JP4119966B2 - Elution recovery of metal from metal collector and method of regenerating eluent - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention collects useful metals from seawater, or collects and removes harmful heavy metals from river water and wastewater, and collects useful metals and harmful substances with as little waste as possible. The present invention relates to a method for efficiently separating and recovering metal.
[0002]
[Prior art]
Seawater contains many useful metals such as uranium, titanium, cobalt, and vanadium. Japan relies on imports for almost 100% of these metals, so if these metals can be collected from seawater, not only can we achieve the long-cherished desire for self-sufficiency of energy, but also overseas for useful rare metals. The degree of dependence can be reduced, and further, it can contribute to the protection of the global environment.
[0003]
Attempts to collect useful metals in seawater were made in the United Kingdom around 1960 and in Japan since the early 1970s. The attempted method uses a collection material mainly composed of titanic acid, and the collection capacity and collection speed are small, and the durability of the collection material is not sufficient. Therefore, economic evaluation preceded, and the collection technology of useful metals in seawater has never been developed from the viewpoint of protecting the global environment, saving resources and energy, and securing long-term energy sources. For example, with respect to a technique of collecting seawater by flowing it into a collection device by a column distribution system and recovering uranium, there is a problem that the pump power occupies most of the energy of the recovered uranium.
[0004]
In the first half of the 1970s, it was found that amidoxime groups are effective in collecting useful metals including uranium. Also, in the first half of the 1980s, development of functional materials by radiation graft polymerization became active, and a trapping material in which an amidoxime group was introduced into the graft side chain of an existing polyolefin fiber was proposed, which further improved performance. .
[0005]
With the advancement of technology and the social background that seeks to protect the global environment and save resources and energy, the need to develop technology to collect and recover useful metals in seawater again in the 1990s is called out. Became.
[0006]
[Problems to be solved by the invention]
In order to efficiently collect and recover useful metals from seawater, the development of excellent metal collectors is also important. It is also important to develop a method for elution recovery. For example, even if the metal is eluted from the collecting material, if the metal is discarded without being effectively recovered, the collected metal cannot be used effectively. In addition, the metal collecting material can be used for the purpose of collecting and removing harmful heavy metals from river water or factory wastewater, for example. A method is conceivable in which the metal is eluted and recovered to collect and process the metal alone and to make the collection material reusable. In this method, when a part of the metal is recovered without being recovered, it may cause problems such as environmental pollution.
[0007]
In view of the importance of such a problem, the present inventors elute the collected metal from the metal collecting material that has adsorbed and collected the metal with as little waste as possible and without consuming energy. We have conducted intensive research to find out how to recover.
[0008]
There has been no method for efficiently eluting the collected metal from the adsorbed metal collecting material while minimizing the generation of waste. In order to achieve this, it is necessary to develop a collection material with good performance, an efficient elution method of the target metal, and reuse of the eluent.
[0009]
A method of performing elution stepwise while increasing the concentration of the eluent sequentially has been conventionally performed in the field of ion exchange. For example, when ion exchange is performed on raw water rich in calcium ions and regeneration is performed with sulfuric acid, gypsum (CaSO_FourIn order to suppress the production of), there is a method in which the concentration of sulfuric acid is first reduced and then increased stepwise, and is regenerated in several stages, which is called the Stepwise regeneration method. However, this is intended to remove the cause of clogging and enable normal regeneration to be carried out, and was not intended to actively separate and recover the adsorbed substances.
[0010]
In order to achieve efficient elution recovery, not only the usage of the eluent but also the elution characteristics of the collection material have an important influence. Since conventional ion exchange resins have a three-dimensional network structure in which the skeleton of styrene is crosslinked with divinylbenzene, the polymer chain is rigid and ion exchange groups such as sulfone groups and quaternary ammonium groups are present. Since it is introduced into a rigid polymer chain, the adsorption rate and diffusion rate of ions are low. Therefore, since the diffusion rate of the regenerant to the adsorbed ion exchange resin is low, not only the regeneration efficiency is low, but also the adsorbed ions, for example, divalent metal ions such as calcium ions and monovalent metals such as sodium ions. The separation efficiency with ions is also small. Such a problem applies not only to the field of ion exchange, but also to the adsorption and elution of metals to which the present invention relates.
