WO2014150710A1

WO2014150710A1 - System and method for recovery of metal values from metal-bearing materials through leaching

Info

Publication number: WO2014150710A1
Application number: PCT/US2014/024040
Authority: WO
Inventors: Anand Raman; Nitin Goel
Original assignee: Freeport-Mcmoran Corporation
Priority date: 2013-03-15
Filing date: 2014-03-12
Publication date: 2014-09-25
Also published as: ZA201507530B

Abstract

Metal value recovery processes for the recovery of multiple metal values from metal-bearing materials are provided. Processes and methods provided may include the use of multiple leach stages, as well as multiple solvent extraction stages. Raffinates from the solvent extraction stages can be combined to improve metal value recovery.

Description

SYSTEM AM) METHOD FOR RECOVERY OF METAL VALUES FROM METAL- BEARING MATERIALS THROUGH LEACHING FIELD OF INVENTION

The disclosure relates generally to systems and methods for extraction of metal values from metal-bearing materials, and more specifically, to systems and methods for recovering metal values using multiple leaching stages and solvent extraction techniques. BACKGROUND OF THE INVENTION

Hydrometallurgical treatment of metal-bearing materials, such as metal ores, metal- bearing concentrates, and other metal-bearing substances, has been well established for many years. Moreover, leaching of metal-bearing materials is a fundamental process utilized to extract metal values from metal-bearing materials. Typical leach processes comprise contacting a metal-bearing material with an aqueous solution containing a leaching medium that extracts the metal value or metal values from the metal-bearing material into solution. For example, in copper leaching operations, aqueous sulfuric acid is contacted with a copper-bearing ore such as chalcopyrite and chalcocite. During the leaching process, acid in the leach medium can be consumed and various soluble components are dissolved, thereby increasing the metal content of the aqueous solution.

The aqueous leach solution containing the leached metal value can then be treated by, for example, solvent extraction, wherein a desired metal value, such as copper, is targeted for removal from the aqueous leach solution for further processing. In such operations, a raffinate containing significant concentrations of another metal value, which may be referred to as a secondary metal value, such as cobalt, can be produced. Such raffinates can be subjected to other metal value extraction processes, such as, for example, cobalt recovery.

Frequently, metal-bearing materials contain multiple metal values and, depending upon market conditions, it may be desirable to extract multiple metal values from a metal- bearing material. For example, cobalt is found with copper in various locations, and it is often desirable to recover both copper and cobalt. However, systems configured to maximize recovery of a specific metal value, such as copper, may not be efficient in recovering other metal values, such as cobalt. Therefore, a need exists for systems and methods of recovering multiple metal values, such as copper and cobalt. SUMMARY OF THE INVENTION

The present disclosure generally relates to systems and methods for recovery of multiple metal values from metal-bearing materials using, for example, multiple leach stages. In various embodiments, systems and methods in accordance with the present disclosure employ at least two leach stages, as well as multiple solvent extraction stages. As set forth in more detail below, various advantages of the systems and methods of the present disclosure can include improved metal value recovery, in particular where multiple metal values are sought.

An exemplary method for extracting one or more metal values from a metal-bearing solution comprises leaching a metal-bearing material to yield a medium-grade pregnant leach solution and a first solids, subjecting the medium-grade pregnant leach solution to solvent extraction to form medium-grade raffmate, leaching the first solids to yield a second solids, washing the second solids to form a low-grade leach solution, subjecting the low- grade leach solution to solvent extraction to form a low-grade raffmate, and merging at least a portion of the low-grade raffmate and at least a portion of the medium-grade raffmate to yield a combined raffmate. Various embodiments can also comprise adding the combined raffmate to a heap leach to yield a pregnant heap leach solution, subjecting the pregnant heap leach solution to solvent extraction to yield an electrolyte, and subjecting the electrolyte to a cobalt recovery operation.

