Method for producing polyphenol component-containing fired zeolite, and method for using the same

Abstract

To provide a method for producing a polyphenol component-containing fired zeolite which can efficiently reduce radioactive substance concentration in contaminated water under an ordinary temperature, and an apparatus for reducing radioactive substance concentration such as HTO.SOLUTION: A production method adds and mixes an organic matter obtained by grinding astringent persimmon much containing a much polyphenol component into potter's clay such as lime feldspar obtained by crushing zeolite, fires the mixture in a firing pot adjusted to 350°C to 450°C and obtains a polyphenol component-containing fired zeolite. An apparatus for reducing a radioactive substance concentration such as HTO stores hard zeolite of the zeolite and clinoptilolite in a filtration tank, brings radioactive substance-containing contaminated water such as HTO into contact with the stored zeolite, makes the zeolite absorb the radioactive substance such as HTO in the radioactive substance-containing contaminated water such as HTO, and discharges the radioactive substance-containing contaminated water such as HTO which is not made to absorb the radioactive substance such as HTO as radioactive substance-containing contaminated water such as HTO having reduced radioactive substance concentration such as HTO.SELECTED DRAWING: Figure 1

Description

Detailed Description of the Invention [Technical field]

[0001] The present invention relates to a method for producing a calcined zeolite containing a polyphenol component, and a method for treating contaminated water containing radioactive substances such as HTO by using the calcined zeolite containing a polyphenol component. [Background technology]

[0002] The contaminated water containing tritium and other radioactive materials generated at the Fukushima Daiichi Nuclear Power Plant has an extremely dilute concentration of just a few nanograms per liter when converted into tritium mass concentration, and it is said to be extremely difficult to efficiently separate and recover such a small amount of tritium from a large amount of water at room temperature by separating the tritium isotopes from the water molecules.

[0003] Meanwhile, research has been published that focuses on the "capillary pseudo-drainage" phenomenon, in which a liquid rises up a tube when a "porous body" with a structure with many holes like charcoal or sponge and a thin tube like a straw are immersed in the liquid, and aims to apply this phenomenon to decontamination technology (see Patent Document 1). Also, a separation method using zeolite for tritiated water and heavy water, in which heavy water or tritiated water is contacted with a gas, has been published (see Patent Document 2). Also, a method for separating and concentrating tritiated water from tritium-containing water using zeolite has been introduced (see Non-Patent Document 1). [Prior art documents]

[0004] [Patent Document 1] JP 2020-071171 A [Patent Document 2] Japanese Patent Application Publication No. 10-128072 [Non-Patent Document 1] Separation of tritium using zeolite. Hydrogen Isotope Chemistry Center, University of Toyama Summary of the Invention [Problem to be solved by the invention]

[0005] The HTO contained in contaminated water containing radioactive materials such as HTO exists in the form of water, making it difficult to separate. There are currently plans to dilute the HTO with water and release it into the ocean, but no definitive solution has yet been found.

[0006] The inventors focused on the characteristics of strong adsorption and aggregation of metals, proteins, etc. through a chemical reaction based on the hydroxyl group reaction of tannic acid, such as that in persimmon tannin, which is rich in polyphenols, and the principle of ion exchange of radioactive substances with zeolite, in order to develop an adsorbent for radioactive substances such as HTO.

[0007] Persimmon tannins, which have the above-mentioned characteristics, are water-soluble and therefore need to be insoluble in order to be used as an adsorbent. Therefore, applying the conventional method of carbonizing and powdering unripe persimmons in an 800°C kiln to treat contaminated water containing radioactive materials, which has completely different treatment conditions and adsorbent materials, would require the collection of large amounts of persimmons and the expense of carbonizing them.

[0008] As a method for dealing with this issue, we aimed to manufacture calcined zeolite containing polyphenol components by mixing porcelain clay containing zeolite powder such as calcine feldspar with organic matter made by crushing astringent persimmons, which contain a lot of polyphenol components, and to provide a treatment device for contaminated water containing radioactive substances such as HTO using a low-cost, simple device. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the method for producing calcined zeolite containing polyphenol components is carried out by using a mixture of 70% (weight) of porcelain clay of zeolite powder such as calcium feldspar and 30% (weight) of organic matter obtained by crushing persimmons, which contains a lot of polyphenol components, as a raw material, forming and extruding the mixture into granules using an extruder with a hole size of 5 mm to 8 mm, drying the mixture, and calcining the mixture in a calcination kiln at a temperature adjusted to 100°C to 800°C, preferably 300°C to 450°C, to carbonize and hollow out the organic matter in the persimmons. This results in the production of the calcined zeolite containing polyphenol components for treating contaminated water containing radioactive substances such as HTO, which has been the subject of the present invention.

