JP2013174532A - Magnetic adsorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily collecting separated harmful components by efficiently separating the harmful components from solution containing the harmful components, such as heavy metal ions and radioactive cesium.SOLUTION: Cesium is efficiently removed by using a magnetic adsorbent with magnetic material particles, cesium adsorptive compounds and hollow particles bound therewith by a binder, and the magnetic adsorbent is more easily collected by magnetic separation.

Description

  The present invention relates to a method for efficiently separating cesium from a solution containing at least cesium and easily recovering the separated cesium.

  Various methods have been studied to separate these from solutions containing harmful components such as heavy metal ions and radioactive cesium. Most simply, a method using an adsorbent such as activated carbon or ion exchange resin is widely used. When these adsorbents are used by adding them to the solution, it is necessary to separate the adsorbent from the treated solution, and this operation has been accompanied with great difficulty. In recent years, as superconducting magnets and high gradient magnetic separation technologies have advanced, the practicality of technologies for separating harmful components in solutions using magnetism has increased and has attracted attention. Furthermore, in the accident at the Fukushima Daiichi nuclear power plant that occurred in 2011, radioactive cesium was scattered over a wide area, and technology for separating radioactive cesium adhering to various substances has become necessary.

  Specific methods for separating harmful components include a method of imparting magnetism to the harmful component itself, a method of mixing the harmful component and magnetic particles and adding a flocculant to form a magnetic floc, activated carbon, There is a method of imparting magnetism to an adsorbent such as zeolite.

  Of these, the method of imparting magnetism to the harmful component itself lacks versatility. In addition, the method of forming a magnetic floc often requires a large amount of magnetic particles and an aggregating agent, and there is a problem that the processing becomes rather complicated. On the other hand, the method of giving magnetism to the adsorbent can be expected to have the advantage of being able to adsorb harmful components effectively, but it is practical to produce it at low cost by giving it high magnetism without reducing the adsorbent's original adsorption capacity. There is still no way.

  For example, a magnetic adsorbent having a magnetic core and an outer skin that covers the core and adsorbs metal ions has been proposed (see Patent Document 1). In addition, a magnetic adsorbent of a type in which a magnetic metal and an organic substance are supported on an inorganic porous material such as porous glass beads, silica gel, alumina, and zeolite, and the organic material is thermally decomposed to exhibit adsorption performance has been proposed. (See Patent Document 2). Furthermore, a method of combining iron oxide with a porous adsorbent such as silica gel, zeolite, activated carbon (see Patent Document 3), a magnetic adsorbent in which zeolite and magnetic particles are bonded with an adhesive (cement) (Patent Document 4, 5) has also been proposed. Since the magnetic adsorbent prepared by these methods has a high specific gravity, it tends to settle, and the probability of efficient contact between the magnetic adsorbent and metal ions in a solution containing metal ions is low. Therefore, there is a problem that a high stirring force is required.

Japanese Patent Laid-Open No. 10-99843 JP 2002-233754 A JP 2005-137773 A JP-A-1-194940 Japanese Patent Laying-Open No. 2005-177709

  The subject of this invention is providing the magnetic adsorbent which can isolate | separate these harmful components efficiently from the solution containing harmful components, such as a heavy metal ion and radioactive cesium, using a magnetic separation technique.

  By intensively researching the above problems and using a magnetic adsorbent in which magnetic particles, cesium adsorbing compounds, and hollow particles are bound together with a binder, cesium can be efficiently separated from a solution containing cesium. As a result, the present invention has been reached.

  In the present invention, a magnetic adsorbent obtained by binding magnetic particles, a cesium adsorbing compound, and hollow particles together with a binder is dispersed in a cesium-containing solution, and then recovered by magnetic separation. The magnetic adsorbent containing hollow particles moves quickly in the cesium-containing liquid with a small stirring force, so that the contact frequency between the contained cesium-adsorbing compound and cesium increases and can be adsorbed quickly. The time is short. Even if the cesium-containing solution contains impurities, it is possible to easily recover only the magnetic adsorbent that has adsorbed cesium by magnetic separation without removing these in advance. Even if contaminants are substances derived from sludge, soil, incineration ash, etc., there is no effect on magnetic separation. As a result, in the present invention, cesium can be separated from the cesium-containing solution by a very short and simple operation.

