JP7266213B2 - Separating agent and manufacturing method thereof - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law "Lecture number: PA348, Lecture title: Development of highly functional adsorbent by chemical modification of activated carbon surface and evaluation of organic compound and metal adsorption capacity"

TECHNICAL FIELD The present invention relates to a separating agent derived from activated carbon, which can separate and purify metals from aqueous solutions containing metals such as seawater.

Rare metals such as cobalt (Co) and nickel (Ni) are important metals in electronic materials, battery electrodes, and the like, and are indispensable resources at present. However, new mining of rare metals involves problems such as environmental pollution and carbon dioxide emissions, and is not easy. On the other hand, efforts are being made to recycle rare metals, but there is the problem of high costs. Therefore, in recent years, attention has been focused on selectively separating and recovering rare metals from seawater.

By the way, at present, solvent extraction is widely known as an industrial method for recovering rare metals and other metals from an aqueous solution. Solvent extraction is a separation technique that utilizes the partitioning of substances between two immiscible phases, typically an aqueous solution and an organic solvent. Therefore, a large amount of organic solvent is required to recover a large amount of metal by solvent extraction. However, many organic solvents are highly volatile and toxic, and their usage is strictly limited in consideration of safety.

For this reason, the development of methods to replace the solvent extraction method has been advanced, and in recent years, an extractant impregnated resin technology called Extractant impregnated resins (EIR) has been proposed (Non-Patent Document 1). By impregnating a resin having pores with an extractant, this product can exhibit the properties of the extractant without using an organic solvent. However, in EIR, there is a risk that the production cost of the resin used is high, and that the resin used deteriorates and decomposes. Moreover, there is a risk that the impregnated extractant may leak into the metal-containing aqueous solution during the metal recovery operation.

On the other hand, activated carbon, which is mainly composed of carbon, has pores on its surface, is non-polar, and has a high ability to extract organic compounds. Therefore, it is used as a deodorizing and decolorizing agent for removing organic compounds in gas and liquid phases. In addition, activated carbon has functional groups such as carboxy groups and hydroxyl groups on its surface, and it is possible to extract metal ions. Therefore, it is expected to be used as a metal recovery method in place of the solvent extraction method. However, since activated carbon generally has random pore sizes, once it is extracted (adsorbed), it is difficult to desorb the extract (adsorbate). Therefore, although it is used to remove harmful substances, it is difficult to use it for the purpose of extracting and desorbing useful substances for reuse.

K. Babic, Louis van der Ham, Andre de Haan, "Recovery of benzaldehyde from aqueous streams using extractant impregnated resins", Reactive and functional polymers, 66, 2006, p1494 - 1505.

The present invention has been made in view of such circumstances, and it is not necessary to use an organic solvent to recover useful metals, etc., and it can be produced at low cost, and the added extractant is in the solution. It is an object of the present invention to provide a reusable separating agent that leaks less and a method for producing the same.

In order to achieve the above object, the gist of the present invention is the following [1] to [10].
[1] A separating agent having a support and a chelating agent for extracting substances to be separated, wherein the chelating agent is added in an amount of 10 to 250% by mass based on the support.
[2] The separating agent according to [1], wherein the support has a specific surface area of 1000 to 5000 m ² /g.
[3] The separating agent according to [1] or [2], wherein the separating agent has a specific surface area of 50 to 4500 m ² /g.
[4] The separating agent according to any one of [1] to [3], wherein the chelating agent is 2-isonitrosopropiophenone.
[5] The separating agent according to any one of [1] to [4], wherein the carrier is a carbon porous material.
[6] A method for producing a separating agent in which 10 to 250% by mass of a chelating agent is applied to a carrier, comprising the steps of preparing the carrier and the chelating agent, and dissolving the chelating agent in a solvent. a step of immersing the support in the chelate solution to impregnate the inside of the support with the chelate solution; and removing the solvent from the support impregnated with the chelate solution. A method for producing a separating agent, comprising the step of removing
[7] The method for producing a separating agent according to [6], wherein the support has a specific surface area of 1000 to 5000 m ² /g.
[8] The method for producing a separating agent according to [6] or [7], wherein the separating agent has a specific surface area of 50 to 4500 m ² /g.
[9] The method for producing a separating agent according to any one of [6] to [8], wherein the chelating agent is 2-isonitrosopropiophenone.
[10] The method for producing a separating agent according to any one of [6] to [9], wherein the carrier is a carbon porous material.

