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By E. Kalhan, C. Kincal

One of the biggest problems in open pit mining is slope stability. The avoidance of slope stability problems depends on a comprehensive assessment of environmental and operational factors such as geology, climate, and mining activities. In the light of these considerations, slope geometries should be determined in accordance with engineering principles. In this research, the slope stability of rock slopes in a mine opened in a gneiss geological unit has been studied. Production activities were ceased in 2019 due to the slope movements in the eastern part of the quarry. In order to safely continue the production, field works were primarily carried out. To assess slope stability, detailed discontinuity surveys were carried out on bench faces. Subsequently, kinematic and numerical analyses were employed to identify geometries that are expected to maintain stability under the prevailing geological structures and environmental constraints. Engineering geological studies such as scanline measurements in steps and investigation of potential failure mechanisms by kinematic analysis technique were carried out. Small module reactor and Q-slope rock mass classification systems were used to evaluate slope stability. Based on these classification systems potential unstable rock slopes were identified and thematic maps were created using geographic information systems. The most suitable slope geometries are suggested for these slopes. In addition, the improvement methods suggested by the rock mass classification systems were proposed for these slopes.

Sep 1, 2025

By L. von Ketelhodt

During the period October 2003 to June 2004, a containerized optical sorting pilot plant was operated at Kloof Gold Mine on a waste rock dump. In this paper, we describe the test work and its results leading to the decision to operate this pilot plant. This paper presents the operational data and financial figures achieved during this project, in particular, for the month of June 2004 when the plant was run at full capacity on three shifts, 24 hour operation. These results are also extrapolated and presented to show the profitability of such an operation at today?s gold price levels and cost structure.

Jan 1, 2009

By Y. Zhou, G. Chisakuta, P. Bwando, G. Mitshabu

A newly started copper hydrometallurgical plant was confronted with a manganese oxidation issue in electrowinning. This oxidation, in the absence of the amount of iron required to stabilise the electrolyte oxidation-reduction potential, is known to produce oxidants (MnO2, MnO4) that can cause accelerated degradation of the organic phase components in solvent extraction and corrosion of lead anodes in electrowinning. The overpotential required to build up the protection layer on new anodes causes an increased electrolyte potential that creates oxidized species in the electrowinning tankhouse, and these species come back to solventextraction plant with the recycled spent electrolyte. This paper discusses the impacts of manganese oxidants on the health of a plant organic phase. It also outlines the actions taken using iron scraps and sulfur dioxide to mitigate the problem that happened due to the lack of ferrous iron sulfate available on site, as recommended for better control.

Jan 1, 2023

By M. M. Oosterveld

"In South West Africa diamonds are mined from ancient beach deposits by the Consolidated Diamond Mines of South West Africa, Limited.To improve the control of mining production, a computer is used for the calculation of statistically more accurate and homogeneous ore blocks. Geological and sampling information has been digitized and stored on magnetic files.The figures derived for each block entail the calculation of the diamond size frequency distribution, the diamond density distribution and the ore reserve by using the density distribution.The diamond size frequency distribution is used for estimating the revenue in an ore block.A description is given of how a linear programming system can be used for production planning."

Jan 1, 2014

By M. Wrobel, J. Hammerschmidt, M. Runkel

Fluid-bed technology is a key pyrometallurgical step for processing a vast number of ores and concentrates. Over the past 50 years, considerable research and development efforts have been made by Metso Outotec to expand the application window of this technology. This paper illustrates different processing routes where fluid-bed technology plays an important role in the production of the copper. The fluid-bed processes utilized are partial, sulfate-producing, and dead roasting. The focus of this paper considers the advantages of the dead-roasting process. This “zero waste” process can provide copper oxides, steam, electrical power, and sulfuric acid for new and existing solvent extraction–electrowinning plants. In a case where an operation is running out of oxidic ores and concentrates, fluid-bed roasting can be applied to close this gap and provide the required copper oxides in a sustainable way.