[0011]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is a first step in which an eluent having a low concentration is brought into contact with a metal collecting material that has adsorbed metal; an eluent having a higher concentration than that in the first step is brought into contact with the metal collecting material, A second step of recovering the metal in the eluent; a third step of regenerating the used eluent obtained in the second step and further concentrating the recovered target metal at the same time; The present invention relates to a method for eluting and recovering metal from a metal collecting material, wherein the regenerated eluent is reused as an eluent in the first step.
[0012]
  Hereinafter, a chelating resin mainly containing an amidoxime group is used as a metal collecting material, and from seawater.Such as uraniumThe method according to the present invention will be described by taking, as an example, a method for eluting and recovering an adsorbed and collected useful metal from a metal collecting material used for adsorbing and collecting a useful metal. In addition, the method illustrated below of recovering uranium and the like from a collection material obtained by adsorbing and collecting uranium and the like from seawater is an example of a method to which the present invention can be applied.It is.
[0013]
  In the method according to one embodiment of the present invention, a chelate resin mainly composed of an amidoxime group is immersed in seawater for several tens of days,Uranium etc.First, the used metal collector that adsorbsThruContact with 0.1N hydrochloric acid. With such a thin hydrochloric acid,Uranium isWithout elution, magnesium, calcium, etc. elute first. Next, as a second step, the trapping material is brought into contact with an eluent having a higher concentration than the first eluent. For example, when contacted with 0.5 N hydrochloric acid, 90% or more of uranium adsorbed on the collecting material is eluted. Since the concentration of uranium in the eluent is on the order of several tens of ppm, the concentration of 3 ppb in seawater can be concentrated 10,000 times. In addition, the eluent of the second step has few impurities such as magnesium and calcium, and the purification is performed together.
[0014]
  The type of eluent is appropriately selected depending on the type of metal to be collected, the method for purifying the collected metal, easiness of elution, type of functional group, durability, and the like. For example,UraniumIn the case of a metal for recovery purposes, hydrochloric acid is preferably used as the eluent. Moreover, when harmful heavy metals such as nickel and copper are collected by a collecting material having a functional group called iminodiacetic acid group, hydrochloric acid, sulfuric acid and the like are preferably used as an eluent. The concentration to be used as the eluent is such that the target metal does not elute in the first eluent, but the concentration in which the other metals elute, and the target in the second eluent. The concentration is such that the metal to be eluted. This varies depending on the type of eluent used, the type of metal to be recovered, the type of metal not to be recovered that should be removed in the first elution step, the state of contamination deposition in the environment of use, etc. , Determined empirically. For example, when the target metal is uranium and hydrochloric acid is used as the eluent, the preferred concentration of hydrochloric acid in the first eluent is 0.01 to 0.1 N, and the preferred concentration of hydrochloric acid in the second eluent is 0. .2 to 1 regulations.
[0015]
Next, a third step of regenerating the uranium-containing eluent in the second step and concentrating uranium at the same time is performed. That is, in the third step, the uranium-containing eluent in the second step is separated to generate a regenerated eluent from which uranium has been removed and a concentrated eluent in which uranium is concentrated.
[0016]
Thus, as a method of producing | generating the liquid which removed the metal ion from the metal ion containing liquid, and a metal ion concentrate, the method of performing by electrodialysis is mentioned, for example. The electrodialysis method consists mainly of a DC electric field and an ion exchange membrane. It is used to concentrate seawater for salt production or to desalinate high salt water for beverage use. It's being used. The eluent comes into contact with the metal trapping material and is partially consumed, or the concentration decreases as the liquid volume increases. For example, when hydrochloric acid is used as the eluent, calcium and magnesium are simultaneously eluted in addition to uranium adsorbed on the metal scavenger. The electrodialysis method is optimal for removing these dissolved metal ions and increasing the hydrochloric acid concentration.