That is, the present inventors have conducted extensive research on techniques for separating and purifying metals from aqueous solutions containing metals such as seawater without using organic solvents. In the course of this research, we focused on activated carbon, which has a high specific surface area and has been used as a porous extractant, and further studied it. As a result, the present inventors have found that the above problems can be solved by using activated carbon as a carrier and adding a chelating agent to it as a separating agent, and have completed the present invention.

Since the separating agent of the present invention does not require the use of an organic solvent when separating metals, it can be used safely without being exposed to danger during separation work. In addition, by adding a chelating agent to the carrier, leakage of the organic solvent is reduced during use, and the carrier is excellent in durability.

FIG. 2 is a diagram showing the relationship between the pH of an aqueous metal solution and the metal extraction rate for a separating agent that is an embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the pH of the aqueous metal solution and the metal extraction rate for comparative examples of the separating agent. FIG. 5 is a diagram showing the relationship between the pH of the aqueous metal solution and the metal extraction rate for other comparative examples of the separating agent. FIG. 2 is a diagram showing the relationship between the equilibrium concentration of cobalt and the adsorption amount for a separating agent that is an embodiment of the present invention and a comparative example thereof.

Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to this embodiment.

The separating agent of the present invention has a support and a chelating agent, and is a separating agent for extracting substances to be separated, wherein 10 to 250% by mass of the chelating agent is added to the support. be. In the present invention, the separating agent means one that separates the metal from the aqueous solution by extracting the metal from the aqueous solution containing the metal, extracting a specific metal from the aqueous solution containing a plurality of metals, Separating them is also included. Furthermore, the separating agent of the present invention also means re-dissolving the once-extracted metal in another solution to separate the separating agent and the metal.
The carrier, the chelating agent, and the separating agent itself, which are the materials of the separating agent of the present invention, are described in detail below.

[Carrier]
As the carrier, those having high affinity to organic compounds, which are not decomposed or denatured in an aqueous solution, and those which are easily recovered from water can be used. Specific examples include porous resins and polymers. Among them, activated carbon is preferably used.

The activated carbon is a porous material obtained by activating a carbonaceous material such as coconut shells and/or a carbonized material of the carbonaceous material (hereinafter sometimes collectively referred to as "carbonized material").
The activation treatment is a treatment for forming pores on the surface of the carbonized material to increase the specific surface area and pore volume.

The carbonaceous substance is not particularly limited as long as it is a carbonaceous substance known as a raw material for activated carbon. Non-graphitizable carbon such as wood, sawdust, charcoal, coconut shell, cellulose fiber, synthetic resin (e.g. phenolic resin); mesophase pitch, pitch coke, petroleum coke, coal coke, needle coke, polyvinyl chloride, polyimide, graphitizable carbon such as PAN; and mixtures thereof. These carbonaceous substances may be used alone or in combination of two or more. Preferred is petroleum coke. These may be used alone or in combination of two or more.

The above carbonaceous material may be subjected to a high-temperature carbonization treatment before the activation treatment, if necessary. Examples of the high-temperature carbonization treatment include heat treatment of the carbonaceous material in an inert gas at 400° C. to 1000° C. for 1 to 3 hours.

Methods for activating the carbonized material include gas activation and chemical activation.
The gas activation is a method of heating the carbonized material to a predetermined temperature and then supplying an activation gas to activate the carbonized material. Steam, air, carbon dioxide gas, oxygen, combustion gas, and mixed gases thereof can be used as the activation gas.
The chemical activation is a method in which a carbonized material and an activator are mixed and heated to perform an activation treatment.
In the method for producing activated carbon of the present invention, the method of activating the carbonized material is not particularly limited. It is preferable to employ an alkali activation treatment method that obtains activated carbon. Alkali activation results in a carbonized material with a higher specific surface area.

