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Mixtures of MnO and graphite were reacted under argon at temperatures ranging from 1200 to 1425°C, and the loss in mass of the mixture was recorded continuously. The results showed that the rate of reduction of MnO increased as the temperature increased and the ratio of MnO to C decreased. The effect of the particle size of MnO and of graphite on the rate of reduction at I350°C was very small in the range 63 to 250 µm for MnO and 45 to 355 µm for graphite. The rate of reduction at I350°C was increased markedly by the addition of Na2CO2 and K2CO3, was slightly increased by the addition of Fe2O3, was unaffected by the addition of CaO, MgO, and AI2O., and was decreased by the addition of SiO2. Some CO2 was always present in the effluent gas, and this was taken as evidence that the reduction of MnO occurred by way of CO2 as an intermediate product. The activation energy of the ratecontrolling step was 57,5 kcal, and this was similar to the measured activation energy for the gasification of graphite by CO., namely, 61,S kcal per mole of graphite. A simple kinetic model was derived on the assumption that the gasification of graphite was the ratecontrolling step, and the results over the temperature range 1200 to I425°C, when plotted in the appropriate form, yielded straight lines as predicted by the model.

Jan 1, 1980

1. Book review Steels- microstructure and properties, by R. W. K. Honeycombe. London, Edward Arnold, 1981. 244 pp. Rl9,90. (Reviewer: P. T. Wedepohl) 2. New books Decision making in continuous steel casting, by Mark A. Vonderembse. New York, Bowker Publishing Co., 1981. U8 pp. Handbook on continuous casting, by E. Herrmann' Diisseldorf, Aluminium-Verlag GmbH, 1980. 742 pp. Cloth DM 1250, leather DM 1500. Pore structure analysis from a nitrogen adsorption study of porous materials using a volumetric method. User's guide to the FORTRAN programs: PORESl and PORES2, by E. G. K. Woods. Pretoria, CERGCSIR (P.O. Box 395, Pretoria 0001), May 1981. Oil and gas from coal, by Dick Olliver. London, Financial Times (10 Cannon Street, London EC4P 4BY), 1980. £120. The seventies: a review, the eighties, a preview, by W. Hibbard (editor). Oxford, Pergamon, 1981. 120 pp. £12.50. Computers in materials technology, by T. Ericsson editor). Oxford, Pergamon, 1981. 230 pp. £14.50.

Jan 1, 1981

By D. D. Aksenova, V. A. Ignatkina, L. A. Samatova, A. V. Lygach, E. D. Shepeta

Calcium minerals such as scheelite, phosphate, apatite are valuable minerals, which have similar flotation properties to the calcium gangue minerals. An additional problem is the fine dispersion and close mineral association of valuable and other minerals. Low polar compounds (non-ionic surfactant), such as fatty iso alcohols, neonol and phosphol, and their combinations with sodium oleate have been studied using flotation of monominerals and ore flotation; ATR IR spectroscopy and TEM for study surface of minerals; UV spectroscopy for control solubility, aggregation and de-aggregation processes. Increase in solubility of fatty acid collectors was confirmed by low soluble (heteropolar) compounds. Oxyethylated esters of phosphoric acid are adsorbed on phosphorite by -O2PO2R2 and on other rock minerals by donation of OH bond. Same effect shows difference of adsorption of fatty iso alcohols on calcite and scheelite. The different forms of adsorption of ionic and nonionic compound on a sparingly-soluble mineral surface creates distinction of the flotation kinetics and technological balance of ore flotation. The results of the separation of flotation of scheelite from calcite depend on the order of pouring into pulp of fatty iso alcohols and oleate, and their ratio in the mixture. Increasing scheelite recovery into rougher scheelite concentrate by 3.6% for both the flotation and sludge classes was obtained. Calcite recovery varied slightly upwards or downwards by 0.8-2.4%. The use of the non-ionic surfactant phosphol in combination with a fatty acid soap allows for obtaining a phosphate concentrate with more than 28% P2O5 content and almost 80% recovery in flotation operation. It is not obtainable with other reagent regimes. Keywords: Flotation, calcium minerals, oleate, fatty isoalcols, neonol, oxyethylated esters, adsorption

