Gold Tailings Research Articles

Self-cementation of gold tailings activated by nonthermal plasma irradiated calcium (hydro)oxide

The alkalinity of CaO is commonly insufficient in alkali-activating raw soils or minerals for the formation of cementation or geopolymerization. In this study, nonthermal plasma (NTP) irradiation was employed to activate traditional CaO to enhance its efficacy in alkali activation and further intensify the self-cementation of gold tailings. The solidification/stabilization (S/S) of the gold tailings-based matrix activated by NTP-CaO was better than that of CaO. The NTP irradiation enhanced the surface hydroxyl groups and oxygen atoms, decreased the binding energy, formed nanoparticles, and significantly changed the morphologies of the calcium activator. The dosage of the NTP-irradiated CaO (NTP-CaO) directly affected the self-cemented solidification/stabilization of gold tailings. The Johnson-Mehl-Avrami–Kolmogorov model was appropriate for analysing the NTP-CaO-activated geopolymerization kinetics of gold tailings. Three-dimensional (3D) structural minerals covered with small pores were determined in the NTP-CaO-activated cemented samples. The employment of NTP-CaO facilitated the formation of aluminosilicate geopolymers during the self-cementation of gold tailings according to comprehensive characterization strategies. The study achieves the efficient self-remediation of gold tailings by activating calcium precursors, which further solves the contradiction between salinization and alkali activation in the field of noncalcined cementitious materials.

Effect of Gold Tailing Addition on the Mechanical Properties and Microstructure of Foam Ceramics

Tailings, with their low utilisation rate and value, pose an urgent problem that needs to be solved. This study focused on foam ceramics and glass granules, which were prepared using gold tailings as the main raw materials, and the prepared microcrystalline foam ceramics were investigated. The optimum sample (S6) of foam ceramics consists of 77 wt% of gold tailings, 6 wt% of talc, 9 wt% of bentonite, 2 wt% of calcite, 0.9 wt% of foaming agent and 0.6% of water reducer. The optimum foaming temperature is 1190 °C, and the holding time is 60 min. The compressive strength and bulk density of the samples are 7.4 MPa and 396.4 kg/m3; nucleation temperature, crystallisation temperature, and crystallisation activation energy of glass particles are 700 °C ± 50 °C, 1100 °C ± 50 °C, and 1572 kJ/mol, respectively. Microanalysis results showed that the crystal phases of foam ceramics were mainly quartz, calcium silicate, and aluminium silicate, and crystallinity increases with increasing gold tailing content. Wollastonite appeared in the crystalline phase of microcrystalline foam ceramics. When the glass granule addition reached 30% (2–3 samples), the compressive strength was increased by 19% (8.81 MPa), and the pore size distribution was more uniform.

Experimental analysis on cyanide removal of gold tailings under medium-temperature roasting

The cyanide content of gold tailings exceeds the standard seriously due to the cyanide extraction process. In order to improve the resource utilization efficiency of gold tailings, a medium-temperature roasting experiment was carried out on the stock tailings of Paishanlou gold mine after washing and pressing filtration treatment. The thermal decomposition rule of cyanide in gold tailings was analyzed, and the effects of different roasting temperatures and roasting durations on cyanide removal efficiency were compared. The results show that when the roasting temperature reaches 150 °C, the weak cyanide compound and free cyanide in the tailings begin to decompose. When the calcination temperature reached 300 °C, the complex cyanide compound began to decompose. When the roasting temperature reaches the initial temperature of cyanide decomposition, the cyanide removal efficiency can be improved by prolonging the roasting time. After roasting at 250–300 °C for 30–40 min, the total cyanide content in the toxic leachate decreased from 3.27 to 0.01 mg/L, which met the water quality standard of III class in China. The research results provide a low-cost and efficient way for cyanide treatment, which is of great significance for promoting the resource utilization of gold tailings and other cyanide-containing wastes.

