Heap leaching is a lowcost technology used in industrial mining to recover precious metals such as gold and uranium, along with several other highly sought after metals like copper, from their primary resources ores and minerals. Uranium leaching uranium leaching is more important than copper, although less amount of uranium is obtained than copper. Modern day heap leaching, which has a relatively low level of energy consumption, is for example. Understanding sulphuric acid leaching of uranium from ore. Precious metals such as gold are extracted from their ores by a cyanide or ozone leaching process. Purification or separation of uranium in carbonate systems.
Heap leaching is a tried and tested mining technique enabling the processing of different kinds of ores which could not otherwise be exploited under viable economic conditions. The cost of the heap leaching process is low, making this process an. Microbial leaching bioleaching, biomining environmental. In addition to the cribs, eight 5m high columns as shown below with an internal diameter of 0. Heap leaching provides mining operators with a benign. It was discovered in the mid s that microorganisms use metals in the cell. A brief note on the heap leaching technologies for the recovery of. Uranium ore leaching pregnant leach liquor ion exchange solvent extraction precipitation. Studies on uranium recovery from a uraniumbearing phosphatic. Bicarbonate leaching of uranium unt digital library. Application of united nations framework classification 2009.
Heap leaching is a wellestablished extractive metallurgical technology enabling the economical processing of various kinds of lowgrade ores, which could not otherwise be exploited. Acid leaching is commonly performed by agitating an ore. Oct 28, 2015 not unlike insitu leach mining, heap leach mining is a process whereby uranium, copper and other precious metals are extracted from ore with a chemical solution. Roasted uranium ores are leached of their uranium values by both acidic and alkaline aqueous solutions. Recovery of uranium from uranium residue by alkaline leaching by bundjoko kweto supervisor.
United states environmental protection agency office of radiation and indoor air 6608t epa 450f17005. While heap leaching was introduced in the uranium industry in the 1950s, when portugal began to use the technology for extraction of uranium from lowgrade uranium ore scheffel, 2002, its an use waned as environmental concerns and low commodity prices made extraction of lowgrade material unattractive, as there were large amounts of high. Column leaching for simulating heap and insitu soil. Hydrodynamic performance critical for heap leach to. For getting one tonne of uranium, a thousand tonne of uranium ore must be handled. Besides copper and uranium, bioleaching technique is also used for extraction of other metals such as nickel, gold, silver, cobalt, molybdenum and antimony. Of late heapleaching methods for extraction of uranium from small deposits of highgrade ores and other deposits of lowgrade ores in outofthe way localities.
Column leaching test was carried out for uranium ore samples obtained from a uranium insitu leaching isl mining site using 2. However, uranium leaching from ore on a large scale is widely practiced in the usa, south africa, canada. Bioleaching of uranium pdf united pdf comunication. Heap leach piles, which consist of ores that have a chemical solution applied to extract uranium. Other important uranium producing countries in excess of 1,000 tons per year are niger, russia, namibia, uzbekistan, china, the. Etango uranium project heap leach demonstration program. Recovery uranium from uraniumbearing waste ore using heap.
Industrialscale experiment on bacterial heap leaching of uranium ore 262 fan baotuan, liu jian, meng yunsheng, niu yuqing. This is much cleaner than the traditional heap leaching using cyanide. The ore can be processed as coarse rock, normally referred to as a dump leach, or as a crushed ore in a heap leach. Heap leaching of gold ore started to gain promenence in the late 1960s when it was applied on a large scale to low grade ores that were uneconomic to procees by conventional tank leach methods. A comparison of the uranium recovery from lowgrade ore by. The cover pictures are of the sierra pintada uranium district in the mendoza province of argentina. The leaching solution is injected into the ore formation to dissolve uranium. Energy information administration 2018 domestic uranium production report iv. Simulation of uranium tailing leaching using vs2drt.
All of these disciplines have made steps forward in modeling the diffusion process and all have pertinent data for the mineral processing of copper heap leaching. Heap leaching and its application to copper, uranium. The chemistry of the leaching process revolves around oxidation of the uranium compounds, which is typically achieved using manganese dioxide mno 2, sodium chlorate. Pdf a brief note on the heap leaching technologies for the. Methods of metal recovery by microorganisms 2 methods. Heap leach developments on low grade ores refractory minerals deemed difficult to leach brannerite, tirich coffinite karoo sandstone acid consumption high due to presence of carbonates calcite and dolomite investigating acid ferric leaching improve rate and extent of uranium dissolution increased acid dosages during agglomeration.
Particular reference is made to the geochemical conditions at crownpoint. Heap leaching is generally economically feasible only for oxide ore deposits. Application of united nations framework classification. Further enhancing project knowledge designed, permitted, constructed and successfully commissioned large scale demonstration plant. For recovery of material occurring naturally in solution, see. Important metals like copper and gold are produced by this. The use of ionexchange recovery in the copper industry is not widesprea d. In addition, in situ leaching of uranium is more sensitive to good engineering management and attention to detail.
