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Copper is a key metal in the transition to a low-carbon economy. Currently, low grade copper sulphide (e.g., chalcopyrite, CuFeS2) ores make up more than 70% of the global reserves. However, the extraction of copper from low-grade copper sulphides faces several challenges including the use of large volumes of water and the precipitation of secondary minerals that passivate the surface of these low-grade copper minerals and/or clog lixiviant flow pathways in heap systems. While the dissolution of chalcopyrite, one of the main low-grade copper sulphide minerals, has been extensively studied, it is still unclear what mechanisms and secondary minerals lead to surface passivation and how passivation can be inhibited. Hence, this study examined the passivation of primary copper sulphide minerals undergoing coupled dissolution with reprecipitation reactions and the role of reaction-induced porosity. In Chapter 2, the saturation state of potential secondary minerals is modelled using a newly formulated surface-passivate model (SPM). The SPM showed that the precipitation of jarosite at the chalcopyrite surface lowered the reactive surface area and the dissolution rate of chalcopyrite. However, the SPM was limited in modelling the incongruent dissolution of chalcopyrite leading to precipitation of Fe-deficient copper phases because the Fe-deficient copper phase remained consistently undersaturated in trial models. This chapter provides insight for the design of experiments in the subsequent chapters of this thesis. Chapter 3 investigates the nature of secondary minerals and their effects on Cu-mineral surface area and Cu release rates using batch experiments conducted with acid-only and highly concentrated chloride (AlCl3, NaCl, CaCl2) lixiviant. This study showed that Fe leaches ahead of Cu during proton-promoted dissolution of a low-grade porphyry. Also, there was the mobilization of Cu ahead of Fe-S during combined ferric-iron and proton-promoted dissolution of copper sulp

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

An understanding of the spatial and temporal variations of surface moisture content over a heap leach pad is essential for leaching production and to achieve a high ore recovery. Current leach-pad monitoring and data-collection practice is highly labour intensive and exposes technical staff to cyanide solutions. It is proposed that unmanned aerial vehicles (UAVs) equipped with thermal imaging sensors could be used to remotely obtain image data with high temporal and spatial resolution for monitoring the surface moisture distribution over heap leach pads. A field study was conducted over a sprinkler-irrigated heap leach pad at El Gallo gold mine in Sinaloa, Mexico, and the acquired data were used to generate moisture distribution maps of the surface of the pad. The moisture maps created provide direct visualisations of surface moisture variation over the surveyed area and would be effective tools for inspecting heap-leaching operations., An understanding of the spatial and temporal variations of surface moisture content over a heap leach pad is essential for leaching production and to achieve a high ore recovery. Current leach-pad monitoring and data-collection practice is highly labour intensive and exposes technical staff to cyanide solutions. It is proposed that unmanned aerial vehicles (UAVs) equipped with thermal imaging sensors could be used to remotely obtain image data with high temporal and spatial resolution for monitoring the surface moisture distribution over heap leach pads. A field study was conducted over a sprinkler-irrigated heap leach pad at El Gallo gold mine in Sinaloa, Mexico, and the acquired data were used to generate moisture distribution maps of the surface of the pad. The moisture maps created provide direct visualisations of surface moisture variation over the surveyed area and would be effective tools for inspecting heap-leaching operations.

The article considers the process of complex processing of precious metals stored in tailings of concentration plants. The tailings of concentration plants in total occupy 23,000 m3, which causes sufficient damage to the environment and the environment. As a result of the complex processing of non-ferrous metals from tailings, it will be possible to attract accumulated waste to the production and improve environmental protection. However, obtaining the enriched concentration by the conventional flotation method is ineffective, that is, the metal is separated in a smaller amount (35-50%). Studies have found that the most promising direction of processing these ores is leaching.

Heap leaching is a firm extractive metallurgical technology facilitating the economical processing of different kinds of low-grade ores that are otherwise not exploited. Nevertheless, regardless of much development since it was first used, the process advantages are restricted by low recoveries and long extraction times. It is becoming progressively clear that the selection of heap leaching as an appropriate technology to process a specific mineral resource that is both environmentally sound and economically feasible very much relies on having an ample understanding of the essential underlying mechanisms of the processes and how they interrelate with the specific mineralogy of the ore body under concern. This paper provides a critical overview of the role of gangues and clays minerals as rate-limiting factors in copper heap leaching operations. We aim to assess and deliver detailed descriptions and discussions on the relations between different gangues and clays minerals and their impacts on the operational parameters and chemical dynamics in the copper heap leaching processes., Validerad;2021;Nivå 2;2021-10-04 (alebob)

Heap leaching is a firm extractive metallurgical technology facilitating the economical processing of different kinds of low-grade ores that are otherwise not exploited. Nevertheless, regardless of much development since it was first used, the process advantages are restricted by low recoveries and long extraction times. It is becoming progressively clear that the selection of heap leaching as an appropriate technology to process a specific mineral resource that is both environmentally sound and economically feasible very much relies on having an ample understanding of the essential underlying mechanisms of the processes and how they interrelate with the specific mineralogy of the ore body under concern. This paper provides a critical overview of the role of gangues and clays minerals as rate-limiting factors in copper heap leaching operations. We aim to assess and deliver detailed descriptions and discussions on the relations between different gangues and clays minerals and their impacts on the operational parameters and chemical dynamics in the copper heap leaching processes., Validerad;2021;Nivå 2;2021-10-04 (alebob)

With the increasing demand of natural uranium, the exploitation of low-grade or complex uranium ores has been attracting more and more attention. Biological leaching is one of the important techniques for exploitation of such uranium resources. At present, heap leaching and in-situ leaching are the main processes for uranium recovery. A number of laboratory experiments and field trials show that the microbial leaching is a feasible technique for industrial production of uranium from low-grade or refractory ores. The tolerance of microorganisms which have been mutated and acclimatised can be improved obviously and it can be adapted to high fluorine uranium ores, low temperature and high acidity environments. For example, the acclimatised bacteria can grow well in mining tailings with fluorine content of 2-3.98 g/l, under the conditions of a low temperature of 8 degrees C and in a solution with pH 1.2-2.0 or even in a higher acidity solution (pH 0.6). Acclimatisation and induction are common technical ways to improve the adaptability of bacteria species to a leaching environment and indigenous bacteria often have better adaptability to native mining areas. The results also show that there is a synergistic effect between mixed strains and the leaching effect is better than that of a single strain. The indirect action of microbial leaching on uranium ore is clear, but the view on direct action of microorganisms on uranium ore is still controversial. The mechanism of uranium leaching by microorganism, the study of tolerance, the breeding of bacteria and research on the practical application of microbial leaching uranium technology were reviewed, especially in the past 20 years. The development of bioleaching of uranium, especially in-situ leaching, was investigated., With the increasing demand of natural uranium, the exploitation of low-grade or complex uranium ores has been attracting more and more attention. Biological leaching is one of the important techniques for exploitation of such uranium resources. At present, heap leaching and in-situ leaching are the main processes for uranium recovery. A number of laboratory experiments and field trials show that the microbial leaching is a feasible technique for industrial production of uranium from low-grade or refractory ores. The tolerance of microorganisms which have been mutated and acclimatised can be improved obviously and it can be adapted to high fluorine uranium ores, low temperature and high acidity environments. For example, the acclimatised bacteria can grow well in mining tailings with fluorine content of 2-3.98 g/l, under the conditions of a low temperature of 8 degrees C and in a solution with pH 1.2-2.0 or even in a higher acidity solution (pH 0.6). Acclimatisation and induction are common technical ways to improve the adaptability of bacteria species to a leaching environment and indigenous bacteria often have better adaptability to native mining areas. The results also show that there is a synergistic effect between mixed strains and the leaching effect is better than that of a single strain. The indirect action of microbial leaching on uranium ore is clear, but the view on direct action of microorganisms on uranium ore is still controversial. The mechanism of uranium leaching by microorganism, the study of tolerance, the breeding of bacteria and research on the practical application of microbial leaching uranium technology were reviewed, especially in the past 20 years. The development of bioleaching of uranium, especially in-situ leaching, was investigated.