Bio-Assisted Improvement of Shear Strength and Compressibility of Gold Tailings

Safe storage of mine tailings has challenged engineers as shown by numerous historical tailings dam failures. While the storing of tailings behind tailings dams is the most practical containment solution, poor mechanical characteristics (low strength and high compressibility) of these waste materials raises serious concerns regarding the stability of tailings dams. In this study, the microbially-induced calcite precipitation (MICP) technique is used to treat gold tailings. Accordingly, tailings were enriched with Sporosarcina pasteurii and flushed with different concentrations of cementation solution to find the CaCl2 amount that produces the highest shear strength in studied tailings. Their shear strength and compressibility were measured in direct shear and one-dimensional oedometer tests and compared with those of the untreated tailings. Results showed that the 50 mM CaCl2 cementation solution proved the most effective treatment solution with respect to MICP, reducing compressibility of tailings by about 300% when loaded up to 800 kPa and improving shear strength by 140%. X-Ray Diffraction (XRD) analysis and Scanning Electron Microscope (SEM) images of treated samples further illustrated the effects of MICP on the composition and structure of the tailings specimens.

Cost-Effective Preparation of Gold Tailing-Based Aerogels for Efficient Adsorption of Copper Ions from Wastewater

Water pollution caused by heavy metal ions has attracted worldwide attention. In this work, gold tailings were used as raw materials and the sol–gel method combined with the atmospheric pressure drying method were used to achieve the low-cost preparation of a silica aerogel. (3-Aminopropyl) triethoxysilane (APTES), ethylenediaminetetraacetic acid disodium salt (EDTA-2Na), and chitosan were used to modify the silica aerogel, which was then used as an adsorbent for the adsorption of copper ions in wastewater. The adsorbent type, adsorption time, copper ion concentration, and pH value were investigated as variables to explore the best adsorption conditions. The adsorption mechanism was also elaborated on. The crystal structure, surface morphology, surface functional groups, chemical composition, and specific surface area of the aerogels and the modified aerogels were characterized by various physiochemical characterizations such as XRD, SEM, FT-IR, XRF, and BET. The results showed that the prepared silica aerogel contained 91.1% SiO2, mainly amorphous SiO2, and amino and carboxyl groups. Other functional groups were successfully grafted onto the silica aerogels. The original silica aerogels and modified silica aerogels had a large specific surface area, total pore volume, and pore diameter. When copper ions were adsorbed by the chitosan-modified silica aerogels, the adsorption capacity of the copper ions was the highest (33.51 mg/g) under the conditions of a copper ion concentration of 100 mg/L, a pH value of 7, and an adsorption time of 2 h. The adsorption of Cu2+ was mainly due to the ion exchange and electrostatic gravity.

Strength and microstructure of cemented paste backfill modified with nano-silica particles and cured under non-isothermal conditions

A series of mechanical and microstructural tests and monitoring experiments are performed on different cemented paste backfill (CPB) specimens made with different types of tailings (silica tailings, gold tailings) to investigate the effects of adding nano-silica (SiO2) particles on the strength and microstructure (pore structure, mineralogical composition) of CPB cured under isothermal and non-isothermal conditions that simulate the field thermal curing conditions of CPB structures. The results show that the CPB with nano-SiO2 (NS-CPB) has a higher strength and finer pore structure than the control samples for all curing times and in all test conditions. Nano-SiO2 particles are effective in increasing the UCS of CPB in isothermal room conditions and non-isothermal field curing conditions. The increase in mechanical performance is higher when CPB is cured under non-isothermal conditions. Most of the increase in strength of the NS-CPB occurs at the early ages (3 days) of curing. The reason for the improvement in the mechanical strength is due to increase in binder hydration and the filler effect of the nanomaterial, which are in agreement with the results from microstructural analyses and electrical conductivity (EC) measurements. It is also found that the increase in temperature due to field thermal curing conditions greatly affect the strengthening properties of nano-SiO2. The NS-induced pozzolanic reactions are much more sensitive to higher temperatures compared to Portland cement hydration. The strengthening properties of the nano SiO2 are affected by the sulphate content in the tailings due to sulphate attacks (inhibition of cement hydration by sulphate ions), as less CH is available for pozzolanic reactions and C-S-H production. The findings presented in this manuscript will help to provide a better understanding of the behaviour of CPB and design a more cost-effective CPB modified with nano SiO2 particles.

