JP5713948B2 - Iodine adsorbent - Google Patents

Description

  Embodiments of the present invention relate to an iodine adsorbent.

  Effective use of water resources is required due to industrial development and population growth. For that purpose, the reuse of wastewater is very important. In order to achieve these, it is necessary to purify the water, ie to separate other substances from the water. Various methods are known as methods for separating other substances from the liquid, such as membrane separation, centrifugation, activated carbon adsorption, ozone treatment, removal of suspended substances by aggregation, and the like. By such a method, chemical substances having a great influence on the environment such as iodine and nitrogen contained in water can be removed, and oils and clays dispersed in water can be removed.

On the other hand, in recent years, iodine recovery and removal techniques have attracted attention. Iodine is used in a wide range and is used in a wide range of fields such as chemical fibers and heat stabilizers in addition to the medical field such as disinfectants. Although iodine has many isotopes, iodine ¹³¹ I is a radioactive isotope and is produced as a daughter nuclide when uranium ²³⁵ U undergoes fission.

  Therefore, the radioactive iodine released in large quantities in the event of an accident at a nuclear power plant may also contain the above-mentioned radioactive iodine. By mixing such radioactive iodine into the atmosphere or wastewater, May be adversely affected. Therefore, when radioactive iodine is mixed in the atmosphere or waste water, it is a problem to remove the radioactive iodine.

As a method for removing iodine, for example, it has been reported that a material having a structure in which cyclodextrin is bound to a carrier adsorbs iodine. This high molecular iodine bactericidal properties, i.e. iodine chemical forms of I ₂ is stabilized by causing subsumed within cyclodextrin, a study for the purpose of being able to use the bactericidal long, polyiodide anion (I ₃ ⁻ ) is generated and incorporated into the cyclodextrin.

  The raw material of cyclodextrin is mainly corn-derived starch, which is produced by hydrolyzing amylose contained therein using an enzyme or the like, and has very high safety.

However, iodine is stably present in the state of iodide anion (I ₃ ⁻ ) or iodate ion (IO ₃ ⁻ ) in water, and is stable in the state of iodine ion (I ⁻ ), particularly in seawater. It is known. The iodine adsorbent described above can adsorb iodide anions (I ₃ ⁻ ), but there is no report on the adsorptivity of iodine ions (I ⁻ ).

J. Appl. Polym. Sci. 2001, 82, 2414-2421.

An object of the present invention is to provide an adsorbent having a novel structure that is particularly excellent in adsorptivity of iodine ions (I ⁻ ).

The iodine adsorbent of the embodiment is encapsulated in a carrier having an amino group, triazino-β-cyclodextrin or a derivative thereof bound to the carrier via the amino group, and the triazino-β-cyclodextrin or a derivative thereof. And at least one of chlorine bonded to the surface of the triazino-β-cyclodextrin or a derivative thereof.

  In another embodiment, the iodine adsorbent was obtained by reacting a carrier with monochlorotriazino-β-cyclodextrin or a derivative thereof and binding the triazino-β-cyclodextrin or a derivative thereof to the carrier. Is.

Chlorine ions dissolved from the iodine adsorbent according to the embodiment (Cl ^-) and the amount of iodine ion by iodine adsorbent ^- is a graph showing the relationship between adsorption capacity of (I). It is a key map of an iodine adsorption system in an embodiment. It is an infrared spectroscopy spectrum figure in an Example. It is an infrared spectroscopy spectrum figure in an Example. It is an infrared spectroscopy spectrum figure in an Example.

(Iodine adsorbent)
The iodine adsorbent of the embodiment has a carrier and triazino-β-cyclodextrin or a derivative thereof bound to the carrier. Specifically, the carrier and cyclodextrin are bonded via a triazine ring.

  The derivative referred to here is a compound obtained by substituting carbon other than the chlorine-substituted carbon of the triazino ring with another substituent in the chlorine-substituted triazino ring constituting triazino-β-cyclodextrin. That means. Examples of such a substituent include an alkoxy group.

