JPS5948870B2 - Method for producing lithium hydroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing lithium hydroxide, particularly a method for producing high-purity lithium hydroxide by an electrolytic method using a diaphragm using lithium carbonate as a raw material.

Lithium hydroxide is used as a raw material for manufacturing greases, batteries, etc., photographic developers, other alkali sources, etc., and it is desirable that these all have high purity.

Conventionally, lithium hydroxide has been produced by, for example, carbonating sposiumene, a raw ore of lithium, to form lithium carbonate, and reacting this with milk of lime.

However, the lithium hydroxide thus obtained contains some unreacted lime milk and other impurities.

For this reason, the lithium hydroxide obtained by the above reaction is usually evaporated and concentrated to crystallize, centrifuged and washed with water, and then the crystals are redissolved and an adsorbent such as activated carbon is added. Impurities are removed by separating the colored substances together with the adsorbent using a separator such as a filter press, recrystallizing them, washing them with water, and separating them by centrifugation.

This method requires a large amount of steam and heat due to repeated crystallization, dissolution, and crystallization, and has drawbacks such as complicated operations and relatively high costs.

The inventor of the present invention has conducted various research and examinations with the aim of eliminating the drawbacks of these conventional methods and easily obtaining high-purity lithium hydroxide from lithium carbonate, and as a result, has developed a method for reacting lithium-containing minerals or lithium carbonate with sulfuric acid. By electrolyzing this using the diaphragm method, lithium hydroxide is produced on the cathode side and sulfuric acid is produced on the anode side.The obtained sulfuric acid is reacted with lithium-containing minerals or lithium carbonate to produce lithium sulfate. It has been found that the above objective can be achieved by recycling the process to the process of obtaining . Examples of lithium-containing minerals that can be used in the present invention include spodiumen,
These include lepidolite, ambrigonite, and petalite.

Lithium carbonate can be obtained by reacting these lithium-containing minerals with sulfuric acid after firing, extracting this with water, adding soda ash and slaked lime to the resulting lithium sulfate, and removing impurities such as iron and aluminum. It is obtained by concentrating it and reacting it with soda ash. The lithium carbonate is then reacted with sulfuric acid to produce lithium sulfate. Most of the coexisting impurities in the lithium sulfate obtained by either method become sulfate, and the solubility decreases significantly in the coexistence with lithium sulfate, making it easy to separate. is immediately subjected to electrolysis using the diaphragm method. Diaphragm electrolysis is a method in which electrolysis is performed in an electrolytic cell with an anode and a cathode separated by a diaphragm. As the diaphragm used, for example, a so-called filtration diaphragm made of asbestos or porous fluororesin can be used, but in order to obtain lithium hydroxide with higher purity or higher concentration, an ion exchange membrane is used. is preferable. The ion exchange membrane used is
For example, it is made of a polymer containing a cation exchange group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a phenolic hydroxyl group, and it is particularly preferable to employ a fluorine-containing polymer as such a polymer. Examples of fluorine-containing polymers containing ion-exchange groups include those that react with vinyl monomers such as tetrafluoroethylene and chlorotrifluoroethylene and ion-exchange groups such as sulfonic acid, carboxylic acid, and phosphoric acid groups, or that can be converted into ion-exchange groups. A copolymer with a perfluorinated vinyl monomer having a functional group can be suitably used. Also usable are trifluorostyrene membrane polymers into which ion exchange groups such as sulfonic acid groups have been introduced, and styrene divinylbenzene into which sulfonic acid groups have been introduced. Among these, when using monomers that can form the polymerized units of (a) and (x) below, it is possible to obtain high-purity lithium hydroxide with relatively high current efficiency. Preferably, x is fluorine, chlorine, hydrogen or -CF3, x'' is X or CF3(CF2)m, and m is 1 to 5;
Y is selected from the following:

Here, P is −{CF2′+−a−(CXX″}−b−{
CF2}-o, and Q is -(CF2-0-CXX″'
+-, and R is →CXX''-0-CF2'+-8, and (P, Q, R) represents that at least one of P, Q, and R is arranged in an arbitrary order.

X, X'' are the same as above, n = 0 to 1, a, b, c
, d and e are O~6.

A is -COOH or -CN, -COF, -COORl,
Indicates a functional group that can be converted to -COOH by hydrolysis or neutralization, such as -COOM and -CONR2R3. R1
is an alkyl group having 1 to 10 carbon atoms, M is an alkali metal or a quaternary ammonium group, and R2 and R3 are hydrogen or an alkyl group having 1 to 10 carbon atoms. Preferred representative examples of the above Y include the following, in which A has a structure in which A is bonded to carbon containing fluorine. X, y, z
are both 1 to 10, and Z and Rf are 1F or carbon number 1 to
A group selected from 10 perfluoroalkyl groups,
A is the same as above.

