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By J. C. Barry, J. H. van Laar, P. L. Crouse, H. Bissett, I. J. van der Walt

"Plasma-assisted spheroidisation of metal powders offers several technical advantages with respect to both the ease of materials handling and powder-metallurgical item manufacturing. Advantages include improved flowability, increased powder packing density, elimination of internal component cavities and fractures, changes in morphology resulting in decreased friction between particles and contamination during pneumatic transport and enhanced particle purity. In this empirical study, spherical iron particles were produced using a microwave plasma operating at atmospheric pressure and characterized using optical microscopy and SEM techniques. Iron powders were fed into the system at fixed operating conditions, resulting in particles with spherical structures. The theoretical estimate of the time required for melting to occur is 1.6 ms, an order of magnitude smaller than the actual residence time. IntroductionParticle design and functionalization has become an increasingly popular aspect of materials synthesis and powder-metallurgical item manufacturing. One such technique involves the spheroidisation and densification of feed materials, typically in the form of chemical powders with wide particle size distributions. The major benefits of powder spheroidisation include improved powder flowability, increased powder packing density and powder purity, reductions in internal voids and defects, as well as the ability to manipulate the particles surface morphologies (Boulos, 2004). Thermal plasma processing has the potential for scale-up and for producing industrial quantities of spheroidised powder.Thermal plasma technologies offer a wide spectrum of material synthesis and treatment options, amongst others the synthesis and spheroidisation of nano-sized ceramic and metal particles (Kumar and Selvarajan, 2006). The spheroidisation process occurs within the plasma discharge via in-flight heating and melting of the powder feed material, given high enough plasma temperatures (Fridman, 2008, p. 495). Surface tension in the molten droplets results in spherical, or nearly, spherical, powder particles being formed upon exiting the plasma discharge where the droplet undergoes rapid cooling and freezes. Quite often, the bulk density of these spherical particles is higher than that of the starting material (Boulos, Fauchais and Pfender, 2013, p. 42). The different plasma spheroidisation techniques reported include radio frequency (RF) induction thermal plasmas (Jiang and Boulos, 2006; Karoly and Szepvolgyi, 2005; Yuming, Junjie and Yanwei, 2013), nontransferred direct current (DC) thermal plasmas (Chaturvedi et al., 2014; Kumar and Selvarajan, 2008; Suresh, Selvarajan and Vijay., 2008) and microwave-assisted plasma processing methods (Chen, Gleiman and Phillips, 2001; Vanamu et al., 2004; Weigle et al., 2004)"

Jan 1, 2016

By H. Manurung, I. M. Bendiayasa, W. Astuti, and H. T. B. M. Petrus, F Anggara, K. C. Wanta

The leaching kinetics of cerium (Ce) and yttrium (Y) in sodium-hydroxide-digested non-magnetic coal fly ash using acetic acid were investigated. The variables analysed were pH, solid-to-liquid ratio (S/L), and temperature. The results show that cerium and yttrium's maximum recovery was 57.33% and 58.36%, respectively, under leaching temperature of 90°C for Ce and 60°C for Y at pH of 1,74 and 10 g/mL solid-liquid ratio in 240 minutes. Increasing the leaching time to more than 120 minutes did not significantly improve the results. After the magnetic separation process, the ICP-OES analysis shows a slight increase in the concentration of cerium and yttrium on nonmagnetic components. The XRD and ICP-OES analysis for the sample before and after silicate digestion shows that 40% silicate was dissolved. The calculation of apparent activation energies of leaching using the Arrhenius law for the leaching of cerium and yttrium gives 22.72 kJ/mol and 35.84 kJ/mol, respectively. The kinetic leaching model of cerium and yttrium all fit Dickinson's new shrinking core model. The calculation results show that the leaching reaction is controlled by combining interface transfer and diffusion across the product layer.

Nov 6, 2024

By M. Steyn

The coordination compound tetrakis(1,3-diphenyl-1,3-propanediona to)zirconium(IV), [Zr(DBM)4], (DBM = dibenzoyl methane/1,3- diphenyl-1,3-propanedionol) was synthesized and characterized by single-crystal X-ray diffraction. [Zr(DBM)4] crystallizes in the monoclinic space group P21/c (a = 24.769(4) Å, b = 10.216(5) Å, c = 19.314(4) Å, and = 101.541(5)°). The coordination geometry around the zirconium atom, formed by the eight O-donating atoms of the four -diketonates, is found to be a near-perfect square antiprism. Crystal packing is stabilized by C?H... interactions throughout the crystal lattice. This structure is a noteworthy example of the application of ambient condition synthesis of zirconium compounds in N,N'-dimethylformamide (DMF) as reaction and crystallization solvent, highlighting the possibilities of aerobic condition metal purification through chelation.

