Method for recycling lithium-ion secondary battery

Abstract

According to an embodiment of the present invention, a valuable metal reactant comprises a first valuable metal-containing material, a second valuable metal-containing material, and carbon which are recovered from waste batteries, and satisfies Expression 1, wherein the first valuable metal-containing material includes at least one of nickel (Ni), cobalt (Co), or manganese (Mn) in the form of a metal or an oxide, and the second valuable metal-containing material may include a non-magnetic material. [Expression 1] 0.2 ≤ ([O]) / ([Ni]+[Co]+[Mn]) ≤ 1.2 In Expression 1, [O], [Ni], [Co], and [Mn] refer to the mol% of the respective elements.

Description

Lithium-ion secondary battery recycling method

[0001] The present invention relates to valuable metal reactants recovered from spent lithium-ion batteries and a method for recovering transition metals from spent lithium-ion batteries.

[0002] With the recent emergence of global warming as a major issue, the demand for and adoption of electric vehicles (EVs) for carbon reduction are increasing. This explosive growth in EV usage will result in a large volume of discarded electric vehicles in the near future. Since these scrapped vehicles contain valuable metallic elements such as nickel, cobalt, manganese, and lithium, the importance of resource recycling is being highlighted.

[0003] These metals are core components of electric vehicle batteries, and despite being limited resources, industrial demand is very high. Therefore, there is an urgent need to develop technologies and systems to efficiently recover and recycle these valuable metals from scrapped electric vehicle batteries. This can reduce resource waste and increase economic value, while also making a significant contribution to environmental protection.

[0004] For the recycling of secondary batteries, the batteries are processed through crushing, grinding, gravity separation, and magnetic separation to produce black powder, which is a mixture of cathode and anode materials. This black powder contains, for example, oxides of nickel, cobalt, manganese, lithium, aluminum, and oxygen as cathode materials, as well as graphite and mixtures thereof as anode materials, and some impurities such as aluminum and copper. Methods for recovering valuable metals from this black powder are broadly divided into wet processes and dry processes.

[0005] The advantage of the dry process is that the time required for the leaching process is reduced by about 70% compared to the wet process. This is because the leaching process can proceed faster since the graphite is dissolved within the alloy.

[0006] However, the dry process presents several significant challenges. First, valuable metals such as lithium and aluminum are consumed as slag, making recovery difficult. This not only reduces resource efficiency but can also result in substantial economic losses.

[0007] Second, the large amount of carbon dioxide generated when oxygen is blown in to remove graphite during the high-temperature dry process can cause environmental problems. This may result in outcomes contrary to global efforts to reduce carbon emissions and undermine the environmental sustainability of the recycling process.

[0008] The objective of the present invention to solve the aforementioned problem is to provide a valuable metal reactant recovered from a spent lithium-ion battery and a method for recovering a transition metal from a spent lithium-ion battery.

[0009] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0010] As a means to achieve the above-mentioned purpose, a valuable metal reactant according to one embodiment of the present invention comprises a first valuable metal containing material, a second valuable metal containing material, and carbon recovered from a waste battery, satisfying Formula 1 below, wherein the first valuable metal containing material comprises at least one of nickel (Ni), cobalt (Co), and manganese (Mn) in the form of a metal or oxide, and the second valuable metal containing material may comprise a non-magnetic material.

[0011] [Equation 1]

[0012] 0.2 ≤ ([O]) / ([Ni]+[Co]+[Mn]) ≤ 1.2

[0013] In the above Equation 1, [O], [Ni], [Co], and [Mn] represent the mol% of each element.

[0014] In a valuable metal reactant according to one embodiment of the present invention, the first valuable metal containing material may be characterized in that, when X-ray diffraction (XRD) is performed, the ratio of the intensity of the Ni peak to the intensity of the Co-Mn oxide peak is 1.5 to 9.0.

