JPS5825052B2 - Production method of high purity tricobalt tetroxide - Google Patents

Description

Detailed Description of the Invention The present invention efficiently produces high-purity tricobalt tetroxide with extremely low content of impurities consisting of alkali metals and anionic components such as sulfate radicals, nitrate radicals, and chloride ions, with high productivity. It relates to a method of manufacturing well.

Conventionally, high-purity tricobalt tetraoxide has been purified by adding approximately an equivalent amount of caustic soda or sodium carbonate to an aqueous divalent cobalt salt solution to generate a cobalt hydroxide or basic cobalt carbonate precipitate, and repeatedly washing this precipitate with water. rear,
It was manufactured by dehydration/drying/calcination.

However, cobalt hydroxide or basic cobalt carbonate precipitates obtained under these precipitation conditions have extremely poor flocculation and sedimentation properties, making repeated water washing and purification operations in a slurry state inefficient, and dewatering properties are also poor. In addition, the productivity was extremely low as a whole.

Therefore, the present inventors conducted extensive studies on a method for obtaining a cobalt hydroxide precipitate with excellent flocculation and sedimentation properties, as well as good dehydration properties, and found that these points could be solved by appropriately selecting the conditions for adding alkali hydroxide. We found that it was significantly improved.

However, there are limits to this improvement in flocculation and sedimentation.
It is inevitable that repeated water washing and purification in the state of cobalt hydroxide precipitate slurry is essentially inefficient for the purpose of obtaining a sufficient purification effect.

As a result of various studies on this point, we found that if the cobalt hydroxide precipitate is dehydrated/dried in an unpurified state and then dispersed again in water and washed, the cobalt hydroxide particles themselves no longer become water sludge. Coagulation/
The present invention was achieved by discovering that the sedimentation property is significantly improved and water washing purification is extremely effective.

That is, the present invention dehydrates a cobalt hydroxide precipitate obtained by reacting an alkali hydroxide in an amount equivalent to or more than 1.2 times the amount of divalent cobalt ions on a divalent cobalt salt aqueous solution and/or a divalent cobalt double salt slurry. , dried, and then treated with an aqueous system to wash the dried product until the alkali metal ion concentration in the washing water becomes 200 mmol or less, followed by dehydration, drying, and, if necessary, calcination. A method for producing cobalt trioxide is provided.

The divalent cobalt salt used in the present invention is a water-soluble divalent cobalt salt, and includes, for example, cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt bromide, and cobalt acetate.

In addition, divalent cobalt double salts are divalent cobalt double salts that are poorly soluble in water, such as basic cobalt carbonate (CoCO3.
XCo(OH)2: ] , basic cobalt sulfate (C.

(OH)2・XCo50. ) and basic cobalt carbonate/sulfate (Co(OH)2/Xco(COa)"'1co
8(J)4].

In the first step of the present invention, first, the divalent cobalt salt aqueous solution and/or divalent cobalt double salt slurry is
1.2 times equivalent or more of the amount of valent cobalt ions, preferably 1
．． A 3 to 5.0 times equivalent amount of alkali hydroxide such as sodium hydroxide or potassium hydroxide is allowed to act.

If the amount of alkali hydroxide added is less than 1.2 equivalents, for example, in a commonly used equivalence reaction method, a cobalt hydroxide precipitate with good flocculation and sedimentation properties cannot be obtained.

On the other hand, it is meaningless if the amount of alkali hydroxide added is too large, and economically it is appropriate to set the upper limit to about 5.0 times the equivalent.

The amount of alkali is selected based on the amount necessary to hydrolyze components other than C0(OH)2 contained in the divalent cobalt double salt.

In particular, when cobalt hydroxide is precipitated from an aqueous solution of cobalt sulfate, more than 99% of the cobalt ions are precipitated by adding approximately 0.7 equivalents of sodium hydroxide, but this is mainly due to basic cobalt sulfate [co(OH )2・XC
This is because CO3 in this double salt precipitates.
Although O4 content decreases as the amount of sodium hydroxide added increases, it is still not possible to completely desorb CoSO4 content near equivalence.

If CoSO4 remains, sulfate radicals as impurities will be mixed into the final product, which is not preferable.

Even in the case of cobalt hydroxide precipitation from a cobalt sulfate aqueous solution, mixing of sulfate radicals into the precipitation can be practically achieved by increasing the amount of alkali hydroxide added to 1.2 times equivalent or more, preferably 1.3 times equivalent or more. can be controlled up to the level.

The rate at which alkali hydroxide acts on cobalt ions also has a subtle effect on the flocculation and sedimentation properties of the cobalt hydroxide produced.

