Method for separating and recovering metal ions

Abstract

To provide a method that enables easy and selective separation and recovery of metal ions.SOLUTION: According to one embodiment, a method for separating and recovering metal ions is provided. The method includes dispersing composite particles containing substrate particles and a metal extractant in an aqueous solution containing one or more first metal ions, selectively adsorbing the first metal ions onto the composite particles, separating the composite particles having adsorbed the first metal ions from the aqueous solution, and replacing the first metal ions adsorbed onto the composite particles with second metal ions to desorb the first metal ions from the composite particles for recovery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a method for separating and recovering metal ions. [Background technology]

[0002] The recovery of rare earth ions from aqueous solutions has been attracting attention from the perspective of recycling rare earth elements and recovering valuable materials. Solvent extraction is used industrially to separate and recover rare earth ions. This method involves contacting an aqueous solution containing the target metal elements with an organic phase consisting of various extractants and organic solvents to dilute them. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-1584 [Patent Document 2] International Publication No. WO2013 / 011901 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-186020 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-147948 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide a method for easily and selectively separating and recovering metal ions. [Means for solving the problem]

[0005] According to an embodiment, a method for separating and recovering metal ions is provided, which includes dispersing composite particles, each containing a base particle and a metal extractant, in an aqueous solution containing one or more first metal ions, selectively adsorbing the first metal ions onto the composite particles, separating the composite particles with the adsorbed first metal ions from the aqueous solution, and substituting the first metal ions adsorbed onto the composite particles with second metal ions, followed by desorption and recovery of the second metal ions from the composite particles. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a conceptual diagram showing one stage in an example of a metal ion separation and recovery method according to an embodiment. [Figure 2] FIG. 4 is a conceptual diagram showing another step in an example of a method for separating and recovering metal ions according to an embodiment. [Figure 3] FIG. 4 is a conceptual diagram showing another step in an example of a method for separating and recovering metal ions according to an embodiment. [Figure 4] FIG. 4 is a conceptual diagram showing another step in an example of a method for separating and recovering metal ions according to an embodiment. [Figure 5] FIG. 1 is a schematic cross-sectional view illustrating an example of a composite particle according to an embodiment. [Figure 6] FIG. 4 is a schematic cross-sectional view showing another example of a composite particle according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] When components of products that use rare earth elements or other metals are treated for recycling as resources, for example, an aqueous solution containing metal ions is generated. It may be necessary to recover the metal ions contained in such an aqueous solution as metals or metal compounds and reuse them as resources. In particular, the separation and recovery of rare earth elements and other rare metals is attracting attention from the perspective of sustainability.

[0008] In treatment processes that involve separation and extraction steps, such as solvent extraction, which is known as a method for separating and recovering rare earth elements, organic solvents are used in the extractant phase. Therefore, the introduction of explosion-proof equipment to ensure safety is a factor in increasing costs. Therefore, there is a demand for treatment processes that do not use organic solvents.

[0009] The metal ion separation and recovery method according to the present embodiment includes dispersing composite particles containing base particles and a metal extractant in an aqueous solution containing one or more first metal ions, selectively adsorbing the first metal ions onto the composite particles, separating the composite particles with the adsorbed first metal ions from the aqueous solution, and desorbing and recovering the first metal ions adsorbed onto the composite particles. The desorption of the first metal ions from the composite particles is achieved by replacing the first metal ions with second metal ions different from the first metal ions.

[0010] The separation and recovery method is a method for separating and recovering metal ions from an aqueous solution containing one or more types of metal ions. The metal ions in the aqueous solution include, for example, ions of rare metals and rare earth elements. One or more types of metal ions contained in the aqueous solution to be treated from which metal ions are recovered are separated and recovered. Hereinafter, the metal ions contained in the aqueous solution and intended to be separated and recovered are referred to as first metal ions. Regardless of whether the type of metal ion to be separated and recovered from the aqueous solution is one type or two or more types, they are collectively referred to as first metal ions. The type of metal ion referred to here refers to the ion species.