[0015] In a valuable metal reactant according to one embodiment of the present invention, the first valuable metal containing material may be characterized by having a Ni (111) peak at a position of 44.4° to 44.8° when analyzed by X-ray diffraction (XRD).

[0016] In a valuable metal reactant according to one embodiment of the present invention, the content of aluminum (Al) in the first valuable metal containing material may be 1.5 wt% or less.

[0017] In a valuable metal reactant according to one embodiment of the present invention, the content of copper (Cu) in the first valuable metal containing material may be 1 wt% or less.

[0018] In a valuable metal reactant according to one embodiment of the present invention, the Co-Mn oxide particles in the first valuable metal containing material may include one or more of MnO2, MnO, Mn2O3, Mn3O4, CoO, Co2O3, Co3O4, MnCo2O4, and CoMn2O4.

[0019] In a valuable metal reactant according to one embodiment of the present invention, the first valuable metal content may include a Ni aggregate structure with a size of less than 20 μm.

[0020] In a valuable metal reactant according to one embodiment of the present invention, the second valuable metal containing material may include at least one of Cu, Al, Al2O3, LiAlO2, Li5AlO4, LiAl5O8, Li2CO3, LiF, Li3PO4, Li4P2O7, LiPO3, Li2SiO3, Li4SiO4, Li2Si2O5, LiFeO2, LiFe5O8, Li3Fe5O8, and Li5FeO4.

[0021] A method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention may include: a step of generating a reducing gas by thermally decomposing a separator, an outer material, and a binder present in the shredded spent lithium-ion battery; a step of obtaining a valuable metal reactant by reducing Ni with the reducing gas; a magnetic separation step of separating the valuable metal reactant into a first valuable metal containing material and a second valuable metal containing material; a step of separating Cu contained in the second valuable metal containing material; and a step of separating a lithium compound contained in the second valuable metal containing material.

[0022] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of generating the reducing gas may be characterized by injecting at least one of the inert gases Ar, He, and N2 to lower the oxygen concentration.

[0023] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the reducing gas generated by thermally decomposing the separator, outer material, and binder may be characterized as being at least one of H2, CxHy (1≤x≤10, 3≤y≤22), and NH3.

[0024] A method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention may further include a step of removing impurities by magnetic separation after the step of generating the reducing gas.

[0025] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of reducing the Ni may be characterized by being performed in a reducing atmosphere in which the O2 concentration is 2% or less.

[0026] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of reducing Ni may be characterized by being performed at 400 to 700°C.

[0027] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of reducing Ni may be characterized by maintaining the maximum reduction reaction temperature for 30 minutes or more.

[0028] In a method for recovering a transition metal from a waste lithium-ion battery according to one embodiment of the present invention, the step of separating Cu contained in the second valuable metal inclusion may be performed by at least one of a ball mill, a cup mill, a lot mill, a hammer mill, and an attrition mill.

[0029] A method for recovering a transition metal from a waste lithium-ion battery according to one embodiment of the present invention further comprises, after the step of separating Cu from the second valuable metal inclusion, a step of separating carbon from the second valuable metal inclusion, wherein the separation may be performed by at least one of particle size separation, cyclone separation, gravity separation, and flotation separation.

[0030] According to one embodiment of the present invention, a valuable metal reactant recovered from a spent lithium-ion battery and a method for recovering a transition metal from a spent lithium-ion battery can be provided.

[0031] The effects obtainable from this invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which this invention pertains from the description below.

[0032] Figure 1 is a figure showing the gas generated when waste lithium-ion battery crushed material is heat-treated at 500°C with an O21% or less.

[0033] Figure 2 is a figure showing X-ray diffraction (XRD) measurement data of the first valuable metal inclusion.

[0034] Figure 3 is a scanning electron microscope (SEM) image of the first valuable metal containing a valuable metal reactant.

[0035] Figure 4 shows the Ni content of a valuable metal inclusion captured by Energy Dispersive Spectroscopy (EDS).

