JPH0553876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a method for recovering iron oxide of high purity and excellent powder characteristics, which can be used as a raw material for magnetic material soft ferrite, from waste liquid from hydrochloric acid pickling of steel in the steel industry. <Prior art and its problems> From hydrochloric acid pickling waste generated in the steel industry,
In order to prevent pollution and recover useful resources, the waste liquid is treated by a spray roasting method or a fluidized fluid roasting method to recover hydrochloric acid and iron oxide (iron oxide here means α-Fe ₂ O ₃ ), It is widely practiced to provide the iron oxide as a raw material for ferrite, which is a magnetic material. However, the iron oxide obtained by this method contains a large amount of impurities, and silicic acid, which is an impurity that impedes the ferrite properties, can be removed by treatment with an adsorbent before roasting, but aluminum, Impurities such as calcium, chromium, and copper are not removed sufficiently. In addition, a large amount of chlorine remains in the iron oxide recovered from the hydrochloric acid pickling waste, but chlorine is a harmful element that obstructs the ferritization reaction during ferrite production, so it is important to remove it as much as possible. desirable. As a method for removing chlorine, iron oxide obtained by roasting is subjected to high-temperature heating treatment or washing with water, but there are limits to the removal by these methods. The iron oxide recovered by the roasting method is only a low-grade raw material for soft ferrite. Furthermore, the iron oxide has ferrite properties and powder properties that are unfavorable for the ferrite reaction (the average particle size is large, the particle size distribution is wide, and the particles are not spherical but irregular).
Therefore, from this point of view, it remains a low-grade raw material for soft ferrite. <Means for solving the problem> The problem with the above conventional technology is that iron is separated from the hydrochloric acid pickling waste liquid by liquid-liquid extraction, and sulfuric acid or sulfate is added to the ferric chloride salt solution obtained by back extraction. This can be solved by adding a neutralizing agent such as ammonia or urea, and controlling the pH, temperature, and time of the reaction system to directly precipitate iron oxide. <Structure of the Invention> The present invention oxidizes ferrous salts in the waste liquid from hydrochloric acid pickling of steel to ferric salts, adjusts the hydrochloric acid concentration to 5 to 9N, and then uses an ether-based or ketone-based organic extractant. The iron content is extracted into the organic phase as an iron chloro complex by contacting with an organic phase containing iron, and the iron content is transferred to the aqueous phase by back extraction, and the iron content is added to the aqueous phase at a molar ratio of 0.1 to the amount of iron.
Add ~3 amount of sulfuric acid or sulfate and lower the liquid temperature to 80~
Heat to 110℃, add a neutralizing agent to make the pH at the end of the iron precipitation reaction 7 or higher, and then adjust the pH of the solution.
7 or more, and aged for at least 10 hours while maintaining the liquid temperature at 80 to 110℃, and then separating and drying the precipitate. Iron oxide (α -Fe ₂ O ₃ ). Ferrous salts in the pickling waste can be oxidized by blowing air or oxygen, adding oxidizing agents such as nitrates or hydrogen peroxide,
Alternatively, it can be accomplished by electrolytic oxidation.