[0011] This separation and recovery method uses composite particles containing a metal extractant suitable for selective adsorption and separation of metal ions and base particles, making it possible to easily separate and recover target metal ions even from aqueous solutions containing a mixture of multiple metal ions. Therefore, valuable metals can be reused by separating and recovering them from mixed solutions containing rare earth ions, etc. Furthermore, since the composite particles can be physically recovered from the solution, the use of organic solvents is unnecessary. In other words, with the above separation and recovery method, the only treatment using a solvent is in the aqueous solution, eliminating the need for measures such as explosion-proof equipment that are required when using organic solvents.

[0012] The aqueous solution from which the first metal ions are recovered by this separation and recovery method may be, for example, an aqueous solution produced during resource recovery processing from components of electronic devices or the like. The aqueous solution may contain one type of metal ion. Alternatively, the aqueous solution may contain multiple types of metal ions. This separation and recovery method can recover some or all of one or multiple types of metal ions as the first metal ions. The recovered first metal ions are, for example, recovered as the first metal element or a metal compound.

[0013] The metal ions contained in the aqueous solution are not limited to ions of rare earth elements or other rare metals. All metal ions contained in the aqueous solution, including rare metal ions and other metal ions, may be separated and recovered as the first metal ions, or only a portion of them may be separated and recovered. Typically, priority is given to the recovery of rare metals such as rare earth elements.

[0014] Composite particles containing substrate particles and a metal extractant are dispersed in an aqueous solution containing one or more first metal ions, thereby contacting the first metal ions with the metal extractant. This allows the first metal ions to be selectively adsorbed onto the composite particles. Conditions such as the pH of the aqueous solution may be adjusted to ensure that the first metal ions are dissolved as ions in the aqueous solution, rather than precipitated as salts. The aqueous solution may also be stirred using a stirrer or the like to promote dispersion of the composite particles.

[0015] The composite particles include a base particle and a metal extractant. The composite particles may be, for example, those in which the metal extractant is immobilized on the surface of the base particle by physical adsorption or chemical adsorption. The composite particles may further have an acid-resistant layer on the surface of the base particle. The aqueous solution from which the first metal ions are recovered may be an acidic solution. Therefore, it is desirable to impart acid resistance to the base particle by, for example, silica coating. In composite particles in which the base particle is coated with an acid-resistant layer, the coated particle including the base particle and the acid-resistant layer on its surface is considered to be the base, and the metal extractant may be immobilized on the surface of the coated particle by physical adsorption or chemical adsorption.

[0016] The base particles are not particularly limited as long as they can form composite particles together with the metal extractant. It is preferable to increase the surface area of ​​the composite particles to improve separation and recovery performance, and for this purpose, for example, nanoparticles can be used as the base particles. The base particles can be magnetic particles. When magnetic particles are used, the composite particles can be separated from the aqueous solution using magnetic force, specifically, the attractive force generated in a magnetic field.

[0017] The magnetic particles are not particularly limited as long as they are particles of a magnetic material. A specific example is iron tetroxide (Fe3O4). In order to improve separation and recovery performance, it is preferable to increase the surface area of ​​the composite particles. For this purpose, for example, nanoparticles can be used as the magnetic particles.

[0018] The metal extractant used is a substance that chemically bonds with the first metal ion. For example, a substance containing a ligand that bonds with the first metal ion to form a metal complex is used as the metal extractant. A specific example is a chelating agent such as ethylenediaminetetraacetate (EDTA), which forms a chelate compound with the metal ion.

[0019] When the aqueous solution contains multiple types of first metal ions to be recovered, it is desirable to use a substance containing a ligand that forms metal complexes with different stability constants for each type of first metal ion as the metal extractant. The larger the value of the stability constant for complex formation, the more stable the metal complex is in the aqueous solution. Therefore, the metal extractant selectively binds to the first metal ion that forms a complex with a larger stability constant. Therefore, the metal ion in the aqueous solution with the highest stability constant for the metal complex with the metal extractant is selectively adsorbed onto the composite particles as the first metal ion. By utilizing this selectivity, the first metal ions can be sequentially adsorbed and separated, starting with the first metal ion with the largest stability constant of the corresponding metal complex.