[0017]
The basic principle of electrodialysis is shown in FIG.
FIG. 1 shows an electrodialysis tank 1 in which an anion exchange membrane 4 and a cation exchange membrane 5 are arranged in this order between a positive electrode 2 and a negative electrode 3. A portion 6 sandwiched between both ion exchange membranes forms a desalting chamber. As an example, uranyl ion UO₂ ²⁺A method for treating an eluent composed of hydrochloric acid containing selenium in this electrodialysis tank will be described. A hydrochloric acid eluent 7 containing uranyl ions is introduced into the desalting chamber 6 while a direct current flows through the electrodes 2 and 3. As the liquid introduced into the acid concentrating chamber 11, a liquid similar to the first eluent or the second eluent (for example, a hydrochloric acid solution having an equivalent concentration or the eluent itself) can be used. Moreover, as the introduction liquid into the metal ion concentration chamber 12, an eluent liquid containing uranyl ions can be used. For example, as the introduction liquid into the metal ion concentration chamber 12, the hydrochloric acid eluent 7 containing the same uranyl ion as that introduced into the desalting chamber can be passed, or the uranyl ion obtained in the previous process can be passed. The concentration can be further increased by introducing a concentrated solution. When energized, uranyl ion UO₂ ²⁺Is drawn by the negative electrode and moves through the cation exchange membrane 5 and enters the metal ion concentration chamber 12. As a result, from the metal ion concentration chamber 12, a concentrated liquid 9 in which uranyl ions are concentrated is obtained. On the other hand, the chloride ion of hydrochloric acid Cl^-Move by being attracted by the positive electrode and enter the acid concentrating chamber 11 through the anion exchange membrane 4. As a result, a hydrochloric acid (HCl) solution containing no metal ions is obtained from the acid concentration chamber 11. Metal ions cannot pass through the anion exchange membrane, and chlorine ions (Cl^-) Cannot pass through the cation exchange membrane, so that the regenerated hydrochloric acid eluent and the concentrated metal ion concentrate can be obtained from the hydrochloric acid eluent containing metal ions. Further, since water from which both metal ions and chlorine ions have been removed is obtained from the desalting chamber, it can be used as dilution water for adjusting the concentration of the eluent.
[0018]
As in the present invention, a normal electrodialyzer as shown in FIG. 1 is not necessary if only a small amount of metal ions are collected and concentrated from a large amount of hydrochloric acid solution to regenerate hydrochloric acid. For example, even with an apparatus using only a cation exchange membrane as shown in FIG. 2, it is possible to concentrate metal ions and regenerate the eluent. This will be described. In the apparatus 11 of FIG. 2, a cation exchange membrane 14 is disposed between the positive electrode 12 and the negative electrode 13. When a hydrochloric acid-eluted solution 17 containing a trace amount of uranyl ions is introduced into the processing chamber 15 while passing a current between both electrodes, a trace amount of uranyl ions UO contained in the eluate is introduced.₂ ²⁺Is drawn to the negative electrode 13, passes through the cation exchange membrane, and enters the metal ion concentration chamber 16. As a result, a regenerated eluent from which the metal ions have been removed is obtained from the processing chamber 15, and a concentrated solution from which the metal ions are concentrated is obtained from the metal ion concentration chamber 19. In this embodiment, an eluent solution containing metal ions (for example, the same as the hydrochloric acid eluent solution 17 introduced into the treatment chamber) can be used as the introduction solution into the concentration chamber. In the present invention, a metal ion concentrated solution and a metal ion can be obtained from a metal ion solution by using a membrane that does not transmit water like a direct current electric field and an ion exchange membrane but can selectively transmit ions. The methods for obtaining the removal liquid are collectively referred to as “electrodialysis method”.
