Tailings Material Research Articles

Cyanide within gold mine waste of the free state goldfields: A geochemical modelling approach

Cyanide, which remains the preferred chemical used in the gold extraction process, has the potential to be disposed of on goldmine tailings. South Africa has nine goldfields, producing approximately a third of the world's gold to date. The cyanide interacts with metals in the tailings environment, where Prussian blue Fe43+[Fe2+(CN)6]3 and Turnbull's blue Fe32+[Fe3+(CN)6]2 are among these. In previous studies, Prussian blue or Turnbull's blue have been found as a blue substance in tailings material. PHREEQC modelling software was used adding the mineralogical data from 16 tailings samples from the Free State goldfield. The results revealed that Prussian blue prefers to precipitate in an oxic environment and Turnbull's blue prefers an anoxic environment. It was also determined that their precipitation is affected by the availability of iron in solution. As soon as all of the iron is consumed in solution, all excess cyanide produces HCN, which is a free cyanide which volatilizes. Contrarily, Prussian and Turnbull's blue are CNSAD compounds, only dissociating in extremely low pH condition in the absence of photolysis. Ultimately, these iron-cyanide compounds are able to immobilize cyanide, preventing seepage into environments such as the ground water. This along with an anoxic environment such as mine void, keeping the pH high, may be a possible solution for cyanide remediation.

Water and environmental management in oil sands regions

Study regionOil sands regions worldwide with emphasis on rapidly developing areas of western Canada. Study focusThis article introduces scientific contributions to the special issue paper collection focusing on water and environmental management in oil sands regions. New hydrological insights for the regionTwenty-one new studies highlight current advances in understanding of hydrological processes relevant to oil sands regions, including: 1) regional assessments of water balance and hydrochemistry in lakes, wetlands and rivers, 2) on-lease investigations carried out at operating oil sands mines including mine circuits and reclaimed wetland and upland sites, 3) off-lease impact investigations including nitrogen emissions, lake and wetland studies, and groundwater monitoring, and 4) a paleohydrologic investigation establishing a record of water balance, chemistry, lake productivity and temperature dating back prior to industrial development. The collection emphasizes multi-disciplinary field-based approaches including use of physical, chemical and isotopic methods. Several modelling programs are also shown to be informative for specific tasks. The interplay of water quantity, water quality and vegetation characteristics is a common finding for reclamation assessments that report sensitivity of wetland vegetation to observed salinity accumulation linked to contact with buried tailings material. While all studies herein report results from the Canadian oil sands region, we posit that these investigations may provide insight into environmental challenges to be encountered worldwide, given the similar geologic settings and bitumen properties noted.

Study of the composition and properties of the beneficiation tailings of currently produced loparite ores

The increase in demand for rare earth metals and the depletion of natural resources inevitably causes the need to search for alternative unconventional sources of rare metal raw materials. The article presents the results of a study of the composition and properties of the beneficiation tailings of currently produced loparite ores. Sieve, mineralogical, chemical, and radionuclide analyses were carried out. The average content of loparite in tailings was determined. Using scanning electron microscopy, minerals-concentrators of rare earth elements in the loparite ore beneficiation tailings were diagnosed. The distribution of valuable components and thorium in the tailings was determined depending on the particle size class. The radium-thorium nature of radioactivity was established, the values of the effective specific activity of the samples were calculated. We concluded that it is necessary to develop an integrated technology for processing the beneficiation tailings of loparite ore, due to the complex and heterogeneous mineral and chemical composition of the tailings material.