  The carrier itself has sufficient strength to self-hold a predetermined form in water, and is strong enough to carry triazino-β-cyclodextrin or a derivative thereof for practical use. . This carrier is preferably such that triazino-β-cyclodextrin or a derivative thereof can be bound by the production method described below. Furthermore, it is preferable that the carrier has many amino groups on the surface, and triazino-β-cyclodextrin or a derivative thereof is bound to the carrier via this amino group. Specifically, examples of the carrier include chitosan and polymer particles whose surface is modified with an amino group.

 The carrier may be an acrylic resin. The acrylic resin itself has sufficient strength, and can provide strength that can be practically used as an iodine adsorbent and has an ester bond site. An amino group can be easily provided by reaction with a secondary amine, and this amino group easily reacts with triazino-β-cyclodextrin.

 The iodine adsorbent in the present embodiment preferably has an average particle size of 100 μm to 2 mm. When the average particle size of the carrier is 100 μm or more and 2 mm or less, for example, when iodine adsorption is performed, both the high packing rate of the iodine adsorbent into the column and the ease of water flow can be achieved. When the average particle size is less than 100 μm, the filling rate of the iodine adsorbent into the column becomes too high, and the ratio of voids decreases, so that it becomes difficult to pass water. On the other hand, when the average particle diameter exceeds 2 mm, the packing rate of the iodine adsorbent into the column becomes too low and voids increase, making it easier to pass water, but the contact area between the iodine adsorbent and the waste water containing iodine. Decreases, the iodine adsorption rate by the iodine adsorbent decreases.

 The iodine adsorbent may have an average particle size in the state of an aggregate in which primary particles are aggregated. A preferable average particle diameter is 150 μm or more and 1.5 mm or less, and more preferably 150 μm or more and 500 μm or less.

 Note that the iodine adsorbent of the present embodiment can adjust the size of the iodine adsorbent itself only by changing the size of the carrier, and in order to obtain an iodine adsorbent that is easy to handle, It can be seen that the size should be set to a predetermined size. That is, an iodine adsorbent that is easy to handle can be obtained without performing operations such as granulation. Further, since it is not necessary to perform granulation or the like, the manufacturing process necessary for obtaining an iodine adsorbent that is easy to handle can be simplified, and the cost can be reduced.

  The average particle diameter can be measured by a sieving method. Specifically, according to JISZ8901-2006 “Test Powder and Test Particles”, it can be measured by sieving using a plurality of sieves having an opening of 150 μm to 500 μm.

  The iodine adsorbent of this embodiment has at least one of chlorine encapsulated in triazino-β-cyclodextrin or a derivative thereof and chlorine bonded to the surface of the triazino-β-cyclodextrin or a derivative thereof. In addition, although the content of chlorine in triazino-β-cyclodextrin or its derivatives is not clear at present, when chlorine is included, as shown in the formula (1), chlorine is included in cyclodextrin. I believe that. On the other hand, when it has chlorine on the surface, it is considered that it is ionically bonded to nitrogen of the triazino ring as shown in the formula (2).

  In the formulas (1) and (2), as described below, after the carrier is graft-modified with an amino group, the triazino-β-cyclodextrin is bound via the amino group. Yes.

In the formulas (1) and (2), the triazine ring of triazino-β-cyclodextrin is described as a derivative substituted with β-cyclodextrin and a sodium salt of a phenolic hydroxyl group. This is due to the use of the derivative from Cyclochem Co., Ltd.

Iodine adsorption agent in the present embodiment, as described above, at least one of chlorine bound to triazino -β- cyclodextrin or encapsulated chlorine and the triazino -β- cyclodextrin or the surface of a derivative thereof in that the induction body It is considered that the iodine ions (I ⁻ ) are adsorbed by ion exchange with iodine ions (I ⁻ ) in the liquid to be treated such as waste water.

