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By B. Kweto, W. Legodi, C. van Buuren, R. F. Sandenbergh

Biooxidation, and especially the BIOX® process, is a viable, economical and environmentally attractive process to liberate gold hosted in refractory sulfides by oxidatively leaching the sulfides as soluble sulfates. The moderate to high cyanide consumption during the subsequent cyanidiation of the washed biooxidation residue is probably caused by the retention on the solids of labile sulfur species formed during the multi-electron oxidation process of sulfide to sulfate. In this work the nature and mode of transport of the cyanicides in the products from the mesophile BIOX® process, as well as that of the combined mesophile and thermophile bioxidation process, were considered and strategies to reduce cyanide consumption evaluated. It was found that labile sulfur species were the major cyanide consumers in the mesophile biooxidation product, forming predominantly thiocyanate during cyanidation. The transfer of labile sulfur species was only marginally decreased by more intensive and thorough washing of the biooxidation products with warm and hot water, intense stirring and warm caustic leaching. A major reduction in cyanide consumption was however achieved by using a combined mesophile and thermophile biooxidation process. Keywords: Biooxidation, refractory sulfide gold ores, cyanide consumption

Jan 1, 2020

By L. Makua, K. Langa, Ndlovu. S., C. Saguru

"Global demand for the three platinum group metals (PGMs) Pt, Pd, and Rh has been steadily growing due to their widespread use in emission control, industrial catalysis, and numerous other applications. The primary supply of PGMs is currently the mining industry. However, legislative, operational, and environmental challenges faced by many mining operations result in erratic supply patterns and deficits for these three metals. Naturally, recycling scrap material to recover Pt, Pd, and Rh has therefore aroused research interest in the scientific and engineering communities. Given that the majority of the global demand for these three metals is driven by emission control devices, autocatalytic converters are therefore a significant source of already processed and beneficiated PGMs for recycling.Although pyrometallurgical processes dominate the recycling industry, hydrometallurgical processes may offer certain advantages, chief among these being lower emissions and reduced energy consumption. In this investigation, scrap converter material was leached in acidic chloride media and the leach liquor subjected to solvent extraction and cloud point extraction (CPE) to recover the PGMs. The recoveries for Pt and Pd using Alamine 308® dissolved in kerosene with decanol as a modifier were 95% and 81%, respectively. The maximum recoveries using CPE after complexation with 2-mercaptobenzothiazole (2-MBT) in the presence of Triton X-100 and tin (II) chloride dihydrate as a reductant were 97% for Pd, 96% for Pt, and 91% for Rh. This demonstrates that CPE, although relatively new, may have some potential as a breakthrough PGM recovery technology. IntroductionPlatinum group metals (PGMs) have found a wide variety of applications in different industries due to their chemical, catalytic, and physical properties. PGMs are essential in automobile emission abatement, petroleum refining, and the pharmaceutical and electrical industries (Carabias-Martinez et al., 2000). However, the abundance of PGMs in the Earth’s crust is low and their primary sources are fast depleting (Crundwell et al., 2011).The high demand for PGMs, together with social, economic, environmental, and political aspects related to their production, has led to concerns about their future supply. This has resulted in renewed interest in recycling end-of-life material. PGM supply from recycling has doubled over the last decade, and currently contributes 22% to global supply (Johnson Matthey, 2016). This is in part due to the environmental, social, and operational challenges associated with mining of PGMs. For example, labour unrest, energy cuts, declining commodity prices, and declining ore grades have collectively made the mining landscape economically challenging (KPMG, 2015). On the other hand, the high content of PGMs in secondary sources makes their recovery from the increasing quantities of waste products important from a resource conservation viewpoint. Moreover, PGMs obtained through recycling have been demonstrated to have a 1% environmental cost from a life-cycle perspective, whereas PGMs obtained from mining contribute the remaining 99% of environmental cost (Bossi and Gediga, 2017). Sustainable resource recovery and the economic incentive of recycling have therefore been major drivers to justify investment in PGM recycling. The autocatalytic converter industry accounts for about 70% of the global consumption of these metals (Johnson Matthey, 2016) and therefore recycling spent converters has become a major source of Pt, Pd, and Rh (Figure 1)."

