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By E. Guerrini, M. Maccagni, J. Nielsen

"Lead is the most important material able to meet the current demand for energy storage. The lead acid battery is reliable, efficient and inexpensive. Continuous developments in battery construction are providing improvements in all aspects of the batteries’ performance. The lead acid battery is both the main lead product and the main raw material for lead production. More than half of the lead produced is from secondary smelters where batteries are the most important feed material. The environmental pressure on lead production has been increasing for many years, and continues to become stronger and stronger. The lead production processes and technologies themselves will require updating to meet the new regulations. Although they are very strict now, they will become even more so and current technologies may not be sufficient. Because recyclability is a strong point for the lead acid battery, the secondary smelters need to reduce the environmental impact as much as possible. In recent years, the secondary smelters underwent impressive changes in this direction, but some more improvements are possible. Electrochemistry can offer a step change improvement in making secondary lead production more environmentally friendly. Engitec has developed an electrochemical process base on a very high current density (high productivity) cell using an inexpensive electrolyte and at a relatively low cost. In this paper, the latest update on the technology is provided. INTRODUCTION The lead acid battery is considered the “walking dead” by some new technologies trying to replace it. It has played and will continue to play a very important role in our lives because it is inexpensive, fully recyclable and the existing lead and the mine reserves guaranty enough material for the extended future. According to the life cycle, the lead acid battery is the cheapest and the most effective system to store energy. Lead is practically a close loop where lead battery production consumes more than 80 % of the produced lead but contemporarily it is the most important raw material for the production of metallic lead. In fact, nowadays, the secondary production has overcome primary production and this trend is expected to continue. Primary lead is the make-up material for the existing battery production and the source of lead for the construction of the new ones."

Jan 1, 2018

By Osvaldo A. Bascur, J. Pat Kennedy

"The profitability of mining and metallurgical operations continues to lag behind that of other industries despite the technical advances that have occurred in recent years. A primary reason for poor performing in this economic sector is the lack of integration of mining and metallurgical information. The mine cut-off grade can be optimized if mining and metallurgical engineers have the data to optimize milling for the type of ore in hand.Integration of mine transactions, stockpile inventories, process flows and assays is the key to determining the economics for each blast strategy in a mining site. Real-time information from manufacturing assets greatly affects the profitability and flexibility of a company, but gross errors from faulty sensors, inaccurate instrument calibration, or incorrect process models may corrupt actionable information. New software tools can model the process, sift through available data to identify and eliminate gross errors, and use statistical data reconciliation to create materially balanced and consistent readings. The reconciled data is unified for use by both monitoring and decision making processes.Creating a real-time information environment where upgrade and change are allowed is becoming an accepted methodology to accelerate and simplify the integration of applications such as production monitoring, equipment performance management and yield and inventory management.This paper describes the data integration requirements in a mine, concentrator and port for unification of the redundant data. The capture of the mining events, stock pile management and the metallurgical information is the base requirements for a dynamic environment to reduce the overwhelming amount of information to unified set of information. Part of any decision support program should entail these results to continuously improve the measurement system to address the costs in mine and milling the ore."

Jan 1, 2003

By F. L. Mentg

The utilization of acid leaching tailings was studied. It is obvious that the Fe in acid leaching tailings can be leached into solutions as Fe2+. In this paper, the influence of conditions, including the concentration of ferrous sulfate, pH, temperature and velocity of air flow was investigated. The optimum conditions for preparing seed crystal are as follows: the concentration of ferrous sulfate is 20 g/L; pH is 9.5~10; reaction temperature is 10~20?; velocity of air flow is 0.4m3/h. The optimum conditions for preparing iron oxide red are as follows: the concentration of ferrous sulfate is 5 g/L; reaction temperature is 80~85?; velocity of air flow is 0.13m3/h. At last, the product of iron oxide red could be prepared by ammonia method.