  The magnetic particles used in the present invention are not particularly limited, and any material exhibiting magnetism can be used. For example, powders of metals such as iron, nickel and cobalt or powders of magnetic alloys based on these metals, powders of metal oxide magnetic materials such as iron trioxide, iron sesquioxide, cobalt-added iron oxide, barium ferrite and strontium ferrite Is mentioned. The particle size of the magnetic particles is preferably 0.1 to 100 μm. If it is less than 0.1 μm, it may be difficult to handle, and if it exceeds 100 μm, mixing with zeolite may not proceed smoothly. The content of these magnetic particles in the magnetic adsorbent of the present invention is preferably 5 to 70% by mass, and more preferably 20 to 60% by mass. If the content is less than 5% by mass, the efficiency of magnetic separation decreases, which is not preferable. Moreover, when it exceeds 70 mass%, since the content rate of a zeolite will become low, harmful component adsorptivity will fall, it is not preferable.

  There is no restriction | limiting in particular as a cesium adsorption compound used for this invention, A well-known thing can be used. For example, zeolite, crystalline tetratitanic acid, smectite, insoluble ferrocyanide, ammonium phosphomolybdate, ammonium phosphotungstate, silicotitanate and the like can be mentioned. When the cesium-adsorbing compound is obtained as a powder and bound to the magnetic particles and the binder to obtain the magnetic particles of the present invention, the particle size of the cesium-adsorbing compound is preferably 0.1 to 100 μm. If it is less than 0.1 μm, handling may be difficult. If it exceeds 100 μm, mixing with the magnetic particles may not proceed smoothly. The content of these cesium-adsorbing compounds in the magnetic adsorbent of the present invention is preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass. If the content is less than 10% by mass, the adsorption efficiency of cesium decreases, which is not preferable. On the other hand, if it exceeds 80% by mass, the content of the magnetic particles is lowered, so that the efficiency of magnetic separation is lowered, which is not preferable.

  There is no restriction | limiting in particular as a hollow particle used for this invention, What has a space | gap inside can be used. There are no particular restrictions on the type of wall material separating the inside and the outside, and organic and inorganic materials can be used.

  Examples of organic materials include aromatic vinyl compounds, (meth) acrylic acid ester compounds, (meth) acrylic acid ester compounds having an amino group, (meth) acrylic acid ester compounds having an alkoxyl group, and (meth) having a cyano group Acrylic ester compound, vinyl cyanide compound, unsaturated acid, vinyl ester compound, vinyl ether compound, unsaturated amide compound, halogen-containing unsaturated compound, conjugated diene compound, non-conjugated diene compound, epoxy group-containing unsaturated compound, styrene sulfone Polymers obtained by addition polymerization of vinyl monomers such as acid, α-methylstyrene sulfonic acid and salts thereof, polyester resin, polyamide resin, polycarbonate resin, phenol resin, urea resin, melamine resin, polyurethane resin, epoxy resin, cyclic Poliophy It can be mentioned resins, synthetic polysaccharides. Among these, monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, styrene, methyl acrylate, ethyl acrylate, butyl acrylate, acrylonitrile, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylonitrile are the main components. A homopolymer of 2 or more and a copolymer comprising two or more monomers are preferably used. Furthermore, among these, a styrene-acrylic copolymer is more preferable because of its stable particle size, dispersibility, and solid content concentration.