[0020] An example of the difference in stability constants of metal complexes for each metal ion is shown in Table 1 below. In the example below, the stability constants of metal-EDTA complexes are shown for cations of erbium (Er), yttrium (Y), titanium (Ti), and magnesium (Mg). In the example of the metal ion group shown in Table 1, Er 3+ ,Y 3+ ,Ti 4+ ,Mg 2+ In this order, the metals are selectively adsorbed onto composite particles containing EDTA as an extractant. The chemical structure of the Er-EDTA complex is shown as a specific example.

[0021] [Table 1]

[0022] [ka]

[0023] The stability constants of metal complexes tend to be as follows: For the same ligand, the higher the valence of the ion, the larger the stability constant. Also, for ions with the same valence, the smaller the ionic radius, the larger the stability constant.

[0024] The method for separating the composite particles that have adsorbed the first metal ions from the aqueous solution is not particularly limited, and examples thereof include centrifugation, coagulation sedimentation, etc. When magnetic particles are used as the base particles, separation using magnetic force becomes possible.

[0025] When separating the composite particles from the aqueous solution using magnetic force, for example, the composite particles are pulled up from the aqueous solution using magnetic force. Alternatively, the composite particles are attracted to the inner wall or bottom of a tank or container containing the aqueous solution using magnetic force, and the aqueous solution is then allowed to flow out. As a specific example, the composite particles can be pulled up using an electromagnetic crane, or the aqueous solution can be allowed to flow out while the composite particles are magnetically attracted to an electromagnet.

[0026] To release the first metal ion from the composite particles separated from the aqueous solution, the first metal ion bound to the metal extractant is replaced with a second metal ion. For example, the composite particles adsorbing the first metal ion separated from the aqueous solution (first aqueous solution) are dispersed in another aqueous solution (second aqueous solution) containing the second metal ion. It is desirable to promote the replacement of the first metal ion with the second metal ion. For example, by increasing the concentration of the second metal ion, the equilibrium in the second aqueous solution is shifted toward the state in which the second metal ion and the metal extractant are bound. Alternatively, the metal extractant, the second metal ion, or both are selected so that the state in which the metal extractant and the two metal ions are bound is more stable than the state in which the metal extractant and the first metal ion are bound. The latter can be achieved by using a metal extractant containing a ligand that binds with the first metal ion to form a metal complex.

[0027] When a metal extractant containing a ligand that forms a metal complex with a first metal ion is used, for example, a metal ion having a higher stability constant of the metal complex than the first metal ion is used as the second metal ion. As described above, a metal complex with a larger stability constant is more likely to be stable as a complex in aqueous solution, so the first metal ion bound to the metal extractant is replaced with the second metal ion to form a complex with a larger stability constant.

[0028] Table 2 shows examples of metal ions that are effective as second metal ions for composite particles that adsorb the metal ions shown in Table 1 above as first metal ions. Here, the stability constants of metal-EDTA complexes for zirconia (Zr) and iron (Fe) ions are shown as highly practical examples due to their ease of handling and availability. Zr 4+ and Fe 3+ has a higher stability constant for the complex with EDTA compared to the metal ions listed in Table 1, and therefore exhibits an advantage in forming metal-EDTA complexes over the metal ions listed in Table 1.

[0029] [Table 2]

[0030] The first metal ions substituted with the second metal ions are recovered from the remaining second aqueous solution, for example, by separating the composite particles to which the second metal ions are adsorbed from the second aqueous solution. For example, the first metal is precipitated in the second aqueous solution either as a single substance or as a metal compound. In addition to the second metal ions, which are cations, the second aqueous solution may contain a component that can function as a counter anion. This counter anion may combine with the first metal ions to produce a compound of the first metal. Alternatively, a separate anion source may be added and reacted with the first metal ions to produce a compound of the first metal.