An overview is presented of the large-scale development of Zijinshan low-grade porphyry gold/copper mine, Shanghang county, China. In order to improve gold recovery at the mine, a combination of crushing, washing and screening, gravity-separation, carbon-in-leach and heap-leaching processes which increase the recovery to 82%, compared with 68% for the single heap-leaching process, is described. For copper recovery, the establishment of a specific stable heap-bioleaching system which operates at low pH (c.0.8-1.0), high total soluble iron concentration (c.50 g/l), high temperature (c.45-60 degrees C) and low Leptospirillum microbial activity (c.10 000/ml) in the pregnant leach solution is discussed. This is followed by solvent extraction and electrowinning with a copper recovery of 80% and operational costs of c.US, An overview is presented of the large-scale development of Zijinshan low-grade porphyry gold/copper mine, Shanghang county, China. In order to improve gold recovery at the mine, a combination of crushing, washing and screening, gravity-separation, carbon-in-leach and heap-leaching processes which increase the recovery to 82%, compared with 68% for the single heap-leaching process, is described. For copper recovery, the establishment of a specific stable heap-bioleaching system which operates at low pH (c.0.8-1.0), high total soluble iron concentration (c.50 g/l), high temperature (c.45-60 degrees C) and low Leptospirillum microbial activity (c.10 000/ml) in the pregnant leach solution is discussed. This is followed by solvent extraction and electrowinning with a copper recovery of 80% and operational costs of c.US

Problems in the copper industry include declining copper grades, orebody complexity, the increasing use of sulphide ores, energy and water consumption, and environmental concerns. Important advances have been made in processing efficiency at the front end of the flowsheet, including the use of stirred mills and high pressure grinding rolls. Discussion is presented of developments in sensor-based ore sorting, prompt gamma neutron activation analysis, and magnetic resonance sorting. Developments are also occurring at the back end of flowsheet, such as regrinding in the flotation circuit, thickening, filtration, and coarse flotation technology. While heap leaching bypasses the need for grinding and flotation, traditional sulphuric acid lixiviants aren't effective on sulphide ores. Argo Natural Resources have developed deep eutectic solvents (ionic solvents which are liquid at low temperatures) which can be reused after copper recovery. It is hoped this technology can be used in the recycling of electronic wastes as well as for processing copper ores. Advanced bioleaching is also a promising technology. Anglo American's FutureSmart Mining program for copper flowsheet optimisation focuses on energy efficient comminution, coarse particle recovery, sorting, dry processing, digital transformation and data analytics, and a shift toward cathode production instead of the traditional smelting route., Problems in the copper industry include declining copper grades, orebody complexity, the increasing use of sulphide ores, energy and water consumption, and environmental concerns. Important advances have been made in processing efficiency at the front end of the flowsheet, including the use of stirred mills and high pressure grinding rolls. Discussion is presented of developments in sensor-based ore sorting, prompt gamma neutron activation analysis, and magnetic resonance sorting. Developments are also occurring at the back end of flowsheet, such as regrinding in the flotation circuit, thickening, filtration, and coarse flotation technology. While heap leaching bypasses the need for grinding and flotation, traditional sulphuric acid lixiviants aren't effective on sulphide ores. Argo Natural Resources have developed deep eutectic solvents (ionic solvents which are liquid at low temperatures) which can be reused after copper recovery. It is hoped this technology can be used in the recycling of electronic wastes as well as for processing copper ores. Advanced bioleaching is also a promising technology. Anglo American's FutureSmart Mining program for copper flowsheet optimisation focuses on energy efficient comminution, coarse particle recovery, sorting, dry processing, digital transformation and data analytics, and a shift toward cathode production instead of the traditional smelting route.

Discussion is presented of new ways to increase productivity in heap leaching and solvent extraction. Molecular imprinted polymers (MIPs) can discriminate between metals and can offer cheaper production for gold extraction than activated carbon. Sixth Wave Innovations' IXOS purification beads work like ion exchange resins but leverage the MIP as a mechanism to help reject the non-gold and non-silver metal ions in solution. Laboratory and mine site testing has achieved recoveries of up to 99% of gold from cyanide leach solutions. Chalcopyrite is a problem in copper leaching and conventional leaching has had poor results. Jetti Resources have developed a soluble catalyst that disrupts the sulphur metal bond of the mineral, and which can be used seamlessly with existing heap leach SX-EW facilities. The Pinto Valley operation in Arizona, USA, started using the technology in 2019 and cathode production per area irrigated doubled in the first year. Other copper leaching technologies include FLSmidth's Rapid Oxidative Leaching, Protea Mining Chemicals' solution to help Cu and Co mines reduce product contamination and maximise solvent extraction, and Metso Outotec's MY Renewable Isoalkane bio-based diluent for hydrometallurgical use. Brief discussion is also presented of FLSmidth's mobile stacking conveyor for stacking heaps., Discussion is presented of new ways to increase productivity in heap leaching and solvent extraction. Molecular imprinted polymers (MIPs) can discriminate between metals and can offer cheaper production for gold extraction than activated carbon. Sixth Wave Innovations' IXOS purification beads work like ion exchange resins but leverage the MIP as a mechanism to help reject the non-gold and non-silver metal ions in solution. Laboratory and mine site testing has achieved recoveries of up to 99% of gold from cyanide leach solutions. Chalcopyrite is a problem in copper leaching and conventional leaching has had poor results. Jetti Resources have developed a soluble catalyst that disrupts the sulphur metal bond of the mineral, and which can be used seamlessly with existing heap leach SX-EW facilities. The Pinto Valley operation in Arizona, USA, started using the technology in 2019 and cathode production per area irrigated doubled in the first year. Other copper leaching technologies include FLSmidth's Rapid Oxidative Leaching, Protea Mining Chemicals' solution to help Cu and Co mines reduce product contamination and maximise solvent extraction, and Metso Outotec's MY Renewable Isoalkane bio-based diluent for hydrometallurgical use. Brief discussion is also presented of FLSmidth's mobile stacking conveyor for stacking heaps.

Accelerated carbonation of ultramafic mine tailings has the potential to offset CO2 emissions produced by mining ores from Cu-Ni-platinum group element, podiform chromite, diamondiferous kimberlite, and historical chrysotile deposits. Implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore-processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures. Here, column experiments were designed to trial two geochemical treatments that address these criteria: direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation (10% CO2 in N2); and repeated heap leaching of ultramafic tailings with dilute sulphuric acid. In the first experiment, rapid carbonation of brucite [Mg(OH)2] is reported in the presence of 10% CO2 gas within tailings sampled from the Woodsreef chrysotile mine, New South Wales, Australia. Within four weeks, a doubling is observed of the amount of CO2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field. Reactive transport modelling (MIN3P) is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years. Finally, synchrotron X-ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals (Fe, Ni, Mn, Co, Cr) become highly concentrated within secondary Fe (hydr)oxide minerals at the pH neutralisation horizon within the column experiments. Acid-leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings, waste rock, or low-grade ores., Accelerated carbonation of ultramafic mine tailings has the potential to offset CO2 emissions produced by mining ores from Cu-Ni-platinum group element, podiform chromite, diamondiferous kimberlite, and historical chrysotile deposits. Implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore-processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures. Here, column experiments were designed to trial two geochemical treatments that address these criteria: direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation (10% CO2 in N2); and repeated heap leaching of ultramafic tailings with dilute sulphuric acid. In the first experiment, rapid carbonation of brucite [Mg(OH)2] is reported in the presence of 10% CO2 gas within tailings sampled from the Woodsreef chrysotile mine, New South Wales, Australia. Within four weeks, a doubling is observed of the amount of CO2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field. Reactive transport modelling (MIN3P) is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years. Finally, synchrotron X-ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals (Fe, Ni, Mn, Co, Cr) become highly concentrated within secondary Fe (hydr)oxide minerals at the pH neutralisation horizon within the column experiments. Acid-leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings, waste rock, or low-grade ores.

The Pinto Valley copper leaching facility in Arizona, USA, has enhanced its dump leach performance by using catalytic technology which allows for heap and stockpile leach extraction of copper trapped in challenging ore types such as low-grade primary sulphides, including chalcopyrite. After a successful demonstration phase, Pinto Valley is to expand its leaching activity, targeting up to 300 000 000 tonnes of historic leach stockpile and up to 186 000 000 t of high-grade waste scheduled for removal over the remaining 19 years of mine life., The Pinto Valley copper leaching facility in Arizona, USA, has enhanced its dump leach performance by using catalytic technology which allows for heap and stockpile leach extraction of copper trapped in challenging ore types such as low-grade primary sulphides, including chalcopyrite. After a successful demonstration phase, Pinto Valley is to expand its leaching activity, targeting up to 300 000 000 tonnes of historic leach stockpile and up to 186 000 000 t of high-grade waste scheduled for removal over the remaining 19 years of mine life.

Ore from the Muntanga open cast uranium mine in Zambia is processed by acid heap leaching. Mine waste water is discharged directly into streams and also into a waste water dam. Uranium levels in samples of drinking water collected from boreholes, shallow wells, streams, and dams in the vicinity of the mine were found to exceed the WHO recommended safe levels for drinking water. Water from the streams gave the highest estimated daily intake (3.26 micrograms/kg) followed by that from dams, boreholes, and shallow wells (2.65 micrograms/kg). It was found that the uranium levels make both carcinogenic and non-carcinogenic health risks higher than those recommended by most regulatory bodies. It is recommended that alternative sources of drinking water should be provided or, preferably, drinking water be treated to minimise U content., Ore from the Muntanga open cast uranium mine in Zambia is processed by acid heap leaching. Mine waste water is discharged directly into streams and also into a waste water dam. Uranium levels in samples of drinking water collected from boreholes, shallow wells, streams, and dams in the vicinity of the mine were found to exceed the WHO recommended safe levels for drinking water. Water from the streams gave the highest estimated daily intake (3.26 micrograms/kg) followed by that from dams, boreholes, and shallow wells (2.65 micrograms/kg). It was found that the uranium levels make both carcinogenic and non-carcinogenic health risks higher than those recommended by most regulatory bodies. It is recommended that alternative sources of drinking water should be provided or, preferably, drinking water be treated to minimise U content.

