KR101316335B1 - Method of solvent extraction for separation of zirconium and hafnium - Google Patents

Abstract

The present invention relates to the separation of zirconium and hafnium in aqueous solution to the solvent extraction process, hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) by giving to the ion adding the two dramatically improve the degree of separation between the metal and which may enhance the zirconium recovery It relates to a solvent extraction method.

Description

Solvent Extraction Method for Separation of Zirconium and Hafnium {METHOD OF SOLVENT EXTRACTION FOR SEPARATION OF ZIRCONIUM AND HAFNIUM}

The present invention relates to the separation of zirconium and hafnium in aqueous solution to the solvent extraction process, hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) was added to ion to by giving the two relates to the solvent extraction method which can dramatically improve the degree of separation between the metal will be.

Zirconium (Zr) is a metal used in various industrial fields, including nuclear power generation, in the form of various special alloys, oxides and other compounds. Zirconium (Zr) is known as an essential material for nuclear fuel cladding, corrosion resistant machinery, metals and precision ceramics. Recently, due to the rapid expansion of the domestic industrial scale, the demand for zirconium is also rapidly growing.

In the case of zircon sand, a raw material mineral of zirconium, casting sand and refractory materials account for about 70% of the total demand, and the rest is used as abrasives and ceramic enamel raw materials.

The average content of zirconium in the earth's crust is about 0.025%, and about 20 species of zirconium are known to date. Most of the zirconium minerals contain hafnium (Hf) at the same time, and these zirconium (Zr) and hafnium (Hf) are known to be very difficult to separate from each other because of their similar physical and chemical properties. Nevertheless, high purity zirconia (ZrO ₂ ) and metal zirconium (Zr) must be separated from zirconium (Zr) and hafnium (Hf) in order to produce from the mineral. In particular, the metal zirconium (Zr) used in the reactor can not exceed 100 ppm of hafnium (Hf), and the high purity zirconia compound, which is a raw material of advanced ceramic materials, also regulates the incorporation of hafnium (Hf). Separation of hafnium (Hf) is essential.

Zirconium (Zr) / hafnium (Hf) separation is generally divided into separation methods in aqueous and nonaqueous phases. Separation in the aqueous phase includes a solvent extraction method and an ion exchange resin method. In addition, the separation method in the non-aqueous liquid phase includes a distillation method and other chemical separation methods.

Documents published so far in connection with the zirconium (Zr) / hafnium (Hf) separation method include US Patent Nos. 5,176,878, 5,132,016 and 4,578,165, and Japanese Patent Application Publication Nos. 2010-075908 and 2008-. 115063, and the like. The most commonly used method of the zirconium (Zr) / hafnium (Hf) separation method is the solvent extraction method, the extractant for zirconium (Zr) / hafnium (Hf) separation is MIBK (Methyl isobutyl ketone), TBP ( Tributyl phosphate) and the like are known.

However, in the case of the solvent extraction method, the degree of mutual separation between zirconium and hafnium is not so high, and a multi-stage separation facility is required to remove hafnium content in zirconium to a desired level. As a result, it is pointed out that the process cost of operating the multi-stage separation facility as well as the increase in device cost is considerably high. In addition, the zirconium loss is inevitably generated in order to sufficiently remove the hafnium, the zirconium recovery is relatively low as 80% or less.

There is a need to overcome the problems of the zirconium (Zr) / hafnium (Hf) separation method and to effectively remove hafnium, but there are still solvents that can significantly improve the zirconium (Zr) / hafnium (Hf) separation. No extraction method has been developed.

5,176,878, "Zirconium-hafnium separation process" 5,132,016, "Solvent prestripping in a Zr / Hf separation liquid-liquid extraction (LLX) circuit" No. 4,578,165, "Process for separation of zirconium from hafnium" JP 2010-075908, "Separation Method of Zirconium and Hafnium" Japanese Laid-Open Patent No. 2008-115063, "Method for Producing the Material Using High Purity Hafnium Material and Solvent Emission Method"

In order to solve the problems of the prior art, in the present invention to separate the zirconium and hafnium in the aqueous solution by the solvent extraction method, by greatly improving the separation between the two metals zirconium is very simple and economical compared to the conventional multi-stage extraction method We propose a solvent extraction method that can separate hafnium.

