JP2004217984A - Method for separating and recovering metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dissolve such problem that the conventional adsorbent is not always excellent in absorbency, labor and facility for fitting/removing treatment, the cost needed to the absorbent and the productivity of recovery. <P>SOLUTION: A method for separating a metal is provided with at least one or more kinds of functional material group disposed in a flowing passage range in contact with metal ion mixing solution, at least one or more of pouring holes for pouring the mixing solution into this range in a column and at least one or more of discharge holes for discharging the mixing solution from the range in the column. Then, the functional material is constituted of an organic material and further, this material has an inner hollow part and the metal to be removed into the inner hollow part, is included or formed with a combined material so as to separate the metal from the solution. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a separating agent for continuously and selectively or non-selectively separating metal ions from an aqueous solution in which various metal ions are present, and a method for treating an aqueous solution containing metal ions. Specifically, a metal separating agent having a lumen and containing a functional molecule capable of encapsulating a metal in the lumen, or separating a metal ion from an aqueous solution containing various metal ions using the metal separating agent. The present invention relates to a method for removing metal ions from an aqueous solution in which various metal ions are present using the same and a method for removing the same.
[0002]
[Prior art]
Techniques for separating these metals from aqueous solutions containing noble metals such as silver and gold and harmful heavy metals such as copper, lead, mercury, and cadmium are extremely important from the viewpoint of resource recovery and reuse and prevention of environmental pollution. Heretofore, as a method for separating these metals, a metal-containing aqueous solution has been used as a cation exchange resin, activated carbon, a metal chelating agent, synthetic zeolite, silica gel, activated alumina, activated clay, an ion transport agent through a liquid membrane, phytoplankton. The method of contacting with various inorganic or organic adsorbents and adsorbing and adsorbing metals on these adsorbents has become mainstream.
[0003]
Specific examples of substances used as ion transport agents include troponoid-added dithiocrown ethers that trap only mercury. Further, a cyclic polyether dicarboxylic acid has been known as a substance capturing only lead. In addition, a methionine derivative having an 8-quinolyl group is described as a compound that traps only mercury. Further, Patent Document 1 discloses an α-amino acid diazide derivative as a substance selectively capturing only copper. So, there is no end to the list.
[0004]
On the other hand, it is known that some microorganisms and algae have an ability to accumulate a specific metal, and in recent years, this has been used to remove harmful metals and valuable metals in wastewater, Attempts have been made to recover, for example, methods using plant biomass, mold, and microalgae such as chlorella have been proposed.
[0005]
[Patent Document 1]
JP-A-5-163243
[Problems to be solved by the invention]
However, the above-mentioned inorganic and organic adsorbents have a limit in adsorption capacity. For example, a metal chelate resin is composed of a chelate functional group that is supplemented by forming a complex with a metal ion using its molecular structure, and a carrier resin that fixes the chelate functional group. If a resin having a large amount of the chelate functional group introduced is selected, the capture yield is improved, but the yield is limited because basically one metal complex is captured for one chelate functional group. Therefore, there is a problem that a large amount of adsorbent must be used to treat a large amount of waste liquid. In addition, while the adsorbing material has a very high selectivity for the specific metal, it is not always easy to desorb the metal once adsorbed, so the regeneration of the adsorbent is difficult and requires complicated operations. Also have. The cost of regenerating the adsorbent and the productivity of recovery are not always good. Moreover, the microorganisms and algae used so far are not always satisfactory in terms of the yield of heavy metals and the difficulty of granulation.
[0007]
[Means for Solving the Problems]
The present inventors have found that ferritin present in the elephant and liver of animals such as horses and cattle regulates metal ion concentration in the body by encapsulating metal ions in a lumen covered by a protein shell. are doing. In addition, when reducing metal ions containing ferritin to metal, we focused on the fact that several thousand metal atoms are contained in one ferritin. It has been found that by effectively utilizing a functional molecule capable of encapsulating a metal in its lumen, not only the initial object can be achieved, but also the yield can be significantly improved. The present invention has been completed by further research based on such findings.
