, bulk density, and loss on ignition exhibit different correlations with the clay content, forming moisture, and sintering parameters. According to the TG-DSC and XRD analysis, gas generation and mineral decomposition occurred during the sintering process. The sanidine, pyrite, montmorillonite, and calcite were decomposed to form hematite and anorthite. In conclusion, the optimum process parameters for the preparation of the sintered bricks are a clay content of 35%, forming moisture of 25%, firing temperature of 1030 °C, and holding time of 105 min.

Heavy metal pollution caused by cyanide gold leaching: a case study of gold tailings in central China.

It is known that the tailings of gold mines have brought serious heavy metal pollution; however, the heavy metal pollution caused by gold tailings in specific geological environments and extraction processes still must be studied. This study investigated the distribution, speciation, bioaccumulation, and pollution of heavy metals in soils from the Yueliangbao gold tailings area in central China, where gold was extracted by cyanidation. The results show that the concentrations of Cu, Pb, Zn, Mn, Mo, and Cd in the soils of the tailings pond were higher than those in the local background. The concentrations of heavy metals related to mineralization activities, such as Cu, Pb, Zn, and Mo, varied with the distance to the tailings pond center. There was a decreasing trend of tailings pond center > tailings pond entrance > surrounding environment. This study's gold tailings pond differed from those of other regions because of its high content of unextracted Cu remaining in the pond. The proportion of non-residual Cu in the tailing pond soil was much higher than that of residual Cu, indicating it was likely to migrate to the surrounding environment. The pollution assessment indicated that the tailings pond soils were heavily polluted by Cu, and the level of heavy metal pollution in soils was positively correlated with the distance to the tailings pond center. Consequently, this tailings pond may become a source of Cu pollution in the surrounding environment, thus endangering environmental safety and human health. The study of heavy metal concentrations in the dominant plants showed that Chinese brake (Pteris vittata L.), Ramose scouring rush (Equisetum ramosissimum), and Manyflower silvergrass (Miscanthus floridulus) had the potential to be used for the phytostabilization of Cu.

Tailings Filtration Using Viper Filtration Technology\u2014a Case Study

Investigation and uptake of filtered tailings continues to grow throughout the globe. This is driven by a wide range of site-specific considerations, which include such factors as tailings characteristics (e.g., amenability to filtration), production rates, climate, water availability, cost drivers, environmental requirements, and social factors. Despite the aforementioned technological growth, the currently available filtration technology is not able to meet the needs of many operations and projects that would otherwise adopt the technology. Experience with large-scale industrial filtration shows that vacuum belt filter systems meet the needs of many modern users, exceptions being the inability to effectively dewater tailings at altitude and/or with a fine particle size distribution: a potential fatal flaw. This paper presents a case study on the utilization of the patented Viper Filtration technology on gold tailings to overcome this challenge and shares the resultant full-scale plant design, highlighting the features designed to overcome cost and scalability deterrents. This technology is a novel mechanical process which complements the vacuum pressure in dewatering the filter cake as it travels along the belt filter. This project commenced with a pilot testing program, which successfully met the objective to rigorously test, measure and record any performance improvements achieved when engaging the Viper technology. Of the two tailings products tested, gross improvements of 4.2%w/w and 5.7%w/w were achieved when compared to the conventional vacuum belt filter operation. This pilot testing facilitated measurement of operating and design data, which forms the basis of the full-scale system design and resultant equipment supply of three vibration roller assemblies for retro-fitting on the existing vacuum belt filter.