Mechanical and microstructural characteristics of cemented paste tailings modified with nano-calcium carbonate and cured under various thermal conditions

ABSTRACT This paper focuses on the evaluation of the strength development and microstructure of nano-calcium carbonate (CaCO3) cemented paste backfill experimentally cured under isothermal conditions at room temperature and non-isothermal conditions in the field. A series of mechanical (uniaxial compressive strength, UCS) and microstructural (thermogravimetric, mercury intrusion porosimetry, scanning electron microscope) tests as well as monitoring experiments are experimentally conducted on cemented paste backfill (CPB) specimens with and without nano-calcium carbonate and cured at different times and under isothermal or non-isothermal conditions. The results show that the addition of nano-CaCO3 particles to CPB significantly improves its mechanical strength, irrespective of the thermal curing conditions (isothermal, field non-isothermal conditions). However, the impact of nano-CaCO3 particles on the increase in strength of CPB is only effective or significant at the early ages (curing time≤7 days). It is also found that the higher temperatures improve the accelerating effect of nano-CaCO3 much more than they accelerate the PCI hydration reactions in the first 3 days. Moreover, it is also found the sulphate ions present in the natural gold tailings negatively affect the mechanical performance of nano-CPB and reduced the accelerating effect of nano-CaCO3 due to sulphate attacks.

Environmentally friendly disposal of the full components of gold tailings: feldspar recovery and cemented filling

ABSTRACT Due to the extremely low-grade of gold in natural ores, a huge amount of gold tailings is produced in the beneficiation progress, which caused the disposal of tailings becomes extremely urgent because of the increasingly stringent environmental protection factors. The present study focuses on the innovative full component disposal of gold tailings, which including the recovery of useful feldspar and safe filling of the remaining low-value component. However, the Fe content of feldspar concentrate is strictly limited, and the Fe removal process is preferred. Firstly, a clean physical (physical-chemical) separation method, magnetic separation, and flotation were combined to remove harmful Fe elements. In addition, Fe removal characteristics of narrow particle size were analyzed. Subsequently, the deslimed gold tailings (+0.045 mm) were used for the recovery of feldspar by flotation in acidic environment. Finally, the ultrafine grained tailings (−0.045 mm), flotation tailing, and iron impurity were backfilled underground by cementation. Separation results show that magnetic field strength and particle size have a significant positive correlation with Fe removal. As the particle size decreases from 0.5–0.25 mm to −0.045 mm, the total Fe content (TFe) increases from 0.23% to 0.35% under 1.4 T field strength, accompanied by the reduction of TFe removal from 68.73% to 61.34%. Flotation can further reduce the TFe to 0.09%–0.21%. Further, feldspar concentrate was successfully recovered with dodecylamine as collector. The grades of Na2O and K2O can reach 7.55% and 3.73% with dosage of 1000 g/t, with recovery of 86.63% and 74.63%. When the tailings pulp concentration is greater than 56%, the curing strength can exceed 0.5 MPa at 3 d. Therefore, feldspar concentrate meeting ceramic standards with whiteness of 58.63 is obtained, and the remaining low value components are filled back to the ground, making it a secondary resource rather than a waste with environmental threats.

Prediction of Gold associated Mineral worth: An application of mathematically driven artificial neural network technique

The elemental composition of other associate minerals existing with gold is a significant asset that defines the amount of additional economic contribution that can be obtained from the gold tailings. The elemental composition is a needed factor in increasing the economic value of gold run-off and getting a clear estimation for the quantity of value-added elements in each tonne of gold sand scooped during the separation process. In this study, the artificial neural network (ANN) modeling technique was used to develop an economic worth prediction model for 10 gold-associated minerals. The developed models have a 1:7:10 architecture and were trained using the ANN Bayesian regularization training algorithm. According to the root mean square error values, the results revealed that the predicted values of the associated minerals are closer to the measured values. Also, the developed model prediction performance was found to be appropriate for the estimation of gold-associated mineral economic benefits based on the high coefficient of determination and variance account. The model performance evaluation results show that the developed ANN models are suitable for economic estimation of gold-associated mineral worth.