Jan 1, 2014

There is a strong demand for nickel metal due to quick development of stainless steel and new electrical materials, most of which is extracted from sulfide resources, resulting in a serious depletion of sulfide resources. Therefore, more attentions have been paying to extracting nickel from nickel laterite, which accounts for some 50% of total nickel metal production. In this paper prereducing?magnetic separation?reduction smelting process is developed to manufacture ferronickel rom two types of nickel laterite DN and GN, assaying 1.42% 1.83% Ni and 49.09% 26.08%Fetotal, respectively. Mineralogy of two types of nickel laterite was determined and optimization of process parameters was conducted to manufacture ferronickel. Prereduction?magnetic concentration process is used to upgrade low grade nickel laterite firstly, two kinds of Ni-Fe concentrates being prepared of DN assaying 2.26% Ni and 69.45% Fetotal and GN containing 2.76% Ni and 38.00% Fetotal. Finally, two types of ferronickel were produced by reduction smelting of prereduced concentrates DN and GN, DN and GN ferronickel contains 2.97% Ni and 6.58%Ni, 89.25%Fetotal and 89.95%Fetotal, respectively. The total recoveries of Ni and Fe of the two ferronickel are beyond 90% and 80%, respectively. There is significant difference in grade of magnetic concentrates and ferronickel between DN and GN laterite due to their different mineralogy, the former belongs to limonitic laterite and the latter saponite one. There are some advantages for this process to manufacture ferronickel from nickel laterite, including effectively upgrading low grade nickel laterite by prereducing?magnetic separation technique, higher throughput and lower energy available for reduction smelting section due to some 40% gangue being rejected in pre-upgrading section, and much less metallurgical coke consumption by using non-coking coal as reductant for prereducing?magnetic separation?smelting process.

Jan 1, 2014

By Chris Plackowski, Bruckard. Warren J., Anh V. Nguyen

"Enargite is a significant penalty mineral in the copper industry and its separation from many copper sulfides by flotation is difficult. The separation may be crudely achieved using selective oxidation techniques or through the use of pulp potential control. This paper summarizes our latest contributions to a better understanding of enargite surface electrochemistry and hydrophobicity. Oxidation, roughness, hydrophobicity and species formation on the surface of natural enargite were examined by a novel experimental approach that combines electrochemical techniques, atomic force microscopy, X-ray photoelectron spectroscopy and droplet evaporation tensiometry. It allows for synchronized electrochemical control and examination of the oxidative surface morphology, speciation and hydrophobicity of enargite at pH 4 and pH 10. At low pH, surface layer formations consisting of metal deficient sulfide and elemental sulfur were identified associated with a limited increase in roughness and heterogeneous distribution of surface species produced by initial rapid dissolution of Cu, followed by diffusion limited surface layer deposition. At high pH, a similar diffusive mechanism associated with oxidation products consisting of copper sulfate and hydroxide and a significant increase in surface roughness were established. Receding contact angle measurements showed no significant difference in the contact angle on a surface oxidized at pH 10 and the freshly polished surface. Contact angle increased from 46° on the polished surface to 59° after oxidation at pH 4. Competing effects of hydrophilic copper oxides and hydroxides, and hydrophobic species of elemental sulfur on the mineral surfaces under oxidizing conditions at pH 4, and the change in surface roughness at pH 10, contribute to the changes in enargite hydrophobicity under electrochemically-controlled oxidation conditions. Most likely, both surface species and surface roughness produced by oxidation are critical to the changes in the wettability of enargite and other sulfide minerals."

Jan 1, 2014

By J. Kolacz

A new optical sorting system based on a complex image analysis and high definition imaging has been developed by Comex. The image analysis is based on high definition cameras of different types and advanced filtration tools for verification of waste particles. Different mineral properties are used to identify the processed material. The system is further combined with a high speed rejection mechanism based on FPGA technology and operating in real time conditions. This provides a minimal error when removing waste particles from the sorted material.

Jan 1, 2014

By Per Svedensten

One of the most significant behaviour of a crushing plant is the constant variation in the process. The variation is caused by two major effects. The first and constantly changing is the rock material properties. During operation rock material with different strength and particle size distribution is fed to the plant which makes the performance of the equipment to vary. The second and more slowly changing variation is caused by wear on the processing equipment. These effects must be predicted in order to be able to optimise a crushing plant. This paper demonstrates how Monte Carlo simulation can be utilised to study and operate crush-ing plants. By introducing Monte Carlo simulation the varying process can be study and also optimised. To maintain the optimised process performance supervision is needed. This paper demonstrates how results from the Monte Carlo simulation can be utilised for process supervision. Charts for process measurements can for example be derived. These can then be used to guide decision making and understand how the variation and performance of the plant changes over time.

