Types Of Tailings Research Articles

Arsenic speciation in picromerite K2Mg(SO4)2•6H2O: Electron paramagnetic resonance and synchrotron X-ray absorption spectroscopic characterizations and implications for organic fertilizers

Picromerite K2Mg(SO4)2•6H2O (also known as schoenite, schönite, or sulfate of potash) formed from alkaline lakes by evaporation is an increasingly important chlorine-free fertilizer and has been used to produce other organic fertilizers such as arcanite K2SO4 and boussingaultite (NH4)2Mg(SO4)2•6H2O. Picromerite and boussingaultite, two Tutton’s salts, are also common secondary solid phases in diverse types of mine tailings and play important roles in controlling the mobility and bioavailability of various heavy metal(loid)s, including arsenic. In this study, picromerite crystals containing 64 ppm As have been synthesized at ambient conditions from aqueous solutions by slow evaporation. Arsenic K-edge X-ray absorption near-edge-structure (XANES) and extended X-ray absorption fine structure (EXAFS) data show that the dominant oxidation state is +5 and that As5+ occupies the S site in picromerite. Single-crystal and powder electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated picromerite reveal three arsenic-associated oxyradicals: AsO42−, AsO32−, and AsO22−. The orientations of the principal 75As hyperfine directions of the AsO32− and AsO22− radicals match the bonding directions of the SO42− groups in the picromerite structure, further supporting substitutions of their respective diamagnetic precursors AsO43- and AsO33- for the sulfate group. These AsO42−, AsO32−, and AsO22− radicals in picromerite are similar but not identical to their counterparts in boussingaultite and gypsum, suggesting that sulfate minerals are capable of sequestrating both arsenate and arsenite, with important implications for understanding the fate and bioavailability of arsenic associated with agricultural applications of organic fertilizers.

Mechanical Characteristics of Tailings in Different Depositional Zones: A Case Study of Caijiagou Tailings Pond in Shaanxi, China

This study examines the widespread practice of upstream tailings dam construction in metallurgical mines in China, conducting comprehensive testing and research on tailings from various depositional zones of the Caijiagou tailings pond. Analysis of the test results from three types of tailings reveals a systematic relationship between the mechanical characteristics of tailings and their depositional zones: the farther from the dam, the finer the tailings particles, categorized as silty clay tailing, silt tailing, and sandy silt tailing. Consistent patterns were observed in the consolidated-drained shear strength and consolidated-undrained effective shear strength of these tailings. Among these, sandy silt tailing exhibited the highest strength, whereas silty clay tailing displayed the lowest. The dynamic stress–strain relationships of all three tailings types are described using the Hardin equivalent viscous-elastic model, where the initial dynamic shear modulus and the maximum dynamic shear stress in the model increased with effective confining pressure. The damping ratios exhibited a three-stage trend with increasing dynamic strain: gradual increase, rapid growth, and then gradual stabilization. Under various consolidated stress conditions, the ratio of the damping ratio to the maximum damping ratio versus the reduction in dynamic shear modulus showed a favorable linear relationship. Under vibration conditions, the dynamic shear stress corresponding to tailings failure increased with higher effective confining pressure and consolidated stress ratio. Finally, this study summarizes the parameters and indicators related to the saturated tailings of iron mines used in the research. Our work provides a foundation and reference for the design of tailings dams and the development and utilization of abandoned tailings ponds.

Adding Agricultural Topsoil and Growing Perennial Ryegrass (Lolium perenne L.) Enhanced the Rehabilitation of Metal/loids Enriched Iron Ore Mine Tailings