  The organic hollow particles are commercially available, for example, as Dow Chemical's Ropaque series and JSR Corporation as SX series. Specifically, Ropaque HP-91 (average particle size 1.0 μm, hollow ratio 51%), Ropaque OP-62 (0.4 μm, 33%), Ropaque OP-84J (0.55 μm, 20). %), Ropaque HP-1055 (1.0 μm, 50%), SX8782 (A) (1.1 μm, 55%), SX8782 (D) (1.0 μm, 51%), SX866 ( B) (0.3 μm, 30%).

  Examples of inorganic materials include silica, alumina, titanium oxide, calcium carbonate, zinc oxide, zinc sulfide and the like. A template method is known as a method for synthesizing the inorganic hollow particles. In this method, organic / inorganic particles are used as a template for a hollow structure, and core / shell particles (coated particles) are formed by precipitating a material that selectively becomes a shell of particles around the core particles by surface charge. Get. After the core / shell particles are filtered and dried, the core particles are removed to form inorganic hollow particles. Polystyrene is often used as the organic template particles, but any template that can be removed can be used. The core particles can be removed by the thermal decomposition method (combustion method) and chemical decomposition method (dissolution with an organic solvent). Removal). As inorganic template particles, Japanese Patent Application Laid-Open No. 2005-263550 discloses a method using calcium carbonate particles. By using an inorganic acid such as hydrochloric acid, core particles can be removed to prepare hollow particles.

  The hollow ratio of the hollow particles in the present invention (the volume ratio of the space part to the total volume of the resin part and the space part of the particle) is not particularly limited, and preferably 20 to 90%, more preferably 40 to 90% of the particles are used. can do.

  The particle size of the hollow particles in the present invention is not particularly limited, but is preferably 0.1 to 100 μm. If it is less than 0.1 μm, handling is difficult, and in order to give buoyancy to the magnetic adsorption material, it is necessary to use a large amount. In that case, the cesium adsorption ability is lowered, and separation from the solution by magnetism becomes difficult. Become. On the other hand, when the thickness exceeds 100 μm, breakage of hollow particles occurs during the production of the magnetic adsorbent, and the magnetic adsorbent having the desired buoyancy cannot be obtained.

  The content of these hollow particles in the magnetic adsorbent of the present invention is preferably 10 to 80% by mass, and more preferably 20 to 70% by mass. If the content is less than 10% by mass, the adsorption efficiency of cesium decreases, which is not preferable. On the other hand, if it exceeds 80% by mass, the content of the magnetic particles is lowered, so that the efficiency of magnetic separation is lowered, which is not preferable.

  There is no restriction | limiting in particular in the kind of binder used for this invention, The binder known in the field of granulation and a shaping | molding can be used. Specifically, for example, inorganic binders such as cement, gypsum, water glass and minerals, natural organic water-soluble binders such as starch, casein, gelatin and chitosan, polyvinyl alcohol resins (polyvinyl alcohol, cation-modified polyvinyl alcohol, anions) Modified polyvinyl alcohol, acetoacetyl modified polyvinyl alcohol, diacetone modified polyvinyl alcohol, silanol modified polyvinyl alcohol, polyvinyl acetal, etc.), cellulosic resins (methylcellulose, ethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose) Etc.), polyacrylic acid resin, polyacrylamide, polyvinyl pyrone Synthetic organic water-soluble binders such as dong, polyethylene oxide and polypropylene oxide, polyacrylate resin, polyamide resin, polyvinyl acetate resin, urea resin, epoxy resin, polyurethane resin, poly (styrene / butadiene) resin, poly (ethylene / Vinyl acetate) Resins, binders in which water-insoluble resins such as nitrile rubber are dispersed in water, and the like can be mentioned. Only one of these can be used alone, or two or more can be used in combination. You can also Furthermore, modified resin emulsions obtained by modifying these resins can also be used.