Jan 1, 2014

By A. Yañez, J. Yianatos, P. Vallejos, R. Grau

This paper presents an evaluation of the effect that the mineral feed characteristics have on the metallurgical performance in an industrial flotation circuit. Variables such as mineralogy, particle size, solid content and mineral grade were evaluated using a flotation simulator, which was previously developed and validated using industrial data from different concentrators. The metallurgical performance was evaluated not only from the point of view of recovery and concentrate grade, but also by analysing less common variables such as froth carrying rate, froth and collection recovery, water recovery and others. Then, new data from the industrial flotation circuit was used to complement this analysis and evaluate the simulator predictability by comparing simulated and measured data. The results allowed for the quantification of the significant effect that mineralogy and particle size have on recovery and/or concentrate grade. Therefore, the grinding stage and flotation cells design become important factors to avoid a significant loss in metallurgical performance when feed mineral characteristics change in an industrial operation. In this context, an evaluation of cells design and arrangement should be performed to compensate the loss in recovery and concentrate grade in order to find an optimal operating condition. Keywords: Flotation circuits, mineral feed, modelling, particle size, liberation, mineralogy

Jan 1, 2020

By G. B. Abaka-Wood, J. Addai-Mensah, W. Skinner

Recently, coal fly ash has become a potential candidate as a secondary resource of rare earth elements (REE). In this investigation, we studied the recovery of REE from fly ash from a commercial power plant. The specific aim was to assess the technical feasibility of recovering REE from the coal fly ash using conventional preconcentration methods, including gravity separation, magnetic separation, and froth flotation. The experimental results revealed that flotation achieved major gains in REE recovery and upgrading. However, during gravity and wet magnetic separation tests, the bulk of REE reported to the tailings. The results showed significant variations in the performance of the various beneficiation methods investigated. This study has confirmed that existing physical separation methods could be used to recover REE from coal fly ash prior to hydrometallurgical and pyrometallurgical processing, although some challenges persist.

Jan 2, 2022

By K. Wu, L. Li, D. W. Zhou, J. W. Yu

The presence of a fractured water-conducting zone (FWCZ) is of significant importance for the safety of underground mining under water bodies. When a coal mining area is covered with a thick layer of alluvial soil, the height, width, and distribution pattern of the FWCZ in the area shows unique features. The internal mechanism by which thick alluvial soil affects the FWCZ is still unknown. Using the Huainan coal mining area (HCMA) in China as a case study, we investigated the impact of thick alluvial soil on the height, width, and distribution pattern of the FWCZ through numerical simulation using the distinct element method, theoretical derivation, and data validation. The results indicate that a thick layer of alluvial soil inhibits the FWCZ height and increases the FWCZ lateral width. When the soil-to-rock ratio is greater than a certain value (the numerical result in this study is 15:18), the FWCZ height and width are affected by the thick alluvium significantly, and the thick alluvial soil alters the shape of the FWCZ from tall and thin to short and wide. The load exerted by the alluvial soil transfers downward to influence the FWCZ; however, this process is obstructed by the hard strata in the bedrock. Therefore, the vertical and lateral change trends show a similar step pattern. Our results can provide a basis for accurate calculation of the FWCZ height in mining areas with thick alluvial soil, to mitigate mine water hazards and increase the safety of underground mining in coal mines covered with a thick alluvium layer. Moreover, reducing the FWCZ height can help extend the upper extraction limit in coal mines covered with a thick alluvium layer, which reduces the thickness of the impermeable coal pillar and increases coal production.