Jan 1, 2014

By M. K. Aydogan

Today, arsenic has become a much greater problem than before because of the limitations introduced by WHO and USEPA that are lowered from 0.05 ppm to 0.01 ppm. In the nature Arsenic is mostly found as inorganic compounds in the forms of arsenite (As+3) and arsenate (As+5) in aqueous solutions. Arsenic contamination in ground and surface waters has been encountered in almost every country. This element has a carcinogenic effect and can occur in natural sources and anthropogenic sources such as metal mining, groundwater usage and industrial activities. In this study adsorbing colloid flotation was applied in the presence of aluminum sulfates. In the experiments SDS and K-Oleate were used as collectors while MIBC was the frother employed. The effects of collectors and aluminum/arsenic ratios on the removal of arsenic were examined under various pH values. It was found that arsenic removal enhanced with increasing aluminum concentration. Furthermore, it was observed that pH was a very critical parameter in all experiments. The best results were obtained when initial As: SDS: Al concentrations were 10:40:40 ppm at pH 5.5. At this concentration, the efficiency of arsenic removal found to be 99.9%. Keywords: arsenic, adsorbing colloid flotation, aluminum sulfate

Sep 1, 2012

By L. Simpson

South African is a repository of significant deposits of a variety of minerals. The Citigroup confirms this assertion with an estimate of in-situ valuation of US$2.5 Trillion. The mining sector plays an important role in the South African economy. In addition to the mineral resource base South Africa has other comparative advantages. Firstly, South Africa retains major mining companies that participate globally, including Anglo American, Goldfields and De Beers. Their global involvement offers much to the local mining sector and the broader economy. Secondly, government established research councils. The Council for Geoscience (CGS) was established to manage the Geological Survey of South Africa, including the reduction of geo-scientific investment risk. The Council for Scientific and Industrial Research (CSIR) promotes industrial development, including mining technology development. Mintek undertakes mineral research from mineral examination of ores, to extraction and refining technologies and manufacture of end products. Thirdly, South African universities teach and conduct research along the mineral value chain. They have increased their minerals graduates? capacity, thus advancing knowledge and skills. Knowledge and technical progress are behind productivity growth and emergence of competitive advantage. The research and development (R&D) capabilities of industry, science councils and universities, working in unison, will enhance the competitiveness of the South African mining industry. The National System of Innovation (NSI) requires multi-disciplinary, collaborative research. Key R&D elements, including skills and expertise, funding and facilities, must be available to implement a long-term national strategy or programme. Improved international collaboration and partnerships between government, academia and industry driven human resource development (HRD), ultimately develop the critical mass for inter-generational skills requirements. This trend requires an expansion of research collaboration programmes. Decisions involving investments and collaborative actions pertaining to R&D in the sector necessitate an analysis of the South African mineral value chain R&D capability. This paper analyses the evolution of R&D capability from exploration to refining, tertiary education, science councils and industry. The political economy of the evolution of this capability is analyzed in relation to the central role that the South African government plays in creating an appropriate supporting environment and related initiatives to enhance R&D and innovation. Keywords: research and development (R&D), science councils, universities, industry, innovation policy, South Africa

Sep 1, 2012

By I. N. Gridasov, T. V. Ignatova, E. V. Shelepov

"Mikhailovskoye Deposit is comprised of oxidized ferruginous quartzites among other minerals with the former widely spread across the ore field and mined along with unoxidized ferruginous quartzites. PJSC Mikhailovsky GOK strategic development is aimed at iron ore product output expansion. The most critical item of the strategic development road map is process design for separation and concentration of hematite contained in oxidized ferruginous quartzites mined as the by-product in the open pit. Laboratory and semi-industrial tests run to design cost-effective, reliable and environmentally friendly process for Mikhailovskoye deposit oxide quartzites processing included the following processes: - pilot tests of reverse anionic flotation which produced concentrate with Fe60.1-62.9% total iron content and 66-69%Fe recovery rate; - combined magnetic separation and flotation (Marubeni Company, 1982) including slime removal, reverse anionic and cationic flotation and high gradient magnetic separation resulting in 48.9% yield, Fe55-57.5%, up to Fe60.5% hematite concentration ( Fe64.1% being the best result achieved),76.2% recovery. - magnetic separation and flotation, including separation in low gradient (1400 Oe) and high gradient (up to 17000-18000 Oe) magnetic field. The results of these pilots tests were the following: 57-59%Fe concentrate, 70%Fe recovery (Mekhanobrchermet, MGOK, 1982-1988): - magnetic roasting in pilot plant of TSGOK (Krivoy Rog) which produced 61.1%Fe concentrate with 81.5% recovery. Major disadvantage of the method is high generation of dust equal to 20% of the initial feed. Based on third-party studies flotation of oxidized ferruginous quartzites process embracing best processing methods was designed by Metalloinvest Management Company LLC and PJSC Mikhailovsky GOK engineers. This paper discusses analysis of studies aimed at intensification of separation processes with application of mechanical slurry agitation (MSA), addition of alkali (NaOH) and elutriation of initial feed. The paper also provides a design solution to implement a lab-scale MSA plant. It includes feasibility evaluation of MSA inclusion in flotation of oxidized ferruginous quartzites process to enable higher yield and hematite recovery in resultant concentrate. Outcomes of the discussed work have significant value for prospective engineering of OFQ concentration process."

