JP3275681B2 - Production method of high purity scandium oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-purity scandium oxide from a rare earth metal, particularly a substance containing trace amounts of scandium (Sc). This method relates to a method for producing high-purity scandium oxide after selectively leaching scandium under high temperature and high pressure and then selectively extracting scandium with a chelating resin to form a scandium precipitate with a precipitant. is there.

The present invention is particularly useful for producing high-purity scandium oxide of scandium from an oxidizing substance containing a large amount of iron, aluminum, and silicon.
High-purity scandium oxide of 95% or more can be efficiently produced from a substance contained in a trace amount of about% by weight.

[0003]

2. Description of the Related Art Scandium is used for high color rendering lamps in metal halide lamps used in gymnasiums, hotels, etc., as an additive to single crystals for lasers as a solid-state laser oscillation source, and as a long cathode ray tube for displays. Used for light orange phosphors.

In recent years, as a new use of scandium, scandium is very promising as a Lewis acid catalyst utilizing a rare earth compound as a kind of Lewis acid, and is expected to be greatly developed as a new catalyst for the next generation. I have.

Scandium is found in the crust at 5 to 10 pp.
m or so, scandium alone is almost no industrially available ore, and currently has very poor enrichment.

[0006] Substances containing trace amounts of scandium include tungsten, tin, uranium smelting residue, ferronickel smelting slag, coal ash, red mud, etc., but those currently used as commercial resources are mainly It is a tungsten, tin and uranium smelting residue.

[0007] Conventional scandium recovery techniques include:
For example, tungsten is extracted from tungsten ore by alkali treatment, but scandium remains in the residue.

[0008] The residue is dissolved in acid to leach out scandium. At this time, after leaching under atmospheric pressure, scandium is separated and recovered by a solvent extraction method, a chelate, an ion exchange method, or the like to obtain high-purity scandium oxide. Manufacturing.

According to this method, in order to increase the leaching rate of scandium to 90% or more, leaching with sulfuric acid of 6 M or more at a temperature of 90 to 100 ° C. for 60 hours or more is required. At the same time, 80% or more of the iron and aluminum is leached, and the concentration of iron and aluminum in the leachate is several hundred times higher than that of scandium, so that the acid consumption is extremely large. Further, according to this method, about 15% of silicon is also leached, and this becomes gel-like, which makes filtration of the liquid difficult.

[0010] In the solvent extraction method for producing high-purity scandium oxide from the leachate, a clad (third gel-like phase) is formed, and in the chelate extraction and ion exchange methods, clogging and aeration are caused. In addition, the following liquid treatment becomes complicated, and there is a problem not only in terms of economy but also in terms of operation.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to control the leaching of iron, aluminum and silicon, which are contained in a large amount other than scandium, from a substance containing a small amount of scandium, and preferentially acid leaching scandium. Significantly reduces acid consumption, and at the same time, greatly improves the solid-liquid separation of the leachate and leach residue, and eliminates clogging and poor air permeability during chelate extraction, making it economically efficient and high-purity scandium oxide. Is provided.

[0012]

Therefore, the present inventor has conducted various studies to avoid the above-mentioned inconveniences and to efficiently and economically produce scandium oxide of high purity from scandium-containing oxides. As a result, it has been found that when acid leaching is performed at high temperature and high pressure in an oxidizing atmosphere, leaching of iron, aluminum and silicon is controlled, while almost all of scandium is selectively and efficiently leached.

Further, since this leachate contains only a small amount of iron, aluminum and silicon, a scandium-containing solution having good filterability is obtained in the solid-liquid separation of the leachate and the leach residue. In the subsequent purification of a series of scandium in chelate extraction, it was found that high-purity scandium oxide can be easily produced because scandium is preferentially efficiently extracted and separated without clogging or poor air permeability. Invented the invention.

Hereinafter, the present invention will be described in detail for each step.

In the present invention, the oxide containing a small amount of scandium, for example, about 0.001 to 0.4% by weight, may be any oxide containing scandium, and is not particularly limited. % Iron, 2-10
% Aluminum and 2-20% silicon.

Therefore, in order to efficiently leach scandium from a substance containing a small amount of scandium in the leaching step, the leaching of iron, aluminum and silicon is controlled as much as possible during acid leaching, and sulfuric acid is selected depending on the type of acid used. Scandium must be selectively leached as a solution of chlorides, chlorides, nitrates and the like.

The leaching of iron, aluminum and silicon can be controlled by acid leaching under high temperature and high pressure in an oxidizing atmosphere using an autoclave.

