JP5247986B2 - Manufacturing method of high purity iron oxide - Google Patents

Description

The present invention relates to a process for producing a high purity oxidation of iron.

  High purity iron is used in the fields of semiconductor elements, electronic devices, recording elements and the like. The purity of high-purity iron used for this purpose is usually on the order of 99.9 to 99.99%. However, due to the recent high integration of these elements and the manufacture of new structural elements, it is preferable due to various impurities (heavy metal, alkali metal, alkaline earth metal, or ions thereof) slightly contained in high-purity iron. There is a need for higher purity iron. Such high-purity iron means that the purity of iron is at least 99.9995% or more, and the content of certain undesirable impurities (heavy metal, alkali metal, alkaline earth metal, or ions thereof) is higher than a predetermined concentration. It is guaranteed to be low.

  Conventional methods for producing high-purity iron include, for example, separation of metal elements by wet treatment such as solvent extraction, ion exchange, or electrolytic purification, removal of gaseous elements such as oxygen by dry hydrogen gas treatment, or float zone melt. There is a purification method. However, these methods have a problem that it is difficult to control and it is difficult to stably supply high-purity iron on an industrial scale.

The crude iron material is treated with hydrochloric acid and oxidized to an acidic aqueous hydrochloric acid solution containing iron (3+) ions. The solution is subjected to ion exchange chromatography to remove impurities such as copper ions, and then evaporated to dryness to obtain iron oxide. A method of reducing to high purity iron is known (Patent Document 1). However, this method has a problem in terms of cost and working environment because it includes an excessively expensive process of heating and evaporating and drying an aqueous iron chloride solution, and further, hydrogen chloride gas is released.
JP 2002-105598 A

The present invention aims to provide a manufacturing method of a preferred high purity oxidation of iron in the production of high purity iron or 99.9995% pure.

  As a result of diligent research to develop a method for producing high-purity iron having a purity of 99.9995% or more in a low-cost, large-scale and environmentally friendly condition, the present inventors have heated and evaporated an acidic iron chloride aqueous solution. Instead of the traditional process of drying to iron oxide, certain unfavorable impurities (heavy metal, alkali metal, or alkaline earth metal by neutralizing acidic aqueous iron chloride solution with alkaline aqueous solution under specific conditions , Or their ions) is lower than a predetermined concentration, and iron hydroxide is obtained as a solid precipitate, and this high-purity iron hydroxide is used to oxidize and reduce to iron oxide. Thus, it has been found that high-purity iron can be obtained at low cost under environmentally friendly conditions, and the present invention has been completed.

That is, the present invention prepares an aqueous solution of iron chloride by dissolving scrap iron with hydrochloric acid and then oxidizing it. The obtained aqueous solution of iron chloride is subjected to ion exchange chromatography to remove heavy metal impurities, and then added with an aqueous alkaline solution. The resulting high purity iron hydroxide is prepared by separating and drying the precipitate, and then the obtained high purity iron hydroxide is heated at a temperature of 500 to 700 ° C. in an oxygen atmosphere. It is related with the manufacturing method of high purity iron oxide characterized by baking for 6 to 12 hours.

Furthermore, the present invention is characterized in that the neutralization precipitation treatment is performed by adding an aqueous iron chloride solution and an alkaline aqueous solution simultaneously to water in a reaction vessel in which the pH is maintained at 9-10. the method for producing a high purity oxidation of iron.

Furthermore, the present invention, the alkali aqueous solution, aqueous ammonia solution, aqueous methylamine, relates to a method for producing high purity acids of iron which is characterized in that any one of trimethylamine aqueous solution.

The present invention also includes the high- purity iron oxide produced by the present invention and the high- purity iron produced using the same.

The production method of the present invention is superior in terms of cost and environment as compared with the heat evaporation treatment (dry method) in the step of converting the aqueous iron chloride solution to iron oxide.

  The best mode for carrying out the invention will be described below with reference to the drawings.

  FIG. 1 shows one conventionally known method for producing high-purity iron. First, scrap iron, etc., which is a raw material, is dissolved in hydrochloric acid and oxidized to form a ferric chloride aqueous hydrochloric acid solution (hereinafter referred to as “iron chloride aqueous solution”). Metal ions, which are impurities, are removed by appropriate ion exchange chromatography. Further, the obtained aqueous iron chloride solution is evaporated to dryness by heating to form iron oxide. High purity iron can be obtained by reducing iron oxide.

