Patent Application
20140262817
The present invention relates, generally, to systems and methods for recovering metal values from metal-bearing materials, and more specifically, to systems and methods for recovering cobalt and other metal values.
Cobalt is an industrially important element that may be used in various catalysts, dyes, alloys, inks, battery additives, and other industrially beneficial products. Cobalt may be found in nature in a variety of forms and in a variety of ores. Cobalt containing ores include cobaltite, heterogenite (CoOOH), erythrite, glaucodot, and skutterudite. As found in nature, cobalt often exists in an oxidation state other than zero. For example, cobalt is often found in the form of cobalt II and cobalt III. Cobalt metal is commercially saleable, though purified forms of cobalt II and/or cobalt III, such as those in a salt form, are also commercially saleable.
In conventional processes, cobalt containing materials precipitated with magnesium oxide (MgO) and subsequently leached tend to be difficult to filter. In addition, large volumes of aqueous solution are typically employed. More efficient systems and methods for cobalt recovery would be commercially and industrially advantageous. In addition, it would be commercially and industrially advantageous to produce both cobalt metal and ionic cobalt.
Accordingly, the present invention provides systems and methods for metal value recovery, such as cobalt recovery. In various embodiments, a method is provided comprising leaching a cobalt bearing material to form a slurry, filtering the slurry to yield solids and a cobalt bearing liquid phase, and forwarding the solids to a second leaching operation.
In various embodiments, a method is provided comprising adding magnesia to a cobalt bearing material to form a first slurry, separating the first slurry into a saleable solid product and a liquid phase, adding lime to the liquid phase to form a second slurry, and separating the second slurry into a solid product and a liquid phase.
Further areas of applicability will become apparent from the detailed description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present invention.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present invention, however, may 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:
The following description is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. The description of specific examples indicated in various embodiments of the present invention are intended for purposes of illustration only and are not intended to limit the scope of the invention disclosed herein. Moreover, recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the stated features.
Furthermore, the detailed description of various embodiments herein makes reference to the accompanying drawing figures, which show various embodiments by way of illustration. While the embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that logical and mechanical changes may be made without departing from the spirit and scope of the present invention. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, steps or functions recited in descriptions any method, system, or process, may be executed in any order and are not limited to the order presented. Moreover, any of the step or functions thereof may be outsourced to or performed by one or more third parties. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component may include a singular embodiment.
The present invention relates, generally, to systems and methods for recovering metal values from metal-bearing materials, and more specifically, to systems and methods for selective proximity recovery of cobalt. Various embodiments of the present invention provide a process for recovering cobalt that varies in accordance with, among other things, proximity to a primary metal value recovery operation. In various embodiments, it has been discovered that various methodologies of cobalt recovery may be used to advantageously affect the recovery of a primary metal value. Moreover, in various embodiments, it has been discovered that various methodologies of cobalt recovery may be used to advantageously improve the recovery of cobalt, for example, in operations that are not in close proximity to a primary metal value recovery operation.
Metal values such as, for example, copper, gold, silver, zinc, platinum group metals, nickel, cobalt, molybdenum, rhenium, uranium, rare earth metals, and the like, may be recovered from metal-bearing materials in accordance with various embodiments of the present invention. A primary metal value may refer to a metal value that is recovered from a metal-bearing material. A secondary metal value (and tertiary metal values, etc) may also be obtained from the metal-bearing material. While any metal value may be deemed to be a primary metal value, typically a primary metal value will be present in the metal-bearing material in a greater concentration than a secondary metal value. For example, in various embodiments, copper may be considered a primary metal value and cobalt may be considered a secondary metal value.
A primary metal value recovery operation may refer to any metal value recovery operation that seeks to recover a primary metal value. For example, a primary metal value recovery operation may include a leaching operation (e.g., a primary metal leach) that produces a pregnant leach stream containing a primary metal value.
A primary metal value recovery operation may be operated in close proximity to a cobalt recovery operation. Close proximity refers to a distance within which it would be reasonable to transport metal value bearing materials between the primary metal value recovery operation and the cobalt recovery operation. For example, close proximity may refer to a portion of the primary metal value recovery operation existing within 50 km of the cobalt recovery operation, within 25 km of the cobalt recovery operation, and within 5 km or fewer of the cobalt recovery operation.
It has been discovered that cobalt may be recovered using a bagged anode electrowinning process, which may be advantageous where a primary metal value recovery operation is operated not in close proximity to a cobalt recovery operation. It has also been discovered that cobalt may be recovered using electrodes that are not sequestered, which may be advantageous where a primary metal value recovery operation is operated in close proximity to a cobalt recovery operation.
In various embodiments, a primary metal value recovery operation operated in close proximity to a cobalt recovery operation may receive one or more output streams from the cobalt recovery operation. Such output stream may contain the primary metal, enhancing recovery of the primary metal value. Moreover, in such a manner, media (e.g., acid) and/or reagents may be conserved.