Jan 1, 2016

By R. Dehghan, M. Zarei, A. Tohry, S. C. Chelgani

Typical depressants for selective reverse flotation of iron oxides from complex silicates do not generally show high levels of efficiency. Therefore, as a hot topic, there are several ongoing investigations in this area. The main aim of this paper is exploring the potential of using humic acid (HA) as a depressant in reverse cationic flotation of hematite from complex silicates. For such a process, the wettability and flotation behaviour of pure minerals (hematite and silicates) was investigated at pH 10 in the presence of HA and cationic collector. Adsorption mechanism of HA on these minerals was measured by zeta-potential and FTIR. Results of flotation tests showed that at the lower concentrations of HA, selective separation of silicates from hematite is beneficial, where the floatability of amphibole was higher than pyroxene. A higher separation efficiency of hematite through reverse flotation was observed in the presence of amphibole, in comparison with the presence of pyroxene. Wettability studies showed that HA has a significant effect on reducing the hydrophobicity of treated minerals with the collector. The adsorption, ZPC and FTIR test results indicated that HA was adsorbed on both silicates and hematite. However, the absorption intensity onto hematite was much higher than silicates. It was found that the adsorption mechanism of HA on hematite takes place through both strong H-bonding and ligand exchange. Keywords: Reverse cationic flotation, humic acid, iron oxide, complex silicates, surface adsorption

Jan 1, 2020

By J. Sjöberg, T. Savilahti, S. B. Umar

"Sublevel caving in Malmberget mine results in mining-induced surface deformation. One of the currently mined orebodies is the Printzsköld orebody. As mining deepens there is need to assess the behaviour of the cave formed in the subsurface above this orebody. Numerical analysis was used to assess the effects of extraction to deeper levels and perform strength parametric studies. Stress redistribution was studied, and the results showed high stress buildups in the hangingwall and the crown pillar. Two failure mechanisms have been identified – shear and tensile. Reducing cohesion by 50% increased the area of the yielded zone by more than 100% in the hangingwall.IntroductionThe Malmberget mine is owned and operated by the Luossavaara-Kiirunavaara AB (LKAB) mining company. Iron ore is extracted by large-scale sublevel caving. The mine comprises a total of 20 orebodies, about 10 of which are in production today (Figure 1). The mine is located in the municipality of Gallivare, about 100 km north of the Arctic Circle (Figure 2).Successful sublevel caving requires progressive caving of the orebody after initial blasting. This results in caving of the hangingwall, sometimes all the way to surface, resulting in surface deformation. As mining progresses to deeper levels a larger area is affected by deformation. Over the years, extraction from the Malmberget orebodies has led to deformation of the ground surface, affecting residential areas and existing infrastructure.Forecasting the caving process is not straightforward as it can be rapid or slow, depending on the rock mass conditions, stress conditions, the failure mechanisms at work, etc. Moreover, several of the orebodies in Malmberget are non-daylighting, which makes reliable caving analysis even more difficult, primarily since there is less available experience from such cases. The present study was designed to improve the understanding of the caving and deformation mechanisms at Malmberget, and in particularly for the Printzskold orebody"

Jan 1, 2017

By F. Nakhaei, M. Le Roux, Q. P. Campbell, S. Botlhoko

The results of coal sink and float tests are plotted as washability curves. Analysis of these curves indicates the most effective method by which the coal can be cleaned. Sink and float experiments are samplingdependent, destructive, and use toxic chemicals. The present research introduces an alternative method based on a 3D imaging system called RhoVol, in which the density of individual particles is determined from mass and volume measurements. A quantitative error analysis was conducted on coal sample density measurements obtained by RhoVol, and the main factors influencing the errors identified and investigated. The results show that the drawback of this technique is related to its not being able to detect hidden concavities in the particle, resulting in an overestimation of particle volume. Furthermore, it is difficult to capture the impact of porosity and cracks on the volume of coal particles obtained from 3D silhouette images. This mismatch between the RhoVol data and sink and float test results has led to attempts to apply neural network (NN) and linear regression techniques to produce a fully reliable model for correction and estimation of coal density. The NN approach offers superior predictive capability over linear regression, and the estimated density distribution is in line with the sink and float analysis. The root mean square error in estimation of density using the NN model was less than 0.05 g/cm³.

Aug 2, 2022

By S. W. Robertson, M. T. Golela, S. Mxinwa

South Africa has one of the largest Cr-related industries in the world and generates large amounts of Cr-containing smelter dusts. It is normal practice to scrub Cr from the furnace off-gas in water, and to recover the Cr by adsorption, followed by recycling of the loaded adsorbent into the furnace. A study was conducted to find a low-cost adsorbent that is capable of removing sufficient Cr from the solutions generated by scrubbing. The test work focused on the evaluation of different clay minerals (attapulgite, bentonite, and kaolinite) as adsorbents for Cr. Cr(VI) could only be adsorbed after prereduction with e.g. ascorbic acid (ASA). An 80% removal of Cr(VI) could be achieved from a solution containing 20 mg/L Cr using bentonite clay after reduction with ASA. Attapulgite and kaolinite adsorbed less than 55% Cr after reduction with ASA. Both ASA and ferrous salts were found to be suitable reducing agents. The use of acid mine drainage (AMD) was also investigated as a low-cost alternative reducing agent, as AMD usually contains iron. The Cr(VI) reduction potential of the AMD was determined by redox titration against a solution containing 50 mg/L Cr(VI). Studies show that AMD can potentially be used as a reducing agent in a Cr removal process if it is available on site.