[0008]
A method for separating a metal according to the present invention that solves the above problems,
A method for selectively or non-selectively separating metals from a first solution in which at least one or more metal ions are mixed,
In the first solution, contacting at least one or more functional substance group,
The step of separating the functional substance group from the first solution by means of aggregating or precipitating the functional substance group,
The above steps are repeated at least once, and the number of times is equal to or less than the number of types of the functional substance group,
The functional substance is composed of an organic substance, and further, the substance has a lumen, and
It is characterized in that the metal is separated from the first solution by enclosing the metal to be removed in the cavity or forming a complex with the metal at the time of contact with the first solution.
[0009]
Preferably, the means for aggregating the functional substance group is to realize separation of the functional substance group and the first solution by centrifugal force.
[0010]
The means for precipitating the functional substance group is to put a compound having an action of precipitating the functional substance group in the first solution, and the precipitating compound is any one of ammonium chloride, cadmium, and divalent ions. It is preferable that it is above.
[0011]
Another method for separating a metal according to the present invention that solves the above-mentioned problem is
A method for selectively or non-selectively recovering a metal from a first solution in which at least one or more metal ions are mixed,
In the first solution, contacting at least one or more functional substance group,
Separating the functional substance group from the first solution by the first operation, or transferring the functional substance group to a second solution that does not directly contact the first solution;
A step of recovering the metal from the functional substance group by the second operation,
The above steps are repeated at least once, and the number of times is equal to or less than the number of types of the functional substance group,
The functional substance is composed of an organic substance, and further, the substance has a lumen, and
The metal is recovered from the first solution by enclosing the metal to be removed in the inner cavity or forming a complex with the metal at the time of contact with the first solution.
[0012]
The first operation is an operation according to any one of claims 1 to 3,
Further, the second operation may be to realize the recovery of the metal by heating the separated functional substance group at a temperature equal to or higher than the burning temperature of the functional substance in a nitrogen atmosphere or the atmosphere. preferable.
[0013]
The first operation is an operation according to any one of claims 1 to 3,
The second operation is to put in a compound having an action of selectively decomposing only the functional substance group, and the degrading compound is one or more of a protease, urea, and a surfactant. Is preferred.
[0014]
The first operation is an operation according to any one of claims 1 to 3,
Preferably, the proteolytic enzyme is any one or more of protease, dispase, trypsin, nagarase.
[0015]
The functional substance is preferably (particles having a diameter of 3 to 30 nm).
[0016]
It is preferable that a major part of the organic substance constituting the functional substance is a protein.
[0017]
It is preferred that the protein molecule is a ferritin family.
[0018]
It is preferable that the huerytin phamily is huerytin or apopheuritin, and a modified product obtained by modifying these amino acid sequences.
[0019]
It is preferred that the protein molecule is a virus selected from the group of adenovirus, rotavirus, poliovirus, HK97, CCMV, and modifications thereof.
[0020]
It is preferable that the protein molecule is a DpsA protein or a MrgA protein, and a modified product obtained by modifying these amino acid sequences.
[0021]
The metal is iron, iron oxide, other iron compounds, nickel, nickel oxide, other nickel compounds, cobalt, cobalt oxide, other cobalt compounds, copper, copper oxide, other copper compounds, gold, other It is preferably at least one of a gold compound, platinum and another platinum compound.
[0022]
The metal is iron, iron oxide, other iron compounds, nickel, nickel oxide, other nickel compounds, cobalt, cobalt oxide, other cobalt compounds, copper, copper oxide, other copper compounds, gold, other It is preferably at least one of a gold compound, platinum and another platinum compound.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a functional molecule having a metal-separating ability and a method of separating and recovering a metal using the same according to the present invention will be described with reference to the drawings.
[0024]
(First Embodiment) [Container Individual Collection Centrifugation]
FIG. 1 is a conceptual diagram showing an outline of an example of a method for separating and recovering a metal from a solution containing metal ions according to the present invention.