[0031] The composite particles that have adsorbed the second metal ions can be easily separated from the second aqueous solution using magnetic force. For example, the composite particles can be pulled up from the aqueous solution using magnetic force. Alternatively, the composite particles can be attracted to the inner wall or bottom of a tank or container containing the aqueous solution using magnetic force, and the aqueous solution can then be drained. Separation using magnetic force becomes possible when magnetic particles are used as the base particles. Separation of composite particles is not limited to methods using magnetic force, and can also be performed using methods such as centrifugation and coagulation sedimentation. Regardless of whether magnetic particles are used, separation can also be performed using methods that do not use magnetic force.

[0032] By releasing the second metal ions from the composite particles, the composite particles can be reused. For example, composite particles with adsorbed second metal ions can be placed in a third aqueous solution, and the second metal ions can be released by adjusting the pH of the aqueous solution. Although this differs depending on the metal ion type and ligand, there is a lower limit to the pH at which metal ions and ligands can form complexes. By lowering the pH of the third aqueous solution beyond this lower limit, the second metal ions can be released from the composite particles in solution. The composite particles from which the second metal ions have been released can be recovered from the third aqueous solution and re-dispersed in the first aqueous solution for reuse. The second metal ions released from the composite particles can be added to the second aqueous solution for reuse. For example, the third aqueous solution containing the second metal ions remaining after separating the composite particles can be mixed with the second aqueous solution, or the concentration, pH, etc. of the third aqueous solution can be readjusted and then reused in the second aqueous solution.

[0033] Separation of the composite particles from the third aqueous solution for reuse can be facilitated by using magnetic force. For example, the composite particles can be pulled out of the aqueous solution using magnetic force. Alternatively, the composite particles can be attracted to the inner wall or bottom of a tank or container containing the third aqueous solution using magnetic force, and the third aqueous solution can then be moved for reuse in the second aqueous solution. Separation using magnetic force becomes possible when magnetic particles are used as the base particles. Separation of the composite particles is not limited to methods using magnetic force, and can also be performed using methods such as centrifugation and coagulation sedimentation. Regardless of whether magnetic particles are used, separation can also be performed using methods that do not use magnetic force.

[0034] When the initial first aqueous solution contains two or more types of first metal ions to be recovered, the first metal ions can be individually recovered by repeatedly adsorbing and separating the first metal ions one by one in descending order of their selectivity for the composite particles. For example, a metal extractant that forms a complex with the first metal ion is used to selectively adsorb the metal ion with the highest stability constant of the metal complex onto the composite particles, replacing the first metal ion adsorbed onto the composite particles with a second metal ion and desorbing it from the composite particles for recovery, desorbing the second metal ion from the composite particles, and recovering the composite particles from which the second metal ion has been desorbed and redispersing them in an aqueous solution. This process is repeated to adsorb and separate the first metal ions in descending order of the stability constant of the metal complex.

[0035] Specific examples of the metal ion separation and recovery method according to the embodiment will be described below with reference to the drawings. The following example corresponds to one embodiment in which magnetic particles are used as base particles, and the base particles can be recovered from an aqueous solution using magnetic force. The metal ion separation and recovery method according to the embodiment is not limited to the embodiment in which composite particles containing magnetic particles are separated using magnetic force.

[0036] 1 to 4 are conceptual diagrams showing an example of a method for separating and recovering metal ions according to an embodiment. Each diagram shows a different stage in the method. Here, Er 3+ , Y 3+ , Ti 4+ , and Mg 2+ This figure shows an example of separating and recovering metal ions from an aqueous solution containing the metal ions. Of course, the separation and recovery method according to the embodiment is not limited to treating an aqueous solution containing metal ions in this combination. In addition, in the illustrated example, EDTA is used as the metal extractant, and various metal ions are separated and recovered in order of increasing stability constant of the metal-EDTA complex shown in Table 1 above. The metal extractant is not limited to EDTA, and depending on the type of metal extractant, the order in which the metal ions are separated and recovered may differ from the illustrated example.