The above-mentioned alkali activator is not particularly limited, but alkali metal hydroxides (caustic alkali) such as potassium hydroxide, sodium hydroxide and lithium hydroxide, alkaline earths such as barium hydroxide, etc. Materials containing metal hydroxides, alkali metal carbonates such as potassium carbonate, sodium carbonate, and lithium carbonate can be used. Among them, potassium hydroxide and sodium hydroxide are preferably used. These may be used alone or in combination of two or more.

The shape of the carbonized material may be, for example, granular, powdery, fibrous, etc., and the granular one is preferably used. Among them, it is preferable to use a material having a smaller particle size and a broader particle size distribution than general carbonized materials.

The ratio of the mass of the alkali component of the alkali activator to the mass of the carbonized material (hereinafter, this ratio may be referred to as "KOH/C") is not particularly limited, but is usually from 1 to 5.

In order to produce activated carbon using the carbonized material and the alkali activator, for example, the carbonized material and the alkali activator are placed in a reaction vessel of an activated carbon production apparatus and heated to activate the carbonized material. to obtain activated carbon. This activation treatment is usually carried out under heating at about 400 to 1000° C. for about 0.1 to 20 hours. The above heating temperature and heating time are only examples, and can be appropriately adjusted depending on the types and amounts of the carbonized material and alkali activator used. Then, activated carbon can be obtained by discharging the activated carbonized material (reactant) from the reaction vessel and, if necessary, performing alkali cleaning, granulating, acid cleaning, dehydration, and the like.

The specific surface area of the activated carbon is not particularly limited, but the specific surface area is preferably in the range of 1000 to 5000 m ² /g, more preferably in the range of 2000 to 4000 m ² /g, and still more preferably. is in the range of 2500-3500 m ² /g. Also, the average pore diameter is preferably 0.3 to 10 nm, more preferably 0.5 to 2.5 nm. The above specific surface area and average pore diameter are values calculated from a nitrogen adsorption isotherm obtained by a nitrogen gas adsorption method using a specific surface area/pore size distribution measuring device.

[Chelating agent]
The chelating agent is not particularly limited, but examples include 2-isonitrosopropiophenone, di-(2-ethylhexyl) phosphate (D2EHPA), di-(2-ethylhexyl) phosphonic acid (PC88A), di -(2-Ethylhexyl)phosphinic acid, oxime-based extractants (LIX-based extractants, etc.), phosphoric acid-based extractants (Cyanex-based extractants, etc.), and the like. Among them, it is preferable to use 2-isonitrosopropiophenone.

2-Isonitrosopropiophenone (hereinafter sometimes referred to as "INP") is a white to pale yellow crystal and crystal powder compound (MW: 163.18) at room temperature (about 23°C). It is represented by the following structural formula (1).

In the separating agent of the present invention, the amount of the chelating agent applied to the support is in the range of 10 to 250% by mass, preferably 20 to 200% by mass, more preferably 50 to 180% by mass. If the amount of the chelating agent applied is too large, there is a concern that the pores of the carrier will be clogged and the surface of the carrier will be excessively covered. On the other hand, if the amount is too small, the effect as a separating agent tends to decrease.

For producing the separating agent of the present invention from the activated carbon and INP, for example, the following procedure is performed. First, INP is dissolved in a solvent to prepare an INP solution. Next, the activated carbon is immersed in the prepared INP solution and stirred to impregnate not only the surface of the activated carbon but also the inside thereof with the INP solution. Then, by removing the solvent from the activated carbon impregnated with the INP solution while leaving the activated carbon in the INP solution, the activated carbon with INP of the present invention can be obtained.

Examples of solvents used in the INP solution include alcohols, aromatic hydrocarbons, etc. Specifically, methanol, ethanol, isopropanol, n-butanol, t-butanol, allyl alcohol, toluene, etc. can be used. Among them, ethanol is preferably used because of its excellent solubility of INP and low environmental load.