[0025]
As an example, a method of separating only metal ions 7C from an aqueous solution containing metal ions 7A, 7B, and 7C will be described. The container of FIG. 1 is filled with the solution 2 containing the one kind of metal ion. The functional material 6C is injected into the container, and the metal ion 7C is included in the functional material 6C by using the operation specifically described in the embodiment, to form the complex 8C. Thereafter, only the composite 8C containing the metal 7C is separated from the container by aggregating or precipitating the composite 8C. By this operation, the metal ions 7C can be separated from the solution 2. That is, the solution 12 from which the metal ions 7C have been removed is formed.
[0026]
Centrifugation is desirable as such an aggregation / precipitation method. The centrifugation method used here means a precipitation method using all centrifugal forces including a sucrose gradient method and an ultracentrifugation method.
[0027]
In such a functional molecule 6, a main part of an organic substance constituting the structure is a protein. The functional molecule 6 is desirably a particle having a diameter of 3 to 30 nm. Specifically, as the protein molecule used as the functional molecule 6, apoferritin or the like can be preferably used. As shown schematically in FIG. 3, apoferritin can be a metal-protein complex in which a core 1 of an inorganic material atom is held in a lumen and the periphery thereof is covered with a protein shell 2. Ferritin, which is a family of apoferritin and can contain iron ions therein, can be extracted from organs such as spleen and liver of animals such as horses and cattle.
[0028]
In the case of ferritin, the inorganic material atoms of the core 1 are usually iron oxide (Fe2 ↓ O3 ↓), the diameter of the core 1 is about 6 nm, the total number of iron oxides is about 3000, and the shell 2 has a molecular weight of 20,000. About 24 mer of protein, the outer diameter of the entire 24 mer is about 12 nm.
[0029]
Further, the functional molecule 6 may be a modified product obtained by modifying the amino acid sequence of these proteins. The means for modifying the protein is realized using a technique known to those skilled in the art such as a genetic recombination technique. For example, glutamic acid and aspartic acid located at the metal introduction part of apoferritin are replaced by uncharged and small-sized serine. Next, glutamic acid located in the lumen is replaced with a basic amino acid such as lysine or a neutral amino acid. Furthermore, by introducing one or more cysteine bonds into the lumen, it is possible to prevent a repulsive force due to an electrostatic interaction generated between a negatively charged (AuCl ₄ ) ⁻ and a negatively charged amino acid, (AuCl ₄ ) ⁻ is easily taken into the lumen. It was incorporated into the lumen (AuCl ₄₎ ^- may be reduced to Au by a technique known to those skilled in the art. Therefore, if this modified apoferritin is used as the functional molecule 6, a column for separating gold ions in a solution as gold particles can be produced.
[0030]
Other examples include the DpsA protein or MrgA protein. In the case of the Dps protein, although not shown, the diameter of the core 1 is about 4 nm, the shell 2 is a tetrahedral dodecamer, and the outer diameter of the entire dodecamer is about 9 nm. Further, a virus selected from the group of adenovirus, rotavirus, poliovirus, HK97, CCMV and the like can also be suitably used.
[0031]
FIG. 1 shows a method of performing the following operation and separating only the metal ion C from the solution, and then recovering only the metal ion (symbol C).
[0032]
The resulting precipitate 18C is heated and burned off in a nitrogen atmosphere or in the air at a temperature equal to or higher than the burning temperature of the functional substance 6 and preferably above the burning temperature of the protein using the heating source 15. Thereby, recovery of the metal 7C can be realized. Alternatively, the complex decomposition solution 14 may be added to the precipitate to decompose the complex 18C and recover the metal 7C.
[0033]
When the complex 18 is a protein, for example, a proteolytic enzyme, urea, a surfactant or the like is suitably used as the complex decomposition solution 14.
[0034]
Specifically, proteases, dispase, trypsin, and nagarase are used as proteolytic enzymes by a treatment method known to those skilled in the art.