FIG. 1 shows the amount of chlorine ions (Cl ⁻ ) eluted from the iodine adsorbent and iodine ions (I ⁻ ) in the ion exchange water when the iodine adsorbent of the present embodiment is immersed in the ion exchange water. It is a graph which shows the relationship with the adsorption | suction ability of the iodine ion (I < ^- >) by the said iodine adsorbent in case containing. As is clear from FIG. 1, as the amount of chlorine ions (Cl ⁻ ) eluted in the ion exchange water increases, the iodine ion (I ⁻ ) adsorption capacity when iodine ions (I ⁻ ) are contained in the ion exchange water. Has increased. From this, it can be inferred that iodine ions (I ⁻ ) in the liquid to be treated are adsorbed by ion exchange with chlorine ions (Cl ⁻ ) of the iodine adsorbent.

The amount of chlorine ions (Cl ⁻ ) and the amount of iodine ions (I ⁻ ) were detected by ion chromatography.

  The iodine adsorbent of the present embodiment is preferably obtained by graft-modifying a carrier with an amino group, and then reacting the carrier with monochlorotriazino-β-cyclodextrin or a derivative thereof via the amino group to produce triazino-β- It is preferred to bind cyclodextrin.

  As explained in the following production method, the carbon substituted with chlorine by adding to chlorotriazino-β-cyclodextrin or its derivative (triazino ring thereof) lacks electrons due to the electron-attracting properties of chlorine. It is in a state. On the other hand, the amino group that modifies the carrier functions as a so-called nucleophile, and thus nucleophilically attacks the carbon. As a result, the chlorine added to monochlorotriazino-β-cyclodextrin or its derivative (triazino ring thereof) is easily removed to form hydrogen chloride, and the protons in this hydrogen chloride are replaced by the nitrogen atom of the triazino ring. As it is donated, it is thought that the remaining chlorine (ions) is included inside the cyclodextrin or bound to the outer polar part, or bound to the nitrogen of the triazino ring. That is, chlorine can be easily bonded to at least one of the inside and the surface of triazino-β-cyclodextrin or a derivative thereof.

(Production method of iodine adsorbent)
Next, the manufacturing method of the iodine adsorbent of this embodiment is demonstrated. However, the production method described below is an example, and is not particularly limited as long as the iodine adsorbent of the present embodiment is obtained.

  First, the carrier is reacted with monochlorotriazino-β-cyclodextrin or a derivative thereof. When the carrier is graft-modified with an amino group, nucleophilic attack on the carbon substituted by the chlorine to which the amino group is attached to monochlorotriazino-β-cyclodextrin or its derivative (triazino ring) As a result, chlorine easily dissociates to form hydrogen chloride, and protons in this hydrogen chloride are donated to the nitrogen atom of the triazino ring, so that the remaining chlorine (ions) is contained inside or outside the cyclodextrin. It is thought that it binds to the polar part of the ring or a nitrogen bond of the triazino ring. That is, it becomes possible to easily have chlorine inside and / or on the surface of triazino-β-cyclodextrin or a derivative thereof.

In addition, (3) Formula showed schematically the process until hydrogen chloride was produced | generated among the said manufacturing methods.

(Iodine adsorption system and method of using iodine adsorbent)
Next, an adsorption system using the above-described iodine adsorbent and a method for using the adsorption system will be described.

FIG. 2 is a diagram showing a schematic configuration of an apparatus used for iodine adsorption in the present embodiment.
As shown in FIG. 2, in this apparatus, the water treatment columns T1 and T2 filled with the iodine adsorbent described above are arranged in parallel, and the contact efficiency is located outside the water treatment columns T1 and T2. Promotion means X1 and X2 are provided. The contact efficiency promoting means X1 and X2 can be a mechanical stirrer or a non-contact magnetic stirrer, but they are not essential components and may be omitted.

