This document relates generally to the extraction of copper, and/or gold and other elements of value from materials including, particularly E-waste materials, copper bearing end of life manufactured products, or ores by a method of specific control of the leaching circuit to allow adequate consumption of the reagent causing leaching and the recovery of metal from the feed material.
For purposes of this document “waste materials” broadly refers to any waste materials potentially including valuable elements and, more particularly, metals that may be reclaimed and recycled. Thus, waste materials include E-waste materials, auto shred materials containing base and precious metals, communications equipment such as plated wave guides, mixed metal conductors or wires, and the like. For purposes of this document, E-waste materials means any such material comprised of at least copper and one precious metal.
This document describes a new and improved method for the enhanced recovery of copper, gold and other valuable metals and materials from waste materials in a more efficient and cost-effective manner by teaching novel techniques to controlling the oxidizer reagent in the leaching circuit. Note that oxidizer and reagent are used synonymously herein.
In accordance with the purposes and benefits set forth herein, a new and improved method is provided for recovering metals from waste materials. That method broadly comprises, consists essentially of or consists of the steps of: (a) contacting the feed material with a lixiviant adapted to leach the target metal from a feed material feed stream in a leaching circuit having a plurality of leaching vessels V1, V2, Vn in series, (b) establishing a countercurrent flow in the leaching circuit by delivering the feed material feed stream to the leaching vessel V1 and moving the feed material feed stream through the leaching circuit in a first direction toward leaching vessel Vn and delivering the lixiviant to the leaching vessel Vn and moving the lixiviant through the leaching circuit in a second direction toward leaching vessel V1; (c) determining, by setting which may be via a controller, a reagent consumption rate for each of the leaching vessels V1, V2, Vn so as to validate performance, minimize left over reagent discharged from leaching vessel V1 and maximize target metal recovery from leaching vessel Vn and (d) recovering the target metal from the feed material into the lixiviant.
In one or more of the many possible embodiments of the method, the method further includes calculating, by the controller, the reagent consumption rate for each vessel V1, V2, Vn based upon a formula (Cn,in−Cn,out)/Cn,in*100 where Cn,in is a concentration of the reagent entering the vessel and Cn,out is the concentration of the reagent leaving the vessel where n designates the nth tank.
In one or more of the many possible embodiments of the method, the method includes one or both of (a) using an ammonia-based lixiviant and (b) using copper (II) (Cu(II)) as an oxidizer and component of the lixiviant. Those skilled in the art may recognize any number of oxidizers may be used such as hydrogen peroxide or metal species which has multiple valances which allow for stable ionic compounds in the lixiviant.
In at least some embodiments, the method may further include determining, by the controller via manipulating flow rates, a residence time for the feed material in each vessel V1, V2, Vn based upon (or required by) an average particle size of the feed material feed stream to reach certain recoveries.
In some embodiments, the method includes one or more of the following: (a) conducting the leaching under anaerobic conditions, (b) using electronic waste as the feed material (including ores) and selecting copper metal as the target metal, (c) using electrowinning in the recovering of the copper metal from the lixiviant, and (d) generating Cu(II) ions during electrowinning and using the generated Cu(II) ions as an oxidant for leaching the copper metal in the leaching circuit, and/or (e) using air or oxygen for regenerating Cu(II) ions.
In accordance with an additional aspect, an apparatus for recovering a target metal from a feed material, comprises, consists essentially of or consists of; (a) a leaching circuit having a plurality of leaching vessels V1, V2, Vn in series, and (b) a control module including (i) a metering system adapted for delivering the feed material feed stream to the leaching vessel V1 and moving the feed material feed stream through the leaching circuit in a first direction toward leaching vessel V1 and delivering a liquid phase, including an ammonia-based lixiviant and a Cu(II) reagent, to the leaching vessel V1 and moving the liquid phase through the leaching circuit in a second direction toward leaching vessel V1, (ii) at least one Cu(II) concentration monitor or sensor adapted for monitoring the concentration of Cu(II) in at least one of the leaching vessels V1, V2, Vn in the leaching circuit and collecting data respecting the concentration of Cu(II) in each of the leaching vessels V1, V2, Vn in the leaching circuit, and (iii) a controller adapted to receive the data from a singular or a plurality of Cu(II) concentration monitors and maintain the concentration of the copper II (Cu(II)) in the ammonia-based lixiviant in the leaching vessels V1, V2, Vn by changing the flow rate of the liquid phase, and/or the flow rate of the feed material feed stream to achieve metal removal from the feed material feed stream of between 1 and 50% in each vessel.