In accordance with additional embodiments, an exemplary method for recovering one or more metal values from a metal-bearing material comprises leaching a metal-bearing material to yield a solid residue and a high-grade pregnant leach solution, washing the solid residue to form a low-grade leach solution, subjecting the low-grade leach solution to solvent extraction to form a low-grade raffmate, adding the low-grade raffmate to a heap leach to yield a pregnant heap leach solution, subjecting the pregnant heap leach solution to solvent extraction to yield an electrolyte, and subjecting the electrolyte to a cobalt recovery operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, can best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements and wherein:

FIG. 1 illustrates a flow diagram of a metal value recovery method in accordance with various embodiments;

FIG. 2 illustrates a flow diagram of a metal value recovery method in accordance with various embodiments;

FIG. 3 illustrates a flow diagram of a metal value recovery method in accordance with various embodiments;

FIG. 4 illustrates a flow diagram of a metal value recovery system in accordance with various embodiments;

FIG. 5 illustrates a flow diagram of a metal value recovery system in accordance with various embodiments; and

FIG. 6 illustrates a flow diagram of a metal value recovery system in accordance with various embodiments.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description of various embodiments herein makes reference to the accompanying drawing figures, which show various embodiments and implementations thereof by way of illustration, and not of limitation. While these embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, it should be understood that other embodiments can be realized and that mechanical and other changes can be made without departing from the spirit and scope of the present disclosure. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component can include a singular embodiment.

Systems and methods of various embodiments exhibit significant advancements over prior art processes, particularly with regard to metal value recovery and process efficiency. Moreover, existing metal value recovery systems and processes that utilize reactive processes and solvent extraction for metal value recovery can, in many instances, be easily retrofitted to exploit the many commercial benefits of the present invention.

The present disclosure relates, generally, to systems and methods for recovering multiple metal values from metal-bearing materials, and more specifically, to systems and methods for recovering copper and cobalt. In various embodiments, a process for recovering copper and cobalt using, among other things, multiple leach stages and multiple solvent extraction apparatus is provided. These improved systems and methods disclosed herein achieve advancement in the art by, for example, improving metal value recovery yields. In addition, various embodiments reduce the consumption of acid, which reduces reagent cost as well as transportation costs. Reagent transportation costs tend to be high at facilities that are remote from large ports, roads, or railways, and thus a reduction in reagent transportation costs tends to be economically attractive.

In particular, it has been discovered that recovery of copper and cobalt can be conducted using an integrated process. In that regard, recovery of copper and cobalt can be performed by multiple leach and purification stages, wherein portions of the leach and purification stages are in fluid communication with each other.

In addition, it has been discovered that production of copper and cobalt can comprise a primary leaching operation. While various embodiments may be constructed and/or operated in any physical location, it is advantageous to operate various embodiments in close proximity to a primary metal value leaching operation. A primary leaching process may comprise a leaching process that is intended to liberate one or more metal values from a metal-bearing material. For example, in various embodiments, a primary leaching process comprises a leaching process to liberate copper and cobalt from a metal-bearing material that comprises copper and cobalt. By operating in close proximity to a primary metal value leaching operation, certain outputs of various embodiments may be forwarded to the primary leaching process. This allows metal values contained in the metal-bearing material to be retained and further processed, decreasing net loss of metal value, for example, by reducing the amount of metal values sent to tails or residue.

FIG. 1 illustrates an exemplary metal value recovery method 100. In various exemplary embodiments, metal value recovery method 100 is configured to recover multiple metal values from metal-bearing material 101. For example, metal value recovery method 100 can be configured to recover of both copper and cobalt from metal-bearing materials.

Metal -bearing material 101 can comprise, for example, an ore, a concentrate, or any other material from which valuable and/or useful metal values can be recovered. As used herein, the term metal values may include, for example, copper, gold, silver, zinc, platinum group metals, nickel, cobalt, molybdenum, rhenium, uranium, rare earth metals, and the like. By way of a specific example, metal value recovery method 100 is configured to recover copper from copper-bearing material, such as, for example, ores and/or concentrates containing chalcopyrite (CuFeS₂), chalcocite (Cu₂S), bornite (Cu₅FeS₄), and covellite (CuS), malachite (Cu₂C0₃(OH)₂), pseudomalachite (Cu₅[(OH)₂P0₄]2), azurite (Cu₃(C0₃)₂(OH)₂), chrysocolla ((Cu,Al)₂H₂Si2O₅(OH)₄ nH₂0), cuprite (Cu₂0), brochantite (CuS0₄-3Cu(OH)₂), atacamite (Cu₂[OH₃Cl]) and other copper-bearing minerals or materials and mixtures thereof.