[0036] Figure 5 shows the O content of the first valuable metal inclusion captured by Energy Dispersive Spectroscopy (EDS).

[0037] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0038] The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof.

[0039] Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense.

[0040] Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0041] Unless otherwise specifically stated in this specification, the % indicating the content of each element is based on weight. The reasons for limiting the compositional range of each alloying element are explained below.

[0042] For the recycling of secondary batteries, the batteries are processed through crushing, grinding, gravity separation, and magnetic separation to produce black powder, which is a mixture of cathode and anode materials. This black powder contains, for example, oxides of nickel, cobalt, manganese, lithium, aluminum, and oxygen as cathode materials, as well as graphite and mixtures thereof as anode materials, and some impurities such as aluminum and copper. Methods for recovering valuable metals from this black powder are broadly divided into wet processes and dry processes.

[0043] Among them, the wet process produces NiSO4, CoSO4, MnSO4, and Li2CO3 through leaching, solvent extraction, and lithium production. When the black powder is processed by the wet process, there is a problem in that the graphite, which is the cathode material contained in the black powder, does not dissolve in a strong acid atmosphere, resulting in an excessively long leaching process time, and there is a problem in that the yield is reduced as the black powder is separated together with the graphite.

[0044] On the other hand, the dry process is a method of recovering valuable metals by processing black powder at high temperatures. This process is carried out at high temperatures, for example, between 1400°C and 1600°C, and graphite and oxygen are introduced to reduce the Ni-Mn-Li-Al-O oxides within the black powder at high temperatures, generating CO or CO2 gas in the process. The results of this process include a Ni-Co-Mn alloy and lithium and aluminum separated in the form of slag. The Ni-Co-Mn alloy produced through the dry process can subsequently be converted into useful metal compounds such as NiSO4, CoSO4, and MnSO4 through the same wet process described above.

[0045] A lithium-ion secondary battery recycling method according to one embodiment of the present invention can minimize the oxidation of graphite present in the crushed waste lithium-ion battery by reducing Ni at a temperature of 400 to 700°C, which is lower than that of conventional methods. Therefore, the problem of excessive carbon dioxide generation when oxygen is blown in to remove graphite in a high-temperature dry process can be improved.

[0046] NCM-based rechargeable batteries are largely composed of a current collector, a cathode material, a negative electrode material, a separator, and an electrolyte. First, copper and aluminum are used as current collectors, responsible for transmitting the current generated at the electrodes to the external circuit. The cathode material consists of oxides containing lithium, nickel, cobalt, and manganese. Graphite is primarily utilized as the negative electrode material, serving to store and release electrons. Additionally, a separator is included to physically separate the cathode and negative electrodes while allowing the movement of ions. The electrolyte is injected into the separator and plays a crucial role as a medium mediating conductive ions. The electrolyte consists of a solvent and a salt. As the solvent, a mixture of organic carbonates, such as ethylene carbonate and propylene carbonate, may be used. LiPF6 is typically used as the salt, contributing to increasing the ionic conductivity of the electrolyte. These components combine to form the rechargeable battery.

[0047] Waste battery composed of the above-mentioned current collector, positive electrode material, negative electrode material, separator, and electrolyte can be completely discharged, dismantled, and crushed to prepare shredded waste battery material. By crushing the waste battery, the surface area in contact with oxygen is increased, thereby improving reaction efficiency.

[0048] The above waste battery crushed material may include not only crushed materials of the current collector, positive electrode material, negative electrode material, separator, and electrolyte as described above, but also defective products generated during the manufacturing process, residues within the manufacturing process, and generated debris.

[0049] A valuable metal reactant according to one embodiment of the present invention is recovered from crushed waste batteries and comprises a first valuable metal containing material, a second valuable metal containing material, and carbon, and satisfies Formula 1 below.