[0019]
In addition, in the case where the eluent regeneration and metal concentration in the third step of the present invention are performed by electrodialysis, in addition to the ion exchange membrane, an ion exchange resin in the desalting chamber (processing chamber) and / or the concentration chamber, When loaded with at least one ion exchanger or chelate material selected from ion exchange fiber, ion exchange net, chelate resin, chelate fiber, chelate net, etc., and used as an ion transfer medium, metal separation performance, separation efficiency It is preferable because electrical characteristics and the like are remarkably improved.
[0020]
As described above, by the third step of the method of the present invention, a regenerated eluent from which the eluting metal has been removed and a concentrated liquid in which the target metal has been concentrated are obtained. The regenerated eluent can be reused as the eluent in the first step and / or the second step after adjusting the concentration as necessary. This makes it possible to effectively reuse the eluent used in the process.
[0021]
In the present invention, the target metal concentrate obtained as described above can be further brought into contact with a metal resorbing material different from the metal trapping material to adsorb the target metal (fourth step). This allows further enrichment and purification of uranium. The metal resorbing material that can be used in the fourth step can be selected from those having a chelate group having a large complex stability constant with uranium in an acidic solution. It goes without saying that the type of metal resorbing material used is determined depending on the type of metal to be recovered, and it is easily determined by those skilled in the art which metal resorbing material is preferable for which metal. can do. The metal resorption material that can be used includes bead-like resin, fiber material, woven or non-woven material, net-like material, sponge-like material, plate-like material, film-like material, or processed products thereof. Forms can be used.
[0022]
As the metal resorbing material used in the collecting material and the fourth step, a chelate resin can be preferably used. As the chelate resin used for this purpose, those having a three-dimensional network structure in which polystyrene is cross-linked can be used, but the chelate resin using graft polymerization is more adsorbed and diffused with the eluent. This is advantageous in terms of speed and separation efficiency from other metals. In addition, a material having a functional group particularly having an affinity for a specific metal, for example, a material made of an inclusion compound can be used as a collecting material and / or a metal resorbing material.
[0023]
  In the method of the present invention, an eluent having a concentration higher than the eluent concentration in the first step but lower than the eluent concentration in the second step is used between the first step and the second step. A step of contacting with the collecting material can be further included. Seawater contains not only uranium but also other useful metals such as vanadium, titanium, cobalt, etc., and these can also be collected with a metal collecting material. When the concentration of the eluent brought into contact with the collection material is increased stepwise, specific metal ions are eluted corresponding to the concentration. By this method, it is possible to prevent other metal ions from being mixed in the eluent of the metal for recovery. In this case, the concentration of the eluent used in each elution step is selected such that only a desired specific metal ion is eluted. Such concentration varies depending on the type of metal ion to be recovered and the type of eluent used, but can be determined empirically by conducting a prior test. In this embodiment, the eluted liquid from which the specific metal ions obtained in each stage are eluted is separately added to the third solution.ProcessTo concentrate the target metal and regenerate the eluent.
[0024]
  In the method of the present invention, the used eluent obtained in the first step and / or the treated eluent obtained in the fourth step (uraniumThe eluent after having been re-adsorbed to the metal re-adsorption material) can be used as a collecting material cleaning liquid before the first step after adjusting the concentration as necessary. A large amount of marine organisms, their secretions and carcasses adhere to the trapping material immersed in seawater for a long time. Most of these deposits can be removed by contacting with an aqueous solution having a composition different from that of seawater. The reason for this is unknown, but it seems that osmotic pressure, pH, and the like are influencing. Therefore, it is desirable to wash the trapping material before the first step of the method of the present invention. As the cleaning solution used for this purpose, the used eluent obtained in the first step or obtained in the fourth step.uraniumThe resorbed eluent can be used with the concentration adjusted appropriately.
[0025]
  Also obtained in the fourth step of the method of the present invention.uraniumThe resorbed eluent has a concentration higher than that of the eluent used in the second step.Because it is belowAnd this as appropriateAdjustmentAfter that, it can be used as an eluent in the first step.