Since liquid-liquid extraction cannot be performed with ferrous iron as it is, it is oxidized to ferric iron. The reason for adjusting the hydrochloric acid concentration after iron salt oxidation to 5 to 9N is that in the liquid-liquid extraction process, it is difficult to extract iron if it is less than 5N, and iron extraction cannot be significantly improved even if it exceeds 9N. That's true. The organic extractants used include ketone compounds (methyl ethyl ketone, methyl isobutyl ketone,
(diisobutyl ketone, etc.) and ether compounds (dimethyl ether, diethyl ether, etc.) can be advantageously used, but due to their solubility in water, ease of handling,
In consideration of price and the like, ketones, particularly diisobutyl ketone, are most preferred. It is known that ketone compounds and ether compounds are used to extract iron. As used herein, the term organic extractant refers to the above-mentioned extractants themselves and their dilutions with organic solvents such as kerosene. Through liquid-liquid extraction, iron is transferred to the organic phase, and silicic acid,
Impurities such as aluminum, calcium, chromium, and copper remain in the water phase, and iron can be effectively separated from the impurities. The iron content in the organic phase is back-extracted with ion-exchanged water and transferred to the aqueous phase to obtain a purified ferric chloride solution with extremely few impurities. The reason for adding sulfuric acid or sulfate to such a ferric chloride solution is to reduce the amount of chlorine mixed as an impurity in the iron oxide obtained, and the molar ratio to iron in the solution is 0.1. If added at a ratio of ~3, iron oxide with a sufficiently low chlorine content can be obtained. Ferric chloride solution with addition of sulfuric acid or sulfate is
The temperature is heated to 80 to 110°C, but temperatures below 80°C are unfavorable because iron oxyhydroxide (α-FeOOH) and iron oxide (α-Fe ₂ O ₃ ) are simultaneously generated during neutralization; At a temperature above that temperature, only iron oxide is produced, but the temperature does not exceed that temperature under normal pressure. The pH of the solution at the end of the iron precipitation reaction is set to 7 or higher,
In addition, by maintaining the pH of the solution during the aging treatment at 7 or higher, iron oxide (α-Fe ₂ O ₃ ) can be obtained directly instead of iron oxyhydroxide. The neutralizing agent used is ammonia, urea, etc. With conventional technology, basic iron sulfate [NH ₄ Fe ₃ (OH) _3
However , according to the present invention, even in _the coexistence of sulfate ions and chloride ions, the temperature of the solution, the pH of the solution, and the aging time in the neutralization reaction can be maintained at a specified level. It is possible to appropriately control this to produce only iron oxide without substantially producing basic iron sulfate. After forming the precipitate, increase the pH of the liquid to 7 or higher and the temperature of the liquid to 80~
Keep at 110°C for at least 10 hours. By this,
Iron oxide is produced and ripened, and the crystal grain size and grain size are adjusted. <Effects of the Invention> According to the present invention, (1) Not only silicic acid present in the hydrochloric acid pickling waste solution but also aluminum, calcium,
Impurities such as chromium and copper can be removed to a high degree. (2) Iron oxide with extremely low chlorine content can be obtained by adding sulfuric acid or sulfate to purified ferric chloride solution. (3) Iron oxide, rather than iron oxyhydroxide (α-FeOOH), can be obtained directly from the hydrochloric acid pickling waste liquid by controlling the pH, temperature, and aging time of the liquid during neutralization. Since the oxide is directly obtained through wet processing, unlike dry methods such as roasting, there is less risk of recontamination of iron oxide, and the obtained iron oxide has a small average particle size and a narrow particle size distribution.
Moreover, since it has a spherical shape, it is ideal as a raw material for soft ferrite. That is, according to the present invention, it is possible to efficiently recover iron oxide powder of high purity and homogeneous morphology and particle size from a highly concentrated hydrochloric acid pickling waste solution containing many impurities.
It is extremely effective industrially. <Specific Description of the Invention> The present invention will be illustrated below with reference to Examples. Example 1 200 hydrochloric acid pickling waste liquid (composition: Fe153g/,
HC1 1.3N Silica 60mg/, Aluminum 39
mg/, Calcium 10mg/, Chromium 71mg/
After oxidizing ferrous chloride to ferric chloride by electrolytically oxidizing 63 gm of copper (remaining portion), concentrated hydrochloric acid was added to adjust the hydrochloric acid concentration to approximately 6N. Add approximately the same amount of diisobutyl ketone (DIBK) to this solution, stir and mix, and convert the iron content into an iron chloro complex to form DIBK.
extracted into the phase. Next, approximately the same amount of ion-exchanged water was added to this DIBK phase and mixed with stirring, and the iron chloro complex in the DIBK phase was back-extracted into the aqueous phase as ferric chloride. To this aqueous solution, sulfuric acid was added in an amount of 1 mole per mole of iron in the solution, heated to 98°C, and ammonia was added as a neutralizing agent until the pH of the solution was 7 at the end of the iron precipitation reaction and during aging. After the precipitation reaction is complete, continue to raise the pH to 7 or higher and the liquid temperature to 98.