[0050] [Equation 1]

[0051] 0.2 ≤ ([O]) / ([Ni]+[Co]+[Mn]) ≤ 1.2

[0052] In the above Equation 1, [O], [Ni], [Co], and [Mn] represent the mol% of each element.

[0053] Figure 3 is a scanning electron microscope (SEM) image of a valuable metal reactant. Table 1 below shows the results of quantitative elemental analysis using Energy Dispersive Spectroscopy (EDS) on three randomly selected spots from the valuable metal reactant shown in the image of Figure 3.

[0054] Classification O(mol%) Al(mol%) Mn(mol%) Co(mol%) Ni(mol%) Formula 1 Value 1 18.5 7 1.1 98.1 79.3 76 2.7 0.2 32 47.7 70.8 27.6 78.8 03 4.9 40.9 33 41.9 20.9 98.3 99.6 23 9.0 80.73

[0055] Referring to Table 1 above, it can be confirmed that the analysis result of the valuable metal reactant according to one embodiment of the present invention satisfies Equation 1.

[0056] The first valuable metal inclusion may include at least one of nickel (Ni), cobalt (Co), and manganese (Mn) in the form of a metal or oxide.

[0057] The above second valuable metal inclusion may include a non-magnetic material.

[0058] In a valuable metal reactant according to one embodiment of the present invention, the first valuable metal containing material may be characterized in that, when X-ray diffraction (XRD) is performed, the ratio of the intensity of the Ni peak to the intensity of the Co-Mn oxide peak is 1.5 to 9.0.

[0059] X-ray diffraction (XRD) analysis using Cu(Kα-rays) was performed on the first valuable metal inclusion. XRD characteristics were measured using Rigaku’s SMARTLAB instrument. The first valuable metal inclusion contains a mixture of Ni and Co-Mn. Figure 2 shows the X-ray diffraction analysis measurement data of the first valuable metal inclusion. Referring to Figure 2, it can be seen that the ratio of the intensity of the Ni peak to the intensity of the Co-Mn peak is 1.5. This can increase from 1.5 to 9.0 depending on the NCM ratio.

[0060] In a valuable metal reactant according to one embodiment of the present invention, the first valuable metal containing material may be characterized by having a Ni (111) peak at a position of 44.4° to 44.8° when analyzed by X-ray diffraction (XRD).

[0061] In a valuable metal reactant according to one embodiment of the present invention, the content of aluminum (Al) in the first valuable metal containing material may be 1.5 wt% or less.

[0062] In a valuable metal reactant according to one embodiment of the present invention, the content of copper (Cu) in the first valuable metal containing material may be 1 wt% or less.

[0063] In a valuable metal reactant according to one embodiment of the present invention, the Co-Mn oxide particles in the first valuable metal containing material may include one or more of MnO2, MnO, Mn2O3, Mn3O4, CoO, Co2O3, Co3O4, MnCo2O4, and CoMn2O4.

[0064] In a valuable metal reactant according to one embodiment of the present invention, the first valuable metal inclusion may include a Ni aggregate structure with a size of less than 20 μm. FIG. 3 is a photograph of the first valuable metal inclusion taken with a scanning electron microscope (SEM). FIG. 4 and FIG. 5 are images of the content of Ni and O at the same location taken with energy dispersive X-ray spectroscopy (EDS), respectively. Since the O concentration in FIG. 5 is low, corresponding to the high Ni concentration in the brightly visible part of FIG. 4, it can be confirmed that Ni has been reduced. As Ni is reduced, aggregation occurs, and it can be confirmed that a Ni aggregate structure with a size of less than 20 μm is formed in FIG. 3.

[0065] In a valuable metal reactant according to one embodiment of the present invention, the second valuable metal containing material may include at least one of Cu, Al, Al2O3, LiAlO2, Li5AlO4, LiAl5O8, Li2CO3, LiF, Li3PO4, Li4P2O7, LiPO3, Li2SiO3, Li4SiO4, Li2Si2O5, LiFeO2, LiFe5O8, Li3Fe5O8, and Li5FeO4.