May 1, 2019

By J. Du, V. Shukla, C. R. Kumar, U. Shivangi, D. P. Chakraborty

During the processing of iron ores, a large quantity of low-grade tailings containing abundant iron values in fine particle size range is produced. Due to the increasing demand in the high-grade ores for metallurgical operations and the stringent environmental conditions imposed on mining activity, it is essential to utilise the waste tailing pond slimes. Recovery of iron values from these tailing ponds not only enhances the life of the existing operating mines, but also enables achievement of a sustainable process. Iron ore tailing/slime (-150 μm) is produced after scrubbing and wet screening of a low-grade iron ore. Tailing beneficiation of iron ore has been addressed either by flotation or wet high intensity high gradient separation. The present paper aims to recover iron values from discarded slime containing assay ~56% Fe, ~6.5% SiO2, and ~7.0% Al2O3 from the Noamundi processing plant by using a high gradient magnetic separator (HGMS). In this process, tailings are effectively processed with a vertical pulsating high gradient magnetic separator to produce a relatively high-grade iron concentrate. The results of investigation indicate that this novel process is capable of producing an iron concentrate assaying ~ 60% Fe and ~3.25% alumina with a yield of ~55 % on weight basis and recover > 65 % iron bearing particles from the tailings. More importantly, the corresponding tailing contained ~45% Fe. It was concluded that this novel process may be effectively used to recover iron values from low-grade hematite tailings. Keywords: Iron ore slime, Fe recovery, HGMS, yield, Noamundi

Jan 1, 2020

The treatment of gold-plant tailings with ferrous sulphate to remove the cyanide is currently in use, on several gold plants. In some cases there is scope for optimization the process. The present work provides a detailed study of the reaction between cyanide and ferrous sulphate. Optimal conditions for the removal of total cyande required a ph of 5,.5 to 6,5 and an Fe:CN molar ratio of 0,5. Ferrocyanide ion is shown to be unstable In aqueous acidic solution, with rapid oxidation to ferricyanide, (Fe(CN) 6 ), and formation .of Fe(CN)5H2O3- at pH values below 4, The precipitate from the reaction between cyanide and ferrous sulphate consists mainly 01 Insoluble Prussian blue, Fe4[Fe(CNI&!.3,and IS shown to be unstable in the presence of alkaline solution, since it decomposes rapidly at pH values above 7 to form ferrocyanide, (Fe(CN)6 ), in solution and various insoluble iron oxides,

Jan 1, 1992

By E. S. van Druten, M. C. Bekker

"The complete and successful closure of a mine in the South African environment remains problematic. Closure remains an elusive mining phase due to unclear roles and responsibilities, inaccurate closure management data, and the inability of stakeholders to conceptualize and integrate closure information into business processes. Currently there are no proven methods available to address the complexities encountered during a closure application, and to date no mine has been granted full closure. Many mines are left abandoned and unrehabilitated, resulting in risk to investors, surrounding communities, and regulators. This investigation aimed to determine, categorize, and rank reasons for unsuccessful mine closures. Focus groups consisting of public and private stakeholders were identified and surveyed through a structured, rank-order questionnaire to determine the relative importance of reasons why achieving formal and final mine closure remains elusive. Various requirements and aspects were identified and listed according to four categories: namely, primary, secondary, process drivers, and information sources. These aspects should be considered in the development of an integrated mine closure model.Background and rationalePrior to 1956, mine closures were not subject to legislative requirements, being merely governed by insufficient environmental regulations under the Mines and Works Act 27 (MWA) (Swart, 2003). In 1981 the Chamber of Mines (COM) published a document titled ‘The rehabilitation of land disturbed by surface coal mining’, which constituted the first notable contribution to environmental protection. This guideline was later referenced in the Minerals Act of 1991, which for the first time laid definite environmental burdens on the Mining Right Holder (MRH). The Minerals Act of 1991 was superseded by the current Mineral and Petroleum Resources Development Act (MPRDA) and the Mineral and Petroleum Resources Development Act Regulations (MPRDAR), which specify a regulatory process for mine closure applications and financial provisions."

Jan 1, 2017

By F. Sundqvist, B. Skawina, J. Greberg, A. Salama, M. Astrand, P. Ekbeck

Today’s mining operations require fast reporting and rapid rescheduling based on updated information. An automatic mine scheduling system could not only quickly reschedule but also propose alternative solutions. To avoid the financial and physical risks associated with testing such a system directly in operation, it could be first evaluated via discrete event simulation models. This would offer a safe environment to evaluate different operating rules and algorithms. In this study, this is achieved by integrating automatic scheduling software with a discrete event simulation model.