Phytoremediation and Nurse Potential of Aloe Plants on Mine Tailings

Mine tailings are a source of potentially toxic metals (PTMs) worldwide. Phytoremediation is a low-cost green technology that uses metal-tolerant plants to extract these contaminants and rehabilitate the soil. In mine tailing restoration efforts, it can be beneficial to introduce species that can facilitate the colonization of other plants (i.e., nurse plant syndrome). In this study, the phytoremediation and nursing potential of two species adapted to metalliferous soil, Aloe burgersfortensis and A. castanea, were evaluated for the first time. An experiment was performed with aloe plants grown in pots containing potting soil, platinum tailings, and gold tailings. Leaves were assessed for bioaccumulation of PTMs. Seeds of Bermuda grass and African daisy, two successional pioneers, were planted with the aloes and had their developmental parameters evaluated after 30 days. Allelopathic effects were also assessed, with seeds of the pioneer plants infused with root extracts of the aloes from the different soil treatments. A. castanea demonstrated greater potential for the bioaccumulation of Cd, Co, Mn, Ni, and Zn in the tailings. The presence of aloes benefited germination rates, leaf count, length, and plant biomass of grasses and daisies in the mine tailings, without significant allelopathic effects. Therefore, aloes-especially A. castanea-should be employed in the rehabilitation of metal-contaminated soils to extract metals and to aid the establishment of other species to enhance the phytoremediation processes.

Mechanical and Hydration Characteristics of Stabilized Gold Mine Tailings Using a Sustainable Industrial Waste-Based Binder.

Sustainable resource utilization of tailings is a long-term challenge. Therefore, a novel waste-based binder is proposed in this study to stabilize/solidify gold mine tailings (GMTs). This binder is composed of fly ash (FA), ground blast furnace slag (GBFS), and metakaolin (MK) activated with mixed calcium carbide residue (CCR) as well as pure reagent grade chemical, sodium hydroxide (SH, NaOH), and plaster gypsum (PG, CaSO4·2H2O). The mechanical properties and hydration of stabilized tailings with curing period were investigated. Tests included triaxial compression test and nitrogen adsorption to evaluate the strength of the stabilized tailings and microstructure. The results show that the addition of the waste-based binder yields significant improvement in shear strength. Strain softening occurred for all cured samples, and a local shear band can be observed in all failed stabilized samples. Based on the relationship between strength and curing period, it can be speculated that the hydration reaction of the sample ends after around 40 days of curing. A bimodal pore-size distribution was observed in all solidified/stabilized samples. FTIR and 27Al MAS-NMR were used to analyze hydration products. The strength improvement of stabilized tailings was mainly attributed to the formation of ettringite and C-S-H gels after various polymerization reactions. These new hydrates bind tailings particles and fill the pores to form a more stable structure, which supplied superior mechanical properties. This paper can provide a theoretical basis for exploring the application of the industrial waste-based binder to modify the mechanical properties of gold tailings.

Evaluating the performance of three sensor types for long-term measurement of suctions in gold tailings

A key aspect of the stability of a tailings dam is the pore pressure regime within the dam. Although gold tailings can exist in an unsaturated state in the field, the measurement of negative pore pressures (matric suctions) in active gold tailings dams is not common. One of the reasons for this may be the uncertainty regarding the ideal sensor type that should be used due to the shortcomings of various types of sensors. To investigate this, a long-term Drying Box experiment was conducted in the geotechnical laboratory at the University of Pretoria. Three sensor types were assessed: a commercially available water potential sensor and two versions of the TUKS tensiometer – a high capacity tensiometer designed and constructed at the University of Pretoria. Gold tailings was deposited in a slurry form and allowed to desiccate. The response from the three sensor types as a result of the change in suctions due to drying and subsequent re-wetting were observed. It was found that the TUKS tensiometer with the steel casing provided rapid, reliable, long-term suction readings. This sensor type is therefore recommended for long-term measurement of suction in gold tailings.

Pore pressure response during tube sampling in gold tailings

Capturing the in-situ state of mine tailings is important in determining its behaviour under loading for evaluating the risk of failure of tailings dams. Obtaining a high-quality undisturbed sample through tube sampling is thus of great value to the responsible engineer. However, the sampling process itself disturbs the soil and changes its state. Since soil behaviour is driven by effective stress, one method to evaluate the disturbance induced during tube sampling is to monitor the soil’s positive and negative pore water pressure response during the process. A laboratory study was conducted where tailings samples were prepared at a controlled void ratio and subsequently saturated with water. Tube samplers of different diameters were driven into the material and extracted by means of an electric actuator during which internal sample pore pressures were monitored using tensiometers. The material experienced significant instantaneous contractive and dilative tendencies during insertion. Instantaneous negative responses during extraction of the tube samplers were also measured. It was found that the largest tube sampler (100mm diameter) performed best in the study.