  The water treatment columns T1 and T2 are connected to a drainage storage tank W1 in which drainage containing iodine is stored via drainage supply lines L1, L2 and L4, and drainage discharge lines L3, L5 and L6. It is connected to the outside via

  The supply lines L1, L2, and L4 are provided with valves V1, V2, and V4, respectively, and the discharge lines L3 and L5 are provided with valves V3 and V5, respectively. The supply line L1 is provided with a pump P1. Further, concentration measuring means M1, M2, and M3 are provided in the drainage storage tank W1, the supply line L1, and the discharge line L6, respectively.

  Further, the control of the valve and pump and the monitoring of the measured value in the measuring device are collectively managed by the control means C1.

  Next, an operation for adsorbing iodine from waste water using the apparatus shown in FIG. 1 will be described.

  First, waste water is supplied from the tank W1 to the water treatment columns T1 and T2 through the waste water supply lines L1, L2, and L4 from the tank W1 to the water treatment columns T1 and T2. At this time, iodine in the wastewater is adsorbed to the water treatment columns T1 and T2, and the drained water after the adsorption is discharged to the outside through the drainage discharge lines L3 and L5.

  At this time, if necessary, the contact efficiency promoting means X1 and X2 are driven to increase the contact area between the iodine adsorbent filled in the water treatment columns T1 and T2 and the waste water, and the water treatment columns T1 and T2 are used. The adsorption efficiency of iodine can be improved.

  Here, the adsorption states of the water treatment columns T1 and T2 are observed by the concentration measurement means M2 provided on the supply side and the concentration measurement means M3 provided on the discharge side of the water treatment columns T1 and T2. When the adsorption is performed smoothly, the iodine concentration measured by the concentration measuring means M3 is lower than the iodine concentration measured by the concentration measuring means M2. However, as the adsorption of iodine in the water treatment columns T1 and T2 progresses gradually, the concentration difference of iodine in the concentration measuring means M2 and M3 arranged on the supply side and the discharge side decreases.

  Therefore, when it is determined that the concentration measuring unit M3 reaches a predetermined value set in advance and the adsorption capacity of iodine by the water treatment columns T1 and T2 has reached saturation, the concentration measuring unit M3 is based on information from the concentration measuring units M2 and M3. The control means C1 temporarily stops the pump P1, closes the valves V2, V3, V4 and V5, and stops the supply of wastewater to the water treatment columns T1 and T2.

  Although not shown in FIG. 2, when the pH of the wastewater fluctuates, or when the pH is strongly acidic or strongly alkaline and is outside the pH range suitable for the iodine adsorbent according to the present embodiment. May measure the pH of the wastewater by the concentration measuring means M1 and / or M2 and adjust the pH of the wastewater through the control means C1.

  After the water treatment columns T1 and T2 reach saturation, the water treatment columns T1 and T2 in which iodine adsorption has reached saturation are appropriately replaced with water treatment columns filled with a novel iodine adsorbent. Provided for necessary post-processing. For example, when the water treatment columns T1 and T2 contain radioactive iodine, the water treatment columns T1 and T2 are crushed and then used for cement solidification or the like.

  In the above example, the iodine adsorption system and operation in wastewater using a water treatment column have been described. However, iodine in the exhaust gas is adsorbed by ventilating the exhaust gas containing iodine in the column as described above. It can also be removed.

Example 1
(Synthesis of acrylic particles grafted with amino groups)
To a eggplant-shaped flask (volume: 1 L) with a magnetic stirrer, 0.08 g of polyvinyl alcohol (hereinafter PVA), 19.6 g of sodium chloride, and 500 mL of ion-exchanged water are added and stirred at room temperature for 40 minutes to give a colorless solution. Obtained. Next, a Dimroth condenser was attached to the flask, and the inside of the system was degassed and replaced with nitrogen.