Jun 1, 2021

By Y. J. Cao

The purpose of this study was to investigate the flotation behaviour of unburned carbon in a cyclonic-static microbubble flotation column (FCSMC). The ash sample, collected from a power station in Guangdong province of China, was characterized by size analysis, X-ray diffraction, contact angle measurements, and X-ray fluorescence. The effect of the column flotation operating variables on the removal of unburned carbon from the fly ash was systematically studied. The feasibility of separating unburned carbon and ash was determined from the removal rate of unburned carbon (RUC) and loss on ignition (LOI). Within the range studied, the optimum diesel oil dosage was 1200 g/t, abies oil dosage was 600 g/t, pulp density was 20 per cent, superficial gas velocity was 1.4 cm/s, and circulating pressure was 0.20 MPa. The results indicate that the FCSMC technique is effective in removing the unburned carbon from the fly ash, which can be attributed to the generation of microbubbles and the continuous cyclonic circulation method. Under the optimized conditions, a cleaning ash with 2.13 per cent LOI and 94.21 per cent RUC was obtained.

Jan 1, 2012

By S. Annavarapu

"Fragment size distributions play an important part in the design and planning of block cave mining operations. Though several methods have been proposed for estimating fragment size distributions in advance of mining, the calibration of these estimating procedures to field measurements has been a challenge. The Block Size Estimator (BSE) program was developed for providing an assessment of primary fragmentation expected in a block cave mine using drill-core piece length data and joint characteristics from the exploration and geotechnical evaluation programmes. In order to validate the results from the BSE program, the drill-core piece length data and the joint characteristics in different rock types from the DOZ block cave mine in Indonesia were used to help generate fragment size distributions in different areas of the mine. The predicted fragment size distributions were compared with the fragmentation observed at the drawpoints during operation of the mine.This paper presents the details of the validation of the fragment size estimates by the BSE program using fragment size distribution data from the drawpoints at the extraction level at the DOZ block cave mine, and the challenges encountered in developing reasonable correlations between the estimated and measured fragment size distributions. IntroductionThe assessment of fragmentation is an important aspect of the design and planning of the block cave mining method, and forms an integral part of the design of the excavations at the extraction level and the selection of material handling systems for transporting the ore to the processing stations. Secondary blasting requirements can also be estimated based on the fragment size distributions developed for the block cave (Laubscher, 1994).Several methods of estimating fragment size distributions in block cave mines have been developed based on joint set parameters estimated from structural data from oriented core drilling campaigns and mapping of available excavations and outcrops. The BCF program (Esterhuizen, 1999) estimates the fragmentation using a combination of empirical, analytical, and rational methods to model the behaviour of materials during the primary and secondary fragmentation processes. The program JKFrag uses advanced tessellation of joint traces to create rock blocks and then generate fragment size distributions (Brown, 2002). Nickson, Coulson and Hussey (2000) presented the details of processing of the geotechnical data from the Mont Porphyre project, including an assessment of block sizes from the data collected on the core logging sheet. The distance between natural fractures was used to create distributions of block lengths, and a distribution of potential block sizes was estimated assuming that the blocks had equal dimensions in all directions. The results agreed closely with the results of the BCF program. Hadjigeorgiou, Grennon, and Nickson (2002) demonstrated the use of oriented borehole data to provide characteristic block size distributions for a mining project using a software package called Stereoblock, which generates a three-dimensional joint network for a given volume and calculates the volumes of blocks created by the intersections of these joints, simulated as circular planes. The distributions of joint orientation and joint spacing generated from statistical analysis of the oriented core data are used for the creation of the Stereoblock model. The diameter of the circular planes representing the joints is determined based on the mean and standard deviation of the joint trace length obtained from scan-line mapping."

