JPH01167203A - Collection of iodine in gas - Google Patents

Abstract

PURPOSE:To easily produce iodine useful in iodine-production industry, pharmaceutical industry, etc., in high efficiency, by contacting an acidic solution with a gas in the presence of a solid adsorbent. CONSTITUTION:An iodine-collecting agent (C) is produced by compounding (A) a solid adsorbent such as an anion-exchange resin having spherical form of 0.1-1.0mmphi in diameter and capable of adsorbing 0.1-1.2g of organic or inorganic molecular iodine (in terms of I2 based on 1g of the adsorbent) and (B) acidic solution of a mineral acid such as HCl having a pH of <=3 and a concentration of 0.1-2.0N at a volume ratio (A:B) of 1:10-2. The component C is packed in the 1st-3rd columns 2-4 and an iodine-containing gas 1 is supplied to the bottom of the 1st column 2 at an average flow rate of about 36$1/h to collect iodine in each column. The collected iodine is desorbed with an NaOH solution containing NaNO3, etc., and recovered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for collecting iodine in a gas, and more specifically, the present invention relates to a method for collecting iodine in a gas. The present invention relates to a method for efficiently collecting iodine by bringing it into contact with iodine. Therefore, it is used in many chemical and pharmaceutical industries that use iodine, including the iodine manufacturing industry.

[Prior Art] Industrial sources of iodine include Chilean saltpeter ore, oil brine, natural gas brine, etc. In Japan, natural gas brine is the main raw material due to cost.

Iodine production methods vary depending on the raw material, and when using natural gas brine, there are activated carbon methods, preparation methods, expulsion methods, etc. Of these, the activated carbon method has now been replaced by the ion exchange resin method due to economic and technical problems.

The outline of the preparation method is to add a mixed solution of copper sulfate and ferrous sulfate to brine, precipitate iodine ions in the form of cupric iodide, and then heat and oxidize the concentrated sludge in a combustion furnace to produce molecular iodine. obtain.

The expulsion method involves adding sulfuric acid to slightly alkaline brine to make it neutral or slightly acidic, then adding chlorine gas to oxidize iodine ions to free iodine, and expelling (sublimating) this iodine with air to form sulfurous acid. Absorb into solution. Hydrogen iodide in this absorption liquid is oxidized again with chlorine to obtain molecular iodine.

In the ion exchange resin method, iodine ions are partially oxidized to molecular iodine using chlorine, and then adsorbed and concentrated on an anion exchange resin. Iodine is eluted from this resin using a sodium hydroxide solution and a sodium chloride solution, the resin is acidified with sulfuric acid, and an oxidizing agent is added to produce molecular iodine.

Conventional methods for collecting iodine in gases include the following.

In the method of washing gas with an alkaline solution, molecular iodine is efficiently collected as ions according to the following formula.

12 + [1Na011;=! 5Nal + Na
103 +3H20 (1) However, the coexisting carbon dioxide gas is also collected at the same time, CO2+ 2NaOH:Na2 CO
3+ H20 (2) Na2CO3+CO2+ H20
=2Nat(CO3(3)), which makes the alkaline solution lose its effectiveness.

Although the method of cleaning gas with an acidic solution eliminates the absorption of carbon dioxide gas, there is a limit to the solubility of iodine, and since it vaporizes (sublimates) along with the passing gas, the amount of collected
This results in a decrease in both collection efficiency. Therefore, in order to put this method into practical use, it is necessary to use nitric acid with a very high concentration of 15.3 M, which does not cause iodine to volatilize, as disclosed in Japanese Patent Application Laid-Open No. 48-31180.

In addition, nuclear power related facilities use a method called the Iodox method, which converts gas into Hg (NO3) 2-H
Iodine is collected by washing with NO3 solution and adsorbing it with silver zeolite, but this method is very expensive and there is a risk that 11g ions may be mixed in with the recovered iodine, making it difficult to use in pharmaceuticals and food products. It is not appropriate to use it as an additive or as a feed mixer.

Furthermore, there are many known methods for capturing iodine in gases using solid adsorbents, but the amount and efficiency of these methods vary greatly depending on various conditions such as relative humidity and nitrogen oxide concentration in the gas. There are some drawbacks that can be affected.

[Problem to be solved by the invention 1 Molecular iodine has a very strong sublimation property and is a substance that easily volatilizes in the air. Therefore, in any of the above production methods, iodine must be completely recovered and used. That is difficult. In particular, when brine is made acidic, coexisting bicarbonate ions are generated as carbon dioxide gas, and when iodine ions are oxidized with chlorine, excess chlorine is volatilized as a gas and sublimated as an iodine carrier. To help this, it volatilizes into the -layer air, resulting in a loss of production.