In various embodiments, metal value recovery method 100 can be configured to recover a primary metal value and a secondary metal value from metal-bearing material 101. For example, the primary metal value can comprise copper, and the secondary metal value can comprise cobalt.

Prior to leaching step 102, metal-bearing material can undergo various optional preparation processes. In various embodiments, metal-bearing material 101 can be prepared in any manner that facilitates the recovery of metal values from metal -bearing material 101. For example, a composition and/or component concentration of metal-bearing material 101 may be manipulated to render the metal-bearing material more suitable for leaching. Desired composition and component concentration parameters can be achieved through a variety of chemical and/or physical processing stages, the choice of which will depend upon the operating parameters of the chosen processing scheme, equipment cost and material specifications. For example, metal-bearing material 101 can undergo comminution, flotation, blending, and/or slurry formation, as well as chemical and/or physical conditioning before reactive processing. Any processing of metal-bearing material 101 which improves the ability to recover metal values from the material is in within the scope of the present disclosure.

For example, metal-bearing material 101 may be dried, crushed, pulverized, finely ground, or undergo any combination thereof. Ores may be concentrated to form a metal bearing concentrate. A variety of acceptable techniques and devices for reducing the particle size of metal-bearing material 101 are currently available, such as crushers, ball mills, tower mills, ultrafine grinding mills, attrition mills, stirred mills, horizontal mills and the like, and additional techniques may later be developed that may achieve the desired result of increasing the surface area of and exposing mineral surfaces within the material to be processed. In accordance with various embodiments, metal-bearing material 101 can be prepared by controlled wet grinding. Wet grinding tends to reduce capital expenditure and operating expenditures when compared with dry grinding. For example, a uniform, particle size distribution may be achieved. In accordance with one aspect of the present disclosure, a particle size distribution of approximately 80% particle distribution passing size (P₈o) of about 75 microns may be used, as well as a particle size distribution of approximately 98% particle distribution passing size (Pgg) of about 100 to about 200 microns. In accordance with one aspect of the present disclosure, a particle size distribution of approximately 80 % particle distribution passing size (P₈₀) of about 74 microns may be used.

However, in various embodiments, a uniform, ultra-fine particle size distribution is not necessary. For example, in various embodiments, a particle size distribution of approximately 80% particle distribution passing size (P₈₀) of about 100 microns may be used, and in various embodiments a particle size distribution of approximately 98% particle distribution passing size (P 8) of about 100 microns may be used. In various embodiments, metal-bearing material 101 can be subjected crushing and grinding to produce larger and/or less uniform particle sizes which does not comprise controlled grinding. For example, metal-bearing material 101 can be screened through a grizzly or other analogous device with about 250mm openings. Further, metal-bearing material 101 can be subjected to a mill operation. Particles having a size of less than about 250mm can be received by mill operation which then reduces the received particles to a particle size distribution suitable for downstream processing. For example, the mill operation may provide particles having about 80%) particle distribution passing size (Pgo) of 100 microns. Other particle sizes described herein may also be useful.

Additionally, liquid, such as process water, can be added to metal-bearing material 101 to create a pulp density which corresponds to desirable operating conditions of the controlled grinding unit. Acceptable techniques and devices for reducing the particle size of the metal-bearing material include, for example, ball mills, tower mills, grinding mills, attrition mills, stirred mills, horizontal mills and the like, and additional techniques can later be developed that can achieve the desired result of reducing the particle size of the copper- bearing material to be transported.

In various embodiments, after undergoing optional conditioning, metal-bearing material 101 can be subjected to a reactive process, such as a leaching step 102. Leaching step 102 can comprise any leaching process which places metal-bearing material 101 in condition for later metal value recovery processing. Such processes can include, for example, atmospheric leaching, pressure leaching, whole ore leaching, agitation leaching, heap leaching, stockpile leaching, pad leaching, thin-layer leaching and/or vat leaching, at either ambient or elevated temperatures. Any suitable process or reaction that puts metal value in metal-bearing material 101 in a condition such that it can be subjected to later metal value recovery processing is within the scope of the present disclosure.