Feb 12, 2024

By A. Chuma, K. J. Nyembwe, H. Simonsen, J. H. Potgieter

Different concentration techniques were evaluated for preconcentration of a mineral ore at a coarser size to avoid energy and resource wastage. Specifically, the aim was to reduce milling costs and energy required in the beneficiation of tin. In this study, cassiterite (0.17% Sn) was the mineral of interest in a pegmatite ore body associated with quartz (SiO₂ > 60%) and alumina (Al₂O3 > 20%). Three concentration techniques, namely dense media, shaking table, and flotation, coupled with characterization analysis, were used to assess the concentration response. The results confirmed that particle size and mineral liberation impact the separation process. High recovery and grade were obtained with gravity concentration methods (dense media and shaking table) for coarser (+300 to +212 μm) and intermediate (+150 to +53 μm) particle sizes. Lower recovery and grade were identified for much finer sizes (−53 to −38 μm). Flotation produced a high-grade product at a relatively low recovery and appeared to be only applicable to finer grains. Separation efficiency based on Schulz’s equation measured a segregation performance of 74.8% for dense medium separation and 60.7% for the shaking table for the coarse and intermediate particle sizes. Flotation only achieved a separation of 30%–40%. The results suggest that use of dense media separation as a rough preconcentration method prior to further grinding, and the utilization of a more advanced concentration technique for mineral recovery and upgrade, constitute a successful approach to improve process economics.

Apr 14, 2024

By M. Ye. Scheglov, G. I. Voiloshnikov, S. M. Ryakhovsky, V. E. Dementyev, V. N. Alekseev, N. S. Voiloshnikova

Irgiredmet has substantial experience on RIP and RIL technology for gold recovery, having started development of ion exchange technology in 1964. Irgiredmet specialists were involved in the majority of RIL and RIP projects in the former Soviet Union and Russia, and took part in commissioning of practically all plants using ion exchange technology. Laboratory and pilot plant tests were conducted to develop process design criteria for designing 15 RIP plants of the former USSR using bifunctional macroporous anionite AM-2B or its analogs. This paper is devoted to the laboratory, pilot plant testing and introduction of RIP technology conducted in cooperation with GC Pertopavlovsk. Medium base resin PuroLite S992 (PuroGold) was used as adsorbent. Some adsorption regularities and the affinity of resin to metal cyanide complexes were studied. Laboratory batch and continuous pilot tests on resin-in-pulp process were held for oxidised ores from Pioneer, Albyn and Malomyr mines (Amur region, Russia) owned by the Petropavlovsk company. A simplified flowsheet for gold elution and resin regeneration was developed. Alkaline cyanide solution was used as gold eluent and gold was recovered from eluates by electrowinning. Process design criteria were developed on the basis of the testwork results, and the plants were designed and constructed by GC Petropavlovsk. The RIP plant at Pioneer was commissioned in May 2008, at Malomyr in August 2010, and at Albyn deposit in December 2011. These plants are currently in operation at design performance at throughputs from 3 to 6.5 Mt/year. The primary gold ores of Pioneer and Malomyr deposits are refractory to cyanidation; Irgiredmet also completed continuous testwork on RIP technology using medium-base resin for pressure oxidation (POX) residues derived from their flotation concentrates. In 2019 a hydrometallurgical plant for the treatment of refractory gold concentrate after POX was commissioned at Pokrovsky mine (Amur region). Keywords: Gold ores, cyanidation, RIP, RIL –processes, ion exchange resin, medium base resin, adsorption, elution, electrowinning

Jan 1, 2020

By A. Golder, S. P. Dandapat, I. Roy

One of the consequences of large-scale opencast mining for coal is the disposal of an enormous volume of overburden material that needs to be removed. With the enlargement of opencast mines and associated high stripping ratios, the volume of overburden extraction is rising. Overburden from the initial mine cut has to be necessarily dumped outside the mining area until enough void is created inside the mine for back-filling operations. The quantity of overburden placed outside the mining area normally varies from 10% to 30% of the total overburden removal. The stability of these dumps placed outside the mining area is of prime importance from the point of view of smooth operations of the mines and safety of persons in and around the dumping area. Owing to increasing pressure on land use, mine operators do not have any other option other than to place the waste dumps very near to the surface edge of the pit, which may lead to failure of the topsoil benches of the working pit. This study identified major controlling parameters that influence a stable but economic combination of height and slope angle of external dumps located close to the edge of an open coal pit.