In at least some embodiments, the controller is further adapted to calculate the Cu(II) reagent consumption in each vessel V1, V2, Vn in accordance with a formula (Cn,in−Cn,out)/Cn,in*100 where Cn,in is a concentration of the Cu(II) reagent entering the vessel and Cn,out is the concentration of the Cu(II) reagent leaving the vessel.
In at least some of the embodiments of the apparatus, the apparatus further includes a shredding device, adapted for shredding the feed material to an average particle size of less than 10 mm, upstream from the leaching vessel V1. In at least some embodiments, the apparatus further includes an electrowinning device, adapted to recover copper metal from the ammonia-based lixiviant and generate Cu(II) ions for use as an oxidant for leaching the copper metal in the leaching circuit, downstream from leaching vessel V1. In one or more of the embodiments, the leaching vessels V1, V2, and Vn are lamella clarifiers with agitation.
In the following description, there are shown and described several preferred embodiments of the method. As it should be realized, the method is capable of other, different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the method as set forth and described in the following claims. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not as restrictive.
The accompanying drawing figures incorporated herein and forming a part of the patent specification, illustrate several aspects of the method and one possible apparatus for performing the method and together with the description serve to explain certain principles thereof.
Reference will now be made in detail to the present preferred embodiments of the method, examples of which are illustrated in the accompanying drawing figures.
Chemical reactions—In ammonia leaching, ammonium salts (NH4Cl or (NH4)2SO4), and possible combinations of copper compounds such as CuSO4, CuO, Cu2O) combined with ammonia (NH3 in forms of NH4OH) are dissolved in water and used as the lixiviant. The dominant species in a Metal-NH3—H2O system are NH3, NH4+, H+, OH− and corresponding anions. The corresponding metal species are complexed with the existing NH3 and OH− ions and corresponding anions. In an embodiment, the leaching of Cu by ammonia/ammonium solution can be divided into two steps: 1) the oxidation of Cu0 to Cu2+ by oxidant such as O2, O2 via air, H2O2, or Fe3+, and the formation of CuO; 2) the dissolution of CuO in ammonia/ammonium solution and the generation of soluble copper-ammonia complex.
In the preferred embodiment, leaching of copper, and by extension other base metals. The major reactions are described as follows:
Eh-pH diagrams—The Eh-pH diagrams (Pourbaix diagrams) of Cu—NH3—H2O system are referenced from the existing literature in order to better illustrate the copper speciation in ammonia/ammonium matrix as shown in
Chemical reactions—After the leaching stage, where copper is leached out as divalent ions in ammonia/ammonium solution, contaminant ions in the solution may be extracted via solvent extraction. The purified electrolyte is conveyed to the electrowinning stage. Such a copper recovery process is schematically illustrated in
Reaction mechanism—In an embodiment of the leaching process, electronic wastes are leached in the ammonium solution containing Cu(NH3)42+ ions (Cu2+), and the metallic copper (Cu0) in the wastes reacts with the Cu2+ and is dissolved as Cu(NH3)2+ ions (Cu+) through the oxidation process described in equations 5 and 6. In the following solvent extraction process, the other base metals or undesired impurities such as iron, aluminum, nickel, cobalt and zinc (tri and divalent ions), can be separated using a selective extractant in ways known in the art. In this embodiment, the electrowinning stage, high purity Cu0 is obtained on the cathode from the Cu+/Cu2+ containing solution. Simultaneously, Cu+ is oxidized to Cu2+ on the anode and the produced Cu2+ is recycled back in the leaching stage as the oxidizing reagent.
Chemical reactions—In thiosulfate leaching for gold, the formation of gold thiosulfate complex proceeds via the catalytic oxidation reaction with Cu(NH3)42+ acting as the primary oxidant. This process can be divided into two steps: 1) the oxidation of Au0 to Au+ in forms of Au(NH3)2+ under the oxidative environment provided by the presence of Cu(NH3)42+, which is also a product from the previous copper ammonia leaching process; 2) the Au(NH3)2+ complex further reacts with S2O32− ion in the solution and forms stable Au(S2O3)23− specie. The reactions are as follows:
A schematic of the mechanism of gold thiosulfate leaching is shown in
Reference is now made to
Next, the fine shredded waste materials 22 are transferred by a skid steer 24 or other means to a metered feeder 26 of a type known in the art to be useful for the metered feeding of such materials. The metered E-waste material may then be transferred by a conveyor 28 or other useful means to the first reactor vessel or unit 30 of a first leaching circuit, generally designated as 32.