[0026]
If the above method is adopted, the eluent used in the first step and / or the fourth step can be reused, and the used eluent can be reused more effectively in the process. .
[0027]
  In the method of the present invention, obtained in the fourth stepuraniumIn the metal re-adsorption material that re-adsorbeduraniumIs concentrated to a very high concentration. Take out the resin and disassemble ituraniumCan be recovered. Also, using an eluent having a higher concentration than the eluent used in the fourth step,uraniumBy contacting with a resorbed metal resorbing materialuraniumCan also be recovered in the eluent.
[0028]
  As an example of the metal trapping material that can be treated by the method of the present invention, a metal trapping material containing an amidoxime group and / or an imidodioxime group as a functional group can be mentioned. A chelate functional group called an amidoxime group has a large complex stability constant with a useful metal such as uranium in seawater, and is the chelate functional group most suitable for use in recovering uranium from seawater. It is said that the amidoxime group deammonifies and easily migrates to the imidodioxime group, but any functional group can be used for the metal scavenger. By mooring the trapping material having such a functional group in the ocean current, it is possible to collect a useful metal such as uranium in the seawater using a natural current such as an ocean current. As another example of the metal collector, iminoTheExamples thereof include a collecting material for adsorbing iron, copper, cobalt, nickel and the like having an acetic acid group, and a collecting material for mercury having a thiol group.
[0029]
Moreover, as an example of the form of the metal trapping material that can be treated by the method of the present invention, a woven fabric or a nonwoven fabric material that is an aggregate of fibers can be cited. By using a woven or non-woven fabric as the form of the collecting material, the advantage of the surface area can be utilized, and the woven or non-woven fabric can be easily formed into an arbitrary shape. It is easy to adopt the adsorption method used. The amount of useful metal adsorbed increases as the amount of seawater flowing into the collection material increases. In the case of the conventional bead-shaped resin, since it is a packed tower system, the pressure loss is large and the amount of inflowing seawater is small.
[0030]
Further, the metal scavenger that can be treated according to the present invention has a polymer side chain introduced with a desired chelate functional group on the main chain of the polymer base material by using a radiation graft polymerization method. It is preferable that The adsorption and elution characteristics of the metal collector have an important influence not only on the type of chelate group but also on the structure of the polymer chain. As described above, when a graft side chain is introduced onto the main chain of the polymer base material, the graft chain is not cross-linked, so the momentum is extremely large, and a large adsorption rate and diffusion rate can be obtained. Therefore, it is particularly excellent for efficiently adsorbing a small amount of 3 ppb of uranium and other useful metals present in a medium with a high salt concentration called seawater, and also for fractionating and eluting with high efficiency.
[0031]
The radiation graft polymerization method is a method in which a desired graft polymer side chain can be introduced into a substrate by irradiating a polymer substrate with radiation to generate radicals and reacting with the graft monomer. The number and length of the metal can be controlled relatively freely, and polymer side chains can be introduced into existing polymer materials of various shapes including woven / nonwoven fabrics. It is most suitable to use for the purpose of manufacturing.
[0032]
Examples of radiation that can be used in the radiation graft polymerization include α rays, β rays, γ rays, electron beams, and ultraviolet rays, and γ rays and electron beams are particularly preferable. In the graft polymerization method, after irradiating the substrate with radiation, the pre-irradiation graft polymerization method in which a polymerizable monomer is brought into contact with each other to carry out a graft polymerization reaction, and radiation in the presence of the substrate and the polymerizable monomer are performed. There are simultaneous irradiation graft polymerization methods for irradiating, but any method can be adopted in the production of the metal collecting material treated by the method of the present invention.
[0033]
For example, when a metal trapping material in the form of a nonwoven fabric containing an amidoxime group and / or an imidodioxime group is used as a metal trapping material that can be treated by the method of the present invention, the amidoxime group and / or the imidodioxime group is It can be formed by graft polymerization onto a nonwoven fabric substrate using acrylonitrile as a polymerizable monomer (graft monomer) and amidoximation with hydroxylamine or the like.