The use of 1.2 times equivalent or more alkali hydroxide and the faster the feed rate of the alkali hydroxide tends to provide better flocculation and sedimentation properties.

In extreme cases, operating conditions such as adding a divalent cobalt salt aqueous solution all at once to a predetermined amount of an alkali hydroxide aqueous solution prepared in advance and continuing stirring for a certain period of time can result in stable water with good flocculation and sedimentation properties. This can be recommended as an example of conditions for producing cobalt oxide precipitation.

The alkali hydroxide that acts on the divalent cobalt salt aqueous solution and/or the divalent cobalt double salt slurry may be in the form of an aqueous solution, powder, granules, or flakes, but it is especially preferable to prepare it as an aqueous solution. is operationally preferable.

In addition, the cobalt hydroxide production reaction is usually carried out under aqueous stirring conditions, at a temperature range of room temperature to 100°C, and for a reaction time of 0.1 to 100°C.
It is carried out in the range of hr.

The produced cobalt hydroxide precipitate slurry is dehydrated with a dehydrator to a water content of 95 to 50% by weight after adding a polymer flocculant such as an acrylamide copolymer at an amount of about 1 to 300 ppm as necessary. and make a dehydrated cake.

In this step, various types of normal dehydrators such as vacuum type, pressurized type, and centrifugal type can be used.

Subsequently, the dehydrated cake is dried under heating conditions to a moisture content of 40% or less, preferably 20% or less, and then pulverized using a pulverizer if necessary.

This drying can be carried out at a temperature of 50 to 900° C. under normal pressure or reduced pressure. If the drying temperature is 300° C. or higher, modification of cobalt hydroxide to tricobalt tetroxide occurs.

The second step of the present invention consists of wet refining the unpurified dry powder obtained above, in which the dry powder is dispersed in water and the alkali ion concentration in the supernatant is 200 p.
A method of washing by repeatedly replacing the aqueous phase until the concentration of alkali ions in the effluent becomes 200 ppm or less, preferably 1100 ppH or less, or placing the dry powder in a fixed bed! Efficient purification can be achieved based on improved flocculation and sedimentation properties by using a flow-through washing method until the following is achieved.

The cobalt hydroxide or cobalt oxide powder that has undergone wet refining is then dehydrated and dried, and if necessary,
High purity tricobalt tetraoxide is obtained by firing at a temperature of ~900°C, preferably 350~850°C.

If 300 to 900°C is used as the drying condition for unpurified cobalt hydroxide in the first step, the calcination operation in this final stage is necessary because cobalt hydroxide has already been modified to cobalt oxide. It's not even necessary.

The firing conditions in the first step and/or the second step are generally well known, and suitably range from 300 to 900°C, preferably from 350 to 850°C.

If it is below 300°C, there is a possibility that cobalt hydroxide may remain, and if it is above 900°C, there is a possibility that cobaltous oxide may be produced and mixed, which is not preferable for the purpose of producing high-purity tricobalt tetroxide.

The highly purified tricobalt tetroxide thus obtained is useful for applications such as semiconductor materials for the electronic industry, special pigments, and catalysts for the chemical industry.

The present invention will be explained in detail below using Examples.

Note that the values of parts, parts, and ratios used in the present examples indicate parts by weight, parts by weight, and weight ratios, respectively, unless otherwise specified.

Metal impurities in cobalt oxide were determined by dissolving the sample in hydrochloric acid and then applying it to an atomic absorption spectrometer.

The pure cobalt content in cobalt oxide was determined by precipitating a sample dissolved in hydrochloric acid as oxalate, and then calcining the precipitated oxalate.

Sulfate radicals in cobalt oxide were quantified by applying the barium salt precipitation method to samples dissolved in hydrochloric acid.

The molecular structure of tricobalt tetroxide was identified by the crystal lattice constant determined by X-ray diffraction.

Example 1 Cobalt sulfate superhydrate salt 5KP (Co+1 = 17.8 moles - 35.6 equivalents) was dissolved in 60A' pure water, and this was added to a separately prepared 20% sodium chloride solution 15. (NaO
When the cobalt hydroxide precipitate slurry was rapidly added to the solution (H pure content = 72 moles = 72 equivalents) and stirred at room temperature for 1 hour, a cobalt hydroxide precipitate slurry was produced.

Next, 1,100 pp of a polymer flocculant ("Sunfloc P-200'" manufactured by Sanyo Chemical Co., Ltd.) was added to this precipitate slurry, and then dewatered using a suction type Buchna funnel with a mouth area of 615 cIrL2 equipped with a mouth paper. 5.15 Kp of dehydrated cake with a moisture content of 67% was obtained in 6 hours of passing time.

