JPH09143589A - Method for concentrating, separating and recovering rare earth metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve recovery efficiency and cost effectiveness by subjecting metal oxides contg. trace scandium, such as tungsten, stannum and uranium refining residues, to acid exudation at and under a high temp and high pressure at the time of separating and recovering the scandium. SOLUTION: The oxides contg. the trace scandium of about 0.001 to 0.4wt.% are charged together with an inorg. acid into a pressure vessel where oxygen or air is blown to maintain an oxidative atmosphere. The oxides are then subjected to an agitation treatment at and under the high temp. and high pressure of 150 to 260 deg.C and 5 to 48kg/cm<2> , by which the scandium is selectively leached into the acidic soln. The acidity of the scandium-contg. liquid is thereafter adjusted to pH4 to 6 to concentrate and settle the scandium. The scandium is thus recovered. While the inorg. acid to be used may be any of sulfuric acid, hydrochloric acid and nitric acid, the sulfuric acid is more preferable in terms of the corrosiveness to the vessel. The acidity of the ordinary temp. leaching liquid after the treatment of pH1 is the target for the adequate amt. of use. By such concentration and sepn., >=95% of the scandium may be leached.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrating and separating and recovering scandium from a rare earth metal, especially a material containing a trace amount of scandium (Sc). The present invention relates to a method for selectively leaching scandium under high pressure and then obtaining a concentrated precipitate of scandium with a precipitating agent.

The present invention is particularly useful for concentrating and separating and recovering scandium from an oxide substance containing a large amount of iron, aluminum and silicon. According to the present invention, scandium is contained in an amount of, for example, about 0.001 to 0.4% by weight. From the substance contained in a trace amount, a hydroxide or carbonate containing a high concentration of scandium of about 1 to 10% by weight can be obtained.

[0003]

2. Description of the Related Art Scandium is used as an encapsulant for metal halide lamps used in gymnasiums and hotels as high color rendering lamps, additives to single crystals for lasers as solid-state laser oscillation sources, and long-lasting cathode ray tubes for displays. Used in 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 type of Lewis acid, and it is expected to develop greatly as a new catalyst for the next generation. There is.

Scandium is 5-10 ppm in the crust
Although it is contained to some extent, there is almost no ore that can be industrially used by scandium alone, and the present situation is that the concentration property is very poor.

As an oxide containing a trace amount of scandium, scandium is typically 0.001 to 0.4.
There are tungsten, tin, and uranium smelting residues containing about wt% and ferro-nickel smelting slag, coal ash, red mud, etc., but the currently used commercial resources are mainly tungsten, tin and uranium smelting residues. Is.

As a conventional scandium recovery technique,
For example, tungsten is extracted from tungsten ore by alkali treatment, but scandium remains in the residue.

The residue is acid-dissolved to leach out scandium, which is leached under atmospheric pressure and then separated and recovered by solvent extraction, chelate and ion exchange methods.

According to this method, in order to increase the leaching rate of scandium, iron and aluminium, which are contained in large amounts other than scandium, are leached at the same time, and the concentration of iron and aluminium in the leaching solution is several hundred times that of scandium. Therefore, not only the acid consumption becomes very large, but according to this method, silicon is also leached out, which causes gelation and makes it difficult to filter the liquid. (3rd phase), causing clogging and poor air permeability in the chelate and ion exchange methods, and the subsequent liquid treatment becomes complicated.
There were problems not only in terms of economy but also in terms of operation.

[0010]

The present invention is to control the leaching of iron and aluminum and silicon which are contained in a large amount in addition to scandium from a substance containing a small amount of scandium, and preferentially leaching scandium with acid,
An economically efficient method for concentrating, separating and recovering scandium is provided.

[0011]

Therefore, the present inventor has conducted various studies to avoid the above-mentioned inconvenience and to efficiently concentrate and recover scandium from an oxide containing a small amount of scandium, and as a result, the oxidizing atmosphere We have found that the acid leaching under high temperature and high pressure controls the leaching of iron, aluminum and silicon, while the leaching of almost all of the scandium is selectively and efficiently leached.

Further, since this leachate contains only a small amount of iron, aluminum and silicon, when a precipitate of scandium is obtained by a precipitant in the subsequent liquid treatment, a high temperature scandium hydroxide having good filterability is obtained. As a result, they have found that they can be recovered as carbonates and have reached the present invention.

The present invention will be described in detail below.