[0034]
In addition, when an electrodialysis method is used in the third step of the method of the present invention, an ion exchanger such as an ion exchange resin, ion exchange fiber, ion exchange net, chelate resin, chelate fiber, chelate net or the like preferably used in an electrodialysis tank or As the chelating material, a material in which a polymer side chain having a desired functional group is introduced onto the main chain of the polymer base material by using a radiation graft polymerization method can be used. These materials may be those having a three-dimensional network structure in which polystyrene is cross-linked, but ion exchangers or chelate materials in which functional groups are introduced into a polymer substrate using a radiation graft polymerization method. However, it is advantageous in terms of adsorption rate, eluent diffusion rate, separation efficiency from other metals, and the like.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
A method according to one embodiment of the present invention will be described with reference to the drawings.
[0036]
  FIG. 3 is a flow sheet illustrating a method according to an aspect of the present invention. From seawater according to the method indicated in the flow sheeturaniumA method for recovering will be described.
[0037]
A metal trapping material that has been moored in the ocean current for a predetermined period and adsorbs a useful metal in the seawater is filled into the metal trapping material elution tank 21. Since many seawater organisms and their secretions are attached to the collection material, the attached material can be removed by washing with the first-step eluted liquid 25 first. Further, pure water may be used as the cleaning liquid, or the re-adsorbed waste liquid 7 from the fourth step described later may be appropriately diluted. Since the cleaning waste liquid 31 from this cleaning step contains biological solids and organic matter, a predetermined water treatment is performed in a discharge water treatment device (not shown) so as to reach the drainage regulation value. Then release. In FIG. 3, the cleaning is performed in the elution tank 21, but when the cleaning efficiency is poor, another cleaning tank (not shown) may be provided and the cleaning may be performed there.
[0038]
A first eluent 33 having a low concentration, for example, a low concentration hydrochloric acid having a concentration of 0.1 N or less, is brought into contact with the cleaned metal collecting material to elute and remove calcium, magnesium, and the like (first step). The waste liquid containing calcium, magnesium, and the like from this step in a high concentration can be stored in the first-step eluted liquid storage tank 25 and used as a cleaning solution in the next process.
[0039]
  Next, a second eluent 24 having a concentration higher than that of the first eluent, for example, hydrochloric acid having a concentration of 0.5 N or more is brought into contact with the collection material,Such as uraniumThe useful metal is eluted (second step). The obtained eluent is stored in the storage tank 26. In this eluent,uraniumIs contained at a certain level (in the order of several ppm). In the second step, in order to push out the eluent remaining in the collecting material, it is preferable that the pusher is further passed after the eluent is passed. As the extrusion liquid used for this purpose, water, or, in some cases, treated tap water or seawater can be used.
[0040]
The eluent 26 in the second step is then sent to an electrodialyzer 27 having a structure as shown in FIG. 1, for example, and subjected to electrodialysis to remove the regenerated eluent from which the contained metal has been removed and the target metal. A concentrated solution 28 is obtained (third step). The regenerated eluent can be reused as the first eluent 23 and / or the second eluent 24 after adjusting the concentration as necessary.
[0041]
The concentrated liquid 28 can then be passed through the metal resorbing material tank 22 to further concentrate the metal for recovery contained in the liquid. The metal resorbing material tank 22 is filled with a chelate resin or the like that can resorb the target metal. For example, when the purpose is to recover uranium, the metal resorbing material tank 22 can be filled with a resin mainly composed of amidoxime groups. In the metal resorbing material tank 22, the target metal is resorbed by the resin (fourth step). The drainage from the fourth step has a slightly lower concentration than the second eluent due to the addition of the extrusion solution and the cleaning solution, but it can be used sufficiently as the first eluent, so the concentration can be adjusted as appropriate. Thus, the first eluent 23 can be used. Alternatively, the drained liquid from the fourth step can be used as the cleaning liquid before the first step.