  In such a method, the heat evaporation process (dry process) in the process of converting the aqueous iron chloride solution to iron oxide requires excessive energy, and hydrogen chloride gas is generated in the environment during the process.

  On the other hand, as shown in FIG. 2, the method according to the present invention is greatly different in that it employs a step of wet-treating an aqueous iron chloride solution. This process provides significant advantages in terms of cost and environment as compared to conventional methods. This will be described in detail below.

FIG. 2 shows one general flow of a method for producing high-purity iron using the present invention. The process of dissolving scrap iron as raw material with hydrochloric acid, the step of oxidizing iron ions dissolved in hydrochloric acid to make an aqueous solution of iron chloride, and the resulting aqueous solution of iron chloride by ion-exchange chromatography for impurity metal ions Etc., the step of neutralizing and precipitating the obtained aqueous iron chloride solution with an alkaline aqueous solution to precipitate iron hydroxide, and separating the resulting precipitate and drying to obtain high-purity iron hydroxide It comprises a step, a step of oxidizing the obtained high purity iron hydroxide to obtain a high purity iron oxide, and a step of reducing the obtained high purity iron oxide to obtain a high purity iron.

The step of removing the impurity metal ions and the like by subjecting the obtained aqueous iron chloride solution to ion exchange chromatography is not essential, and can be appropriately selected depending on the type and amount of impurities. Hereinafter, each process will be described in detail.
(Process to dissolve scrap iron as raw material by treating with hydrochloric acid)
Scrap iron as a raw material that can be used in the present invention is not particularly limited, and can be used as long as the purity of the iron is 99.0 to 99.9%. Moreover, it can be used even if other metal ions usually contained as impurities are contained.

Although there is no restriction | limiting in particular also about the hydrochloric acid which melt | dissolves raw material scrap iron, The thing which does not contain an impurity as much as possible is preferable. Examples of impurities include heavy metals, alkali metals, alkaline earth metals, and the like. A commercially available hydrochloric acid solution can be used as it is. It is also preferable to adjust by blowing high purity hydrochloric acid gas into high purity water. The concentration of hydrochloric acid is not particularly limited as long as the raw scrap iron is sufficiently dissolved. Preferably it is about 4-6 mol / L. There is no particular limitation on the dissolution method, and it is preferable to dissolve the solution little by little with stirring using a container of a material and a shape that prevents impurities from being mixed and does not dissolve the impurity metal from the container wall.
(Step of oxidizing iron ions dissolved in hydrochloric acid to make an aqueous solution of iron chloride)
The aqueous iron chloride solution obtained above first dissolves in the form of iron (2+) ions, but is converted to iron (3+) ions by oxygen in the air. In order to complete this oxidation, it is preferable to actively oxidize with an oxidizing agent. The oxidizing agent is not particularly limited as long as it can oxidize iron (2+) ions to iron (3+) ions in an acidic aqueous solution, and various inorganic and organic oxidizing agents can be used. Examples of the inorganic oxidizing agent include hydrogen peroxide water, chlorine gas, and ozone. In particular, the use of hydrogen peroxide water is preferable. The oxidizing agent may be put in the water of the reaction vessel from the beginning, or may be added during the reaction. Whether or not the oxidation has completely progressed can be easily determined by a change in the color of the reaction solution.

  The obtained aqueous iron chloride solution can be used in the next step as it is. If necessary, it can be diluted to an appropriate concentration and subjected to ion exchange column chromatography to remove impurity metal ions and the like.

Moreover, it is preferable to perform elemental analysis of the aqueous iron chloride solution obtained before the next step. The method of elemental analysis is not particularly limited, but it is preferable to use a method and apparatus in which the detection limit of iron, other heavy metals, alkali metals, and alkaline earth metals is about 1 ppt. Specific examples include an inductively coupled plasma mass spectrometer (ICP-MS).
(Process of ion exchange chromatographic treatment of iron chloride aqueous solution)
In the present invention, it is preferable to reduce the concentration of impurities by ion exchange chromatography before neutralizing and precipitating the obtained aqueous iron chloride solution. For the ion exchange chromatograph used for this purpose, various publicly known methods can be used. When the impurities to be specifically removed are divalent cations (copper ions, nickel ions, etc.), it is possible to use a known anion exchange chromatograph (Thin Solid Films 461 (2004) 94-). 98).
(Step of neutralizing and precipitating iron chloride aqueous solution with alkaline aqueous solution to precipitate iron hydroxide)
The present invention is particularly characterized in that the aqueous iron chloride solution prepared above is wet-processed, that is, precipitated and separated as a hydroxide while neutralizing with an aqueous alkaline solution. By this treatment, iron ions become insoluble solid precipitates (powder) of iron hydroxide and other impurities (other metal ions, etc.) remain dissolved in the reaction solution, so that only iron can be easily separated. Is possible. The pH of the aqueous solution during the reaction is not particularly limited as long as iron ions are in an insoluble hydroxide, and may be in the range of 8 or more. In the present invention, it is preferable that iron hydroxide is sufficiently separated from the reaction solution to generate a precipitate, and is maintained at 9 to 10 as a condition that impurities are not mixed into the precipitate.