[0035]
When the compound included in the core of the complex 18 is a metal compound, the method also includes a process of oxidizing and reducing the metal compound by a method known to those skilled in the art.
[0036]
(Embodiment 2) [Container individual collection centrifugation]
FIG. 2 is a conceptual diagram schematically showing an example of a method for selectively or nonselectively recovering a metal from a solution in which various kinds of metal ions are mixed according to the present invention.
[0037]
As an example, a method of recovering only metal 7C from three kinds of metals (7A, 7B, 7C) will be described. The container of FIG. 2 is filled with a solution containing the above three types of metal ions. The functional substance 6C is injected into the container, and the metal ion C is included in the functional substance 6C by using an operation specifically described in the embodiment, to form the complex 8C. Thereafter, only the composite 8C containing the metal 7C is separated from the container by aggregating or precipitating the composite 8C. Here, a solution containing only the functional material 6C was injected into the container in order to selectively recover only the metal 6C, but a solution containing at least one or more functional materials was used in order to non-selectively recover the metal. May be injected.
[0038]
Centrifugation is desirable as such an aggregation / precipitation method. The precipitate 8 is heated and burned off in a nitrogen atmosphere or in the air at a temperature equal to or higher than the burning temperature of the functional substance 6, preferably at or higher than the burning temperature of the protein, by using the heating source 15. It is desirable to realize the recovery of the metal 7A. Further, the complex decomposition solution 14 described in Embodiment 2 may be added to the precipitate to decompose the complex 18C and recover the metal 7C.
[0039]
Since the supernatant contains the remaining metal ions A and B, only the metal 7A and the metal 7B can be recovered by the same procedure as described above. That is, a solution containing the functional substance 6A for selectively enclosing only gold A in the supernatant is injected into the supernatant, and the centrifugation operation is repeated. By repeating the steps described above at least once and not more than the number of types of the functional substance group, the metal can be selectively recovered.
[0040]
(Embodiment 3) [Container individual collection sedimentation]
FIG. 2 is also a conceptual diagram schematically showing an example of a method for selectively or nonselectively recovering a metal from a solution containing metal ions according to the present invention.
[0041]
As an example, a method of recovering only metal 7C from three kinds of metals (7A, 7B, 7C) will be described. The container of FIG. 2 is filled with a solution containing the above three types of metal ions. As in the second embodiment, only the complex 8C containing the metal 7C is separated from the container by precipitating the complex 8C. However, even if such precipitation / agglomeration is realized using a chemical reaction. good.
[0042]
For example, when the functional substance 6 is the protein described in Embodiment 1, the protein can be precipitated using an ammonium chloride solution or urea. Other methods of precipitation include coprecipitation with divalent ions and chemical aggregation. When the functional substance 6 is ferritin described in Embodiment 1, the ferritin can be precipitated with divalent ions such as Ca ²⁺ or cadmium ions. For example, ferritin can be added by adding 10 mM CdSO ₄ or the like to a container. Precipitates.
[0043]
The precipitate is heated in a nitrogen atmosphere or in the air using the heating source 15 specified in the second embodiment at a temperature equal to or higher than the burning temperature of the functional substance 6, preferably equal to or higher than the burning temperature of the protein. It is desirable to realize the recovery of the metal 7A by heating and burning off 8. Further, the complex decomposition solution 14 described in Embodiment 2 may be added to the precipitate to decompose the complex 18C and recover the metal 7C.
[0044]
Since the supernatant contains the remaining metal ions A and B, only the metal 7A and the metal 7B can be recovered by the same procedure as described above. That is, a solution containing the functional substance 6A for selectively enclosing only gold A in the supernatant is injected into the supernatant, and the precipitation operation is repeated.
[0045]
【Example】
(Example 1)
Hereinafter, an example in which iron ions are removed and recovered from an aqueous solution by being encapsulated in ferritin, which is a functional substance, by the method of the present invention will be described.