An object of the present invention is to separate the zirconium and hafnium in the aqueous solution by a solvent extraction method, a solvent extraction method for separating zirconium and hafnium and increasing the recovery rate of zirconium compared to the conventional multi-stage extraction method, very simple and economical, the two metals It is to provide a method for dramatically increasing the separation of liver.

In order to achieve the above object, the present invention relates to a method for separating zirconium (Zr) and hafnium (Hf). More specifically, the present invention is zirconium (Zr) and hafnium aqueous solution of hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) in the containing (Hf) adding the ion, and adding the extractant to the aqueous solution and extract the zirconium solvent It provides a method for separating zirconium (Zr) and hafnium (Hf) comprising a step.

When the zirconium and hafnium in the aqueous solution is separated by the solvent extraction method by the method of the present invention, the zirconium and hafnium can be separated very simply and economically compared to the conventional multi-stage extraction method by dramatically increasing the separation between the two metals. . That is, hafnium can be effectively removed by only one-stage batch extraction without the conventional continuous multi-stage extraction operation, which can drastically reduce the initial investment cost for the installation of the multi-stage extraction facility as well as the time and cost required for continuous operation. Will be. Particularly, in the conventional method, a significant amount of zirconium loss occurs because the zirconium recovery is 80% or less, but the method of the present invention has a feature that the zirconium recovery is 95% or more, which greatly reduces the zirconium loss.

The solvent extraction method for separating the zirconium and hafnium of the present invention will be described in more detail.

The separation of zirconium (Zr) and hafnium (Hf) according to the invention is zirconium (Zr) and hafnium (Hf) aqueous solution of hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) in including a step of adding an ion, and Mixing the extractant in the aqueous solution comprises the step of solvent extraction of zirconium.

The aqueous solution containing zirconium (Zr) and hafnium (Hf) means a state in which zirconium (Zr) and hafnium (Hf) are dissolved in water. Here, dissolution means that zirconium and hafnium exist in an ionic state in water.

The hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) to mix before the addition of the ion, nitric acid in an aqueous solution containing zirconium and hafnium (Nitric acid) is preferred.

When nitric acid is added to the aqueous solution, the nitric acid concentration is preferably 8 10 mol / L. A nitric acid concentration of 8 mol / L or more is advantageous for increasing the zirconium extraction rate, and a nitric acid concentration of 10 mol / L or less is advantageous for further increasing the separation of zirconium and hafnium.

In the present invention, when the hypophosphite ions are added to the aqueous solution, complexes are formed with the zirconium and hafnium ions in the aqueous solution. Zirconium-hypophosphate complexes have the effect of greatly increasing the extraction rate, while hafnium-hypophosphate complexes have the effect of greatly suppressing the extraction rate, ultimately improving the degree of separation.

In the addition amount of the hypophosphite ion, it is preferable to add 1.2 times the molar ratio of the total content of zirconium and hafnium in the aqueous solution. If the addition amount of hypophosphite ion is lower than the above range, there is a problem that the separation degree of zirconium and hafnium falls, and if it is higher than the above range, there is a problem that the consumption of chemicals increases unnecessarily.

In the present invention, any salt that can form a complex compound with zirconium and hafnium in the aqueous solution including the hypophosphite ion can be used without limitation. For example, sodium hypophosphite (NaH ₂ PO ₂ ) or potassium hypophosphite (Potassium hypophosphite, KH ₂ PO ₂ ) may be used, but sodium hypophosphite is much more advantageous in terms of price.

Next, an extractant is added to the aqueous solution to which the hypophosphite ion was added, and zirconium is solvent-extracted. The extractant is not particularly limited, and various kinds of organic compounds may be used as the extractant. The amount of the extractant may be selected by a person skilled in the art according to the type of extractant, and the extractant may be used by diluting at a predetermined ratio using a diluent such as Kerosene.