Jan 1, 2020

By deur R. Dippenaar

'n Kort kursus oar die teorie en praktyk van hittebehandeling is vanaf 29 Junie 1981 tot 3 Julie 1981 in die departement Materiaalkunde en Metallurgiese Ingenieurswese aan die Universiteit van Pretoria aangebied. Die kursus is dour dosente van die departement opgestel en in samewerking met 'n aantal gassprekers aDder beskerming van die Suid-Afrikaanse Instituut vir Mynbou en Metallurgie aangebied. Tunnelling The Third International Symposium on Tunnelling is to be held in Brighton from 7th to 11th June, 1982. Professional development seminars The Department of Mining and Metallurgical Engineering of McGill University is to hold the following seminars during 1981-1982.

Jan 1, 1981

A colloquium on 'Recent Developments in Wearresistant Materials', organized by the Technical Programme Committee: Physical Metallurgy of the SAIMM, was held at Mintek on 7th May, 1985. After delegates had been welcomed by Dr P.T. Wedepohl, Chairman of the Organizing Committee, Mr J.D. Austin, President of the SAIMM, delivered the opening address. Corrigenda to article on copper* I read with considerable interest the recent articles on copper by Mr C.O. Beale as published in the Journal. However, in Part 11 the section dealing with Prieska Copper Mines (Pty) Limited contained several factual errors, details of which are given below.

Jan 1, 1985

By N. B. Strydom, P. L. Jooste, H. F. Kotze, W. H. Van Der Walt

Note: A revised method of heat acclimatization by N. B. STRYDOM, W. H. VAN DER WALT, P. L. JOOSTE, and H. F. KOTZE INTRODUCTION Climatic-room acclimatization was introduced in the gold-mining industry in 1965 and was rapidly adopted by all mines because it reduced the number of days required for heat acclimatization from 12 to 8. The method has been adequately described in previous papers1, 2 but, briefly, requires four hours of heat exposure per day while the work rate is progessively increased from 35 W on Day 1 to 70 W on Days 7 and 8. Several attempts to shorten

Jan 6, 1976

R. T. Whillans and D. A. Cranstone. Canadian reserves of copper, nickel, lead, zinc, molybdenum, silver and gold as of January 1, 1979. Hull (Canada), Canadian Government Publishing Centre, 1980. C$2.40. Brewer, Stephen. Solving problems in analytical chemistry. New York, Wiley, 1980. 512pp. $8.95. E. K. Turkdogan. Physical chemistry for high temperature technology. New York, Academic Press, 1980. 464 pp. $49,50. G. B. Fettweis. World coal resources. Amsterdam, Elsevier, 1979. 416 pp. U.S. $80.50 Dfl. 165.00 Canadian mines: 1979 perspective. Hull (Canada), Canadian Government Publishing Centre, 1980. C$2.40. Clarence Karr (ed.). Analytical methods for coal and coal products, Volume 3. New York, Academic Press, 1979. 656 pp. Charles B. Gill. Nonferrous extractive metallurgy. New York, Wiley, 1980. 500 pp. $30.00. M. Kuzvart and M. B6hmer. Prospecting and exploration for mineral deposits. Amsterdam, Elsevier, 1978. 432 pp. U.S. $68.25. Dfl.140.00. Martin A. Elliott (ed.). Chemistry of coal utilization, supplementary volume 2. New York, Wiley, 1980. 3000 pp. $150.00. M. Radetzki and S. Zorn. Financing mining projects in developing countries. Aedermannsdorf (Switzerland), Trans Tech. Publications, 1979. 200 pp. SFr. 48.00 (hard cover), SFr. 38.00 (soft cover). Charles G. Schofield. Homogenisation/blending systems design and control for minerals processing. Aedermannsdorf (Switzerland), Trans Tech Publications, 1980. 332 pp. SFr.98.00 (hard cover), SFr.48.00 (soft cover). A. V. Smoldyrer and Y. K. Safonov (translator: W. C. Cooley). Pipeline transport of concentrated slurries. Aedermannsdorf (Switzerland), Trans Tech Publications, 1979. 176 pp. SFI'. 115.00. V. M. Karasik (translator: W. C. Cooley). Slurry hydrotransport of minerals and tailings. Aedermannsdorf (Switzerland), Trans Tech Publications, 1979. 156 pp. SFr.1l5.00. S. P. Turchaninov (translator: W. C. Cooley). The life of hydrotransport pipelines. Aedermannsdorf (Switzerland), Trans Tech Publications, 1979. 158 pp. SFr.115.00. NIM reports Report 2037 The removal of contaminants from recycled water in a mineral-flotation plant. Report 2054 The determination, by X-ray spectrometry, of trace amounts of tin in titanium-bearing ores and concentrates and in siliceous materials. Report 2063 Aerosal deposition and carbon-rod atomization of gold. This report describes the determination, by flameless