[0046]
As an example, an example is described in which apoferritin is used as a functional substance, precipitated with CdSO ₄ , centrifuged, and iron is recovered from an aqueous solution.
(Purification of apoferritin)
From horse spleen ferritin (Sigma), only the 24 mer is purified. Specifically, dialysis is performed at 4 ° C. overnight using 0.5 mM EDTA and 10 mM Tris (pH 8.5). Thereafter, using a G4000SWXL PEEK column (TOSOH) sufficiently equilibrated with 10 mM TrisHCl (pH 8.5) and 150 mM NaCl, only the 24 mer was fractionated. Ferritin was further dialyzed against 1 wt% thioglycolic acid and 0.1 M acetate buffer (pH 5.6) at 4 ° C. for 3 hours, and further dialyzed at 4 ° C. using 0.1 M acetate buffer (pH 5.6). After dialysis for 4 hours and apoferritinization, dialysis is performed with 50 mM TrisHCl (pH 8.5). Finally, it was dissolved in 150 mM NaCl buffer.
(Incorporation and collection of iron ions)
A solution in which apoferritin was dissolved to a final concentration of 0.1 μM was added to a 100 μM iron sulfate solution. After adding dilute sulfuric acid to adjust the pH to 1.5 and reacting at room temperature for 60 minutes, 10 mM CdSO ₄ is added and centrifuged at low speed. Ferritin is included in the precipitate.
[0047]
The amount of residual iron in the waste liquid was measured for the supernatant by flame atomic absorption spectrometry. Hydrochloric acid was added to the discharged solution to make a hydrochloric acid solution having a final concentration of 0.1 M, which was directly sprayed on an acetylene / air frame, and iron was quantified by an absorbance at a wavelength of 248.3 nm. The measured effluent contained only 1.3 μg of iron.
[0048]
In order to remove Cd from the precipitate obtained by centrifugation, the precipitate is dissolved in 150 mM NaCl and subjected to high-speed centrifugation three times. The precipitate was allowed to stand on a 30 mm square Si substrate, and heated at 700 ° C. for 1 hour in a quartz tube furnace in which nitrogen gas was flowed at a flow rate of 200 mL / min. After that, when the inside of the furnace was cooled to 100 ° C. or lower, it was taken out from the substrate, and 3.5 mg of a metal lump was obtained. Converted from the concentration of the added apoferritin, the recovery capacity of ferritin per unit mass was calculated to be 352 mg / g, and apoferritin showed a very large adsorption capacity.
[0049]
【The invention's effect】
The functional molecule of the present invention can include a large amount of metal ions. Moreover, the metal can be easily desorbed and recovered by a simple operation.
[0050]
Therefore, this patent can efficiently absorb, collect or remove valuable and harmful metals in industrial waste, mine drainage, factory drainage, etc., which can be used to recover and reuse resources and prevent environmental pollution. It is extremely important from the viewpoint of.
[0051]
In addition, since the main component of the functional molecule is a biomolecule represented by a protein, it can be applied to medical fields such as blood treatment and food fields.
[0052]
In addition, since the present method has a very high functional molecule single yield, it can be applied to the preparation of concentrated samples for analyzing ultratrace metals.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a method for separating and recovering a metal utilizing an agglomeration / precipitation action according to an embodiment of the present invention. FIG. 2 is a view showing an aggregation / precipitation action according to an embodiment of the present invention. FIG. 3 is a diagram showing an outline of a method for separating and recovering a metal used. FIG. 3 is a diagram showing a molecular structure of a ferritin protein which is a functional molecule of the present invention.