[0042]
The target metal re-adsorbed on the metal re-adsorption material can be directly recovered by decomposing the resin. When the metal is adsorbed on the resin, it is convenient for transportation, and it is advantageous when the metal is purified and recovered elsewhere. Alternatively, the material re-adsorbed with metal is brought into contact with an eluent 29 having a higher concentration, for example, hydrochloric acid with a higher concentration (for example, 1 to 5 N), and the metal adsorbed on the re-adsorbed material is again eluent. 29 can also be eluted. The eluted liquid 30 obtained from this step contains the target metal at a very high concentration and can be recovered by methods well known in the art.
[0043]
【The invention's effect】
According to the method of the present invention,uraniumCan be recovered from the metal collector in a purified state, so that uranium can be collected from seawater.can do. In addition, the present invention method can be applied to, for example, collecting and removing harmful metals such as cadmium, lead, and copper in river streams, collecting and removing harmful metals such as mercury from factory wastewater, or nickel from the effluent of the nickel plating process. If diverted to removal technologyThe recovery efficiency can be remarkably increased. Moreover, since the used eluent can be reused as much as possible, the cost for recovery can be further reduced. Therefore, the method of the present inventionFutureIt is important to contribute to energy, resources and environmental issues.
[0044]
【Example】
Manufacture of metal collector
60 g / m per unit area made of polyethylene fiber having a fiber diameter of 10 to 20 μm²The non-woven fabric was irradiated with 150 kGy of γ rays in a nitrogen atmosphere, then immersed in a mixed monomer solution of acrylonitrile and methacrylic acid, and reacted at 50 ° C. for 6 hours to perform graft polymerization. Next, the nonwoven fabric was immersed in dimethylformamide, washed at 50 ° C. for 3 hours, and then weighed. As a result, a graft ratio of 132% was obtained.
[0045]
Hydroxylamine hydrochloride was added to a mixed solution of 50% methanol and 50% water to a concentration of 3%, and the graft nonwoven fabric obtained above was immersed in this solution and reacted at 80 ° C. for 1 hour for amidoximation. It was. Next, it was immersed in a 2% aqueous solution of potassium hydroxide and subjected to alkali treatment at 80 ° C. for 1 hour. This nonwoven fabric was thoroughly washed with pure water and used as a metal collecting material.
[0046]
Adsorption collection of useful metals in seawater
Ten test samples of 20 cm × 30 cm were cut out from the nonwoven metal collection material obtained above and accommodated in a cage made of a stainless steel wire mesh. A cage containing a test sample was moored in a sea area where the ocean current velocity was about 1 m / sec (water depth of about 3 m) and placed for about 3 weeks to collect and adsorb useful metals in seawater. The uranium concentration in the seawater in this sea area was 3.1 ppb.
[0047]
Recovery of useful metals
The metal collecting material that had been adsorbed to useful metals and was lifted from the sea was washed. As the cleaning liquid, a waste liquid after passing 0.1 N hydrochloric acid through the collecting material was used. Next, the collecting material was packed in an elution column (diameter 50 mm). As a packing method, a 20 cm × 30 cm non-woven fabric collecting material was wound in a roll shape by 5 sheets, and this was stacked in two stages to a height of 40 cm and accommodated in a column.
[0048]
Through the column, 1200 ml of 0.1N hydrochloric acid was passed, and the effluent from the column was stored for the next washing. This effluent contained high concentrations of calcium and magnesium, but contained almost no useful metals such as uranium and vanadium.
[0049]
Next, 1200 ml of 0.5 N hydrochloric acid was passed through the column, and in order to push out the remaining liquid, 600 ml of water was passed through the column as the push liquid. The uranium concentration in 1.8 liters of the total effluent from the column was measured and found to be 4.7 mg / l. The second elution-treated collection material was disassembled, and the amount of uranium that could not be eluted with 0.5 N hydrochloric acid was measured. The result was 0.1 mg or less, and 95% or more of the collected uranium was efficiently obtained. It was found that elution was possible.