  In order to improve the water resistance of these binders, there are a method of using a crosslinking agent and a method of promoting crystallization by heating. There is no restriction | limiting in particular as a crosslinking agent, A well-known thing can be used. Examples include oxazoline polymers, water-soluble epoxy compounds, water-soluble melamine compounds, water-dispersed blocked isocyanates, water-based aziridine compounds, titanium compounds, zirconium compounds, silicon compounds, aldehyde compounds, and boric acid.

  The content of the binder in the magnetic adsorbent of the present invention is preferably 1 to 50% by mass, and particularly preferably 1 to 20% by mass. When the content is less than 1% by mass, the physical strength of the magnetic adsorbent is lowered, and the magnetic particles and the cesium adsorbing compound are easily separated. When the content rate exceeds 50% by mass, the adsorption efficiency of harmful components decreases, which is not preferable.

  As a method for producing the magnetic adsorbent of the present invention, there is a method in which magnetic particles, a cesium adsorbing compound, and hollow particles are mixed with a binder, dried, and pulverized. As another method, there is a method in which magnetic particles, a cesium-adsorbing compound, and hollow particles are bulk polymerized together with a monomer, followed by drying and pulverization, but the former method is advantageous in terms of ease of control of the manufacturing process and cost It is. There is no restriction | limiting in particular about the apparatus used in each process.

  As a method for contacting the solution containing harmful components with the magnetic adsorbent of the present invention, batch treatment in which the magnetic adsorbent is added to the solution and stirred can be carried out with a simple apparatus. Examples of the stirring method include a method of stirring with a stirring blade and a method of aeration such as aeration. The contact time between the solution containing harmful components and the magnetic adsorbent is preferably 10 minutes to 2 hours. If the contact time is shorter than 10 minutes, adsorption of harmful components may be insufficient. Even if the contact time is longer than 2 hours, the adsorption has already reached equilibrium, which is not preferable in terms of work efficiency, and long-time stirring may adversely affect the mechanical strength of the magnetic adsorbent.

  There is no limit to the amount of the magnetic adsorbent of the present invention added to a solution containing harmful components, and the amount of harmful components removed to the target level may be determined experimentally according to the concentration of harmful components. .

  The magnetic adsorbent adsorbing the harmful components is collected in a short time by a permanent magnet, an electromagnet, and a superconducting magnet, and separated from the solution from which the harmful components have been removed. There are no particular restrictions on the magnetic separation device used.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples. In addition, the percentage in an Example is a mass reference | standard unless there is particular notice.

<Synthesis of magnetic adsorbent 1>
Iron trioxide (10 g) having an average particle diameter of 2 μm, zeolite (Shintohoku Chemical Co., Ltd .; Zeophyl CP; 10 g), styrene / acryl hollow particles (Dow Chemical Co .; Ropaque HP-1055; solid content concentration 27. 5%, average particle size = 1.0 μm; 50 g), polyacrylate ester emulsion (Nisshin Chemical Industry Co., Ltd .; Vini Blanc 2680; solid content 30%; 23.3 g), kneaded in a mortar for 30 minutes, And dried at 80 ° C. for 3 hours. The obtained dried solid was pulverized with a mini blender to obtain 38 g of magnetic adsorbent 1.

<Synthesis of comparative adsorbent 1>
Ferric trioxide (10 g) having an average particle diameter of 2 μm, zeolite (Shintohoku Chemical Industry Co., Ltd .; Zeophyl CP; 10 g), polyacrylate ester emulsion (Nisshin Chemical Industry Co., Ltd .; Vini Blanc 2680; solid content 30 %; 13.3 g) were mixed at the same time, kneaded in a mortar, spread on a petri dish and dried at 80 ° C. for 3 hours. The obtained dried solid was pulverized with a mini blender to obtain 20 g of Comparative Adsorbent 1.

<Synthesis of comparative adsorbent 2>
An iron trioxide (10 g) having an average particle diameter of 2 μm and zeolite (New Tohoku Chemical Industry Co., Ltd .; Zeophyl CP; 10 g) were mixed, and 2 g of Portland cement was further added and mixed. This mixture was granulated while adding water to a rolling granulator, and sieved with a sieve having an opening of 2 mm. This sieving was dried to obtain 11 g of comparative adsorbent 2.