During step 102, the metal value is solubiiized or otherwise liberated in preparation for later recovery processes. Any substance that assists in solubilizing the metal value, and thus releasing the metal value from a metal-bearing material, can be used. For example, where copper is the metal value being recovered, an acid, such as sulfuric acid, can be contacted with the copper-bearing material such that the copper is solubiiized for later recovery steps. However, it should be appreciated that any suitable method of solubilizing metal value in preparation for later metal value recovery steps is within the scope of the disclosure. For example, in various embodiments, leaching may include the use of a basic leach medium such as ammonia. Moreover, in embodiments using ammonia as a leach medium, ammonium carbonate and/or ammonium sulfate may be added to the leach medium.

In various embodiments, step 102 can comprise, for example, pressure leaching a metal-bearing material 101 to form a first slurry 103. First slurry 103 can undergo, for example, a solid-liquid separation step 104. For example, step 104 can comprise subjecting first slurry 103 to a solid-liquid separation process to form a first pregnant leach solution 105 and a first solids 107. In various embodiments, first pregnant leach solution 105 can comprise between about 5 and about 10 grams per liter of copper. In a preferred embodiment, first pregnant leach solution 105 can comprise between about 6 and about 8 grams per liter of copper.

In various embodiments, step 104 can comprise one or more solid-liquid phase separation techniques, such as, for example, filtration systems, CCD circuits, thickeners, and/or clarifiers. Any manner of separating first pregnant leach solution 105 and first solids 107 from first slurry 103 is within the scope of the present disclosure.

After step 104, in various embodiments, first pregnant leach solution 105 can be subjected to a solvent extraction step 106. In such embodiments, step 106 can comprise subjecting first pregnant leach solution 105 to a process, such as solvent extraction, that isolates and removes a significant portion of a primary metal value, such as copper, from first pregnant leach solution 105. For example, step 106 can comprise a liquid-liquid extraction process. During step 106, metal values from first pregnant leach solution 105 can be selectively loaded into an organic phase in an extraction stage, wherein the organic phase comprises a metal-specific extraction agent such as, for example, an aldoxime and/or ketoxime, to form an aqueous phase and an organic phase. The metal-specific extraction reagent extracts the metal value from the aqueous phase into the organic phase.

The extraction phase of solvent extraction step 106 can produce an aqueous raffinate. The aqueous raffinate from the extraction phase can include metal values, such as copper and/or cobalt, and thus can be treated to recovery such metal values, among others. In various embodiments, step 106 can comprise producing a loaded organic phase and a medium-grade raffinate 1 1 1 in an extraction stage and stripping the loaded organic phase to yield first pregnant leach solution 105. In such embodiments, for example, first electrolyte 109 can comprise copper and medium-grade raffinate 1 1 1 can comprise cobalt. In various embodiments, medium-grade raffinate 1 1 1 can comprise between about 5 g/L and about 8 g/L of acid. In a preferred embodiment, medium-grade raffinate 1 1 1 comprises between about 6 g/L and about 7 g/L of acid.

First electrolyte 109 can, for example, be forwarded to a primary metal value recovery process, such as, for example a primary metal value electrowinning circuit. In various embodiments, first electrolyte 109 comprises copper, which is extracted from the liquid stream through a primary metal value electrowinning circuit.

Method 100 can, for example, comprise a primary metal value electrowinning step 108. In such embodiments, electrolytes such as first electrolyte 109 can be forwarded to a metal value recovery process, such as electrowinning. In various embodiments, step 108 comprises subjecting first electrolyte 109 to a copper electrowinning process.

In various embodiments, medium-grade raffinate 11 1 can be combined with other process streams, as will be discussed in more detail below. Further, at least a portion of medium-grade raffinate 111 can be subjected to a secondary metal value recovery process. For example, medium-grade raffinate 11 1 can be subjected to an electrowinning process to recover cobalt from the liquid solution.