Next, the dehydrated cake (5.15Kp) was finely loosened, placed in a hot air dryer, and treated for 5 hours.
-8 type)), an unpurified dry cobalt hydroxide powder (water content 15%) was obtained.

The composition of this powder was Co=48%, Na=3.4% and S0422.6%.

Next, mix the unpurified dry powder with 201% pure water! After stirring for 1 hour, the mixture was dehydrated using the same Buchner funnel as described above in the following manner.

After about 0.5 hours of passing time, additional pure water 407 was added to the dehydrated cake using a shower set over a period of 2 hours, followed by
．． The suction was continued for 5 hours.

The Na ion concentration in the mouth at this final stage is 25P
It was +.

As a result, a purified dehydrated cake with a water content of 58 cm was produced at 3.62K.
p was obtained.

The total time required for this wet purification process was approximately 5 hours.

Next, the purified dehydrated cake was finely loosened and treated in a hot air dryer at 150°C for 3 hours, then fired in an electric furnace at 700°C for 2 hours and cooled. Cobalt was obtained.

Co 73.37% (999% in terms of Co304) Na 0.007% 80, 0.01% or less Comparative Reference Example 1 As cobalt hydroxide production reaction conditions, a 10% caustic soda aqueous solution 15.0 KP was used instead of a 20% caustic soda aqueous solution 15.0 KP. 0KP (NaOH purity = 36 moles = 36 equivalents)
When the reaction operation and filtration/dehydration operation were performed in the same manner as in Example 1 except for using %, it took a long time of 24 hours, and productivity was extremely poor.

Comparative Reference Example 2 The results are shown when the wet refining process was applied to an unpurified dry powder with no blemishes and an unpurified dehydrated cake.

A dehydrated cake of 5.15 KP with a moisture content of 67% obtained by performing the same operation as in the first half of Example 1 was finely loosened to give 2M
After stirring for 1 hour, the mixture was dehydrated using the same Buchner funnel as in Example 1, and a dehydrated cake with a water content of 69% was obtained in about 8 hours.

Regarding this cake, the cake layer was dense and water permeability through the mouth was poor, so it was impossible to wash the cake using an additional shower flow system.

Therefore, this dehydrated cake was finely loosened again and 40A'
After 1 hour of stirring, the dehydrated cake was dehydrated using the same Buchner funnel as in Example 1. After about 8 hours of passage time, the dehydrated cake with a water content of 70% decreased to 5.67%.
Obtained.

The Na ion concentration in the mouth at this final stage is 170
It was ppm.

The total time required for this wet purification process was approximately 20 hours.

Next, the obtained purified dehydrated cake is finely loosened and then 15
After being treated in a hot air dryer at 0°C for 4 hours, it was fired in an electric furnace at 700°C for 2 hours and cooled, yielding tricobalt tetroxide having the following composition.

This purity is considerably inferior to the results of Example 1.

Co 72.92% (CO304 equivalent 99.3%) Na 0.082%804
As can be seen from this result, when the wet refining process is applied to the unrefined dehydrated cake, the processing efficiency is lower than that of the method of the present invention, so the refining effect is low even though the refining process is time-consuming. does not rise.

Example 2 Cobalt nitrate large water salt 5 Kp (Co++ = 17.2 mol = 34.4 equivalent) was separately added into a stirring 20 Kp (NaOH purity = 96 mol - 96 equivalent) aqueous solution of 20% sodium hydroxide. ) was added to the cobalt solution prepared by dissolving it in pure water 1001 at a flow rate of 517 ytu'yw>,
When stirring was continued for 1 hour, a cobalt hydroxide precipitate slurry was produced.

Next, after adding iooppm of a polymer flocculant ("Sunfloc P-200" manufactured by Sanyo Chemical Co., Ltd.) to this precipitate slurry,
When the mixture was placed in a centrifugal dehydrator at a rotational speed of 3.00 rpm for 1 hour, a dehydrated cake with a water content of 74 cm was obtained.

Next, the dehydrated cake was loosened finely, placed in a hot air dryer at 150°C for 3 hours, and then heated in an electric furnace at 500°C for 3 hours.
It was baked for a time and then cooled.

Next, a crusher equipped with a screen with an opening of 0.5 mm (
When the mixture was passed through a fine-use sample mill (AP-8 model), unrefined dry cobalt oxide powder was obtained.

The composition of this powder is Co=65% and Na=5.5
%Met.

