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By R. N. Gow

EH-pH diagrams are useful tools in understanding how mineral surfaces react in solution and particularly how aqueous conditions can be changed to enhance mineral leaching processes. However, successful application of these diagrams requires several things be kept in mind to prevent what others have termed ?gross errors? in their calculation and use. The aqueous Cu-S system is used as the basis for explaining the mass-balanced method of calculating EH-pH diagrams with the thermodynamic equilibrium software, STABCAL. This includes a breakdown of the Gibbs? Phase Rule and how it is employed in STABCAL to modify the diagrams. This methodology was then applied to the aqueous Cu-As-S system and resulting diagrams are compared against examples of those generated using the predominant-ion method. The resulting mass-balanced diagram for enargite (Cu3AsS4) is noted to compare well with spectroelectrochemical measurements using Raman spectroscopy and cyclic voltammetry.

Feb 23, 2014

By G. T. Vandel

Dado el alza de precios en los metales, y la baja del "mining out", se busca una permanente mejora del método de beneficio aplicados a los minerales, a través del uso de la microscopia, como sistema alternativo y actual. Por tal motivo, el propósito del presente estudio refiere un panorama de los análisis microscópicos usados como rutina, así como de otros métodos empleados para llevar a cabo los estudios especiales. Siendo las investigaciones microscópicas de minerales y de los productos de la concentración, las que se constituyen como uno de los medios más disponibles para llegar a este perfeccionamiento, además de servir en los controles de rutina de algunos procesos usuales. En consecuenca, el uso de la microscopía permite ahorrar tiempo en las investigaciones de los minerales en plantas pilotos y reduce los problemas de dichos beneficios, presentados a las minas y concentradoras de la Cerro de Pasco Corporation.

Jul 20, 1956

By Niels Verbaan

NioCorp is developing the niobium/scandium/titanium Elk Creek carbonatite deposit. The probable reserve announced by the company in 2017 indicated significant niobium (0.79% Nb2O5), titanium (2.81% TiO2), and scandium (71 g/t), and is composed predominantly of calcite, dolomite, and ankerite. Niobium is mostly (80%) contained in pyrochlore with the balance in various Fe-Nb-Ti oxides, which also host most of the titanium. Scandium is primarily deported in dolomite, with lesser quantities in pyrochlore and biotite. The process flowsheet recovers separate niobium, titanium, and scandium products. Scandium is extracted from whole ore hydrochloric acid leach solutions using solvent extraction and is further refined through a re-leach and precipitation process. Scandium leach residues are treated in a sulphuric acid sulphation process to recover separate niobium and titanium precipitates as well as to solubilize the remaining scandium. Both hydrochloric acid and sulphuric acid reagents are recycled within the flowsheet. This paper will discuss key bench and pilot test results of the niobium extraction and recovery circuits and will present a conceptual flowsheet developed by the project team for NioCorp at SGS Minerals.

By G. L. Peralta

Geothermal energy is an important source of power in more than 12 countries and is a potential source in 50 countries. However, the exploration and use of geothermal resources generate residues such as scale and sludge. The scale is from the steam distribution pipes while the sludge is from cooling ponds. These solids contain significant levels of elements which are of environmental importance notably, arsenic, sulfur, copper, zinc and lead that require safe treatment and disposal. The compositions, phases, textures, morphologies and size of scale and sludge particles have been studied by laser particle size analysis, light microscopy, scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. In addition, their leachability was tested with protocol leaching procedures and sequential extractions. The detailed spatial relationships and speciation of the environmentally significant constituents have received particular emphasis. The information obtained is useful in understanding how the scale and sludge are formed, their leaching behavior if disposed of in a landfill and in developing appropriate treatment strategies.

Jan 1, 1994

By W. E. MacDonald

This paper relates the story of 100 years of mining in the Harbour Seam at the Princess Colliery, Sydney Mines, Nova Scotia. Several interesting anecdotes are included along with the discussion of the evolution of coal mining methods in the area. Finally, some of the recently introduced equipment at Princess Colliery is described, and prospects for the future of the industry are outlined.