In the case of a copolymer consisting of the polymerized units of (a) and (1) above, in order for the membrane to achieve the above ion exchange capacity, the polymerized units of (1) are preferably 1 to 40 mol%, particularly 3 to 40% by mole. 2
Preferably it is 0 mol%. The ion exchange resin membrane of the present invention can be obtained by copolymerizing a fluorinated olefin monomer with a polymerizable monomer having a carboxylic acid group or a functional group that can be converted into a carboxylic acid group, as described above. It is composed of the obtained non-crosslinkable copolymer, and its molecular weight is preferably about 3,000 to 300,000 parts, particularly preferably 10,000 to 300,000 parts.
It is 100,000.

In addition, the thickness of the ion exchange resin membrane used is 20 to 600 mm.
It is appropriate to use microns, preferably about 50 to 400 microns.

Further, as the anode, for example, a corrosion-resistant electrode made of a corrosion-resistant core material such as titanium or tantalum coated with ruthenium oxide, or an electrode made of platinum, lead, or the like can be used.

Further, as the cathode, for example, iron, nickel, suanreth, etc. can be used as appropriate.

For electrolysis, an aqueous solution of lithium sulfate having a concentration of about 0.1 to 6N is suitable.

If the concentration is lower than the above range, the concentration of lithium hydroxide obtained will be low and it will be expensive to concentrate, while if it exceeds the above range, some crystals of lithium sulfate will precipitate in the anode chamber during electrolysis. This is not desirable as there is a risk.

In the case of employing 1 to 6N in the above range, it is particularly preferable because the power efficiency of the obtained lithium hydroxide is good and there is no crystal precipitation of lithium sulfate. In addition, the electrolytic voltage during electrolysis is 3 to 6 V, and the current density is 1 to 100 A/Dm.
The degree is appropriate.

It is thus possible to obtain lithium hydroxide with a concentration of 5 to 10% by weight. When the voltage is lower than 3V and the current density is lower than 1A/Dm2, the production amount of lithium hydroxide per unit floor area is low, and on the other hand, when the voltage exceeds 6V and the current density exceeds 100A/Dm. Neither is preferable because the temperature of the electrolyte increases and water evaporates, which may result in the precipitation of lithium sulfate crystals.
In the above range, the electrolytic voltage is 4 to 5.5 V, and the current density is 3.
It is particularly preferable to use .about.40 A/Dm., since the power efficiency can be maximized and the concentration of the obtained lithium hydroxide can be relatively high.

For electrolytic formation, the so-called two-chamber method is usually adopted, which has an anode chamber and a cathode chamber separated by a diaphragm as described above, but the method is not limited to this, and if desired, two or more diaphragms may be used. The so-called 3 type has an anode chamber, an intermediate chamber, and a cathode chamber separated by
There is no problem in adopting a method called a chamber method or a multi-chamber method.

5 Next, the present invention will be specifically explained with reference to Examples. Example 1 The anode effluent (mixed solution of sulfuric acid and lithium sulfate) described later was supplied to a container equipped with a stirrer, and lithium carbonate (analytical values: 300 ppn of chlorine, 2000 ppn of sulfate) was added.
Hemagnesium 4M 500ppn. Calcium 1000p
A 5N lithium sulfate aqueous solution was prepared by reacting the pr0 powder and adding the required amount of water.

As a result of removing impurities in this lithium sulfate aqueous solution by filtration, the impurity content was found to be 20p of chlorine and 10p of magnesium.
ppn, calcium 10pIXn. This solution is used as an anode; platinum; as a cathode; SUS3O4, C2F4 and CF2=
A cation exchange membrane with an effective membrane area of 25 dm2 obtained by hydrolyzing a membrane material (300 micron thick, ARl. 48) made of a copolymer of CF-0-(CF2)3C00CH3 was heated to 80°C. It was supplied to the anode chamber of the electrolytic cell held at a rate of 8.11/Hr.

On the other hand, the cathode chamber was filled with 3N lithium hydroxide aqueous solution and electrolysis was started at a current density of 20A/Dm.
．． Water was supplied at a rate of 31/Hr, and a 3N lithium hydroxide aqueous solution was continuously extracted from the cathode chamber at a rate of 4.51/Hr. The aforementioned mixed aqueous solution of sulfuric acid and lithium sulfate (13.5 g equivalent of sulfuric acid, 27.0 g equivalent of lithium sulfate, 6.31 g of water per hour) was continuously extracted from the anode chamber side and sent to the lithium carbonate reaction vessel. As a result of analyzing the obtained lithium hydroxide, it was found that 1 ppn of chlorine and 300 ppn of sulfate were found as impurities based on solid lithium hydroxide. It was found that it contained 10 ppn of calcium and wm of magnesium. In this case, the production ratio of lithium hydroxide to the amount of electricity supplied, that is, the current efficiency, was 74%, and the sliding voltage was 5.3V. Example 2 A 5N lithium sulfate aqueous solution was added to the anode chamber at a rate of 7.71/Hr.
Electrolysis was carried out under the same conditions as in Example 1, except that water was supplied to the cathode chamber at a ratio of 2.21/Hr,
4N lithium hydroxide aqueous solution from the cathode chamber at 3.21%
Obtained at the rate of Hr.