Assessment of EDTA-enhanced electrokinetic removal of metal(loid)s from phosphate mine tailings

ABSTRACT Electrokinetic remediation (EKR) is a promising technique for the treatment of contaminated soils and sediments. However, the application of EKR to metal(oid)-contaminated mine wastes with varying mineralogy and physicochemical properties has not been fully characterized. This paper evaluates the potential of EDTA-enhanced EKR as a means to remove trace metal(oid)s (Cu, Cd and As) and major metals (Fe, Al and Mg) from a phosphate mine tailings material. Controlled laboratory EKR experiments were performed, in which the electrolyte EDTA concentration was varied between 0.1 and 1 M and the voltage gradient between 24 and 32 V. Migration of the studied contaminants increased proportionally to increasing EDTA concentration and applied voltage gradient, and the obtained average removal efficiencies of Al, Mg, Cu, Cd and As reached up to 29%, 10%, 26%, 28% and 22%, respectively, within a week. Differences in metal mobilization could be explained by their mineral hosts and aqueous speciation under the imposed geochemical conditions during EKR, which were corroborated by aqueous geochemical equilibrium modeling using PHREEQC. Our results suggest that EKR could be a feasible remediation option for select metal(oid)-enriched mine waste fractions following further optimization.

Development law and growth model of dynamic pore water pressure of tailings under different consolidation conditions.

Tailings dams are in danger of liquefaction during earthquakes. The liquefaction process can be indirectly reflected by the evolution rule of the dynamic pore water pressure. To study the development law of dynamic pore water pressure of tailing sand under different consolidation conditions, the evolution equation of critical dynamic pore water pressure of tailings under isotropic and anisotropic consolidation conditions was derived based on the limit equilibrium theory. Moreover, the development law of dynamic pore water pressure was expounded theoretically. The dynamic triaxial tests of tailing silty sand and tailing silt under different dry densities, consolidation ratios, and confining pressures were performed. The dynamic pore water pressure ratio and vibration ratio curves of tailings under isotropic and anisotropic consolidation were analyzed, and a dynamic pore water pressure growth index model suitable for both isotropic and anisotropic consolidation was derived. The results showed that the critical dynamic pore water pressure was positively correlated with the confining pressure and average particle size of tailings under isotropic consolidation conditions. The tailings have a limit dynamic effective internal friction angle [Formula: see text] under the anisotropic consolidation condition. The evolution law of critical dynamic pore water pressure can be judged according to the dynamic effective internal friction angle of tailing sand φd and [Formula: see text] values. The consolidation ratio significantly affects the dynamic pore pressure growth curve while confining pressure and dry density do not. For different tailing materials, the dynamic pore water pressure ratio is positively correlated with tailing particles. The dynamic pore water pressure growth process of tailing silty sand and tailing silt can be divided into two stages: rapid and stable growths. The development law of two types of tailings can be described by the dynamic pore water pressure growth index model. The research results can provide a theoretical basis for the seismic design of tailings dams in practical engineering.

Pilot-scale feasibility study for the stabilization of coal tailings via microbially induced calcite precipitation

Sustainable long-term solutions to managing tailings storage facilities (TSFs) are integral for mines to operate in a safe and environmentally responsible manner. The long-term storage of subaqueous tailings can pose significant safety, environmental, and economic risks; therefore, alternative containment strategies for maintaining geochemical stability of reactive materials must be explored. In this study, the physical and geochemical stabilization of coal tailings using microbially induced calcite precipitation (MICP) was evaluated at a laboratory pilot scale. Three application techniques simulated commonly used agricultural approaches and equipment that could be deployed for field-scale treatment: spraying on treatment solutions with irrigation sprinklers, mixing tailings and treatment solutions with a rototiller, and distributing treatment solutions via shallow trenches using an excavator ripper. Test cells containing 1.0 × 1.0 × 0.5 m of tailings were treated with ureolytic bacteria (Sporosarcina pasteurii) and cementation solutions composed of urea and calcium chloride for 28 days. Penetrometer tests were performed following incubation to evaluate the extent of cementation. The spray-on application method showed the greatest strength improvement, with in an increase in surface strength of more than 50% for the 28-day testing period. The distribution of treatment solution using trenches was found to be less effective and resulted in greater variability in particle size distribution of treated tailings and would not be recommended for use in the field. The use of rototilling equipment provided a homogenous distribution of treatment solution; however, the disruption to the tailings material was less effective for facilitating effective cementation. Bacterial plate counts of soil samples indicated that S. pasteurii cultures remained viable in a tailings environment for 28 days at 18 °C and near-neutral pH. The treatment was also found to stabilize the pH of tailings porewater sampled over the 28-day incubation period, suggesting the potential for the treatment to provide short-term geochemical stability under unsaturated conditions.