The heap leaching process has been widely used for recovering different metals since its first application at the end of the 1960s. In Chile, copper production via heap leaching has accounted for between 30 and 40% of annual copper production over the past 10 years. This level of production has been achieved through and supported by the use of a mathematical relation, known as the leaching ratio (LR) or irrigation ratio (IR), which relates operational parameters with metal extraction in a heap leaching operation. This ratio has been used to develop leaching column tests, to scale up results from the laboratory to industrial operations, to design new heap leaching plants, and in metallurgical control and production estimation. In spite of the widespread industrial use of this relation, few scientific studies mention it. This is due to its simplicity and basic theoretical foundations. This disparity between industrial practice and scientific research could lead to operational decisions which lack substantial theoretical support, and to scientific studies which have limited industrial impact. In order to guide its future use, this paper describes the leaching ratio and its current uses and limitations, through a literature review and case studies., The heap leaching process has been widely used for recovering different metals since its first application at the end of the 1960s. In Chile, copper production via heap leaching has accounted for between 30 and 40% of annual copper production over the past 10 years. This level of production has been achieved through and supported by the use of a mathematical relation, known as the leaching ratio (LR) or irrigation ratio (IR), which relates operational parameters with metal extraction in a heap leaching operation. This ratio has been used to develop leaching column tests, to scale up results from the laboratory to industrial operations, to design new heap leaching plants, and in metallurgical control and production estimation. In spite of the widespread industrial use of this relation, few scientific studies mention it. This is due to its simplicity and basic theoretical foundations. This disparity between industrial practice and scientific research could lead to operational decisions which lack substantial theoretical support, and to scientific studies which have limited industrial impact. In order to guide its future use, this paper describes the leaching ratio and its current uses and limitations, through a literature review and case studies.

The Terrafame (formerly Talvivaara) mine in northern Finland uses oxidative heap leaching in temperatures which can fall below -30 degrees C, and there is also an annual net precipitation of water. The sulphide ore is very reactive, causing problems with mine water and heating of the heap. The actual water balance during 2017 and 2018 is compared with simulations of annual precipitation and evaporation in a highly arid climate (the Antofagasta Mountains, Chile) and in an area of no excess heat generation in the heap. The discharge requirement and therefore the water footprint of the Terrafame plant was shown to be highly dependent on the climatic conditions. Heat generation in the heap leach operation was shown to be vital for water management operations and therefore the management of discharge. Climate change scenarios show that the need for water discharge from the site would only increase by 5% in the wettest years, whereas raw water utilisation would increase by 46-83% during the driest years. The results suggest that although the heat generation is ore- and process-specific, the water consumption as well as discharge to the surrounding environment is highly dependent on the climatic conditions (precipitation, temperature) in the geographical location., The Terrafame (formerly Talvivaara) mine in northern Finland uses oxidative heap leaching in temperatures which can fall below -30 degrees C, and there is also an annual net precipitation of water. The sulphide ore is very reactive, causing problems with mine water and heating of the heap. The actual water balance during 2017 and 2018 is compared with simulations of annual precipitation and evaporation in a highly arid climate (the Antofagasta Mountains, Chile) and in an area of no excess heat generation in the heap. The discharge requirement and therefore the water footprint of the Terrafame plant was shown to be highly dependent on the climatic conditions. Heat generation in the heap leach operation was shown to be vital for water management operations and therefore the management of discharge. Climate change scenarios show that the need for water discharge from the site would only increase by 5% in the wettest years, whereas raw water utilisation would increase by 46-83% during the driest years. The results suggest that although the heat generation is ore- and process-specific, the water consumption as well as discharge to the surrounding environment is highly dependent on the climatic conditions (precipitation, temperature) in the geographical location.

Heap leaching has low capital expenditure and operating costs, can be set up quickly, and needs low levels of training for routine operation. Disadvantages include reduced metal recovery compared to milling, cash delays at start-up, high risk for low grade ores, difficulty changing leach kinetics and analysing problems, and the need to manage closure and exhausted heaps. Heap leaching of copper sulphide ore (chalcopyrite) needs elevated temperatures and forced aeration for enhancing bacterial oxidation of the ore. Copper recoveries of up to 80% over 120 days are achievable. Development of a leaching facility requires laboratory column testing to predict likely recoveries, and heap leach testwork to consider factors such as ore grade, leaching kinetics, percolation, ore mineralogy, and crush size. The final size and shape of the heap is important, with the best shape being a stepped trapezoid. An example is presented of the heap leaching of low-grade copper-molybdenum porphyry ore at Haib, Namibia, where up to 95.2% of copper can be extracted using bacterial leaching., Heap leaching has low capital expenditure and operating costs, can be set up quickly, and needs low levels of training for routine operation. Disadvantages include reduced metal recovery compared to milling, cash delays at start-up, high risk for low grade ores, difficulty changing leach kinetics and analysing problems, and the need to manage closure and exhausted heaps. Heap leaching of copper sulphide ore (chalcopyrite) needs elevated temperatures and forced aeration for enhancing bacterial oxidation of the ore. Copper recoveries of up to 80% over 120 days are achievable. Development of a leaching facility requires laboratory column testing to predict likely recoveries, and heap leach testwork to consider factors such as ore grade, leaching kinetics, percolation, ore mineralogy, and crush size. The final size and shape of the heap is important, with the best shape being a stepped trapezoid. An example is presented of the heap leaching of low-grade copper-molybdenum porphyry ore at Haib, Namibia, where up to 95.2% of copper can be extracted using bacterial leaching.

Hydraulic conductivity is one of the properties that most influences the leaching solution flow through a mineral heap leach. This paper presents a methodology based on geostatistical and geophysical techniques in order to determine the spatial distribution of hydraulic conductivity in a mineral heap leach. The study is carried out with specific information providedby geophysical profiles carried out in the mineral heap leach of the Gualcamayo Mining Project, located in the Jáchaldepartment of the San Juan province. The variable provided by the geophysical study is electrical resistivity. The statistical and geostatistical analysis of this property makes it possible to estimate values of electrical resistivity in volumetric units, as well as enabling the variance of the error, which gives an idea of the accuracy and degree of uncertainty in the estimation. hus, a mathematical model of resistivities distribution is obtained, from which moisture contents, porosities and hydraulic conductivities inside the heap are estimated. The modeling results makes it possible to identify areas of the heap with different permeabilities, under different conditions of mineral irrigation, which lead to the development of heterogeneous liquid flows that condition the performance in the mineral extraction., La distribución espacial de la conductividad hidráulica es una de las propiedades que más influye sobre el flujo de líquidode solución extractiva, a través de una pila de lixiviación de minerales. En este trabajo se presenta una metodología basadaen técnicas geoestadísticas y geofísicas para determinar la distribución espacial de la conductividad hidráulica en una pila de lixiviación de minerales. El estudio se realiza con la información proporcionada por perfiles geofísicos realizados en la pilade lixiviación de minerales del Proyecto Minero Gualcamayo, ubicado en el departamento Jáchal de la provincia de San Juan. La variable proporcionada por la geofísica es la resistividad eléctrica. El análisis estadístico y geoestadístico de esta propiedad permite tanto estimar valores de resistividad eléctrica en unidades volumétricas, como la varianza del error, que da una idea de la precisión y el grado de incertidumbre en la estimación. De esta forma, se obtiene un modelo matemáticode distribución de resistividades, a partir del cual se estiman contenidos de humedad, porosidades y conductividades hidráulicas en el interior de la pila. Los resultados del modelo permiten identificar sectores de la pila de lixiviación con distintas permeabilidades, lo que condiciona el riego del mineral, conduciendo al desarrollo de flujos de líquido heterogéneosque condicionan el rendimiento en la extracción del mineral.

Multivariate analytical models are quite successful in explaining one or more response variables, based on one or more independent variables. However, they do not reflect the connections of conditional dependence between the variables that explain the model. Otherwise, due to their qualitative and quantitative nature, Bayesian networks allow us to easily visualize the probabilistic relationships between variables of interest, as well as make inferences as a prediction of specific evidence (partial or impartial), diagnosis and decision-making. The current work develops stochastic modeling of the leaching phase in piles by generating a Bayesian network that describes the ore recovery with independent variables, after analyzing the uncertainty of the response to the sensitization of the input variables. These models allow us to recognize the relations of dependence and causality between the sampled variables and can estimate the output against the lack of evidence. The network setting shows that the variables that have the most significant impact on recovery are the time, the heap height and the superficial velocity of the leaching flow, while the validation is given by the low measurements of the error statistics and the normality test of residuals. Finally, probabilistic networks are unique tools to determine and internalize the risk or uncertainty present in the input variables, due to their ability to generate estimates of recovery based upon partial knowledge of the operational variables.