In the illustrated embodiment, the first leaching circuit 32 includes a total of five reactor vessels designated 30, 34, 36, 38 and 40 that are connected in series and form a counter current leaching arrangement. The waste material feed stream delivered to the first unit 30 is contacted with a first lixiviant in the units 30, 34, 36, 38 and 40 of the first leaching circuit 32. That first lixiviant is particularly adapted to leach copper metal and other base metals from the waste material feed stream while leaving any noble metals behind in the treated waste material feed stream that is ultimately discharged from the first leaching circuit 32.
In one particularly useful embodiment, the E-waste material feed stream is subjected to ammonia leaching in the first leaching circuit 32 in order to leach the copper and the other base metals from the waste material feed stream. As noted above, ammonia leaching uses ammonium salts (NH4Cl or (NH4)2SO4) combined with ammonia (NH3 in form of NH4OH) dissolved in deionized water.
As should be appreciated, the waste material feed stream travels in a first direction through the first leaching circuit 32 from the first reactor vessel 30, to the second reactor vessel 34, then to the third reactor vessel 36, then to the fourth reactor vessel 38 and then finally to the fifth reactor vessel 40. The first ammonia-based lixiviant travels in a second opposite direction in a countercurrent flow to the waste material feed stream from the fifth reactor vessel 40, to the fourth reactor vessel 38, then to the third reactor vessel 36, then to the second reactor vessel 34 and then finally to the first reactor vessel 30. The various pumps 42 move the first ammonia-based lixiviant through the reactor vessels 40, 38, 36, 34 and 30 of the first leaching circuit 32. The first ammonia-based lixiviant is first transferred from the first reactor vessel 30 by the pump 44 to a filter 46 which captures any remaining particles of the waste material feed stream. The filtered first lixiviant is then transferred to a solvent extraction circuit 48 of a type known in the art, that is adapted to remove base metals other than copper from the first lixiviant. Those other base metals include, but are not necessarily limited to, iron, nickel, chromium, silver, zinc, cobalt and the like.
The treated first ammonia-based lixiviant with the copper ions retained and the other base metal ions extracted is then transferred to an electrowinning press 50 of the type disclosed in, for example, International Application Publication number WO2021/159086 (the full disclosure of which is incorporated herein by reference) filed concurrently herewith and entitled Electrowinning Cells for The Segregation of the Cathodic and Anodic Compartments. There, copper metal is recovered from the first ammonia-based lixiviant on the cathodes of the electrowinning cells making up the electrowinning press.
During the electrowinning process, Cu2+ ions are generated in the first lixiviant. These Cu2+ ions are used as an oxidant in the leaching of the copper and the other base metals from the waste material feed stream in the first leaching circuit. The first lixiviant, minus the now recovered copper metal and plus the Cu2+ ions generated during electrowinning is returned to the reactor vessel 40 of the first leaching circuit 32 by the pump 52. Preferably, the Cu2+ ion concentration in the first lixiviant of the first leaching circuit 32 is maintained between about 0.0001 M and about 1.6 M to enhance the leaching efficiency of the first circuit. The Cu2+ ion concentration may be adjusted by controlling the rate of the metered feeding of waste material to the first circuit, the lixiviant flow rate, between stage solid transfer rate or the current in the electrowinning cell 32.
The treated waste material feed stream is delivered from the last reactor vessel 40 of the first leaching circuit 32 to a belt filter wash (or other solid/liquid separators and conveyances of a type known in the art) 54 where the majority of the first lixiviant remaining on the treated E-waste stream is recovered and returned by the pump 56 to the unit 40 of the first leaching circuit 32.
The treated E-waste feed stream with some remaining first lixiviant, including Cu2+ ions, is then transferred by the conveyor 58 to the second leaching circuit generally designated by reference numeral 60 where it is contacted with a second lixiviant. The Cu2+ ion concentration in the second lixiviant is preferably maintained between about 0.0001 M and about 0.1 M in the second lixiviant in order to provide sufficient oxidization to efficiently leach the at least one noble metal from the treated waste material stream. If desired, additional oxidizer for leaching may be provided by sparging oxygen through the second lixiviant.