Revegetating iron-ore mine tailings is difficult due to their poor physicochemical and microbial properties. This experiment aimed to improve tailings properties for better plant growth and rhizosphere activities. First, a pot experiment was conducted to assess the influence of topsoil amendment on the remediation of tailings collected from two sites (coded A and B) in Western Australia to promote the growth of perennial ryegrass (Lolium perenne L. cv Ausvic). Each pot was filled with pre-defined ratios of topsoil to mine tailings (0, 10, 20, 30, 50 and 100% w/w). Perennial ryegrass was harvested 60 days after sowing and analysed for plant growth, root morphological characteristics and metal uptake by shoots. Second, a study on biological attributes and an incubation study over 84 days were carried out. The addition of topsoil significantly decreased pH, but EC and total organic carbon (TOC) increased with an increased proportion of topsoil. Total concentrations of As, Co, Cr, Cu, Ni, Pb, Zn, Fe and Mn decreased with an increased ratio of topsoil in growth medium. The highest root dry biomass was observed in the treatments with 30% and 50% topsoil addition to tailings, whereas shoot dry biomass only increased with 50% topsoil. Total root length increased significantly with 50% topsoil addition to site A tailings. A significant increase in microbial biomass carbon (MBC) was found with 50% addition of topsoil compared with the control. Microbial quotient (MBC/TOC) decreased significantly with the addition of topsoil to both types of tailings. Metal contents in perennial ryegrass shoots decreased with the increasing rate of topsoil, but perennial ryegrass was an effective phytoextractor of Cu, Zn and Mn. Further, the incubation study revealed that 50% topsoil application increased cumulative respiration emissions in both A and B tailings after 42 days. Iron ore mine tailings can be improved in terms of physicochemical and biological attributes by adding topsoil. However, further investigation should be carried out to determine the speciation of metal/loids in amended iron ore tailings.

The Use of Acid Leaching to Recover Metals from Tailings: A Review

Mine tailings deposits are often overlooked by the industry, posing significant environmental challenges due to chemical hazards and inadequate maintenance. Nevertheless, such mineral deposits hold considerable economic potential for processing, and the adoption of innovative technologies may also address critical chemical and physical stability issues. Existing research has demonstrated the feasibility of recovering target metals—i.e., copper, iron, manganese, cobalt, zinc, and others—through the application of acid leaching techniques with consistently high yields and metal recovery rates. Therefore, a compilation was carried out from 2008 onwards, on working conditions such as leaching agent, acid concentration, oxidizing-reducing reagent, particle size, O2 pressure, stirring speed, solid–liquid ratio, temperature, and leaching time. At present, there are no reviews on the recovery of metals via acid leaching in tailings, so this study can serve as support for future researchers who want to project themselves in this area, ordering the procedures and the results obtained by the research carried out. Regarding the evaluation, it can be commented that research has shown that acid leaching of tailings has achieved recoveries of over 90% in different metals, such as Zn, Cu, and Fe, which indicates that the treatment is efficient and recommended for different types of tailings.

Health risk assessment of lead‐zinc mine tailing in Angoran, Zanjan, Iran

AbstractComprehending the characteristics of heavy metal contamination within mine tailings and its ramifications on ecological and human well‐being holds paramount importance in formulating effective preventive and ameliorative strategies. This investigation evaluates the health hazards posed by the tailings originating from the Angoran lead‐zinc mine situated in Zanjan province, Iran. The mine generates two distinct types of tailings: hot filter cake (referred to as cobalt cake or S2) and cold filter cake (nickel cake or S1). Twenty subsamples were procured from each type of tailing and subjected to analysis at the pollution research laboratory of University of Zanjan. The quantification of lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd), nickel (Ni), copper (Cu), chromium (Cr), mercury (Hg), manganese (Mn), and antimony (Sb) concentrations was accomplished through the utilization of inductively coupled plasma mass spectrometry (ICP‐MS). Carcinogenic and non‐carcinogenic risk assessment indices were computed. Moreover, the limits of detection (LOD) and quantification (LOQ) for the measurements were established using blank solutions prepared as samples for assessment. The Hazard Index (HI) surpassed unity for Pb, Zn, Cd, As, Hg, and Mn in both types of tailings, signifying non‐carcinogenic risk exposure for both children and adults. Furthermore, the HI for Pb and As also exceeded unity for adults. Consequently, both age groups were subject to non‐carcinogenic hazards, with children encountering notably elevated risks. The chief pathways for exposure to heavy metals and the ensuing non‐carcinogenic risks encompassed ingestion, inhalation, and dermal contact. The cumulative risk threshold for carcinogenic outcomes, in accordance with USEPA standards, ranged between 1.00E‐04 and 1.00E‐06. In this inquiry, the overall risk for children associated with tailing S1 and S2 amounted to 2.39E‐03 and 5.00E‐03, respectively, markedly surpassing the acceptable threshold. Furthermore, the cumulative risk for adults pertaining to tailing S1 and S2 stood at 1.27E‐03 and 4.68E‐03, respectively, indicating the presence of carcinogenic perils in the adult demographic.