The importance of mine planning is often underestimated. Nonetheless, it is essential in achieving high performance by identifying the potential value of mineral resources and providing an optimal, practical, and realistic strategy for extraction, which considers the greatest quantity of options, materials, and scenarios. Conventional mine planning is based on a mostly deterministic approach, ignoring part of the uncertainty presented in the input data, such as the mineralogical composition of the feed. This work develops a methodology to optimize the mineral recovery of the heap leaching phase by addressing the mineralogical variation of the feed, by alternating the mode of operation depending on the type of ore in the feed. The operational changes considered in the analysis include the leaching of oxide ores by adding only sulfuric acid (H2SO4) as reagent and adding chloride in the case of sulfide ores (secondary sulfides). The incorporation of uncertainty allows the creation of models that maximize the productivity, while confronting the geological uncertainty, as the extraction program progresses. The model seeks to increase the expected recovery from leaching, considering a set of equiprobable geological scenarios. The modeling and simulation of this productive phase is developed through a discrete event simulation (DES) framework. The results of the simulation indicate the potential to address the dynamics of feed variation through the implementation of alternating modes of operation.

A survey is presented of the economic geology of Zimbabwe's gold, its declared output 1898-2014 and mine tonnage milled 1916-1979, the history of the industry, informal and formal alluvial gold operations, open-cast and underground mining methods, the equipment and techniques used for crushing and grinding, gold recovery, heap leaching, and the economics of the three main types of operation: open-cast with heap leaching; open-cast mining; and underground mining, with a selection of recovery grades tabulated from the late 1980s. Environmental aspects of cyanide and mercury use, tailings and waste dumps, and problems with riverbank excavations are also discussed. To conclude the chapter, the stories of three of the country's many gold-mining characters are recounted: John Mack, Norman Levin and the tycoon Tiny Rowland., A survey is presented of the economic geology of Zimbabwe's gold, its declared output 1898-2014 and mine tonnage milled 1916-1979, the history of the industry, informal and formal alluvial gold operations, open-cast and underground mining methods, the equipment and techniques used for crushing and grinding, gold recovery, heap leaching, and the economics of the three main types of operation: open-cast with heap leaching; open-cast mining; and underground mining, with a selection of recovery grades tabulated from the late 1980s. Environmental aspects of cyanide and mercury use, tailings and waste dumps, and problems with riverbank excavations are also discussed. To conclude the chapter, the stories of three of the country's many gold-mining characters are recounted: John Mack, Norman Levin and the tycoon Tiny Rowland.

An overview is presented of Chinese biohydrometallurgical investigations, which have led to increases in utilisation rates of mineral resources from 33 to 96%. Establishment of genomics-based quantitative technology of bioleaching microorganisms and transformation of bioleaching studies from pheno- to geno-type are discussed. A stepwise oxidation model is provided for bioleaching of copper sulphide ore containing iron. Several projects are described including a bioleaching copper-mine plant having a 60 000 000-ton/y processing capacity, a CCGRI patented bio-oxidation gold-extraction technology and a demonstration project in China’s gold industry, and a project to increase the leaching rates of sulphide-coated uranium ore to 96% and to reduce the grades of uranium ore from 0.1 to 0.003%., An overview is presented of Chinese biohydrometallurgical investigations, which have led to increases in utilisation rates of mineral resources from 33 to 96%. Establishment of genomics-based quantitative technology of bioleaching microorganisms and transformation of bioleaching studies from pheno- to geno-type are discussed. A stepwise oxidation model is provided for bioleaching of copper sulphide ore containing iron. Several projects are described including a bioleaching copper-mine plant having a 60 000 000-ton/y processing capacity, a CCGRI patented bio-oxidation gold-extraction technology and a demonstration project in China’s gold industry, and a project to increase the leaching rates of sulphide-coated uranium ore to 96% and to reduce the grades of uranium ore from 0.1 to 0.003%.

An evaluation of high-pressure grinding roll (HPGR) technology for replacing the tertiary cone crushers at the X-Pit crusher, Rochester open-pit silver/gold mine heap-leach facilities, Pershing County, Nevada, USA is presented. On-site and third-party pilot-testing programmes conducted during the period 2016-2018 to investigate the effect of the HPGR crushed product on silver and gold recoveries and heap-leach performance in an open-circuit configuration are described. Tests using cyanide bottle-roll and column leaching include a scoping study at a single press force and the influence of press force on permeability and metal recovery. Hydraulic-conductivity measurements, particle-size distribution data and advanced mineral identification and characterisation system (AMICS) analyses are additionally reported. The results show that silver recovery is projected at 68.2% in 1 y of leaching from HPGR-crushed material, compared to a historical recovery rate of 46.8%; ultimate silver recovery of HPGR-crushed product is estimated to attain a maximum of 69.6% at 5 y, compared to conventional crushing and historical recovery rates needing 20 y to attain a maximum of 61.4%. The HPGR circuit is planned to commence operations at the Rochester-mine X-Pit facility in 2019 with a 2 000 t/h (2 200 st/h) throughput., An evaluation of high-pressure grinding roll (HPGR) technology for replacing the tertiary cone crushers at the X-Pit crusher, Rochester open-pit silver/gold mine heap-leach facilities, Pershing County, Nevada, USA is presented. On-site and third-party pilot-testing programmes conducted during the period 2016-2018 to investigate the effect of the HPGR crushed product on silver and gold recoveries and heap-leach performance in an open-circuit configuration are described. Tests using cyanide bottle-roll and column leaching include a scoping study at a single press force and the influence of press force on permeability and metal recovery. Hydraulic-conductivity measurements, particle-size distribution data and advanced mineral identification and characterisation system (AMICS) analyses are additionally reported. The results show that silver recovery is projected at 68.2% in 1 y of leaching from HPGR-crushed material, compared to a historical recovery rate of 46.8%; ultimate silver recovery of HPGR-crushed product is estimated to attain a maximum of 69.6% at 5 y, compared to conventional crushing and historical recovery rates needing 20 y to attain a maximum of 61.4%. The HPGR circuit is planned to commence operations at the Rochester-mine X-Pit facility in 2019 with a 2 000 t/h (2 200 st/h) throughput.

Studies have been carried out of the effect of surfactant addition on microbial growth, ability for ferrous iron oxidation and chalcopyrite bioleaching using a mixed thermophilic microbial culture (dominant in Metallosphaera hakonensis). The non-ionic surfactants Tween 20, Tween 80, Plurafac LF 120, Plurafac LF 600, and Lutensol XL 90 were tested at concentrations of 5, 10 and 20 mg/l. It was found that the addition of 5 and 10 mg/l Tween 20 showed no negative effect on microbial ferrous iron oxidation and chalcopyrite bioleaching, and its presence was seen to reduce the initial leaching lag time. Microbial ferrous iron oxidation was inhibited in the presence of 10 mg/l Plurafac LF 120 while there was partial inhibition in the system containing 10 mg/l Lutensol XL 90. Plurafac LF 600 at 5 and 10 mg/l and Tween 80 at 10 mg/l inhibited microbial growth completely. In all cases, attachment of the thermophilic microorganisms to the concentrate surface was reduced in the presence of surfactant. However, the corresponding pH, redox potential and copper recovery data indicates that the relative lack of attachment of the microorganisms did not prevent bioleaching activity., Studies have been carried out of the effect of surfactant addition on microbial growth, ability for ferrous iron oxidation and chalcopyrite bioleaching using a mixed thermophilic microbial culture (dominant in Metallosphaera hakonensis). The non-ionic surfactants Tween 20, Tween 80, Plurafac LF 120, Plurafac LF 600, and Lutensol XL 90 were tested at concentrations of 5, 10 and 20 mg/l. It was found that the addition of 5 and 10 mg/l Tween 20 showed no negative effect on microbial ferrous iron oxidation and chalcopyrite bioleaching, and its presence was seen to reduce the initial leaching lag time. Microbial ferrous iron oxidation was inhibited in the presence of 10 mg/l Plurafac LF 120 while there was partial inhibition in the system containing 10 mg/l Lutensol XL 90. Plurafac LF 600 at 5 and 10 mg/l and Tween 80 at 10 mg/l inhibited microbial growth completely. In all cases, attachment of the thermophilic microorganisms to the concentrate surface was reduced in the presence of surfactant. However, the corresponding pH, redox potential and copper recovery data indicates that the relative lack of attachment of the microorganisms did not prevent bioleaching activity.

