Waste Rock Research Articles

Hydrogeochemical modelling of pyrite oxidation ion mobility in unsaturated mine waste rock piles

Hydrogeochemical modelling of pyrite oxidation ion mobility in unsaturated mine waste rock piles

Inhibition of pyrite oxidation through forming biogenic K-jarosite coatings to prevent acid mine drainage production

This study proposes a novel method by forming biogenic K-jarosite coatings on pyrite surfaces driven by Acidithiobacillus ferrooxidans (A. ferrooxidans) to reduce heavy metal release and prevent acid mine drainage (AMD) production. Different thicknesses of K-jarosite coatings (0.7 to 1.1 μm) were able to form on pyrite surfaces in the presence of A. ferrooxidans, which positively correlated with the initial addition of Fe2+ and K+ concentrations. The inhibiting effect of K-jarosite coatings on pyrite oxidation was studied by electrochemical measurements, chemical oxidation tests, and bio-oxidation tests. The experimental results showed that the best passivation performance was achieved when 20 mM Fe2+ and 6.7 mM K+ were initially introduced with a bacterial concentration of 4 × 108 cells·mL−1, reducing chemical and biological oxidation by 70 % and 98 %, respectively (based on the concentration of total iron dissolved into the solution by pyrite oxidation). Similarly, bio-oxidation tests of two mine waste samples also showed sound inhibition effects, which offers a preliminary demonstration of the potential applicability of this method to actual waste rock. This study presents a new perspective on passivating the oxidation of metal sulfide tailings or waste and preventing AMD.

Identifying sources of acid mine drainage and major hydrogeochemical processes in abandoned mine adits (Southeast Shaanxi, China).

Acid mine drainage (AMD) has resulted in significant risks to both human health and the environment of the Han River watershed. In this study, water and sediment samples from typical mine adits were selected to investigate the hydrogeochemical characteristics and assess the environmental impacts of AMD. The interactions between coexisting chemical factors, geochemical processes in the mine adit, and the causes of AMD formation are discussed based on statistical analysis, mineralogical analysis, and geochemical modeling. The results showed that the hydrochemical types of AMD consisted of SO4-Ca-Mg, SO4-Ca, and SO4-Mg, with low pH and extremely high concentrations of Fe and SO42-. The release behaviors of most heavy metals are controlled by the oxidation of sulfide minerals (mainly pyrite) and the dissolution/precipitation of secondary minerals. Along the AMD pathway in the adit, the species of Fe-hydroxy secondary minerals tend to initially increase and later decrease. The inverse model results indicated that (1) oxidative dissolution of sulfide minerals, (2) interconversion of Fe-hydroxy secondary minerals, (3) precipitation of gypsum, and (4) neutralization by calcite are the main geochemical reactions in the adit, and chlorite might be the major neutralizing mineral of AMD with calcite. Furthermore, there were two sources of AMD in abandoned mine adits: oxidation of pyrite within the adits and infiltration of AMD from the overlying waste rock dumps. The findings can provide deeper insight into hydrogeochemical processes and the formation of AMD contamination produced in abandoned mine adits under similar mining and hydrogeological conditions.

Microstructural characterization and the influence of the chemical composition of the raw material mix on the physicochemical characteristics of waste-derived ceramic aggregates

This work presents the possibility of using a mixture of different mining and industrial wastes (fly ash, waste rock, glass cullet and waste solution as a binder) for ceramic aggregate production with the application of microwave radiation. The effect of the chemical composition of the raw material mix reflected by F/SA ratio (flux oxides/SiO2 + Al2O3) on the mechanical and microstructural properties of the aggregates was evaluated using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and X-ray nanotomography (nCT). A higher proportion of fly ash relative to waste rock in the mixture composition led to an increase in the F/SA ratio. The greater the F/SA, the higher the values of particle density and compressive strength, ranging from 1.72 to 1.87 g/cm3 and 6.31–7.31 MPa, respectively. Moreover, higher F/SA led to lower water absorption and porosity, which oscillated between 2.12 - 3.44% and 3.22–5.00%, respectively. X-ray nanotomography studies revealed an increasing contribution of larger pores with a radius of and an overall increase in porosity as the F/SA ratio rose. This finding was further confirmed by SEM investigations. TG-QMS analysis showed that organic matter could act as a pore-forming agent. The basic physical and mechanical paramaters of the obtained ceramic aggregates indicate the suitability of the studied wastes for the production of valuable construction materials.