[0010] The method for treating contaminated water containing radioactive substances such as HTO of the present invention using calcined zeolite containing polyphenol components comprises a filtration tank 4 of an apparatus for reducing the concentration of radioactive substances, and in the filtration tank 4, the calcined zeolite containing polyphenol components 6 for treating contaminated water containing radioactive substances such as HTO as described in the previous section and hard zeolite such as clinoptiolite as an adsorption aid for radioactive substances are contained in a ratio of 1:1.

[0011] The polyphenol component-containing calcined zeolite and the hard zeolite of clinoptiolite are brought into contact with contaminated water containing radioactive substances such as HTO, and the radioactive substances such as HTO in the contaminated water containing radioactive substances such as HTO are absorbed by the polyphenol component-containing calcined zeolite and the hard zeolite of clinoptiolite.

[0012] This device is characterized by discharging contaminated water containing radioactive materials such as HTO, in which the above-mentioned method was unable to absorb radioactive materials such as HTO, as contaminated water containing radioactive materials such as HTO with a reduced concentration of radioactive materials such as HTO.

[0013] The device for reducing the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO and discharging it is configured with a discharge pipe that utilizes the siphon principle to expose the hard zeolite, i.e., calcined zeolite containing polyphenol components and clinoptiolite, in the contaminated water containing radioactive substances in the lower part of the filtration tank, and promotes the intake of oxygen and the transfer of radioactive substances between components, and automatically intermittently discharges water containing radioactive substances such as HTO with reduced concentrations. Effect of the Invention

[0014] The present invention is characterized in that contaminated water containing radioactive substances such as HTO is brought into contact with hard zeolites, i.e., calcined zeolite containing polyphenol components and clinoptiolite, so that the radioactive substances such as HTO are absorbed by the calcined zeolite containing polyphenol components and the hard zeolites, i.e., clinoptiolite, and the contaminated water containing radioactive substances such as HTO that could not be absorbed is discharged as contaminated water with a reduced concentration of radioactive substances such as HTO.

[0015] By combining the above-mentioned devices in a multi-stage configuration, it is possible to increase the rate at which the concentration of radioactive substances such as HTO can be reduced, making it possible to discharge treated water whose concentration in wastewater is below the national regulatory standards for environmental release. This has the greatest advantage of making it possible to eliminate tanks for contaminated water containing radioactive substances such as HTO. Moreover, since this system is inexpensive and can be managed continuously, it is expected that the need for it will continue to increase in the future. [Brief description of the drawings]

[0016] [Figure 1] This is a manufacturing process diagram of calcined zeolite containing polyphenol components, which reduces the concentration of radioactive substances such as HTO. [Diagram 2] This is a cross-sectional diagram of an apparatus for reducing the concentration of radioactive materials such as HTO in contaminated water containing radioactive materials such as HTO. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The raw materials of the embodiment of the present invention will be outlined below. Pottery clay, such as calcine feldspar, which is the main raw material for calcined zeolite containing polyphenol components, is a powder of porous zeolite, an aluminosilicate mineral with many cavities in its crystals. It has the chemical property of having a strong adsorption power when it comes into contact with moisture, and a base exchange ability that allows it to exchange ions when it comes into contact with different cations in an aqueous solution.

[0018] If sagging or crumbling occurs during the formation of the polyphenol component-containing calcined zeolite, a suitable amount of powder of any of light earthenware clay, coarse earthenware clay, white cloud earthenware clay or the like can be added as a binder.

[0019] On the other hand, polyphenols are components of the foods we eat every day, and scientific elucidation of their mechanism is progressing in the field of agricultural chemistry. Chemical reactions based on the hydroxyl group reaction of polyphenols that are easily oxidized, such as tannic acid, exhibit high adsorption properties to the surfaces of various materials and the ability to convert various metal ions, and therefore have been adopted for the purpose of reducing the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO.