The INP solution usually contains 0.1 to 70 mmol (hereinafter sometimes referred to as "mM") of INP in a solvent, preferably 1 to 60 mM, more preferably 3 to 50 mM. Preferably 5 to 15 mM.

The ratio of the INP solution to the activated carbon may be any as long as 10 to 250% by ^mass of INP is applied to the activated carbon. 5.0 cm ³ (apparent volume), preferably 0.2 to 3.0 cm ³ , more preferably 0.5 to 2.0 cm ³ .

The time for impregnating the activated carbon with the INP solution is usually about 1 to 36 hours, preferably 2 to 30 hours, more preferably 4 to 24 hours, and still more preferably 5 to 10 hours. The temperature of the INP solution at that time is usually 10 to 50°C, preferably 20 to 40°C, more preferably 25 to 30°C.

The method for removing the solvent from the activated carbon impregnated with the INP solution is not particularly limited, and examples thereof include heat removal, vacuum distillation, and air drying.

The separating agent obtained as described above is suitably used for separating and recovering metals, particularly rare metals, from objects to be separated. For example, it is used for aqueous solutions containing metals such as seawater (hereinafter sometimes referred to as "metal aqueous solutions"). Such metal aqueous solutions include, for example, various metals (for example, platinum group metals, gold, silver, copper, nickel, chromium, vanadium, cobalt, lead, zinc, etc.) or aqueous solutions containing these metal compounds, general river water, lake water, seawater, soil elution water, industrial water, biological treatment Examples include water, factory wastewater, mine wastewater, and hot spring water. The separating agent of the present invention can extract, recover, remove, and separate metals from these metal aqueous solutions. Among others, it is suitable for extraction and separation of Co and Ni.

In addition, since the separating agent of the present invention does not contain an organic solvent, it can be used in fields that have not been industrially used so far. That is, by using it as a substitute for organic solvents, it is expected that environmental pollution by organic solvents can be prevented. In addition, it is possible to increase the availability of various extractants that are sparingly soluble in organic solvents.

The above separating agent can be used according to a conventional method. For example, it can be used by adding to an aqueous metal solution at room temperature (about 23° C.) and stirring, or by pouring the aqueous metal solution into a cylinder filled with a separating agent.

The separating agent of the present invention is obtained by adding 10 to 250% by mass of a chelating agent such as INP to a carrier such as activated carbon. In particular, it is preferable that 50 to 200% by mass of the chelating agent is added to the carrier, because the extraction capacity of the target separation target is further increased.

Although the specific surface area of the separating agent of the present invention is not particularly limited, it is preferably in the range of 50 to 4500 m ² /g, more preferably 100 to 4000 m ² /g, still more preferably 150 to 3000 m 2 /g, and more preferably 150 to 3000 ^{m 2} /g. More preferably 200 to 2500 m ² /g. If the specific surface area of the separating agent is too low, the number of extraction sites for extracting objects to be separated tends to decrease, and if it is too large, the effect as a separating agent tends to be reduced.

Although the total pore volume of the separating agent of the present invention is not particularly limited, it is preferably in the range of 0.05 to 2 cm ³ /g, more preferably 0.1 to 0.8 cm ³ /g. If the total pore volume of the separating agent is too large, the pore volume ratio of a size suitable for extraction of the target separation target will decrease, and the extraction amount will tend to decrease. The pore volume itself, which has a size suitable for extracting the object, also decreases, and there is a tendency that a sufficient amount of extraction cannot be obtained.

Next, examples will be described together with conventional examples and comparative examples. However, the present invention is not limited to the following examples.

[Example 1]
0.5 g (3.0 mM) of INP was added to 100 cm ³ of ethanol, and this was stirred at a temperature of 30° C. with an evaporator without reducing pressure to prepare an INP solution. 1.0 g of activated carbon (MSC30, manufactured by Kansai Coke and Chemicals Co., Ltd.) was added to the INP solution, and the mixture was further stirred for 12 hours to impregnate the inside of the activated carbon with the INP solution. Thereafter, while the activated carbon was immersed in the INP solution (without removing the activated carbon from the INP solution), the evaporator was depressurized to remove ethanol under reduced pressure, thereby imparting 50% by mass of INP to the activated carbon. A separating agent is obtained.