Heap leaching of ores is becoming a widespread method of metal recovery. It is common practice to initiate irrigation in heap leach facilities with low rates, followed by a gradual increase to the final rate. However, no detailed study has been performed to understand the processes that may lead to better recovery using this technique. Large column tests were performed with copper ore and raffinate solution to study solution-flow behavior under different initial irrigation ramp-up schemes. The columns were monitored for the duration of the tests with moisture sensors, a neutron probe, electrical resistivity tomography, and tensiometers. The baseline test used the final target raffinate irrigation rate from the beginning. The packed ore experienced significant agglomeration collapse, consolidation and decreased permeability, localized ponding, and flow diversion. The slow ramp-up test exhibited minimal ore collapse and no ponding or flow diversion, such that the flow was observed to remain in the center. The faster ramp-up test showed some ore collapse, but no ponding or flow diversion. Water content did not seem to be the only factor involved in agglomeration structure collapse, suggesting that other factors such as pore size variation and flux might take key roles. The results of tracer tests and inverse transport modeling helped to understand flow behavior for the tests. Large dispersivity values resulted from the large scale and wide pore size variation of the ore media. Mobile water fraction and mass transfer coefficients were consistent with compacted ore versus agglomerated structure from the tests. The experimental results, along with the inverse modeling helped in the interpretation of the hydrological processes in heap leaching.

Heap leaching of ores is becoming a widespread method of metal recovery. It is common practice to initiate irrigation in heap leach facilities with low rates, followed by a gradual increase to the final rate. However, no detailed study has been performed to understand the processes that may lead to better recovery using this technique. Large column tests were performed with copper ore and raffinate solution to study solution-flow behavior under different initial irrigation ramp-up schemes. The columns were monitored for the duration of the tests with moisture sensors, a neutron probe, electrical resistivity tomography, and tensiometers. The baseline test used the final target raffinate irrigation rate from the beginning. The packed ore experienced significant agglomeration collapse, consolidation and decreased permeability, localized ponding, and flow diversion. The slow ramp-up test exhibited minimal ore collapse and no ponding or flow diversion, such that the flow was observed to remain in the center. The faster ramp-up test showed some ore collapse, but no ponding or flow diversion. Water content did not seem to be the only factor involved in agglomeration structure collapse, suggesting that other factors such as pore size variation and flux might take key roles. The results of tracer tests and inverse transport modeling helped to understand flow behavior for the tests. Large dispersivity values resulted from the large scale and wide pore size variation of the ore media. Mobile water fraction and mass transfer coefficients were consistent with compacted ore versus agglomerated structure from the tests. The experimental results, along with the inverse modeling helped in the interpretation of the hydrological processes in heap leaching.

Caliche is a mineral exploited in northern Chile, from which iodine and Nitrate salts (saltpeter) are obtained. This ore is the most important source of iodine in the world and is processed mainly by heap leaching using water as a leaching agent. Heap leaching of caliche ore is carried out by the stacking of ROM (Run-Of-Mine) material, where the particle size distribution covers a wide range, from a few millimeters up to several decimeters, even diameters about 1 m. During the leaching, the multiple soluble species of caliche, which can reach total fractions larger than 40%, are dissolved at different rates, mainly controlled by their solubilities. When it occurs and unlike most other leachable ores, the particle size diminishes. The leaching modeling of several soluble species of caliche has been recently addressed; however, one of the main assumptions is the idealization that the heap is composed of particles of the same size. The present work aims to complement the previously formulated phenomenological models for caliche ore leaching, through a model that considers the simultaneous dissolution of two species from caliche with three different particle sizes. These two water-soluble species have different solubilities and dissolution rates and the conceptual model considers that both species are dissolved at the particle surface. When the most soluble species is being depleted, the particle collapses, leaving a remaining fraction of the less soluble species together with insoluble material. The less soluble species is now being dissolved from the collapsed material. This article also includes the experimental verification of the conceptual model using data obtained from column leaching tests conducted for this purpose, focusing on the dissolution of two soluble species: Nitrate and Magnesium., QC 20180213

A heap leaching study was conducted with a pyrrhotite rich pentlandite black schist ore originating from Talvivaara, Finland. The ore contains about 20 wt% metal sulphides, with pyrite and pyrrhotite as the dominant sulphide species. Valuable metals for the operation are present in pyrrhotite (nickel), pentlandite, violarite and sphalerite. The ore was crushed to 80% below 8 mm size, agglomerated and stacked to two 8.5 m tall heaps with 350 m width and 132 m top length. The first heap was constructed in autumn 2015 and the second during winter 2016. Irrigation with 5 to 7 L/m2/h was applied from the top of the heap and air feed (ca. 0.06 m3/ton ore/hour) applied with two-level piping inside the heap. Heat generation was estimated from the heat transferred to the solution across the heaps. Optical cables were installed inside the heap sections and temperature read by the distributed temperature sensing (DTS) method. DTS method was shown to work in a heap with temperatures up to 160 degrees C. The heat generation rates were observed up to 10 W/ton ore, representing oxygen (in air) efficiencies from 10 to 14%. The heap section constructed during winter experienced a lag in heat generation while the one constructed in autumn heated up in two to three days after irrigation and aeration were started. (Authors.), A heap leaching study was conducted with a pyrrhotite rich pentlandite black schist ore originating from Talvivaara, Finland. The ore contains about 20 wt% metal sulphides, with pyrite and pyrrhotite as the dominant sulphide species. Valuable metals for the operation are present in pyrrhotite (nickel), pentlandite, violarite and sphalerite. The ore was crushed to 80% below 8 mm size, agglomerated and stacked to two 8.5 m tall heaps with 350 m width and 132 m top length. The first heap was constructed in autumn 2015 and the second during winter 2016. Irrigation with 5 to 7 L/m2/h was applied from the top of the heap and air feed (ca. 0.06 m3/ton ore/hour) applied with two-level piping inside the heap. Heat generation was estimated from the heat transferred to the solution across the heaps. Optical cables were installed inside the heap sections and temperature read by the distributed temperature sensing (DTS) method. DTS method was shown to work in a heap with temperatures up to 160 degrees C. The heat generation rates were observed up to 10 W/ton ore, representing oxygen (in air) efficiencies from 10 to 14%. The heap section constructed during winter experienced a lag in heat generation while the one constructed in autumn heated up in two to three days after irrigation and aeration were started. (Authors.)

Heap leaching is responsible for approximately 21% — 3 900 000 metric tonnes — of copper production and 9% — 270 metric t or 8 700 000 ounces — of gold production worldwide. Given metal price assumptions of US, Heap leaching is responsible for approximately 21% — 3 900 000 metric tonnes — of copper production and 9% — 270 metric t or 8 700 000 ounces — of gold production worldwide. Given metal price assumptions of US

An investigation of the effect of microwave irradiation on high-pressure grinding roll-crushed small (-5+4.75 mm), medium (-16+9.5 mm) and large (-25+19 mm) particles of massive zinc sulphide ore (sphalerite) is presented. X-ray computed tomography and QEMSCAN analyses indicate that, following microwave treatment, the internal crack volumes of the particles increase and mineral grain exposure increases of 28, 26 and 15% are found for the small, medium and large particles, respectively. Long-term (350-d) column bioleaching tests performed by inoculating with a mixed culture of adapted mesophilic acidophilic chemolithotrophs (Leptospirillum ferriphilum) and leaching at 30 degrees C with acidic ferrous solution gives 26, 24 and 23% increases in zinc recovery for the small, medium and large microwave-treated particles, respectively., An investigation of the effect of microwave irradiation on high-pressure grinding roll-crushed small (-5+4.75 mm), medium (-16+9.5 mm) and large (-25+19 mm) particles of massive zinc sulphide ore (sphalerite) is presented. X-ray computed tomography and QEMSCAN analyses indicate that, following microwave treatment, the internal crack volumes of the particles increase and mineral grain exposure increases of 28, 26 and 15% are found for the small, medium and large particles, respectively. Long-term (350-d) column bioleaching tests performed by inoculating with a mixed culture of adapted mesophilic acidophilic chemolithotrophs (Leptospirillum ferriphilum) and leaching at 30 degrees C with acidic ferrous solution gives 26, 24 and 23% increases in zinc recovery for the small, medium and large microwave-treated particles, respectively.