Contamination assessment and potential sources of heavy metals and other elements in sediments of a basin impacted by 500years of mining in central Mexico.

Since the middle of the 1500s, mining has been active in central Mexico. Total estimates for low-grade piles and mine tailing materials in the Guanajuato mining district (GMD) are in the range of 150 million tons, covering an area of 15 to 20 km2. GMD is located in the Guanajuato River sub-basin (GRB), which is part of one of the largest basins in Mexico (Lerma-Santiago). Previous studies on the GRB found unusually high concentrations of heavy metals in mining tailings and sediments. Geochemical and statistical methods were used here to determine the sediment's origin, background values, degree of contamination, and toxicity through different contamination indices. This analysis shows that Cu, Co, As, Sb, and Hg are higher than they are in the upper continental crust (UCC) overbank sediments without human and mining influence, because of the ore deposits and rock weathering in GRB. Geochemistry results in stream sediments show anomalies, where Hg, Cu, Zn, As, and Pb are higher than UCC because those heavy metals and trace elements (HMT) have been influenced by human activities and mineral recovery (smelting, amalgamation, cyanidation). The distribution of high concentrations of HMTs and contamination indices occur in the main channel of the Guanajuato River and downstream of the city of Guanajuato. Statistical analyses (cluster and principal component analysis) reveal relationships between Cr, Ni, Cu, and Pb, which are primarily of natural origin, related to rocks of the upper basin. The middle and lower basins are distinctive in their associations between As, Sb, Zn, Pb, and Hg. Additionally, it is recognized that the origins of Pb, Zn, and Hg are geogenic and anthropogenic. This study demonstrates how crucial it is to understand the geochemistry of various HMT sources, with both natural and anthropogenic contributions (stream sediments and rocks), in order to calculate a more realistic background in a basin with both natural anomalies and anthropogenic contamination. The basin is a regional aquifer recharge area, so the new geochemical data are important for improving basin environmental management.

Quality control in tailings resource exploration at Havelock Mine, Eswatini

Quality assurance and quality control (or QAQC) plays a key role in safeguarding the level of confidence of the data generated during mineral exploration and mine development, and is also part of the reporting code requirements for resource estimation and reporting, as well as mining investment. Implementation of good policies and working protocols in quality management will result in the generation of reliable information, which is critical for decision-making on the future of the mining project. The use of certified reference materials, i.e., standard, blank, and duplicate samples, proves effective and efficient for ensuring the level of data confidence in terms of precision, accuracy, and sample contamination. This is well demonstrated by the practice of QC in the exploration programme for the chrysotile tailings storage facilities of Havelock Mine, using 1254 samples from 53 drill-holes. Different statistical tools were applied to analyse the assay results from these samples. The outcome substantiates that the QC practice established during the Havelock exploration project is aligned to best practice guidelines in the industry. The resource delineated indicates that the tailings material at Havelock could potentially become a significant source of supply to the global magnesium market.

