JPH0360426A - Production of high-purity cesium chloride - Google Patents

Abstract

PURPOSE:To prevent formation and admixture of Rb salt without generating toxic gas at a time of reaction and to easily obtain high-purity CsCl by utilizing H2O2 as an oxidizing agent and utilizing hydrazinium salt as a reducing agent respectively and treating a hydrochloric acid-based soln. contg. Cs ions. CONSTITUTION:I2 powder equivalent to Cs is added to a 5-9 N hydrochloric acid-based soln. contg. Cs<+> such as Cs2CO3. Thereafter aqueous hydrogen peroxide having >=30wt.% concn. of 1-1.7 equivalent to I2 is added. The soln. is agitated until I2 is extinguished while the temp. of the soln. is maintained at 30-40 deg.C. After CsICl2 is formed, the soln. is heated to rise the temp. and deposited crystal is dissolved. This soln. is left to cool and CsICl2 is deposited, separated and recovered. Then separated and recovered CsICl2 is mixed with the required amount of water. Hydrazinium salt is added while agitating the soln. until CsICl2 disappears and both I2 and CsCl soln. are produced. I2 is separated and the obtained CsCl soln. is heated and concentrated and thereafter left to cool. Further after adding acetone, this CsCl soln. is left to cool and deposited high- purity CsCl is separated and recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the production of high purity cesium chloride used as an organic synthesis catalyst or for DNA purification.

[Prior Art] Japanese Patent Publication No. 46-803 discloses a method for industrially producing high-purity cesium chloride. This method uses a cation exchange resin or an inorganic ion exchanger, and the former uses a dilute cesium solution because the separation coefficient between cesium and rubidium is very small, and the solution in the cation exchange resin layer is The linear velocity has to be extremely slow, which necessitates large capital investment and low productivity.The latter method uses an extremely dilute cesium salt aqueous solution, although the separation coefficient between cesium and rubidium is high. However, it has the disadvantage that it is unavoidable to be contaminated with phosphorus and heavy metals, which are the most hindrances in biotechnology.

As a method for solving the above drawbacks, a method for producing cesium chloride via cesium dichloroiodate has been disclosed (New Experimental Chemistry Course 8 Synthesis of Inorganic Compounds, Chemical Society of Japan 1976). In this method, cesium chloride is dissolved in 9M hydrochloric acid, mixed with a calculated amount of 9M hydrochloric acid solution containing iodine chloride, and cooled to obtain cesium dichloroiodate. It is heated to 200'C and decomposed to obtain cesium chloride. When cesium nitrate is used as a raw material, iodine is added to a high temperature solution of cesium nitrate dissolved in hydrochloric acid. In any case, by using chlorine gas or nitric acid as the oxidizing agent, iodine can be used in place of the expensive iodine monochloride.

[Problems to be Solved by the Invention] However, in these methods, the use of expensive iodine monochloride impairs economic efficiency, and to avoid this, if iodine and an oxidizing agent are used, for example, chlorine is used as an oxidizing agent. When used, not only does the reaction require a high temperature and equipment made of a special material with high corrosion resistance, but the reaction efficiency is poor and unreacted chlorine gas is released into the atmosphere. Also,
When nitric acid is used as an oxidizing agent, the system becomes aqua regia,
Similarly, not only equipment made of special materials is required, but also a large amount of NO is generated during the oxidation reaction. Also, depending on the conditions,
There is a problem in that poorly soluble iodate is produced, reducing the purity of cesium dichloroiodate, and reducing the Rh concentration in the obtained cesium chloride to about 200 ppm. In addition, when cesium dichloroiodate is heated and decomposed, highly corrosive chlorine and iodine are generated, corroding equipment, etc., and not only increasing the risk of contamination with impurities but also deteriorating the working environment. There is.

An object of the present invention is to provide a method free of the above-mentioned problems in obtaining highly purified cesium chloride from cesium salt containing various impurities including rubidium.

[Means for Solving the Problems] The method of the present invention for solving the above problems involves adding iodine powder in an amount equivalent to cesium to a 5-9N hydrochloric acid solution containing cesium ions, and then te1〜゛1
．． After adding 7 equivalents of 30% or more hydrogen peroxide solution,
While maintaining the liquid temperature at 30 to 40'C, stir until the iodine powder disappears to produce cesium dichloroiodate, then heat the liquid to raise the temperature to dissolve the precipitated crystals,
A first step of cooling to precipitate cesium dichloroiodate and separating and recovering it; and a first step of mixing cesium dichloroiodate obtained in the first step with a desired amount of water; Add hydrazinium salt until it disappears to produce iodine and cesium chloride solution, heat and concentrate the cesium chloride solution obtained by separating iodine, and then let it cool, or add acetone etc. and let it cool. The method for producing high-purity cesium chloride is characterized by comprising a second step of separating and recovering precipitated cesium chloride.