In the illustrated embodiment, the second leaching circuit includes five reactor vessels or units 62, 64, 66, 68 and 70 connected in series. The treated E-waste material feed stream delivered to the second leaching circuit 60 is contacted with a second lixiviant in the units 62, 64, 66, 68 and 70. The second lixiviant is particularly adapted to recover at least one noble metal from the treated E-waste feed stream. For purposes of this document, “noble metals” include silver, platinum, palladium and gold.
In one particularly useful embodiment of the method, the method uses thiosulfate leaching to leach the noble metals from the treated waste material feed stream in the second leaching circuit 60. As noted above, the Cu2+ ions in any remaining first lixiviant on the treated waste material feed stream transferred to the second leaching circuit 60 acts as a primary oxidizer to catalyze the leaching of the at least one noble metal, and, more particularly, the gold from the treated E-waste feed stream.
As should be appreciated, the treated waste material feed stream travels in a third direction through the second leaching circuit 60 from the first reactor vessel 62, to the second reactor vessel 64, then to the third reactor vessel 66, then to the fourth reactor vessel 68 and then finally to the fifth reactor vessel 70. The second lixiviant travels in a fourth direction in a countercurrent flow to the treated waste material feed stream from the fifth reactor vessel 70, to the fourth reactor vessel 68, then to the third reactor vessel 66, then to the second reactor vessel 64 and then finally to the first reactor vessel 62. The various pumps 72 move the second lixiviant through the reactor vessels 70, 68, 66, 64 and 62 of the second leaching circuit 60. The second lixiviant is then transferred from the first reactor vessel 62 by a pump or other appropriate device (not shown) to a Merrill Crowe plant 74 wherein a precipitation reaction of a type known in the art is used to recover the noble metal, and, more particularly, the gold from the second lixiviant.
In an embodiment the treated waste material feed stream exiting the second leaching circuit 60 at the fifth reactor vessel 70 is delivered to a belt filter and washing station 76 and a reverse osmosis unit 78 where all the reagents including the second lixiviant are washed from the treated waste material feed stream, recovered and then returned to the fifth reactor vessel 70 by the pumps 80 and 82. The now washed and treated waste material feed stream 84 may then be dried in an oven 86 with the tails deposed of in a suitable and ecologically sound manner or readied for further processing.
Any or all of the reactor vessels 30, 34, 36, 38, 40, 62, 64, 66, 68 and 70 may take the form of the agitated lamella clarifier 10′ illustrated in
The clarifier section 22′ overlies and is axially aligned with the mixing section 20′ along the center axis 18′ within the housing 12′. As illustrated, the clarifier section 22′ includes a plurality of plates 261′-26n′ that are nested together and define a plurality of intervening flow passageways 281′-28n′. In the illustrated embodiment, the plates 261′-26n′ are frustoconical in shape. Such a shape may be approximated by interconnecting a series of flat plates if desired. The lowermost ends 301′-30n′ of the respecting intervening flow passageways 281′-28n′ open into an axial passageway 32′ that extends through the clarifier section 22′ along and concentrically around the center axis 18′.
The single stage clarifier mixing assembly 10′ also includes an inlet 34′ adapted for delivering an inlet stream to the mixing section 20′ and, more particularly, the mixing chamber 24′. For purposes of this document, the terminology “inlet stream” refers to a liquid or slurry to be processed through the mixing assembly.
The single stage clarifier mixing assembly 10′ also includes an agitator, generally designated by reference numeral 36′, that is adapted to mixing the inlet stream in the mixing chamber 24′. The single stage clarifier mixing assembly 10′ also includes an inlet stream feed conduit 38′ that extends along the center axis 18′ through the axial passageway 32′ to the inlet 34′. As will be described in greater detail below, the inlet stream is fed through the feed conduit 38′ to the inlet 34′ where that inlet stream is delivered to the mixing chamber 24′ of the mixing section 20′.
The agitator 36′ of the illustrated embodiment includes a drive motor 40′ connected by a drive shaft 42′ to an impeller 44′ which, in the illustrated embodiment, is provided at the distal end of the drive shaft. As illustrated, the drive shaft 42′ extends along the center axis 18′ through the feed conduit 38′ and the inlet 34′. Thus, it should be appreciated that the feed conduit 38′ and inlet 34′ are concentrically disposed around the drive shaft 42′; the axial passageway 32′ is concentrically disposed about the feed conduit 38 and the inlet 34′; and the lowermost ends 301′-30n′ of the respective intervening flow passageways 281′-28n′ and the lowermost ends of the frustoconical plates 261′-26n′ are concentrically disposed about the axial passageway 32′.