In various embodiments of metal value recovery method 100, first solids 107 can be subjected to leaching step 1 10. In such embodiments, first solids 107 are subjected to a second leach process to further extract desired metal value from the solids. Step 1 10 can comprise, similar to step 102, atmospheric leaching, pressure leaching, whole ore leaching, agitation leaching, heap leaching, stockpile leaching, pad leaching, thin-layer leaching and/or vat leaching, at either ambient or elevated temperatures. Leaching step 1 10 may use an acid leach medium such as sulfuric acid or, in various embodiments, leaching step 1 10 may use a basic leach medium such as ammonia, ammonium carbonate and/or ammonium sulfate. Further, an leaching process that puts metal value in first solids 107 in a condition such that it can be subjected to later metal value recovery processing is within the scope of the present disclosure.

Step 1 10, in various embodiments, produces a second slurry 1 13. Similar to step 104, second slurry 1 13 can undergo, for example, a solid-liquid separation step 112. For example, step 1 12 can comprise subjecting second slurry 1 13 to a solid-liquid separation process to form a second pregnant leach solution 1 15 and a second solids 127. In various embodiments, step 112 can comprise one or more solid-liquid phase separation techniques, such as, for example, filtration systems, CCD circuits, thickeners, and/or clarifiers. Any manner of separating second pregnant leach solution 115 and second solids 127 from second slurry 113 is within the scope of the present disclosure.

In various embodiments, second pregnant leach solution 1 15 is subjected to a solvent extraction step 114. For example, step 114 can comprise subjecting second pregnant leach solution 1 15 to a solvent extraction process to produce high-grade raffinate 1 17 and a second electrolyte 129. Similar to step 106, step 114 can comprise a process, such as solvent extraction, that isolates and removes a significant portion of a primary metal value, such as copper, and a secondary metal value, such as cobalt, from second pregnant leach solution 1 15. For example, step 114 can comprise a liquid-liquid extraction process, wherein metal values from second pregnant leach solution 1 15 can be selectively loaded into an organic phase in an extraction phase, wherein the organic phase comprises an extracting agent to aid in transporting the metal values to the organic phase. The extraction phase can produce an aqueous raffinate, such as high-grade raffinate 117. The raffinate from the extraction phase can include metal values, such as copper and/or cobalt, and thus can be treated to recovery such metal values, among others. In various embodiments, for example, second electrolyte 129 can comprise copper and high-grade raffinate 117 can comprise cobalt.

Similar to first electrolyte 109, second electrolyte 129 can, for example, be forwarded to primary metal value electrowinning step 108. In various embodiments, second electrolyte 129 comprises copper, which may be extracted from the liquid stream through primary metal value electrowinning step 108.

In various embodiments, high-grade raffinate 117 can be forwarded to various other steps for further processing, or to assist in the operation of those steps. For example, a portion of high-grade raffinate 1 17 can be returned to leaching step 1 10 to assist in leaching first solids 107. A portion of high-grade raffmate 1 17 can also be mixed with other process streams, as will be discussed in more detail below.

In various embodiments, second solids 127, which were formed in step 110, can be subjected to further processing. For example, second solids 127 can undergo a wash solids step 1 18, in which a wash solution is provided to second solids 127. Step 1 18 can produce a solution containing primary and or secondary metal value, such as a washed solution 1 19.

Washed solution 1 19 can, for example, be forwarded to solvent extraction step 120. In various embodiments, step 120 comprises subjecting washed solution 1 19 to a solvent extraction process. In such embodiments, step 120 can be employed to form a low-grade raffmate 121 and a low-grade electrolyte 131. Low-grade electrolyte 131 can, for example, be forwarded to primary metal value electrowinning step 108. In various embodiments, low-grade raffmate 121 can comprise between about 12 g/L and about 16 g/L of acid. In a preferred embodiment, low-grade raffmate 121 comprises about 15 g/L of acid.

Further, washed solution 1 19 can be fortified by mixing it with other process streams prior to a leaching step 122. For example, a portion of high-grade raffmate 1 17 can be mixed with washed solution 1 19 prior to step 122. In various embodiments, mixing other process streams with washed solution 119 can increase the concentration of a primary and/or secondary metal value in washed solution 1 19.