  Next, 17.8 ml of methacrylic acid, 6 ml of divinylbenzene, 34 ml of chlorobenzene, and 0.2 g of azobisisobutyronitrile (hereinafter referred to as AIBN) were mixed in a beaker (volume: 200 ml). The obtained mixture was added to the above solution by decantation, and the mixture was heated and stirred at 80 ° C. for 6 hours under a nitrogen atmosphere to obtain a colorless suspension. The AIBN was deactivated by removing the flask from the oil bath and exposing the suspension to air.

  Subsequently, the resin fine particles were allowed to settle by allowing to stand in a draft, and the supernatant was removed by decantation. The remaining resin fine particles were charged with ion exchange water having the same volume accuracy as the resin fine particles, washed by gently shaking the flask by hand, and the supernatant was removed by decantation. This washing operation was repeated three times. The obtained resin fine particles were subjected to suction filtration using a Kiriyama funnel and washed with ion exchange water and acetone in this order. Finally, the solvent was completely distilled off under reduced pressure to obtain an acrylic resin carrier.

  Next, 5 g of an acrylic resin carrier was placed in a two-necked eggplant type flask (volume: 100 mL) equipped with a magnetic stirrer and a Dimroth condenser, and deaeration and nitrogen substitution were repeated three times. Furthermore, 20 mL of ethylenediamine was added in a nitrogen atmosphere, and the mixture was heated and stirred at 120 ° C. for 9 hours. After returning to room temperature, the solution was suction filtered with a Kiriyama funnel and washed with ion exchange water and acetone in this order. Thereafter, the solvent was completely distilled off under reduced pressure to obtain an acrylic resin carrier grafted with light yellow amino groups.

(Synthesis of iodine adsorbent)
In a 20 ml screw vial, 0.150 g of an acrylic polymer grafted with an amino group, 1.50 g of monochlorotriazino-β-cyclodextrin salt-containing powder, and 15 ml of pure water were added, and a horizontal mix rotor (rotation speed: 60 rpm) And stirred at room temperature for 7 hours. Thereafter, the obtained fine particles were filtered, washed with pure water, and then the solvent was distilled off over 7 hours to obtain an iodine adsorbent as reddish brown fine particles (yield 0.165 g).

  The structure of the obtained reddish brown fine particles was identified by using an infrared spectrum. FIG. 3 shows the spectrum of the obtained reddish brown fine particles, the spectrum of the carrier before the reaction, and the difference spectrum obtained by subtracting the spectrum of the carrier from the spectrum of the reddish brown fine particles. FIG. 4 shows the difference spectrum of FIG. 3 together with the spectrum of MCT-β-CD.

FIG. 4 shows that the difference spectrum between the obtained reddish brown fine particles and the carrier is in good agreement with the spectrum of MCT-βCD. In addition, a peak considered to be derived from the triazine ring at 800 cm ⁻¹ and a peak characteristic to the polysaccharide considered to be derived from CO stretching vibration at 1100 cm ⁻¹ were clearly confirmed. From the above results, it was shown that the obtained reddish brown fine particles have a cyclodextrin and a triazine ring.

(Iodine adsorption test)
20 mg of iodine adsorbent was placed in 30 mL of a screw vial, 20 ml of a 650 ppm aqueous solution of potassium iodide (KI) was added thereto, and the mixture was stirred at room temperature for 2 hours using a horizontal mix rotor (rotation speed: 60 rpm). It filtered with the membrane filter made from a cellulose, and the iodine ion (I < ^- >) density | concentration in the colorless solution obtained was measured using the ion chromatography. The ion chromatography was measured using an Alliance HPLC system manufactured by Japan Waters. The measurement conditions shown in Table 1 were used.

  The results obtained are summarized in Table 2 below.

(Example 2)
A reaction using chitosan (manufactured by Wako Pure Chemical Industries, Ltd.) as a carrier instead of the acrylic polymer grafted with an amino group was carried out to obtain an iodine adsorbent which was a colorless solid.

