JPS6287412A - Production of high-purity alumina using colloidal earth as raw material - Google Patents

Abstract

PURPOSE:To obtain high-purity alumina by the use of an inexpensive naturally- occurring raw material to readily be reacted with an acid, by crystallizing an aluminum salt from a reaction solution obtained by treating colloidal earth with a mineral acid by concentrating the reaction solution or by allowing it to stand and to cool it, purifying precipitate crystal, calcining and grinding. CONSTITUTION:High-purity alumina is produced by the following 4 processes. (1) A process wherein colloidal earth is blended with a mineral acid in an amount to give >=6N acid concentration in a reaction and stirred. (2) A process wherein a reaction solution is separated from a reaction mixture. (3) A process wherein the reaction solution is concentrated, allowed to stand and cooled or treated with an alkali to crystallize an aluminum salt and the precipitated crystal is separated and (4) a process wherein the aluminum salt crystal is purified, calcined and ground. Or, the high-purity alumina can also be produced similarly by reacting the colloidal earth with the mineral acid to give the aluminum salt, reacting the aluminum salt with ammonium bicarbonate to give ammonia dawsonite, calcining and grinding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for producing crystal-pure aluminum using colloidal clay as a raw material.

The high purity alumina produced by the method of the present invention is ^1
Contains 99.9% of 203, and its uses c
at: High quality sintered bodies such as saf sapphire substrate 81 windows for SOS, translucent pipes for generating tubes of high-pressure sodium lamps, thread guides, cutting openings, etc., as well as abrasives, carriers for phosphors, special glass A wide variety of additives are available.

Prior Art Conventional methods for producing high-purity alumina include the following.

■ A method in which aluminum hydroxide obtained from bauxite by the Bayer process is refined into ammonia and alum, which is then calcined and crushed.

■ A method in which aluminum hydroxide J obtained from bauxite by the Bayer method is washed to increase its purity, and then calcined and crushed.

■ AI produced by reacting aluminum metal with hydrochloric acid
'Cl3-611□0 is separated and purified as a crystal, which is then calcined with or without induction into ammonia dawsonite.
How to crush.

■ A method in which organoaluminum compounds are synthesized from aluminum metal, purified and then hydrolyzed to produce permanent alumina, calcined, and crushed.

■ A method of spark-discharging high-purity aluminum metal in water to generate aluminum hydroxide, which is then fired and crushed.

In this way, the raw materials used in conventional manufacturing methods are mainly aluminum hydroxide or aluminum metal obtained from bauxite, but there are also known manufacturing methods that use crystalline clay minerals such as kaolin halloysite. The intermediates mainly include aluminum hydroxide, ammonia alum, ammonia dawsonite, and aluminum mineral salts.

Problems to be Solved by the Invention However, in the method for producing the above-mentioned intermediate, aluminum hydroxide obtained from aluminum, horn, metal, or bauxite by the Bayer method is extremely expensive as a raw material. , 14 are difficult to dissolve in acids and should be dissolved! It requires heating at a high temperature for a long time in order to dissolve the metal, and also has the drawback of generating hydrogen gas when reacting with alumina J and metal tJ acids. The aluminum metal inside remains as is.
Since F. is not soluble in acid, it must be calcined once at 500 to 700°C.

The present invention aims to solve the problems of such conventional methods.Although it is a natural raw material and contains many impurities, it is inexpensive, easily reacts with acids, and does not emit hydrogen gas during the reaction. The present invention relates to a method for producing 101 purity alumina using colloidal soil as a raw material.

In order to solve the problems, the method for producing high-purity alumina according to the present invention uses colloidal soil as a raw material, and uses colloidal mineral acid and colloidal soil such that the acid concentration at the time of reaction is 6 N or more. Mix and stir, separate the reaction solution from the reaction mixture, and then crystallize the aluminum salt by means such as concentration, cooling, or addition of an acid or alkali. Calcining and crushing purity salts or turning these high purity aluminum salts into ammonia dawsonite? The desired purpose was achieved by crushing, firing and pulverizing the mixture.