Evaluation of hydrocyclonage variables aiming at the optimization of the processing of kaolin of the primary type

Kaolin is a white rock, formed basically by the clay mineral kaolinite, for presenting favorable technological characteristics has a wide industrial application. Kaolin deposits are classified geologically into two types according to their origin: primary and secondary. Kaolin from the Seridó region of Paraíba and Rio Grande do Norte is of the primary type and its processing is carried out wet, generating two types of tailings. It is considered a difficulty in the current processing of this kaolin the method of mineral classification that is carried out by vibratory sieves. The main objective of this work was to evaluate the variables that influence the hydroclinage process for the classification of kaolin of the primary type. The trials were performed on a bench scale, using the Plackett-Burman factorial design. The best results were found in the T4 and T6 tests, which presented lower values of D50 and the results of XRF indicated that the aluminum oxide contents are higher in the overflow and the silica contents higher in the underflow. The trials indicated promising results for the classification of this type of kaolin, but a good adjustment of the operational variables is needed.

Soil microbe-mediated carbon and nitrogen cycling during primary succession of biological soil crusts in tailings ponds

Tailings ponds resulting from mining operations have led to serious environmental hazards, and their bioremediation is an area of ongoing exploration. Primary succession represents the starting point of biotic community establishment and development, with soil carbon and nitrogen cycling being critical to this process. To investigate the soil microbial-mediated carbon and nitrogen cycling patterns accompanying primary succession, we selected three types of tailings ponds as study areas and set up sampling sites for different stages of primary succession. The results showed that primary succession promoted microbe-mediated carbon and nitrogen cycling. It also led to improvements in soil nutrient availability and enzyme activity. In primary succession, the main pathways of carbon cycling are 3HP and rTCA, and nitrogen cycling is nitrate assimilation. In the early stages, microbes mediated more anaerobic and microaerobic processes. As succession proceeded, the pattern of microbial contributions to the carbon and nitrogen cycles changed. As succession proceeds, the functional metabolic potential of the carbon cycle gradually rises, while the nitrogen cycle shows a dramatic increase after the accumulation of autotrophic biomass. In addition, we found a positive coupling pattern between the carbon and nitrogen cycles. These findings support the optimization of bioremediation strategies for tailings ponds.

Curing conditions effect on pore structure, compressive strength and elastic modulus of cementitious tailings backfills

As a widespread application in underground metal mines, cementitious tailings backfill (CTB) has a significant implication for recycling dangerous process tailings and enhancing the safety of mining voids. The pore structure of CTB that is liable on the features and proportions of tailings and binders is correlated to its mechanical characteristics (i.e., elastic modulus, uniaxial compressive strength). This study deals with the influence of curing conditions such as temperature (20–50 °C), stress (0–540 kPa), and time (3–28 days) on mechanical and pore structure characteristics of CTB. Fill samples were prepared in a stable solid dosage and cement/water ratio of 76% and 1/6, respectively, and put into cylindrical molds (D × H: 50 × 100 mm). A new lab instrument with adjustable curing conditions was adopted for fills. A PC-controlled mechanical press and Hg intrusion porosimetry were applied to assess CTB's strength and pore structure properties. Results suggest that, with advancing curing temperature/stress, the strength and elastic modulus of CTB show a rising trend, while its growth rates show a falling trend. CTB's porosity shows a declining trend, and it exists a good linear correlation between fill's strength and apparent porosity. CTB's strength essentially depends on the volume of medium (1–10 μm) and micro (0.01–1 μm) pores. As a result, several practical equations for CTB specimens are established, which consider types of tailings and admixtures.