Example 1
6.33 mg of cesium chloride was dissolved in 500 ml of distilled water to prepare an aqueous solution having a cesium ion concentration of 0.001% (10 ppm). After adding 20 mg of the magnetic adsorbent 1 to 50 ml of this solution and stirring for 10 seconds and allowing to stand for 30 minutes, a part of the aqueous phase was taken out and the concentration of cesium ions remaining in the aqueous phase was determined by ICP-MS. It was found that 88% of cesium ions were removed. After the sample was taken out, the magnet was inserted into the container for 30 seconds while further stirring, and then the magnet was taken out, stirring was stopped, and the inside of the container was observed. It was confirmed that there was no decomposition.

Comparative Example 1
The same operation as in Example 1 was conducted except that 12 mg of the comparative adsorbent 1 was added instead of 20 mg of the magnetic adsorbent 1. The residual cesium ion concentration was 4.0 ppm, and the removal rate was 60%. Moreover, when the same operation as Example 1 was performed about the remainder which took out the sample, the solid substance was observed by the bottom of the container. After sampling and drying, 3 mg component was confirmed.

Comparative Example 2
The same operation as in Example 1 was conducted except that 12 mg of the comparative adsorbent 2 was added instead of adding 20 mg of the magnetic adsorbent 1. The residual cesium ion concentration was 5.6 ppm, and the removal rate was 44%. Moreover, when the same operation as Example 1 was performed about the remainder which took out the sample, the solid substance was observed by the bottom of the container. After sampling and drying, 5 mg component was confirmed.

  From the results of Example 1 and Comparative Examples 1 and 2, it was shown that harmful components can be efficiently separated according to the present invention. It was also confirmed that the magnetic adsorbent can be efficiently recovered by a simple method.

  According to the present invention, a magnetic adsorbent is added to a harmful component-containing solution, and after a simple stirring operation, the magnetic adsorbent is removed by magnetic separation, thereby removing harmful components in a short time and magnetic separation by magnetic separation. Can be easily recovered and separated. Even if the harmful component-containing solution contains sludge, soil, incinerated ash, etc., it hardly affects magnetic separation, and thus the present invention is considered effective for purification of the harmful component-containing solution containing these.

The magnetic particles used in the present invention are not particularly limited, and any material exhibiting magnetism can be used. For example, powders of metals such as iron, nickel and cobalt or powders of magnetic alloys based on these metals, powders of metal oxide magnetic materials such as iron trioxide, iron sesquioxide, cobalt-added iron oxide, barium ferrite and strontium ferrite Is mentioned. The particle size of the magnetic particles is preferably 0.1 to 100 μm. If it is less than 0.1 μm, handling may be difficult. If it exceeds 100 μm, mixing with the cesium-adsorbing compound may not proceed smoothly. The content of these magnetic particles in the magnetic adsorbent of the present invention is preferably 5 to 70% by mass, and more preferably 20 to 60% by mass. If the content is less than 5% by mass, the efficiency of magnetic separation decreases, which is not preferable. Moreover, when it exceeds 70 mass%, since the content rate of a cesium adsorptive compound becomes low and harmful component adsorptivity falls, it is not preferable.

The content of these hollow particles in the magnetic adsorbent of the present invention is preferably 10 to 80% by mass, and more preferably 20 to 70% by mass. When the content is below 10 wt% not object of buoyancy is obtained, in the cesium adsorption treatment, cesium adsorption efficiency at low stirring force is reduced, so shall be subject to high stirring force is not preferable. On the other hand, if it exceeds 80% by mass, the content of the magnetic particles is lowered, so that the efficiency of magnetic separation is lowered.

Claims (1)

A magnetic adsorbent in which magnetic particles, a cesium adsorbing compound, and hollow particles are bound by a binder.