[0066] Hereinafter, a method for recovering transition metals from spent lithium-ion batteries according to the present invention is described. A method for recovering transition metals from spent lithium-ion batteries according to one embodiment of the present invention may include: a step of generating a reducing gas by thermally decomposing a separator, outer material, and binder present in the shredded spent lithium-ion battery; a step of obtaining a valuable metal reactant by reducing Ni with the reducing gas; a magnetic separation step of separating the valuable metal reactant into a first valuable metal containing material and a second valuable metal containing material; a step of separating Cu contained in the second valuable metal containing material; and a step of separating a lithium compound contained in the second valuable metal containing material.

[0067] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of generating the reducing gas may be characterized by injecting at least one of the inert gases Ar, He, and N2 to lower the oxygen concentration.

[0068] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the reducing gas generated by thermally decomposing the separator, outer material, and binder may be characterized as being at least one of H2, CxHy (1≤x≤10, 3≤y≤22), and NH3.

[0069] A method for recovering transition metals from spent lithium-ion batteries according to one embodiment of the present invention may further include a step of removing impurities by magnetic separation after the step of generating the reducing gas. Impurities such as Fe can be separated through the magnetic separation. For example, the magnetic separation may be performed by using a magnetic material to separate particles through contact with the magnetic material, and various types of magnetic separation methods may be applied.

[0070] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of reducing the Ni may be characterized by being performed in a reducing atmosphere in which the O2 concentration is 2% or less.

[0071] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of reducing Ni may be characterized by being performed at 400 to 700°C.

[0072] When heat treatment is performed in a reducing atmosphere of 400°C or higher, H2 is mainly generated as plastics (separators, outer materials, binders, etc.) contained in the shredded waste battery material undergo thermal decomposition, and some CO2 gas is also formed due to the oxidation of graphite and plastics. In addition, CO and CH4 gases are formed. Figure 1 is a figure showing the gases generated when shredded waste battery material is heat-treated at 500°C with an O2 content of 1% or less.

[0073] H2 and CO generated according to the above heat treatment process 2, Due to gases such as CO and CH4, at temperatures above 400°C, the complex metal oxide composed of lithium-nickel-cobalt-manganese in the waste battery shreds undergoes a reduction process, and the nickel oxide among the complex metal oxides is converted into a metallic form.

[0074] According to one embodiment of the present invention, reduction heat treatment can be performed at a lower temperature than a conventional heat treatment process, thereby minimizing the oxidation of graphite and minimizing the emission of greenhouse gases such as CO2.

[0075] The biggest change after the reduction heat treatment process is that nickel regains its magnetism. Nickel is a metal and possesses magnetism, but the lithium-nickel-cobalt-manganese composite oxide (anode material) does not exhibit magnetism. However, when reduced to the nickel metal form as described above, it regains its magnetism according to its original properties.

[0076] In a method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention, the step of reducing Ni may be characterized by maintaining the maximum reduction reaction temperature for 30 minutes or more.

[0077] In a method for recovering a transition metal from a waste lithium-ion battery according to one embodiment of the present invention, the step of separating Cu contained in the second valuable metal inclusion may be performed by at least one of a ball mill, a cup mill, a lot mill, a hammer mill, and an attrition mill.

[0078] A method for recovering a transition metal from a spent lithium-ion battery according to one embodiment of the present invention may further include a step of separating carbon from the second valuable metal inclusion after the step of separating Cu from the second valuable metal inclusion. Additionally, the separation may be performed by at least one of particle size separation, cyclone separation, gravity separation, and flotation separation.

[0079] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and those skilled in the art will understand that various changes and modifications are possible within the scope and concept of the claims set forth below.

