JPS61157539A - Decomposition treatment of ion exchange resin - Google Patents

Abstract

PURPOSE:To carry out the decomposition of an ion exchange resin using hydrogen peroxide as an oxidizing agent in the presence of iron catalyst, in high decomposition ratio and low generation of sludge, by using nickel as a cocatalyst. CONSTITUTION:(A) An ion exchange resin, especially a waste radioactive ion exchange resin generated from various nuclear installations is charged to a reactor together with (B) hydrogen peroxide solution and (C) an iron and nickel compound having an Fe ion concentration of 0.001-0.01M and an Ni ion concentration of 0.005-0.03M, preferably sulfate or nitrate. The ion exchange resin is decomposed at room temperature - 100 deg.C under agitation while keeping the pH of the reaction liquid to >=1.8, preferably >=2. The use of nickel as a cocatalyst enables the decomposition of even an anion exchange resin in high decomposition ratio at low Fe ion concentration suppressing the generation of sludge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention particularly relates to a chemical decomposition treatment method suitable for reducing the volume of used ion exchange resins (waste resins) generated from various nuclear facilities.

[Prior art and its problems]

Ion exchange resins are widely used for water purification, wastewater treatment, separation of various elements, etc., and are particularly used in the nuclear field for purification of reactor cooling water, wastewater treatment, separation and purification of rare earth elements and ultra-plutonium elements, etc. has been done. In recent years, as the number of nuclear power plants in operation has increased, the amount of various solid wastes has increased, and the treatment and final disposal methods have become a problem. Among solid wastes, ion exchange resins have a large capacity and are discarded after being used to treat liquid systems.
Therefore, its volume reduction has become a serious issue.

The combustion method,
A thermal decomposition method, an acid decomposition method, etc. have been proposed, but none of them have been definitive. The combustion method is characterized by high processing speed, but! '-+lk, HJ+++1
-+xth+a-9J-u, +IkJ/-yhnfil
There are drawbacks such as a complicated system and the production of volatile radioactive compounds. In addition, although the pyrolysis method does not generate radioactive volatiles, it has the drawback that it produces a large amount of carbonate residue and, like the incineration method, the flow system is complicated. Furthermore, the acid decomposition method uses concentrated sulfuric acid and concentrated nitric acid. L (about 260℃)
This method decomposes used ion exchange resin by decomposing the resin to about 90%, and although it does not have the drawbacks of the above methods, it also decomposes SOx, The disadvantage is that harmful gases such as NOx are generated.

In the reaction between the ion exchange resin (Cm) (n) and sulfuric acid, CmHn+n/2HzSO4- nHzO+n/2SOt↑+mC C+ 2 Has 04 → 2 HzO+ 2 SOz + CO□↑In the reaction between C generated above and nitric acid, 3 C+ 4 HN Os → 4NO↑ 2H,O+3CO□↑ 5C+4HNO,→ 2Nz T+2HtO+5COz↑ 2 C+ 2 HN Oa → NzO+ HzO+ 2 COz↑ The acid decomposition method described above can also be carried out at very high temperatures. very to be It was necessary to use expensive heat-resistant materials (such as tantalum) in the reactor.

Therefore, a method has been proposed in which ion exchange resin is decomposed at a temperature of about 100° C. using hydrogen peroxide and an iron ion catalyst (Japanese Patent Laid-Open No. 1446/1983).

However, although this method can easily decompose the cation exchange resin to about 95%, there is a problem when decomposing the anion exchange resin.

That is, as a result of the decomposition process, sludge of iron or the like is generated. The formation of this type of sludge reduces the volume reduction effect of the ion exchange resin. One possible countermeasure to this problem is to lower the concentration of iron added, but there is an optimum value for the iron concentration, and if it is too low, the decomposition rate will decrease. Another solution is to lower the pH of the reaction system, but if the pH is lowered too low (i.e., too acidic),
A large amount of salt will be generated during the later neutralization treatment of the reaction solution. For example, when the pH is lowered with sulfuric acid, the reaction of HzSOa + 2NaOH- Na zSO4+ 21 (20) occurs in the neutralization treatment performed later to produce Na 2S O.
From the viewpoint of volume reduction, it is preferable that the production of a zS Oa be as small as possible.

Actual used ion exchange resin contains cation exchange resin and anion exchange resin, so when decomposing such a mixture with hydrogen peroxide, the challenge is how to reduce the amount of sludge as described above. It has become.

[Purpose of the invention]

The present invention provides a decomposition treatment method that has higher decomposition efficiency and generates less sludge when decomposing ion exchange resins with hydrogen peroxide. It is an object of the present invention to provide a decomposition treatment method that is particularly effective for reducing the volume of used ion exchange resins.

[Key points of the invention]

The above objects are achieved by the present invention. To summarize, the present invention resides in a method for decomposing an ion exchange resin, which is characterized by using iron and nickel as a decomposition catalyst when decomposing the ion exchange resin with hydrogen peroxide.

As mentioned above, when ion exchange resins, especially anion exchange resins, are decomposed using iron as a catalyst, a large amount of sludge is generated. If the concentration of the iron catalyst is lowered in an attempt to avoid this, the decomposition rate will be lowered, and if the pH is lowered, a large amount of salt will be generated during the neutralization treatment performed when the reaction solution is disposed of. It has now been discovered that by adding nickel to the iron catalyst as a co-catalyst, it is possible to perform a decomposition process with a high decomposition rate and a small amount of sludge even when the iron concentration is low.

and nickel are used in ionic form. Since the decomposition reaction is carried out in an aqueous system, any iron and nickel compound can be used as long as the iron and nickel can be dissolved in water to produce the respective ions. Particularly preferred iron and nickel compounds are iron and nickel sulfates, nitrates, and the like. Iron and nickel each preferably have a Fe ion concentration of 0.001 to 0.00. OIM
and the Ni ion concentration is in the range of 0.005 to 0.03M.