Jan 1, 2018

By X. L. Song

A large amount of tailings in concentrators bring a series of problems to the environment and society. It is significant to reclaim the huge tailings and reuse them in industries in order to utilize mineral resources adequately. Primarily Lead-Zinc tailings with a certain quality of clay and feldspar were used to produce ceramic tiles by sintering method under specific technical conditions. By testing the properties of the ceramic tiles, it was shown that the amount of Lead-Zinc tailing used in the tiles was 60%~70%, and the mechanics properties were good. The optimum proportion parameters were Lead-Zinc tailing 60%, clay 35%, feldspar 5%, and the maximum flexural strength of tiles was up to 38.2MPa when it was sintered at 1090? for 30min. Its flexural strength, water absorption and thermal shock resistance reached the State Standard of GB/T4100.4. The product is suitable to be used in pavements and paths of parks.

Jan 1, 2014

By T. V. Vijaya Kumar

Most of the iron ore washing plants set up in India consist of sizing of the ore by dry / wet screening, washing and classification by screw classifiers followed by multi-stage hydrocycloning of screw classifiers? overflow. The underflow of the hydrocyclones forms the concentrate which is used for pellets making. As the cut-point of hydrocyclones is generally at 20 microns, relatively lower diameter cyclones in a cluster with parallel feeding are used. This is found to, often, result in choking of the spigots, at times, by extraneous material as well reporting along with the slurry. It is observed to lead to sub-optimum performance of the cyclones with loss of iron values into cyclone overflow and thereafter into tailings. Analysis of data of an operating beneficiation plant (Beneficiation Plant - 1, BP - 1) of M/s Jindal South West (JSW) Steel Limited, Karnataka, India over a period of one year indicated that weight recovery of the concentrate from two-stage hydrocycloning was 45% (with respect to feed to the cyclones) and assaying 63.43% Fe, 4.43% SiO2 and 2.32% Al2O3. CSIR - National Metallurgical Laboratory - Madras Centre (NML - MC), India developed flotation process for processing screw classifier overflow with a view to improve the recovery of ultrafine iron values from it. Detailed investigations at laboratory scale flotation column and on-site pilot plant trials proved that the production of the concentrate and productivity of the plant could be enhanced by adopting reverse cationic column flotation technology. It was established that a typical screw classifier overflow analyzing 60.54% Fe, 5.95% SiO2 and 3.67% Al2O3 could be upgraded to 64.21% Fe, 2.64% SiO2 and 2.20% Al2O3 with 82.7% weight and 84.7% Fe recovery. This translates into an increase of 80% in weight recovery of the concentrate compared to what is being obtained, at present, by two-stage cycloning. It had an added advantage of reduced SiO2 in the concentrate. Thus, SiO2 in the final concentrate could be reduced to 2.64% from 4.43% by adopting column flotation. The concentrate so generated meets the stringent specifications, especially in terms of alumina in it(should be less than 2.50%) for pellets making. Later, JSW Steel Limited set up the flotation plant in BP - 1 based on the process developed by NML - MC and was commissioned in 2010. Keywords: iron ore, washing, ultra fines, alumina reduction, column flotation

Sep 1, 2012

By S. Serranti

The recycling of end-of-life concrete into new concrete is one of the most interesting options for reducing worldwide natural resources use and emissions associated with the building materials sector. The possibility to realize a larger re-use of silica aggregates from old concrete, strongly contributes to reduce environmental impact (reduced exploitation of natural resources, reduction of CO2 emissions, airborne dust production, etc.).To reach this goal, innovative processing techniques, as well as innovative sensing units and architectures have to be developed. In this perspective an analytical approach, based on hyperspectral sensing techniques, is proposed, discussed and critically evaluated in order to perform an automatic quality control assessment, finalized to maintain a high standard of concrete demolition waste, from the earliest stage of recycling to the further processing stages, according to the detected in-situ demolition waste characteristics. The paper deals with the analysis and the evaluation of the problems related to the integration of this approach with state-of-the-art demolition and building processes and procedures. Keywords: end-of-life concrete, recycling, hyperspectral imaging, NIR spectroscopy, quality control