[Effect] The present invention will be explained below by dividing into a first step and a second step.

(1) First step The first step is a step of obtaining cesium dichloroiodate from a hydrochloric acid cesium solution.

In this step, the 5-9N hydrochloric acid solution containing cesium ions may be prepared by dissolving the cesium salt in a 5-9N hydrochloric acid solution, or by mixing an aqueous solution of cesium salt and a hydrochloric acid solution, or by mixing a cesium salt aqueous solution and a hydrochloric acid solution. Instead of a solution, the main subject - C obtained in the process
The mother liquor after s1C1i recovery may be used. There is no problem with the cesium salt used as long as it is soluble in the hydrochloric acid solution, but in order to avoid an unnecessary increase in anions, it is preferable to use cesium carbonate or impure cesium chloride.

The reason why the hydrochloric acid concentration is set to 5 to 9N is that when the hydrochloric acid concentration is low, the solubility of Cs1C1i produced becomes high, the yield deteriorates, and economic efficiency is impaired, and when it is high, separation of impurity elements such as Cs and Rb becomes worse. Because it does.

In this first step, iodine is oxidized using a hydrogen peroxide solution, and the purpose of using the hydrogen peroxide solution is to prevent the contamination of impurities and the generation of harmful gases such as chlorine. That is, the Cs1C1° production reaction in the first step is shown by the following equation, but normally at room temperature, the reaction of equation 0 is biased toward the left side, and as the reaction of equation (■) progresses, the reaction of equation 0 is Proceed to the right side.

As can be seen from equations (1) and (2), in the present invention, the reaction of equation 0 proceeds with the production of Cs101s, so no chlorine gas is generated.

2t [CI + flies” C1* + 2Hs
Is of O-m- + C12+ 2C3+ C1-=2
CslCL -0 In this step, cesium and iodine react quantitatively, so the amount of iodine added may be equivalent to that of cesium. In addition, hydrogen peroxide for oxidizing iodine may be used in an equivalent amount to iodine, but
It is necessary to add more when the temperature is high, stirring is insufficient, and self-decomposition of hydrogen peroxide must be taken into account, but if too much is added, chlorine gas will be generated, so 1.7 equivalents are added. The following ε is required.

Incidentally, the reaction rate of formula (2) depends on the hydrochloric acid concentration and reaction temperature, and a high reaction temperature is particularly desired when the hydrochloric acid concentration is low. However, if the reaction temperature is too high, iodine will volatilize, so it is preferable to set it at 30-40'C.
.

The completion of the reaction is determined by the disappearance of iodine. The part that exceeds the solubility of Cs1C1a generated at this time exists in the system as a precipitate, but since this precipitate contains impurities such as Rb, the temperature of the liquid is raised to completely dissolve the precipitate, and then released. It is cooled to precipitate high purity Cs1C1i. At this time, the temperature required varies depending on the amount of precipitate present, but it is preferably around 80°C in order to complete the reaction and completely dissolve the precipitate to achieve a purification effect.

The method for separating the precipitated high-purity Cs1C1i is not particularly limited. In addition, the mother liquor after recovering high-purity Cs1C1 can be used to create a cesium hydrochloride solution in the genuine leather process as described above in order to ensure the yield of high-purity Cs1C1. Needless to say, whether or not this is possible depends on the impurity concentration.

Genuine leather - The concentration of hydrogen peroxide used in the process is Cs1C
Since the solubility of 1 t is relatively high, it is desirable to use as high a concentration as possible, and preferably 30% by weight or more.

It goes without saying that if the purity of the obtained Cs1C1z is insufficient, it can be purified by heating and dissolving it using a hydrochloric acid solution, allowing it to cool, and recrystallizing it.

(2) Second Step This second step is a step of reducing the high purity Cs1C1° obtained in the first step to obtain high purity CsC1.

The purpose of mixing high purity Cs1CL with water is to cause a reaction and to completely dissolve the C5Ct produced. Therefore, it is necessary to set the amount of water used so that this purpose can be achieved. In addition, the reducing agent that can be used in this process must be able to prevent the contamination of impurities and must not produce any substances that cannot be removed by the reaction.For this reason, the use of hydrazine, hydrazine hydrate, and hydrazinium salts is considered. . However, hydrazine and hydrazine hydrate are not suitable because the iodine produced by the heat of neutralization and reduction reaction evaporates. Even if hydrazinium salt reduces iodine to a single element, it still produces iodine ions.
There is no reduction to 100%, and no significant reaction heat is generated. From the above, hydrazinium salt is optimal as the reducing agent used in this second step.