Strength distribution of cemented waste rock backfill: a similarity simulation experiment

Backfill of cemented waste rock into underground mined-out areas is an effective way to eliminate solid wastes and potential hazards in mines. To understand the backfill strength distribution law throughout the stope, similarity simulation experiments were conducted for direct-irrigating cemented waste rock backfill, and OpenCV and neural network were employed to analyze particle segregation and the spatial distribution of backfill strength. Results show that distinct gravitational segregation leads to an uneven and heterogeneous distribution of natural graded waste rocks in a similar model. Backfill strength near sidewalls and bottom of the model surpasses that of other areas. In the vertical direction, the average backfill strength increases with depth, ranging from 1.15 MPa at the topmost layer to 1.91 MPa at the bottommost layer. Horizontally, the average backfill strength near model boundaries is consistently higher than that at the model center, irrespective of the layer depth and orientation. Neural network prediction on spatial backfill strength proves reliable, exhibiting an average relative error of 4.12%, compared to the traditional surface fitting with a 10.20% error. Verification tests affirm the capability of the neural network model to accurately predict the anisotropic and nonlinear distribution of backfill strength in a large stope.

Needs and Options for Improving Gold Mining Waste Management Practices for Sustainable Development in Tanzania

The main objective of this study was to evaluate current mining waste management practices and their challenges. This study aimed to identify existing technologies and practices, and to present improvement needs and options for environmentally sustainable practices for mining operations. Other researchers have reported many practices and technologies for managing mining waste, but the efficiency, applicability, and need for customization were not specifically addressed for developing countries. This study used field observations, measurement methods, and laboratory analysis to collect data. This study showed a large amount of mine waste rock compared to the tailings wastewater from gold processing plant produced annually. This comprises approximately 5.2 million m3 of mine contaminated water generated by leaching from the waste rock dump (WRD) and 2.3 million m3 from the tailings storage facility (TSF). The study also identified the use of TSF cut-off trenches for seepage collection, the use of lime to treat acid mine drainage (AMD), the discharge of AMD into the TSF, and the recycling of TSF water as the best practices for managing mining waste. Furthermore, the study also found that the most common environmental problems were caused by TSF water and AMD water. However, mining waste management can be improved by modifying existing practices and adopting cost-effective technologies and practices to control and treat excess mining water.

Effective Stress Analyses to Assess the Stability of Progressively Raised Upstream Dikes for Tailings Impoundments with Waste Rock Inclusions

Effective Stress Analyses to Assess the Stability of Progressively Raised Upstream Dikes for Tailings Impoundments with Waste Rock Inclusions

Complex electrical measurements of waste rock during acid mine drainage generation and release: Kinetic column tests

Acid mine drainage (AMD) emanating from waste rock piles (WRPs) at mining sites is a global concern. Successful rehabilitation of these sites requires effective characterization and monitoring of the waste rock during AMD generation/release. Traditional approaches involve ex-situ analysis of waste rock and porewater samples collected via corings and monitoring wells; however, this is highly disruptive, costly, and provides sparsely distributed point information across enormous volumes typical of WRPs. Geoelectrical techniques are a promising approach for non-invasive continuous imaging; however, their application has been limited to ‘one-off’ imaging with few studies on monitoring waste rock evolution. The objective of this study is to assess the geoelectrical signatures of changing waste rock during AMD generation/release. Field waste rock samples were extracted from three mine WRPs and first characterized for mineralogy and acid generation potential. Kinetic tests were then performed on each sample using leaching columns and humidity cells, with simultaneous measurements of effluent quality and complex electrical conductivity (real and imaginary components measure conduction and polarization, respectively). Results show that real conductivity was highly sensitive to changes associated with AMD leachate quality (e.g., 28,800 to 68 mg/L acidity) and surface of the waste material. Imaginary conductivity measurements identified changes in the waste mineralogy over time, though these signatures were not very distinct, which is likely due to low sulfide contents and limited oxidation (e.g., 0.59 wt% sulfide and 33% air saturation). This study improves our understanding of geoelectrical signatures associated with real waste rock, demonstrating the potential application of the electrical resistivity tomography and induced polarization techniques for mine waste investigations.