Sep 1, 2012

By Paulo Castillo, Cesar Gomez, Jaime Alvarez

Operations using flotation to produce mineral concentrates require testing of frothers to characterize their ability to preserve bubble formation size and to build a stable froth. Many techniques have been proposed to measure parameters associated with these two roles. These techniques focus, in general, on only one of these roles and are based on special equipment operated at conditions quite different from those existing in industrial cells and columns. Both roles have been simultaneously characterized in a laboratory flotation column, but the requirements associated with the installation and operation of one of these units, are a serious limitation for its use on-site. A technique based on the use of a laboratory mechanical cell, a common piece of equipment in operations, will have wider application. Establishing the ability of a frother to control coalescence by preserving bubble formation size is done through bubble size measurements as a function of frother concentration. Froth build-up and stabilization is associated with the amount of water carried by bubbles into the froth layer, which has been demonstrated to correlate with the gas holdup in the collection zone. Procedures devised for determining the critical coalescence concentration (CCC) from measurements of bubble size as a function of frother concentration, and the gas holdup by collection of water displaced from the cell by the presence of bubbles at different frother concentrations, were tested. Three analytical-grade frothers were utilized: a straight-chain (1-heptanol) and a branched (MIBC) alcohol and a polyglycol (PPG425). The results obtained at a standard set of conditions, demonstrated consistent differences between these frothers, and the ranking from least to most effective for reducing bubble size or decreasing water drainage followed the same sequences found when more complex frother characterization techniques are used.

Jan 1, 2014

By E. Emelyanenko, P. Solozhenkin, J. Yagudina, O. Ibragimova

To recover tetrahedrite-tennantite series minerals from porphyry copper-pyrite ores by the froth flotation method, further research on thiol collectors is launched to promote the utilization efficiency of copper ores. In the present paper the adsorption mechanism of the collectors on tennantite surface has been investigated by computational modeling and FTIR-spectroscopic analysis, which have revealed that the decrease in prognosis of collector activity evaluation (PCAE) for tennantite is in the following order: BX (-0.34318), AEROPHINE 3418A (- 0.61756), AERO 5100 (-14.18857). The lower PCAE the stronger the ability of the collector to interact with the mineral surface of tennantite and form the stable complex. More kinetic reliable conditions to form suitable adsorption layer and rupture of the liquid interlayer with AERO 5100 have been observed by FTIR spectra due to decrease of the intensity and stretching and bending vibrations of water (less than 20 and 65%, respectively). In order to verify the feasibility of AERO 5100 as a collector the industrial flotation tests have been conducted. Flotation performance has improved significantly with the stadially grinding and preflotation of tennantite in intercycle copper flotation that allows to avoid desliming of the fragile mineral and minimize loss of Cu and As in tailings. The recovery of copper in copper concentrate increases by 3.9% with the grade maintained.

Jan 1, 2018

By Kauko T. Ingerttilä, Jouko O. Kallioinen, Jaakko O. Leppinen, Alexander V. Lashkul, Vladimir E. Nenno

The Separation in Froth (SIF) technique is based on the idea that the pulp is fed directly onto the froth layer prepared on the surface of liquid medium providing an effective method for separation of coarse particles up to a few millimeters size. Thus the SIF process can result in substantial savings in grinding energy and flotation chemicals. In this work flotation of apatite, calcite and silicate minerals from various industrial sources was investigated using laboratory and pilot plant-scale SIF machines. Flotation of diamonds was also investigated on laboratory scale. It was observed that all the minerals mentioned above can be successfully floated up to about 3 mm particle size. Beneficiation tests with the coarse fractions of classification circuits indicated that final grade calcite concentrate can be obtained with over 90% recovery in one SIF step in this grain size (typically 0,1 to 1,5 mm). Similarly, substantial upgrading of coarse apatite was achieved without grinding it to the fineness required by conventional flotation. SIF could also be applied to the recovery of coarse apatite from the tailings of a conventional flotation process. The capacity measured in the pilot plant test runs for a 1 m2 cell was typically 30 t/m2h. Presently, a full-scale process using the SIF technology is being installed for coarse apatite recovery.