With reference to
Cobalt bearing material 102 may be an ore (cobaltite, heterogenite (CoOOH), erythrite, glaucodot, skutterudite, other cobalt containing ores, and mixtures of cobalt containing ores with ores bearing other metal values), a concentrate, a process residue, an impure metal salt, a preprocessed cobalt bearing material, combinations thereof, or any other material from which cobalt values are present. Cobalt, whether in metal or ionic form, may be recovered from cobalt bearing material 102 in accordance with various embodiments of the present invention. In various embodiments, cobalt bearing material 102 contains other metal values, such as precious metals (e.g., gold, silver and platinum) and copper. Various aspects and embodiments of the present invention, however, prove especially advantageous in connection with the recovery of cobalt from a preprocessed cobalt bearing material. A preprocessed cobalt bearing material may comprise a material that has been subjected to a prior metallurgical process. For example, a metallurgical process may result in the formation of cobalt hydroxide Co(OH)2. Cobalt hydroxide may be formed by combining a cobalt bearing material with magnesium oxide (MgO) and/or lime. It should be appreciated that a preprocessed cobalt bearing material may contain various other constituents as impurities or coprecipitates, such as copper, zinc, manganese and/or nickel. In various embodiments, cobalt bearing material 102 comprises cobalt hydroxide. In various embodiments, cobalt bearing material 102 comprises cobalt hydroxide produced by addition of magnesium oxide to a material containing cobalt ions. In various embodiments, cobalt bearing material 102 comprises cobalt hydroxide produced by addition of lime to a material containing cobalt ions. In various embodiments, cobalt bearing material 102 comprises cobalt hydroxide produced by addition of lime and/or magnesium oxide. Cobalt produced using magnesium oxide is generally considered of greater quality than cobalt produced using lime, though various factors, including reagent costs, may affect the selection of an appropriate cobalt bearing material.
With continued reference to
In accordance with various embodiments, reactive processing 104 may comprise any type of reactive process that is capable of yielding cobalt in cobalt bearing material 102 in a condition to be subjected to later metal recovery steps. For example, in various embodiments, reactive processing 104 comprises a leaching operation. In various embodiments, reactive processing 104 yields cobalt bearing reactive processed material 105, described in detail herein below.
Cobalt bearing reactive processed material 105 may be directed to filtration 106. Filtration 106 may comprise any suitable filtration process. For example, vacuum filters such as a bat filter may be used. In addition, pressure filters such as a plate and frame filter may be used.
Filtration 106 may separate the cobalt bearing reactive processed material 105 into a solid phase and a liquid phase. The solid phase is sent to primary leaching process 120. Primary leaching process 120 may comprise a leaching process that is intended to liberate one or more metals from a metal bearing material. For example, in various embodiments, primary leaching process 120 comprises a leaching process that tends to liberate copper from a copper bearing material. The liquid phase of cobalt bearing reactive processed material 105 comprises filtrate 107. Filtrate 107 is forwarded to conditioning 108.
In various embodiments, conditioning 108 comprises one or more chemical and/or physical processing steps. The filtrate 107 may be conditioned to adjust the composition, component concentrations, solids content, volume, temperature, pressure, and/or other physical and/or chemical parameters to desired values and thus to form a suitable copper-bearing solution. Generally, a properly conditioned copper-bearing solution will contain a relatively high concentration of soluble copper, for example, copper sulfate, in an acid solution and preferably will contain few impurities. Moreover, the conditions of the copper-bearing solution preferably are kept substantially constant to enhance the quality and uniformity of the copper product ultimately recovered. In various embodiments, conditioning 108 comprises a solution extraction operation.
In various embodiments, conditioning 108 produces conditioned solution 118 and conditioned solution 116. Conditioned solution 118 may be forwarded to precipitation and filtration 112.
Precipitation and filtration 112 may comprise a filtration process wherein a reagent is added to selectively precipitate cobalt. Precipitation and filtration 112 may comprise a precipitation that includes the use of a variety of precipitants, including, for example, calcium compounds such as gypsum (calcium sulfate), lime (calcium hydroxide and/or calcium oxide), calcium carbonate and milk of lime (certain preparations of calcium hydroxide). In various embodiments, any suitable source of gypsum or lime may be used in precipitation and filtration 112. For example, lime and gypsum may be added to precipitation and filtration 112 to precipitate cobalt as cobalt gypsum (“CoGyp”). Precipitation and filtration 112 thus produces precipitated cobalt 114. Precipitated cobalt 114 may be passed to reactive process 104.
Conditioned solution 116 may be passed to further processing 110. Further processing 110 may comprise any metal recovery process, such as ion exchange, electrowinning, solution extraction, carbon column filtering, and combinations thereof. Further processing may yield cobalt metal.
As shown in metal recovery process 100, the connection to primary leaching process 120 allows for greater efficiency and efficacy in the recovery of a primary metal. For example, a primary metal may be contained in Co MAT 102. As cobalt is further refined and recovered, the primary metal may be separated from cobalt and recovered itself in another process, such as primary leaching process 120.
With reference to
Leach 202 may comprise leaching may be any method, process, or system that enables cobalt to be leached from cobalt bearing material 102. Typically, leaching utilizes acid to leach cobalt from cobalt bearing material 102. Basic (i.e., caustic) leaches may be used, however. For example, leaching can employ a leaching apparatus such as for example, a heap leach, a vat leach, a tank leach, a simultaneous grind-leach apparatus, a pad leach, a leach vessel or any other leaching technology, known to those skilled in the art or hereafter developed, that is useful for leaching cobalt from cobalt bearing material 102.