Jan 1, 1968

By J. B. Mawdsley

A LITILE north of the geographic centre of the Province of Saskatchewan, 150 miles north of the city of Prince Albert, is a narrow green-stone and sedimentary belt of pronounced structural characteristics. This belt, generally known as the Sulphide Lake belt, is about two and a half miles wide. During the past three years prospecting has uncovered numerous gold-bearing showings occurring chiefly along the centre of the belt for a distance of at least nine miles. The number of these showings, the nature of some of them, and their relationship to strong structural features, make it altogether likely that intensive work will eventually locate ore-bodies that will be of economic importance. The discovery of gold in the fall of 1938 on the south shore of Mackay lake, about five miles northwest of the Sulphide Lake gold-bearing belt, indicates that there are neighbouring zones of interest. This paper, an attempt to outline the present status of the interesting mineralized belt, is based largely on the information gained on a five-day tour of this district, made in August, 1939, on behalf of the Department of Natural Resources of the Province of Saskatchewan. The Sulphide Lake belt is named after a small lake centrally located in it. This lake and others are just north and within short portage distances of some of the long bays along the north shore of Lac La-Ronge, an irregular, island-studded lake, about twenty miles in diameter, in relatively rocky Precambrian country, just north of the Palaeozoic contact. The fur-trading post and settlement of Lac La-Ronge is on the west shore of this lake and a road, now under construction, will shortly link this community with the city of Prince Albert. In the past, the most direct route was an indifferent canoe route, in part following Montreal lake and river; more recently, the aeroplane has made this section easily accessible.

Jan 1, 1940

By Hatch, A. Reple, W Valery

The mining industry is facing declining feed grades which require the mining and processing of larger volumes of material per tonne of product. Pre-concentration aims to remove barren material at as coarse a particle size and as early in the process as possible to reduce processing costs, energy consumption, water losses, and greenhouse gas emissions while increasing production and profitability. This may be achieved using bulk ore sorting—the separation of barren gangue from a fully loaded conveyor belt based on the grade as measured or inferred from a sensor. This paper evaluates the technical and economic viability of bulk ore sorting for the PanAust Phu Kham copper deposit in Lao PDR. Bulk ore sorting technology is described briefly along with discussion of appropriate sensor and diversion systems for the Phu Kham operation. To evaluate the economic implications, the actual mined material and costs from 2014 were used as the base-case. Sampling data was not available; therefore, the ore grade variability that would feed a bulk ore sorter was estimated using geo-statistical tools based on mine grade control data. The sorter performance when treating this material was simulated considering the accuracy of the sensor measurement and errors associated with material diversion. The impact on inferred cash flow was estimated for several different scenarios considering the additional costs for sorter operation and reject handling. The evaluation demonstrated that bulk ore sorting at Phu Kham has the potential to increase the amount of metal in product and/or reduce processing plant throughput (and costs) to improve the annual inferred cash flow for the conditions investigated. The sorter is the gatekeeper – only material above the cut-off grade (value-adding) reports to the processing plant; no waste dilutes the feed. Likewise, above cutoff grade material is not lost to waste; preventing lost revenue.

Jan 1, 2016

By A. M. L. Cushing, S. Kelebek

Presently, adsorption is one of the effective methods of removing toxic contaminants from waste waters. The contaminants from metal mining industrial operations include an effluent water containing various types of heavy metal species at concentrations beyond the maximum allowable limits, which are 0.5 ppm and 0.3 ppm for nickel and copper species, respectively. Adsorption behavior of copper ions pre-chelated with diethylenetriamine (DETA) and triethylenetetramine (TETA) onto natural bentonite and peat has been investigated. Both natural bentonite and peat was found to be capable of removing these copper-polyamine complexes from aqueous solutions relevant to process water effluents. However, the adsorption capacity of bentonite was significantly higher than that of peat. Two models were used to study the adsorption kinetics: a pseudo-first-order rate expression and a pseudo-second-order rate expression. For both adsorbents, the data conformed best to the pseudo-second-order rate expression. Representation of the experimental data through adsorption models was also investigated. Out of the four cases considered, namely, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms, it was found that for both bentonite and peat, the copper polyamine adsorption data conformed best to the Dubinin-Radushkevich adsorption model. The Langmuir model also represents the bentonite-copper polyamine adsorption system reasonably well as the second best case, suggesting that the amount adsorbed on bentonite might be a monolayer with strong affinity.