Mine waste as a sustainable resource for facing bricks

Circularity of raw materials starts with a zero-waste approach to any (potential) resource. The increasing pressure on the primary raw materials sector and external market dependence can ultimately lead to scarcity of natural resources. To minimise this pressure, alternative materials need to be mapped, characterised, and valorised. Construction and demolition waste and mining waste are currently the biggest waste streams in the EU27 and can lead to environmental, health, and social hazards. The purpose of this study is to evaluate the sustainable use of (clean) sulphidic mining waste materials in facing bricks.After materials’ characterisation, a company-specific blend for facing bricks has been modified on a lab scale, by partly replacing primary raw materials with mining waste materials (Plombières tailings and Neves Corvo waste rocks). The production processes, product quality, and environmental performance of waste-derived bricks were assessed and compared to standards and regulatory limits. A cradle-to-gate life cycle assessment (LCA) was performed to evaluate the environmental profiles of the best performing waste-derived bricks compared with standard bricks.Results show the suitability of using the untreated Plombières tailings material in facing brick blends, giving satisfactory technical and aesthetical properties, and complying with environmental regulations for service, 2nd life, and end-of-life stages. According to the LCA, facing bricks made with 40 wt% Plombières tailings demonstrated better environmental performances than standard bricks. The pre-treated Neves Corvo waste rock materials were unsuitable for facing bricks due to the high sulphur and metal(loid)s content that caused aesthetical and chemical-environmental problems.

Study on strength formation and frost resistance of concrete modified by molybdenum tailings

Solid waste tailing materials from molybdenum mining in China occupy extensive land areas and threaten the health of nearby residents. To address the risk and the increasing shortage of natural construction materials, using those tailings as a construction material is a potential option for the construction industry. Modified concrete mixed with other tailings materials has been widely studied. The application of molybdenum tailings modified concrete to cold regions needs to fully consider its durability. Through the concrete cube compressive strength test and rapid freeze-thaw cycle test after different standard curing time, the strength formation process and frost resistance of molybdenum tailings modified concrete are explored. On this basis, the optimal content of Mo tailing material was determined. Results demonstrated that the compressive strength and frost resistance of Mo-tailing-modified concretes increased first and then decreased with the increase in Mo tailing content. The optimal modification effect was achieved when the Mo tailing content reached 20%. Under that circumstance, the porosity of Mo-tailing-modified concrete was at a minimum before and after the freeze–thaw cycles, thus increasing mechanical and antifrost properties significantly.

Characterizing the hydraulic and transport properties of a constructed coarse tailings sand aquifer

Millions of tonnes of coarse tailings sand are produced every year as a byproduct of the bitumen extraction process in the Athabasca Oil Sands Region. These tailings materials contain residual quantities of mobile solutes, which can be transported through groundwater to downgradient terrestrial and aquatic ecosystems. The anticipated ubiquity of coarse tailings sand on the post-mined landscape necessitates the characterization of its hydraulic and transport properties. Hydraulic conductivity and dispersivity was evaluated at multiple scales, and included the first field-scale tracer test conducted in a tailings sand aquifer. Average hydraulic conductivity derived using laboratory cores, single-well response tests, and the tracer test were 3.2 m d−1, 2.9 m d−1, and 3.4 m d−1, respectively. These measurements demonstrated close agreement and were consistent with expectations of a material that experiences some grain-size segregation and homogenization due to the oil sands process and the nature of deposition. The field-scale tracer test appeared to obtain the asymptotic dispersivity of the coarse tailings sand aquifer, reaching a maximum value of 0.5 m after 18 m of displacement. Coarse tailings in the oil sands that experience similar processes of segregation, settling, and deposition on the reclamation landscape could be expected to have similar hydraulic properties.

Estimating the Potential Differential Settlement of a Tailings Deposit Based on Consolidation Properties Heterogeneity