In accordance with various embodiments, leaching may be conducted at any suitable pressure, temperature, and/or oxygen content. Leaching can employ one of a high temperature, a medium temperature, or a low temperature, combined with one of high pressure, or atmospheric pressure. Leaching may utilize conventional atmospheric or pressure leaching, for example, but not limited to, low, medium or high temperature pressure leaching. As used herein, the term “pressure leaching” refers to cobalt recovery process in which material is contacted with an acidic or a basic solution and oxygen under conditions of elevated temperature and pressure. Medium or high temperature pressure leaching processes which are generally thought of as those processes operating under acidic conditions at temperatures from about 120° C. to about 190° C. or up to about 250° C.
Leach 202 is conducted in acid media under the addition of sulfur dioxide gas. Leach 202 may be performed under pressure and at temperatures above 25° C., though in various embodiments, leach 202 is conducted at atmospheric temperature and ambient temperature. Leach 202 yields leachate 203 that is forwarded to filtration 106. Sulfur dioxide addition acts to reduce cobalt III into cobalt II, which is more easily dissolved into solution.
Solution extraction 204 is configured to selectively extract impurities, as described in further detail herein. In various embodiments, solution extraction 204 comprises a liquid-liquid extraction. During solution extraction 204, impurities from the filtrate 205 may be loaded selectively into an organic phase in an extraction stage. Impurities may include one or more of copper, zinc, manganese and nickel. In various embodiments, the organic phase comprises an extracting agent, which may also be referred to as an extractant, to aid in transporting the impurities to the organic phase. For example, Di-(2-ethylhexyl)phosphoric acid (D2EHPA) may be used as an extracting agent. Cobalt is retained in the aqueous phase and Zn, Mn, and Ca are loaded in the organic phase.
The organic phase from solution extraction 204 may be then subjected to one or more wash stages in which the loaded organic phase is contacted with an aqueous phase in order to remove aqueous cobalt bearing solution droplets from the organic phase. However, in various embodiments, a wash stage is not included. The organic phase may then be subject to a solvent stripping stage, wherein the impurities are transferred to an aqueous phase. For example, more acidic conditions may shift the equilibrium conditions to cause the impurities to migrate to the aqueous phase. The aqueous phase, which contains the impurities, may be processed in a suitable manner. The organic phase is thus purged of impurities and, in various embodiments, may be contacted again with liquids from liquid phase. Conditioned solution 118 thus comprises cobalt containing liquid from solution extraction 204.
Upstream bleed 206 comprises a portion of filtrate 205. Upstream bleed 206 may be used to bleed a portion of filtrate 205 to precipitation and filtration 112, thus bypassing solution extraction 204. Upstream bleed 206 allows for the reduction of impurities from the circuit and for the reduction in process volumes in downstream processing. For example, leachate 203 from leach 202 may be of relatively low cobalt concentration. Upstream bleed 206 provides a portion of the liquid phase of leachate 203 to precipitation and filtration 112, allowing the cobalt to be precipitated and the cobalt-depleted liquid phase with the impurities to be sent to elsewhere (e.g., to tails). Stated another way, upstream bleed 206 acts to reduce solution volumes, in turn reducing the volume of solution that is subject to other metal recovery processes. By reducing volume prior to other processing steps, the volume of solution used in the other processing steps relative to the cobalt contained therein is lower than in conventional systems. Accordingly, process equipment may be downsized as the equipment need not be sized to accommodate a large volume of low cobalt concentration liquor. The reduction in equipment size is also a cost savings over conventional systems on a per mass unit of cobalt recovered basis.
With reference to
As discussed above, cobalt bearing material 102 may be produced in proximity to other metallurgical operations. For example, certain mining operations recover more than one metal from an ore body. Certain ore bodies comprise cobalt and copper, among other metals. Copper may be leached in a primary leaching operation. During the processing of the leachate from such a primary leaching operation, it may be beneficial to begin cobalt recovery. For example, cobalt bearing solution 303 may originate from primary metal recovery 304. In various embodiments, cobalt bearing solution 303 may comprise a raffinate from a solution extraction process.
Cobalt bearing solution 303 may be forwarded to cobalt precipitation 302. Cobalt precipitation 302 may comprise any process by which cobalt is precipitated out of solution using a precipitating agent. A precipitant or precipitating agent, used herein interchangeably, is an agent that, when added to a solution, causes at least a portion of a solute to precipitate. A variety of precipitating agents may be used to precipitate metal values. Any agent that may precipitate a metal value from an aqueous solution may be used as a precipitating agent. Precipitating agents may include various hydroxides and carbonates. More specifically, precipitating agents may include magnesium hydroxide, lime, magnesium oxide (also known in the art as magnesia), ammonium hydroxide, potassium hydroxide, calcium carbonate, ammonium sulphate, sodium carbonate, magnesium carbonate, potassium, and sodium hydroxide. In an exemplary embodiment, any form of magnesium oxide may be used as a precipitating agent. For example, forms of magnesium oxide include solid magnesium oxide, calcined magnesium oxide and slurried, calcined magnesium oxide. Cobalt precipitation 302 may comprise multiple precipitation steps performed in parallel or in series.