The colloidal soil that is the starting material for the present invention is the accumulated and weathered volcanic ash soil erupted at the end of the 4th century. Mineralogically, it is a silica-alumina gel whose main component is alonphene, and it varies depending on the region. Kanuma soil, millet ± (Tochigi prefecture),
Misojo (Nagano Prefecture), Mizuto (Shimane Prefecture), Borasu, Red Haya (
61 The acids used for the reaction with colloidal soil in carrying out the method of the present invention are preferably mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. and
The phosphoric acid series shows almost the same reaction 111 to colloid, but phosphoric acid is slightly inferior.

Mineral acid concentration ti during reaction: 6 N or more, preferably 8 N
Therefore, if the concentration of the mineral acid is lower than 6N, a large amount of silica will be dissolved in the reaction solution, and silica will remain in the final product, which will reduce the purity of the product, which is not preferable.

The reaction temperature between the colloidal soil and the mineral acid is not particularly limited, but is preferably 50 to 80°C, and the stirring time is usually sufficient for 30 minutes to 1 hour. When separating the reaction liquid, it is desirable to wash and recover the reaction liquid adhering to impurities with an acid of the same concentration. Washing with water should be avoided because it dilutes the acid concentration and requires extra acid or steps for the subsequent purification. Impurities washed with acid should be washed with water and used as a silica source for zeolite synthesis. It can be used as

In the method of reacting hydrochloric acid with colloidal soil, AlC in the reaction solution
Adjust the amount of l:+4 so that the concentration is 25-32w 1%, and if this concentration is not reached, it is desirable to adjust it within this range by concentrating it under reduced pressure or adding 8ICl3.6+1□0 crystals. . By blowing hydrogen chloride gas into this reaction solution to increase the concentration of hydrochloric acid, ^1c13.
611□O crystals are precipitated, separated and washed with 35% hydrochloric acid. If the concentration of impurities contained in the crystal exceeds the target value, dissolve the crystal in pure water and use the same method again to crystallize, separate, and wash AlCl3-611□0 to purify it and convert it into aluminum chloride hexahydrate. , after drying the crystals about 40
The product can be obtained by calcination to a temperature of 0°C, further calcination at 700-1300°C, and pulverization.

The advantage of using colloidal soil is most clearly seen in the reaction between colloidal soil and nitric acid. In other words, aluminum hydroxide is difficult to react with nitric acid and requires an abnormal heating time of 10 hours at a temperature of 100°C when the acid concentration is 12N, whereas colloidal soil reacts at a temperature of 80°C.
A reaction time of 30 minutes to 1 hour is sufficient at a temperature of . There is also no need for a calcination step, as is the case with crystalline clay minerals.

In this reaction, the amount of AJ(NOz)y in the reaction solution is 55~
The amount used was adjusted to 90w 1%, and the reaction solution was mixed with old-2-ethylhexyl I'l+ospha
te was dissolved in a water-insoluble organic solvent such as kerosene to remove the iron content by liquid-liquid extraction, and the aqueous phase was separated and concentrated under reduced pressure to reduce the concentration of AI (NO3) 3 to 67.
Adjusted to ~95 wt%, and as it cooled,
(NO,) J-911□0 crystals may be precipitated, recrystallized using a nitric acid aqueous solution, calcined to 300°C, further calcined to 700 to 1300°C, and pulverized. Note that the iron content during the reaction can also be separated and removed by heating the alumina content in excess and causing precipitation of iron oxide.

In the method of reacting sulfuric acid with colloidal soil, aluminum sulfate 1" tum is produced, which has a small difference in solubility due to temperature differences and is difficult to purify by recrystallization. Therefore, it is desirable to purify it by introducing it into ammonia alum. For the reaction, A1□(
504) Adjust the amount used so that the concentration of s-5-18H is 10 to 58 wt%. If the concentration of aluminum sulfate in the reaction solution is higher than this, crystals will precipitate in the reaction solution and become insoluble in the reaction solution. Separation of substances becomes difficult, and if it is lower than this, the recovery rate of crystals in the next step will be poor, which is not preferable. The reaction solution is cooled and Ajg(SO4)s-f
ell□0 is crystallized, separated, washed with 12N sulfuric acid, dissolved in water, added sulfuric acid and ammonia, reacted at pH 1 to 3.5, cooled and separated after the reaction, and poured into cold water. 900 to 1300
The product can be obtained by firing at ℃ and pulverizing.