May 1, 2019

By F. Mwaura

"The aim of the audit was to determine whether the mining project environmental impact assessments (EIAs) in Kenya are undertaken according to international best practice. A sample of 50 EIA reports for the 2007–2016 period was evaluated using 18 criteria in the Environmental Law Alliance Worldwide (ELAW) guidelines. The findings showed that only two criteria were considered ‘excellent’ according to the ELAW guidelines, namely baseline environmental assessment and prediction of physical impacts. Six criteria were found to be ‘satisfactory’, including prediction of social impacts, analysis of alternative options, and impact mitigation. The reports were quite weak in terms of: consideration of all phases in the mining cycle, environmental regulatory framework, prediction of biological impacts, stakeholder consultation and engagement, integration of human right issues, and integration of climate change and cost-benefit analysis. It is therefore recommended that the Kenyan National Environment Management Authority (NEMA) should consider tightening the EIA terms and conditions in the approval of statutory terms of reference (ToR) for full-scale mining EIAs to ensure improved performance of EIA as a tool for environmental protection. IntroductionThe nexus between society and the environment has continued to generate interest because the environment is the source of goods and services that sustain the various needs of human beings as outlined in the UN sustainable development goals (SDGs) (Armstrong and Peart, 2000; Sutton 2004; Chakrabarti 2007; Strange and Bayley 2008). All the five generic categories of societal needs, namely physiological needs (food, water, clothing, medicines, etc.), residential and occupational needs (shelter, transport, energy, etc.), economic needs (tradeable goods and services), leisure and recreational needs (tourism), and cultural and spiritual needs (e.g. sacred resources and ecosystems) (Mwaura et al. 2016) are addressed by the environment. Consequently, a wide range of development sectors have been established around the world in order to address the above needs (Lederer, Galtung, and Antal, 1980; Rammelsberg et al., 2006; Noonan, 2014). All these development sectors rely entirely on the environment for their proper functioning, as shown in Table I."

May 1, 2019

By K. H. Zhang, Y. P. Gao, J. Q. Zhao, Q. Li, J. C. Ma

Compared with sinusoidal oscillation, non-sinusoidal oscillation enhances the ability to control waveform and meets different oscillation requirements by adding an independent parameter, which is the key technology for high-efficiency continuous casting. A new waveform of mould non-sinusoidal oscillation is proposed in this paper, that is, a velocity waveform that is composed only of straight lines and parabolas, which not only has good dynamic characteristics, but also further enhances the feature of non-sinusoidal oscillation. Compared with sinusoidal oscillation, the negative strip time is reduced by 15.9%, the maximum negative strip velocity difference is increased by 38.3%, and the maximum positive strip velocity difference is decreased by 27.8%. The formulas of oscillation process parameters can be clearly deduced, and the isoplethic curves of oscillation process parameters when multi-parameter simultaneously changes are drawn. The negative strip time decreases as the modification ratio, frequency, and casting speed increase, but increases as stroke increases. In order to maintain the stability of negative strip time, an oscillation synchronous control model for optimising oscillation basic parameters was developed. Through practical application, the mean oscillation mark depths decreased by 10.1 μm and the flux consumption is increased from 0.37 kg/t to 0.45 kg/t in the non-sinusoidal oscillation model, which meets the requirements of normal production.

Oct 24, 2025

By T. Steyn, M. Fofana

"One of the most important performance indicators of a dense medium cyclone (DMC) circuit is the Tromp curve, and by extension the separation density and Ecart Probable (Ep) values. The densimetric profiles of DMC product streams have been traditionally acquired using heavy liquid sinkfloat analysis, which has certain disadvantages, such as the associated safety and health risks. More recently, non-toxic media such as lithium hetero-polytungstates (LST) have been used, with the desired densities being achieved by maintaining the solutions at specific temperatures. However, the high costs of these liquids can be prohibitive. The long turnaround time of the sink-float analysis is a further disadvantage for timeous interventions to the operating set-points of the DMC process.The RhoVol technology can generate the density distribution of a batch of particles in a rapid, accurate, repeatable, and safe manner. Additional data of interest, such as particle size and shape, are also measured and reported on a per-particle basis. Furthermore, samples can be sorted into discrete sorting bins based on any of the measured parameters of the particle, making further analyses of the material possible.This technology has applications across all commodities that use the DMC, particularly in the size fractions –25 +8 mm and –8 +3 mm. To date, laboratory results have proved very encouraging – separation densities are within 5% of traditional sink-float results, and the technology is being introduced to diamond DMC plants. IntroductionDense medium separation is a commonly applied beneficiation technique for the density separation of valuable products from crushed ores. The industrial applications of dense medium separation have been summarized and reviewed by various authors (Scott and Napier-Munn, 2000; Bosman, 2014; Napier- Munn, 2018). Dense medium cyclones (DMCs) are widely used in the coal and diamond industries to produce clean coal or to preconcentrate kimberlitic ores, respectively. Cyclone performance (separation density monitoring) techniques are varied. In the mineral industry. Density tracer tests (Napier- Munn, 1985, 2014; Davis, Wood, and Lyman, 1985) without mineral material, are widely used, although their accuracy in predicting operating cut-points becomes limited once mineral material is introduced. More recently, radio frequency tracers have been also used for the determination of cyclone efficiency (Partition Enterprises, 2017)."