[0037] Figure 1 shows the separation and recovery of Er 3+The aqueous solution to be treated 10 is introduced into the first treatment tank 1 through an inlet 40. The aqueous solution to be treated 10 may be, for example, an original aqueous solution containing various metal ions produced in a process for recovering non-metallic materials as resources from waste. The aqueous solution introduced into the first treatment tank 1 contains Er. 3+ , Y 3+ , Ti 4+ , and Mg 2+ Hereinafter, the aqueous solution to be treated in the first treatment tank 1 will be referred to as a first aqueous solution 21.

[0038] Composite particles 100 containing magnetic particles 101 and a metal extractant 102 are dispersed in a first aqueous solution 21 in the first treatment tank 1. In this example, EDTA is used as the metal extractant 102. As shown in Table 1, the metal ions contained in the first aqueous solution 21 include Er. 3+ Since the metal-EDTA complex has the highest stability, Er in the first aqueous solution 21 3+ preferentially binds to the metal extractant 102 and is selectively adsorbed onto the composite particles 100.

[0039] Using an external magnetic field source 90, Er 3+ The composite particles 100 to which the metal ions (Y) are adsorbed are separated from the first aqueous solution 21. For example, the composite particles 100 are transferred to the second aqueous solution 22 in the second treatment tank 2 using a transfer means equipped with an electromagnet as the external magnetic field source 90. Alternatively, the composite particles 100 are immobilized in the first treatment tank 1 by the external magnetic field source 90, and the remaining unadsorbed metal ions (Y 3+ , Ti 4+ , and Mg 2+ The aqueous solution 11 containing the ions may be discharged from the outlet 50 to the outside of the first treatment tank 1. Note that a magnet having a north pole and a south pole is illustrated to conceptually represent the external magnetic field source 90, but this is a symbolic representation of a device or member capable of generating a magnetic field.

[0040] The first aqueous solution 21 may be adjusted to aid in the dispersion of the first metal ions in the solution for the purpose of separation and recovery, or to promote the formation of complexes between the first metal ions and the metal extractant 102. For example, a pH adjuster 71 may be added to the first aqueous solution 21 through a pH adjuster inlet 70 installed in the first treatment tank 1. Although not shown, the treatment tank may be equipped with a stirrer that stirs the first aqueous solution 21 to promote the dispersion of the composite particles 100 and increase the opportunity for contact between the metal extractant 102 and the first metal ions.

[0041] Er separated from the first aqueous solution 21 3+ The composite particles 100 with the adsorbed Zr are dispersed in a second aqueous solution 22 containing second metal ions. In the illustrated example, Zr is used as the second metal ion. 4+ In the case where the composite particles 100 are separated from the first aqueous solution 21 by fixing the composite particles 100 in the first treatment tank 1 with the external magnetic field source 90 and discharging the aqueous solution 11 out of the first treatment tank 1, for example, instead of transferring the composite particles 100 to the second treatment tank 2, Zr 4+ A second aqueous solution 22 containing the above may be introduced into the first treatment tank 1.

[0042] As shown in Tables 1 and 2, the Zr-EDTA complex has a higher stability constant in water than the Er-EDTA complex. 4+ is the second metal ion, and the first metal ion Er adsorbed on the composite particle is the second metal ion. 3+ The metal ion that forms a metal-EDTA complex with EDTA, which is the metal extractant 102 of the composite particle 100, can be replaced with Er. 3+ From Zr 4+ is replaced by Zr 4+ The composite particles 100 having Er adsorbed thereon are obtained, and the second aqueous solution 22 contains Er. 3+ is eluted.

[0043] Although not shown, the treatment tank may be equipped with a stirrer for stirring the second aqueous solution 22 in order to promote dispersion of the composite particles 100 and increase the chance of a substitution reaction of the first metal ions with the second metal ions.