  The alkaline aqueous solution that can be used for neutralization is not particularly limited, but preferably has a high purity. In particular, it is preferable to avoid mixing of various alkali metals and alkaline earth metals from the alkaline aqueous solution. Specific examples of the alkaline aqueous solution that can be used in the present invention include an aqueous sodium hydroxide solution, an aqueous ammonia solution, and an aqueous methylamine solution. It is possible to use a high-purity sodium hydroxide aqueous solution that is commercially available for semiconductor production, or it can be prepared by dissolving high-purity sodium or high-purity sodium hydroxide in high-purity water. . When sodium, potassium, and magnesium are not problematic as impurities contained in high-purity iron, an aqueous sodium hydroxide solution can be preferably used as the alkaline aqueous solution. When sodium, potassium, or magnesium is a problem as an impurity contained in high-purity iron, an aqueous ammonia solution, an aqueous methylamine solution, particularly an aqueous ammonia solution can be preferably used as the alkaline aqueous solution. Although there is no restriction | limiting in particular also about the density | concentration of aqueous alkali solution, What is necessary is just the range of 5-8 mol / L.

  Further, in the present invention, there is no particular limitation on the type of reaction between the aqueous iron chloride solution and the alkaline aqueous solution, but a method in which both aqueous solutions are simultaneously added to the water in the reaction vessel is preferable. There is no particular limitation as long as the addition rate is in the range of 15.0 to 25.0 ml / min. When added at a rate larger than this range, impurities may be taken into the produced precipitate. The reaction solution in the reaction vessel is preferably sufficiently stirred with a stirring device. After completion of the reaction, it is preferable to continue stirring for a while in order to sufficiently mature the precipitate. Although there is no restriction | limiting in particular also about reaction temperature, It is preferable to maintain the range of 30-50 degreeC.

The neutralization reaction type is not particularly limited, and can be either a batch type or a continuous type. In the case of the continuous type, the generated iron hydroxide precipitate can be continuously taken out by the overflow pipe provided in the reaction apparatus, so that it can be carried out more efficiently.
(Step of separating the obtained precipitate and drying it to make high purity iron hydroxide)
The iron hydroxide precipitate obtained above can be easily separated from the reaction solution by various methods. A method by decantation or filtration using a filter is possible. Impurity ions mixed in the form of a solution during precipitation can be easily washed away by sufficiently washing several times with high-purity water.

The obtained iron hydroxide precipitate can be sufficiently dried by an ordinary drying method. Specifically, it is held at 50 to 70 ° C. for 10 to 20 hours in a vacuum drying apparatus.
(Step of oxidizing the resulting high-purity iron hydroxide to high-purity iron oxide)
The obtained high-purity iron hydroxide can be easily made into high-purity iron oxide by using a normal oxidation treatment method. Specifically, it can be performed by baking at 500 to 700 ° C. for 6 to 12 hours in an oxygen atmosphere.
(Step of reducing the obtained high purity iron oxide to high purity iron)
The obtained iron oxide can be easily made into high-purity iron using a normal reduction treatment method. Specifically, a method of heating at 800 ° C. in a hydrogen gas atmosphere can be used.

  Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to these examples.