In various embodiments, low-grade raffmate 121 can be subjected to a secondary metal value recovery step 1 16. Step 1 16 can comprise, for example, a cobalt electrowinning process. In various embodiments, low-grade raffmate 121 comprises cobalt, and at least a portion of the cobalt is extracted from the liquid solution through step 116.

Further, a portion of low-grade raffmate 121 can be forwarded for use in leaching step 122. In various embodiments, leaching step 122 comprises a heap leach of a second metal-bearing material 133. Second metal-bearing material 133 can comprise, for example, previously processed materials such as mine tailings. In such embodiments, step 122 can produce a third leach solution 123.

In various embodiments, third leach solution 123 can be forwarded to solvent extraction step 124. Step 124 can comprise, for example, subjecting third leach solution 123 to a solvent extraction process. As previously discussed, solvent extraction can produce an electrolyte solution comprising a desired metal value. In various embodiments, step 124 produces a third electrolyte 125 comprising cobalt. In such embodiments, third electrolyte 125 can be forwarded to secondary metal value electrowinning step 116. In various embodiments, third electrolyte 125 comprises between about 5 and about 10 grams per liter of cobalt. In a preferred embodiment, third electrolyte 125 comprises about 6 grams per liter of cobalt.

With reference to Figure 2, a method of recovering metal value 200 is illustrated, in various embodiments, method 200 comprises many of the same steps as method 100 as depicted in Figure 1. For example, method 200 can comprise all the steps of method 100 except for leaching step 122 and solvent extraction step 124. In such embodiments, method 200 may not comprise forwarding a portion of a low-grade raffinate 121 to a step such as step 122, and may not comprise providing a third electrolyte 125 to step 116.

With reference to Figure 3, a method of recovering metal value 300 is illustrated. In various embodiments, method 300 comprises many of the same steps as method 100 as depicted in Figure 1. For example, method 300 can comprise all the steps of method 100 except for leaching step 102, solid-liquid separation step 104, solvent extraction step 106, and primary metal value electrowinning step 108. In such embodiments, method 300 may not comprise forwarding a first solids to leaching step 1 10 and forwarding a medium-grade raffinate to steps such as step 1 16 and/or step 122.

With reference to Figure 4, a system for recovering metal value 400 is illustrated. In various embodiments, system 400 comprises a system for recovering metal value in accordance with method 100, illustrated in Figure 1. However, any system, including system 400, capable of performing method 100 is within the scope of the present disclosure.

In various embodiments, system 400 comprises a primary leach vessel 430. A metal- bearing material, such as metal-bearing material 101, can be provided to primary leach vessel 430. Primary leach vessel 430 can comprise, for example, an autoclave capable of pressure leaching copper and/or cobalt from metal-bearing material 101 to produce first slurry 103.

System 400 can further comprise, for example, a solid-liquid separation apparatus 432. In various embodiments, solid-liquid separation apparatus 432 can comprise filtration systems, CCD circuits, thickeners, clarifiers, and the like. In various embodiments, solid- liquid separation apparatus 432 is capable of receiving first slurry 103 and producing first solids 107 and first pregnant leach solution 105. Any solid-liquid separation apparatus capable of producing first solids 107 and first pregnant leach solution 105 from a slurry is within the scope of the present disclosure. In various embodiments, system 400 can further comprise medium-grade solvent extraction apparatus 434. Medium-grade solvent extraction apparatus 434 can be capable of receiving first pregnant leach solution 105 and producing medium-grade raffinate 1 1 1. In various embodiments, medium-grade solvent extraction apparatus 434 produces a first electrolyte 109. Any apparatus capable of producing medium-grade raffinate 11 1 from first pregnant leach solution 105 is within the scope of the present disclosure.

System 400 can further comprise, for example, a secondary leach vessel 436. A metal-bearing material, such as first solids 107, can be provided to secondary leach vessel 436. In various embodiments, secondary leach vessel 436 comprises an autoclave capable of pressure leaching copper and/or cobalt from first solids 107 to produce a second slurry 1 13.