The structure of the obtained compound was identified using an infrared spectrum. FIG. 5 shows the spectrum of the product when chitosan was used as the carrier, including the carrier (chitosan) before the reaction and the spectrum of MCT-βCD. Since chitosan is also a polysaccharide, the characteristic peak for polysaccharides near 1100 cm ^-1 could not be confirmed before and after the reaction, but a peak thought to originate from the triazine ring near 800 cm ^-1 was generated. Observed in the product spectrum. Also over the 1700 cm ^-1 from 1200 cm ^-1, peaks were confirmed in the same manner one and MCD-βCD.

  From the above results, it was shown that even when chitosan was used as the carrier, the product had βCD and a triazine ring. On the other hand, when porous cellulose particles were used as the carrier, the IR spectrum of the product almost coincided with the spectrum of the carrier before the reaction. From this result, it was suggested that when porous cellulose particles were used as the carrier, the reaction with monochlorotriazino-β-cyclodextrin did not proceed easily.

  Further, an iodine adsorption test was conducted in the same manner as in Example 1, and the results shown in Table 2 were obtained.

(Comparative Example 1)
Monochlorotriazino-β-cyclodextrin was reacted with porous cellulose particles (Viscopar manufactured by Rengo Co., Ltd.) in the same manner as in Example 1 to obtain colorless particles. Further, an iodine adsorption test was conducted in the same manner as in Example 1, and the results shown in Table 2 were obtained.

(Comparative Example 2)
Using the monochlorotriazino-β-cyclodextrin used in Example 1 as it was without binding to the carrier, an iodine adsorption test was carried out in the same manner as in Example 1, and the results shown in Table 2 were obtained.

(Comparative Example 3)
An iodine adsorption test was conducted on β-cyclodextrin in the same manner as in Example 1, and the results shown in Table 2 were obtained.

(Comparative Example 4)
Using the acrylic polymer grafted with an amino group used in Example 1 as it was, an iodine adsorption test was carried out in the same manner as in Example 1, and the results shown in Table 2 were obtained.

(Comparative Example 5)
Using the monochlorotriazino-β-cyclodextrin as it was without reacting with chitosan in Example 2, an iodine adsorption test was carried out in the same manner as in Example 1, and the results shown in Table 2 were obtained.

(Comparative Example 6)
Using the porous cellulose used in Comparative Example 1 as it was, an iodine adsorption test was carried out in the same manner as in Example 1, and the results shown in Table 2 were obtained.

As is clear from Table 2, all of the adsorbents of Examples obtained high iodide anion (I ⁻ ) adsorption ability, but were low when the comparative adsorbents were used. This is presumably because in the comparative example, monochlorotriazino-β-cyclodextrin, which controls the adsorption ability of iodide anion (I ⁻ ), is not sufficiently added to the carrier quantitatively.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

T1, T2 Water treatment column P1 Pump M1, M2, M3 Concentration measuring means C1 Control means W1 Drainage storage tank L1, L2, L4 Drainage supply line L3, L5, L6 Drainage discharge line V1, V2, V3, V4, V5 Valve X1, X2 Contact efficiency promotion means

Claims (4)

A carrier having an amino group ;
Triazino-β-cyclodextrin or a derivative thereof bound to the carrier via the amino group ;
An iodine adsorbent comprising: at least one of chlorine encapsulated in the triazino-β-cyclodextrin or a derivative thereof and chlorine bonded to the surface of the triazino-β-cyclodextrin or a derivative thereof. The iodine adsorbent according to claim 1, wherein the iodine adsorbent has an average particle size of 150 μm or more and 500 μm or less. It was obtained by reacting a carrier having an amino group with monochlorotriazino-β-cyclodextrin or a derivative thereof, and binding the triazino-β-cyclodextrin or a derivative thereof to the carrier via the amino group. Characteristic iodine adsorbent. Before SL monochlorotriazinyl rear Gino -β- cyclodextrin or a derivative thereof is characterized in that is reacted via an amino group obtained by graft-modified on the support, the iodine adsorbent according to claim 3.

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