JPH0925117A - Purification of potassium compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively remove Na in an aq. KCl soln. or an aq. KOH soln. used as starting material for producing KOH or Na in a melt of potassium nitrate used for surface treatment of glass. SOLUTION: Crystalline zirconium phosphate represented by the formula AXr2 (PO4 )3 .nH2 O (where A is H or K and 0<=n<=2) is brought into contact with a soln. or melt of a potassium compd. contg. Na ions to remove the Na ions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a starting potassium chloride aqueous solution or obtained potassium hydroxide when a potassium hydroxide aqueous solution is obtained by electrolyzing a potassium compound containing sodium ions, for example, a potassium chloride aqueous solution containing sodium ions. Removal of sodium ions contained in the aqueous solution,
Furthermore, the present invention relates to a method for purifying a potassium compound useful for removing sodium ions in a potassium nitrate melt used for surface treatment of glass.

[0002]

2. Description of the Related Art Industrially produced potassium compounds usually contain 0.05 to 0.4% by weight of sodium as impurities. For example, potassium hydroxide mainly produced by the electrolytic method contains 0.07 to 0.25% by weight of sodium hydroxide derived from sodium chloride contained in potassium chloride as a raw material. Since potassium and sodium have similar chemical properties, sodium ion cannot be selectively removed by electrolysis of an aqueous potassium chloride solution by the ion exchange membrane method. Conventionally, such trace amounts of sodium ions have not been normally removed and used as they are, but recently, with technological progress in the fields of pharmaceuticals, optical materials, battery materials, and the like, potassium compounds having a low sodium content have been demanded. There is.

As a method for removing sodium ions from an aqueous solution of potassium chloride, a recrystallization method utilizing a difference in solubility between sodium chloride and potassium chloride in water, an ordinary ion exchange membrane electrolytic cell and an intermediate chamber using a cation exchange membrane are used. There is a method of using a three-chamber electrolysis method provided with.

[0004]

However, the above-mentioned recrystallization method has many problems in practical use such as increase in energy consumption and installation of auxiliary equipment, and the three-chamber electrolysis method has a complicated electrolytic cell structure, There is an unavoidable large increase in cost, such as an increase in power consumption. In general, a method using a chelate resin or an ion exchange membrane has a low exchange selectivity between sodium and potassium, and it is difficult to remove a sodium content from a potassium compound containing a small amount of sodium. Recently, removal of sodium ions by the ion-exchange action of crystalline antimonic acid has been proposed (JP-A-61-10025). However, elution of antimony in the ion-exchange step and antimonic acid has a heat-resistant temperature of 400. Since it is as low as ℃, there is a problem that it cannot be used for removing sodium ions in a potassium compound melted at a high temperature. Further, although it shows relatively good sodium ion removal performance in a basic aqueous solution, there is also a problem that the performance is inferior in the neutral to acidic region.

[0005]

The present invention is intended to solve the above problems, that is, a solution or a melt of a potassium compound containing sodium ion contains the crystalline zirconium phosphate represented by the formula (1). A method for purifying a potassium compound, which comprises contacting to remove sodium ions. AZr ₂ (PO ₄ ) ₃ · nH ₂ O (1) (where A is a hydrogen atom or a potassium atom, and n is 0 ≦ n ≦
Represents a numerical value of 2. )

It is known that crystalline zirconium phosphate has an ion exchange capacity, and α-Zr (HPO ₄ ) ₂ .H having an atomic ratio of phosphorus to zirconium (P / Zr) of 2.
₂ O, β-Zr (H ₂ PO ₄ ) (PO ₄ ) · 2H ₂ O,
_{θ-Zr (HPO 4) 2} · 8H 2 O it is generally well known. However, the ion exchange selectivity of these crystalline zirconium phosphates for alkali metals is Li <Na <K
, And the higher the ion concentration, the higher the exchange capacity.
That is, these crystalline zirconium phosphates are not possible in terms of selectivity and concentration to exchange and remove a trace amount of sodium ions in the high concentration potassium compound.

As a result of earnest studies, the present inventors have found that the crystalline zirconium phosphate represented by the formula (1) is specifically superior in ion exchange selectivity to sodium ion as compared with potassium ion.

Crystalline zirconium phosphate represented by the formula (1) (hereinafter referred to as crystalline zirconium phosphate (1))
As exemplified in JP-A-60-239313, zirconium compounds such as zirconium oxychloride and zirconium nitrate, and polycarboxylic acids having two or more carboxyl groups such as oxalic acid, sodium oxalate and maleic acid. Alternatively, it can be obtained by reacting a salt thereof with a water-soluble phosphoric acid compound such as sodium phosphate or a phosphoric acid compound which becomes water-soluble with an acid at a pH of 10 or less.