[0044] Using an external magnetic field source 90, Zr 4+ The composite particles 100 with Er adsorbed thereon are separated from the second aqueous solution 22. For example, the composite particles 100 are transferred to the third aqueous solution 23 in the third treatment tank 3 using a transfer means equipped with an electromagnet as the external magnetic field source 90. Alternatively, the composite particles 100 are fixed in the treatment tank by the external magnetic field source 90, and the Er 3+ The aqueous solution containing the compound may be recovered.

[0045] Zr 4+ From the aqueous solution in which the composite particles 100 adsorbed Er 3+ The Er or Er compound is recovered as a metal element or an Er compound. For example, Er or Er compound is precipitated by adjusting the pH or temperature of the solution or by removing the solvent by evaporation.

[0046] Zr separated from the second aqueous solution 22 4+ The composite particles 100 with Er adsorbed thereon are dispersed in a third aqueous solution 23. In the illustrated example, the composite particles 100 are moved to a third treatment tank 3. The composite particles 100 are fixed in the treatment tank by an external magnetic field source 90, and Er 3+ If the composite particles 100 are separated from the second aqueous solution 22 by recovering the aqueous solution containing the composite particles 100, for example, instead of transferring the composite particles 100 to the third treatment tank 3, the third aqueous solution 23 may be introduced into the treatment tank.

[0047] Zr 4+ For example, a pH adjuster 71 is added to the third aqueous solution 23 in which the composite particles 100 adsorbed with Zr are dispersed through a pH adjuster inlet 70 provided in the third treatment tank 3. By adjusting the pH of the third aqueous solution 23 to a value outside the range in which a Zr-EDTA complex can be formed, Zr 4+ is released from the composite particles 100. Although not shown, the treatment tank may be equipped with a stirrer that stirs the third aqueous solution 23 in order to promote the effect of the added pH adjuster.

[0048] Using an external magnetic field source 90, Zr 4+ The composite particles 100 from which Zr has been released are recovered from the third aqueous solution 23. For example, the composite particles 100 are pulled up from the third aqueous solution 23 using a transport means equipped with an electromagnet as the external magnetic field source 90. Alternatively, the composite particles 100 are fixed in a treatment tank by the external magnetic field source 90, and then the composite particles 100 are removed from the third aqueous solution 23 for reuse as the second aqueous solution 22. 4+ The third aqueous solution 23 containing the composite particles 100 is collected. The collected composite particles 100 can be reused. 4+ The aqueous solution containing, for example, Zr 4+ It can be reused as the second aqueous solution 22 after adjusting the concentration and pH.

[0049] Figure 2 shows the Er 3+ Following the recovery of Y 3+ This indicates the stage where Er is collected. 3+ After separating the composite particles 100 that adsorbed Y, the Y remaining in the first treatment tank 1 3+ , Ti 4+ , and Mg 2+ The aqueous solution containing Y 3+ Separation and recovery of Er 3+ At the recovery stage, Er 3+ In order to separate the composite particles 100 that have adsorbed the compound from the first aqueous solution 21, the composite particles 100 are fixed in the first treatment tank 1 by an external magnetic field source 90, and the aqueous solution 11 that has been discharged from the first treatment tank 1 is reintroduced from the inlet 40.

[0050] The composite particles 100 recovered from the third aqueous solution 23 are dispersed again in the first aqueous solution 21. The metal ions Er contained in the original aqueous solution 10 to be treated are 3+ , Y 3+ , Ti 4+ , and Mg 2+ Among them, Er 3+ followed by Y 3+ The metal-EDTA complex of Y in the first aqueous solution 21 in this step is the most stable. 3+preferentially binds to the metal extractant 102 and is selectively adsorbed onto the composite particles 100.

[0051] Using an external magnetic field source 90, Y 3+ The composite particles 100 to which the metal ions (Ti) are adsorbed are separated from the first aqueous solution 21. For example, the composite particles 100 are transferred to the second aqueous solution 22 in the second treatment tank 2 using a transfer means equipped with an electromagnet as the external magnetic field source 90. Alternatively, the composite particles 100 are immobilized in the first treatment tank 1 by the external magnetic field source 90, and the remaining metal ions (Ti 4+ and Mg 2+ ) may be discharged from the outlet 50 to the outside of the first treatment tank 1.