Jan 1, 1980

By M. Rudolph, E. Schach

Tecflote is a new group of nitrile-based collectors for sulfide flotation. Water insolubility results in some interesting implications for the actual mechanism. It is not yet understood if Tecflote is directly adsorbed on the mineral surface as emulsion droplets or if it is only active at the air-water interface, affecting the interfacial rheology or electrostatic- and Van der Waals interactions, which have a direct impact on the bubble-particle contact. Different investigations including contact angle measurements, AFM studies and micro-flotation experiments are conducted to obtain a better understanding of the actual mechanism of Tecflote. Due to the reagent’s insoluble character, the Langmuir-Blodgett technique is used to investigate its behaviour in the air-water interface and to deposit defined layers of Tecflote on mineral substrates for the above-mentioned studies. An interferometric set up is used to investigate the influence of Tecflote on the film thinning between an air bubble and a mineral substrate. In addition, possible synergistic effects for the combination of Tecflote and conventional frothers (e.g. MIBC) are studied. Keywords: Sulfide flotation, insoluble collector

Jan 1, 2020

By J. Petersen, K. Shaik1, H. Kolev, Z. Cherkezova-Zheleva

Sperrylite is one of the most abundant platinum minerals globally, valued for its economic importance but also known for its highly refractory nature, making it difficult to process via the conventional route. This study explores the oxidative leaching of sperrylite using a cyanide–ferricyanide system, with a key focus on characterisation of the mineral and surface speciation under varied leaching conditions using x-ray photoelectron spectroscopy. The parameters investigated include the effect of sodium cyanide concentration, the use of potassium ferricyanide as an oxidant, copper sulphate pentahydrate as a catalyst, as well as the effects of temperature and particle size. A limited set of leaching tests was carried out to study the surface chemistry rather than optimising dissolution conditions. This approach identified mineral oxidation states and shifts in binding energies, prior to and post leaching. XPS analysis of sperrylite’s surface chemistry identified key species, comprising the bulk Pt(II)–As (≈73 eV) and As(–I)–Pt (≈41.8 eV) states, together with surface oxidation products Pt(II)–O (≈72 eV), Pt(IV)–O (≈74.5 eV), As(III)–O (≈43 eV) and As(V)–O (44.5 eV). Leaching led to the removal of pre-existing oxides on the ultra-finely ground sample, exposing the underlying bulk species. In contrast, the crystalline sample with an initial low concentration of oxides, generated higher amounts of fully oxidised species after leaching, reflecting greater surface reactivity.