For example, HZr ₂ (PO ₄ ) ₃ is NH ₄ Zr
₂ (PO ₄ ) ₃ · nH ₂ O (where 0 ≦ n ≦ 2) 400
It can be obtained by heat treatment in the range of up to 1,000 ° C. Further by the HZr ₂ (PO _{4) 3} for water _{treatment, HZr 2 (PO 4) 3} · nH 2 O ( where 0 <
n ≦ 2) is obtained. The crystalline zirconium phosphate (1) thus obtained is chemically and thermally stable and has a NASICON type three-dimensional network structure. Its crystal structure is characterized by an X-ray diffraction pattern with the interplanar spacing (d) shown in the table below.

HZr ₂ (PO ₄ ) ₃ d (angstrom) Specific strength (100 × I / Io) Low temperature type High temperature type 6.41 to 6.30 7 to 68 4.66 to 4.50 100 26 to 100 4. 66-4.38 55-100 100 3.86-3.78 55-128 3.20-3.14 24-82 2.93-2.84 27-83 2.57-2.53 7-60 1 0.99 to 1.97 3 to 40 1.68 to 1.66 5 to 45

HZr ₂ (PO ₄ ) ₃ · nH ₂ O (where 0 <n ≦ 2) d (Angstrom) Specific intensity (100 × I / Io) 6.49 to 6.33 7 to 58 4.73 to 4 .60 45 to 90 4.44 to 4.35 50 to 110 3.86 to 3.80 100 3.23 to 3.17 30 to 85 2.95 to 2.90 25 to 128 2.55 to 2.52 5-45 1.92-1.90 5-45 1.89-1.81 3-44 1.66-1.65 3-40

The HZr ₂ (PO ₄ ) ₃ .nH ₂ O
Is contacted with an aqueous solution of a potassium compound such as potassium hydroxide, potassium chloride or potassium nitrate, filtered and dried to obtain KZr ₂ (PO ₄ ) ₃ · nH ₂ O (where 0 ≦ n ≦
2) can be obtained.

When the solution of the potassium compound to be purified in the present invention is an aqueous solution, potassium bromide, potassium bromate, potassium carbonate, potassium hydrogen carbonate, potassium chloride,
Potassium chlorate, potassium chromate, potassium dichromate, potassium fluoride, potassium phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, potassium iodide, potassium iodate, potassium permanganate, potassium manganate, Examples thereof include inorganic potassium compounds such as potassium nitrate, potassium hydroxide, potassium sulfite, and potassium sulfate; organic potassium compounds such as potassium acetate and potassium oxalate; and mixtures of two or more thereof. Further, these potassium compounds can also be used as a soluble organic solvent solution.

When the potassium compound to be purified is a molten product, the crystalline zirconium phosphate (1) to be used has a heat resistant temperature of 800 ° C., so that the melting point of a single potassium compound or a mixed potassium compound is 800 ° C. or less. The melt can be purified, and examples thereof include potassium bromide, potassium bromate, potassium chloride, potassium chlorate, potassium iodide, potassium iodate, potassium nitrate, potassium hydroxide, potassium thiocyanate, and dipotassium trichloride.

The crystalline zirconium phosphate (1) used for the purification of such a potassium compound may be in the form of powder, granules or fibers, and the treatment method may be a batch method, a column method or any other method. You can choose. Industrially, a method is preferred in which an inorganic or organic binder is used, crystalline zirconium phosphate (1) is granulated to about 0.1 to 10 mm, and a potassium compound solution is continuously treated by a column system packed with this.

When purifying an aqueous solution of a potassium compound,
The amount of crystalline zirconium phosphate (1) used depends on the concentration of the potassium compound in the aqueous solution and the concentration of sodium contained in the aqueous solution, but is usually 5 to 1,000 times the sodium amount (as Na) to be removed, Preferably 10 to 10
It is 0 times the weight. The same applies to the case of the melt.

The treatment temperature can be arbitrarily selected from room temperature to 800 ° C. In the case of an aqueous solution, the higher the temperature, the faster the ion exchange rate. In the case of a melt, the lower the viscosity of the melt is, the more likely it is to come into contact with the crystalline zirconium phosphate (1). Therefore, the treatment at the temperature having the lowest melt viscosity above the melting point and below 800 ° C. is preferable. The treatment time depends on the concentration of sodium as an impurity, but in the case of a batch method, it is usually
The sodium ion can be removed by stirring for 0 to 24 hours.

[0018]

The crystalline zirconium phosphate (1) used in the present invention has a particularly excellent ion exchange selectivity for sodium ions as compared with potassium ions. The excellent selectivity seems to be due to the position and size of the ions in the skeleton of the three-dimensional network skeleton structure of this compound. That is, the size occupied by the ions in the skeleton is optimal for sodium ions, and sodium ions are much easier to exchange ions than potassium ions having a large ion diameter.