Jan 1, 2015

By J. D. Little

"THE SALMO PROPERTIES of Canadian Exploration, Limited comprise forty-one Crown-granted mineral claims situated on Iron mountain between Sheep creek (on the north) and Lost creek, some eight miles southward from Salmo, in the Nelson mining division (see Figure 1). On these claims there are at present four operating mines. These are, from north to south, the Dodger, Feeney, and Emerald, all tungsten mines, and the Jersey, a lead-zinc mine, about 7,000 feet south of the Dodger. About midway between the Dodger and the Jersey is a fifth mine, the Emerald lead-zinc mine, which was the first producer in the area but has been inactive since 1926. The locations of the mines are shown in Figure 2.Records of prospecting and claim staking on Iron mountain -which owes its name to the presence of large iron-stained outcrops -go back to 1895. The first recorded owner of the claims that form the old Emerald lead-zinc mine was John Waldbeser who, in 1908, did considerable work and produced 426 tons of lead ore valued, at the then price of lead, at $7,000. This ore was chiefly lead carbonate and was taken from the surface outcrops of two bands of ore that form the Emerald orebodies. In 1909, the Emerald was the largest lead producer in the Nelson mining district."

Jan 1, 1953

By C. G. Anderson

The treatment of materials for the recovery of the precious metals imposes many processing and environmental challenges. Sunshine Mining and Refining Company has developed hydrometallurgical technology for recovery of values from refractory precious metal materials. At Sunshine, the industrial focus of these processes has been for the direct recovery of silver without cyanidation. However, recent work has indicated that these technologies can provide a means for treating complex, refractory gold concentrates. This will be the focus of this paper. The practice of pretreating ores and concentrates to make them more amenable to cyanidation is becoming more common. Several pretreatment options for sulfide concentrates containing gold include roasting, bio-leaching, direct pressure oxidation and nitrogen species catalyzed pressure oxidation. The industrial use of nitrogen species catalyzed pressure oxidation has been limited to the Sunshine refinery where its focus has been for the treatment of silver concentrates. Much of the reluctance, outside of Sunshine, to use this type of technology may be based on the perception that high costs are associated with using nitrogen species (e.g. nitric acid, sodium nitrite) to leach. Also, the use of nitrogen species catalyzed pressure oxidation on an industrial scale is unfamiliar to most metallurgical professionals. A summary of pressure leaching processes which utilize nitrogen species as a catalyst is presented in Tables 1 and 2.

Jan 1, 1996

By J. M. Bowen, P. Wemyss

"Gold losses to natural carbonaceous matter during cyanide leaching have been investigated for over a century. The variation in the severity of the problem from one ore to another has led to a range of different processes being implemented at different mine sites. Most commercial options utilise one or more of the following processes: roasting, carbon pre-flotation, organic blinding, CIL, chlorine passivation, pressure oxidation, biological passivation, elevated temperature CIL, RIL and thiosulfate. This paper provides a background to identify the most appropriate process or combination of processes for a particular ore. It also presents information on how these processes may be implemented, drawing on information in the literature and from current or recent applications at operations such as the following: Stawell, Kumtor, Penjom, Twin Creeks, Macraes Flat, Kittilä, Fosterville, Inata, Carlin, Goldstrike, and Jerritt Canyon. Various process options have been dismissed, or deemed unsuccessful due to limited knowledge available on the strengths and weaknesses of the different options and their implementation. The authors have collectively been involved in flowsheet development and project implementation in four commercial plants that have treated preg-robbing ores.INTRODUCTION Cyanide processing has been the mainstay of gold recovery for well over a century. It is generally a very effective process with over 90% recovery on free milling ores, but complex and refractory ores may only give 0–50% recovery with conventional processing (La Brooy et al., 1994). People have written about gold losses to natural carbonaceous matter during cyanidation for over a century e.g. Feldtmann, (1915). The earliest reports related to African operations, but the issue has since been reported in Canada, North and South America, Australia, Russia and China. The phenomenon is usually referred to as ‘preg-robbing’ dating from the times before the use of granular activated carbon for gold recovery, when gold was lost from the pregnant solution before it could be separated from the leach solids and recovered by cementation. Many excellent reviews have been published e.g. Dunn et al. (2013), summarising the options considered and where they have been applied commercially."

Jan 1, 2017

By R. S. Fowkes

Jetstream pressure distributions and coal cutting rates were determined for a number of nozzles and under different operating conditions. The jetstrearn pressure distribution data were fitted to an assumed curvilinear equation by the utilization of a numerical least-squares technique with the aid of a digital computer. Subsequent manipulation of the approximation equation showed that the total force of the jetstream, rather than its maximum pressure or total kinetic energy per unit Lime, was the most significant quantity affecting the coal cutting rate. A shorter method for assessing the ability of a nozzle to cut coal was found.