Constitutive modelling of instabilities and strengths of an unsaturated tailings

Instabilities mostly happen in fully saturated and loose non-cohesive geomaterials like sands or silts or tailings, but it is also possible in unsaturated geomaterials. When unsaturated they can experience a reduction in effective stress and strain soften during water (and air) undrained loading, attaining a very low residual strength. This study focuses on modelling the conditions required to cause instability in unsaturated silty tailings, giving particular consideration to the presence of air and the way it alters the ability for volume change when it remains trapped inside the tailings. A gold tailings is used to calibrate the UNSW boundingsurface plasticity model. The effect of air, including the volumetric change caused by air compression, the alteration of air pressure, the contribution of suction to the effective stress, and suction hardening, are explored. Collapse lines (sometimes referred to as instability lines or flow liquefaction lines which represent boundaries between stable and potentially unstable stress states) in the 𝑞𝑞 − 𝑝𝑝′ plane are explored. The undrained shear strength ratios and slopes of the collapse lines are compared to those of other tailings andsands when unsaturated.

The influences of partial saturation on cone penetration tests in silty gold tailings

Laboratory-controlled cone penetration test results of a silty gold tailings in a variety of saturated and unsaturated states, obtained using two calibration chambers, are presented then interpreted using a state parameter-based approach. The research was conducted as part of the TAILLIQ project (tailliq.com), funded by the Australian Research Council and six mining companies, and involving four Australian universities.Cone penetration resistances, which increase due to the presence of suction when the tailings are unsaturated, can be normalised using the initial mean effective stress to establish a relationship with the initial state parameter. The relationship is applicable to saturated and unsaturated conditions, as long as the presence of suction hardening as well as the influence of suction on the mean effective stress are accounted for, and as long as the cone penetrations occur under pseudo drained conditions. The relationships enable state parameters and void ratios to be back-calculated from normalised cone penetration resistances.

Strain Softening response of loose unsaturated tailings samples in undrained triaxial tests

For a soil that is contractive and strain softening at fully saturated conditions the question remains on which degree of saturation can trigger a strain softening response. A common engineering practice is to adopt a saturation threshold (e.g., 85%) and then assume a fully saturated response when saturation is above that value. This study aims to understand how the strain softening response change when tailings are not fully saturated and to propose a systematic method for determining the saturation threshold. A restraint when preparing unsaturated loose samples is that it is likely to have collapse during flashing, thus changing void ratio and making comparisons between different degrees of saturation problematic. A simple procedure to obtain loose samples at different degrees of saturation but at similar post-flushing void ratios is explained and preliminary results of undrained shear strength obtained for gold tailings in triaxial device are presented and discussed.

Accelerating gold extraction from refractory gold tailings via NH4HF2 pre-treatment

Gold tailings are secondary resources, however, a suitable method to extract the remaining gold has not yet been found. Thus, this study investigated that a gold tailings was pretreated with ammonium bifluoride, which promoted recovery of the remaining gold from the tailings. Ammonium bifluoride affecting the leaching effect may be due to the synergistic effect of fluorine and hydrogen ions. The mechanism was researched with the help of scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The results indicated that ammonium bifluoride interacted with the silica-bearing mineral in the tailings, which made the surface of the tailings become rougher and more cracks, and thus provided some channels for leaching reagent and exposed the occluded gold, largely facilitating gold dissolution. The preferable pre-treatment conditions were shown as NH4HF2 concentration = 0.7 mol/L, liquid to solid ratio = 5, the temperature = 25 °C, and the time = 4 h. The gold extraction efficiency increased by 48.45 % under the optimized pre-treatment conditions. Additionally, ammonium bifluoride proved to be an environmentally friendly, efficient, and low-costed pre-treatment reagent, being well-suited for promoting gold extraction from gold tailings.