In addition, in the present invention, ammonium bicarbonate 10-am is reacted with alumina 1 and salt produced by reacting colloidal soil and mineral acid to obtain ammonia dosol 1, which is calcined and pulverized. By doing so, high purity alumina can be produced in the same manner as described above.

Effect: The reason why colloidal soil has a characteristic of being easily reacted with acids in the method of the present invention is considered to be as follows. In other words, colloidal soil is represented by the following chemical formula, with CAlm0. -23iOz'
1~311zO) (gel) + (mAl(Ot
l)+)nFe(0)1)3) (gel), consisting of an allophane core mainly composed of silica and alumina gel, and accompanying alumina gel and iron gel, which are rich in activity. Approximately 80% of the hydrogel is amorphous, so it easily reacts with acids and has a chemical composition similar to that of kaolin, hallosite, etc., which belong to crystalline clays. have different properties, and colloidal soil has a significantly larger surface area than other alumina materials, so it reacts in a relatively short time because it has good contact efficiency with acids and alkalis. ends.

Example 1 A. Preparation of purified colloidal soil When atoms collected from Terauchi, Moka City, Tochigi Prefecture are crushed together with water in a ball mill pulverizer, a light yellow muddy water is produced. The rock portion with a high specific gravity contained as a substance was collected, and only the muddy water with a low specific gravity was collected and classified downstream, and the collected muddy water was dehydrated and separated by a filter press to obtain a pale yellow plate-shaped cake. The moisture content of this colloidal soil was 65 to 70% by weight, and the results of analyzing the solid content of purified colloidal soil prepared by drying this to a solid content of 50% by weight are as shown in Table 2.

Table 2 Chemical composition of purified colloidal soil, production of alumina by reaction between colloidal soil and hydrochloric acid.
After adding 12.3 kg of hydrogen chloride gas and stirring for 1 hour at a temperature of 80°C, the reaction liquid was filtered from the reaction mixture, 2.1 kg of hydrogen chloride gas was blown into it, and the precipitated crystals were separated.
Washed twice with 5% hydrochloric acid. Add and dissolve 2.2 kg of water to 3.7 kg of this crystal = 13-, and add 1 kg of hydrogen chloride gas to this.
, 2 kg was blown in to precipitate crystals and separated in the same way.
After washing, 6.6 kg of crystals were obtained. The amount of impurities in the aluminum chloride hexahydrate thus obtained was determined by atomic absorption spectrometry, t
The results of CP emission spectroscopy and silica measurements using the molybdenum blue method are shown in Table 3. After drying the aluminum chloride crystals at a temperature of 105°C, the aluminum chloride crystals were calcined to about 400°C, and then further heated to a temperature of 1000°C. The mixture was calcined for 1 hour and pulverized to obtain 1.0 kg of finely granulated alumina.

The particle size of the substance is in the range of 0.3 to 1 μm, and its particle size distribution is extremely sharp. Sulfuric acid is added to the substance, and the substance is sealed and heated at a temperature of 240°C for 18 hours to dissolve it.
The results of measuring the amount of impurities in alumina using the same method as above are shown in Table 4, and the main point is 99.99%.
It contained the above alumina.

Furthermore, the number of impurities after firing in Table 4 corresponds to the amount of impurities before firing in Table 3, and it was recognized that the purity of the product could be predicted from the amount of impurities before firing.