The use of one precipitant over another is determined based on a number of factors. As discussed above, cobalt produced using magnesium oxide is generally considered of greater quality than cobalt produced using lime. Generally speaking, industrially produced cobalt hydroxide using magnesium is approximately 30%-45% pure, whereas industrially produced cobalt hydroxide using lime is approximately 10%-25% pure. Cobalt hydroxide is a commercially marketable product, so the desired return on investment may be weighed using the present or predicted market price of both materials. Thus, it may be beneficial in operations that produce both products to adjust the balance of the type and amount of cobalt hydroxide that is recovered and the type and amount of cobalt hydroxide that is marketed directly. Solids 301 from cobalt precipitation 302 may be used as cobalt bearing material 102. Cobalt metal is obtained in electrowinning 308.
Primary leach 120 may output a primary metal bearing solution 305 to be forwarded to primary metal recovery 304. Primary metal recovery 304 may comprise one or more processes that tend to recover a primary metal value. For example, primary metal recovery 304 yields primary metal value 306.
With reference to
Leachate from a primary metal leach is subject to solution extraction, and the raffinate is subject to cobalt precipitation 402. Cobalt precipitation 402 comprises the addition of a precipitating agent such as magnesia, lime, and/or other precipitating agents to the raffinate solution. The resultant slurry 403 that forms in cobalt precipitation 402 is subject to cobalt leach 404.
Cobalt leach 404 is conducted in acid media under the addition of sulfur dioxide gas, though any suitable reducing agent may be used in lieu of or with sulfur dioxide gas. Sulfur dioxide addition acts to reduce cobalt III into cobalt II, which is readily dissolved into solution. Cobalt leach 404 may be performed under pressure and at temperatures above 25° C., though in various embodiments, cobalt leach 404 is conducted at atmospheric pressure and at a temperature of about 50° C. Cobalt leach 404 yields a leachate that is forwarded to filtration 408. Acid may also be added to cobalt leach 404 from time to time.
Filtration 408 separates the slurry output of cobalt leach 404 into a solid phase and a liquid phase. Filtration 408 comprises filtering the slurry output of cobalt leach 404 in the presence of gypsum. It has been found that gypsum added via lime as a precipitant in one of the process stages tends to act as a suitable filtering aid, in addition to providing various other benefits.
Solid phase output 430 of filtration 408 is sent to a primary leaching process. Primary leaching process comprises a leaching process that is intended to liberate one or more metals 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
A first portion of the liquid phase output of filtration 408 is bled as bleed 412 to precipitation and filtration 410. A second portion of the liquid phase output of filtration 408 is forwarded to Zn/Mn/Ca SX 406. Zn/Mn/Ca SX 406 comprises a solution extraction process that removes, among other things, Zn, Mn, and Ca from the liquid portion output of filtration 408. The aqueous liquid portion of the liquid portion output of filtration 408 may be contacted with an organic solution and an extractant.
Zn/Mn/Ca SX 406 uses D2EHPA as an extractant. After impurities are brought in the organic phase, the organic phase may be washed with water, though in various embodiments the organic phase is not washed. The organic phase may be scrubbed with dilute sulfuric acid to strip any cobalt that was extracted from the aqueous phase. After scrubbing, the dilute sulfuric acid, which now contains cobalt scrubbed from the organic phase, may be sent back to precipitation and filtration 112 via scrubbed cobalt solution 470. The organic phase may be stripped with an additional aqueous phase to bring impurities to the aqueous phase. The additional aqueous phase may be suitably treated. Acid for stripping the organic phase may be generated from other processes, for example, raffinate from undivided electrowinning 422 or other acidic streams from the primary metal recovery process. The aqueous phase Zn/Mn/Ca SX 406 produces may be referred to as extracted cobalt bearing solution 409.
A portion of extracted cobalt bearing solution 409 is forwarded to precipitation and filtration 410. Precipitation and filtration 410 comprises a filtration process wherein a reagent is added to selectively precipitate cobalt. Precipitation and filtration 410 may comprise a precipitation that includes the use of a variety of precipitants, including, for example, calcium, lime (calcium hydroxide and/or calcium oxide), calcium carbonate and milk of lime (certain preparations of calcium hydroxide). In various embodiments, any suitable source of gypsum or lime may be used in precipitation and filtration 410. For example, lime may be added to precipitation and filtration 410 to precipitate cobalt as cobalt gypsum (“CoGyp”). Precipitation and filtration 410 thus produces precipitated cobalt 405. Precipitated cobalt 405 may be passed to leach 404.