Beneficiation of recycled process water at DRDGOLD's ERGO plant, and its effect on gold recovery

SYNOPSIS To conserve fresh water resources and comply with environmental regulations, DRDGOLD, a South African gold producer re-treating surface tailings, has transitioned to a fully closed water circulation system. Consequently, the accumulation of contaminants, as well as addition of reagents, has led to changes in water composition that have compromised leach performance and overall gold recovery. A two-sample t-test confirmed a significant difference in gold recoveries between the use of Rand Water, which was used as a benchmark, and untreated process water. Atomic absorption analysis of ERGO's process water, confirmed the presence of iron, nickel, zinc, and manganese. A study of the effect of the identified contaminants on gold recovery showed that iron, nickel, and zinc have the largest negative effect on gold recovery, with iron and nickel being more detrimental than zinc. Sulphates were shown to have a possible passivation effect, which also influenced gold recoveries, although to a lesser extent than the heavy metals. Calcium, when present in excess, had a positive influence on gold recovery indicating the possible formation of a calcium aurocyanide complex. Lime softening successfully reduced the heavy metal and sulphate concentrations, and the gold recoveries obtained with the treated process water were similar to those as achieved with Rand Water. Keywords: gold tailings, re-processing, water quality, gold recovery.

Cone penetration testing on silty tailings using a new small calibration chamber

This study presents the results of the first cone penetration testing on predominately silty gold tailings in a calibration chamber, with results interpreted within the critical state soil mechanics framework. Samples were prepared in a wide range of void ratios, prioritising loose contractive states. The results are presented in terms of the state parameter against the normalised tip resistance and are compared with some common state parameter interpretation screening tools. The modified laboratory equipment, sample preparation methods and characterisation of the tested silty tailings are described along with the adapted void ratio tracking method.

A REVIEW OF DEPOSIT VELOCITY PREDICTION METHODS FOR MEDIUM PARTICLE SIZE SLURRIES IN PIPES

Methods of predicting the deposit velocity for wide particle size slurries with maximum particle size up to about 1 mm and maximum d50 size around 0.3 mm are outlined. These slurries generally possess non-Newtonian properties, typically modelled as Bingham plastics, and typically flow pseudo-homogeneously in turbulent flow down to the deposit velocity. Because they flow pseudo-homogeneously, pressure gradient prediction is relatively easy once a suitable operating velocity is selected. Consequently, the deposit velocity is the most important parameter as it determines the operating velocity. Beginning with Durand and Condolios [6], the historical development of the major methods for predicting the deposit velocity for mono-size particles in water are first reviewed, and their advantages and limitations discussed. Methods of extending predictions to mono-size particles in viscous Newtonian fluids are then reviewed. Next, prediction techniques relevant to deposition are reviewed for non-Newtonian slurries. These include prediction of the transition velocity between laminar and turbulent flow, and the critical pressure gradient required to prevent deposition under laminar flow conditions. Finally, these prediction techniques are combined to apply to minus 1 mm, wide size distribution, viscous slurries, commonly encountered in the mining industry. Two deposit velocity prediction techniques for these types of slurries are discussed. The first technique, based on determining the inherent viscosity of the slurry and assuming the weighted mean particle size of the total slurry represented the relevant coarse particle dimension, was found to predict performance in an operating 593 mm ID pipeline. The second technique, based on assuming the minus 75 µm portion represented the “carrier” fluid and assuming the median size of the plus 75 µm portion represented the relevant coarse particle dimension, was found to give very good predictions of the observed deposition trends of Goosen and Paterson [8] for a minus 300 µm gold tailings tested in 100 mm, 152 mm and 242 mm test loops.

Experimental Study on Zhaoyuan Gold Tailings-Based Aerated Concrete

This paper discusses the preparation of aerated concrete using the massive gold tailings stockpiled in Zhaoyuan as the main raw material with a mixture of cement, lime, gypsum, and Al powder. Contents of gold tailings, gypsum, lime, Al powder, and water-material ratio are used as impact factors for orthogonal array test to determine the most optimized formulation. The formula optimized through orthogonal experiments is: gold tailings, 58%; lime, 26%; cement, 11%; gypsum, 5%; Al powder 0.048%; water-material ratio, 0.59. Based on this formula, the specimens have the highest strength and specific strength, being 6.15 MPa and 9.96 MPam3• kg−1, respectively. Dry apparent density is 617.5 kg/m3, which is in compliance with the requirements of the national standard on dry apparent density to be smaller than or equal to 625 kg/m3.