Mar 6, 2026

By B. McFadzean, M. Becker, S Geldenhuys, A. Molifie

Mineral hydration is known to result in low flotation recoveries and grades within primary platinum group element ores worldwide. This is because the phyllosilicate minerals derived from hydration reactions of silicate minerals (i) form electrostatic coatings on valuable minerals that in turn hinder collector adsorption, (ii) alter the viscosity of the slurry leading to poor gas dispersion and (iii) decrease the concentrate grade due to naturally-floating gangue. Sodium silicate was investigated because its dispersant, rheology modifying, and depressant properties could prove promising in combating the problems associated with these ore types. Quantitative evaluation by scanning electron microscopy analysis revealed large quantities of serpentine and talc present within the ore sample used in this study, which led to a poor flotation response as indicated by batch flotation tests. Using sodium silicate improved the recoveries and grades at high dosages (>1000 g/t). The zeta potential experiments indicate that improved recoveries are, in part, as a result of the reversal of serpentine surface charge, creating electrostatic repulsion between serpentine and valuable minerals which prevents the coating of valuable minerals by serpentine slimes. Ore dilution and rheology tests indicated that decreased viscosity at high dosages also improved recoveries. Talc micro-flotation tests revealed that the depression of talc occurred at higher sodium silicate dosages, which improved concentrate grade. The processing of nearsurface altered ores is becoming an increasing problem worldwide and the use of sodium silicate proved valuable in mitigating the problems associated with the altered ore investigated in this study. Keywords: Alteration, phyllosilicate slimes, colloidal chemistry

Jan 1, 2020

By B. P. Watson

The Bushveld platinum group metal deposits in South Africa are the largest in the world. These deposits occur as two distinct stratiform tabular ore bodies and strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2300 m. The mining method is a variation of planar open stoping. Crush pillars are widely used to support the open stopes. These pillars are designed to fail and the residual strength provides the required support resistance to stabilize the stoping excavations. This paper describes the in situ measurement, of stress within a Merensky pillar from Impala Platinum. These measurements were used to derive a stress-strain curve that includes pre and post failure behaviour. 2D FLAC modelling, with strain softening, was done to investigate how damage expands into the hanging- and/or footwall. Although the so-called ?squat? effect is always present, the modelling suggests that it does not dominate the pillar system behaviour at larger width to height ratios. Punching of the pillar into the hanging- and/or footwall increasingly controls the pillar system behaviour with larger width to height ratios. The paper investigates the behaviour of a system that incorporates the immediate hanging- and footwall, as well as the pillar itself.

Jan 1, 2009

Infacon 74 Members are reminded of the International Ferro-Alloys Congress that is to take place in Johannesburg between 22nd April and 1st May, 1974. The Congress is being held jointly by the National Institute for Metallurgy, the Ferro Alloy Producers' Association of South Africa, and the South African Institute of Mining and Metallurgy. Correspondence and enquiries should be addressed to The Secretary, Organizing Committee, INFACON 74, Private Bag 7, Auckland Park 2006. The gold deposits of the farms Lisbon and Berlyn in the Eastern Transvaal by v. c. H. R. BRERETON. Published in the Journal November 1973. AUTHOR'S CORRECTIONS The following amendments should be made.

Jan 2, 1974

By N. Morris

In South Africa, diamonds are mined predominantly in rural areas. Kimberlitic diamonds dominate in Limpopo and the Northern Cape Provinces whereas alluvial diamonds are mainly sourced from the North West and Northern Cape Provinces. There are a few large and medium sized diamond companies (De Beers, Petra Diamonds, Trans Hex, Rockwell and Alexkor). There are many smaller companies involved in diamond mining, mostly alluvial diamond mines. The nature of alluvial diamond deposits is that they are aerially more extensive and thus their surface impacts are more pervasive: The recent downturn in diamond prices has resulted in the sudden cessation of mining at many small and medium diamond operations. The South African Mining Charter requires all mines, including diamond mines, to subscribe' to .the following empowerment objectives:

Jan 1, 2010

By P. J. D. Lloyd, Jill Urban, M. R. Urban

The adsorption of gold from cyanide solutions onto constituents of the reef, and its role in reducing the efficiency of the gold-recovery process by M. R. URBAN. M.Sc. (Chem. Eng.) Rand (Visitor). JILL URBAN. B.Sc. (Chem. Eng.) Rand (Visitor) and P. J. D. LLOYD. Ph.D. (Cape Town) (Fellow) Evidence for the adsorption or re-precipitation of gold from cyanide solutions onto gangue minerals of the Witwatersrand reefs has been gathered over a number of years by various investigators. The evidence from tests using radioactive tracers is conclusive and indicates thlt adsorption contributes about 0,1 g/t to the total gold loss from conventional reduction works. The loss is a function of the alkalinity and cyanide concentration of the solution, and it appears to be affected by the extent of time between milling and cyanidation. The heavy minerals appear to be the strongest adsorbers, and the clay minerals somewhat less strong adsorbers. A sensitive qualitative test based on thin-layer chromatography permits the extent of adsorption and desorption to be readily determined.