In the present invention, it is preferable to use TEHP (Tris (2-ethylhexyl) phosphate) as the extractant. When using TriHP (2-ethylhexyl) phosphate (TEHP), it may be used in a volume ratio of 0.3: 0.7 to 0.7: 0.3, preferably 1: 1.

In the solvent extraction process of the zirconium, it is preferable to maintain the temperature in the range 60 90. It is preferable to stir an aqueous solution in the solvent extraction process of the said zirconium. The extraction time may take about 1 hour before or after vigorously stirring the aqueous solution and the extractant, which may be adjusted by those skilled in the art depending on the reaction conditions. If the extraction temperature is lower than the above-mentioned range, the zirconium extraction rate is lowered. If the extraction temperature is higher than the above-mentioned range, the energy cost is excessive and the extractant is lost while evaporating.

After extracting zirconium by the solvent extraction step, the method according to the invention may further comprise the step of separating the aqueous solution and the extractant. The separation step can be carried out by stopping the stirring and letting it stand for phase separation.

In addition, the zirconium in the extractant separated above may be back extracted with water to recover the zirconium. However, in the present invention, there is no particular limitation on the method of back extracting zirconium in the extractant with water, and a conventional back extraction method is sufficient. For example, it can extract back by setting the volume ratio of water and extractant to 1: 1. TEHP may be used as the extractant.

Hereinafter, the specific conditions and features of the present invention targeting the actual zirconium aqueous solution will be described in detail through the following examples. However, the following examples are provided to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example  One

Sodium hypophosphite was added twice in a molar ratio to the total content of zirconium and hafnium in 1 liter of an aqueous solution of 12,250 mg / L of zirconium, 270 mg / L of hafnium, and 8 mol / L of nitrate. 1 liter of the zirconium solution and 1 liter of TEHP (Tris (2-ethylhexyl) phosphate) were added to a reactor and the temperature was raised to 60 ° C. After the temperature was reached, zirconium was extracted for 1 hour while vigorously stirring the aqueous solution and TEHP with a stirrer. After the extraction, the mixture was left to stand and the aqueous solution and TEHP were separated. On the other hand, zirconium and hafnium extracted in TEHP are back-extracted with the volume ratio of water and TEHP 1: 1. After the back extraction was completed, the zirconium and hafnium contents were collected and analyzed using an ICP Spectrophotometer (manufacturer: Thermojarrell Ash, model name: Polyscan 61E), and were 11,800 mg / L and 1.1 mg / L, respectively. Thus, the final zirconium recovery was 96.3% (= 11,800 / 12,250) and the hafnium content in zirconium was significantly reduced from the initial value of 21,565 ppm (= 270 / (12,250 + 270)) to 93.2 ppm (= 1.1 / (11,800 + 1.1)). appear.

Example  2

In the same manner as in Example 1, sodium hypophosphite was added 1.2 times the total content of zirconium and hafnium in 1 liter of an aqueous solution of 12,250 mg / L of zirconium, 270 mg / L of hafnium, and 10 mol of nitrate. Added. 1 liter of the zirconium aqueous solution and 1 liter of TEHP (Tris (2-ethylhexyl) phosphate) were put in a reactor and the temperature was raised to 90 degrees Celsius. After the temperature was reached, zirconium was extracted for 1 hour while vigorously stirring the aqueous solution and TEHP with a stirrer in the same manner as in Example 1. After the extraction, the mixture was left to stand and the aqueous solution and TEHP were separated. On the other hand, zirconium and hafnium extracted in TEHP were back extracted with a volume ratio of water and TEHP of 1: 1. After the back extraction was completed, the zirconium and hafnium contents were collected and analyzed using an ICP Spectrophotometer (manufacturer: Thermojarrell Ash, model name: Polyscan 61E), and were 11,960 mg / L and 1.2 mg / L, respectively. Thus, the final zirconium recovery was 97.6% (= 11,960 / 12,250) and the hafnium content in zirconium was significantly reduced from the initial value of 21,565 ppm (= 270 / (12,250 + 270)) to 100.3 ppm (= 1.2 / (11,960 + 1.2)). Appeared.