The temperature at the time of acid leaching is 150 ° C. or more, and the pressure is 5
kg / cm ² or more, especially 220 ° C. to 260 ° C.
C. and a range of 24 to 48 kg / cm ² are preferable. Thereby, leaching of iron, aluminum and silicon is suppressed.

In order to make the atmosphere oxidizing, Fe ₂
It can be achieved by the action of oxides such as O ₃ and Al ₂ O ₃ , but can be easily achieved by blowing oxygen or air into the autoclave.

The maintenance of high temperature and high pressure is easily achieved by blowing steam into the autoclave.

In order to promote the leaching reaction, the leaching reaction can be completed within one hour by stirring with an impeller in addition to the steam stirring with the steam.

As the acid used, any of sulfuric acid, hydrochloric acid and nitric acid can be used, but sulfuric acid is most preferable in view of the corrosiveness of the autoclave material. The amount of acid used is such that the pH of the leachate after acid leaching under high temperature and high pressure is 1 at room temperature.
It is adjusted so as to be before and after.
The H range is preferred.

When the pH is less than 0.5, the amount of acid used increases, and the leaching rate of iron, aluminum and silicon other than scandium increases. On the other hand, when the PH exceeds 2.0, the leaching rate of scandium decreases. The yield decreases.

By acid leaching under the above conditions, 95% or more of scandium is leached, and leaching of iron, aluminum and silicon is 5% and 10%, respectively.
And 5% or less.

The scandium-containing acid leaching solution obtained by the present invention has a low concentration of iron, aluminum, and silicon. Particularly, since a low silicon concentration solution is obtained, gelation of the leaching solution by silicon is controlled. Filtration separation from the residue is greatly improved.

In the solution adjusting step, the acid leachate containing scandium obtained according to the present invention is treated with sodium carbonate,
Using alkali such as calcium carbonate, ammonium carbonate, sodium hydroxide, calcium hydroxide, aqueous ammonia, magnesium carbonate, magnesium hydroxide, calcium oxide, magnesium oxide, etc.
Is adjusted to a range of 1 to 4, preferably 1.5 to 2.5.

Thereafter, a redox solution is prepared by using a reducing agent such as hydrazine, sodium hydrogen sulfide, sodium sulfide, ammonium sulfide, hydrogen sulfide gas, or sulfur dioxide to adjust the oxidation-reduction potential to 200 mV or less.

By adjusting the pH to this value, trivalent Fe
Almost all and part of Al are removed by precipitation.
All of the scandium remains in solution. Further, by setting the oxidation-reduction potential to 200 mv or less, F
e can be divalent in total.

In the extraction step, almost all of the scandium is adsorbed by bringing the liquid thus adjusted into contact with the chelate resin, but the adsorption rate of Fe and Al is controlled to about 3 to 10%, and Is not adsorbed at all and remains in the whole liquid. Other elements such as Mn, Mg, and Ca are not adsorbed similarly to Si, and the entire amount remains in the liquid.

In the washing step, washing is carried out with a dilute acid having a pH of 0.5 to 7.0 in order to remove all the adjusting solution remaining in the scandium-adsorbed chelate resin. By performing the treatment at a pH in this range, the resin can be washed while the scandium is adsorbed on the chelate resin.

In the back extraction step, 1N or more, preferably 3
By contacting with a strong acid of N or more, the entire amount of scandium is eluted from the scandium-adsorbed chelating resin. At this time, F partially adsorbed together with scandium
e and Al are also completely eluted.

A series of methods from extraction with a chelate resin to washing and back-extraction can be easily carried out by continuously supplying an adjusting solution, a dilute acid solution and a strong acid solution into a chelate resin packed in a column. .

Further, scandium is eluted from the chelating resin by the strong acid solution. At this time, the amount of scandium eluted changes with time depending on the supply amount of the strong acid solution. Thus, compared to the scandium concentration in the preparation solution,
Concentration ratios as high as 100 times are possible. On the other hand, impurities such as Fe and Al show almost the same change over time as scandium, but the adsorption rate itself is low, so that the concentration is lower than these concentrations in the adjusting solution.

Therefore, by repeating the scandium-containing liquid obtained in the back extraction step from the liquid preparation step to the back extraction step again, a high-concentration scandium liquid containing few impurities such as Fe and Al can be obtained.

In the precipitation step, after adjusting the pH of the solution to a range of 0.5 to 7.0, scandium oxalate is prepared with a precipitant such as oxalic acid, ammonium oxalate, sodium carbonate, ammonium carbonate, sodium hydroxide, and aqueous ammonia. As a result, a precipitate of a high-purity scandium compound such as scandium carbonate is obtained.