Jan 1, 2023

By B. A. Obadele, R. Machaka, M. L. Raganya, M. E. Makhatha, N. A. Moshokoa

The influence of solution treatment on the phase evolution and tensile properties of Ti-Mo alloys was investigated to assess their potential use in biomedical applications. Phase formation and microstructural evolution were studied using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The mechanical properties were characterized by means of tensile tests and bending strength. XRD analysis showed that solution treatment increased the volume fraction of β phase and supressed the α" phase. The microstructures of the as-cast alloys consisted of β equiaxed grains with sub-grain structures of different sizes, while the solution treated alloys comprised β equiaxed grains only except for Ti- 10.02Mo, which comprised needle-like α" structures. EBSD showed an increase in the volume fraction of the ω and α" phases in all the alloys after solution treatment. The elastic modulus and UTS of all the alloy significantly decreased after solution treatment, except for Ti-15.05Mo,whereas the elongation significantly increased. The fracture surfaces of all the alloys after solution treatment indicated more ductile behaviour than brittle

Jun 10, 2024

By R. M. Mashishi, T. Malehase, O. J. Okonkwo

The concentrations of selected trace elements (As, Cd, Hg, and Pb in run-of-mine (ROM) coal, discard, and coal product were investigated to assess the efficiency of beneficiation in reducing trace element concentrations and ascertain any implications regarding environmental compliance to regulatory frameworks. Samples were collected from a colliery in Mpumalanga Province twice a month for a period of 24 months. The samples were ashed to approximately 0.21 mm, then digested in a mixture of 70% HNO3 and 40% HF and analysed using inductively coupled plasma-mass spectrometry (ICP-MS). Except for Pb, the mean concentration of all elements decreased from the ROM stage to the coal product stage. The order in which trace elements occurred from the highest to lowest throughout the production chain was Pb>As>Hg>Cd. With the exception of Cd, the mean trace element concentrations in the discard were above the total concentration threshold (TCT) set for landfill disposal. The As, Hg, and Cd concentrations in the product were well below the thresholds for all land uses. However, Pb concentrations in the product coal were above legal limits, which is of concern with regard to environmental compliance and the performance and marketability of the product.

Dec 13, 2023

By S. T. L. Harrison, J. R. Amaral Filho, M. Smart, J. Broadhurst, J. Weiler

Technosol production from mine waste, following amendment with additional organic residues, to provide healthy and functional topsoil is an advantageous alternative to the long-term dump disposal of mine waste. Minimising the legacy of mine waste and supplying soil for mine site rehabilitation contributes towards more sustainable mining practices. Following the creation of the physicochemical structure of the soil from appropriate mixtures of coal waste with low sulfur content, physical ameliorants and nutrient sources, the inoculation of Technosols with active microbial suspensions may accelerate the decomposition of organic matter present and ensure nutrient availability for plant growth through active nutrient cycling, particularly of nitrogen, sulfur and phosphorous. In this paper, South African ultrafine coal waste was used as the main mineral matrix, and malt residue was used as source of organic matter and nutrients. In order to evaluate the effects of Technosol inoculation, five microbial treatments were used, including the addition of: commercial grade efficient microorganisms (EM Prosoil), anaerobic digested sludge supernatant from treating brewery waste, and ‘tea’ extracts prepared from compost, vermicompost and soil native to the mining area. Growth experiments were carried out using Eragrostis teff, commonly known as teff, a grass typically used for the rehabilitation of mined areas in South Africa. Preliminary results showed that Technosols inoculated with microorganisms performed better in terms of nutrient availability and plant growth. Varied performance was observed as a function of the microbial inoculation applied. This suggests that the inoculation of Technosols with appropriate microorganisms may be recommended to accelerate nutrient availability assisting plant growth during the initial establishing of the Technosols. Technosols continue to show promise as an alternative to both mine waste disposal and the burrowing of topsoils for mine rehabilitation. Keywords: Fabricated soil, mine waste, coal discards, malt residue, nutrient availability, soil microbiology, plant growth

Jan 1, 2020

By T. Marin, J. E. Seccatore, M. Cardu

The most energy-intensive process in the mining industry is particle size reduction – comminution. The first phase of this process is blasting to fragment the rock from the initial Boussinesq’s halfspace size. Scientific literature demonstrates that the output of a blast in terms of fragment size distribution can be manipulated by varying the specific charge (powder factor) and charge distribution. This study focuses on the influence of blasting on the internal resistance of the blasted fragments; in particular the influence of the spatial distribution of charges. Small-scale blasts were performed on 14 marble blocks using different powder factors and charge distributions. Three control blocks were fragmented by mechanical means for comparison. The results show the correlations between charge distributions and the specific energy of mechanical comminution. Opportunities for adjusting charge diameter and distribution in opencast blasts to improve the performancet of comminution circuits are discussed.