Jan 1, 1968

By M. Girard, E. Bourricaudy, M. Ashbury, M. Canizares, A. Mezei

Liquid-solid separation and slurry handleability relate directly to commercial plant ramp-up success or lack thereof. The paper provides a well-proven approach for testing, scale-up and commercial application of difficult processes. Emphasis is placed on practical applications of rheological concepts developed both academically and empirically. The cause-effect relationship between the process chemistry and possible physical implications on the metallurgical plant operability is presented in a simple, direct form. Examples include recent results in areas of mineral processing and extractive metallurgy. Technical process risk factors and their mitigation are included in the discussion.

Jan 1, 2011

By C Vejrazka

Northparkes is located 27 km north of the township of Parkes in central New South Wales, Australia. The operations consist of underground block cave mines and an ore processing plant that produces high-grade copper and gold concentrate. Production is currently sourced from the E48 Lift 1 block cave mine and open cut stockpiles. Mining commenced at Northparkes in 1994 as an open cut operation. Underground block cave mining began in 1997. Northparkes was the first mine in Australia to use the highly efficient block cave mining method, which relies on gravity and natural rock stresses to fragment the ore.The occurrence of air blasts is one of the principal mining hazards in block caving operations between the time of first undercutting and breakthrough of the cave to surface. As such, it needs to be managed continuously, and risk assessments need to be reviewed on a regular basis for applicability to changing conditions. Unfortunately, there is little literature on how to practically approach air blast risk assessments in a way that can be incorporated in the day-to-day operation of a mine. Previous methods of assessing air blast risk were tedious and results were often unrepeatable.With the extension of the E48 Lift 1 extraction level, it was necessary to assess the air blast risk for the extension drives and develop operational guidelines for production from the extension. A review of the methodology for assessing air blast risks revealed substantial improvement opportunities.This paper outlines the principles used for air blast risk assessments at Northparkes Mines and the methodology employed to achieve efficient, repeatable and auditable results.CITATION:Vejrazka, C, 2016. Northparkes Mines’ current air blast risk assessment practices for block caving operations, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 257–264 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By M. Ghiani

Biohydrometallurgy originated, some forty years ago, from an environmental problem, namely the serious pollution of the Ohio river by acid drainage water coming from neighboring subbituminous coal mines. Studies aimed at elucidating the cause of the intensive oxidation of the iron sulfide (pyrite) inclusions of those coals, led to the discovery of a bacterium, Thiobacillus ferrooxidans (Temple and Colmer, 1951), capable of acting as a catalyzer, accelerating the otherwise very slow chemical oxidation of iron sulfide to rates many orders of magnitude higher. However, it is now recognized that the biotechnology of microbial mining dates back to 1963, when the ability of this bacterium to solubilize copper from sulfide ores was ascertained (Razzell and Trussell, 1963). Much research has been carried out on biohydrometallurgy over these last 25 years and is still being actively conducted all over the world. The interdisciplinary nature of this young branch of science and technology is reflected by the variety of experts involved: microbiologists, mining engineers, hydrometallurgists, physico-chemists, mineralogists, solid-state physicists and biochemists. This intensive research effort has provided a solid background on the fundamentals of this technology, although many important issues have still to be solved, amongst which the enzymatic mechanisms controlling biocatalysis of mineral sulfides dissolution, the influence of bulk- and surface solid-state physics of metal sulfides on dissolution mechanisms, the interaction of the various strains composing natural microbial floras. Their elucidation should permit the rationalization of biohydrometallurgical techniques and the optimization of commercial processes. Biohydrometallurgy has already achieved satisfactory results: copper recovery from submarginal copper sulfide run-of-mine ores (i.e. assaying less than 0.3% Cu) by in-situ, dump and/or heap leaching is successfully practised in many countries and uranium recovery through bioleaching is competitive with other leaching processes.