Also, like chlorine gas, iodine gas is highly oxidizing and harmful, so it should be completely removed from the air inside the factory.

In order to solve these problems, it was necessary to develop a method for efficiently collecting io 5 =trisium in gases.

[Means for Solving the Problems] The present inventors have completed the present invention as a result of their earnest efforts to develop a method that is safe, inexpensive, and has a high collection amount and collection efficiency.

That is, the present invention is a method for collecting iodine in a gas in which an acidic solution and a gas are brought into contact in the presence of a solid adsorbent, and specifically, a gas containing iodine is brought into contact with an acidic solution containing a solid adsorbent. This is a method of very efficiently capturing and recovering iodine by introducing it and bringing it into contact.

Conventionally, methods for collecting iodine in gases include washing with an acidic or alkaline solution, or adsorbing it to an adsorbent. It was discovered that by contacting with a gas containing iodine, a higher amount of collection and collection efficiency than previously seen could be obtained, leading to the present invention.

It is believed that the excellent effects of the present invention are exhibited through the following cycle. That is, by bringing a gas containing iodine into contact with an acidic solution containing a solid adsorbent,
Iodine is dissolved in acidic solution due to gas-liquid equilibrium, and this iodine is further rapidly adsorbed by solid adsorbent due to solid-liquid equilibrium, reducing the iodine concentration in the solution, which reduces the dissolution of iodine into acidic solution. It will encourage you. In this way, iodine will rapidly move from the gas to the solution and then into the solid adsorbent until the adsorption capacity of the solid adsorbent is saturated.

It is presumed that the remarkable effects of the present invention are brought about by the following phenomenon. That is, when a gas containing iodine is introduced into an acidic solution in which a solid adsorbent is dispersed, fluidization and stirring of the liquid phase occurs due to the introduction of the gas, and this fluidization and stirring of the liquid causes the solid adsorbent dispersed in the liquid phase to flow and stir. Existence makes this process extremely smooth. This occurs along with relatively large-scale macroscopic movement and mixing of liquid caused by the introduction of gas.
The rotation, dispersion, and coalescence of solid adsorbent particles cause microscopic agitation of the liquid, which constantly renews the gas-liquid and liquid-solid interfaces, thereby increasing gas adsorption between the gas and liquid. This is thought to be because the mass transfer in the phase-solid adsorbent proceeds extremely smoothly. As a result, it is presumed that a higher collection amount and collection efficiency than ever seen before was achieved.

If even higher collection efficiency is required, this can be achieved by connecting the processes in series.

The solid adsorbents used in the present invention include activated carbon,
There are no limitations as long as it is acid resistant and has good iodine adsorption performance in acidic solutions, such as anion exchange resins and MR type resins. Examples of the solid adsorbent include the following.

That is, activated carbon includes fruit shell-based, wood-based, coal-based, petroleum-based, carbon black-based, and anion exchange resin includes:
Examples of styrene-divinylbenzene-based strong basic resins and weakly basic resins, as well as MR resins, include styrene-divinylbenzene-based and acrylic ester-based resins having exchange groups or those having no exchange groups. The particle size of these solid adsorbents is 0.1 to 1.0, considering the flow and stirring of the solid in the liquid. It is preferable that the shape of Ommφ is as close to a spherical shape as possible, and the adsorption performance is preferably one that has an iodine adsorption amount of about 0.1 to 1.2 (g-12/g-adsorbent).

The acidic solution used in the present invention is preferably an aqueous solution of a mineral acid such as nitric acid, sulfuric acid, or hydrochloric acid. The concentration of the acid is not particularly limited as long as it can be easily handled at pH 3 or below in order to keep molecular iodine stable, but it is 0.1 to 2.0 as it is not economical to increase the concentration. A concentration of about 0 normal is used.

The solid adsorbent used in the present invention must be able to move freely in the acidic solution. For this purpose, it is preferable that the ratio of the solid adsorbent to the acidic solution is in the range of 10 to 1=2 by volume.

The method of the present invention has been developed to effectively utilize resources by collecting, collecting and reusing iodine that volatilizes in the gas during the iodine production process. It can also be used as a substitute for the sulfite absorption liquid in the expulsion method, which is one of the manufacturing methods. In this case, after collecting the iodine, it is sufficient to take out only the adsorbent, recover the iodine, and regenerate and reuse it, and the acidic solution can be used again as long as it has a pH of 3 or less, which is economical. Furthermore, it can be applied to the collection of radioactive iodine as a safe and inexpensive iodine collection method with good collection efficiency.