Aug 8, 2024

By A. F. van der Merwe, R-D. Taylor, M. Jacobs, F. H. Conradie

Total bound moisture (TBM) is a typical quality indicator of industrial-grade gypsum. This gypsum is comprised of three distinct phases, namely anhydrite, dihydrate, and hemihydrate, of which only the latter is of much industrial use. TBM analysis is a lengthy laboratory procedure, and an artificial neural network (ANN) TBM inference measurement is proposed as a fast and online alternative. An ANN inference model for gypsum TBM based on plant data was developed. The inputs to the network were primarily focused on the plant's calciner, and different network topologies, data divisions, and transfer functions were investigated. Furthermore, the applicability of the TBM value as a quality indicator was investigated based on a gypsum phase analysis. A strong correlation between TBM and the gypsum hemihydrate and anhydrite content was found, validating the plant target TBM of 5.8% as a quality indicator. A network topology consisting of one hidden layer with logarithmic-sigmoid (logsig) and pure linear (purelin) transfer functions showed the best performance (R > 90%).

Oct 3, 2023

By S. A. Lorentz, Y. Xu, C. Theron

The failure of tailings storage facilities (TSFs) results in the discharge of significant quantities of hazardous waste material into the natural environment. Research studies relating to slope instability have identified physical mechanisms such as rainfall-induced erosion, liquefaction, and shear failure as the main triggers. The generation of transient pressure waves and the mobilization of pre-event water in the unsaturated zone have been found to trigger shallow landslides in natural hillslopes. In this paper we review these physical mechanisms, known as groundwater ridging (GWR) and the Lisse effect (LE), from other studies. Previous researchers have explained both these phenomena through field and laboratory observations, numerical modelling, as well as conceptual discussions. These case studies demonstrate the impact of rainfall characteristics on the generation of transient pressure waves that rapidly increase the phreatic surface and change pore water suction. Reference is also made to the influence and behaviour of physical porous medium characteristics on the establishment of a continuous water phase that facilitates the transmission of an induced pressure head. However, previous studies fail to recognize the possibility that the pressure increase in pre-event water through pore air propagation could cause slope instability in tailings dams. The authors suggest that the physical properties and hydraulic behaviour of unsaturated porous tailings media make it susceptible to GWR and the LE, resulting in the creation of a potential failure plane.

Feb 2, 2022

By J Taguta, B. McFadzean, P. E. Ngoepe, M. G. Mulaudzi

Computational modelling methods and isothermal titration calorimetry (ITC) were employed to investigate the interaction of a pyrite surface with thiol collectors. Modelling work was conducted in the presence and absence of water. Microcalorimetry was employed to investigate the resultant energy of interaction pyrite as a result of mineral-collector interactions. Sodium ethyl xanthate (SEX), diethyldithiocarbamate (DTC) and diethyl dithiophosphate (DTP) were investigated in this study. The results showed that the calculated surface energies and morphologies for FeS2 showed that (100) and (111) are the most stable surfaces. The morphology also indicated the appearance of the (100) and (111) surface facets and no presence of others. The calculated adsorption energies between thiol collectors and the pyrite surface were always more exothermic than the experimentally determined ones. When comparing different ligand types with the same alkyl chain length, the heat of adsorption of diethyl-DTC was greater than that of ethyl xanthate and diethyl-DTP for pyrite. Experimentally, the diethyl DTP barely adsorbed onto the pyrite surface and this may be due to a different mechanism of action. In computational calculations, water adsorption was found to reduce the reactivity of the Fe atom for the interaction with thiol collectors, and bring the adsorption energies closer to the magnitude of the experimental values. Keywords: Computational modelling, microcalorimetry, experimental and thiol collectors, adsorption energies