A small amount of scandium in the present invention, for example, 0.001 to 0.4% by weight, preferably 0.0
More than 06 to 0.4% by weight, more preferably 0.01 to
The oxide contained at about 0.4% by weight is not particularly limited as long as it contains scandium, but is usually 5 to 50% iron, 2 to 10% aluminum, and 2 to 20%. Contains% silicon.

Therefore, in order to efficiently concentrate and recover scandium from a substance containing a trace amount of scandium,
During acid leaching, it is necessary to control leaching of iron, aluminum and silicon as much as possible to selectively leached scandium.

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.

During the acid leaching, the temperature is 150 ° C. or higher and the pressure is 5
kg / cm ² or more is required, especially 220 ° C to 260
The temperature is preferably in the range of 24 to 48 kg / cm ² . This suppresses the leaching of iron, aluminum and silicon.

To make an oxidizing atmosphere, Fe ₂
This can be done by the action of oxides such as O ₃ and Al ₂ O _3, but it can be easily done by blowing oxygen or air into the autoclave.

In order to maintain high temperature and high pressure, it is easily achieved by blowing steam into the autoclave.
In order to accelerate the leaching reaction, it is possible to complete the leaching reaction within 1 hour by stirring with an impeller in addition to the steam stirring with the steam.

The acid used may be sulfuric acid, hydrochloric acid or nitric acid, but sulfuric acid is most preferable from the viewpoint of the corrosiveness of the autoclave material. The amount of acid used is 1 at room temperature as the pH of the leaching solution after acid leaching under high temperature and high pressure.
Adjust it so that it is in front and back.

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 controlled to 5% or less.

The acid leaching solution containing scandium obtained by the present invention has a low iron, aluminum and silicon concentration, and since a particularly low silicon concentration solution is obtained, gelation by silicon of the leaching solution is controlled, and the leaching solution and leaching are controlled. Filtration and separability from the residue are significantly improved.

The acid leachate containing scandium obtained according to the present invention is treated with sodium carbonate, calcium carbonate, ammonium carbonate, sodium hydroxide, calcium hydroxide, aqueous ammonia, magnesium carbonate, magnesium hydroxide, calcium oxide, magnesium oxide. A precipitate is obtained as a hydroxide or a carbonate using an alkali such as.

In this case, by adjusting the pH of the leachate to more than 4 to 6, preferably 5 to 6, almost all the amount of scandium can be recovered as a precipitate. 4, preferably 3
After removing iron, aluminum, and silicon as a precipitate with this PH, the pH is adjusted to more than 4 to 6 by the action of alkali to obtain a precipitate as a hydroxide or a carbonate, thereby obtaining a higher concentration. A scandium enriched precipitate can be formed.

This is because almost all iron leached by acid leaching in a high temperature, high pressure oxidizing atmosphere exists as trivalent iron, so that almost all the iron can be removed by precipitation at pH 4 or less. This is because the precipitation removal of about 80% is possible below.

Further, in the case of silicon, the precipitate acts as a coagulant and adheres to the surface of the precipitate to give 75%.
The degree is removed.

On the other hand, scandium has a pH of 4 or less and is almost entirely present in the liquid, and the total amount of the precipitate is formed as hydroxide or hydroxide at PH 5.5, whereby it is possible to concentrate and separate the scandium.

[0028]

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

[0029]

Example 1 Leaching residue (Fe: 42%, Mn :) after leaching tungsten by subjecting a tungsten concentrate to alkali treatment
7%, Al: 2.5%, Si: 3.3%, Sc: 0.0
15%) was made into a 25% slurry with water, 175 g of 98% sulfuric acid was added to 1 kg of the residue, and the mixture was leached with an autoclave 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 0.9,
Fe: 1.6 g / l, Al: 0.4 k / l, Mn: 2
3.4 g / l, Si: 0.2 g / l, Sc: 0.053
A leachate with a concentration of g / l was obtained.

The leaching rates of Sc and Mn at this time are 9 respectively.
The leaching rates of Fe, Al and Si were 1%, 4% and 2%, respectively.

The leachate and the residue were subjected to solid-liquid separation by a filter press at a slurry concentration of 23%.
A residual treatment amount of 9 kg / m ² · Hr was possible, and the water content at that time was 38%.

The leachate was pH adjusted with calcium carbonate.
It was set to 3.8, and Fe and Al were precipitated and removed as carbides.
Along with this, Si was also removed at the same time. The respective precipitation removal rates were Fe: 98%, Al: 80%, and Si: 70%. At this time, the Sc coprecipitation rate was only 3%, and almost the entire amount remained in the liquid.