Scrap iron was used as a raw material in the following examples and comparative examples. For elemental analysis of iron chloride and iron oxide, ICP-MS (Optima 4300 DV manufactured by PerkinElmer) was used, and the measurement data was a value obtained as the concentration of each element measured with respect to iron (concentration of each element measured = total amount of each element measured) / Total amount of iron). Moreover, the glow element mass spectrometry (Glow Discharge Mass Spectroscopy) was used for the elemental analysis of iron.
Example 1
400 g of raw scrap iron was pulverized and dissolved in 8 L of 35% hydrochloric acid (manufactured by Kanto Chemical Co., product number 18078-80). Thereafter, 12 L of distilled water was added to make the total volume 20 L. Thereafter, 500 ml of 35% hydrogen peroxide solution (manufactured by Ube Chemilla Co., Ltd.) was slowly added and stirred. The color of the aqueous solution changed from light blue to dark yellow. The results of elemental analysis of the obtained aqueous iron chloride solution are shown in Table 1 below.

  A 15 L volume vinyl chloride cylindrical container (radius 13 cm, height 25 cm) was used as a reaction vessel. 3 L of ion-exchanged distilled water was added to the reaction tank, the temperature of the water in the reaction tank was controlled at 40 ° C., and the pH was maintained at 10 with a pH controller. Further, a propeller-shaped stirrer having a radius of 3.5 cm was fixed to the center of the reaction vessel at a rotation speed of 400 rpm and stirred.

  To this reaction vessel, 8 L of iron chloride aqueous solution and 1 L of 28% ammonia aqueous solution (manufactured by Kanto Chemical Co., Ltd., special grade, product number 01266-80) were simultaneously added over 6 hours using a quantitative dropping device. The dropping rate of the aqueous iron chloride solution was 23 ml / min.

  A reddish brown precipitate formed with the addition.

  Thereafter, washing with decantation water was performed twice, followed by filtration and separation using a suction filter. The obtained precipitate was dried at about 60 ° C. under vacuum for 10 hours to obtain 306 g of iron hydroxide.

  760 g of the obtained iron hydroxide was calcined in an oxidation furnace apparatus at 650 ° C. for 10 hours in an air atmosphere to obtain 1145 g of iron oxide. Table 2 shows the elemental analysis results of the obtained iron oxide.

  From the measured values, the purity of iron oxide was 99.988%, and the contents of aluminum, magnesium and sodium were all 1 ppm or less.

  1145 g of the obtained iron oxide was reduced by heating at 800 ° C. for 10 hours in a hydrogen atmosphere using a reduction furnace apparatus to obtain 400 g of iron.

  Moreover, when the energy cost was calculated using the equation shown in the following equation 1, the energy cost required to make 1 kg of high-purity iron compound by the evaporation to dryness method could be reduced to about 1/4 times (see Table 1). 3).

Q = {W × H × E} / Fe
Q: Energy cost required to make 1kg of high-purity iron compound (yen)
W: Power consumption (kW)
H: Processing time (hr)
E: Unit price (yen / kW)
Fe: Iron processing amount (kg)
* The iron concentration of the iron chloride used was 25 g / L.

（実施例２）
実施例１で使用したアンモニア水溶液に代えて、水酸化ナトリウム水溶液を使用したこと以外は実施例１と同様の条件で行った。ここで水酸化ナトリウム水溶液は半導体用高純度グレードを使用した（鶴見曹達株式会社製、製品名ＣＬＥＡＲＣＵＴ−Ｓ）。

(Example 2)
It replaced with the ammonia aqueous solution used in Example 1, and carried out on the conditions similar to Example 1 except having used the sodium hydroxide aqueous solution. Here, a high-purity grade for semiconductor was used as the aqueous sodium hydroxide solution (product name CLEARCUT-S, manufactured by Tsurumi Soda Co., Ltd.).

  Table 4 shows the elemental analysis results of the obtained iron oxide.

From the measured values, the purity of iron oxide was 99.948%, and the contents of aluminum and magnesium were both 1 ppm or less. On the other hand, the sodium content was 374 ppm.
(Example 3)
The iron chloride aqueous solution 20L prepared in Example 1 was passed through an anion exchange resin 30L (Mitsubishi Chemical Corporation, product name DIAION SA10A, packed in a 12 cm diameter vinyl chloride column) to adsorb iron ions and other elements. Separated from ions. Next, iron ions were eluted with an eluent (concentration: 1 mol / L hydrochloric acid). Elemental analysis of the obtained eluent is shown in Table 5 below.

  The obtained iron ion eluent 8L was used for the next neutralization precipitation. Neutralization precipitation was performed in the same manner as in Example 1. In addition, the obtained iron hydroxide was oxidized to iron oxide and reduced from iron oxide to iron in the same manner as in Example 1.