As further illustrated in
The clarifier section 22′ also includes a clarified liquid flow gutter 50′ (i.e. overflow weir) that extends concentrically around the clarifier liquid chamber 46′ and functions to feed clarified leachate to the first outlet 52′ that extends from the bottom wall of the clarified liquid flow gutter 50′ through the circular sidewall 14′ of the housing 12′. A first outlet stream is discharged from the first outlet. Depending upon the particular application, the “first outlet stream” may comprise a clarified liquid, a clarified leachate, or clarified barren solution.
As still further shown in
In addition, the mixing section 20′ includes a second outlet 62′ provided in circular sidewall 14′ outboard of the clarifier section 22′ at a vertical position substantially corresponding to the clarified liquid flow gutter 50′: that is, substantially corresponding to the top of the frustoconical plates 261′-28n′. A second outlet stream is discharged from the second outlet 62′. Depending upon the particular application, the second outlet stream may comprise a concentrated-solids slurry or a slurry of the same concentration as the mixing chamber 24′.
In operation, an inlet stream, such as a slurry, is delivered to the single stage clarifier mixing assembly 10′ by means of the feed conduit 38′ (note action arrow A). The inlet stream passing through the feed conduit 38′ is discharged from the inlet 34′ into the mixing chamber 24′ of the mixing section 20′ (note action arrows B). The agitator 36′ turns with the necessary rotational speed to mix the inlet stream (e.g. slurry) in the mixing chamber 24′ and maintain the slurry in suspension. The strongest mixing action is provided at the very bottom of the mixing chamber 24′ adjacent the bottom wall 16′ below the bottoms 58′ of the vanes 56′. As the liquid flow is not all exiting via 62′, the inlet stream rises in the housing 12′, the inlet stream passes through the axial passageway 32 through the lowermost ends 301′-30n′ and fills the respective intervening flow passageways 281′-28n′ defined between the frustoconical plates 261′-26n′ (note action arrows C).
It is in these intervening flow passageways 281′-28n′ that lamella separation occurs and solids from the inlet stream (e.g. slurry) flow downward (note action arrows D) in the intervening flow passageways 281′-28n′ on the upper faces of the frustoconical plates 261′-26n′ under the force of gravity while clarified liquid from the inlet stream flows upward (note action arrows E) and is pushed into the clarified liquid chamber 46′ through the uppermost ends 481′-48n′ of the intervening flow passageways. The resulting clarified liquid (a.k.a. first outlet stream) flows outward (note action arrows F) in the clarified liquid chamber 46′ into the clarified liquid flow gutter 50′ and is subsequently discharged through the first outlet 52′. In contrast, a second outlet stream with concentrated solids is simultaneously forced outward at the top of the mixing chamber 24′ through the second outlet 62′.
Reference is now made to
In addition, the second outlet stream or slurry from the second outlet 162 of the first lamella clarifier 100 is delivered to the mixing chamber 224 of the second single stage clarifier mixing assembly 200 through the feed conduit 238 and the inlet 234 and the second outlet stream or slurry from the second outlet 262 of the second lamella clarifier 200 is delivered to the mixing chamber 324 of the third lamella clarifier 300 through the feed conduit 338 and the inlet 334. Of course, the inlet stream, fresh leachate or unprocessed slurry is also being fed from a source 400 into the mixing chamber 124 of the first lamella clarifier 100 through the feed conduit 38 and inlet 134 while processed slurry being discharged from the outlet 362 of the third lamella clarifier 300 is being discharged from the system.
As should be appreciated, the plurality of frustoconical plates 261′-26n′ in the various lamella clarifiers 10, 100, 200, 300 are arranged so as to allow for an increase of inter-lamella area as the radius of the plates increases. The effect of this increase in inter-lamella area is that the mean stream velocity of the inlet stream or slurry in the lamella clarifier decreases with increasing radius. As the mean stream velocity of the inlet stream or slurry decreases, the settling efficiency of the solids improves as a function of radius.
While the previous description refers to separations of solid from a slurry it should be appreciated that the lamella clarifiers 10′, 100, 200, 300 disclosed above may not only be used in liquid-solid separations, but also for purposes of liquid-liquid separation as well as part of solid-liquid reactors and liquid-liquid reactors.