In various embodiments, system 400 comprises a solid-liquid phase separation apparatus 438. For example, second slurry 1 13 can be forwarded to solid-liquid phase separation apparatus 438 to form second solids 127 and second pregnant leach solution 1 15. Solid-liquid separation apparatus 432 can comprise, for example, filtration systems, CCD circuits, thickeners, clarifiers, and the like capable of producing second solids 127 and second pregnant leach solution 1 15. Any solid-liquid separation apparatus capable of producing second solids 127 and second pregnant leach solution 1 15 from a slurry is within the scope of the present disclosure.

System 400 can further comprise, for example, a high-grade solvent extraction apparatus 440. In various embodiments, high-grade solvent extraction apparatus 440 is capable of receiving second pregnant leach solution 115 and producing high-grade raffinate 117. High-grade raffinate 1 17 can be useful in other system operations. For example, in various embodiments, at least a portion of high-grade raffmate 117 can be forwarded to secondary leach vessel 436 to assist in leaching first solids 107. In various embodiments, at least a portion of high-grade raffinate 117 can be mixed with washed solution 1 19 to improve the profile and metal value concentration of washed solution 1 19 prior to solvent extraction.

In various embodiments, system 400 can further comprise a wash stage 442. For example, wash stage 442 can be configured to receive second solids 127 and a wash solution. In various embodiments, a wash solution can be provided to wash stage 442 from other system components. As will be described below, a lean electrolyte 137 can be provided to wash stage 442. In various embodiments, wash stage 442 can form a washed solution 1 1 9. Washed solution 1 19 can comprise, for example, metal value washed from second solids 127. System 400 can comprise, for example, a solid-liquid separation apparatus configured to separate washed solution from second solids 127. In various embodiments, after separation from second solids 127, washed solution 1 19 is subjected to further processing to remove metal value, such as copper and/or cobalt.

System 400 can further comprise, for example, a low-grade solvent extraction apparatus 448. In various embodiments, low-grade solvent extraction apparatus 448 can be configured to receive a solution containing a relatively low concentration of a metal value, such as washed solution 1 19. In such embodiments, low-grade solvent extraction apparatus 448 can be configured to produce low-grade raffinate 121. At least a portion of low-grade raffinate 121 can, for example, be forwarded to primary leach vessel 430 and/or secondary leach vessel 436. In various embodiments, a portion of low-grade raffinate 121 can be mixed with a portion of medium-grade raffinate to form a combined raffinate. In various embodiments, the combined raffinate can comprise between about 9 g/L and about 12 g/L of acid. In a preferred embodiment, the combined raffinate comprises between about 9 g/L and about 10 g/L of acid. Further, as will be discussed below, at least a portion of low-grade raffinate 121 can be forwarded for further processing.

In various embodiments, system 400 further comprises a heap leach stage 452. For example, heap leach stage 452 can leach metal-bearing material that has been previously subjected to metal value recovery processes, such as mine tailings. In various embodiments, process streams such as low-grade raffinate 121, medium-grade raffinate 1 1 1, and/or a combined raffmate can be forwarded to heap leach stage 452 to assist in leaching of the metal-bearing material. Heap leach stage 452 can be configured, for example, to produce third leach solution 123 containing cobalt and/or copper.

System 400 can further comprise, for example, a solvent extraction apparatus 454. In various embodiments, solvent extraction apparatus 454 can be configured to receive third leach solution 123 and produce third electrolyte 125. Third electrolyte 125 can, for example, be forwarded for further processing. In various embodiments, third electrolyte 125 can comprise between about 1 g/L and about 3 g/L of acid. In a preferred embodiment, third electrolyte 125 comprises between about 2 g/L and about 3 g/L of acid.

In various embodiments, system 400 can further comprise a secondary metal value electrowinning circuit 450. For example, secondary metal value electrowinning circuit 450 can comprise an electrowinning circuit suitably designed to carry out any electrow inning process capable of producing a metal cathode product such as, for example, a cobalt cathode product. In such configurations, secondary metal value electrowinning circuit 450 can be configured to receive third electrolyte 125. In various embodiments, secondary metal value electrowinning circuit 450 can produce a lean electrolyte 131. For example, lean electrolyte 131 can be forwarded to other system components, such as wash stage 442.