[Example 2]
A separating agent having 100% by mass of INP with respect to the activated carbon was obtained in the same manner as in Example 1, except that the amount of INP was changed to 1.0 g (6.0 mM).

[Example 3]
A separating agent having 200% by mass of INP based on activated carbon was obtained in the same manner as in Example 1, except that 2.0 g (12.0 mM) of INP was used.

[Comparative Example 1]
A commercially available activated carbon (MSC30, manufactured by Kansai Coke and Chemicals Co., Ltd.) was used as Comparative Example 1.

[Comparative Example 2]
1.223 g (7.5 mM) of INP was dissolved in 150 cm ³ of toluene to prepare a 50 mM-INP solution (Comparative Example 2).

The specific surface area, total pore volume and average pore diameter of the products of Examples 1 to 3 and Comparative Example 1 were measured and shown in Table 1 below. In addition, the measuring method of each item is as showing below.

<Specific surface area>
After vacuum heating 0.2 g of each example and comparative example product at 70 ° C., using a nitrogen adsorption apparatus (manufactured by Micromeritic, "ASAP-2420"), nitrogen adsorption under a liquid nitrogen atmosphere (77 K). An isotherm was determined, and the specific surface area (m ² /g) of each example and comparative example was determined by the BET method.

<Total pore volume>
A nitrogen adsorption isotherm was calculated for each example and comparative example product, and based on each nitrogen adsorption isotherm, relative pressure P/P ₀ (P: gas pressure of adsorbate in adsorption equilibrium, P ₀ : adsorption temperature The saturated vapor pressure of the adsorbate at 0.93 was obtained, and the nitrogen adsorption amount up to a pore diameter of 300 nm was obtained, and this was taken as the total pore volume (cm ³ /g) of each example and comparative example product.

<Average pore size>
Assuming that the pores of each example and comparative example are cylindrical, the average pore diameter was calculated based on the following formula.
Average pore diameter (nm) = (4 x total pore volume (cm ³ /g)) / specific surface area (m ² /g) x 1,000

なお、実施例３品は、実施例１および比較例１品に比べて比表面積が顕著に小さいと考えられ、上述の方法で比表面積が測定できなかったため、上記表１に記載していない。

The product of Example 3 is not listed in Table 1 above because it is considered that the product of Example 3 has a significantly smaller specific surface area than the product of Example 1 and Comparative Example 1, and the specific surface area could not be measured by the above method.

Next, the effects of pH and the extraction capacity were investigated and evaluated using the respective example products and comparative example products as appropriate. The method of examination and evaluation of each item is as shown below.

<Effect of pH>
An aqueous metal solution was prepared by adding 1 mM each of Co and Ni to a 3% by weight aqueous solution of ammonium chloride.
Initial pH was set from 3.0 to 9.0, and pH adjustment was performed using 0.1N-HCl and 0.1N-NaOH.
50 mg of the above Example 2 product or Comparative Example 1 product was added to a sample tube containing 10 cm ³ of the above metal aqueous solution and shaken at 30° C. and 120 rpm for 24 hours to extract the metal from the above metal aqueous solution. This is filtered, the pH after equilibrium is measured using a pH meter (LAQUA F-72S, manufactured by Horiba Ltd.), and the metal concentration of the metal aqueous solution is measured by an atomic absorption photometer (Z-2310, manufactured by Hitachi High-Technologies Corporation). ) were measured by the calibration curve method, and their extraction rates were determined by the following formula (1).
On the other hand, for Comparative Example 2, 10 cm ³ was added to an Erlenmeyer flask containing 10 cm ³ of the metal aqueous solution, and the metal was extracted from the metal aqueous solution by shaking at 30° C. and 120 rpm for 24 hours. After shaking, the aqueous metal solution was sampled, and the pH and metal concentration after equilibrium were measured in the same manner as in Example 2 and Comparative Example 1 to determine the extraction rate.