A small-scale hydrogeometallurgical laboratory test has been developed to serve as a proxy for column, and by inference, heap leaching. Over 50 leach tests were conducted on low-grade nickel laterite ores from Western Australia to compare predicted nickel recoveries, acid consumption and leach kinetics, and to determine whether insight into potential scale-up effects could be obtained. The column leach test was performed along with four different small-scale proxy leach tests: high-pressure acid leach, stirred atmospheric leach, bottle roll leach, and shaker table leach. The most promising proxy test was found to be a rapid hydrogeometallurgical shaker leach test, which gave statistically significant recovery and acid consumption correlations to the column leach tests. The accuracy of the small-scale tests was confirmed by column tests run on new laterite ores. This geometallurgical proxy could be of use for the population of block models and process selection during the mine planning phase or for optimisation and control during processing., A small-scale hydrogeometallurgical laboratory test has been developed to serve as a proxy for column, and by inference, heap leaching. Over 50 leach tests were conducted on low-grade nickel laterite ores from Western Australia to compare predicted nickel recoveries, acid consumption and leach kinetics, and to determine whether insight into potential scale-up effects could be obtained. The column leach test was performed along with four different small-scale proxy leach tests: high-pressure acid leach, stirred atmospheric leach, bottle roll leach, and shaker table leach. The most promising proxy test was found to be a rapid hydrogeometallurgical shaker leach test, which gave statistically significant recovery and acid consumption correlations to the column leach tests. The accuracy of the small-scale tests was confirmed by column tests run on new laterite ores. This geometallurgical proxy could be of use for the population of block models and process selection during the mine planning phase or for optimisation and control during processing.

A proposed expansion to the Cosmic Boy concentrator (Western Australia) is being developed to treat an impurity stream that is high in nickel and would otherwise report to tails. The concentrator produces around 25 000 t/a of nickel in concentrate from low As ores from the Flying Fox mine and higher As ores from Spotted Quoll. The flowsheet consists of a flash float on the cyclone underflow in the milling circuit followed by conventional rougher and scavenger circuit on the cyclone overflow, with one stage of optional cleaning. BioHeap technology will be used for Spotted Quoll ores to recover Ni and discard As to tailings. The expansion will consist of a biohydrometallurgical plant that leaches the nickel arsenic minerals, removing the arsenic as a stable iron/arsenic hydroxide, while recovering the nickel as a high-grade nickel sulphide product (at approximately 50% Ni). This will then be blended with the final concentrate to improve nickel grades and recoveries, while simultaneously reducing impurity levels, or used to produce high value products such as nickel sulphate., A proposed expansion to the Cosmic Boy concentrator (Western Australia) is being developed to treat an impurity stream that is high in nickel and would otherwise report to tails. The concentrator produces around 25 000 t/a of nickel in concentrate from low As ores from the Flying Fox mine and higher As ores from Spotted Quoll. The flowsheet consists of a flash float on the cyclone underflow in the milling circuit followed by conventional rougher and scavenger circuit on the cyclone overflow, with one stage of optional cleaning. BioHeap technology will be used for Spotted Quoll ores to recover Ni and discard As to tailings. The expansion will consist of a biohydrometallurgical plant that leaches the nickel arsenic minerals, removing the arsenic as a stable iron/arsenic hydroxide, while recovering the nickel as a high-grade nickel sulphide product (at approximately 50% Ni). This will then be blended with the final concentrate to improve nickel grades and recoveries, while simultaneously reducing impurity levels, or used to produce high value products such as nickel sulphate.

Quebrada Blanca, Chile, is a high-tonnage porphyry deposit with low grade copper in the hypogene zone and higher grades in the supergene zone. Recent exploration has extended the supergene resource life-of-mine (LOM) by 5 years, to 2020, and geometallurgical variables (including copper recovery and acid consumption) have been added to the geological model to optimise production. LOM lithologies include diorites, quartz monzonites, porphyries, igneous, and tourmaline breccias with main alteration present being potassic, phyllic and argillic. The deposit can be geometallurgically represented by twelve litho-alteration units, which cover 98% of the LOM volume. 40 mini-column tests were carried out to obtain kinetics curves and Cu recovery values after comparing the difference between head and tails grades. Acid consumption was obtained using an automatic neutralised device-based test. It was found that lower recoveries (of around 60%) were related to potassic-altered diorites and argillic-altered quartz monzonites while the best recoveries (around 80%) were obtained in potassic-altered quartz monzonites and argillic-altered diorites. The most reactive rock was the potassic-altered diorite, with 12 kg/t of acid consumption. The final geometallurgical model was calculated using a program that relates each geometallurgical unit with a specific copper recovery and acid consumption value. Results from comparisons with historical leach pad data were used to validate the model., Quebrada Blanca, Chile, is a high-tonnage porphyry deposit with low grade copper in the hypogene zone and higher grades in the supergene zone. Recent exploration has extended the supergene resource life-of-mine (LOM) by 5 years, to 2020, and geometallurgical variables (including copper recovery and acid consumption) have been added to the geological model to optimise production. LOM lithologies include diorites, quartz monzonites, porphyries, igneous, and tourmaline breccias with main alteration present being potassic, phyllic and argillic. The deposit can be geometallurgically represented by twelve litho-alteration units, which cover 98% of the LOM volume. 40 mini-column tests were carried out to obtain kinetics curves and Cu recovery values after comparing the difference between head and tails grades. Acid consumption was obtained using an automatic neutralised device-based test. It was found that lower recoveries (of around 60%) were related to potassic-altered diorites and argillic-altered quartz monzonites while the best recoveries (around 80%) were obtained in potassic-altered quartz monzonites and argillic-altered diorites. The most reactive rock was the potassic-altered diorite, with 12 kg/t of acid consumption. The final geometallurgical model was calculated using a program that relates each geometallurgical unit with a specific copper recovery and acid consumption value. Results from comparisons with historical leach pad data were used to validate the model.

The leaching kinetics and reaction mechanism of uranium from a natural, metamict betafite sample have been studied using oxidative acidic solutions under different temperature and reagent concentrations. Almost complete extraction of uranium was observed by leaching in a solution containing 214.5 g/l H2SO4 and 2.0 g/l Fe3+ at 89 degrees C for 48 h. Alternative leaching conditions using 57.1 g/l H2SO4 and 36.7 g/l Fe3+ at the same temperature also resulted in practically complete extraction of uranium and improved the selectivity for uranium over titanium, tantalum and niobium. A portion of the betafite sample used in the leaching tests was recrystallised by heating in air at 1 100 degrees C. This was leached under similar conditions to those applied to the metamict sample and the highest extraction achieved was 12% uranium. This implies that the extent of metamiction is a significant indicator of the leaching behaviour that can be expected for a particular betafite mineralisation and that heat treatment prior to leaching should be avoided. The thermal recrystallisation of betafite seems to have resulted in tantalum enrichment on the surface of betafite particles, which may be related to the lower extraction of uranium observed., The leaching kinetics and reaction mechanism of uranium from a natural, metamict betafite sample have been studied using oxidative acidic solutions under different temperature and reagent concentrations. Almost complete extraction of uranium was observed by leaching in a solution containing 214.5 g/l H2SO4 and 2.0 g/l Fe3+ at 89 degrees C for 48 h. Alternative leaching conditions using 57.1 g/l H2SO4 and 36.7 g/l Fe3+ at the same temperature also resulted in practically complete extraction of uranium and improved the selectivity for uranium over titanium, tantalum and niobium. A portion of the betafite sample used in the leaching tests was recrystallised by heating in air at 1 100 degrees C. This was leached under similar conditions to those applied to the metamict sample and the highest extraction achieved was 12% uranium. This implies that the extent of metamiction is a significant indicator of the leaching behaviour that can be expected for a particular betafite mineralisation and that heat treatment prior to leaching should be avoided. The thermal recrystallisation of betafite seems to have resulted in tantalum enrichment on the surface of betafite particles, which may be related to the lower extraction of uranium observed.

The Productora deposit is a porphyry-copper style deposit with chalcopyrite as the main ore. It can be exploited using open pit mining, with preparation of a saleable concentrate from fresh ore as well as heap leaching, solvent extraction and electrowinning of copper from oxide ores. A geometallurgical model was developed during the prefeasibility study to predict the process responses of both sulphide and oxide ores. The model incorporates test results from mineralogical, metallurgical, and comminution testing, as well as other studies from samples collected from the deposit. The variability of sulphide ore throughput and comminution costs were estimated using Bond Work Index and Abrasion Index proxies in the geometallurgical model. Heap leach acid consumption in oxide ore was estimated from drill hole calcium concentrations. The model was then used in mine scheduling to identify high- and low-throughput or high- and low-acid ore zones so that the processing of these zones could be advanced or deferred to improve net present value. The cost benefits of preparing an early-stage geometallurgy model were quantified through a comparison with a conventional model based on test work averages., The Productora deposit is a porphyry-copper style deposit with chalcopyrite as the main ore. It can be exploited using open pit mining, with preparation of a saleable concentrate from fresh ore as well as heap leaching, solvent extraction and electrowinning of copper from oxide ores. A geometallurgical model was developed during the prefeasibility study to predict the process responses of both sulphide and oxide ores. The model incorporates test results from mineralogical, metallurgical, and comminution testing, as well as other studies from samples collected from the deposit. The variability of sulphide ore throughput and comminution costs were estimated using Bond Work Index and Abrasion Index proxies in the geometallurgical model. Heap leach acid consumption in oxide ore was estimated from drill hole calcium concentrations. The model was then used in mine scheduling to identify high- and low-throughput or high- and low-acid ore zones so that the processing of these zones could be advanced or deferred to improve net present value. The cost benefits of preparing an early-stage geometallurgy model were quantified through a comparison with a conventional model based on test work averages.