Processing of extracted oil sands generates substantial volumes of tailings slurries. Due to the scale and inherent variability of the tailings properties, consolidation settlement is expected to occur at different rates and magnitudes across the tailings deposit. Estimating potential differential settlement of the consolidated deposit surface is an essential input for closure design. This paper presents a three-step methodology that generates multiple realizations of quasi-three-dimensional (3D) surfaces of the consolidated deposit based on the adjacent points. Each point is based on a stochastic one-dimensional (1D) large strain consolidation model developed with Monte Carlo techniques in GoldSim. The simulated surfaces provide early estimates of differential settlement based on the variability of consolidation properties expected in the tailings deposit. Comprehensive sensitivity analyses are performed for differently treated tailings material through 28 distinct scenarios to evaluate the sensitivity of the developed 1D and 3D models to consolidation input parameters over a 40-year time period. The analysis demonstrated that differential settlement is highly sensitive to tailings compressibility and hydraulic conductivity governed by the constitutive relationship parameters, and less sensitive to the solids content, specific gravity or thickness of a surcharge load. Tailings that underwent steady continuous settlement exhibited the largest degree of differential settlement.

Invertebrate metal accumulation and toxicity from sediments affected by the Mount Polley mine disaster.

On August 4, 2014, a tailings dam failed at the Mount Polley copper and gold mine near Likely, British Columbia, Canada, releasing approximately 25 M m[Formula: see text] of contaminated water and solid tailings material into Polley and Quesnel lakes. Water, sediment, freshwater scuds (Hyalella azteca), and mayfly larvae (Ephemeroptera) were collected during the summer of 2018 from Polley Lake, affected and unaffected sites in Quesnel Lake, and both mine-contaminated and clean far-field sites as references. Analytical results indicated that invertebrates from sites affected by the tailings breach had elevated metal concentrations relative to those from non-affected or reference sites. We conducted a controlled laboratory exposure to determine if laboratory-reared Hyalella azteca metal concentrations were related to field-collected water or sediments from the same sites as the field study. Half of the replicates prevented amphipods from directly contacting sediments (water-only exposure), while the other half allowed them direct access (sediment and water exposure). Whole-body Cu concentration was highest in Hyalella exposed to substrate from the most contaminated sites as well as in treatments where they were allowed direct access to sediments. Hyalella having direct access to metal-contaminated sediments showed reduced survival and growth relative to those in reference or control treatments. These results suggest that metals from the fine sediments associated with the Mount Polley mine disaster are bioavailable and potentially toxic to epibenthic invertebrates, even several years after the initial breach.

A Particle Size Distribution Model for Tailings in Mine Backfill

With the increasing awareness of sustainable mining, the cement tailings backfill (CTB) method has been developed rapidly over the past decades. In the CTB technique, the two main mechanical properties engineers were concerned with are the rheological properties of CTB slurry and the resulting CTB strength after curing. Particle size distribution (PSD) of tailings material or PSD of the slurry is a significant factor that highly influences the rheological of CTB slurry and the strength performance of CTB. However, the concentrically partial size distribution curve and existing mathematical model could not represent the PSD of tailings material. In this study, a mathematical model for the particle size distribution of mine tailings was established using three model coefficients A B and K, which mainly reflect the characteristics of particles from three aspects respectively, the average size of particles, the proportion of the coarse or the fine parts of particles, and the distribution width of particles; meanwhile, an optimal coefficient solution method based on error analysis is given. Twelve tailing materials sourced from metal mines around China were used for the model establishment and validation. The determination coefficient of error analysis (R2) for all twelve modeled PSD lognormal curves was more significant than 0.99, and the modeled PSD lognormal curves are highly consistent with the determined particle size distribution curve.

Influence of compaction on small-strain shear modulus of iron ore tailings

Understanding the geotechnical properties of iron ore tailings is one of the biggest challenges currently faced by the mining industry. The brittle behaviour of these tailings has brought the importance of small-strain stiffness to the geotechnical forefront. However, lack of knowledge and information about the behaviour of iron ore tailings still exists. The results and analysis of a laboratory programme aimed at assessing the small-strain stiffness of tailings materials are presented in this paper. The materials tested were produced during the iron ore treatment process. Bender elements were used to measure shear wave velocities and evaluate dynamic shear moduli at different effective stress levels resulting from isotropic consolidation tests. Three types of iron ore tailings with different grain size distributions were used – flotation tailings, slimes tailings and blended tailings. Reconstituted specimens were prepared at different densities (loose and dense conditions) to assess the effects of initial density (percentage compaction) on the shear modulus. The laboratory results were compared with empirical correlations for other soil types. The equations were ineffective at representing tailings materials containing large amounts of fines (slimes). The advantages and limitations of the equations are discussed and a new empirical equation that includes the degree of compaction is suggested.