By J. van der Walt, A. Whillier

Reference is made to the approach to mine cooling in which the service water is used as one of the means of distributing refrigeration, and attention is drawn to various engineering disciplines or functions necessary for effective distribution and reticulation of cold water from refrigeration plant. The demand for service water is intermittent, the peak flow-rates being typically two to three times the average flowrate. The refrigeration plant, on the other hand, must preferably be operated steadily throughout the day and night, with the result that a large storage dam for cold water must be incorporated into each system in order to even out the surge in demand for water. These dams should be operated as constant-temperature, variable-volume reservoirs. The conventional cascade system involving dams on each level is not the best for sending water down mines, and schemes are described that avoid the need for such dams. Reference is made to various tests that were carried out, and to several large systems that were installed. Management and organizational problems that could arise as a result of new technological developments in mine cooling are referred to, and cost figures are quoted to indicate the large potential savings, In addition to the improved environmental conditions, that can be achieved through the use of integrated water systems.

Jan 1, 1979

By G. Asbjörnsson, E. Hulthén, P. Papadopoulou, C. M. Evertsson

Crushing plant managers need to assess, manage, and communicate the environmental impact induced by their crushing plant operations as a step towards the sustainable development of the company. However, performing reliable environmental impact calculations of crushing plants can be challenging when the availability of operational and emission data is low, and when the company’s environmental expertise is not adapted and connected to plant operations (or does not currently exist). To address these challenges, this paper proposes a practical approach where the lifecycle assessment methodology (LCA) is combined with process simulations in a web-based tool. To describe what functionality such a tool should have to be incorporated into a company’s workflow, the system that surrounds a crushing plant is analysed. Further, a case study with a three-stage crushing plant is introduced to showcase how the simulated power draw results produced with the beta version of the tool can be compared to measured sensor data from the crushing plant for one operational day. The results indicate that the simulation tool can provide an adequate estimation of the specific energy for the different material fractions and give an overview of the environmental impact of the process caused by electricity and explosives consumption. Plant managers and operators can use this tool to calculate the environmental impacts of their plant and simulate how different operational strategies influence them. Keywords: LCA, environmental impact, coarse comminution, crushing plant

Jan 1, 2020

By T. Mahlangu Mahlangu, T. Fungene, K. C. Sole

"Although oxygen is widely employed as the oxidant of choice in gold leaching by cyanide, its low aqueous solubility presents some drawbacks in practical application; hydrogen peroxide has therefore been considered as a possible alternative. The aim of this investigation was to study the catalytic decomposition of hydrogen peroxide, which generates an oxidizing intermediate species, and to understand its effect on cyanide destruction. Operating conditions that facilitated the effective decomposition of hydrogen peroxide were established by varying the pH and catalyst type and concentration. The oxidizing intermediate, detected using an indirect technique, was found to be the hydroxyl radical (OH?). OH? is commonly generated in acidic solutions, but this work demonstrated that it is also produced at the alkaline pH values necessary for cyanide gold leaching. The effects of free and complexed iron and copper catalysts on the oxidation and consumption of hydrogen peroxide and cyanide were also investigated. It was shown that the cyano complexes of Fe(II) and Cu(I) are also effective as decomposition catalysts. Hydrogen peroxide concentrations above 0.01 M decreased the free cyanide concentration, which was attributed to the probable formation of the cyanate anion (CNO-). Although cyanide consumption increased due to its oxidation in the presence of OH?, excessive cyanide consumption in the presence of copper was attributed primarily to its complexation by the unstable copper(I) cyanide species. Rate constants for the decompositions of H2O2 and cyanide by ferrocyanide and copper cyanide were calculated; the latter was identified as being a better catalyst. IntroductionLeaching of gold from its ores using cyanide has been employed for well over a century (Habashi, 2016). Addition of cyanide converts the gold into a cyanide complex (Au(CN)2 -) that is soluble in water (Wang and Forssberg, 1990). The leaching reaction can be represented as Equation [1]:"