Nuclear installations in Brazil, which includes all uranium and thorium mining and milling facilities, are subject to a Nuclear Licence and an Environmental Licence. The main activities during the licensing process are safety evaluation and regulatory inspections. Quiteria has the largest discovered uranium reserve in Brazil and the site is in the process of commissioning. Caetite is the only active uranium mine and has been in operation since 2000 with reserves of 100 000 t of U3O8. Ore is mined using open cast methods and the processing plant can treat 200 000 t/y to produce 400 t/y U3O8. After agglomeration and heap leaching, the ore is processed by solvent extraction, stripping using NaCl solution, precipitation as ADU, solid/liquid separation and precipitate washing in a decanter and vacuum belt filter system, and drying of the washed precipitate. The waste rock pile is on the natural slope of a dry valley and rain water infiltration is treated or directly discharged to the environment. The leached ore is encapsulated within the waste rock pile. After waste rock piles reach their final elevation they are covered with clay and a topsoil cover, and revegetation is carried out. Surface and groundwaters are monitored and intervention measures carried out if necessary., Nuclear installations in Brazil, which includes all uranium and thorium mining and milling facilities, are subject to a Nuclear Licence and an Environmental Licence. The main activities during the licensing process are safety evaluation and regulatory inspections. Quiteria has the largest discovered uranium reserve in Brazil and the site is in the process of commissioning. Caetite is the only active uranium mine and has been in operation since 2000 with reserves of 100 000 t of U3O8. Ore is mined using open cast methods and the processing plant can treat 200 000 t/y to produce 400 t/y U3O8. After agglomeration and heap leaching, the ore is processed by solvent extraction, stripping using NaCl solution, precipitation as ADU, solid/liquid separation and precipitate washing in a decanter and vacuum belt filter system, and drying of the washed precipitate. The waste rock pile is on the natural slope of a dry valley and rain water infiltration is treated or directly discharged to the environment. The leached ore is encapsulated within the waste rock pile. After waste rock piles reach their final elevation they are covered with clay and a topsoil cover, and revegetation is carried out. Surface and groundwaters are monitored and intervention measures carried out if necessary.

The following abstracts are included from sessions on laterites, environment/safety, process development, solvent extraction, copper solvent extraction-electrowinning, bioleaching, pressure oxidation and pressure acid leaching: HPAL in past, present and future, by Tsuchida T., p.2; Technical and cost comparison of laterite treatment processes Part 3, by Dry M., p.24; Atmospheric leaching of Ni laterites with Fe precipitation, by White D.T. and Gillaspie J.D., p.48; Inverse leaching process for Ni laterite ores, by Jiang Kaixi et al., p.68; An atmospheric dissolving process for laterites, by Rastas J. et al., p.79; A comparison study for Ni and Cu processing technologies using life cycle assessment, by Khoo J. et al., p.95; Implications of the presence of radioactivity in Cu concentrates, by Manis A. and Ring B., p.103; Advances in non-ferrous pyrometallurgy, by Walton M., p.117; Can farming Ni pay for your testwork and feasibility studies? by Willis B., p.126; Flowsheet options for treatment of difficult Ni residues, by Muller B., p.139; alkaline glycine systems as alternative leaching reagents for Cu deposits of complex mineralogy, by Eksteen J. et al., p.168; Solvent extraction of Ni - 28 years of endeavour, by Mackenzie M., p.191; A new solvent extraction approach to Ni laterite leach solutions, by Zhu Zhaowu et al., p.212; Direct solvent extraction for the recovery of Ni and Co from nitric acid Ni laterite leach liquors, by Hutton-Ashkenny M., Ibana D. and Barnard K.R., p.224; New synergistic solvent extraction systems for separation and recovery of Ni, Co, Cu and Zn in H2SO4, HNO3 and HCl acid leach solutions, by Zhang Wensheng and Kelly N., p.239; Recovery of base metals from concentrated chloride solutions via solvent extraction, by Harris B. and White C., p.253; 43 Years of Escaid diluents use in solvent extraction (SX), by Bien D., p.265; Using principles of inherent safety for design of hydrometallurgical solvent extraction plants, by Moore L.J., p.273; Tu, The following abstracts are included from sessions on laterites, environment/safety, process development, solvent extraction, copper solvent extraction-electrowinning, bioleaching, pressure oxidation and pressure acid leaching: HPAL in past, present and future, by Tsuchida T., p.2; Technical and cost comparison of laterite treatment processes Part 3, by Dry M., p.24; Atmospheric leaching of Ni laterites with Fe precipitation, by White D.T. and Gillaspie J.D., p.48; Inverse leaching process for Ni laterite ores, by Jiang Kaixi et al., p.68; An atmospheric dissolving process for laterites, by Rastas J. et al., p.79; A comparison study for Ni and Cu processing technologies using life cycle assessment, by Khoo J. et al., p.95; Implications of the presence of radioactivity in Cu concentrates, by Manis A. and Ring B., p.103; Advances in non-ferrous pyrometallurgy, by Walton M., p.117; Can farming Ni pay for your testwork and feasibility studies? by Willis B., p.126; Flowsheet options for treatment of difficult Ni residues, by Muller B., p.139; alkaline glycine systems as alternative leaching reagents for Cu deposits of complex mineralogy, by Eksteen J. et al., p.168; Solvent extraction of Ni - 28 years of endeavour, by Mackenzie M., p.191; A new solvent extraction approach to Ni laterite leach solutions, by Zhu Zhaowu et al., p.212; Direct solvent extraction for the recovery of Ni and Co from nitric acid Ni laterite leach liquors, by Hutton-Ashkenny M., Ibana D. and Barnard K.R., p.224; New synergistic solvent extraction systems for separation and recovery of Ni, Co, Cu and Zn in H2SO4, HNO3 and HCl acid leach solutions, by Zhang Wensheng and Kelly N., p.239; Recovery of base metals from concentrated chloride solutions via solvent extraction, by Harris B. and White C., p.253; 43 Years of Escaid diluents use in solvent extraction (SX), by Bien D., p.265; Using principles of inherent safety for design of hydrometallurgical solvent extraction plants, by Moore L.J., p.273; Tu

The main map and five larger-scale inset maps indicate names and global locations of major base metal, precious metal, industrial mineral and uranium heap leach mines and projects. Symbols illustrate the nature of the facilities: mines which are producing, suspended or developing, projects which have feasibility completed, and stand-alone refineries. The chemical symbol of each commodity - gold, silver, copper, iodine, molybdenum, nickel, uranium and zinc - appears below the name of the facility. Four of the inset maps relate to projects along the western cordilleras of North and South America, while the fifth large-scale map includes Kuranakh gold mine and neighbouring operations in Siberia, Russia., The main map and five larger-scale inset maps indicate names and global locations of major base metal, precious metal, industrial mineral and uranium heap leach mines and projects. Symbols illustrate the nature of the facilities: mines which are producing, suspended or developing, projects which have feasibility completed, and stand-alone refineries. The chemical symbol of each commodity - gold, silver, copper, iodine, molybdenum, nickel, uranium and zinc - appears below the name of the facility. Four of the inset maps relate to projects along the western cordilleras of North and South America, while the fifth large-scale map includes Kuranakh gold mine and neighbouring operations in Siberia, Russia.