Next, this solution was treated with sodium carbonate to obtain P
It was set to H5.5 and Sc was precipitated and recovered as a carbonate. The Sc precipitation recovery rate at this time was 100%, and the total amount of Fe and Al and Si: 30% and Mn: 0.3% were simultaneously precipitated,
c: 9.0%, Fe: 5.6%, Al: 13.9%, S
A Sc concentrate of i: 4.0%, Mn: 12.2% was obtained. This concentrate is 600 times more S than the leaching residue after leaching tungsten by subjecting the tungsten concentrate to alkali treatment.
c Concentration ratio was obtained.

[0035]

Example 2 Red mud containing 0.025% Sc (F
e: 48%, Mn: 1%, Al: 2.8%, Si: 3.
8%, Mg: 2.2%) to make a 30% slurry with water, add 205 g of 98% sulfuric acid to 1 kg of red mud, and autoclave the temperature at 240 ° C, pressure 35 kg / cm ^2.
After leaching for 1 hour at 1, the pressure of the autoclave was reduced to atmospheric pressure.

The liquid pH at room temperature after leaching is 0.9,
Fe: 1.5 g / l, Al: 0.4 k / l, Mn: 4.
5 g / l, Mg: 10.1 g / l, Si: 0.4 g / l
l, Sc: 0.012 g / l concentration of leachate was obtained.

The leaching rates of Sc, Mn, and Mg at this time were 94%, 90%, and 92%, respectively, and Fe, Al, and
The leaching rates of Si were 0.5%, 3%, and 2%, respectively.

When this leachate and the residue were subjected to solid-liquid separation with a filter press at a slurry concentration of 32%, 3
A residue treatment of 3 kg / m ² · Hr was possible, and the water content at that time was 30%.

This leachate was treated with calcium hydroxide to form P
It was set to H3.5, and Fe and Al were precipitated and removed as hydroxides. Along with this, Si was also removed at the same time. The respective precipitation removal rates are Fe: 97%, Al: 73%, Si: 70
%Met. The Sc coprecipitation rate at this time was only 2%,
Almost all the liquid remained in the solution.

Next, this solution was adjusted to pH 5.7 with sodium hydroxide to precipitate and recover Sc as hydroxide. At this time, the Sc precipitation recovery rate was 100%, and the total amount of Fe and Al and Si: 25%, Mn: 0.5%, Mg: 0.2%
Simultaneously precipitates, Sc: 2.1%, Fe: 7.9%, A
1: 18.9%, Si: 5.3%, Mn: 4.1%, M
A Sc concentrate of g: 3.5% was obtained. This concentrate had a Sc concentration ratio of 840 times that of the original red mud.

[0041]

According to the present invention, almost all the amount of scandium can be preferentially leached from a scandium-containing substance containing a large amount of iron, aluminum and silicon without leaching almost all of iron, aluminum and silicon. As a result, not only the consumption of acid is greatly reduced and the economic effect is very large, but also the filtration and separation properties of the leachate and the leach residue are good, and it is efficient in terms of operation.

Furthermore, since scandium can be easily separated and recovered as hydroxide or carbonate, a high-concentration scandium precipitate can be obtained.

Since the scandium concentrated precipitate obtained by the present invention is a hydroxide or a carbonate, it can be easily dissolved in an acid to obtain a high-concentration scandium solution. , 9 more
High-purity scandium of 9% or more can be easily and efficiently produced.

Claims (5)

[Claims] 1. When recovering scandium from an oxide containing a trace amount of scandium, the oxide containing a trace amount of scandium is selectively leached into an acidic solution under high temperature and pressure in an oxidizing atmosphere. ,
A method for concentrating, separating and recovering scandium, comprising forming a concentrated precipitate of scandium after obtaining a solution containing scandium, and adjusting the pH of the solution. 2. The temperature for leaching scandium is 150.
The method according to claim 1, wherein the temperature is ℃ to 260 ℃, and the pressure is 5 to 48 kg / cm ² or more. 3. The method of concentrating, separating and recovering according to claim 1, wherein the acidic solution is an aqueous solution of sulfuric acid, nitric acid, or hydrochloric acid. 4. The method of concentrating, separating and recovering according to claim 1, wherein the liquid PH for forming the scandium concentrate is 4 to 6. 5. The scandium enriched precipitate is a hydroxide,
The method of concentrating, separating and recovering according to claim 1, which is a carbonate.