The plurality of frustoconical plates 261′-26n′ and the plurality of intervening flow passageways 281′-28n′ defined between those plates may be oriented at an angle of between 15 and about 60 with respect to the center line axis 18′ which extends in a vertical direction. In one particularly useful embodiment, the angle of the plurality of frustoconical plates 261′-26n′ and plurality of intervening flow passageways 281′-28n′ is approximately 35 degrees.
The above description may be said to relate to an apparatus 10 for recovering a target metal from a feed material. The apparatus may be described as including; (a) a leaching circuit, such as shown at 32, having a plurality of leaching vessels, 30, 34, 36, 38 and 40 in series (and also referenced by the designation V1, V2, . . . Vn), and (b) a control module 43 including (i) a metering system 26, 28 (including pumps 42) adapted for delivering the feed material feed stream to the leaching vessel V1 and moving the feed material feed stream through the leaching circuit in a first direction toward leaching vessel Vn and delivering a liquid phase, including an ammonia-based lixiviant and a Cu(II) reagent, to the leaching vessel Vn and moving the liquid phase through the leaching circuit in a second direction toward leaching vessel V1, (ii) a plurality of Cu(II) concentration monitors or sensors 45, of a type known in the art, adapted for monitoring or sensing the concentration of Cu(II) in each of the leaching vessels V1, V2, Vn in the leaching circuit and collecting data respecting the concentration of Cu(II) in each of the leaching vessels V1, V2, Vn in the leaching circuit, and (iii) a controller 47 adapted to receive the data from the plurality of Cu(II) concentration monitors/sensors and maintain the concentration of the copper II (Cu(II)) in the ammonia-based lixiviant in the leaching vessels V1, V2, Vn by changing the flow rate of the liquid phase (by controlling operation of the pumps 42), and/or the flow rate of the feed material feed stream (by controlling operation of the metered feeder 26 and the conveyor 28) to achieve metal removal from the feed material feed stream of between 1 and 50% in each vessel.
In some particularly useful embodiments, the controller 47 is further adapted to calculate the Cu(II) reagent consumption in each vessel V1, V2, Vn in accordance with a formula (Cn,in−Cn,out)/Cn,in*100 where Cn,in, is a concentration of the Cu(II) reagent entering the vessel and Cn,out is the concentration of the Cu(II) reagent leaving the vessel.
Such an apparatus may be said to relate to a method for recovering a target metal from a feed material. That method broadly comprises the steps of: (a) contacting the feed material with a lixiviant adapted to leach the target metal from a feed material feed stream in a leaching circuit, as described above, having a plurality of leaching vessels V1, V2, Vn in series, (b) establishing a countercurrent flow in the leaching circuit by delivering the feed material feed stream to the leaching vessel V1 and moving the feed material feed stream through the leaching circuit in a first direction toward leaching vessel Vn and delivering the lixiviant to the leaching vessel Vn and moving the lixiviant through the leaching circuit in a second direction toward leaching vessel V1, (c) determining, by a controller, a reagent consumption rate for each of the leaching vessels V1, V2, Vn so as to validate performance, minimize left over reagent discharged from leaching vessel V1 and maximize target metal recovery from leaching vessel Vn and (d) recovering the target metal from the lixiviant.
The method may further include calculating, by the controller, the reagent consumption rate for each vessel V1, V2, Vn based upon a formula (Cn,in−Cn,out)/Cn,in*100 where Cn,in is a concentration of the reagent entering the vessel and Cn,out is the concentration of the reagent leaving the vessel. Still further, the method may include using an ammonia-based lixiviant. Alternatively or in addition, the method may include using copper (II) (Cu(II)) as an oxidizer and the reagent. Those skilled in the art will recognize any number of oxidizers may be used such as hydrogen peroxide or metal species which has multiple valances which allow for stable ionic compounds in the lixiviant.
The method may include determining, by the controller, a residence time for the feed material feed stream in each vessel V1, V2, Vn based upon an average particle size of the feed material feed stream.
In some embodiments, the method includes one or more of the following: (a) conducting the leaching under anaerobic conditions, (b) using electronic waste as the feed material and selecting copper metal as the target metal, (c) using electrowinning in the recovering of the copper metal from the lixiviant, and (d) generating Cu(II) ions during electrowinning and using the generated Cu(II) ions as an oxidant for leaching the copper metal in the leaching circuit.