Static liquefaction behaviour of gold mine tailings

Static liquefaction failure of tailings impoundments has been a persistent issue for the mining industry for many decades. In this study, the monotonic shearing response and instability of gold tailings are examined through a series of constant-volume and drained direct simple shear tests on slurry-deposited and moist-tamped specimens. The experiments were carried out on both the silt and the sand tailings produced at the mill and separated for use in dam construction. Laboratory shear wave velocity measurements made by means of bender element tests were also used to relate the shearing response and strength of the tailings to an in situ geophysical measurement. Specimen fabric differences produced by the different preparation methods do not translate into significant differences in the critical state line, liquefaction triggering or post-liquefaction strength for the sand tailings. Additionally, common trends of undrained yield and post-liquefaction strength ratios with state parameter were observed for both the sand and the silt tailings despite their different fines contents. An empirical method to evaluate the onset of instability and the post-liquefaction strength of the tailings using shear wave velocity is proposed.

Potential Beneficiation of Readily Available Gold Tailings and Paper Wastes: Development of a New Building Material

Gold mine tailings (GMT) generated from gold mining processes are readily available in South Africa. The generated GMT is disposed to the environment by land filling. This occupies considerable land area, which subsequently results into environmental pollution. Numerous industries use paper for a number of applications on daily basis and its generation is inevitable. Unrecycled paper ends up in the landfill, which has a negative impact on the environment, as it is not degradable. This study investigated the blending of GMT and waste paper for the production of building bricks (papercrete). The chemical composition of GMT in terms of elemental, mineralogy and micrograph before and after paper stabilization was examined. Developed composites were cured for 7, 14, 21, 28 days, and the unconfined compressive strength (UCS) and absorption tests were conducted. The results obtained showed an improvement in both the UCS and the water absorption of the bricks with the increment in curing period. The brick cured for 28 days had the highest UCS of 7.76 MPa and the lowest water absorption of 80.43% when compared to the bricks cured for 7,14 and 21 days. The developed papercrete was relatively light in weight; however, they proved not to be suitable for outdoor walls and water logging areas due to their high capability to absorb water.

Combined effects of green manure returning and addition of sewage sludge compost on plant growth and microorganism communities in gold tailings.

Remediation of gold tailings is often difficult due to their extremely barren nature and highly heavy metal concentrations. Returning green manure and applying sewage sludge compost have the beneficial effects of providing nutrients and improving the soil environment. The effects of green manure plants, alfalfa (Medicago sativa L.), ryegrass (Lolium perenne Linn.), and tall fescue (Festuca arundinacea), returning in situ on nutrients, bioavailability of trace metals, and community structure of microorganism in gold tailings amended with 0%, 5%, and 10% (weight/weight) sewage sludge compost on the top 4 cm of tailings (SSC-5, SSC-10) were investigated in a pot experiment. The results showed that the plant biomass and microbial biomass carbon in tailings significantly increased in the treatments with sewage sludge compost. The available N and available P and the availability of Zn decreased markedly with the returning of alfalfa and ryegrass. Moreover, through high-throughput sequencing, it was found that the returning of alfalfa had positive effects on the bacterial community richness but a negative impact on the fungal community richness. The microbial community diversity was reduced in the treatment without sewage sludge compost amendment and with alfalfa returning. However, the microbial community diversity was enriched in the treatment of alfalfa returning with sewage sludge compost. In each plant species, 9 dominant bacterial phyla and 10 dominant fungi phyla could be detected. Returning alfalfa green manure and applying sewage sludge compost led to a relative increase in the abundance of Proteobacteria and Ascomycota. These results demonstrated that returning alfalfa and applying sewage sludge compost could be effective in the ecological restoration of gold tailings.