[0020] Figure 1 shows the manufacturing process for calcined zeolite containing polyphenols, which reduces the concentration of radioactive substances such as HTO in contaminated water. Zeolite is crushed into 70% clay such as calcite, and mixed with 30% organic matter made from crushed persimmons, which contain a lot of polyphenols.

[0012] The above-mentioned mixed calcined zeolite raw material containing polyphenol components is fed into a hopper of an extruder, and the extruder having a hole diameter of 5 mm to 8 mm is driven to extrude and mold the material into granules, which are then dried.

[0013] The dried extrusion-molded product is calcined in a calciner adjusted to a temperature range of 100°C to 800°C, preferably 300°C to 450°C, to obtain calcined zeolite containing polyphenol components, which is the object of the present application, and which reduces the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO, by combining the ion exchange ability of zeolite and zeolite powder and the properties of chemical reactions based on the hydroxyl group reaction of polyphenols.

[0014] The above-mentioned calcined zeolite containing polyphenol components is made by mixing zeolite powder with an organic material made by crushing astringent persimmons, which contain a large amount of polyphenol components. However, a porous body obtained by a known method of soaking granular zeolite in persimmon tannin liquid, removing it, drying it, and calcining it in a calcination pot at a temperature range of 300°C to 450°C is also included and used as the calcined zeolite containing polyphenol components of the present invention that adsorbs radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO.

[0015] The calcined zeolite containing polyphenol components of the present invention, which adsorbs radioactive substances such as HTO, utilizes the inherent properties of zeolite and polyphenols, such as the base exchange ability of zeolite and zeolite powder to exchange ions, the ability to adsorb metal ions through chemical reactions based on the reaction of the hydroxyl groups of polyphenols, and the susceptibility of polyphenols, which are antioxidants, to oxidation and the reduction and adsorption ability of precious metals in the inter-component reactions accompanying the oxidation reaction.

[0016] The combination of the above-mentioned properties of calcined zeolite containing polyphenols that adsorb radioactive substances such as HTO means that its chemical structure has changed and it has latent capabilities; however, since calcined zeolite containing polyphenols is a combination of natural substances, information on its chemical principles will have to wait until the future.

[0017] Next, the device for reducing the concentration of radioactive materials in contaminated water containing radioactive materials shown in FIG. 2 will be described.

[0018] The first device for reducing the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO comprises a perforated partition plate 5 laid at the bottom of the filtration tank 4, and a mixture of zeolite powder and crushed astringent persimmon, or a hard zeolite such as clinoptiolite, mixed in a 1:1 ratio, and a polyphenol-containing calcined zeolite 6 stored in the filtration tank. For the purpose of facilitating replacement of the polyphenol-containing calcined zeolite, the polyphenol-containing calcined zeolite may be stored in a mesh bag in the filtration tank.

[0019] 2. In the same manner as above, in an apparatus for reducing the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO, the calcined zeolite containing polyphenol components obtained by soaking the zeolite in persimmon tannin liquid and the hard zeolite clinoptiolite alone or in a 1:1 mixture are placed in the apparatus for reducing the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO, and the calcined zeolite containing polyphenol components of 6. For the purpose of facilitating the replacement of the calcined zeolite containing polyphenol components, the polyphenol components may be placed in a mesh bag and stored in the filtration tank.

[0020] Contaminated water containing radioactive materials such as HTO is depressurized from a storage tank for contaminated water and injected into the filtration tank at 4 either directly or via pump 1, with the supply amount adjusted using the water supply adjustment valve at 3 in the water supply pipe at 2.

[0021] The contaminated water containing radioactive substances such as HTO injected into the filtration tank 4 comes into contact with the calcined zeolite containing polyphenol components 6 and the hard zeolite of clinoptiolite in the filtration tank 4, and the radioactive substances such as HTO in the contaminated water containing radioactive substances such as HTO are absorbed by the calcined zeolite containing polyphenol components and the hard zeolite of clinoptiolite.