At this time, by adjusting the liquid PH in the case of using oxalic acid (salt) preferably in the range of 1 to 3, almost the entire amount of scandium can be recovered as high-purity scandium oxalate.

On the other hand, the liquid PH in the case of using an alkali such as sodium carbonate or ammonia water other than oxalic acid (salt)
By adjusting the amount to preferably 5 to 6, almost all of scandium can be recovered as high-purity scandium carbonate or high-purity scandium hydroxide.

In the firing step, high-purity scandium oxalate, high-purity scandium carbonate or high-purity scandium hydroxide is fired at 450 ° C. or higher,
High purity scandium oxide can be manufactured.

[0039]

The present invention will be described below in more detail with reference to examples.

[0040]

Example 1 Leaching residue (Fe; 42%, Mn;
7%, Al: 2.5%, Si: 3.3%, Sc: 0.0
(15%) was made into a 25% slurry with water, 165 g of 98% sulfuric acid was added to 1 kg of the dried residue, and the autoclave was leached at a temperature of 240 ° C. and a pressure of 35 kg / cm ² for 1 hour, and then the pressure of the autoclave was reduced to atmospheric pressure. .

The liquid PH at room temperature after leaching is 1.0,
Fe: 1.3 g / l, Al: 0.3 g / l, Mn: 2
2.9 g / l, Si; 0.1 g / l, Sc; 0.055
A leachate with a concentration of g / l was obtained.

The leaching rates of Sc and Mn at this time were 9
The leaching rates of Fe, Al, and Si were 0.8%, 3.5%, and 1%, respectively.

The leachate and the residue were subjected to solid-liquid separation using a filter press at a slurry concentration of 24%.
Residue treatment of 1 kg / m ² · Hr was possible, and the water content at that time was 36%.

This leachate was washed with calcium carbonate to pH
After 2.0, a small amount of sodium hydrosulfide was added to adjust the oxidation-reduction potential to 50 mv.

As a result, 55% of Fe, Al, Si
30% and 20% were removed by precipitation, and almost all of Sc remained in the solution. The concentration of this adjusted solution was Fe: 0.6 g / l, A
0.2 g / l; Mn; 22.3 g / l; Si;
08 g / l, Sc; 0.053 g / l.

When this adjusted liquid was passed through a cylindrical column filled with a terminal H-type chelate resin, the amount of the liquid was 5 times the resin volume, 98% of Sc was adsorbed in the resin because of good water flow. However, Fe and Al were only 6% and 4%, and Mn and Si were not adsorbed at all.

Subsequently, the diluted sulfuric acid solution having a pH of 2.0 was washed with 1/3 of the amount of the adjusted solution, and then 5N sulfuric acid was washed with the 1/2 of the adjusted solution to remove Sc from the resin. Eluted.

When the region of high concentration of Sc in the eluent with 5N sulfuric acid was separated by 2/25 times the amount of the adjusted solution, 0.58 g / l of Sc and 0.38 g / l of Fe were added.
1; a Sc-containing liquid having a concentration of 0.10 g / l was obtained.

The Sc-containing solution was adjusted again to pH 2.0 with ammonia water and the oxidation-reduction potential to 50 mv with sodium hydrogen sulfide, and then adsorbed, washed and eluted with a chelating resin under the same conditions as above.

Thus, Sc: 5.85 g / l, F
e: 0.24 g / l, Al: 0.04 g / l, a high-concentration Sc high-purity liquid was obtained.

After this solution was adjusted to pH 1.5 with aqueous ammonia, scandium oxalate was obtained at a precipitation recovery of 98% by using 1.1 equivalents of oxalic acid with respect to the Sc amount.

When this scandium oxalate was calcined at 800 ° C. for 2 hours, high purity scandium oxide of 99.9% was obtained.

[0053]

Example 2 Fe obtained in Example 1; 0.6 g / l,
Al; 0.2 g / l, Mn: 22.3 g / l, Si;
0.08 g / l, Sc; 0.053 g / l of the adjusting solution
After passing 5 times the amount of liquid with respect to the resin volume through the cylindrical column filled with the terminal H-type chelate resin to adsorb Sc into the resin, the diluted hydrochloric acid solution having a pH of 1.5 was subsequently adjusted to the adjusted liquid amount. And 1/3 volume of water-washing.