[0052] Y shown in Figure 2 3+ For details on the recovery stages, see Er 3+ instead of Y 3+ The Er shown in Figure 1 is recovered as a metal or compound. 3+ This is the same as the recovery stage. Since the contents are redundant, the explanation will be omitted.

[0053] In Figure 3, Y 3+ Following the recovery of Ti 4+ Y indicates the stage at which the 3+ Ti remaining in the first treatment tank 1 after separating the composite particles 100 adsorbing Ti 4+ and Mg 2+ The aqueous solution containing Ti was used as the first aqueous solution 21. 4+ Separation and collection of Y 3+ At the collection stage, Y 3+ In order to separate the composite particles 100 that have adsorbed the compound from the first aqueous solution 21, the composite particles 100 are fixed in the first treatment tank 1 by an external magnetic field source 90, and the aqueous solution 12 that has flowed out of the first treatment tank 1 is reintroduced from the inlet 40.

[0054] The composite particles 100 recovered from the third aqueous solution 23 are dispersed again in the first aqueous solution 21. The metal ions Er contained in the original aqueous solution 10 to be treated are 3+ , Y 3+ , Ti 4+ , and Mg 2+Of the Ti remaining at this stage, 4+ and Mg 2+ Between Ti 4+ The stability of the metal-EDTA complex is higher in the first aqueous solution 21. 4+ preferentially binds to the metal extractant 102 and is selectively adsorbed onto the composite particles 100.

[0055] Using an external magnetic field source 90, Ti 4+ The composite particles 100 to which the metal ions (Mg) are adsorbed are separated from the first aqueous solution 21. For example, the composite particles 100 are transferred to the second aqueous solution 22 in the second treatment tank 2 using a transfer means equipped with an electromagnet as the external magnetic field source 90. Alternatively, the composite particles 100 are fixed in the first treatment tank 1 by the external magnetic field source 90, and the remaining metal ions (Mg 2+ ) may be discharged from the outlet 50 to the outside of the first treatment tank 1.

[0056] Ti shown in Figure 3 4+ For details on the recovery stages, see Y 3+ Instead of Ti 4+ The Er shown in Figure 1 is recovered as a compound such as titanium dioxide (TiO2). 3+ Recovery and Y shown in Figure 2 3+ This is the same as the recovery stage. Since the contents are redundant, the explanation will be omitted.

[0057] Figure 4 shows the Ti 4+ Following the recovery of Mg 2+ This shows the stage where Ti is collected. 4+ After separating the composite particles 100 adsorbing Mg, the Mg remaining in the first treatment tank 1 2+ The aqueous solution containing Mg was used as the first aqueous solution 21. 2+ Separation and recovery of Ti 4+ At the recovery stage, Ti 4+ In order to separate the composite particles 100 that have adsorbed the compound from the first aqueous solution 21, the composite particles 100 are fixed in the first treatment tank 1 by an external magnetic field source 90, and the aqueous solution 12 that has flowed out of the first treatment tank 1 is reintroduced from the inlet 40.

[0058] At this stage, the metal ions remaining in the first aqueous solution 21 are Mg 2+ Therefore, even if it is not adsorbed onto the composite particle 100, Mg 2+ For example, the appropriate counter anion X can be recovered. - The magnesium compound MgX is obtained by adding a source to the solution, adjusting the pH or temperature of the solution, or removing the solvent by evaporation. n is precipitated.

[0059] Although no example is shown, Mg 2+ was adsorbed onto the composite particles, replaced with a second metal ion, and then the Mg desorbed from the composite particles was 2+ Mg may be recovered. 2+ The second aqueous solution after desorbing from the composite particles may contain fewer impurities than the first aqueous solution after recovering metal ions other than the metal ions. Therefore, recovering the last type of metal ion in the initial aqueous solution to be treated through composite particles can result in a more highly pure recovered product. For the same reason, even if the initial aqueous solution (aqueous solution to be treated 10) contains only one type of metal ion, recovering through composite particles can easily result in a highly pure recovered product.