A portion of extracted cobalt bearing solution 409 is then subjected to organic polishing 414. Organic polishing 414 comprises a filtration of extracted cobalt bearing solution 409 in a carbon column. A carbon column may comprise any suitable carbon media, such as, for example, activated charcoal, powdered activated carbon or granulated activated carbon. Carbon media may adsorb various impurities from extracted cobalt bearing solution 409. For example, carbon media may adsorb organic compounds from extracted cobalt bearing solution 409. Carbon media is suited for adsorption due to its high surface area, among other properties. In that regard, other media may be used in organic polishing 414 that are suitable for adsorbing or absorbing organic compounds. Carbon media may periodically be regenerated or replaced to maintain appropriate adsorbing performance. Organic polishing 414 produces polished cobalt bearing solution 411.
Polished cobalt bearing solution 411 may be forwarded to copper ion exchange (Cu IX) 416. Copper may be present at relatively low concentrations in polished cobalt bearing solution 411. Copper present in polished cobalt bearing solution 411 may exist as copper I and/or copper II. Cu IX 416 may be used to remove copper. Copper removed by Cu IX 416 may be in either metal or ionic form. Ion exchange may be accomplished in any suitable manner. For example, polished cobalt bearing solution 411 may be contacted with a surface or membrane containing ions. A surface or membrane in an ion exchange step may be comprised of a synthetic resin, a polymer, or any other suitable material. In various embodiments, for example, LEWATIT MONOPLUS TP207 resin, made by Lanxess of Birmingham, N.J. USA, is used. In further embodiments, PUROLITE S950 resin, made by Purolite, Inc. of 150 Monument Road, Bala Cynwyd, Pa. 19004, USA is used. Copper from cobalt bearing solution 411 may be exchanged with ions present on the surface or membrane, leaving copper present on the surface or membrane. The membrane or surface may be washed periodically to remove the adhered copper and increase efficacy of the ion exchange step. During such periodic washing, acid or other media may be contacted with the membrane or surface to remove the deposited copper ions. The acid or other media may be recycled into a primary leaching process to recover the copper ions washed off the membrane or surface. Cu IX 416 produces exchanged cobalt bearing solution 413. Copper removal could also be done with a suitable organic extractant using liquid extraction, although in various embodiments, solvent extraction is not used for removing copper.
Exchanged cobalt bearing solution 413 is subjected to organic polishing 418. Organic polishing 418 may be conducted in the same or similar manner as organic polishing 414. For example, exchanged cobalt bearing solution 413 may be contacted with a carbon column to further remove impurities, such as organic compounds. Organic polishing 418 produces polished cobalt bearing solution 415.
Polished cobalt bearing solution 415 may be subjected to nickel ion exchange (Ni IX) 420. NiIX 420 may be accomplished in any suitable manner. For example, polished cobalt bearing solution 415 may be contacted with a surface or membrane containing ions. A surface or membrane in an ion exchange step may be comprised of a synthetic resin, a polymer, or any other suitable material. In various embodiments, for example, DOWEX M4195 resin is used. DOWEX M4195 is made by the Dow Chemical Company, Dow Water Solutions, Customer Information Center, P.O. Box 1206, Midland, Mich. 48642-1206. In further embodiments, for example, DOWEX XUS43605 resin is used. DOWEX XUS43605 is made by the Dow Chemical Company, Dow Water Solutions, Customer Information Center, P.O. Box 1206, Midland, Mich. 48642-1206. Nickel from polished cobalt bearing solution 415 may be exchanged with ions present on the surface or membrane, leaving nickel present on the surface or membrane. In various embodiments, a portion of the cobalt in polished cobalt bearing solution 415 may also become bound to the surface or membrane. NiIX 420 produces purified cobalt bearing solution 417.
The membrane or surface may be washed periodically to remove the adhered cobalt and increase efficacy of the ion exchange step. For example, Co Elution 424 comprises a regeneration or purging of the membrane or surface of NiIX 420 to remove cobalt that may have adhered to the membrane or surface. In that regard, Co Elution 424 may comprise contacting an elution medium, such as an acid medium, with the membrane or surface. The elution medium may be conducted to leach 404 to improve cobalt recovery.
The membrane or surface may be washed periodically to remove the adhered nickel and increase efficacy of the ion exchange step. Ni Elution 424 comprises a regeneration or purging of the membrane or surface of NiIX 420 to remove nickel that may have adhered to the membrane or surface. In that regard, Ni Elution 424 may comprise contacting an elution medium, such as an acid medium, with the membrane or surface. The elution medium may be conducted to tails via neutralization 428. Neutralization 428 may include the addition of lime or other agent to adjust the pH of the tails.
Purified cobalt bearing solution 417 may be forwarded to electrowinning cell 422. Electrowinning cell 422 yields a cobalt metal cathode product. As those skilled in the art are aware, a variety of methods and apparatus are available for the electrowinning of cobalt and other metal values, any of which may be suitable for use in accordance with the present invention, provided the requisite process parameters for the chosen method or apparatus are satisfied.
In various embodiments, electrowinning may be performed in electrowinning cell 422 such that the anodes and cathodes are not separated into compartments. In such embodiments, the anodes and cathodes are placed in the same media without a barrier and electrical current is applied. For example, electrowinning cell 422 may comprise a cathode compartment and an anode compartment. Metal values, such as cobalt, may evolve at the cathode. Manganese, among others species, may evolve at the anode. It has been found that electrowinning in undivided compartment is advantageous where the electrowinning is done in close proximity to a primary metal recovery operation.