Jan 1, 2003

By V. F. Petrov

Today, sodium cyanide is extensively used for extracting gold, however it is highly toxic to the environment if not managed properly. This paper discusses the key challenges presented to gold operations in efforts to come into alignment with the Russian environmental regulations and suggests solutions to overcome these challenges. It is a fact that the major environmental threat cyanide poses to water sources. Therefore, natural water sources should be well protected from the adverse effect of cyanides used in hydrometallurgical processes. For this, the following site procedures and facilities are practiced: in-site and external water recycling systems, reclaim water treatment if required and tailings ponds with water impermeable screens (tailings ponds with controlled leakage). Cost comparison analysis of cyanide destruction methods was carried out. It was revealed that the aldehyde treatment method developed by Irgiredmet JSC demonstrated the best economics. Cyanide emissions are treated by mass-manufactured packed and membrane devices which allow to keep cyanides at the acceptable limiting values established by environmental regulatory agencies.

Jan 1, 2014

By Francisco Cubillos, Jorge Menacho, Cesar Gomez, Juan Rodríguez

Mineral flotation is the most used process to selectively separate particles of one or more minerals of interest. The process uses natural or induced hydrophobicity to collect particles on the surface of rising bubbles through collisions and formation of bubble-particle aggregates. Flotation machines must keep particles in suspension and well distributed, while at the same time, disperse a mass of air into a population of small bubbles. The efficiency of the separation depends primarily on the characteristics of the bubble population generated in the machine and its distribution and flow throughout its volume. The formation and separation of bubble-particle aggregates create two zones, with strong interactions between them, and with markedly different hydrodynamics conditions. A model describing two-phase hydrodynamics of the continuous and dispersed phases (frother solutions and bubbles, respectively), moving along the whole unit, is proposed. Bubble populations are characterized at the formation stage including the effect of the presence of frothers. Flow through the aggregates formation zone, where bubbles move freely and are closely spherical, is modeled using drift-flux analysis. In the aggregates separation zone, bubbles initially pack maintaining a water layer thick enough to prevent capillary forces to affect their shape. As water drainage proceeds, bubbles deform, capillary channels form, and a network of channels with a diameter size distribution develops; channels become narrower (permeability is reduced) as the distance from the interface increases. Froth hydrodynamics is characterized using models originally developed to describe unsaturated flow through porous solid particle beds. Effects of hydrostatic pressure are considered.

Jan 1, 2014

By D. Hatfield, G. de Jager

"The rapid developments in computer vision and computational resources are creating new possibilities for the use of machine vision systems for industrial control. A number of commercial image analysis systems exist, and research into improved measurements of froth performance is ongoing. An integral part of the implementation of these systems is the validation of the relationship between image analysis measurements and flotation cell performance. This paper discusses the factors affecting concentrate flow and presents the results obtained from one such system with respect to its ability to estimate the flow of concentrate from a flotation cell.The relationship between froth flow speed and the rate of recovery of concentrate from a flotation cell was investigated on two industrial operations, both processing PGM (Platinum Group Metal) bearing ores. Results are presented that show a relationship between froth flow speed and concentrate yield."

Jan 1, 2003

By Vasily V. Lodeischikov, Adolf F. Panchenko, Olga D. Khmelnitskaya, Vladimir E. Dementyev

Pilot plant tests of underground gold leaching from Maminskoye deposit oxide ores at a grade of 0,7 g/t Au were carried out. The underground leaching flow sheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution on active carbon, carbon concentrate ashing and calcine melting to produce high grade gold concentrate. The underground leaching system throughput was 15 m3 of solution per hour. Gold concentration in pregnant solutions was 0.12-0.13 mg/l. Gold recovery from solutions into carbon was in the range of 63-84%. It was demonstrated that the low Au recovery in the adsorption cycle was due to the presence in pregnant solutions of "active" chlorine, which destroys active carbon and causes a sharp decrease of the carbon loading capacity for gold. To improve the adsorption indices, previously dechlorinated pregnant solutions using bituminous coal or Na2S2O3, is recommended. Ion exchange process was tested as an alternative for gold extraction from dechlorinated solutions. In the testwork period, 4.4 kg of gold were produced with a chlorine consumption of 3.5 kg per 1 g of gold. During the tests a program of environmental protection measures was completed to provide the necessary safety precautions of the underground leaching works.

Jan 1, 2003