  The elemental analysis results of the obtained iron oxide and iron are shown in Tables 6 and 7, respectively.

測定値から酸化鉄の純度は９９．９９８％であり、かつ重金属、マグネシウム、ナトリウムの含有量はいずれも１ｐｐｍ以下であった。

From the measured values, the purity of iron oxide was 99.998%, and the contents of heavy metals, magnesium, and sodium were all 1 ppm or less.

Moreover, the purity of iron was 99.9998%, and cobalt and copper were 1 ppm or less, but other metals were 0.1 ppm or less.
(Comparative Example 1)
500 ml of an aqueous iron chloride solution was placed in a 1000 ml cylindrical beaker made of Teflon placed on a hot plate. This was heated to obtain black crystalline iron oxide. The elemental analysis of the obtained iron oxide is shown in Table 8.

測定値から酸化鉄の純度は、９９．９９８％であり、かつカルシウムとシリカ以外の金属元素は２ｐｐｍ以下であった。
（実施例４） 連続法による中和沈殿処理１
攪拌機付きの反応槽に水３Ｌを入れ、ｐＨ制御計によりｐＨを１０に調整した。ここへ鉄濃度が２０ｇ／Ｌの塩化鉄水溶液と、４８％の水酸化ナトリウム水溶液を反応槽内のｐＨが自動的に１０に維持されるように投入した。塩化鉄水溶液の投入流速は２３ｍｌ／分であった。また、反応槽内の温度は４０℃に維持し、攪拌機で常に攪拌した。生成した水酸化鉄はオーバーフロー管よりオーバーフローさせて取り出し、水洗、脱水、乾燥処理した。このようにして、高純度水酸化鉄粉末を得た。
（実施例５） 連続法中和沈殿処理２
同様に水酸化ナトリウム水溶液に替えて、２８％のアンモニア水溶液を用いた。他は上と同様に行い高純度水酸化鉄粉末を得た。

From the measured values, the purity of iron oxide was 99.998%, and the metal elements other than calcium and silica were 2 ppm or less.
(Example 4) Neutralization precipitation treatment 1 by a continuous method
3 L of water was placed in a reaction vessel equipped with a stirrer, and the pH was adjusted to 10 with a pH controller. An iron chloride aqueous solution having an iron concentration of 20 g / L and a 48% sodium hydroxide aqueous solution were added thereto so that the pH in the reaction vessel was automatically maintained at 10. The input flow rate of the iron chloride aqueous solution was 23 ml / min. Moreover, the temperature in a reaction tank was maintained at 40 degreeC, and was always stirred with the stirrer. The produced iron hydroxide was taken out by overflowing from the overflow pipe, washed with water, dehydrated and dried. In this way, high purity iron hydroxide powder was obtained.
(Example 5) Continuous process neutralization precipitation process 2
Similarly, a 28% aqueous ammonia solution was used in place of the aqueous sodium hydroxide solution. The others were carried out in the same manner as above to obtain high-purity iron hydroxide powder.

The present invention, preparation of suitable purity oxidation of iron in the production of high purity iron over 99.9995% of purity at a low cost, thereby enabling the condition environmentally friendly.

FIG. 1 is a diagram showing a conventional method for producing high-purity iron. Figure 2 is a diagram showing a manufacturing method of high purity oxidation iron according to the invention.

Claims (4)

An aqueous iron chloride solution is prepared by dissolving scrap iron with hydrochloric acid and then oxidizing it,
The obtained aqueous iron chloride solution is subjected to ion exchange chromatography to remove heavy metal impurities, then neutralized with an aqueous alkaline solution to precipitate iron hydroxide , and the precipitate is separated and dried to prepare high purity iron hydroxide. And
Next, the high-purity iron oxide obtained is calcined at a temperature of 500 to 700 ° C. for 6 to 12 hours in an oxygen atmosphere.   The method for producing high-purity iron oxide according to claim 1, wherein the aqueous iron chloride solution and the aqueous alkaline solution are simultaneously added to water in a reaction vessel that is stirred and maintained at a pH of 9 to 10. . The alkali aqueous solution, aqueous ammonia solution, aqueous methylamine, characterized in that it is either Re not have a trimethylamine solution, method for producing high-purity iron oxide according to claim 1 or 2.   The method for producing high-purity iron oxide according to any one of claims 1 to 3, wherein the purity of the high-purity iron hydroxide is 99.995% or more.

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