Nov 27, 2024

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 P. C. Pistorius, M. P. Maphutha, J. D. Steenkamp

Advanced high-strength steels (AHSS) are sophisticated materials being developed by the steel industry to mitigate challenges related to the performance of motor vehicles. To meet the requirements of AHSS, the ferromanganese alloys (FeMn) utilized in the production of the steel are required to contain acceptable levels of unwanted impurities, i.e. P, S, N, H, and C. The focus of the current study was to investigate dephosphorization of ferromanganese to produce a low-P alloy that could be effectively utilized in the production of AHSS. The study involved conducting laboratory-scale testwork to study the efficiency of CaO-based slag systems to dephosphorize FeMn alloys. The addition of Na2O, CaF2, and BaO to MnO-CaO-SiO2 slag was considered. The test work was carried out in a 25 kW induction furnace at temperatures of 1350°C, 1400°C, and 1450°C. The P partition coefficient (Lp) remained small at <1, which is an indication that dephosphorization had not been achieved. The baseline slag, comprising 40%CaO-40%SiO2-20%MnO, reported higher Lp values. Addition of Na2O and CaF2 did not show any further benefit. Substituting half of the CaO by BaO, resulted in similar Lp values to those of the baseline slag under conditions of 1350°C and 1450°C at 30 minutes. In summary, based on the Lp values obtained, the conditions investigated with the CaO-based slags appeared to have been unfavourable for dephosphorization of FeMn alloys, as most of this impurity element remained in the alloy.

Sep 1, 2021

By S. Durapraj, R. T. Masethe, U. Maqina, A. C. Adoko

This study investigates seismicity and rockburst control within the Merensky Reef and UG2 orebody of an intermediate-depth platinum mine located in South Africa's Bushveld Complex. Utilising a mine-wide seismic monitoring system, over 1,900 seismic events were recorded between April 2023 and May 2024, revealing complex seismic patterns driven by mining-induced stress changes. The largest event, with a magnitude of ML 2.0, underscores the seismic risks associated with mining at increasing depths. Key findings include the spatial and temporal variability of seismic events, with high seismic activity observed near pillars and geological structures. A significant portion of events correlated with pillar and foundation failures. Moment tensor analysis identified dominant failure modes, such as stress-driven fracture closures and dynamic pillar failures. To mitigate risks, the study emphasises advanced support system redesign and rockburst risk assessment using the rockburst damage potential (RDP) method. The research highlights the importance of monitoring, geotechnical compliance, and adaptive designs in enhancing safety and reducing seismic hazards in underground mining operations. The study applied the RDP framework, classifying damage across R1 to R5 scales, where most instances fell into low-risk categories (R1 and R3), indicating minor to moderate damage. However, data limitations and the tabular stoping method's complexity led to inconclusive results, highlighting the need for more robust data and customised risk assessment tools. Despite these challenges, the RDP approach provided valuable insights into rockburst mechanisms and the effectiveness of existing support systems.

Jan 12, 2025

By D. Skelton

The Renard kimberlite cluster is located in the Monts Otish region of Quebec, Canada. A Canadian National Instrument (NI) 43-101 compliant resource statement for the Renard kimberlites 2, 3, 4 and 9 and the Lynx kimberlite dyke was first issued in 2008 followed by a Preliminary Economic Assessment and the development of a conceptual mine plan. Following a successful drill program in 2009 that greatly expanded the amount of kimberlite in Renard 2, a revised resource statement was issued in December 2009 comprising 23 million carats of Indicated Mineral Resources and 13 million carats of Inferred Mineral Resources, a threefold increase on the previous estimate. The project is currently the focus of a second Preliminary Economic Assessment and it is expected that a full feasibility and permitting program will commence in 2010 leading to the creation of Quebec&apos;s first diamond mine by 2013.