Extraction rate (%)=(C ₀ -C ₁ )/C ₀ ×100 (1)
C ₀ : metal concentration (mM) of metal aqueous solution before extraction
C ₁ : metal concentration (mM) of metal aqueous solution after extraction

These results are shown in FIG. 1 (Example 2 product), FIG. 2 (Comparative example 1 product) and FIG. 3 (Comparative example 2 product), respectively.
From the results shown in FIG. 1, it can be seen that the product of Example 2 has a high Co, Ni equilibrium extraction rate and excellent extraction ability. In addition, there was a tendency that Co was rapidly extracted near pH 5.0, and Ni was rapidly extracted near pH 6.0, suggesting that Co is preferentially extracted. This is thought to reflect the characteristics of INP used as an extractant.
From the results of FIG. 2, it was found that the extraction rate of the product of Comparative Example 1 increased as the pH of both Co and Ni increased. It is considered that this is because the functional group of the activated carbon is dissociated to become negatively charged and extract the metal cation. However, the extraction volume as a whole was small.
From the results of FIG. 3, it can be seen that Ni is hardly extracted in any pH range of the product of Comparative Example 2. As for Co, the extraction rate increased as the pH increased, and the extraction rate increased sharply from around pH 7.0 after equilibrium. From this, it is considered that INP has selectivity for Co. In addition, the extraction amount as a whole was small.

<Extraction capacity>
Regarding the products of Examples 1 to 3 and the product of Comparative Example 1, the relationship between the amount used and the amount of extracted metal was examined according to the following procedure.

An aqueous metal solution was prepared by adding 5 mM each of Co and Ni to a 3% by weight ammonium chloride aqueous solution.
The initial pH was set at 8.0, and pH adjustment was performed using 0.1N-HCl and 0.1N-NaOH.
After weighing out a predetermined amount (10-70 mg in increments of 10 mg) of each of the above Examples 1 to 3 and Comparative Example 1 in a prepared 30 cm ³ sample tube, 10 cm ³ of the above metal aqueous solution was added, and the mixture was heated to 30°C. , 120 rpm for 24 hours to extract the metal from the aqueous metal solution. The metal aqueous solution after shaking is collected, and the pH after equilibrium is measured using a pH meter (LAQUA F-72S, manufactured by Horiba, Ltd.), and the concentrations of Co and Ni are measured with an atomic absorption photometer (Z-2310 (manufactured by Hitachi High-Technologies Corporation) was measured by the calibration curve method to create an isotherm. An isotherm generated for Co is shown in FIG. From this result, it was found that the addition of INP increased the extractability by about four times.

As described above, the separating agent of the present invention has a high extractability and can be used as an extracting agent for metals. Further, the separating agent of the present invention can be fully expected to be used as an extracting agent in organic solvent extraction methods.

The separating agent of the present invention can be used when extracting and refining metals from aqueous solutions containing metals such as seawater.

Claims (6)

A separating agent having a carrier and a chelating agent for extracting a substance to be separated, wherein the chelating agent is added in an amount of 10 to 250% by mass relative to the mass of the carrier. , wherein the carrier is a carbon porous material and the chelating agent is 2-isonitrosopropiophenone . The separating agent according to claim 1, wherein the carrier has a specific surface area of 1000 to 5000 m ² /g. The separating agent according to claim 1 or 2, wherein the separating agent has a specific surface area of 50 to 4500 m ² /g. A chelating agent is provided by adding 10 to 250% by mass with respect to the mass of the carrier, the carrier is a carbon porous material, and the chelating agent is 2-isonitrosopropiophenone. A method for producing a separating agent, comprising the steps of preparing the support and the chelating agent, dissolving the chelating agent in a solvent to prepare a chelate solution, and dissolving the support in the chelate solution. and impregnating the inside of the support with the chelate solution; and removing the solvent from the support impregnated with the chelate solution. . 5. The method for producing a separating agent according to claim 4, wherein the support has a specific surface area of 1000 to 5000 m ² /g. The method for producing a separating agent according to claim 4 or 5, wherein the separating agent has a specific surface area of 50 to 4500 m ² /g.

Images