Thereafter, 3N hydrochloric acid was added to a half of the prepared solution.
Sc was eluted from the resin by passing twice the amount of water. The Sc high concentration liquid region of the eluent with 3N hydrochloric acid is 1/15 of the adjusted liquid amount.
When it was collected by double amount, Sc; 0.70 g / l, F
e; 0.42 g / l, Al; 0.10 g / l, concentration S
A c-containing liquid was obtained.

The Sc-containing hydrochloric acid solution was adjusted again to pH 2.0 with ammonia water and the oxidation-reduction potential to 50 mv with sodium hydrogen sulfide, and then adsorbed, washed and eluted with a chelating resin under the same conditions as above.

Thus, Sc: 8.74 g / l, F
e; a high-concentration Sc high-purity liquid of 0.20 g / l and Al; 0.02 g / l was obtained.

This solution was adjusted to pH 5.5 with aqueous ammonia to precipitate and recover the entire amount of Sc as hydroxide.

The scandium hydroxide was heated at 700 ° C. for 3 hours.
After firing for 98 hours, high purity scandium oxide of 98% was obtained.

[0059]

COMPARATIVE EXAMPLE The tungsten leaching residue of the component used in Example 1 was adjusted to a 15% slurry concentration with water, and 1200 g of 98% sulfuric acid was added to 1 kg of tungsten leaching residue and leached at a temperature of 95 ° C. for 80 hours. , The pH of the leached solution is 0.5, and the concentration of the leached solution is 54.3 g of Fe;
/ L, Al; 3.2 g / l, Mn; 9.5 g / l, S
i: 0.8 g / l, Sc: 0.022 g / l.

At this time, the leaching rates of Sc, Fe, Mn, Al, and Si were 91%, 82%, 85%, 80%,
15%.

When the leachate and the residue were subjected to solid-liquid separation by a filter press, filtration was impossible with only 5 minutes of water flow.

At this time, the residue treatment amount was 0.2 kg / m ² , and the water content after filtration was 76%.

[0063]

According to the present invention, almost all of scandium can be preferentially leached without substantially leaching iron, aluminum and silicon from a scandium-containing substance containing a large amount of iron, aluminum and silicon. As a result, the acid consumption is greatly reduced, and the economic effect is very large.

Further, since this leachate contains only a small amount of iron, aluminum and silicon, a scandium-containing solution having good filterability can be obtained in the solid-liquid separation of the leachate and the leach residue. In the subsequent purification of a series of scandium in chelate extraction, scandium can be preferentially and efficiently extracted and separated without clogging or poor air permeability.
% Of high-purity scandium oxide can be easily and efficiently obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromasa Yakushiji Hachinohe City, Aomori Prefecture Ohara Kawaragi character Toyama Nitta (without address) Taiheiyo Metal Co., Ltd. Hachinohe Works (56) References JP-A-3-173725 ( JP, A) JP-A-1-133920 (JP, A) JP-A-1-108119 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (2)

(57) [Claims] 1. A method for producing high-purity scandium oxide from an oxide containing 0.001 to 0.4% by weight of scandium. Step 1: Using an oxide containing a small amount of scandium in an oxidizing atmosphere at a high temperature of 150 ° C. or more . A leaching step of selectively leaching scandium into an acidic aqueous solution under a high pressure of 5 kg / cm ² or more to obtain a scandium-containing solution; and step 2 comprising the scandium-containing solution obtained in step 1. Solution is P
After adjusting H to 1 to 4, a liquid adjusting step of using a reducing agent selected from the group consisting of hydrazine, sodium hydrogen sulfide, sodium sulfide, ammonium sulfide, hydrogen sulfide gas, sulfur dioxide gas, and a combination thereof to form a reducing liquid. And an extraction step of contacting the adjusted liquid obtained in step 3 with the chelate resin to form a chelate resin adsorbing scandium; and a step in which the scandium-adsorbed chelate resin obtained in step 4-step 3 has PH A washing step of washing with a dilute acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and a combination thereof of 0.5 to 7.0, and the scandium-adsorbed chelate resin obtained in step 5 to step 4 is 1N or more. Scandium is eluted from the chelating resin with a strong acid selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid and a combination thereof. A back extraction step of obtaining a chromatic solution, a scandium-containing solution obtained in step 6 step 5 P
H, a scandium-containing oxide comprising: a precipitation step of obtaining a scandium precipitate with a precipitant after adjusting to a range of 0.5 to 7.0; and a step of firing the scandium precipitate obtained in steps 7 to 6. For producing high-purity scandium oxide from 2. After performing the step 1, the scandium-containing solution obtained by repeating the operations of the steps 2 to 5 one or more times sequentially is subjected to the next step 6. The method according to claim 1.