Next, the unrefined cobalt oxide powder was placed on a suction-type Buchner funnel with a mouthpiece area of 615crIL2 equipped with a spout, and pure water 1001 was sprayed from above using a shower set over a period of 2 hours, followed by suction-filtering for 0.5 hours. Continuously, a purified cobalt oxide water-containing cake was obtained.

The Na ion concentration in the oral fluid at this final stage is 151
It was F.

Next, when the purified cobalt oxide water-containing cake was treated in a hot air dryer at 200°C for 5 hours, Co=73.4% (Co30
4 conversion 99.9%) t Na = 0.005% high purity tricobalt tetroxide to 1.24? Obtained.

Comparative Reference Example 3 Instead of 20% caustic soda aqueous solution 20KP, 72% caustic soda aqueous solution 20KP (NaOH purity = 34.6
A cobalt hydroxide precipitate slurry was obtained in the same manner as in the first half of Example 2 except that mol = 34.6 equivalents) was used, and 100 pl [l] of a polymer flocculant ("Sunfloc P-200" manufactured by Sanyo Chemical Co., Ltd.) was added. Then, increase the rotation speed to 3.00 Orp.
When the sample was placed in a centrifugal dehydrator for 1 hour, the water content decreased to only about 85%, which required considerably more dehydration than in Example 2.

Calculating from this result, the water retention capacity of 1 part of dry solid content is 85
/15=5.67 parts, which is 74/2 in Example 2
6=2.85 parts, the amount of residual water was large, and the drying process in the latter half was significantly disadvantageous.

Example 3 Cobalt chloride/big water salt 5 Ky (Co++= 21.
0 mol = 420 equivalents) was dissolved in 6 (l) of pure water, added to a separately prepared 10% sodium carbonate aqueous solution 23KP, and stirred at room temperature for 1 hour, resulting in basic cobalt carbonate double salt [CoCO3. XCo(OH)2.X is approximately 2] A precipitate slurry was produced.

Next, separately prepared 10% soda aqueous solution 27Kp
(NaOH pure content = 63 molar equivalents above the pure content) was added at once and stirring was continued for 1 hour at room temperature. The double salt was hydrolyzed and turned into a cobalt hydroxide precipitate slurry with good flocculation and sedimentation properties. did.

Next, after adding 50 ppil of a polymer flocculant ("Sunfloc P-200" manufactured by Sanyo Chemical Co., Ltd.) to this precipitate slurry,
When dehydration was performed using a suction type Buchner funnel with a mouthpiece set and a mouth area of 615 cR2, a raw dehydrated cake of 9.5 Kp with a moisture content of 76 inches was obtained in about 8 hours.

Next, the unrefined dehydrated cake was loosened finely and placed in a hot air dryer at 200°C for 5 hours, after which the mesh size was Q, 5.
When the mixture was passed through a pulverizer (fine type sample AP-8 type) equipped with a ysmφ screen, unrefined dry cobalt hydroxide powder (water content 3%) was obtained.

The composition of this powder is Co=51% and Na=6.2
%Met.

Next, the unpurified cobalt hydroxide powder was dispersed in 201 ml of pure water, stirred for 1 hour, and then applied to a centrifugal dehydrator with a rotation speed of 3.00 rpm.
1 was sprayed using a shower set for 2 hours, and then the washing and dehydration operation was completed by rotating the shower for an additional 0.5 hour.

The Na ion concentration in the centrifuged water at this final stage was 11 ppm.

Next, the purified cobalt hydroxide water-containing cake obtained above was
After treatment in a hot air dryer at 00°C for 3 hours, firing in an electric furnace at 800°C for 1 hour resulted in Co = 73.39% (Co
s04 equivalent 99.9%), Na =0.004%
The high purity tricobalt tetroxide is 1.45? Obtained.

Comparative Reference Example 4 When 100 ppm of a polymer flocculant was added to the basic cobalt carbonate double salt precipitated slurry obtained in the first half of Example 3 and dehydration was performed using the same Buchner funnel as in Example 3, the water content was 80%. It took more than 30 hours to achieve this, and the dehydration properties were extremely poor.

Claims (1)

[Claims] Cobalt hydroxide obtained by reacting an alkali hydroxide in an amount equivalent to or more than 1.2 times the amount of divalent cobalt ions on a divalent cobalt salt aqueous solution and/or divalent cobalt double salt slurry is dehydrated and dried, and then This dried material is treated in an aqueous system to bring the concentration of alkali metal ions in the washing water to 200 pH.
A method for producing high-purity tricobalt tetroxide, which comprises washing with water until it becomes less than 1[l], followed by dehydration, drying, and, if necessary, calcination.