With reference to
Metal recovery process 500 comprises subjecting cobalt bearing material (“Co MAT”) 502 to leach 504, filtration 507, and solution extraction 513. At least a portion of the tails of filtration 507 may proceed to tails 522. Metal recovery process 500 comprises divided compartment electrowinning 518.
Cobalt bearing material 502 may be an ore (cobaltite, heterogenite (CoOOH), erythrite, glaucodot, skutterudite, other cobalt containing ores, and mixtures of cobalt containing ores with ores bearing other metal values), a concentrate, a process residue, an impure metal salt, a preprocessed cobalt bearing material, combinations thereof, or any other material from which cobalt values are present. Cobalt, whether in metal or ionic form, may be recovered from cobalt bearing material 502 in accordance with various embodiments of the present invention. In various embodiments, cobalt bearing material 502 contains other metal values, such as precious metals (e.g., gold, silver and platinum) and copper. Various aspects and embodiments of the present invention, however, prove especially advantageous in connection with the recovery of cobalt from a preprocessed cobalt bearing material. A preprocessed cobalt bearing material may comprise a material that has been subjected to a prior metallurgical process. For example, a metallurgical process may result in the formation of cobalt hydroxide (Co(OH)2). Cobalt hydroxide may be formed by combining a cobalt bearing material with magnesium oxide (MgO) and/or lime. It should be appreciated that a preprocessed cobalt bearing material may contain various other constituents as impurities or coprecipitates, such as copper, zinc, and/or nickel. In various embodiments, cobalt bearing material 502 comprises cobalt hydroxide. In various embodiments, cobalt bearing material 502 comprises cobalt hydroxide produced by addition of magnesium oxide to a material containing cobalt ions. In various embodiments, cobalt bearing material 502 comprises cobalt hydroxide produced by addition of lime to a material containing cobalt ions. In various embodiments, cobalt bearing material 502 comprises cobalt hydroxide produced by addition of lime and/or magnesium oxide. Cobalt produced using magnesium oxide is generally considered of greater quality than cobalt produced using lime, though various factors, including reagent costs, may affect the selection of an appropriate cobalt bearing material.
In accordance with various embodiments, leach 504 may comprise any type of leaching process that is capable of yielding received cobalt 503 to a condition to be subjected to later metal recovery steps. In various embodiments, leach 504 yields cobalt bearing leachate 506, described in detail herein below.
Leachate 506 may be directed to filtration 507. Filtration 507 may comprise any suitable filtration process. For example, vacuum filters such as a belt filter or disc filter may be used. In addition, pressure filters such as a plate and frame filter may be used.
Filtration 507 may separate the leachate 506 into a solid phase and a liquid phase. The solid phase is sent to tails 522. Tails 522 may be treated (e.g., neutralized) and processed in any suitable manner. The liquid phase of leachate 506 comprises liquid leachate 508. Liquid leachate 508 is forwarded to solution extraction 513.
In various embodiments, solution extraction 513 comprises a solution extraction process. Solution extraction 513 is configured to selectively extract impurities, as described in further detail herein. In various embodiments, solution extraction 513 comprises a liquid-liquid extraction. During solution extraction 513, cobalt (e.g., ionic cobalt) from the liquids phase may be loaded selectively into an organic phase in an extraction stage, wherein the organic phase comprises an extracting agent, which may also be referred to as an extractant. For example, Di-(2-ethylhexyl)phosphoric acid (D2EHPA) may be used as an extracting agent. Cobalt is retained in the aqueous phase and Zn, Mn, and Ca are loaded in the organic phase.
The organic phase from solution extraction 513 may be then subjected to one or more wash stages and/or scrub stages in which the loaded organic phase is contacted with an aqueous phase in order to remove entrained/extracted aqueous solution from the organic phase. The washed organic phase may then be subject to a solvent stripping stage, wherein the cobalt is transferred to an aqueous phase. For example, more acidic conditions may shift the equilibrium conditions to cause the cobalt to migrate to the aqueous phase. Loaded aqueous streams 512 and 514 thus comprise cobalt containing liquid from solution extraction 513.
Loaded aqueous stream 512 may be forwarded to precipitation and filtration 511, to precipitate any cobalt that was stripped from the organic phase in the wash/scrub stage.
Precipitation and filtration 511 may comprise a filtration process wherein a reagent is added to selectively precipitate cobalt. Precipitation and filtration 511 may comprise a precipitation that includes the use of a variety of precipitants, including, for example, calcium compounds such as gypsum (calcium sulfate), lime (calcium hydroxide and/or calcium oxide), calcium carbonate and milk of lime (certain preparations of calcium hydroxide). In various embodiments, any suitable source of gypsum or lime may be used in precipitation and filtration 511. For example, lime and gypsum may be added to precipitation and filtration 511 to precipitate cobalt as cobalt gypsum (“CoGyp”). Precipitation and filtration 511 thus produces precipitated cobalt 510. Precipitated cobalt 510 may be passed to leach 504.