[0022] In the filtration tank 4, the contaminated water containing radioactive substances such as HTO, whose concentrations have been reduced and which could not be absorbed by the calcined zeolite containing polyphenol components 6 and the hard zeolite of clinoptilolite, is automatically discharged intermittently from the siphon-type water discharge pipe 7 at the bottom of the filtration tank 4 by adjusting the water supply amount using the water supply amount adjustment valve 3.

[0023] The device of the present invention for reducing the concentration of radioactive substances such as HTO in contaminated water containing radioactive substances such as HTO, can reduce the concentration of radioactive substances such as HTO in contaminated water by physical processing without relying on petroleum energy, depending on the installation conditions, such as by reducing the pressure of contaminated water from a tank for contaminated water containing radioactive substances such as HTO.

[0024] It is also envisaged that the polyphenol component-containing calcined zeolite and the hard zeolite such as clinoptiolite into which radioactive substances such as HTO have been absorbed according to the present invention may be used to recover and store radioactive substances such as HTO by electrical or heat treatment, and that the polyphenol component-containing calcined zeolite and the hard zeolite such as clinoptiolite into which radioactive substances such as HTO have been absorbed may be recovered, enclosed in concrete, coated with asphalt and buried in the ground.

[0025] In experiments on the adsorption of radioactive substances such as HTO in contaminated water by calcined zeolite containing polyphenol components, since it is difficult to conduct experiments using actual radioactive elements, the adsorption rate of strontium in an aqueous solution of strontium chloride was evaluated.

[0006] A 0.10 mmol / L aqueous solution of strontium chloride was prepared, and 100 g of the calcined zeolite containing polyphenol components was weighed out in a separate container, and 100 ml of the aqueous solution of strontium chloride was poured into it and allowed to stand for one day and night.

[0007] The polyphenol-containing calcined zeolite was removed and the supernatant was measured by atomic absorption spectroscopy. The metal ion concentration was calculated from a calibration curve of a solution of known concentration, and the absorption rate of the polyphenol-containing calcined zeolite was calculated. It was confirmed that it was possible to adsorb more than 80% of strontium. [Explanation of symbols] 1. Water supply pump 2. Water pipe 3. Water supply amount adjustment valve 4. Filter tank 5, Perforated partition plate 6, Polyphenol-containing calcined zeolite 7, Water discharge pipe

Claims

1. This method for producing calcined zeolite containing polyphenol components comprises mixing 70% of pulverized zeolite-based pottery clay, such as calcite feldspar, with 30% of organic matter made by crushing astringent persimmons containing a large amount of polyphenol components, and carbonizing and hollowing the mixture in a calcination oven adjusted to 350 to 450°C.

2. This method involves immersing granular zeolite in a known persimmon tannin liquid, removing it, drying it, and heating it at 350°C to 450°C to obtain calcined zeolite containing polyphenol components.

3. A method for producing a calcined zeolite containing polyphenol components and an apparatus for reducing the concentration of radioactive substances such as HTO, comprising: placing the calcined zeolite containing polyphenol components and the hard zeolite of clinoptiolite according to claim 1 and claim 2 in a filtration tank; contacting the calcined zeolite with contaminated water containing radioactive substances such as HTO; absorbing the radioactive substances such as HTO in the contaminated water containing radioactive substances such as HTO into the calcined zeolite containing polyphenol components and the hard zeolite of clinoptiolite; and intermittently discharging the contaminated water containing radioactive substances such as HTO in which the radioactive substances such as HTO could not be absorbed as contaminated water containing radioactive substances such as HTO with a reduced concentration of the radioactive substances such as HTO.

4. A method for producing a calcined zeolite containing polyphenol components and an apparatus for reducing the concentration of radioactive substances such as HTO, comprising mixing the calcined zeolite containing polyphenol components and the hard zeolite clinoptiolite in a 1:1 ratio, storing the mixture in a filtration tank, contacting the mixture with contaminated water containing radioactive substances such as HTO, causing the radioactive substances in the contaminated water containing radioactive substances such as HTO to be absorbed by a hybrid of the calcined zeolite containing polyphenol components and the hard zeolite clinoptiolite, and discharging the contaminated water containing radioactive substances such as HTO in which the radioactive substances such as HTO could not be absorbed as contaminated water containing radioactive substances such as HTO with a reduced concentration of the radioactive substances such as HTO.

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