Example 2 2.8 kg of 12N nitric acid was added to 1.2 kg of colloid purified in Example 1, and the mixture was reacted at a temperature of 80° C. for 1 hour.
The reaction solution was filtered. This reaction solution contains l1i-2ethyl
12.6 kg of a kerosene solution containing 15et% hexyl Phosphate was added for liquid-liquid extraction, this extraction operation was repeated twice to remove the Fe content in the reaction solution, and then the aqueous layer of the extract was separated and this was After concentrating under reduced pressure, it is cooled to precipitate crystals, ^l (NO3) 5-9
1.1 kg of 11□0 crystals were obtained. The aluminum nitrate nonahydrate was recrystallized by adding 0.8 kg of 16N nitric acid, washed with 16N nitric acid, and the crystals were calcined to 300°C, then fired at a temperature of 1000°C for 1 hour, and then milled in a ball mill. 0.1 kg of fine alumina having a particle size of 1.0 to 1.5 μm was obtained.

The amount of impurities in the product was determined by measuring impurities in aluminum nitrate nonahydrate using the same method as in the example above.
As shown in Table 5, it is 63 μg or less per 1 g of Al, so the alumina obtained by firing from this is 9
It was recognized that it contained A1□03 min of 9.9% or more -1;

Example 3 9.3 kg of 12N sulfuric acid was added to 1.4 g of colloid soil purified in Example 1 and reacted at a temperature of 70°C for 30 minutes.
The reaction solution was filtered while hot. The reaction solution was cooled to precipitate crystals, which were filtered, and the crystals were dissolved in 1.0 kg of 12N sulfuric acid.
Washed with.

Next, the crystals were dissolved in 1.5 kg of water, and 98% sulfuric acid was added.
．． Add 0.6 kir and add 25% ammonia water to 12 yen while stirring.
．． Added up to 0. The reaction mixture was cooled, and the precipitated crystals were separated and washed with water to obtain 1.2 kg of ammonia alum crystals. The crystals were further recrystallized twice with water and then fired to a temperature of 500"c, approximately 1200"c.
Calcined at a temperature of 1' for 1 hour, and ground in a ball mill to produce alumina with a fine powder of 0. Ikg (n).The particle size of Motoichi is 0.3 ~
The impurities in ammonia and alum before firing were measured using a range of 0.5μ, and the results were as shown in Table 6. As a result, the purity of the alumina obtained by firing was 9.
9.9% was recognized as ``nu+''.

Example 4 0.57 kg of Reta Alc13-611zO crystals obtained by treating colloidal soil and hydrochloric acid in the same manner as in Example 1 was dissolved in 521 water, and 6.6 kg of ammonium bicarbonate was dissolved in 421 water.
It was added dropwise to the solution containing g over about 1 hour under stirring while maintaining the temperature of 48 to 50°C, and after the completion of the dropwise addition,
After maintaining the same state for 0 minutes, the mixture was cooled, separated, and washed with water to obtain 270 g of ammonia dawsonite. The ammonia dawsonite was calcined to 300°C and further heated to 100°C.
The mixture was fired at a temperature of 0° C. for 1 hour to obtain 100 g of finely powdered alumina having a particle size of 0.3 to 0.8 μm.

The impurities contained in Motoichi were measured using the method described in Example 1, and the results were as shown in Table 7. As a result, the purity of the alumina obtained by firing was confirmed to be 99.9% or higher. It was done.

Claims (2)

[Claims] (1) A step of adding and stirring a mineral acid to colloidal soil so that the acid concentration at the time of reaction is 6N or more, a step of separating the reaction liquid from the reaction mixture obtained by the above treatment, a step of concentrating and releasing the reaction liquid. A high purity product made from colloidal clay, which consists of the steps of crystallizing aluminum salt by cooling or adding acid or alkali, separating the precipitated crystals, and refining the aluminum salt crystals, firing and crushing them. Alumina manufacturing method. (2) A step of adding and stirring a mineral acid to the colloidal soil so that the acid concentration during the reaction is 6N or more, a step of separating the reaction liquid from the reaction mixture obtained by the above treatment, a step of concentrating and releasing the reaction liquid. A step of crystallizing the aluminum salt by cooling or adding acid or alkali, and separating the precipitated crystals; and a step of calcining and pulverizing the ammonia dawsonite produced by reacting the aluminum salt with ammonium bicarbonate. A method for producing high-purity alumina using colloidal soil as raw material.