The mixture was kept at ℃ and aged for 10 hours to obtain a reddish-brown precipitate. The resulting reddish-brown precipitate was collected by centrifugation and dried by spray drying to obtain a reddish-brown powder. As a result of X-ray diffraction analysis, the powder was found to be α-
It was Fe ₂ O ₃ (hematite). As a result of measurement using an electron microscope, the average particle size was 0.5 μm, and all particles were within the particle size range of 0.2 to 0.8 μm and spherical. Further, impurities such as silica, aluminum, calcium, chromium, and copper were all less than 50 ppm, and chlorine was less than 100 ppm. In addition, the chlorine content in iron oxide powder produced by varying the amount of sulfuric acid added to the ferric oxide aqueous solution obtained by back extraction was measured. FIG. 1 shows the relationship between the amount of sulfuric acid added to the ferric chloride solution and the chlorine content of the product. As seen here, the amount of chlorine decreases when 0.1 mole of sulfate is added to 1 mole of iron, and the effect is saturated at about 3 moles. In addition, when forming a precipitate, the amount of ammonia added was changed to change the pH of the liquid at the end of the iron precipitation reaction and during the aging process, and the temperature was maintained at 98°C and the aging time was changed to perform the precipitation. This was treated in the same manner as above to obtain iron oxide powder, and its morphology was examined by X-ray diffraction. Figure 2 shows the relationship between the PH of the solution, the aging time, and the product when a ferric chloride solution containing sulfate radicals is neutralized and aged at 98°C. As seen here, iron oxyhydroxide is produced when the pH is below 7.
If it is 7 or more, iron oxide is generated. Comparative Example 1 The hydrochloric acid pickling waste used in Example 1 was spray roasted at 700°C, and 3 g of the resulting powder was mixed with 300 ml of ion-exchanged water.
After washing with water and drying at 100°C. The powder obtained in this way was analyzed by X-ray diffraction and the result was α-
It was Fe ₂ O ₃ , and the results of measurement using an electron microscope showed that the average particle size was 5 μm, widely distributed in the range of 0.5 to 10 μm, and the shape was not uniform and not spherical. The impurity content of this powder is 260ppm silica, aluminum
180ppm, calcium 50ppm, chromium 330ppm,
Copper was 290 ppm and chlorine was 800 ppm. Comparative Example 2 The powder obtained by spray roasting the hydrochloric acid pickling waste used in Example 1 at 700°C was further heat-treated at 1000°C for 1 hour.
The result of analysis by line diffraction is α-Fe ₂ O ₃ ,
Measurement results using an electron microscope show that the average particle size is 5 μm.
The particles were widely distributed in the range of 0.5 to 10 μm, and the shape of the particles was not constant and not spherical. The impurity content of this powder is 270ppm silica, aluminum
2700ppm, calcium 175ppm, chromium 320ppm,
Copper was 280ppm and chlorine was 1100ppm. 【table】

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of sulfuric acid added and the amount of chlorine in the produced iron oxide when sulfuric acid is added to a ferric chloride solution. Figure 2 shows the relationship between the PH of the solution after addition of a neutralizing agent, the precipitate ripening time, and the chemical species of the produced precipitate when a ferric chloride solution is neutralized with ammonia.

Claims (1)

[Claims] 1 Oxidize the ferrous salt in the waste liquid from hydrochloric acid pickling of steel to ferric salt, adjust the hydrochloric acid concentration to 5-9N, and then contact it with an organic phase containing an ether-based or ketone-based organic extractant. Iron content is extracted into the organic phase as an iron chloro complex, the iron content is transferred to the aqueous phase by back extraction, and sulfuric acid or sulfate is added to the aqueous phase in an amount of 0.1 to 3 in molar ratio to the amount of iron. , heat the liquid temperature to 80 to 110℃, add a neutralizing agent, and adjust the pH at the end of the iron precipitation reaction.
7 or higher, and keep the pH of the liquid at least 7 or higher and the temperature at 80 to 110℃.
A method for recovering iron oxide (α-Fe ₂ O ₃ ) with high purity and excellent powder properties from the hydrochloric acid pickling waste solution by separating and drying the precipitate after aging for 10 hours.