Effective utilization of dolomitic lead–zinc waste rock by replacing dolomite as flux in iron ore sintering process

Effective utilization of dolomitic lead–zinc waste rock by replacing dolomite as flux in iron ore sintering process

MIGRATION OF HEAVY METALS FROM MINE WASTE ROCK DUMP END ENVIRONMENTAL IMPACT ON GROUNDWATERS AND SEDIMENTS

The environmental impact of mine waste rock dump, located in the region of Srednogorie, Bulgaria on groundwaters and sediments was studied. The acid mine drainage with low pH (2.43 - 3.53), high electrical conductivity (1500 - 4400 μS cm-1), content of Fe, Mn, Cu, Zn, Al, As and high concentration of sulfates (540 - 6905 mg L-1) are formed after heavy rainfall. The content of heavy metals, except manganese, in groundwater was significantly lower than that in the acid mine drainage, and the pH was in the range of 5.43 to 6.62. Sediments in the non-consequential vicinity of the mine waste rock dump had a pH in the range of 2.86 - 4.53 and contained heavy metals and As at concentrations higher than those in the mineral waste due to precipitation, co-precipitation and sorption reactions. An increase in the copper and zinc content in the exchangeable and organic matter fractions was found in the sediment sample. A relationship was found between arsenic and iron concentration in the sediments, which was mainly due to the retention of arsenic in the Fe and Mn oxides fraction. The concentration of total Mn in the sediments was lower than that in the mining waste due to the high mobility of manganese.

Prediction Study on the Impact of Engineering Waste Rocks on Water Quality During Reservoir Construction

The impact of dammed reservoirs on the local ecological environment during the operational phases has garnered significant attention. However, there is limited research on the ecological risks posed by reservoirs during the construction period, particularly regarding the waste rock at the bottom of the reservoir. Based on the results of release experiment, the water quality risks of engineering waste rocks to reservoirs were analyzed by a three-dimensional model using the MIKE 3 FM HD and ECO Lab module. The calculation results showed that as the waste rock yards are inundated, SO42− and Fe3+ in the reservoir are released and gradually affecting the water quality in the area in front of the dam. During the process of water storage, the release of pollutants from the waste rocks at the bottom of the reservoir had a significant impact on the underlying water body after two months and then spread from the bottom to the upper layer of water. After three months of water storage, when the water level of the reservoir reached 867 meters, the pollutants released by the waste rock had an impact on the surface water quality. After four months, the release of pollutants from the waste rock yards essentially ceased, and the pollutants gradually accumulated in the bottom water body in front of the dam after dilution and diffusion. In the future, special attention should still be given to the risk assessment of pollutants in the bottom sediments during long-term operation and management of the reservoir.

Modern technical and IT solutions in the System of Quality Control of the Run of Mine at LW “Bogdanka” S.A. coal mine

In underground coal mines, one of the primary sources of waste rock in the ore is the phenomenon of roof fall. This phenomenon increases the contamination of the ROM (Run of Mine) with waste rock, which in turn increases the operating costs of the mine. Exploitation of thinner and thinner seams, the use of plough technology, the increasing speed of mining – all these factors related to the mining technology used significantly affect the cleanliness of the coal seam exploitation. More accurate identification of the causes of increased spoil contamination by waste rock and forecasting its level at the stage of mining planning can allow the application of appropriate countermeasures, often even before the start of mining. The authors believe that monitoring the amount and sources of waste rock in longwalls and headings can provide a basis for developing a method for forecasting the mining plant’s yield. The article presents methods of modeling roof rock fall, which are the result of the work of the Team of the Division of Mineral Resources Acquisition of the Polish Academy of Sciences and LW “Bogdanka” S.A. In the future the proposed methodology can be used to analyze the course of roof rock fall, calculate the mass of roof rock fall, and calibrate a continuous system for measuring the quality of ROM in mine excavations.

Tools to improve mine closure: 10 years of research in integration of environment in the mine life cycle

Abstract Mine closure can be approached by several points of view, from the technical, engineering, ecological, up to social and governance aspects. The definition of a good mine closure should cover most, if not all, of these aspects. This article provides a review of technical and engineering-oriented research work as a partial answer to the question ‘what is good mine closure’. The article presents a ten-year research program realized in the framework of a Canada Research Chair in integration of environment in the mine life cycle. Research projects aimed at better planning mine closure and mine site reclamation from the early stages of a mining project life cycle are exposed as possible steps to strive for optimal mine waste management. At the exploration stage, geo-environmental characterization and modeling are proposed as tools to improve mine waste management planification. During mine operations, environmental desulfurization is suggested as a method to reduce environmental risks associated with sulfidic tailings and waste rock. Indeed, research has shown that acid mine drainage and metal leaching can be significantly limited via desulfurization. At the closure stage, desulfurized tailings can be used to replace at least part of natural materials used for reclamation cover systems. Research work done on other types of mine waste, such as waste rock and water treatment sludge, also show good potential for their reuse as closure material. All these tools can be integrated into the mine life cycle to better plan for closure, which ultimately will make mine closure more sustainable.