Oxidative leaching of refractory sulphidic gold tailings with an ionic liquid

The effect of temperature in the range of 20–65 °C on gold extraction from refractory gold tailings containing pyrite in 20% (v/v) of 1-butyl-3-methylimidazolium hydrogen sulphate [Bmim+HSO4−]-water solution with thiourea as complexing agent and iron(III) sulphate oxidant, at pH of 1 was examined for 12 h leaching time intervals. The experimental results revealed that the extraction of gold improved by increasing the temperature. The effect of time showed that a substantial amount of gold extraction took place during the first day of extraction and thereafter very little gold extraction occurred. The ionic liquid [Bmim+HSO4−] is water soluble and in aquatic solution can act like a Brønsted acid by releasing H+ ions. The apparent activation energy (Ea) was calculated based on the Arrhenius theory and it suggests that the kinetic process of gold leaching with this acidic ionic liquid follows shrinking core model with mixed and diffusion controlled reaction regions having Ea of 17.97 kJ/mol and 27.17 kJ/mol, respectively. In the SEM image of the solid residue of the leached sample some pores appeared on the reactive pyrite particles, whereas the pyrite particles in the unleached sample looked smooth. Additionally, Raman spectra detected sulphur shifts in the recorded spectra of the solid residue after leaching which can be an indication of the formation of a product surface layer of elemental sulphur, which supports the diffusion through a product layer in the kinetic model.

Excess pore pressure generation during slurry deposition of gold tailings

ABSTRACT Excess pore water pressure (PWP) in gold tailings, deposited in the laboratory in a settling column, was observed for various rates of deposition. Rates of rise (vertical increase in height of settled tailings over time expressed in metres per year) of 10 m/yr and 20 m/yr were evaluated by depositing the gold tailings in layers. The maximum deposition rate achieved in the laboratory by depositing tailings to the full height of the settling column at once (full depth deposition) was also investigated. Maximum excess PWPs of 6 kPa generated within 3 to 9 minutes from the start of tailings slurry deposition were recorded. 90% of the maximum generated excess PWPs dissipated within the first 10 hours for coarse tailings and 30 hours for fine tailings. Dissipation of the remaining 10% occurred within 1.1 days and 10.4 days respectively. The excess PWPs were the highest for full depth (FD) deposition. Excess PWPs at an rate of rise (RoR) of 20 m/yr and 10 m/yr were 50% and 30% of the FD deposition. Dissipation of the excess PWPs occurred mostly during the sedimentation phase. It is shown that excess PWP build up on its own cannot be the mechanism that limits the RoR of gold tailings dams.

Coupling elasto-plastic behaviour of unsaturated soils with piecewise linear large-strain consolidation

Slurried soils or tailings are often deposited in layers that undergo complex stress paths in terms of desiccation and loading, as a given layer may undergo variable degrees of desiccation before burial by subsequent layers, which has implications for geotechnical stability and geo-environmental performance. Proper analysis therefore requires not only an effective coupling of unsaturated flow with large-strain consolidation, but also inclusion of hysteresis effects. This paper presents the development and testing of a coupled unsaturated flow–large-strain consolidation model, UNSATCON, initially formulated for only monotonic dewatering, to include such effects. UNSATCON operates by a novel numerical algorithm that ensures mass conservation and handles the saturated/unsaturated transition smoothly. Differently from conventional integration schemes commonly embedded in finite-element formulations, this algorithm, tracking the void ratio change explicitly for large deformation, is shown to be applicable for most constitutive models of unsaturated soils under one-dimensional or isotropic stress conditions. Three constitutive models are implemented: a modified state surface model and the original and a minor variant of the Glasgow coupled model (GCM). The numerical model is evaluated using a recently published experimental study on multilayer deposition of thickened gold tailings. The model adequately reproduces the essential features of the dewatering processes, including the irrecoverable deformation induced by desiccation, the interlayer water exchange governed by deformation and deformation-dependent hysteretic retention behaviour. All three implemented constitutive models can reasonably simulate these experimental observations, despite some trivial discrepancies in magnitude. Point-level inspection, however, reveals some fundamental differences that may have important practical implications. For example, the additional plastic strain that occurs in GCM type models over multiple wetting–drying cycles may explain observed trends in increased strength in the simulated experiment.