Application of inspection and monitoring in the reduction of risk for mine tailings dams

Recent high-profile failures of mine tailings dams across the globe have once again raised geotechnical interest in these structures. Much of the recent discussion in the technical literature has focused on the prediction of the ultimate stress state and thus of the failure potential of tailings materials. Concentration solely on geomechanical properties is important in the understanding of the fundamental characteristics of extractive waste but limits the appraisal of risk potential in these complex and multi-faceted structures. It is evident from the author's study of failures of extractive waste facilities over a period of some 50 years that knowledge of geomechanical properties alone would not have prevented disasters in many instances. The fundamental risks posed by these structures are reviewed in this paper with respect not only to their design but also to their construction, operation and eventual closure. The analysis confirms that other crucial elements of design and construction, if neglected, potentially pose higher risks than a lack of knowledge of geomechanics alone. A broad list of risk reduction criteria that should be applied to mine tailings dams is presented and examples of where and how such neglect has resulted in recent high-profile failures are cited. A review of general risk reduction criteria is presented and compared with existing standards and guidelines.

Comprehensive Diagnosis Method of the Health of Tailings Dams Based on Dynamic Weight and Quantitative Index

As a dangerous source of man-made debris flow with high potential energy, tailings dams can cause huge losses to people’s lives and property downstream once they break, and their safety control problem is particularly prominent. The health diagnosis of tailings dams is a complex and nonlinear problem full of uncertainty. At present, the health diagnosis of tailings dams is mostly qualitative evaluation or quantitative analysis aiming at a single index, so this study puts forward a comprehensive quantitative diagnosis method of tailings dam health based on dynamic weight. Slope stability, deformation stability and seepage stability are taken as project layers, and the diagnosis index system of the tailings dam is constructed. The quantitative methods of diagnosis indexes of project layers are proposed. For the dam slope stability project, the safety factor and the reliability index of tailings dams are determined based on the Monte Carlo method, which can consider the uncertainty of tailings material parameters. For the deformation stability project, the normal operation values of deformation rate and deformation amount are determined by analyzing the in situ observation data and combining them with the numerical simulation results. For the seepage stability project, through the analysis of seepage and stability, the relationship curve between the depth of saturation line and the safety factor of anti-sliding stability is established. The norms method is used to determine the quantitative standards for the diagnosis indexes of the basic layer. Based on the analytical hierarchy process method and the penalty variable weight method, the method of dynamic weight of the project layer index is proposed. The proposed methods are applied to a practical engineering project. The results show that the methods can accurately reflect the health status of tailings dams. This study provides a new method for evaluating the safety of tailings dams.

Macro- to nanoscale mineral relationships in surficial cobalt-arsenic-bearing mine tailings of the Cobalt Mining Camp, Northeastern Ontario, Canada