Reduction of ore losses on the footwall by improving ore breaking

When mining steep deposits of Kryvyi Rih iron ore basin (Ukraine), a significant part of the reserves is lost in the “triangle” of the footwall. Complete extraction of reserves requires increased costs for mining ore. At present, there are options for mining reserves from the “triangle” of the footwall. However, all the proposed options lead to an increase in the cost of mining or increased ore losses and the reduced iron content in the mined ore mass. To reduce the cost of mining, an option is proposed with concentrated charges to break ore located between the footwall and the caved massif. In order to improve indicators of reserve extraction from the “triangle” of the footwall in the massif, it is advisable to place inclined concentrated charges at an angle of 58 – 78 degrees. To reduce broken ore dilution with waste rocks on the boundary, it is advisable to create an overcompacted layer of the broken ore mass by reducing the calculated value of the line of least resistance by a factor of 0.5 – 0.75. Application of this method of mining reserves from the block increases the content of iron in the mined ore mass by 1.2%, reduces discounted costs for driving workings and for drilling and blasting. Thus, due to application of the bulk level caving system with improved ore breaking by the use of concentrated charges located in the “triangle” of the footwall, the expected economic effect of mining of 718.2 kt makes 5.20 k USD.

The application of artificial neural network model to predicting the acid mine drainage from long-term lab scale kinetic test

Acid mine drainage (AMD) is one of the common environmental problems in the coal mining industry that was formed by the oxidation of sulfide minerals in the overburden or waste rock. The prediction of acid generation through AMD is important to do in overburden management and planning the post-mining land use. One of the methods used to predict AMD is a lab-scale kinetic test to determine the rate of acid formation over time using representative samples in the field. However, this test requires a long-time procedure and large amount of chemical reagents lead to inefficient cost. On the other hand, there is potential for machine learning to learn the pattern behind the lab-scale kinetic test data. This study describes an approach to use artificial neural network (ANN) modeling to predict the result from lab-scale kinetic tests. Various ANN model is used based on 83 weeks experiments of lab-scale kinetic tests with 100% potential acid-forming rock. The model approaches the monitoring of pH, ORP, conductivity, TDS, sulfate, and heavy metals (Fe and Mn). The overall Nash-Sutcliffe Efficiency (NSE) obtained in this study was 0.99 on training and validation data, indicating a strong correlation and accurate prediction compared to the actual lab-scale kinetic tests data. This show the ANN ability to learn patterns, trends, and seasonality from past data for accurate forecasting, thereby highlighting its significant contribution to solving AMD problems. This research is also expected to establish the foundation for a new approach to predict AMD, with time efficient, accurate, and cost-effectiveness in future applications.

Indium use, resource, market and ore deposit type

With the continuous advancement of science and technology, rare dispersed elements that have long been dormant in rocks and ignored by humans have become increasingly important. Indium is one of these rare dispersed elements, although most people know little or nothing about it. In fact, indium has a wide range of important uses in many aspects. Given the unique physical and chemical properties of indium, some uses are even irreplaceable. Therefore, many countries have included some rare elements, including indium, in the list of national strategic resources or critical metals for protection. This article not only popularizes the main uses of indium in modern society, briefly describes the distribution and current status of natural indium ore resources around the world, but also explores its market status in the past 10 years and future development trends. Finally, the main genesis types of associated or symbiotic indium ores around the world are summarized and briefly discussed. Because indium does not exist as an independent deposit and can only exist as a by-product of non-ferrous metals such as copper, lead, zinc and tin, it is very important to research and develop new sources of indium, including recycling and reuse. These new sources include but are not limited to waste rock piles and tailings from related abandoned old mines, etc.