Jan 1, 1987

By H. Huang, R. N. Gow

"The reactivity of an enargite mineral electrode was investigated spectroelectrochemically under conditions typically found in alkaline sulfide leach solutions, with pH 11-13 and Na2S additions of 50 and 250 gL-1. A bulk enargite electrode was cycled between 0 and -1,000 mV for each set of solution conditions. Raman spectroscopy was used to determine and compare surface formations against species in mass-balanced EH-pH diagrams generated using STABCAL. Previously, it was determined that arsenic could be selectively leached under alkaline conditions at an average solution potential of -300mV, across the pH range 11-13. Operating under such conditions allowed for the selective leaching of arsenic with elemental sulfur formation. From several of the voltammograms obtained during this current testing, the formation of elemental sulfur appeared at increasingly reducing conditions with increasing sulfide concentration. At high concentrations, copper started to dissolve, possibly as a bisulfide complex, reducing the selectivity of the leach, unlike previous studies. However, the presence of the higher sulfide concentration is also anticipated to prevent passivation by consuming any surface formation of elemental sulfur. This study provides insight into the operating parameters of alkaline sulfide leaching in regards to the selectivity of arsenic leaching, as well as guidance for control of reagents and solution potential and, of course, the need for water treatment afterwards.IntroductionEnvironmental limitations on the pyrometallurgical processing of arsenic-bearing concentrates have forced operations to consider other solutions. Attempts to hydrometallurgically process enargite (Cu3AsS4) fall into two categories: the co-dissolution of arsenic and copper under acidic conditions, and the selective leaching of arsenic under basic conditions. The authors believe that the selective leaching of arsenic is more amenable because it produces a solid copper phase, preferably chalcocite (Cu2S) or covellite (CuS) that could then be processed using conventional methods already in place in the copper and gold industries. Potential leaching methods include alkaline sulfide leaching (Achimovicovica et al., 1999; Anderson and Twidwell, 2008a,b; Tongamp et al., 2009 and 2010), hypochlorite leaching (Vinals et al., 2003; Curreli et al., 2005; Mihaljovic et al., 2007), ammoniacal leaching (Gajam and Raghavan, 1983), and acid leaching (Gow et al., 2014b) with or without fine grinding to mechanically activate the enargite surface and increase normally slow leach reaction kinetics (Achimovicova et al., 1999; Balaz et al., 2000; Balaz and Achimovicova, 2006). In this study, the reactivity of enargite under alkaline sulfide leach conditions was examined."

Jan 1, 2015

By G T. Jemwa, F Rousseau, F J. Wolfaardt, J A. M Rademan, P W. Smit

Mining companies are increasingly faced with the challenge of reducing operating costs while maximising throughput and profitability. At the same time, the grade and quality of treated ores are becoming poorer and more variable, resulting in suboptimal process performance.It is now widely accepted that strategies to drive operational goals must revolve around improving plant availability, reliability and process efficiency. In particular, progress in plant automation and control systems has seen a trend towards unified frameworks for control and optimisation of mineral processing plants. These frameworks seek to seamlessly integrate different roles and tasks involved in process operations - IT, automation, plant maintenance and operations. An integrated solution framework for reducing process variability, increasing process efficiencies and maximising plant availability and reliability is discussed within the context of a typical milling circuit. The framework exploits a real-time analysis ægapÆ evident in production operations that prevents timeous identification of equipment and process failures. This is achieved by leveraging predictive analytics for equipment health monitoring, control loop monitoring and advanced regulatory control solutions towards enhanced process performance, improved asset management and regulatory compliance. The framework provides for early and actionable warnings on equipment and process degradation using real-time operational data.Resolving these problems can potentially avoid unplanned downtimes, process instabilities and other operational surprises, thus ensuring optimal plant throughput and optimal process behaviour for improved recoveries. Integrating control systems and plant automation with advanced analytics to analyse and optimise processes enables operations to achieve reductions in the variability of key process parameters. In addition, early detection of equipment malfunction or suboptimal process conditions leads to improved equipment availability and reliability. Ultimately, these operational gains reflect in profitability because of plant throughput and recovery gains. These benefits are demonstrated using data from a South African gold mining operation, where such an integrated asset and process health monitoring framework for process optimisation has been implemented.CITATION:Jemwa, G T, Wolfaardt, F J, Smit, P W, Rademan, J A M and Rousseau, F, 2013. Towards an integrated framework for asset and process health monitoring and optimisation on a milling circuit, in Proceedings World Gold 2013, pp 137-148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By A. Bouajila1