Exploring the link between ultrasonic and strength behavior of cementitious mine backfill by considering pore structure

Understanding the porosity/pore linkage and strength properties of cementitious mine backfill (CMB) is essential for the design of underground mining filling. Adoption of new production techniques in parallel with the development of technology in the mining sector has also increased the orientation to easier and less costly applications for evaluating CMB performance. This study aimed to evaluate the strength development of CMB and the change in its pore structure by using ultrasonic pulse velocity (UPV) technique. The influence of two types of pyritic tailings (low pH and high pH) obtained because of diverse production techniques on the quality of filling specimens was also investigated. The link between the microstructure formation (e.g., MIP), mechanical (e.g., UCS) and ultrasonic (e.g., UPV) characteristics of backfilling was explored by using a fixed ratio of fly ash-slag as a cement substitute (cement/slag-fly ash: 70/30). Filling samples were prepared at constant solid content (74 wt%), different curing times (3–90 days), and binder ratios (3–5-7 wt%). The results revealed that the total porosity of CMBs decreased with increasing age and binder ratio. One could also observe that the total porosity of the fill samples containing high pH tailings was lower (up to 56 %) compared to those containing low pH tailings. The acidic nature of low pH tailings negatively affected the aged strength of CMBs, destructing its microstructure. However, it was observed that the negative effects of low pH added backfills decreased in slag substitution and high binder dosages. Excellent correlation curves (power fitting) were found between UPV and UCS according to the variables used (e.g., different types of processing tailings and mineral additives). The measured and calculated UCS values were largely (R2 = 94.8 %) consistent. Finally, this study provides a complete report to support operationally low cost, easy and feasible fill design for underground metallic mines.

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.

Calibration of the PM4Sand model for hard-rock mine tailings based on laboratory and field testing results

A comprehensive campaign of laboratory and field tests has been conducted to characterize the behaviour of tailings from a hard-rock mine. Cyclic triaxial, direct simple shear, and triaxial simple shear tests have shown that the contractive tailings are susceptible to liquefaction and that their behaviour is similar to loose sand despite their higher fines’ content. To model the behaviour of tailings’ impoundments in dynamic simulations, the PM4Sand constitutive model is calibrated based on the dataset presented here. Some of the model parameters are defined based on consolidation and compression tests, while the critical state line (CSL) is defined based on the results of monotonic triaxial and direct simple shear tests. The CSL is lower for tailings than for most natural sands, which is consistent with previous studies. The calibrated model can reproduce reasonably well the monotonic behaviour and provides an excellent fit of the cyclic strength curves measured in the lab at different confining pressures and density index. The results presented in this paper indicate that the PM4Sand model can be used to simulate the cyclic behaviour of low-plasticity, hard-rock tailings. The proposed procedure also provides general guidelines regarding model calibration for other types of tailings.

Consolidation behavior of various types of slurry tailings co-disposed with waste rock inclusions: a numerical study

The co-disposition of mine tailings and waste rock in tailings storage facilities (TSFs) could contribute to increase the consolidation rate and decrease long-term settlement of tailings. Non-linear change of tailings properties during the filling process and interaction between tailings and waste rock inclusion (WRI) are critical to mechanical analysis but can, however, be complicated to simulate. The question of net volume gains or losses of tailings was also raised. In this study, fully coupled analysis which considered continuous variation of hydraulic conductivity and stiffness of tailings were performed to assess the evolution of consolidation of various tailings types in the presence of WRI. Effects of volume ratio of tailings over WRI on the net volume was investigated. Finally, effect of several practical aspects such as filling rates, and instantaneous filling assumption were considered. Results indicated that WRI could increase by 3.3 times the rate of consolidation of tailings. The zone of influence of WRI on tailings consolidation varied for each tailings. Using updated properties showed significant differences compared to models with constant values. The application of WRI can reduce volume available for the storage of tailings and net volumetric change due to settlement of the tailings with or without WRI could be estimated explicitly. Equations predicting evolution of net volume with the changes in the volume ratio of tailings and WRI were accordingly proposed. WRI effects were more pronounced with the increase of the filling rate. Finally, instantaneous filling assumption had little effect on the simulated rate of consolidation.