Jan 1, 2010

By R. G. B. Pickering

Successful management of mining operations depend on the accurate and reliable measurement of performance as a monitoring instrument in a feedback and control loop. However, when changes are being considered, the probable effect of the change on bottom line results requires different measuring techniques incorporating an in depth understanding which can identify hot spots in the operation which exhibit strong sensitivity to change. The CSIR&apos;s Division of Mining Technology has therefore been devoting a considerable effort to the establishment of techniques which enable changes to be analysed in terms of their impact on the two key parameters describing mine performance, i.e. profitability and safety. This paper describes these techniques, outlines their application to some example situations and discusses planned enhancements. The first section of the paper addresses the profitability model, and this is followed by a section considering the mine safety model.

Jan 1, 1996

By H. M. Stewart, N. F. Dawson, J. P. Beukes, P. G. van Zyl, Q. P. Campbell, A. Jordaan, R. I. Glastonbury, L. N. Sadiki

"SynopsisThe physical properties of oxidative sintered pellets produced from typical South African UG2 ore are compared with the physical properties of pellets produced with conventional South African metallurgical-grade chromite ore (from the Lower Group 6 or the Middle Group 1 and 2 seams). A statistical evaluation of the cured (sintered) compressive strengths proved that pellets prepared from UG2 ore are likely to have the same, or better, compressive strength than pellets prepared from metallurgical-grade chromite ore. The cured abrasion strength of the UG2 pellets was also superior to that of the metallurgical-grade pellets. Scanning electron microscopy (SEM) backscatter, secondary electron, and elemental X-ray mapping were used to determine the reasons for the general superior strength of the UG2 pellets. The case study UG2 ore also required 13 kWh/t less energy for milling to attain the required particle size distribution prior to pelletization, which can lead to substantial cost savings. Results presented in this paper can be utilized by ferrochromium (FeCr) producers to better quantify the advantages and disadvantages associated with the use of UG2 ore for FeCr production.IntroductionChromite, a mineral of the spinel group, is the only commercially viable source of virgin chromium units. Geologically, commercial chromite deposits in the world are found in three forms, i.e. alluvial-, podiform-, and stratiform-type deposits (Murthy et al., 2011; Cramer et al., 2004). Alluvial deposits were formed by weathering of chromite-bearing rock with the subsequent release of chromite and gravity concentration by flowing water. However, these deposits are relatively small and of comparatively minor commercial interest. Podiform-type chromite deposits usually occur as irregularly shaped pods or lenses, and their distribution within a mineralized zone is usually relatively erratic and unpredictable, making the exploration of these deposits difficult and costly (Cramer et al., 2004). Stratiform-type chromite deposits occur as parallel seams in large, layered igneous rock complexes with more regular layering and lateral continuity (Cramer et al., 2004). The largest example of a stratiformtype chromite deposit is the Bushveld Complex (BC) in South Africa, which holds an estimated three-quarters of the world’s viable chromite ore resources (Cramer et al., 2004).Several chromite seams exist in the BC. The seams of economic interest are the Lower Group 6 (LG6), the Middle Group 1 and 2 (MG1 and 2), and the Upper Group 2 (UG2) seams (Cramer et al., 2004). The LG and MG seams are specifically exploited for their chromium content, while the UG2 seam is mined primarily as a source of platinum group minerals (PGMs) (Xiao and Laplante 2004). Extraction of the PGMs from the UG2 ore usually involves the liberation of the sulphide by milling and subsequent recovery of the PGM concentrate through flotation (Xiao and Laplante, 2004). Chromite in the PGM concentrate is undesirable; therefore, PGM recovery circuits are specifically designed to ensure maximum rejection of the chromite to the tailings stream. However, the chromite in the PGM tailings can potentially serve as feedstock for ferrochrome (FeCr) production, after beneficiation to increase the chromium content."

Jan 1, 2015

By R. Asamoah, P. Forson, S. Xu, W. Skinner, M. Zanin

In most auriferous hydrothermal deposits, gold is preferentially associated with pyrite and arsenopyrite minerals, with higher economic gold values noted for the latter and arsenian pyrite minerals. In this paper, surface (Cryo-XPS) and solution (EDTA extraction) analysis were used to characterise pyrite and arsenopyrite minerals under different aqueous conditions involving electrokinetic study and collector interactions to better understand ways of improving the separation of pyrite and arsenopyrite. The evidence showed higher surface oxidation at solution pulp pH values in the range of 4-11 for arsenopyrite relative to pyrite. The observed highest ratio of pyrite to arsenopyrite selectivity was 1.7 at collector concentration of 50 g/t and decreased with an increase in collector concentration. Keywords: EDTA extractable iron, selectivity index, differential flotation, grade engineering

Jan 1, 2020