Dec 1, 2018

By L. E. Salinas-Farran, S. J. Neethling

Key variables in heap leaching include permeability, mechanical stability and mass transport. All of these properties can be manipulated by agglomerating and curing the ore before stacking it into heaps. The chemical and structural evolution of the agglomerates during curing is key to improving agglomerate properties and, ultimately, heap performance. It is possible to image the internal structure of agglomerates using SEM/EDX (e.g. QEMSCAN or MLA), although these methods are destructive and do not represent the 3D structure of the agglomerates. A non-destructive alternative is to image the agglomerates using X-ray Microtomography (XMT). Not only does this provide 3D information, it also allows the same samples to be repeatedly scanned, allowing the time evolution of the agglomerate structure and chemical composition to be tracked. In this paper we compared the behaviour of ores agglomerated using a combination of sulphuric acid and ferric sulphate with ones in which chloride ions are added to the recipe, since chloride leaching is gaining in popularity as a chemical alternative to bioleaching for sulphide ores. We tracked the curing process beyond the typical time scales to see the impact that this has on both the agglomerate structure and the subsequent leaching behaviour. Keywords: Heap leaching, curing extent impact, leaching kinetics, ferric-chloride leaching

Jan 1, 2020

By C. C. Pretorius, S. Ramjee, R. J. Mostert

The study investigates the effect of prior corrosive exposure on crack growth resistance behaviour of thin sheet (3 mm thick) aluminium alloy 2024-T3 at slow strain rates. Compact tension specimens were exposed to standard corrosive environments that simulate accelerated atmospheric corrosion attack. Two corrosive environments were considered – an exfoliation corrosion (EXCO) solution and a 3.5 wt% sodium chloride solution. The unloading compliance R-curves of the two-hour EXCO-exposed specimens revealed a significant degradation of approximately 11% in the crack growth resistance behaviour (Kc_e values) compared to the baseline (air-exposed) values. Furthermore, secondary intergranular crack formation was also revealed in the plastic zone ahead of, and adjacent to, the crack tip of these specimens; which formed during the crack growth resistance loading. It is postulated that the observed degradation of the Kc_e values of the EXCO-exposed material is due to hydrogen embrittlement since the exposure times for the EXCO evaluation were limited to ensure that uniform corrosion dominated; that is, significant penetration of corrosion damage and pitting due to localized corrosive attack did not occur. The sodium chloride-exposed specimens revealed a similar degradation (13%) after 24 hours exposure. However, slight intergranular corrosive attack and isolated pitting were observed on the exposed surfaces prior to crack growth resistance loading, resulting in notch effects that could assist in crack growth. Pitting and intergranular corrosion were, however, not observed at the pre-crack tip. The relative contributions of the notch effects and the hydrogen embrittlement during the degradation of the KR performance are, therefore, unclear.

Apr 1, 2021

Book reviews Fiftieth Annual Report (1971) of the Safety in Mines Research Establishment, published by H. M. Stationery Office, London on behalf of the Department of Trade and Industry. Advances in extractive metallurgy and refining. This excellent volume, published by the Institution of Mining and Metallurgy, contains all the thirty papers presented at the International Symposium held in London in October, 1971. Electric Melting Practice by A. G. E. Robiette, Charles Griffin and Co. 412 pp. In recent years the application of electric furnaces to melting processes has expanded to such an extent that it has become a topic in its own right, quite distinct from the related subject of electric smelting which is still limited, for the most part, to those areas where inexpensive electrical power is available. Optimum use of manpower by A. J. van Zyl. The sixties represented one of the longest periods of sustained economic growth South Africa has experienced. At the same time it caused a certain amount of inflation and an acute manpower shortage.