Jan 1, 2020

By J. Moema, L. Mampuru, M. Phasha, D. Mkhonto

The global liquified natural gas (LNG) storage market size is projected to reach USD17.5 billion by 2025. Currently, owed to its high toughness, tensile strength, and excellent weldability, the 9% nickel steel is the most used in building infrastructure for cryogenic applications such as the construction of tanks and pipes for storage and transportation of LNG. However, this alloy is not readily available because of its complex production process and high cost. This provides an opportunity for suitable alternative materials to build infrastructure for cryogenic applications. Among strong contenders is the Fe-Mn based alloys, which have sparked global interest due to their desirable properties such as relatively lower density, low cost, high toughness and strength, due to a high manganese (Mn) content. These attractive properties render Fe-Mn based alloys preferred candidates to replace traditional steels in engineering applications in which strengthweight ratio is critical. In response, as a build-up to designing and developing austenitic Fe- Mn alloys, the present study employed density functional theory (DFT) based first-principles computational materials modelling technique to investigate the structural, thermodynamic, and magnetic properties of binary Fe-Mn alloy composition in competing FCC, HCP, and BCC crystal structures. Using this approach, it was possible to unravel the key underlying elastic properties that are directly correlated to experimental tensile strength and high toughness in binary Fe-Mn alloys. Besides successfully validating the existing experimental data, the current predicted properties and the deployed approach will serve as a benchmark from which further alloying required to improve other properties will be conducted.

Mar 4, 2025

By S. T. L. Harrison, A. Kotsiopoulos, M. D. Maluleke, E. Govender-Opitz

In the extraction of base metals from printed circuit boards (PCBs) using bioleaching, the accumulation of metal ion stress in solution has been shown to inhibit the microbial regeneration of ferric iron. This poses a challenge for the development of this technology for e-waste treatment. The paper explores the application of a microbial immobilisation system in a two-stage bioleaching system consisting of a chemical leaching reactor in series with a microbial ferric iron regenerating reactor to mitigate microbial inhibition and to enhance base metal extraction. A mixed microbial culture dominated by L. ferriphilum, L. ferrooxidans and At. Caldus was maintained over a period of two months in the presence of polyurethane foam which acted as the biomass support particle. Microbial metabolic activity of immobilised cells and their tolerance to inhibitory Cu ions was investigated. Results showed that immobilised microbial cells maintained higher ferrous iron oxidation activity compared to planktonic cells in the presence of increasing Cu2+ concentrations up to 6 g/L. This presents an opportunity for microbial immobilised systems to be adopted in two-stage bioleaching system. Keywords: Bioleaching, microbial immobilisation systems, microbial inhibition and ferrous iron oxidation

Jan 1, 2020

By N. C. J. Dempers, J. A. L. Parker, R. A. Wildenboer

More than half of global cobalt reserves are located in the Southern African Copperbelt, stretching over the northern tip of Zambia and southern area of the Democratic Republic of Congo. In these areas, cobalt is not typically produced as a primary product but as a byproduct of copper production. Ores from this region often contain uranium, which is readily leached under typical copper leach conditions and enters the process. Uranium does not pose a challenge to copper production, but it becomes a significant problem when it follows cobalt to the cobalt precipitation process and results in unacceptably high levels of U in the final Co product. This paper evaluates the existing process technologies that can be used to remove uranium from cobalt-bearing process streams, including phosphate precipitation and ion exchange. Advantages and disadvantages of the uranium removal processes are discussed, and important design considerations are highlighted.

Jan 1, 2023

By K. Sasaki, S. Kuroiwa, H. Miki, Y. Aoki, T. Hirajima, Y. Orii, G. P. W. Suyantara

Selective flotation to separate copper minerals from, for example, Mo- and/or As-bearing minerals is a continuing problem because the selectivity of current systems is imperfect. Selective Cu-As flotation is currently difficult, and the most common Cu-Mo selective flotation method uses NaHS; this must be done in an enclosed system because, under acidic conditions, this method produces hydrogen sulfide. In this paper, some novel alternative flotation processes that use redox reactions are discussed; these methods have a much lower environmental impact. Oxidation and reduction reactions can be used to make copper minerals more hydrophilic and Mo-bearing minerals more hydrophobic. X-ray photoelectron spectroscopy (XPS) analyses indicated that the copper minerals became hydrophilic because hydrophilic iron precipitated and several hydroxides covered the copper minerals’ surfaces, whereas the molybdenum minerals remained hydrophobic because their sulfide surfaces were not covered. Flotation experiments on these minerals after redox treatments indicated that excellent separation of Cu-minerals from Mo-minerals can be achieved. Possible mechanisms for this separation were investigated using detailed surface analyses and thermodynamic calculations. The additives used to initiate the redox reactions are easy to handle and make these new flotation procedures better than current processes because the new methods do not emit effluent gas and because they are commercially viable. Keywords: Flotation; chalcopyrite; molybdenite; oxidation; reduction