Use of cavitation to enhance the leaching kinetics of refractory gold ores

ABSTRACT The cyanidation process for refractory gold ores has been the subject of numerous investigations aimed at improving gold recovery and leaching kinetics. From recent literature investigations, hydrodynamic cavitation has been found to be a promising new approach which may modify the cyanidation processes. In this study, this approach results in the enhancement of mass transfer kinetics in multiphase fluid streams due to impacting two pulps streams against one another in a vessel called the Jetleach reactor. In this work, the Jetleach reactor was applied to a flotation concentrate from a South African gold tailings processing plant (Ergo) where an improvement of almost 10% in gold recovery was obtained while decreasing cyanide and oxygen consumption by almost 8% and 50%, respectively. The main reason for the improvement is surmised to be due to the generation of micro-cavitation which improves the mass transfer of oxygen and cyanide within the slurry.

Comprehensive Utilization of Tailings in Quartz Vein-Hosted Gold Deposits

The aim of this study was to develop a comprehensive technology for the utilization of tailings from quartz vein-hosted gold deposits. We investigated the recovery potential and separation process for gold, feldspar, and quartz from tailings samples collected from the Jinqu gold mine in Henan province, China. The sequence of the principal flowsheet of the comprehensive utilization of gold, feldspar, and quartz from the tailings samples was determined according to the process mineralogy and corresponding experiments. The residual gold in the tailings was extracted, and both feldspar and quartz concentrates were recovered according to the flowsheet of selective desliming, flotation of gold-bearing sulfide ore, removal of iron-containing impurities, flotation separation of feldspar, and purification of quartz. The quartz concentrate met China’s industrial standard for raw-material quartz sand for producing high-grade glass, such as cover glass for touch electronics and TFT LCD liquid crystal substrate glass. The feldspar concentrate also met China’s ceramic industry standards. The established process provides an efficient way for recovering the main valuable minerals in tailings from quartz vein-hosted gold deposits. Moreover, this study demonstrates the synthetic recovery of the same type of gold tailings.

Study on the hydration properties of a ternary cementitious material system containing activated gold tailings and granulated blast furnace slag

This paper mainly studies the hydration properties of a mechanical-chemical-thermal coupling activated gold tailings (CGT)-Cement-granulated blast furnace slag (GBFS) ternary cementitious material system. The effect of the CGT-Cement-GBFS cementitious material system on the mechanical properties and porosity of the mortar is studied. The hydration heat, hydration products, calcium hydroxide (CH) content, chemically bound water (CBW) content, micromorphology and elemental compositions of the CGT-Cement-GBFS cementitious material system are tested by Isothermal calorimeter (TA), X-ray diffractometer (XRD), Thermogravimetric analysis (TGA), Differential thermal analysis (DTA), Scanning electron microscope (SEM) and Energy dispersive spectrometer (EDS). The research results show that the CGT-cement-GBFS cementitious material system delays the end time for the induction period of the paste and reduces the main exothermic peak and cumulative hydration heat but improves the early degree of hydration of cement compared with the addition of CGT and GBFS alone. The main hydration products of the CGT-Cement-GBFS cementitious material system are C–S(A)-H gel, CH, monosulfoaluminate, ettringite and monocarboaluminate, calcium aluminate hydrate. The CH content of the CGS3 (15 wt% CGT and 15% wt.% GBFS) at 56 d was 23.25% lower than that of the pure cement sample (CGS0), but the CBW content was 3.14% higher than that of CGS0. The CGT-Cement-GBFS cementitious material system generates C–S(A)-H gel with a higher Ca/Si ratio than CGS0 in the early hydration stage. As the secondary hydration reaction proceeds, the C–S(A)-H gel shows a decrease in the Ca/Si ratio. The CGT-Cement-GBFS cementitious material system can ensure the hydration degree in the early stage, and can continue hydration in the later stage, thereby improving the overall degree of hydration. The compressive strength of CGS3 at 28 d is 48.59 MPa, which is 5.36% higher than that of CGS0. The cumulative porosity of CGS3 at 56 d is 0.89 mL/g, which is 31.75% lower than that of CGS0. The CGT-Cement-GBFS cementitious material system optimizes the pore size distribution of the mortar base on physical and chemical effects, improves the compactness of the mortar, and improves the compressive strength of the mortar. This research provides a certain reference value for the practical application of gold tailings in cement-based materials.