[0050]
As shown in FIG. 1, the obtained second eluted solution (uranium concentration 4.7 mg / l) was placed between an anode and a cathode having an area of 5 cm × 10 cm, a strongly acidic cation exchange membrane (manufactured by Asahi Glass Co., Ltd., Electrodialyzer (acid concentrating chamber and metal concentrating chamber) in which a trade name Selemion CMV) and a strongly basic anion exchange membrane (Asahi Glass Co., Ltd., trade name Selemion AMV) are arranged with a spacing of 3 mm between them via a spacer net. Was passed through a desalting chamber having a thickness of 3 mm) at a flow rate of 10 ml / min, and a current of 0.2 A was applied. A 0.5 N hydrochloric acid solution was circulated and supplied to the acid concentrating chamber, and the second eluted solution was circulated and supplied to the metal concentrating chamber. Uranium moved into the metal concentration chamber on the cathode side, and a concentrated solution containing uranium at a concentration of about 13 mg / l was obtained. The uranium concentration in the effluent from the desalting chamber is as low as 0.02 mg / l, and the effluent from the acid concentrating chamber on the anode side contains almost no uranium. It was reusable as an eluent or a solution for adjusting the concentration of the eluent.
[0051]
The uranium-containing concentrate obtained from the electrodialyzer was further filled with 5 ml of a bead-shaped chelate resin having a large complex stability constant with respect to uranium (product name: Uniselec UR-3100). The adsorption column was passed through SV3 to resorb uranium on the resin. The uranium concentration in the effluent from the resorption column was measured and found to be 0.013 ppm, indicating that most of the uranium was resorbed on the chelate resin. It was found that the uranium concentration in the resin was 0.18%, which was concentrated about 600,000 times from the concentration of 3 ppb in seawater. The effluent from this column was also reusable as the eluent or its concentration adjusting liquid.
[0052]
As a result of using the recovered hydrochloric acid as the eluent in each of the above steps, the consumption of hydrochloric acid was reduced to about 35% of the initial time.
[Brief description of the drawings]
FIG. 1 is a diagram showing a concept of an electrodialysis apparatus that can be used in the present invention.
FIG. 2 is a diagram showing the concept of another embodiment of an electrodialysis apparatus that can be used in the present invention.
FIG. 3 is a flow sheet of a metal recovery method according to an aspect of the present invention.
[Explanation of symbols]
1,11 Electrodialyzer
21 Metal collector elution tank (first and second steps)
22 Metal resorption material tank (4th process)
23 First eluent
24 Second eluent
25 First step eluted liquid storage tank
26 Second Step Eluted Liquid Reservoir
27 Eluent regeneration / metal concentration tank (third step)
28 Metal concentrate
29 Eluent for metal resorption material
30 Elution liquid of metal resorption material
31 Effluent water

Claims (4)

A low concentration acid eluent is brought into contact with a metal scavenger containing amidoxime groups and / or imidodioxime groups introduced to a woven fabric or non-woven fabric adsorbed with a metal containing uranium using a radiation graft polymerization method. 1 step; a second step in which an acid eluent having a higher concentration than that in the first step is brought into contact with the metal scavenger to recover uranium in the acid eluent; obtained in the second step using electrodialysis Regeneration of the spent acid eluent, and at the same time, the third step to make the recovered uranium a further concentrated concentrate; the uranium concentrate obtained in the third step is brought into contact with the metal resorption material to resorb uranium And a fourth step, wherein the acid eluent regenerated in the third step and the fourth step is reused as the acid eluent in the first step and / or the second step. Elution recovery method of uranium from materials. The method of claim 1, further comprising the acid eluent being hydrochloric acid. The method according to claim 1, further comprising a pretreatment step of cleaning the metal collection material by bringing the spent acid eluent from the first step into contact with the metal collection material before the first step. In the electrodialysis, in addition to the ion exchange membrane, at least one ion exchanger or chelate material selected from ion exchange resin, ion exchange fiber, ion exchange net, chelate resin, chelate fiber, and chelate net is used as an ion transfer medium. The method of Claim 1 used as.

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