[Examples] Next, the present invention will be specifically explained using Examples and Comparative Examples.

Example 1 Columns with an inner diameter of 19 nu++φ and a height of 80 mm were connected as shown in Figure 1, and each column was filled with 0.1 mo115 of nitric acid.
0ml and anion exchange resin (Dowcx lx 8.5
0-100mcsh) 1g from the bottom of the column.
2709 air containing 1.2 ppm I2 = 10- was supplied at an average flow rate of 3.8 A/h.

The iodine collected in each column is NaNO32mol/1
O containing 1, 1 mol/9. It was washed out with a NaOH solution and analyzed using the JIS K-01 inch iodine analysis method. The results show that the amount collected in the first column was 160 mg, and the amount collected in the second column was 160 mg.
The column weighed 150 mg, and the third column weighed 7.5 mg. The value of the first column is the saturated amount of collection, and the collection rate is calculated from the amount of collection of the second and third columns using the following approximate formula: Collection rate (%) = fl (7, 5/1.50)]
100 = 95.0 (%).

Comparative Example 1 Columns with an inner diameter of 19 mmφ and a height of 80 mm were connected as shown in Figure 1, and 10 m of 0.1 mo1151 nitric acid was added to each column.
1, and air containing 4.2 ppm of 12 was supplied at 3.5 A from the bottom of the column at an average flow rate of 3.6111/h.

The iodine collected in each column is 0.1mol1151Na
It was washed out with an OH solution and analyzed using the iodine analysis method of JIS K-01 (11).The results showed that the amount collected in the first column was 1.55 mg, the second column was 1.50 mg, and the third column was 0. The value of the first column is the saturated amount of collection, and when the collection rate is calculated from the amount of collection of the second and third columns using the following approximate formula, the collection rate ( %;) = +1- (0,75/1..50
)l +1.00=50.5(%).

Comparative Example 2 Columns with an inner diameter of 19 mm and a height of 80 mm were connected as shown in Figure 1, and each column was coated with anion exchange resin (Dovex).
lx 8.50~1.00mesh> Insert Ig,
Air containing 1.2 ppm of I2 is supplied from the bottom of the column at an average flow rate of 3.69/h.

The iodine collected in each column is NaNO32mo115
It was washed out with a 0.1 mol/51 NaOH solution containing 1 and analyzed using the JIS I (-0101) iodine analysis method.The results showed that the amount collected in the first column was 160 mg.
, the second column or 1. 'aOmg, 3rd column is 9Jmg
Met. The value in the first column is the saturated amount of collection;
The collection rate is calculated using the following approximate formula based on the amount of collection in the third column and the collection rate (%) -11-(91/130)l
It was 0-30.0 (%).

Examples 2 to 4 Columns with an inner diameter of L9nvφ and a height of 80mm were connected as shown in Figure 1, and each column was filled with styrene-divinylbenzene M.
R resin (prototype, non-polar, 100-150 mesh)
10 ml of an aqueous solution whose pH had been adjusted to 4 with Ig and nitric acid was charged, and air containing 1.2 ppm of I2 was exchanged from the bottom of the column at an average flow rate of 3.8 U/h at 40 to 280 ml.

Further, under the same conditions, 10 ml each of nitric acid aqueous solutions having pHs of 3 and 1 were used.

The iodine collected in each column was 0.1mol115°Na
It was washed out with an OH solution and analyzed using the iodine analysis method of J r S K-0101. The results were evaluated in the same manner as in Example 1 and were as shown in Table 1.

Table 1 [Effects of the Invention] As explained above, by the method of the present invention, iodine in gas can be collected relatively easily and efficiently.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an example of an iodine collection device used in Examples and Comparative Examples. ■...Iodine-containing gas, 2...1st column, death...
2nd column, 4... 3rd column, 5... gas indicator needle.

Claims (4)

[Claims] (1) A method for collecting iodine in a gas, which comprises bringing the gas into contact with an acidic solution in the presence of a solid adsorbent. (2) The method according to claim 1, wherein the solid adsorbent is an acid-resistant organic or inorganic molecular iodine adsorbent. (3) The method according to claim 1 or 2, wherein the acidic solution is a mineral acid and its pH is maintained at 3 or less. (4) The method according to any one of claims 1 to 3, wherein the volume ratio of the solid adsorbent to the acidic solution is in the range of 1:10 to 1:2.