In view of the previous embodiments and descriptions an additional embodiment is provided to describe the conceptual operation of the copper leaching circuits described in
In this embodiment material suitable for leaching is added to leaching vessel number 1. A possible example of the electro-oxidizing species is Cu(NH3)42− ions (Cu(II)). In leach vessel 1, which receives unleached material (represented in
In this embodiment it is assumed that copper is the primary species of interest in the leaching circuit. As such,
As shown in
In this embodiment, electrolyte with a higher Cu(II)/Cu(I) ratio than that exiting the leaching circuit shown in
In an embodiment, the Cu(II) concentration may be used interchangeably with the Cu(II)/Cu(I) ratio as a substitute.
To provide a nonlimiting example of the design of such as circuit as described in the previous embodiment, the following example is provided to show how one skilled in the art may utilize such principles to design and operate such a circuit. An assumption in a continuously stirred tank reactor (CSTR) of which the described lamella clarifiers herein may be considered a subset, is that the concentration of reagents of importance (in this embodiment Cu(II)) in each individual leaching tank may be considered as constant within a tank. In a counter current leaching (CCL) circuit the concentration existing in each tank is different (as described conceptually in
For those skilled in the art to design or operate a leaching circuit as described in the previous embodiments the following principles maybe considered with the following approximations:
1) The concentration in a leaching vessel is considered constant, due to the stirring and assumed ideal mass transfer in tanks.
2) A leaching model indicative of the leaching performance of an individual tank relating to important leaching parameters is identified and utilized. Such parameters considered by the model may be, reagent concentration (in this embodiment Cu(II)), particle size, temperature, etc. which is suitable under a constant concentration of reagent to indicate leaching of performance. This may also be measured practically in situ via Cu(II) measurement or sampling to forgo a leaching model.
3) The circuit is operated in such a manner to minimize the regent leaving the leaching circuit and maximizing the recovery of the metal of interest from the feed material.
To provide a nonlimiting example of utilizing these principles, the following is provided. In consideration of developing a model which describes the leaching behavior or electronic waste, a leaching test was conducted with processed E-Waste of a particular size. A set of leaching experiments were performed where the concentration of Cu(II) was set at the beginning of the experiment and decreased with time. A shrinking core model with a variable concentration is given by Zhuravlev's (Zhuravlev, V. F., Lesokhin, I. G., & Tempelman, R. G. (1948). Kinetics of Reactions in the Formation of Aluminates and the Contribution of Mineralizers to the Process. J. Appl. Chem. USSR, 21(09), 887-890.) changing concentration model, defined as:
Where α is the reacted fraction of Cu; D is the diffusion coefficient, m2/s; Vm is the volume of product formed from 1 mole of the slowest penetrating component; C0 is the initial concentration of reactant, mol/L. Since the concentration C0 in each leaching tank is different the rate constant becomes:
where b is the model-conversion constant written as
C0 is the initial Cu concentration coming in the reaction tank, in g/L.
Referring back to the fitting of Zhuravlev's model using batch experimental data under various Cu(II) concentrations, as presented in
Correspondingly, a justified model for leaching under constant concentration, was developed by adopting the interchangeable k value from Zhuravlev's changing-concentration model into Jander's constant-concentration model (Jander, 1927):
By substituting the solved value for b as 0.002882, the justified model is expressed as:
The form for reacted fraction a can be solved mathematically:
where kj′=0.002882×C0.
To further demonstrate the concept of CCL in CSTR reactors in this embodiment, experimental data was adopted and plotted into the justified model. The resulted Cu concentration (g/L) after each stage of leaching estimated by the justified model is shown in
In the CCL circuit, starting from Tank 1, the solid is the most intact and the lixiviant is the most depleted in the oxidizer. In this case, the predicted value for reacted fraction a in Tank 1 is determined by the constant concentration model where the initial reactant concentration is 4 g/L, as shown in
Applying the following input parameters (as listed in Table B) for a CCL circuit using CSTR, accumulative reacted fraction a was obtained and listed in C. Note that a significant change in the inputs is the rate coefficient, now held as a variable differed by concentrations from tank to tank. The radius of free particles is 1 mm (top size of 2 mm), and the reaction takes place under ambient temperature. The starting lixiviant, composing 35 g/L Cu(II) and 5 g/L Cu(I), enters the CCL circuit at Tank 4, at a flow rate of 500 L/min. The pulp density is 10%. The solid phase, containing 30% wt. of Cu(0), flows through the circuit from Tank 1 at a mass flowrate of 3.33 t/h for total solid, and 1 t/h for Cu(0), respectively. The estimated reaction fraction a listed in Table C, showed a depleting trending for Cu(II) from Tank 4 (most concentrated) to Tank 1 (most depleted). The cumulative a at the end of leaching was 0.97 (97% Cu recovery).