[0019]

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples. Example 1 A compositional formula HZr was added to 100 mL of a 48.5 wt% potassium hydroxide aqueous solution having a NaOH concentration of 2,000 ppm.
8 g of crystalline zirconium phosphate (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd., trade name “NZP-100”) represented by ₂ (PO ₄ ) ₃ · 0.1H ₂ O is added, and the mixture is added at 30 ° C. for 1 hour. After stirring, the solution was filtered and the concentration of NaOH in the filtrate was measured by plasma emission spectroscopy.
The amount was reduced to about 1/3.

Example 2 The same crystalline zirconium phosphate (“NZP-100”) as in Example 1 was added to 100 mL of a saturated potassium chloride aqueous solution (KCl 300 g / L) having a NaCl concentration of 1,000 ppm.
g, stirred at 80 ° C for 30 minutes, filtered, and filtered to obtain N in the filtrate.
When aCl was analyzed, it was 200 ppm.

Example 3 200 m of high-purity potassium chloride aqueous solution obtained in Example 2
Crystalline zirconium phosphate in L (“NZP-100”)
After adding 5 g and stirring at 70 ° C. for 2 hours, the powder separated by filtration was subjected to elemental analysis and X-ray diffraction analysis.
It was a crystalline zirconium phosphate represented by ₂ (PO ₄ ) ₃ . When 10 g of this K-type crystalline zirconium phosphate was added to a 25 wt% potassium nitrate aqueous solution having a NaNO ₃ concentration of 800 ppm, the mixture was stirred at 50 ° C. for 3 hours and then filtered, whereby the NaNO ₃ concentration in the filtrate was 25 ppm.

Example 4 100 g of a potassium nitrate melt having a NaNO ₃ concentration of 3,000 ppm was added to crystalline zirconium phosphate (“NZP-10”).
0 ") was added, mixed at 380 ° C for 4 hours and filtered. After cooling the filtered melt, it is dissolved in water and NaNO ₃
Was measured to find that the NaNO ₃ concentration was 1,300 ppm with respect to potassium nitrate. In each of the above Examples, no zirconium was eluted in the purified liquid.

Comparative Example 1 As the crystalline zirconium phosphate, the composition formula Zr (HP
The filtrate was analyzed in the same manner as in Example 2 except that 5 g of O ₄ ) ₂ · H ₂ O (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd., trade name “CZP-100”) was used. However, NaCl in the filtrate was 980 ppm.

Comparative Example 2 As crystalline zirconium phosphate, the composition formula Zr (HP
O _{4) 2} · 2H ₂ O (Daiichi Kigenso Kagaku Kogyo Co., Ltd., except that trade name "CZP-200") was used 5g, similarly quite as in Example 2, were analyzed for the filtrate However, NaCl in the filtrate was 970 ppm.

Comparative Example 3 Instead of crystalline zirconium phosphate, the composition formula HZr ₂ (P
The analysis of the filtrate was carried out in the same manner as in Example 2 except that 5 g of amorphous zirconium phosphate represented by O ₄ ) ₃ · H ₂ O was used. As a result, NaCl in the filtrate was 920 ppm.
Met.

[0026]

EFFECTS OF THE INVENTION According to the present invention, it is possible to efficiently remove the sodium content in an aqueous solution of potassium chloride used as a raw material for producing potassium hydroxide or in the produced aqueous solution of potassium hydroxide. Further, the present invention can be applied to the purification of various potassium compounds containing other sodium components, and can also effectively remove the sodium components in the high temperature potassium nitrate melt used for the surface treatment of glass. This is a great feature. Therefore, it has great utility in the field of high-purity potassium compounds required as raw materials for pharmaceuticals, optical materials, battery materials and the like.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tomihiko Yamamoto 77 Kitayoshida-cho, Matsuyama-shi, Ehime Prefecture (72) Inventor Katsuhiko Ito 134-2 Nishiwaki, Iwaoka-cho, Nishi-ku, Kobe-shi, Hyogo

Claims (3)

[Claims] 1. A method for purifying a potassium compound, which comprises contacting a solution or a melt of a potassium compound containing sodium ion with the crystalline zirconium phosphate represented by the formula (1) to remove the sodium ion. AZr ₂ (PO ₄ ) ₃ · nH ₂ O (1) (where A is a hydrogen atom or a potassium atom, and n is 0 ≦ n ≦
Represents a numerical value of 2. ) 2. The method for purifying a potassium compound according to claim 1, wherein the solution of the potassium compound is an aqueous solution. 3. The melting point of the potassium compound is 800 ° C.
The method for purifying a potassium compound according to claim 1, which is the following melt.