Jan 1, 2020

By G. Bueno, L. M. Tavares, T. M. Campos

Iron ore pellet feed pressing has been one of the first and most successful applications of High- Pressure Grinding Rolls (HPGR) in the minerals industry. Vale S.A. has been one of the pioneers in this application, currently with six HPGRs in operation in the pelletising plants of the Complexo de Tubarão (Brazil). In spite of the important advances in the technology, risks still exist when scaling-up the process from small-scale information. The present work takes advantage of the recent advances in the mathematical modelling of the HPGR performance, using the population balance model to evaluate the modified Torres and Casali model prediction in iron ore pellet feed pressing for different scales of operation. Results are presented that compare the HPGR performance in different operational scales for iron ore pellet feed pressing, demonstrating the confidence of this model-based approach for scale-up to full-scale HPGRs used in pressing iron ore concentrates. Keywords: Scale-up, HPGR, pellet feed, modelling, simulation

Jan 1, 2020

By C. Chibwe, M. Tadie

Copper electrowinning models are useful for prediction of process performance, optimisation and improved understanding of complex phenomena such as current distribution without the expense of physical experiments. Recently, finite element models such as those generated in COMSOL Multiphysics have been developed for the electrowinning process. The predictive capacity of these models is improved by incorporating physical and chemical phenomena. Since physicochemical properties of electrolytes can have a significant effect on the quality of copper produced, this work was conducted to investigate the effect of such properties on electrodeposition at varying levels of copper, sulphuric acid concentration, iron concentration and temperature, in the presence of a smoothing agent. Tests were conducted at conditions similar to those for industrial copper electrowinning. Mathematical correlations were developed for the following properties; density, conductivity and diffusivity which were compared to existing models in literature and thereafter applied in a COMSOL generated model. The model predicts, current distribution at the cathode surface, deposit thickness (morphology), concentration of species within the cell and current efficiency. Current distribution output shows the impact of several phenomena on the deposit generated including the relationship between increasing copper concentration and current density and lack of influence of acid concentration on this property. Keywords: Electrowinning, physicochemical properties, electrolyte composition, modelling

Jan 1, 2020

By E. Van Der Lingen

This paper provides a review on coloured gold, platinum, andpalladium intermetallic compounds, and discusses the models thatwere developed to obtain these materials. These compounds have acrystal structure of high symmetry, such as the CaF2or CsClstructures, ensuring distinct electron band structures. Variousexamples of coloured gold, platinum, and palladium intermetalliccompounds are provided. More in-depth discussion is provided on thepurple gold (AuAl2) and yellow platinum-aluminium (PtAl2)compounds with CaF2structure, as well as the purplish-pinkpalladium-indium (PdIn) compound with CsCl structure. Precious metal intermetallic compounds are used in jewellery andprovide a new dimension to design. Some of these compounds havealso found use as barrier coatings on turbine blades for jet engines,and more recently, research has been conducted into their potentialuse as catalysts, electro-catalysts, sensors, capacitors, and fordecorative coatings.

Jan 1, 2014

By N. V. Moraka

Mining companies are required by law to improve representation of women on their boards. However, progress in this regard has been slow. Boards of directors play an important role in formulating corporate strategy, risk assessment, and effective governance for sustained financial performance. Although some women have successfully maintained board seats, others have been unable to do so. It is difficult to ascertain whether women are being appointed as tokens to satisfy social pressures, as little is known about the experiences of women board members in mining, which may inform or refute tokenism. In-depth interviews were conducted with 20 women and 16 men across six listed mining companies. Thematic data analysis revealed evidence of tokenism where recruitment to mining boards is compliance-based and is informally driven by influential directors. Adverse boardroom experiences that further confirmed tokenism were reported by women, such as disregarding their contributions, condescending behaviour, and limited influence in decision-making, while other women sought to validate their competence and oppose social exclusion. This study recommends that a strong Board Chair and nominations committee is critical to ensure sustainable recruitment of competent and suitably qualified women; and further foster a culture of inclusivity and valuing gender-diverse boards.

Dec 13, 2023