Enhancing Orebody Knowledge using Measure-While-Drilling Data: A Machine Learning Approach

Due to limited resource definition and grade control drilling, conventional bench-scale geochemical exploration is frequently plagued by uncertainty, resulting in diminished processing plant efficiencies. The Measure-While-Drilling (MWD) system comprises a set of sensors designed to gather data pertaining to the performance of mining blast hole drill rigs. Previous MWD research primarily relied on penetration rate to identify rock type and estimate grade. This investigation uses Data Fusion and Machine Learning (ML) algorithms to characterize geochemical orebody quality values, such as iron percentage, phosphorous, sulfur, alumina, and silica content, based on MWD data collected at the field-scale, thereby facilitating efficient mine planning and excavation. Feature importance algorithms identified novel significant MWD variables, such as force on bit and ratio of bit air pressure to penetration rate, which provide valuable insights into subsurface geochemical properties. The performance of various ML algorithms was compared, with the Random Forest algorithm demonstrating the highest coefficients of determination (up to 0.96), indicating accurate field or laboratory results prediction. As a result, this work demonstrates that MWD data can be used to obtain high-resolution orebody knowledge prior to mining, improving subsurface geochemistry prediction. This knowledge can optimize the excavation of high-grade material by minimizing dilution from lower-grade or waste rock entering the processing plant.

Geotechnical investigations of lead-silver ore processing residues at the Auzelles site, Auvergne (France)

<p>Mining operations generate a significant quantity of mining waste in the form of sterile rocks and processing residues. These mining wastes are typically placed on the surface and can cause geotechnical and geochemical disturbances, as well as contaminants in surface water (through runoff) and groundwater (through infiltration), thus posing environmental risks. This article aimed to characterize the geotechnical properties of lead-silver ore processing residues at the Auzelles site in order to assess their stability and propose recommendations for their management and rehabilitation. The adopted methodology included in situ tests (such as density measurement and permeability) and laboratory analyses (grain size distribution, moisture content, methylene blue test, direct shear test, and standard Proctor test). The results showed a wet density of 1.63 g/cm<sup>3</sup> for the residues compared with 1.65 g/cm<sup>3</sup> for the waste rock, as well as a permeability of the residues measured at 5.5 × 10<sup>-5</sup> m/s, indicating significant drainage capacity. Laboratory analyses revealed that the samples were primarily composed of very silty sands and gravel, classified as B5 according to the Guide to Road Settlements. The cohesion of the residues was found to be zero, while the internal friction angle varied between 28° for the residues and 30° for the foundation soils. These geomechanical properties, particularly density, lack of cohesion, and friction angle values, raise concerns about the long-term stability of the residues. Due to their high permeability and lack of cohesion, the residues are susceptible to mass movement and erosion, which may exacerbate contamination risks. Therefore, it is essential to integrate these parameters into any potential residue stability analysis. Proactive management, based on these results, requires the implementation of appropriate rehabilitation techniques, such as drainage optimization and incorporation of vegetation covers, to minimize environmental impacts and ensure the long-term sustainability of mining waste structures.</p>

Potential Use of Coal Mine Overburden Waste Rock as Sustainable Geomaterial: Review of Properties and Research Challenges

Potential Use of Coal Mine Overburden Waste Rock as Sustainable Geomaterial: Review of Properties and Research Challenges

Improvement of the transitional technology from open pit to underground mining of magnetite quartzite

The paper analyzes the disadvantages of the technology of iron ore open pit mining and current environmental problems of open pit mining. The paper also addresses problems of possible displacement and strains of rocks in the classical open pit mining method with extraction of minerals exclusively by open pit mining, studies current transitional technologies from open pit to integrated open pit-underground and subsequent underground mining, and presents an improved methodology for studying the stress-strain state of the massif during transition from open pit mining to integrated open pit-underground and subsequent underground mining. There are studied, developed and proposed options of environmentally friendly technologies of integrated open pit-underground mining with mining waste disposal in the worked-out space of underground mines and open pits, highly efficient calculation schemes for studying the stress-strain state of a rock massif during transition from open pit to underground mining with formation of protective barrier pillars, an option with the development of the lower room of stage II under protection of an ore pillar left within the contours of the upper room of stage I, and an option with the development of the lower room of stage II under protection of an artificial pillar made of the consolidating backfill in the upper room of stage I. The stress-strain state of the massif and possibilities of forming internal waste rock dumps when applying integrated open pit-underground mining technologies are studied and substantiated. Transition technologies from open pit to underground mining of iron ore raw materials under the bottom of an operating open pit are developed and proposed on the example of Kryvyi Rih iron ore basin.