As the hydrogen peroxide used as the oxidizing agent, those commercially available in the form of an aqueous solution (hydrogen peroxide solution) can be used. The decomposition reaction is carried out by charging an ion exchange resin, a hydrogen peroxide solution, and a catalyst into a reaction tank, and stirring the mixture. The reaction is preferably carried out at a temperature from room temperature or higher to about 100°C. The lower the pH of the reaction solution, the less sludge will be produced, but considering the amount of salt produced in the later neutralization treatment,
It can be carried out at a pH of 1.8 or higher, preferably 2 or higher.

Ion exchange resins to which the decomposition treatment method of the present invention can be applied are:
This is used (waste) resin generated from various uses. The method of the present invention uses a cation exchange resin (-3O, Hl-COOH
Not only used anion exchange resins (=OH type containing NOH groups, etc.), but also mixtures of used amphoteric ion exchange resins ( It can equally be applied to ordinary waste resins (which are in the form of mixtures).

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using Examples.

Figure 1 shows a schematic diagram of the experimental equipment used to decompose ion exchange resin with hydrogen peroxide. Here, 1 is a reaction tank, into which an aqueous solution in which a catalyst is dissolved and an ion exchange resin are placed. This liquid is stirred by magnetic cooler 2. The third is a water bath, which is used to keep the temperature of the reaction system constant. 4 is a hydrogen peroxide supply port, from which hydrogen peroxide is supplied at a constant flow rate. The catalyst concentration is kept constant by supplying the catalyst solution from the catalyst supply port 5.

Using this device, we conducted an experiment to decompose anion exchange resin. The decomposition conditions are as follows.

Anion exchange resin 5AN-1 (OH type, manufactured by Mitsubishi Kasei) 2g (dry) Supply H, O□ concentration 30% Ht O2 supply rate 1ml/5inPH2 Resin addition amount 2g (dry) Catalyst solution Ferrous sulfate solution Nickel sulfate Solution temperature: 95°C The experimental results obtained are shown in Figure 2. The decomposition rate shown in Figure 2 was calculated from the carbon balance and is expressed by the following formula.

Decomposition rate (%) = carbon content of resin before decomposition This decomposition rate indicates the proportion of organic carbon content before treatment due to decomposition.

As shown in Figure 2, when only an iron catalyst is used, the decomposition rate is extremely reduced below 0.01M, but when nickel and iron are used, even when the iron ion concentration is below 0.01M. 9
A good decomposition rate of 0% or more can be obtained.

Figure 3 shows the amount of sludge produced in each case.

The amount of sludge produced is determined by the amount of iron ions in the sludge (mm
It is indicated by oj1). As shown in the figure, it can be seen that the amount of sludge increases in proportion to the iron ion concentration.

The method is the same as that described in Example 1 by Yuji Kase, except that the ion concentration is 0.01M in the case of iron catalyst only, and the ion concentration in the case of iron + nickel is 0.002M iron + 0.02M nickel. The anion exchange resin was decomposed using OIM, and the relationship between the pH of the reaction system and the amount of sludge produced was investigated. The results are shown in Figure 4. As is clear from this figure, when iron and nickel are used together, the decomposition rate is high even when the iron ion concentration is low, so the amount of sludge produced is low even at the same pH.

Similarly, the above decomposition experiments were conducted for C1 type and S04 type ion exchange resins, and it was confirmed that the addition of nickel as a cocatalyst increased the decomposition rate and lowered the amount of sludge produced.

A common used ion exchange resin (waste resin) is a mixture of a cation exchange resin and an anion exchange resin in a ratio of 1=1 or 2:1. Therefore, the zero decomposition conditions and results of decomposition experiments conducted on such mixtures are summarized in Table 1.

From these results, it is clear that even if the iron ion concentration is reduced, the decomposition rate is high and the sludge reduction effect is large.

〔Effect of the invention〕

According to the present invention, when hydrogen peroxide is used as an oxidizing agent and ion exchange resin is decomposed using an iron catalyst, by using nickel as a co-catalyst, the decomposition rate is higher than when using only an iron catalyst, and sludge is generated. It has become possible to perform decomposition processing in small quantities.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the equipment used in the ion exchange resin decomposition experiment, Figure 2 is the relationship between iron catalyst concentration and decomposition rate, Figure 3 is the relationship between iron catalyst concentration and sludge amount, and Figure 4 is the relationship between iron catalyst concentration and sludge amount. 3 is each graph showing the relationship between PH and the amount of sludge generated. 1...Reaction tank, 2...Magnetic stirrer 3...Water bath, 4...Hydrogen peroxide supply port, 5...Catalyst supply port Answer Z Metetsu catalyst'=U! Shiku Fl, Fe'n1') Stop 9th

Claims (1)

[Scope of Claims] 1) A method for decomposing an ion exchange resin, which comprises using iron and nickel as a decomposition catalyst in decomposing the ion exchange resin with hydrogen peroxide. 2) In the decomposition treatment method according to claim 1, the iron ion concentration in the oxidative decomposition system is from 0.001 to 0.01.
M and nickel ion concentration from 0.005 to 0.03
A decomposition processing method characterized by being within the range of M. 3) The decomposition treatment method according to claim 1, wherein the ion exchange resin is a spent radioactive ion exchange resin generated from various nuclear facilities.