[0060] An example of how a metal extractant is immobilized on the particle surface of a composite particle will be described with reference to FIGS.

[0061] The composite particle shown in Figure 5 is an example in which a metal extractant is immobilized by chemical adsorption. Composite particle 100 includes a base particle that includes magnetic particles 101 and an acid-resistant layer 103 that covers the surface of the magnetic particles. Metal extractant 102 is immobilized on the surface of acid-resistant layer 103 by chemical adsorption, and thus metal extractant 102 is immobilized on the surface of the base particle.

[0062] The composite particle shown in Figure 6 is an example in which a metal extractant is immobilized by physical adsorption. Composite particle 100 includes magnetic particles 101 and an acid-resistant layer 103 that covers the surface of the magnetic particles. Acid-resistant layer 103 contains metal extractant 102. Acid-resistant layer 103 containing metal extractant 102 is formed on the surface of magnetic particle 101, thereby immobilizing metal extractant 102 on the surface of magnetic particle 101.

[0063] According to one or more of the embodiments described above, a method for separating and recovering metal ions from an aqueous solution containing metal ions is provided. The method includes dispersing composite particles in an aqueous solution containing one or more first metal ions, selectively adsorbing the first metal ions onto the composite particles, separating the composite particles with the first metal ions adsorbed from the aqueous solution, and then replacing the first metal ions adsorbed onto the composite particles with second metal ions, which are then released from the composite particles and recovered. The composite particles include base particles and a metal extractant. The separation and recovery method described above allows metal ions to be easily and selectively separated and recovered even from an aqueous solution containing a mixture of multiple types of metal ions.

[0064] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0065] 1...first treatment tank, 2...second treatment tank, 3...third treatment tank, 10...aqueous solution to be treated, 11, 12, 13...aqueous solution, 21...first aqueous solution, 22...second aqueous solution, 23...third aqueous solution, 40...inlet, 50...outlet, 70...pH adjuster inlet, 71...pH adjuster, 90...external magnetic field source, 100...composite particles, 101...magnetic particles, 102...metal extractant, 103...acid-resistant layer.

Claims

1. Dispersing composite particles comprising substrate particles and a metal extractant in an aqueous solution comprising one or more first metal ions; Selectively adsorbing the first metal ions onto the composite particles; separating the composite particles having the first metal ions adsorbed thereon from the aqueous solution; replacing the first metal ions adsorbed on the composite particles with second metal ions, and then desorbing and recovering the second metal ions from the composite particles; A method for separating and recovering metal ions, comprising:

2. a metal ion having the highest stability constant of a metal complex with the metal extractant in the aqueous solution is selectively adsorbed onto the composite particles as the first metal ion; 2. The method for separating and recovering metal ions according to claim 1, wherein the stability constant of the second metal ions is higher than that of the first metal ions adsorbed on the composite particles.

3. the aqueous solution contains two or more types of the first metal ions, desorbing the second metal ions from the composite particles; re-dispersing the composite particles from which the second metal ions have been released in the aqueous solution; further comprising 3. The method for separating and recovering metal ions according to claim 2, wherein the metal ions having the highest stability constant in the aqueous solution are selectively adsorbed onto the composite particles as the first metal ions, the first metal ions adsorbed onto the composite particles are replaced with the second metal ions, and the first metal ions are then detached from the composite particles and recovered, the second metal ions are detached from the composite particles, and the composite particles are re-dispersed in the aqueous solution, thereby selectively adsorbing and separating the first metal ions in descending order of their stability constant.

4. The method for separating and recovering metal ions according to claim 1 , wherein the composite particles have an acid-resistant layer on the surface of the base particle.

5. 4. The method for separating and recovering metal ions according to claim 1, wherein the metal extractant is immobilized on the surface of the composite particles by physical adsorption or chemical adsorption.

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