Claims

1. A valuable metal reactant comprising a first valuable metal containing material, a second valuable metal containing material, and carbon recovered from a waste battery, satisfying Formula 1 below, The first valuable metal inclusion comprises at least one of nickel (Ni), cobalt (Co), and manganese (Mn) in the form of a metal or oxide, and The above second valuable metal inclusion is a valuable metal reactant comprising a non-magnetic material: [Equation 1] 0.2 ≤ ([O]) / ([Ni]+[Co]+[Mn]) ≤1.2 In the above Equation 1, [O], [Ni], [Co], and [Mn] represent the mol% of each element.

2. In Claim 1, The first valuable metal containing material is characterized by having a ratio of the intensity of the Ni peak to the intensity of the Co-Mn oxide peak of 1.5 to 9.0 when analyzed by X-ray diffraction (XRD), and is a valuable metal reactant.

3. In Claim 1, The above first valuable metal containing material is characterized by having a Ni (111) peak at a position of 44.4° to 44.8° when analyzed by X-ray diffraction (XRD), a valuable metal reactant.

4. In Claim 1, A valuable metal reactant in which the aluminum (Al) content in the first valuable metal content is 1.5 wt% or less.

5. In Claim 1, A valuable metal reactant in which the copper (Cu) content in the first valuable metal inclusion is 1 wt% or less.

6. In Claim 1, The Co-Mn oxide particles in the first valuable metal inclusion are a valuable metal reactant comprising one or more of MnO2, MnO, Mn2O3, Mn3O4, CoO, Co2O3, Co3O4, MnCo2O4, and CoMn2O4.

7. In Claim 1, The first valuable metal content is a valuable metal reactant comprising a Ni aggregate structure with a size of less than 20 μm.

8. In Claim 1, The second valuable metal containing above is a valuable metal reactant comprising at least one of Cu, Al, Al2O3, LiAlO2, Li5AlO4, LiAl5O8, Li2CO3, LiF, Li3PO4, Li4P2O7, LiPO3, Li2SiO3, Li4SiO4, Li2Si2O5, LiFeO2, LiFe5O8, Li3Fe5O8, and Li5FeO4.

9. A method for recovering transition metals from spent lithium-ion batteries, A step of generating reducing gas by thermally decomposing the separator, outer material, and binder present in the shredded waste lithium-ion battery material; A step of obtaining a valuable metal reactant by reducing Ni with the above-mentioned reducing gas; A magnetic separation step for separating the above valuable metal reactant into a first valuable metal content and a second valuable metal content; A step of separating Cu contained in the second valuable metal inclusion; A method comprising the step of separating a lithium compound contained in the second valuable metal inclusion.

10. In Claim 9, A method characterized by the step of generating the reducing gas by injecting at least one of the inert gases Ar, He, and N2 to lower the oxygen concentration.

11. In Claim 9, A method characterized in that the reducing gas generated by thermally decomposing the above-mentioned separator, outer material, and binder is at least one of H2, CxHy (1≤x≤10, 3≤y≤22) and NH3.

12. In Claim 9, A method characterized by further including a step of removing impurities by magnetic separation after the step of generating the reducing gas.

13. In Claim 9, A method characterized in that the step of reducing the above Ni is performed in a reducing atmosphere in which the O2 concentration is 2% or less.

14. In Claim 9, A method characterized in that the step of reducing the above Ni is performed at 400 to 700°C.

15. In Claim 9, A method characterized in that the step of reducing Ni is maintained at a maximum reduction reaction temperature for a time of 30 minutes or more.

16. In Claim 9, A method in which the step of separating Cu contained in the second valuable metal inclusion is performed by at least one of a ball mill, a cup mill, a lot mill, a hammer mill, and an attrition mill.

17. In Claim 9, After the step of separating Cu from the second valuable metal inclusion, The above-mentioned second valuable metal inclusion further includes a step of separating carbon, and The above separation is performed by at least one of particle size separation, cyclone separation, gravity separation, and flotation separation.

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