The anode effluent at this time consisted of 12.8 g equivalent of sulfuric acid, 25.6 g equivalent of lithium sulfate, and 6.1 kg of water per hour, and was sent to the lithium carbonate reaction vessel. Further, the current efficiency at this time was 69%, and the sliding voltage was 5.2. Example 3 A 5N lithium sulfate solution was placed in the anode chamber.6.
61/Hr, and water was supplied to the cathode chamber at a rate of 1.41/Hr.
Electrolysis was carried out under the same conditions as in Example 1, except that 5N lithium hydroxide aqueous solution was supplied from the cathode chamber at a ratio of
．． It was obtained at a ratio of 21/Hr.

The anode effluent at this time consisted of 11.0 g equivalent of sulfuric acid, 22.0 g equivalent of lithium sulfate, and 5.4 kg of water per hour, and was sent to the lithium carbonate reaction vessel. Further, the current efficiency at this time was 60%, and the sliding voltage was 5.1V. Example 4 Electrolytic current density was 30 A/Dm2, lead was used for the anode, 5N lithium sulfate aqueous solution was placed in the anode chamber at a rate of 11.51 small r, and water was placed in the cathode chamber at a rate of 3.21/Hr. Electrolysis was carried out under the same conditions as in Example 1, except that 4N lithium hydroxide solution was supplied from the cathode chamber at 4.81/Hr.
obtained at a rate of

The anode effluent at this time consisted of 19.2 g equivalent of sulfuric acid, 38.4 g equivalent of lithium sulfate, and 9.2 kg of water per hour, and was sent to the lithium carbonate reaction vessel. Example
5 Example except that the electrolytic current density was 40 A/Dm, a 5N lithium sulfate aqueous solution was supplied to the anode chamber at a rate of 13.21/Hr, and water was supplied to the cathode chamber at a rate of 2.81/Hr. Electrolysis was carried out under the same conditions as in 1, and a 5N lithium hydroxide solution was obtained from the cathode chamber at a ratio of 4.41/Ylr.

The anode effluent at this time consisted of 22.0 g equivalent of sulfuric acid, 44.0 g equivalent of lithium sulfate, and 10.7 kg of water per hour, and was sent to the lithium carbonate reaction vessel. Example 6 The electrolysis temperature was 90°C, 5N lithium sulfate was added to the anode chamber at a rate of 8.61/Hr, and water was added to the cathode chamber at a rate of 3.51/Hr.
Electrolysis was carried out under the same conditions as in Example 1, except that the solution was supplied at a rate of r, and a 3N lithium hydroxide solution was obtained from the cathode chamber at a rate of 4.81/Hr.

The anode effluent at this time consisted of 14.4 g equivalent of sulfuric acid, 28.8 g equivalent of lithium sulfate, and 6.8 kg of water per hour, and was sent to the lithium carbonate reaction vessel. Example 7 α-spodiumene as a source of lithium sulfate
After heating to 00℃ to make β-spodium, this β-
After heating the spodumene to 250°C and adding sulfuric acid, extract the lithium sulfate with water, add soda ash and slaked lime to this extract, filter out calcium and magnesium, and prepare a 5N aqueous lithium sulfate solution. The following was used.

Claims (1)

[Claims] 1. Lithium sulfate is obtained by reacting lithium-containing minerals or lithium carbonate with sulfuric acid, and this is electrolyzed by a diaphragm method to produce lithium hydroxide on the cathode side and sulfuric acid on the anode side, A method for producing lithium hydroxide, characterized in that the obtained sulfuric acid is recycled to a step of reacting with lithium-containing minerals or lithium carbonate to obtain lithium sulfate. 2 Lithium-containing minerals include spodiumen, lepidolite,
The method for producing lithium hydroxide according to claim 1, which is at least one selected from ambrigonite and petalite. 3. The concentration of lithium sulfate used for diaphragm electrolysis is 0.
The method for producing lithium hydroxide according to claim 1, wherein the lithium hydroxide is 1 to 6N. 4 Electrolysis using the diaphragm method uses an electrolytic voltage of 3 to 6 V and a current density of 1
The method for producing lithium hydroxide according to claim 1, which is carried out at ~100 A/dm^2. 5. The method for producing lithium hydroxide according to claim 1, wherein the diaphragm used for electrolysis by the diaphragm method is a fluorine-containing cation exchange resin membrane.