1: Core of Fe ₂ O ₃ 2: Protein shell 3: Metal ion-containing solution 4: Functional molecule-containing solution 5: Metal ion-removed solution 6: Functional molecule 6A: Functional molecule A
6B: Functional molecule B
6C: Functional molecule C
7: Metal ion 7A: Metal ion A
7B: Metal ion B
7C: Metal ion C
8: Metal-functional molecule complex 8A: Metal-functional molecule complex A
8B: metal-functional molecule complex B
8C: metal-functional molecule complex C
10: container 14: complex decomposition solution 15: heating source 18C: aggregated complex C
19: Decomposed metal-functional molecule complex

Claims (15)

A method for selectively or non-selectively separating metals from a first solution in which at least one or more metal ions are mixed,
In the first solution, a step of contacting at least one or more functional substance group,
A step of separating the functional substance group from the first solution by means of aggregating or precipitating the functional substance group,
The above steps are repeated at least once, and the number of times is equal to or less than the number of types of the functional substance group,
The functional substance is composed of an organic substance, and further, the substance has a lumen, and
A metal which comprises separating the metal from the first solution by enclosing the metal to be removed in the lumen or forming a complex with the metal at the time of contact with the first solution. How to separate. The method for separating metals according to claim 1, wherein the means for aggregating the functional substance group is to realize separation of the functional substance group and the first solution by centrifugal force. The means for precipitating the functional substance group is to put a compound having an action of precipitating the functional substance group in the first solution, and the precipitating compound is ammonium chloride, cadmium, or any of divalent ions. The method for separating metals according to claim 1, wherein the method is one or more. A method for selectively or non-selectively recovering a metal from a first solution in which at least one or more metal ions are mixed,
In the first solution, a step of contacting at least one or more functional substance group,
Separating the functional substance group from the first solution by the first operation, or moving the functional substance group to a second solution that is not in direct contact with the first solution,
Collecting a metal from the functional substance group by a second operation,
The above steps are repeated at least once, and the number of times is equal to or less than the number of types of the functional substance group,
The functional substance is composed of an organic substance, and further, the substance has a lumen, and
A metal, comprising: in contact with the first solution, containing the metal to be removed in the lumen, or forming a complex with the metal, thereby recovering the metal from the first solution. How to collect. The first operation is an operation according to any one of claims 1 to 3,
Further, the second operation is to realize the recovery of the metal by heating the separated functional material group at a temperature equal to or higher than the burning temperature of the functional material in a nitrogen atmosphere or in the air. The method for recovering a metal according to claim 4. The first operation is an operation according to any one of claims 1 to 3,
The second operation is to put a compound having an action of selectively decomposing only the functional substance group, and the degrading compound is any one of a protease, urea, and a surfactant. The method for recovering a metal according to claim 4, which is as described above. The first operation is an operation according to any one of claims 1 to 3,
The method for recovering a metal according to claim 6, wherein the protease is any one or more of protease, dispase, trypsin, and nagarase. The method according to any one of claims 1 to 7, wherein the functional substance is (particles having a diameter of 3 to 30 nm). The method according to any one of claims 1 to 8, wherein a main part of the organic substance constituting the functional substance is a protein. 10. The method according to claim 9, wherein the protein molecule is huerytin familly. The method according to claim 10, wherein the huerytin familly is huerytin, apopheuritin, or a modified product obtained by modifying the amino acid sequence thereof. The method according to claim 9, wherein the protein molecule is a virus selected from the group consisting of adenovirus, rotavirus, poliovirus, HK97, CCMV, and modifications thereof. The method according to claim 9, wherein the protein molecule is a DpsA protein or a MrgA protein, or a modified product obtained by modifying the amino acid sequence thereof. The metal is iron, iron oxide, other iron compounds, nickel, nickel oxide, other nickel compounds, cobalt, cobalt oxide, other cobalt compounds, copper, copper oxide, other copper compounds, gold, other The method according to any one of claims 1 to 13, wherein the method is at least one of gold compounds, platinum, and other platinum compounds. The metal is iron, iron oxide, other iron compounds, nickel, nickel oxide, other nickel compounds, cobalt, cobalt oxide, other cobalt compounds, copper, copper oxide, other copper compounds, gold, other The method according to any one of claims 1 to 13, wherein the method is at least one of gold compounds, platinum, and other platinum compounds.

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