National emission standards for operating mill tailings subpart w subpart w. Testing confirms the simple chemistry and efficient leaching nature of the granite host rock and uranium mineralisation. Application of united nations framework classification 2009 unfc2009 for uranium resources uranium ore processing i. Heap leaching of ore is becoming more important as a cost effec tive means of metal extraction. Heap leaching is an industrial mining process to extract precious metals, copper, uranium, and other compounds from ore via a series of chemical. Ore is mined, crushed and dumped onto a leaching pad made from impermeable membrane with a minimum thickness of 1. Wmc copper uranium division copper ore heap leaching. The worldwide production of uranium in 2015 amounted to 60,496 tonnes. Kinetics of uranium leaching the typical leach curve shown in figure 1 indicates that the initial leaching rate is fast but that it decreases with time, and that some of the uranium is very slow leaching or characterization of the leaching properties of a uranium leaching pulp by j.
Introduction in china, acid heap leaching technology has been used increasingly in hard rock uranium mines. Uranium, heap leaching tailings, neutralization, porosity. Some supporting data from studies using alkaline leach for remediation of uranium. Neutralization processing and study of dynamic of acidic. Characterization of the leaching properties of a uranium. T his chapter outlines the basic steps involved in mining, processing, and reclamation that might be suitable for uranium ore deposits in the commonwealth of virginia.
Uranium deposit mineralogy and associated chemistry there are numerous types of uranium minerals in existence, the simplest form being uraninite. Ironand sulfuroxidizing microorganisms are used to release occluded coppergold and uranium from mineral sulfides. Leaching in columns simulates percolation leaching because the conditions are very similar to those in the heap 5. Mineral beneficiation by heap leaching technique in mining. The crushed ore is placed on a leaching pad with a liner. An integrated multiscale approach to heap leaching of uranium. For uranium ore deposits, the choice of mining methods and processing options is very depositspecific and dependent on many variables such as the quality and quantity of the ore, the shape and depth of the ore deposit, site. Nonetheless, heap leaching has also been used to extract uranium from ore at conventional mills, and ionexchange procedures have been used to separate uranium from the liquid extract at both conventional mills and isr facilities. Currently, the nrc regulates active uranium recovery operations in new mexico, and nebraska. Kazakhstan, canada, and australia are the top three producers and together account for 70% of world uranium production.
Acid leaching of agglomerated ore stacked to 5m occurs in four 2m x 2m x 6m leach cribs. For that reason, the nrc regulates in situ recovery facilities as stated above, as well as uranium mills and the disposal of liquid and solid wastes from uranium recovery operations including mill tailings. Recent developments in uranium resources and production. The latter allows simulation of the full scale operation of heap leach pads, as defined in the dfs.
Heap leaching is an extraction process by which chemicals usually sulfuric acid are used to extract the economic element from ore which has been mined and placed in piles on the surface. The leaching agent alkaline, or sulfuric acid is introduced on the top. This is because the recovery of uranium in much higher with heap leaching. Pdf heap leaching technologycurrent state, innovations. This may be done if the uranium contents is too low for the ore to be economically processed in a uranium mill. Uranium leaching with sulphuric acid is a complex process governed by chemical dissolution, and the oxidation of uranium. Uranium is commonly understood as a material storing a huge energy and its only commercial application is as nuclear fuel. Efficiency of bioleaching was studied by varying parameters like pulp density and initial ferrous concentration as source of energy. Pdf conventional heap leaching of uranium ore is neither a new concept historically in the united states, nor is the idea unfamiliar on a. In situ uranium leaching is gaining vast acceptance. An integrated multiscale approach to heap leaching of. Microbial leaching of copper has been widely used in the usa. The uranium bearing pregnant solution can then be recovered through production wells.
The reagents used and the chemistry of leaching are metal. The process initially involves the drilling of holes into the ore. Table of contentsmechanism of thorium leachingprecipitate formationbacterial activitysulphuric acid consumption mechanism of uranium leaching. While it is possible to directly precipitate uranium from. Although usually acidic mine waters were used for ore processing,4 billion liters of freshwater. Bioleaching of lowgrade uranium ore using acidithiobacillus. After 146 days of performance, the slag uranium leaching rate was 55. The front cover shows a general view of the mining area, and the back cover installations for heap leaching. So we try to use continued multicolumns bioleaching in uranium to model multiheaps bioleaching as to improve the production efficiency pf reduce the production cost. However, despite much progress since it was first applied in recent times, the process remains limited by low recoveries and long extraction times. Preconcentration by screening, gravity separation and radiometric sorting can potentially reduce the mass flow to the downstream leach and recovery plants. Heap leachionexchange operations involve the following process.
The first use of cyanide for leaching of gold and silver ores was in england in 1887 by j. Radioactive metals, such as uranium are extracted by the process of acid leaching. For the successful operation of all leaching systems, uranium must either be initially present in the more stable hexavalent state or be oxidized to that state in the leaching process. The goal of the present study was to compare uranium recovery by bioleaching and acid leaching in identical columns under similar process conditions for the same material. In situ leaching isl, solution mining, or in situ recovery isr involves dissolving uranium in the ground and pumping the solution to the surface where the minerals can be recovered.