The estimated a were then programmed in a mass-balanced flowsheet, as shown in
In function, there exists an infinitely large number of combinations of feed, concentrations, and residence times to provide satisfactory recoveries of metals and reagent consumption. As an additional non limiting embodiment, the simulation above was changed to a feed of 20 g/L of Cu(II) with the output resulting in shown in
With regard to the practitioner being able to achieve such results as described herein, what may be non-obvious to those skilled in the art is how to achieve in practical terms the operation of a leaching circuit to achieve the simultaneous consumption of reagent with regards to minimizing the outgoing reagent. To provide a non-limiting embodiment demonstrating the techniques to achieve counter current solids residence time and liquid concentration of reagent, the following is provided.
Utilizing a lamella clarifier as previously described, a 100 gallon vessel was feed a liquid 0.5 m2/hr. It can be assumed that the clarifier is of sufficient design to allow the solid/liquid separation under the range of conditions outlined. A circuit was arranged according to
As a further embodiment, methods of measurement and control may be, UV-Vis for Cu(II), ORP measurements corresponding to Cu(II)/Cu(I) ratios, or direct measurement by titration for assaying for lixiviant measurement. In this manner, the control of the leaching circuit may be conducted.
This disclosure may be considered to relate to the following items:
Each of the following terms: “includes”, “including”, “has”, “having”, “comprises”, and “comprising”, and, their linguistic/grammatical variants, derivatives, or/and conjugates, as used herein, means “including, but not limited to”, and is to be taken as specifying the stated component(s), feature(s), characteristic(s), parameter(s), integer(s), or step(s), and does not preclude addition of one or more additional component(s), feature(s), characteristic(s), parameter(s), integer(s), step(s), or groups thereof.
The term “method”, as used herein, refers to steps, procedures, manners, means, or/and techniques, for accomplishing a given task including, but not limited to, those steps, procedures, manners, means, or/and techniques, either known to, or readily developed from known steps, procedures, manners, means, or/and techniques, by practitioners in the relevant field(s) of the disclosed invention.
Terms of approximation, such as the terms about, substantially, approximately, etc., as used herein, refers to: ±10% of the stated numerical value. Use of the terms parallel or perpendicular are meant to mean approximately meeting this condition, unless otherwise specified.
It is to be fully understood that certain aspects, characteristics, and features, of the method of recovering metals from waste material, which are, for clarity, illustratively described and presented in the context or format of a plurality of separate embodiments, may also be illustratively described and presented in any suitable combination or sub-combination in the context or format of a single embodiment. Conversely, various aspects, characteristics, and features, of the method which are illustratively described and presented in combination or sub-combination in the context or format of a single embodiment may also be illustratively described and presented in the context or format of a plurality of separate embodiments.
The foregoing has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Obvious modifications and variations are possible in light of the above teachings. For example, the apparatus may be arranged so that the solid phase/feed material is maintained in a single vessel throughout processing but the liquid phase is manipulated in a manner to approximate a countercurrent flow. Further, illustrated embodiments refer to shredding of the waste material prior to processing. Other alternative or additional methods of preparing the waste material for processing include but are not limited to sizing the waste material by means other than shredding, removing ferro-magnetic materials by pretreatment with a magnet, pretreatment by eddy-current or sensor sorting and the like. All such modifications and variations are within the scope of the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.
This application claims priority to U.S. Provisional Patent Application Ser. No. 63/315,322 filed on Mar. 1, 2022, U.S. Provisional Patent Application No. 63/398,695 filed on Aug. 17, 2022, and U.S. Provisional Patent Application Ser. No. 63/447,313 filed on Feb. 21, 2023 which are hereby incorporated by reference in their entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US23/14254 | 3/1/2023 | WO |
Number | Date | Country | |
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63315322 | Mar 2022 | US | |
63398695 | Aug 2022 | US | |
63447313 | Feb 2023 | US |