Study on Tailings Covering System Constructed by Geological Polymerization of Mine Waste. Part 2: Simulation of Oxidation Inhibition of Overburden on Acid-producing Tailings

Acid mine drainage (AMD) is a well-recognized environmental issue associated with mining production worldwide. The second part of our study aims to assess the protective effect of using a polymer hard layer (PHL) by conducting sulphur-enriched tailing-based column experiments. An oxygen (O2) barrier was simulated using a designed column device filled with different types of tailings. All experimental columns underwent six drying-wetting cycles, and the chemical properties of the tailings and leachate were detected after every cycle. The permeability coefficient of the PHL was only 1.16 × 10- 5cm/s. Over the entire experimental period, none of the leachates collected from column 4 using the PHL as an O2 barrier. Moreover, the level of redox potential and pH and the contents of heavy metals such as Cu and Zn were stable in PHL covering system. These results show that a PHL is the optimal covering system.

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.

Solidification and stabilization of harmful elements in antimony tailings and synergistic utilization of multiple solid wastes

The massive generation and accumulation of tailings potentially lead to environmental pollution. Antimony tailings (AT) have higher environmental risks than other types of tailings and thus require special attention. Hence, this article used a variety of industrial solid wastes to solidify and stabilize the harmful components in AT. The solidified bodies prepared by adding different ratios of AT were cured under standard and natural curing conditions, and a series of performance tests and leaching toxicity analysis were performed. The results show that the solidified bodies containing 1000 g AT demonstrates excellent mechanical properties after standard curing for 28 d, with a compressive strength of 15 MPa and flexural strength of about 2.5 MPa. The solidified bodies have a water absorption rate of around 27%, softening coefficient of about 0.7, dry density of 900 kg/m3 and wet density of 1100 kg/m3, which meet waterproof and lightweight requirements. In addition, according to leaching toxicity analysis, the solidified bodies meet environmental standards. The bonding effect of needle-shaped ettringite and the encapsulation and filling effect of gelling substance are beneficial to the solidification and stabilization of AT. This article provides theoretical basis and research ideas for AT treatment and disposal.

Primary Succession Changes the Composition and Functioning of the Protist Community on Mine Tailings, Especially Phototrophic Protists.

Primary succession in mine tailings is a prerequisite for tailing vegetation. Microorganisms, including bacteria, fungi, and protists, play an important role in this process in the driving force for improving the nutritional status. Compared to bacteria and fungi, protist populations have rarely been investigated regarding their role in mine tailings, especially for those inhabiting tailings associated with primary succession. Protists are the primary consumers of fungi and bacteria, and their predatory actions promote the release of nutrients immobilized in the microbial biomass, as well as the uptake and turnover of nutrients, affecting the functions of the wider ecosystems. In this study, three different types of mine tailings associated with three successional stages (original tailings, biological crusts, and Miscanthus sinensis grasslands) were selected to characterize the protistan community diversity, structure, and function during primary succession. Some members classified as consumers dominated the network of microbial communities in the tailings, especially in the original bare land tailings. The keystone phototrophs of Chlorophyceae and Trebouxiophyceae showed the highest relative abundance in the biological crusts and grassland rhizosphere, respectively. In addition, the co-occurrences between protist and bacterial taxa demonstrated that the proportion of protistan phototrophs gradually increased during primary succession. Further, the metagenomic analysis of protistan metabolic potential showed that abundances of many functional genes associated with photosynthesis increased during the primary succession of tailings. Overall, these results suggest that the primary succession of mine tailings drives the changes observed in the protistan community, and in turn, the protistan phototrophs facilitate the primary succession of tailings. This research offers an initial insight into the changes in biodiversity, structure, and function of the protistan community during ecological succession on tailings.