Feb 1, 2019

By T. Nesane, S. S. Mnyakeni-Moleele, L. C. Murulana

The effectiveness of two synthesized ionic liquids, 1-(benzyloxy)-1-oxopropan-2-aminium 4-methylbenzenesulfonate (1-BOPAMS) and 4-(benzyloxy)-4-oxobutan-1-aminium 4-methylbenzenesulfonate (4-BOBAMS), were evaluated for mild steel corrosion inhibition in 1.0 M hydro-chloric acid solution, using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and gravimetric techniques. Organic moieties responsible for the adsorption process on mild steel surface were investigated using Fourier transform infrared spectroscopy (FTIR). Gravimetric analysis revealed that the inhibition efficiency of 1-BOPAMS and 4-BOBAMS increased with concentration, with maximum inhibition values of 90.32% and 97.91%, respectively, at the highest concentration of the inhibitors. Gibbs free energy (ΔG°ads) values indicated a strong interaction between the mild steel surface and the molecules of the ionic liquids, and that the adsorption process was spontaneous. These values also show that the inhibitive nature of ionic liquids against mild steel corrosion is caused by a mixedtype of adsorption film formed on the steel surface. The Langmuir adsorption isotherm was used to describe the adsorption of ionic liquid molecules onto the mild steel surface. Polarization curves showed that 1-BOPAMS and 4-BOBAMS have a similar effect on both the anodic and cathodic half-reactions, indicating that they prevent the dissolution of mild steel through both physical and chemical process. Nyquist plots were defined by incomplete semicircle capacitive loops, showing that the charge transfer mechanism controls the corrosion of mild steel in acidic solution.

Apr 1, 2021

By M. Åstrand, M. Johansson

"Advanced planning and automation are increasingly important in modern mines. Sophisticated methods for long-term mine planning are often used, and the advent of autonomous machines makes the actual operation more predictable. However, the interface between these two timescales, i.e. the scheduling of the mobile production fleet, often limits the ability to operate mines at maximum profitability. We show how scheduling the production fleet in an underground mine can be modelled as a flow shop. A flow shop is a general abstract process formulation that captures the key properties of a scheduling problem without going into specific details. Thus, the flow shop enables mine scheduling to reap the benefits of scheduling research from other industries. We review recent results from the mining community and the flow shop community, and introduce scheduling methods used in these two fields. This work aims at providing value to researchers from the mining community who want to leverage their skill set, as well as to theoretical researchers by presenting the mining process as a potential application area. Lastly, we discuss the results, and outline some future challenges and opportunities facing the industry. IntroductionThe margins in underground mining are constantly under pressure since costs increase as the mine becomes deeper. One major component influencing the operational performance, and thus the profitability of an underground mine, is how the mobile machinery and staff are coordinated. Today, the coordination of the underground fleet, i.e. scheduling of the machines, is mostly done manually, with methods that are stretched to their limit and with no guarantees on performance. According to a survey of more than 200 high-level executives in mining companies around the world (Mincom, 2011), the top challenge for modern mines is to maximize production effectiveness, rather than improving the reliability of individual items of equipment. This highlights the importance of coordination on a system level.The effectiveness of mine production can be increased by introducing supportive algorithms in the scheduling process. These algorithms enable mines to construct optimized schedules with respect to custom metrics. Additionally, manual scheduling is a tedious and error-prone task where the performance is heavily dependent on the scheduler. To reduce the staff dependency, supportive algorithms can help to achieve more uniform outcomes, resulting in a more predictable process. In turn, this increases the transparency of the mining process through the entire production chain. It is worth noting that automatic scheduling has proved beneficial in many other industries, such as chemicals and metals (Floudas and Lin, 2004; Tang et al., 2001)."