The reaction when N, H, and C1 are used as reducing agents is shown in equation (2).

4CsIC1s + N5llsC1z ” 4CsC
I + 611CI +Nt +21*■ When a reducing agent is added, orange Cs1C1t decreases according to the formula (■), and 17 black IO precipitates. The end of the reaction is indicated by an orange C.
The iodine produced in the 12-line reaction, which can be judged by the disappearance of s[C1i, mainly contains cesium chloride as an impurity, with negligible amounts of other elements, and can be used sufficiently for the oxidation reaction in the first step.

After separating and removing iodine, the solution is heated and concentrated until it becomes saturated with CsC1, and then allowed to cool to precipitate CsC1. Alternatively, after heating and concentrating, add acetone etc. to CsC1
is precipitated.

Note that CsC1 obtained by the method of the present invention contains a very small amount of iodine, but if necessary, the iodine solution obtained in the second step may be brought into contact with a water-insoluble organic solvent to remove iodine. After extracting and removing C, it is heated and concentrated to obtain iodine-free C.
It is also possible to obtain sC1.

[Example] Dissolve cesium carbonate in water to obtain Cs 31.2, Rb
O, 33, Ha O, 41, SO 40, 8? , L
i<0.01. K <0.01゜Ca
(0,01, Ba <0.01. AI <
0.01. Mg <0.01, re <0.
01, P <0.01 Rb/Cs ratio is 0.0 for each g/l.
A solution of Oll was obtained. 1460 ml of this solution 121
and then 9 N of CC51C1 saturation at 20 °C.
Add to 3400 ml of HC1 solution, then 3-5f
Add 1032.6 g of crushed iodine to fi+1,
While stirring, 808.1 ml of 30 W/V 1% hydrogen peroxide solution was added. Next, the solution was heated to 40'C and stirred until iodine disappeared. Next, increase the liquid temperature to 8
Completely dissolve the precipitated Cs1C1 crystals at 0°C,
The crystals were then allowed to cool and were dried to obtain 2094 g of high purity Cs1C1x. The direct yield is 78%,
The Rb/Cs ratio of the obtained crystal was 6.5 x 10-'
Met.

1283 g of this crystal and 2035 ml of 5.7N hydrochloric acid
were mixed, heated to 80°C to dissolve, and then allowed to cool to room temperature. The precipitated crystals were dried to obtain 1123 g of highly purified Cs1C1z crystals. The direct yield was 88% and the Rb/Cs ratio of the crystals was 6.5X 10-'.

Next, purified high purity Cs1C1, 1096 g of crystals and 1 water
1 and 56 hydrazinium monochloride while stirring.
．． 7g was added for reduction. The generated iodine has a moisture content of 20
%, 522 g, and the direct yield was 99%. The mother liquor from which iodine was separated and removed was concentrated at 80°C using an evaporator until CsC1 was saturated, and then 5
00 ml of acetone was added to precipitate CsC1, which was dried to obtain 480 g of high purity CsC1 crystals. Direct yield was 86%.

Note that the impurities in this crystal are Rb 2, Na O, 4
, Sku5, Li O,2, K O12, Ca
<0.5, Ba <0.5, AI<0.5
, Mg Q,1,re <0.5, p <o,s
each ppm.

[Effects of the Invention] According to the method of the present invention, since hydrogen peroxide is used as an oxidizing agent and hydrazinium salt is used as a reducing agent, not only no toxic chlorine gas is generated during the reaction, but also no rubidium salt is produced. It is possible to easily obtain highly pure cesium chloride. Furthermore, the iodine produced during the reaction has high purity and can be used repeatedly within the system, making the present invention more economical.

Claims (1)

[Claims] Iodine powder in an amount equivalent to cesium was added to a 5-9N hydrochloric acid solution containing cesium ions, and then 30% by weight or more hydrogen peroxide solution, which was 1 to 1.7 equivalents to the iodine, was added. After that, the solution was stirred while maintaining the temperature at 30 to 40°C until the iodine powder disappeared to form cesium dichloroiodate.Then, the solution was heated to increase the temperature to dissolve the precipitated crystals, and allowed to cool. , a first step of precipitating cesium dichloroiodate and separating and collecting it, and mixing the cesium dichloroiodate obtained in the first step with a desired amount of water, and the cesium dichloroiodate disappears during each step. Add hydrazinium salt until the hydrazinium salt is added to produce an iodine and cesium chloride solution, heat and concentrate the cesium chloride solution obtained by separating the iodine, and then let it cool, or add acetone etc. and let it cool to get the precipitated chloride. A method for producing high-purity cesium chloride, comprising a second step of separating and recovering cesium.