Geochemical Characteristics of Tailings from Typical Metal Mining Areas in Tibet Autonomous Region

With the exploring and developing of mineral resources in the Tibet Autonomous Region for many years, a large number of tailings have been produced. A total of 17 tailings samples from borehole cores were collected from different tailings ponds in different regions of Tibet. The results showed that the mineral composition and content of tailings in each research area were different. Among them, quartz was the most abundant mineral in most tailings. The major elements of tailings mainly included Si, Al, Fe, Mg, Mn, Ca, Na, K and so on. S existed in different types of tailings. In the analysis of trace element composition, it was found that the content of some elements had approached the lowest industrial grade, which has potential recycling value, such as Mn, Zn, Pb and P. Through the detection of radioactive elements (Ra-226, Th-232 and K-40), it was shown that there were great differences among different types of tailings, and their different contents would bring potential hazards to the safety of the surrounding environment and human health. Similar results were found in the analysis of particle size characteristics of tailings. These results are of great significance for the future utilization and resource utilization of tailings pond.

Physico-chemical and micro-structural behavior of cemented mine backfill: Effect of pH in dam tailings

The tailings created during ore processing have been a serious problem for mining companies and environment since it is a challenging task to effectively manage these highly voluminous/dangerous tailings. Therefore, several tailings disposal methods like tailings dams are needed for sustainable mining operations. The tailings accumulated in the dams reflect a critical raw material source since they might contain key base/precious metals, such as Au, Ag, Co, Ni, Cu and Zn. This study deals with the use-ability of dam tailings in cemented mine/paste backfill (CMB/CPB), considering the physico-chemical and micro-structural aspects. The backfill mixtures were manufactured at 76 wt% solid and 5 wt% cement contents, exposed to cure for up to 56 days, and tested for determining their strength (UCS), geo-chemical (i.e., pH, redox potential, and conductivity) and microstructure (i.e., XRD, TGA, and SEM) characteristics. Results disclosed that the strength of backfill was improved by the augmented basicity/age while only backfills made with sulfide-rich tailings had a noticeable drop in strength. This can be enlightened by the types of tailings (aged and fresh), and the hydration products shaped owing to the interaction of these tailings mixed with cement. While the values of pH detected by chemical tests were amplified up to 14 days, some decreased up to 56 days due to acid formations and erosions. This is the key function of CPB's deterioration physically, chemically, and microstructurally. Lastly, the outcomes of this study will allow us to further explore/assess the effects of dam tailings' potential usages on quality/performance of backfill mixtures.

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.

Physical, Chemical, and Microbiological Characterization of Kettara Mine Tailings, Morocco

The mining industry is of major importance to Morocco’s economy. However, the abandoned pyritic mines are a source of potentially toxic elements that can cause the disruption of the surrounding ecosystems, constituting a huge threat to wellbeing and human health. The present study aimed to analyze the physical and chemical characteristics of different types of tailings and to investigate the microbial populations of acidophilic bacteria involved in the oxidation of pyrite. Coarse and fine tailings collected from different zones of the mine (dike and pond) at two different depths (oxidized and non-oxidized residues) were analyzed for their pH, electrical conductivity, total organic carbon, total nitrogen, available P, major elements, and pseudo-total metal concentrations. The abundance of acidophilic bacteria was determined, and some acidophilic bacterial strains were isolated and tested for their metal tolerance. Tailings showed a pH ≈ 2, very low nutritional content, and high concentrations of Cu, As, Zn, and Pb, which were higher in the non-oxidized samples. The microbial counts of iron- and sulfur-oxidizing bacteria were higher than heterotrophic bacteria, with the highest numbers detected in the oxidized fine tailings. The five acidophilic bacteria isolated from the tailings were affiliated to genera Alicyclobacillus and Sulfobacillus, commonly found in this kind of environment.