Phosphate fertilizers as a proliferationrelevant source. Pdf conventional heap leaching of uranium ore in the western. In the case of insitu leaching, no excavation is needed, and the process of leaching is done at the site. Is a technique used in the recovery of copper, salttrona and uranium ores in. In situ microbial leaching is greater acceptance since it eliminates the expense of moving vast amounts of material. Cement, limestone or fly ash are used for heap leaching gold ores with cyanide, and could be considered for alkaline heap leaching of uranium ores or ammonia leaching. The activity ratio of the two uranium isotopes in the pregnant leach solution was measured by. On the other hand, the resulting heap leaching tailings acidic waste water, not only. Uranium bioleaching process is more significant economically. Insitu leaching, also called insitu recovery or solution mining, is a mining process used to recover minerals such as copper and uranium through boreholes drilled into a deposit, in situ. Acid leaching is sometimes also referred to as heap leaching because the leaching process can be performed on large heaps of uranium ore that have been collected from mines.
Mar 09, 2010 the bacterial strain that was used in the leaching experiments was isolated from the jaduguda mine water sample. It is controlled by surface etching, diffusion, and mass transfer within the ore. Uranium leaching is more important than copper, although less amount of uranium is obtained than copper. At the same time, the first modern copper heap leach operation may have been the bluebird copper oxide mine in 1968 bartlett, 1998, followed in the early 1970s by a few other small operations in the western united states. Similar to in situ mining, heap leach mining differs in that it places ore on a liner, then adds the chemicals via drip systems to the ore, whereas in. The study has proven that recovery uranium from uranium bearing waste ore using heap bioleaching is feasible. The influence of uranium mineralogy and the lithology and behaviour of the host rocks means of effecting capital and operating cost reductions, particularly for lower grade deposits flowsheet options for acid leaching and purification flowsheet options for alkaline leaching and purification impact of salinity on the process flowsheet. A brief note on the heap leaching technologies for the.
In the case of heap leaching, the uranium ore is mined, placed on a pad in heaps 530 metres high and irrigated with acid or alkaline solution over many weeks, leaching uranium into the resulting pregnant liquor, which is then collected and treated to extract the uoc. The common methods in the mining world are heap leaching and insitu leaching. Pdf heap leaching is a lowcost technology used in industrial mining to recover precious metals such as gold and uranium, along with several other. In the usa 200 tonnes of copper is recovered per day. Uram conference, vienna 2014 uranium heap leaching 22 the plan 1. Another critical factor was the supply of water for the leaching heaps. Recent developments in uranium resources and production with. In some cases, uranium is extracted from lowgrade ore by heap leaching.
This method has been tested for uranium recovery since 1975 taylor, 1979. The leaching process in mining is carried out either as heap leaching or insitu leaching. For many decades, there has been a growing demand for heap leaching due to its environmental benefits. Request pdf an integrated multiscale approach to heap leaching of uranium ore agglomerates in heap leaching, agglomeration of clay rich ores is commonly used and may prevent plugging phenomena. Based on the current understanding of uranium deposits in the commonwealth of virginia, extraction of uranium ore would use openpit mining, or underground mining, or a combination of both. Heap leach depths have increased to more than 500 ft of ore depth from only 50 to 65 ft a decade ago. Uranium mining is the process of extraction of uranium ore from the ground. In the mineralization under investigation uranium does not form a definite mineral but it is hosted by apatites. For oxide ores, recovery only slightly reduced with. In situ leach isl mining of uranium june 2009 z most uranium mining in the usa and kazakhstan is now by in situ leach methods, also known as in situ recovery isr. Heap leaching is an industrial mining process used to extract precious metals, copper, uranium, and other compounds from ore using a series of chemical reactions that absorb specific minerals and reseparate them after their division from other earth materials. Uranium recovery by heap leaching methods in arizona new mexico wyoming uranium energy corp 6100 indian school rd ne, suite 225 albuquerque, nm 87110 505 830. Studies on uranium recovery from a uranium bearing phosphatic sandstone by a combined heap leaching liquidgel extraction process.
Dr dr groot a dissertation submitted in partial fulfilment of the requirements for the degree of master of applied sciences metallurgy department of materials science and metallurgical engineering faculty of engineering, built environment and information. Heap leaching leaching is a technology to extract pre cious metals, copper, uranium or other combinations from ore via chemical reac tions that absorb specific minerals and then reseparate them after their division from other earth materials. Jun 29, 2019 this is much cleaner than the traditional heap leaching using cyanide. In situ leach works by artificially dissolving minerals occurring naturally in a solid state. This process is dependent on the chemistry of uranium and so is independent on the type of mining system conventional, heap or insitu used. The leaching of uranium from betafite sciencedirect.
Heap leaching process is sometimes preferred instead of the in situ technique. This heap leaching process is applicable for the recovery of rees from. United states environmental protection agency office of radiation and indoor air 6608t epa 450f17005 april 2017. During 1952 and 1953, the plant at urgeirica started a uranium heap leaching process on a commercial scale. Vs2drt is a new reactive transport model for vsaturated porous media. It is observed that the efficiency of bioleaching was 49% at 10% pulp density wv and initial ph 2. Heap leaching experiencebased approach to successful heap.