Loaded aqueous stream 514 may be passed to further processing 516. Further processing 516 may comprise any metal recovery process, such as ion exchange, electrowinning, solution extraction, carbon column filtering, and combinations thereof. Processed cobalt bearing material 517 is forwarded to compartmentalized electrode electrowinning 518. Processed cobalt bearing material 517 may yield cobalt metal. For example, processed cobalt bearing material 517 may comprise electrowinning cobalt using a compartmentalized (e.g., bagged) electrode process.
Bagged electrodes, such as bagged anodes, are advantageously employed to enhance cobalt recovery. Typical bagged electrode processes tend to benefit from enhanced monitoring and care. Thus, bagged electrode processes may benefit from being conducted not in close proximity to a primary metal recovery process so that appropriate skilled personnel may properly maintain process conditions.
Upstream bleed 509 comprises a portion of filtrate 508. Upstream bleed 509 may be used to bleed a portion of filtrate 508 to precipitation and filtration 511, thus bypassing solution extraction 513. Upstream bleed 509 acts as a bleed of impurities such as MgSO4 and Na2SO4 from the circuit and allows for the reduction in process volumes in downstream processing, whose benefits are described elsewhere herein.
With reference to
Cobalt leach 604 is conducted in acid media under the addition of sulfur dioxide gas, though any suitable reducing agent may be used in lieu of or with sulfur dioxide gas. Cobalt leach 604 may be performed under pressure and at temperatures above 25° C., though in various embodiments, cobalt leach 604 is conducted at atmospheric temperature and ambient temperature. Cobalt leach 604 yields a leachate that is forwarded to filtration 608. Sulfur dioxide addition acts to reduce cobalt Ill into cobalt II, which is readily dissolved into solution. Acid may also be added to cobalt leach 604 from time to time.
Filtration 608 separates the slurry output of cobalt leach 604 into a solid phase and a liquid phase. Filtration 608 comprises filtering the slurry output of cobalt leach 604 in the presence of gypsum. It has been found that gypsum acts as a suitable filtering aid, in addition to providing various other benefits.
Solid phase output 630 of filtration 608 is sent to neutralization/tails 628. Neutralization/tails 628 may comprise an addition of lime or other agent to chemically adjust the pH of the tails prior to further processing of the tails.
A first portion of the liquid phase output of filtration 608 is bled as bleed 612 to precipitation and filtration 610. A second portion of the liquid phase output of filtration 608 is forwarded to Zn/Mn/Ca SX 606. Zn/Mn/Ca SX 606 comprises a solution extraction process that removes, among other things, Zn, Mn, and Ca from the liquid portion output of filtration 608. The aqueous liquid portion of the liquid portion output of filtration 608 may be contacted with an organic solution and an extractant.
Zn/Mn/Ca SX 606 uses D2EHPA as an extractant. After cobalt is brought in the organic phase, the organic phase may be washed with water, though in various embodiments the organic phase is not washed. The organic phase may be stripped with an aqueous phase to bring cobalt to the aqueous phase. Acid for stripping the organic phase may be generated from other processes, for example, raffinate from undivided electrowinning 622 or other acidic streams from the primary metal recovery process. The aqueous phase Zn/Mn/Ca SX 606 produces may be referred to as extracted cobalt bearing solution 609.
Portion 607 of extracted cobalt bearing solution 609 is forwarded to precipitation and filtration 610. Precipitation and filtration 610 comprises a filtration process wherein a reagent is added to selectively precipitate cobalt. Precipitation and filtration 610 may comprise a precipitation that includes the use of a variety of precipitants, including, for example, calcium compounds such as gypsum (calcium sulfate), lime (calcium hydroxide and/or calcium oxide), calcium carbonate and milk of lime (certain preparations of calcium hydroxide). In various embodiments, any suitable source of gypsum or lime may be used in precipitation and filtration 610. For example, lime and gypsum may be added to precipitation and filtration 610 to precipitate cobalt as cobalt gypsum (“CoGyp”). Precipitation and filtration 610 thus produces precipitated cobalt 605. Precipitated cobalt 605 may be passed to leach 604.
A portion of extracted cobalt bearing solution 609 is then subjected to organic polishing 614. Organic polishing 614 comprises a filtration of extracted cobalt bearing solution 609 in a carbon column. A carbon column may comprise any suitable carbon media, such as, for example, activated charcoal, powdered activated carbon or granulated activated carbon. Carbon media may adsorb various impurities from extracted cobalt bearing solution 609. For example, carbon media may adsorb organic compounds from extracted cobalt bearing solution 609. Carbon media is suited for adsorption due to its high surface area, among other properties. In that regard, other media may be used in organic polishing 614 that are suitable for adsorbing or absorbing organic compounds. Carbon media may periodically be regenerated or replaced to maintain appropriate adsorbing performance. Organic polishing 614 produces polished cobalt bearing solution 611.