With reference to Figure 5, a metal value recovery system 500 is illustrated. In various embodiments, system 500 comprises many of the same steps as system 400 as depicted in Figure 4. For example, system 500 can comprise all of the components of system 400 except for the heap leach stage 452 and/or solvent extraction apparatus 454. In such embodiments, system 500 does not comprise forwarding a portion of third electrolyte 125 to secondary metal value electrowinning circuit 450.

With reference to Figure 6, a metal value recovery system 600 is illustrated. In various embodiments, system 600 comprises many of the same steps as system 400 as depicted in Figure 4. For example, system 600 can comprise all the components of system 400 except for the primary leach vessel 430, solid-liquid separation apparatus 432, and/or medium-grade solvent extraction apparatus 434. In such embodiments, system 600 may not comprise forwarding first solids 107 to secondary leach vessel 436 and providing medium- grade raffmate 1 15 to heap leach stage 452.

It is believed that the disclosure set forth above encompasses at least one distinct invention with independent utility. While the invention has been disclosed in the exemplary forms, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. The subject matter of the invention includes all novel and non-obvious combinations and sub combinations of the various elements, features, functions and/or properties disclosed herein and their equivalents.

The method and system described herein can be implemented to recover copper and other metals in a controlled manner. Other advantages and features of the present systems and/or methods can be appreciated from the disclosure herein and the implementation of the method and system.

Claims

CLAIMS What is claimed is:

1. A method comprising:

leaching a metal-bearing material to yield a medium-grade pregnant leach solution and a first solids;

subjecting the medium-grade pregnant leach solution to solvent extraction to form medium-grade raffinate;

leaching the first solids to yield a second solids;

washing the second solids to form a low-grade leach solution; subjecting the low-grade leach solution to solvent extraction to form a low- grade raffinate; and

merging at least a portion of the low-grade raffinate and at least a portion of the medium-grade raffinate to yield a combined raffinate.

2. The method of claim 1, further comprising:

adding the combined raffmate to a heap leach to yield a pregnant heap leach solution;

subjecting the pregnant heap leach solution to solvent extraction to yield an electrolyte; and

subjecting the electrolyte to a cobalt recovery operation.

3. The method of claim 1, wherein the medium-grade raffinate is between about 5 g/L and 8 g/L acid.

4. The method of claim 1, wherein the low-grade raffinate is between about 12 g/L and 16 g/L acid.

5. The method of claim 1 , wherein the combined raffinate is between about 9 g/L and 12 g/L acid.

6. The method of claim 2, further comprising subjecting the combined raffinate to the cobalt recovery operation.

7. The method of claim 1, wherein the medium-grade raffmate is between about 5 g/L and 8 g/L acid.

8. The method of claim 1, wherein the low-grade raffmate is between about 12 g/L and 16 g/L acid.

9. The method of claim 2, wherein the electrolyte is between about 1 g/L and 3 g/L acid.

10. The method of claim 1, wherein the leaching the first solids yields a high- grade pregnant leach solution.

1 1 . The method of claim 10, further comprising subjecting the high-grade pregnant leach solution to solvent extraction to yield a high-grade raffmate.

12. The method of claim 11, further comprising bleeding a portion of the high- grade raffmate to the low-grade leach solution.

13. The method of claim 1, wherein the metal-bearing material comprises copper and cobalt.

14. A method comprising:

leaching a metal-bearing material to yield a solid residue and a high-grade pregnant leach solution;

washing the solid residue to form a low-grade leach solution; subjecting the low-grade leach solution to solvent extraction to form a low- grade raffmate;

adding the low-grade raffmate to a heap leach to yield a pregnant heap leach solution;

subjecting the electrolyte to a cobalt recovery operation.

15. The method of claim 14. wherein the low-grade raffinate is between about 12 g/L and 16 g/L acid.

16. The method of claim 14, wherein the electrolyte is between about 1 g/L and 3 g/L acid.

17. The method of claim 14, further comprising subjecting the high-grade pregnant leach solution to solvent extraction to yield a high-grade raffinate.

18. The method of claim 17, further comprising bleeding a portion of the high- grade raffinate to the low-grade leach solution.

19. The method of claim 14, wherein the metal-bearing material comprises copper and cobalt.