Pyrite enhanced chlorination roasting and its efficacy in gold and silver recovery from gold tailing

Developing cost-effective, efficient and environmentally friendly recovery process for gold tailings is imperative for environmental protection and resource recycling. In this paper, we developed a pyrite enhanced chlorination roasting technology and it was first used to dispose gold tailing. Here, we show that addition of pyrite could promote calcium chloride oxidation to produce chlorine gas, and the process realized the recovery of gold (Au) and silver (Ag) from gold tailing in an efficient and environmentally friendly way. Notably, addition of pyrite also has the potential to enhance the chlorination roasting in other fields. The experimental results confirmed that 86.93% Au was recovered by pyrite enhanced chlorination roasting under the roasting temperature of 900℃, however, without pyrite the value only of 44.27%. In addition, FeS2 and CaCl2 were converted to CaSO4 and Fe2O3 during the pyrite enhanced chlorination roasting while gaining Cl2 to extract Au and Ag from the gold tailing. The effects of different parameters on the recovery efficiencies of Au and Ag were examined. Through this technology the recovery efficiencies of Au and Ag could reach 98.56% and 87.92%, respectively, under the optimal conditions.

Results of a critical state line testing round robin programme

A critical state testing round robin programme was carried out on sandy silt gold tailings. This involved 15 laboratories around the world testing a sandy silt tailings to infer its critical state line (CSL). Methods to be used were intentionally not supplied to participants, to enable the current methods being employed in industry and academia to be obtained in an unbiased manner. All but one of the laboratories involved in the study used the moist tamping sample preparation technique, generally to produce loose, contractive specimens. Void ratio was measured using a variety of means, including cell calibration, end-of-test water content and end-of-test soil freezing (EOTSF) to assist in measuring the final water content. Of the 15 entries, four were excluded from the primary comparison owing to various issues that appear to have led to their divergence from most of the entries received. Of the remaining entries, the best reproducibility was produced by laboratories that used EOTSF to measure void ratio. Most other test procedure variations appeared to have a negligible effect, with the exception of fixing of the top platen and possibly sample size. A CSL elevation range of 0·04 void ratio for laboratories using EOTSF was observed.

Pemisahan Logam Tanah Jarang dari Limbah (Tailing) Emas Poboya dengan Metode Pengendapan

Gold tailings are waste generated from gold mining activities and contain minerals and rare-earth metals (REM) that are much needed in current technological developments. This research was conducted to determine the REM content contained in Poboya gold tailings, through the destruction process using sulfuric acid and precipitation using ammonium hydroxide. The results were showed that the level of REM contained in Poboya gold tailings was 6-7%. REM oxide content analysis performed with Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) obtained 6 types of REM with the main REM levels namely Terbium (Tb): 77-80% dan Lanthanum (La): 13%, as well as other rare-earth metals with smaller amounts of Europium (Eu): 4-5%, Cerium (Ce): 2%, Neodymium (Nd): 0.02% and Gadolinium (Gd): 0.02%. Poboya gold waste can be used by the community as a source of REM and used in various industries.
 Keywords: Gold tailings, rare earth metals (REM), destruction, precipitation

Preparation of Ca–Si–Al–Mg porous ceramics by Co-operation of Ca&Mg-contained soda residue and altered rock gold tailings

Utilization of two solid wastes of altered rock gold tailings and soda residue as main raw materials, and investigated the effects of soda residue, Al2O3 and MgO contents on bulk density, compressive strength and crystal phase of porous ceramics. The results showed that porous ceramics with the main crystalline phases of diopside can be prepared from high solid waste content (gold tailings + soda residue accounting for 95%) at 1170 °C. The addition of MgO made the final product generate augite phase, which improved the compressive strength of the porous ceramics. The best results of bulk density and compressive strength of the final product are 0.50 g/cm3 and 6.02 MPa respectively.