ABSTRACT Arsenates, which correspond to the majority of known arsenic (As)-bearing minerals, control the mobilization of As in contaminated soils, sediments, and fluvial environments as well as in tailings and mine waste piles. Additionally, arsenate-bearing Fe-(hydr)oxides are of particular significance for the control of As mobility, as they are among the most thermodynamically stable minerals under near-neutral to alkaline pH conditions. However, in the surficial (upper 30 cm) alkaline mine tailings at the Cobalt Mining Camp in Northeastern Ontario, Canada, these phases only occur in trace amounts. This study attempts to understand this unusual mineralogical feature through an investigation of the relationships between nano- and macroscale mineralogical and geochemical features at two tailings sites (A and B) at the Cobalt Mining Camp. Sixty samples from two depth profiles (0–30 cm; i.e., one sample per centimeter) were collected at the two sites, analyzed for their major and minor chemical elements, and characterized for their mineralogical composition at the nano- to centimeter scale. The tailings material at both sites is predominantly composed of minerals of the amphibole, chlorite, and feldspar groups, as well as carbonates (calcite and dolomite). Minor phases are Co-Fe-Ni-Zn-sulfarsenides and -arsenates. The tailings material at site B contains, on average, higher concentrations of As, Co, Sb, and Zn and lower concentrations of Fe than the material at site A. Secondary (scanning electron microscope) and transmission electron microscopy studies indicate that the alteration of primary sulfarsenides to secondary arsenates may proceed in the following sequence: (1) the formation of Fe-hydroxide and -arsenate mineral surface coatings on sulfarsenides; (2) the downward mobilization of Co-Ni-Zn-arsenate and (FeOHCO3)aq species; (3) replacement of earlier-formed scorodite by Co-Ni-Zn-arsenates; (4) the precipitation of Co-Ni-Zn-arsenates on the surfaces of silicates; and (5) neoformation of Fe-rich hydroxy-interlayered minerals at greater depth, partly replacing earlier-formed Co-Ni-Zn-arsenates. These processes result in layers enriched in As, Co, Sb, and Zn (increase in Co#) and enriched and depleted in Fe (increase and decrease in Fe#) in tailings material at both sites. The TEM studies further indicate that Co-Ni-Zn-arsenates precipitate initially as nanoparticles on the surface of scorodite and detrital silicates and subsequently coarsen through Oswald ripening. The mineralogical-geochemical features depicted in this study provide a better understanding of the geochemical behavior of Co, Fe, and As in alkaline tailings and may assist in the interpretation of mineral-microbial community associations and the development of effective bioleaching strategies for the strategic element cobalt.

Basic research on the microwave absorbing properties and microwave roasting kinetic of cyanide tailings

In this study, a thorough exploration was performed on the mechanism of microwave enhancement in the treatment of cyanide tailings by the microwave chlorination heat treatment process. The improvement rate of the dielectric properties of tailing materials is rapid in the high temperature range (673–1173 K), which indicates that cyanide tailings have favorable microwave- absorbing performance. Under the action of iron oxide, the loss tangent of raw materials increased from 0.0364 to 0.1914. The heating efficiency improved significantly, from 6.73 K/min to 41.667 K/min. The kinetics experiment was performed on tailings in the two different roasting process. Compared with conventional roasting, the activation energy of the chlorination reaction of gold under the microwave roasting decreased by 32.47%. The work provides sound references for promoting the industrial application of microwave chlorination roasting on cyanide tailings.

Performance Characteristics of Cemented Tailings Containing Crumb Rubber as a Filling Material

Increasing amounts of tailings and waste rubber tires have caused threats to the environment. In order to reuse these solid wastes, this study proposed a cemented tailings material containing crumb rubber recovered from waste tires. Unconfined compression tests and thermal conductivity measurements were conducted to evaluate the feasibility and performance of the proposed cemented tailings. Results revealed that the stress-strain behavior of the cemented tailings changed by the inclusion of crumb rubber. The unconfined compressive strength of cemented tailings decreased with increasing crumb rubber content. The inclusion of crumb rubber increased the failure strain and nonlinearity index of the cemented tailings. It was found that the addition of 4% crumb rubber provided the greatest improvement in ductility. The increase of the rubber content further increased the thermal insulation capacity of the cemented tailings. The low stiffness and the dimpled surface of the crumb rubber were responsible for the reduced compressive strength and thermal conductivity of the cemented tailings. In conclusion, the crumb rubber had both positive and negative effects on the cemented tailings. In practical application, the rubber admixture amount should be flexibly adjusted for different use case to make the cemented tailings material show the most suitable performance characteristic.