Comparative Example  One

1 liter of an aqueous solution of 12,250 mg / L of zirconium content, 270 mg / L of hafnium content and 8 mol of nitrate, and 1 liter of Tris (2-ethylhexyl) phosphate (TEHP) without sodium hypophosphite Into the reactor together, the temperature was raised to 60 degrees Celsius. After the temperature was reached, zirconium was extracted for 1 hour while vigorously stirring the aqueous solution and TEHP with a stirrer in the same manner as in Example 1. After the extraction, the mixture was left to stand and the aqueous solution and TEHP were separated. On the other hand, zirconium and hafnium extracted in TEHP were back extracted with a volume ratio of water and TEHP of 1: 1. After the back extraction was completed, zirconium and hafnium contents were collected and analyzed using an ICP Spectrophotometer (manufacturer: Thermojarrell Ash, model name: Polyscan 61E), and were found to be 8,160 mg / L and 21 mg / L, respectively. Thus, the final zirconium recovery was only 66.6% (= 8,160 / 12,250), and the hafnium content in the zirconium was 2,567 ppm (= 21 / (8,160 + 21)). It was found to be poor.

Comparative Example  2

1 liter of an aqueous solution of 12,250 mg / L of zirconium content, 270 mg / L of hafnium content and 10 mol of nitrate concentration, which is the same as that of Example 2, was added to 1 liter of tris (2-ethylhexyl) phosphate (TEHP) without sodium hypophosphite. Into the reactor together, the temperature was raised to 90 degrees Celsius. After the temperature was reached, zirconium was extracted for 1 hour while vigorously stirring the aqueous solution and TEHP with a stirrer in the same manner as in Example 1. After the extraction, the mixture was left to stand and the aqueous solution and TEHP were separated. On the other hand, zirconium and hafnium extracted in TEHP were back extracted with a volume ratio of water and TEHP of 1: 1. After the back extraction was completed, the zirconium and hafnium contents were collected and analyzed using an ICP Spectrophotometer (manufacturer: Thermojarrell Ash, model name: Polyscan 61E), and were found to be 8,350 mg / L and 23 mg / L, respectively. Thus, the final zirconium recovery was only 68.2% (= 8,350 / 12,250), and the hafnium content in zirconium was 2,747 ppm (= 23 / (8,350 + 23)), which is significantly lower than that of Example 2 It was found to be poor.

Claims (9)

Zirconium (Zr) and hafnium aqueous solution of hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) in the containing (Hf) adding the ion, and
Separation method of zirconium (Zr) and hafnium (Hf) comprising the step of adding an extractant to the aqueous solution and zirconium solvent extraction.
2. The method of claim 1, wherein hypophosphorous acid ^{_{(Hypophosphite, H 2 PO 2 -}} ) prior to the ion added, zirconium (Zr) and hafnium comprising the step of adding nitric acid to an aqueous solution containing zirconium and hafnium (Hf ) Separation method
The method of separating zirconium (Zr) and hafnium (Hf) according to claim 2, wherein the concentration of nitric acid in the aqueous solution is 8 10 mol / L.
2. The method of claim 1, wherein the hypophosphite ion is added at a molar ratio of 1.2 to the total content of zirconium and hafnium in an aqueous solution.
The method for separating zirconium (Zr) and hafnium (Hf) according to claim 1, wherein the hypophosphite ion is added using sodium hypophosphite or potassium hypophosphite.
The method of claim 1, wherein the extracting agent is TEHP (Tris (2-ethylhexyl) phosphate) is separation method of zirconium (Zr) and hafnium (Hf).
The method of claim 1, wherein zirconium (Zr) and hafnium (Hf) to maintain the temperature during the solvent extraction in the range of 60 to 90 degrees Celsius.
The method of claim 1, further comprising, after the solvent extraction, separating the aqueous solution and the extractant.
The method of claim 8, further comprising back-extracting zirconium in the separated extractant with water.