Dec 1, 2018

By I. J. Geldenhuys

South Africa’s mining and metals industries have an illustrious history dating back to the Late Iron Age. We live in a complex and data-intensive world that has already fundamentally changed how we work and live. The outbreak of the global COVID-19 pandemic in 2020 resulted in immeasurable suffering worldwide, but the crisis also accelerated many technological developments and altered the way we think about, and experience, technology and work. Problem-solving requires new and rapidly changing skills to manage the data tsunami. Whether at the rock face or on the processing plant, the fundamentals have not changed, although how we interact with minerals and their properties has changed dramatically. Sustainable processing and design are non-negotiable if we genuinely want to achieve the aim of the cradle-to-cradle principle. As we venture forth, what can scientists, engineers, technologists, and mathematicians learn from history? History is data presented in a context; sometimes, the context is also important. We exist in an age of data, with most of the world’s data created in only the past two years. History can enhance our understanding of the present and enhance our future outcomes. Lessons from history can help provide insights into making ethical and sustainable choices related to technology or engineering in the mining and metallurgical industry. Shifting the perspective of mining and metallurgy professionals from a narrow focus on complex technical solutions towards a broader context for problem-solving and designs that includes the entire ecosystem is crucial. In other words, using or reflecting on historical process development is, at its core, systems thinking.

Sep 1, 2021

Rock mass classification systems are extensively used in rock engineering design work, and mine design is no exception. Among the systems most widely used for mining-related design work are the NGI 0-system (Barton et al., 1974), the RMR system (Bieniawski, 1976), the MRMR system (Laubscher and Taylor, 1976) and, more recently, the GSI system (Hoek et al., 1998). Classifying the rock mass is widely seen as being the fieldwork required to characterize the rock mass and enable the application of empirical design methods associated with the different classification systems. This paper argues that it is fundamentally important to recognize the distinction between rock mass characterization and rock mass classification. These two processes should, in most cases, be separated from each other. Rock mass characterization should be used to determine the intrinsic properties of the rock mass independently of the application; i.e. independent from the infrastructure to be designed, the size, shape, and orientation of the excavation(s) or pillar(s), etc. Rock mass characterization should also be compatible with most classification systems and empirical design methods to be used. Rock mass characterization is the background fieldwork required to perform rock mass classification and/or engineering design work. Rock mass classification is the subsequent step to the characterization, and an integral part of the design process. Parameters that vary according to the design, such as the relative orientation of geological structures compared to the opening or the mine-induced stresses, should be calculated as part of the rock mass classification and design process, rather than during the rock mass characterization process. The failure to distinguish between rock mass characterization and rock mass classification can lead to major design errors and poor results.

Jan 1, 2012

By M. Z. Emad, A. Khan, N. Abbas, K. G. Li

Probability-based empirical methods were employed as an alternative approach to predicting uncertainties associated with rock mass properties. The focus was on developing probabilistic spreadsheets to forecast rock mass classification indexes. Histograms were constructed to describe the best distribution in predicting rock mass properties. The developed models also offer utility in predicting the impact of discontinuities within the rock mass on rock strength and rock mass classification systems. Statistical analyses identified volumetric joint count, joint spacing, joint frequency, and rock strength as the most influential parameters. Moreover, the statistical analysis revealed varying degrees of correlation among different rock mass properties. While some properties demonstrated significant correlations suitable for modelling, others did not align well with any correlation model. The results highlight the need for a comprehensive approach to rock mass characterization, considering multiple factors beyond volumetric joint count. Geological complexities, including tectonic activity and weathering processes, may obscure direct correlations. These results emphasize the importance of empirical modelling and detailed site investigations for accurate assessment of rock mass quality and stability in the Himalaya.

Jun 10, 2024

By A. Rahmanab, A. Torpy, M. I. Pownceby, M. N. Zaman, N. Haque, W. Bruckard, J. Tardio