The use of a very wide range of metals, often in niche applications that exploit their specific properties, has expanded hugely over the past 30 years while demand for metals such as Fe, Al and Cu is expected to double in the next 15-20 years; however haulage, milling and comminution of metal ores consumes 5-6% of global energy produced and conventional extraction gives rise to air and water pollution. Biomining, the use of lithotrophic microorganisms to degrade sulphide minerals selectively in low-pH liquors in order to access the energy locked up in reduced S and Fe, has developed from the Cu dump mining of the 1960s but has not transformed the industry due to its slowness, limited range of target ores, existing smelters representing large-scale investment, mistrust of biotechnology, a few cases where biomining has failed or caused environmental problems, and its overplayed green credentials. Accounting for c.5% of global Cu production, 5% of Au and smaller percentages of Ni, Zn and U, biomining has major advantages for low-grade/run-of-mine ores as at Dexing in China and Chino in New Mexico, for heap bioleaching of primary and secondary sulphides at sites with establlished oxide SX-EW as at Escondida in Chile, for biooxidation of refractory ores as at Sansu, Ashanti in Ghana, in cases where producing a concentrate is problematic as with the Talvivaara Ni-Zn-Cu black schist in Finland that contains c.10% graphite, and where smelting incurs a penalty as with high-As concentrates. Such biomining does not eliminate the energy and other costs associated with conventional mining, though waste reprocessing as at Kasese in Uganda does have lower energy cost. New developments include reductive bioprocessing of oxidised ores, initially designed to extract Ni from laterites but possibly applicable to occluded REE minerals, and deep in-situ biomining of hard-rock sulphides at 1-2 km depth by processes such as the BioMOre indirect system whereby acidic Fe(3+)-rich liquors wou, The use of a very wide range of metals, often in niche applications that exploit their specific properties, has expanded hugely over the past 30 years while demand for metals such as Fe, Al and Cu is expected to double in the next 15-20 years; however haulage, milling and comminution of metal ores consumes 5-6% of global energy produced and conventional extraction gives rise to air and water pollution. Biomining, the use of lithotrophic microorganisms to degrade sulphide minerals selectively in low-pH liquors in order to access the energy locked up in reduced S and Fe, has developed from the Cu dump mining of the 1960s but has not transformed the industry due to its slowness, limited range of target ores, existing smelters representing large-scale investment, mistrust of biotechnology, a few cases where biomining has failed or caused environmental problems, and its overplayed green credentials. Accounting for c.5% of global Cu production, 5% of Au and smaller percentages of Ni, Zn and U, biomining has major advantages for low-grade/run-of-mine ores as at Dexing in China and Chino in New Mexico, for heap bioleaching of primary and secondary sulphides at sites with establlished oxide SX-EW as at Escondida in Chile, for biooxidation of refractory ores as at Sansu, Ashanti in Ghana, in cases where producing a concentrate is problematic as with the Talvivaara Ni-Zn-Cu black schist in Finland that contains c.10% graphite, and where smelting incurs a penalty as with high-As concentrates. Such biomining does not eliminate the energy and other costs associated with conventional mining, though waste reprocessing as at Kasese in Uganda does have lower energy cost. New developments include reductive bioprocessing of oxidised ores, initially designed to extract Ni from laterites but possibly applicable to occluded REE minerals, and deep in-situ biomining of hard-rock sulphides at 1-2 km depth by processes such as the BioMOre indirect system whereby acidic Fe(3+)-rich liquors wou

The following abstracts are included: The untold story of the Australian METS sector - a, The following abstracts are included: The untold story of the Australian METS sector - a

Predictions of how a mining complex might adapt to a gradual reduction in uncertainty can be carried out using per-state policies. This concept is illustrated using data from a copper-gold mine where the extracted ore (sulphides, transition, and oxides) is sent to one of 6 initial destinations: a sulphide mill, a sulphide heap leach, a sulphide dump leach, a transition heap leach, an oxide heap leach, or an oxide waste dump. Six mining periods (years) are considered and 50 orebody simulations used to model geological uncertainty. Results show that the approximate dynamic programming methodology can successfully construct a per-state policy with significantly superior performance to that of a policy based on a greedy heuristic., Predictions of how a mining complex might adapt to a gradual reduction in uncertainty can be carried out using per-state policies. This concept is illustrated using data from a copper-gold mine where the extracted ore (sulphides, transition, and oxides) is sent to one of 6 initial destinations: a sulphide mill, a sulphide heap leach, a sulphide dump leach, a transition heap leach, an oxide heap leach, or an oxide waste dump. Six mining periods (years) are considered and 50 orebody simulations used to model geological uncertainty. Results show that the approximate dynamic programming methodology can successfully construct a per-state policy with significantly superior performance to that of a policy based on a greedy heuristic.

A novel sequential heap leaching process has been identified as a possible alternative to the conventional concentrate–smelt–refine route for processing Platreef ore, a platinum group metals containing ore with palladium predominance. The present study focuses on testing this process on crushed whole ore, after initial experiments conducted on low-grade Platreef flotation concentrate achieved promising results. Two samples of drill core Platreef ore with size distributions of - 25 mm + 1 mm and - 6 mm + 1 mm were first bioleached in cylindrical columns, to simulate heap leaching, at 65 °C and then leached with cyanide solution at 50 °C in cylindrical columns. Overall the best results were achieved from the tests on the - 6 mm + 1 mm size fraction sample. After 304 days 93% Cu, 75% Ni and 53% Co were extracted in the bioleach experiment, and after 60 days 57.8% Pt, 99.7% Pd and 90.3% Au in the follow-up cyanide leach experiment. Analysis using a mineral liberation analyser suggested that Pt and Pd were leached mostly from the tellurides while the Pt arsenides appeared resistant to cyanide leaching. From the results it is proposed that the process considered herein is a potential alternative route to treat Platreef ore.

Three largely-independent studies were undertaken on the same heap leach system during the period of transition from processing oxidised ores to sulfide ores: monitoring of heap solutions for microorganisms, analysis of samples from a spent heap, and column tests. Microbial cell numbers and diversity were monitored in process water samples from the transition heap over a four-year period. Cell numbers remained low throughout, 1–30 × 104 cells mL−1, possibly reflecting growth inhibition by the high element concentrations in process water. High iron, magnesium and aluminium concentrations in spent heap pregnant leach solution (PLS) are attributed to siderite and clinochlore dissolution and would be expected to impact on microbial growth. Planktonic cell numbers in a column leachate declined rapidly by two orders of magnitude when concentrations of ferric ion and sulfate exceeded 30 and 75 g L−1, respectively. Nevertheless, a variety of bacterial strains closely related to Acidithiobacillus (At.) ferrooxidans, At. caldus, Leptospirillum (L.) ferriphilum, Acidimicrobium (Am.) ferrooxidans, Acidiphilium (Ap.) cryptum, an Alicyclobacillus-related strain and Sulfobacillus (S.) thermosulfidooxidans, and the archaeon Ferroplasma (F.) acidiphilum were isolated, mainly from the more acidic intermediate leach solutions (ILS).Overall, the results obtained from the use of culture-dependent and culture-independent methods of community analysis were complementary and consistent. The majority of identified genera and species were present in both the process water samples from the operating heap and the solutions and ore samples from the spent heap. In the spent heap, distinct populations dominated different sample types. Leptospirillum- and Acidithiobacillus-like strains dominated PLS samples and Leptospirillum also dominated seven of eight spent ore samples and all of the heap sediment samples, making it the primary iron(II) oxidising species.

Caliche is a mineral that contains a high fraction of soluble minerals and that is exploited in Northern Chile through vat or heap leaching for the production of iodine and nitrate. In this zone, the water availability is scarce, being a critical issue for the mining industries and whereby the use of other leaching agents as seawater may be a viable alternative. For this reason in the present study, column-leaching experiments using seawater were performed, including different irrigation rates and column heights. It is found that the highly soluble minerals such as nitrate and iodate are rapidly leached, while for other minerals like sulphate and chloride, the outlet concentration increased once that part of the sodium has been removed. Crystals of sodium sulphate were found at the column bottom, when this was dismantled. An existing phenomenological model (Gálvez et al., 2012) was used to analyse the changes of concentration of nitrate and iodine (as iodate) with a good agreement between the experiments and the simulations. On the other hand, for sulphate and chloride a new model was developed, which takes into account the dissolution and precipitation phenomena of these ions. The model was able to capture the trends observed in the experiments for the outlet concentrations of the modelled ions., QC 20131105

The main map and five inset maps show names and locations of base and precious metal and uranium heap leaching facilities around the world. Symbols distinguish producing, suspended, developing, feasibility and pre-feasibility projects and the commodities being heap leached include gold, silver, cobalt, copper, molybdenum, nickel, lead, uranium, tungsten and zinc. As well as large numbers of Au-Ag and Cu-Mo projects along the western cordilleras of North and South America, to which four of the five larger-scale inset maps relate, many projects are identified in western (Au, U) and southern (Cu-Co, Au, U) Africa, across central and eastern Asia (mainly Au), in south-east Asia (including Sokor Au-Pb-Ag-Zn and Wetar Cu-Au-Ag-Zn) and Australia (Au, Ni, Cu et al), and in the Middle East (precious and base metals), as well as a few in Europe: Talvivaara Ni-Zn-Cu-Co-U, Biely Vrch Au, Assarel Cu, and Smolino and Salamanca U., The main map and five inset maps show names and locations of base and precious metal and uranium heap leaching facilities around the world. Symbols distinguish producing, suspended, developing, feasibility and pre-feasibility projects and the commodities being heap leached include gold, silver, cobalt, copper, molybdenum, nickel, lead, uranium, tungsten and zinc. As well as large numbers of Au-Ag and Cu-Mo projects along the western cordilleras of North and South America, to which four of the five larger-scale inset maps relate, many projects are identified in western (Au, U) and southern (Cu-Co, Au, U) Africa, across central and eastern Asia (mainly Au), in south-east Asia (including Sokor Au-Pb-Ag-Zn and Wetar Cu-Au-Ag-Zn) and Australia (Au, Ni, Cu et al), and in the Middle East (precious and base metals), as well as a few in Europe: Talvivaara Ni-Zn-Cu-Co-U, Biely Vrch Au, Assarel Cu, and Smolino and Salamanca U.