Polished cobalt bearing solution 611 may be forwarded to copper ion exchange (Cu IX) 616. Copper may be present at relatively low concentrations in polished cobalt bearing solution 611. Copper present in polished cobalt bearing solution 611 may exist as copper I and/or copper II. Cu IX 616 may be used to remove copper. Copper removed by Cu IX 616 may be in either metal or ionic form. Ion exchange may be accomplished in any suitable manner. For example, polished cobalt bearing solution 611 may be contacted with a surface or membrane containing ions. A surface or membrane in an ion exchange step may be comprised of a synthetic resin, a polymer, or any other suitable material. In various embodiments, for example, LEWATIT MONOPLUS TP207 resin, made by Lanxess of Birmingham, N.J. USA, is used. In further embodiments, PUJROITE S950 resin, made by Purolite, Inc. of 150 Monument Road, Bala Cynwyd, Pa. 19004, USA is used. Copper from cobalt bearing solution 611 may be exchanged with ions present on the surface or membrane, leaving copper present on the surface or membrane. The membrane or surface may be washed periodically to remove the adhered copper and increase efficacy of the ion exchange step. During such periodic washing, acid or other media may be contacted with the membrane or surface to remove the deposited copper ions. The acid or other media may be recycled into a primary leaching process to recover the copper ions washed off the membrane or surface. Cu IX 616 produces exchanged cobalt bearing solution 613.
Exchanged cobalt bearing solution 613 is subjected to organic polishing 618. Organic polishing 618 may be conducted in the same or similar manner as organic polishing 614. For example, exchanged cobalt bearing solution 613 may be contacted with a carbon column to further remove impurities, such as organic compounds. Organic polishing 618 produces polished cobalt bearing solution 615.
Polished cobalt bearing solution 615 may be subjected to nickel ion exchange (Ni IX) 620. NiIX 620 may be accomplished in any suitable manner. For example, polished cobalt bearing solution 615 may be contacted with a surface or membrane containing ions. A surface or membrane in an ion exchange step may be comprised of a synthetic resin, a polymer, or any other suitable material. In various embodiments, for example, DOWEX M4195 resin is used. DOWEX M4195 is made by the Dow Chemical Company, Dow Water Solutions, Customer Information Center, P.O. Box 1206, Midland, Mich. 48642-1206. In further embodiments, for example, DOWEX XUS43605 resin is used. DOWEX XUS43605 is made by the Dow Chemical Company, Dow Water Solutions, Customer Information Center, P.O. Box 1206, Midland, Mich. 48642-1206. Nickel from polished cobalt bearing solution 615 may be exchanged with ions present on the surface or membrane, leaving nickel present on the surface or membrane. In various embodiments, a portion of the cobalt in polished cobalt bearing solution 615 may also become bound to the surface or membrane. NiIX 620 produces purified cobalt bearing solution 617.
The membrane or surface may be washed periodically to remove the adhered cobalt and increase efficacy of the ion exchange step. For example, Co Elution 624 comprises a regeneration or purging of the membrane or surface of NiIX 620 to remove cobalt that may have adhered to the membrane or surface. In that regard, Co Elution 624 may comprise contacting an elution medium, such as an acid medium, with the membrane or surface. The elution medium may be conducted to leach 604 to improve cobalt recovery.
The membrane or surface may be washed periodically to remove the adhered nickel and increase efficacy of the ion exchange step. Ni Elution 626 comprises a regeneration or purging of the membrane or surface of NiIX 620 to remove nickel that may have adhered to the membrane or surface. In that regard, Ni Elution 626 may comprise contacting an elution medium, such as an acid medium, with the membrane or surface. The elution medium may be conducted to tails via neutralization/tails 628.
Purified cobalt bearing solution 617 may be forwarded to electrowinning cell 622. Electrowinning cell 622 yields a cobalt metal cathode product. As those skilled in the art are aware, a variety of methods and apparatus are available for the electrowinning of cobalt and other metal values, any of which may be suitable for use in accordance with the present invention, provided the requisite process parameters for the chosen method or apparatus are satisfied.
In various embodiments, electrowinning may be performed in electrowinning cell 622 such that the anodes and cathodes are housed in separate compartments. For example, electrowinning cell 622 may comprises a cathode compartment and an anode compartment.
Compartments may be formed by the placement of a bag or other barrier, whether permeable or semi-permeable, around or partially around one or more of the anodes and cathodes. For example, a bag may be placed around all or a portion of an anode. The electrolyte is thus divided into anolyte and catholyte. A bag that at least partially encloses the anode may be semi-permeable to anolyte. In that regard, anolyte may be withdrawn from within the semi-permeable anode bag by the slight negative pressure created from an anolyte gas scrubber fan, thus avoiding the generation of acid mist within the electrowinning tankhouse. Bagged anodes may tend to prevent contact between the anode and cathode. Various anodes and anode coatings may be susceptible to short circuiting, thus it is beneficial to create barriers to prevent such short circuiting.
Cobalt metal may evolve at the cathode. Manganese, among others species, may evolve at the anode. Manganese and other species from the anode may be forwarded to a leach or other metal recovery processing operation. Lean electrolyte from the anode compartment may be forwarded to leach 604.
Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any element or combination of elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of any or all the claims or the invention. Many changes and modifications within the scope of the instant invention may be made without departing from the spirit thereof, and the invention includes all such modifications. Corresponding structures, materials, acts, and equivalents of all elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claim elements as specifically claimed. The scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given above.