Ilmenite is the principal feedstock for producing TiO2 - used in paints, plastics and paper and the production of Ti metal. The Brahmaputra River system in Bangladesh represents a potentially new source of ilmenite concentrated within sandbar placer deposits and the current study presents results from beneficiation and characterisation studies conducted on Brahmaputra River Fe-Ti oxides. Characteristic of fluvial systems, the ilmenite concentration is low (~0.5 wt-%), however extensive annual dredging for waterway navigation provides the economic impetus to recover saleable ilmenite. The Fe-Ti oxide suite derived from magnetic fractionation comprises homogeneous ilmenite, titanohematite and hematite, although many grains exhibit complex exsolution within the (Ilm-Hem)ss series. The textural variability results in difficulty generating a pure ilmenite feedstock with the bulk concentrate typically being low in TiO2, containing 31.0 wt-%TiO2 and 62.7 wt-% (Fe2O3). Results are interpreted via an analysis of the implications for producing a commercial-grade ilmenite concentrate suitable for TiO2 production. Keywords: Ilmenite, titanohematite, Fe-Ti oxide exsolution, TiO2 production

Jan 1, 2020

By D. F. Malan, T. E. Oates

A recent experimental pillar extraction project at a UG2 bord-and-pillar mine presented a unique opportunity to compile a new pillar database. Currently, the South African hard rock bordand- pillar mines are designed using the Hedley and Grant formula with a modified K-value. This empirically derived formula was developed for uranium mines in the Elliot Lake district of Canada. The use of this formula for the design of pillars in South Africa is questionable. Very few pillar failures have nevertheless been observed and its current calibrations for the various reef types are possibly too conservative. A new UG2 pillar database of 66 pillars, of which seven are classified as failed, was compiled by the authors. This enabled a revised ‘first-order’ calibration of the K-value for the Hedley and Grant formula. The new estimated value for the UG2 is K = 75 MPa. This gives a pillar strength that is more conservative than the PlatMine formula. This work should nevertheless be considered as only a preliminary calibration as the database was small. Further work is also required to determine whether the exponents in the formula for the width and height parameters are appropriate for UG2 pillars.

May 3, 2023

By I. Silin, H. Wotruba, A. Liono, I. Volobayev, Y. Rubinstein, D. Gürsel

Old, abandoned or in situ processed and storaged tailings can be a potential source of remained valuable metals and minerals. By reprocessing of tailings, it is possible not only to achieve economical profit from recovery of valuable metals, but also to reduce environmental damage caused by tailings such as generation of acid mine drainage from sulfide minerals, mobilization of heavy metals, soils and groundwater contamination. In addition, storage facilities can be successfully redesigned with modern geotechnical requirements and monitoring to avoid a dam collapse of abandoned tailings. In this case study, the processing of low grade abandoned tailings was investigated. Copper (0.15%), cobalt (0.032%) and gold (0.35 ppm) were determined as main valuable and recoverable metals. Cobalt occurs as cobaltite and cobaltiferrous pyrite, while chalcopyrite represents copper. The fine fraction of tailings below 32 μm is enriched with cobalt and copper. Preliminary test-works with initial tailings sample were aimed to recover copper, cobalt and gold. The previously tested magnetic and gravity separation could not recover the metals in a pre-concentration step. Flotation tests of the tailings sample had shown a suitability for flotation without previous regrinding of the tailings. The valuable minerals are first proposed to be recovered by collective flotation, followed by a selective circuit with production of a low grade copper concentrate and a cobalt bearing pyrite concentrate. Based on various tested collectors, amounts of sulfidisation agents and activators, a suitable reagents regime was determined and used for up-scaling by locked cycled test. Keywords: reprocessing, tailings, copper, cobalt, gold, flotation, cobaltite, cobaltiferrous pyrite

Jan 1, 2020

By A. Angelov, U. Peukerd, S. Gaydardzhieve, A. Stefanov, K. Grossman, V. Stoilov

Flotation concentrate originating from the Asarel-Medet porphyry copper mining and processing complex in Bulgaria has been subjected to regrinding using a Ro-Star mill; the effects of which on the downstream metallurgical behaviour are discussed. Particularly the effect on the liberation degree was studied through an optical microscopy and MLA-SEM automated mineralogy. On the other hand, copper selective flotation of the reground bulk concentrate was realised to evaluate the anticipated metallurgical improvement. Process parameters such as involvement of prior hydrocycloning and variation of collector dosage have been evaluated. Within a two-minute residence time inside the Ro-Star mill, an improved liberation degree of the copper bearing minerals has been observed. As a consequence, enhanced copper recovery and selectivity against pyrite was noted. It has been found that in order to guarantee efficient flotation of the resulting ultrafine particles, a modified flotation regime (i.e. changing collector suite and dosages) should be followed. Keywords: RoStar Mill, liberation, flotation recovery, ultrafine particles

Jan 1, 2020