Minerals processing organisations will be more and more under intense competitive pressure. Major changes are being experienced with intense respect to resources, processes, production strategies and markets. As result of international competition, only the most productive and cost-effective operations will survive. That is why operators in the minerals industry have always aimed to obtain better performance from their processes along the mineral extraction cycle starting from exploration up to the smelting step if any. A principal ingredient and perhaps the most important one in the process of evolution toward improved productivity is the achievement and implementation of an error-free production synonym of an ignorance-free operation. This is, at the same time, a guarantee for quality, a minimising factor for waste materials production, handling and disposal, and a maximising factor for labour utilisation. The notion of ?error or ignorance-free? -usually identified as a ?made in Japan? manufacturing mythology, will sound, at first impression, like a pious ideal, to be striven for but impossible to attain. Nevertheless, the introduction of measurement and detection technology in the minerals industry along the last century should benefit from the today?s sensors and control systems that explosively expanded beyond their traditional production base into far-ranging commercial ventures. The fastness and spread of those technologies will play an important role in the survival of innovative plants. Their role in information assimilation, and control of operations to maintain an error-free production environment, will help many plants to stay effective on their competitive course. In this paper the feasibility of the zero process ignorance concept as applied to the comminution circuits will be discussed and the challenge behind this ambitious move toward improved productivity will be outlined. Examples of pre-competitive R&D projects started at COREM in order to fulfil this prerogative will be presented.

May 1, 2001

During a period of six months in FY2018, a series of trials were conducted to compare drilling accuracy using two different methodologies and the subsequent impact this had on ore dilution. Testing was conducted at Cracow underground gold mine in Queensland, Australia. The drill rig’s existing alignment process was compared to a new technology system with the following observations: - Using the existing alignment process only 20% of holes surveyed recorded toe points within the +/-300mm (11.8in) tolerance blast-hole deviation. - The new technology was proven to limit rig alignment error, reducing average blast-hole deviation and increasing the number of holes drilled within tolerance by 160%. The increased accuracy reduced stope dilution by reducing over-break of subgrade ore: - Stopes drilled using the new technology recorded 62.6% less average dilution. - This contributed to an overall reduction in dilution for the full year (FY18) of 5 percentage points compared to FY17 - from 22% to 17% (a net decrease of 22.7%). A cost-benefit analysis extrapolated from the trials stipulates that if the new technology were in use for a full 12 months, when applied to FY17 full year data, a 10 percentage point reduction in dilution would represent a net 45.4% decrease, and would result in AUD8.2M (USD5.9) additional ore recovered, with AUD4.5M (USD3.2M) less spent on wasted cost of haulage and processing of diluted ore. As a result, return per tonne would increase 22%, from AUD87 (USD63) to AUD106 (USD77.1). INTRODUCTION Dilution – planned and unplanned – remains a significant cost impairment in the mining process. A series of trials were held over a six-month period in FY18 which established the cost-benefit of new technology as it applies to the alignment accuracy of production drilling rigs in underground mining, thus confirming its ability to limit drilling as one of the causes of dilution. The trials identified three underlying factors affecting drilling accuracy, measurable by blast-hole deviation surveys of planned vs actual toe data. These were; rig alignment error, collar location change/error, and in-hole deviation. The trials involved a comparison of existing rig setup processes and technology, with the new technology (Minnovare’s Production Optimiser system). The trials were undertaken in the same environment; an operating underground gold mine - Cracow Gold Mine. The comparison first revealed the extent to which rig alignment impacts blast-hole deviation. Secondly, the new technology was proven to limit rig alignment error, thereby reducing average blast-hole deviation and increasing the number of holes drilled within tolerance by 160%.

Jan 1, 2019

Sphalerite is commonly floated in an alkaline environment and under such conditions the overall activation mechanism is obscured by the hydrolysis of Cu2+ and precipitation of Cu(OH)2. Electrokinetic and kinetic flotation tests show that the activation of sphalerite is a two-stage process; the activation products formed on the surface of sphalerite in near neutral and in alkaline solutions in the first rapid activation stage are "flotation-inactive". These layers, when formed in an alkaline solution, are unstable and are transformed into the "flotation-active" form in the second stage. However, the surface layers formed during activation in alkaline environment by copper in the presence of lead ions are very stable and even after a long conditioning time the flotation rate is not improved. Consequently, while both Cu2+ and Pb2+ activate sphalerite flotation, quite unpredictable effects may result when both are present in the solution.

Jan 1, 1997