JP2862180B2 - Method for producing lithium adsorbent - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lithium adsorbent, and particularly to a lithium dilute solution which is excellent in selective adsorption to lithium, has a large adsorption capacity and a large adsorption speed, and has a large capacity. TECHNICAL FIELD The present invention relates to a method for producing an inexpensive lithium adsorbent which is stable and less toxic.

[Prior Art] In recent years, metallic lithium and its compounds have been used in a wide range of fields such as ceramics, batteries, absorption type refrigerants, pharmaceuticals and the like. In the future, large capacity batteries, aluminum alloy materials, nuclear fusion fuels, etc. The demand for lithium is expected to increase further in the future (Journal of the Japan Mining Association, Vol. 97, p. 221).

Metallic lithium and its compounds are mainly produced from lithium-containing ores (lithium content of 2 to 6%) such as spodumene, ambrigonitite, petalite, levitrite, or salt lakes with high lithium concentration or underground brine ( Lithium concentration of 50 to 200 ppm) is collected by evaporation method.

In Japan, lithium-containing ores as described above are scarce, and a method for recovering from lithium-containing liquid has not been established. Therefore, the fact is that metal lithium and its compounds all depend on imports. On the other hand, some geothermal and hot spring waters in Japan contain considerable amounts of lithium, and the surrounding ocean also contains trace amounts of lithium (0.17 ppm). Therefore, it is strongly desired to establish a technique for efficiently recovering lithium from a dilute solution containing lithium.

As a part of the technology for recovering lithium from a dilute solution containing lithium, various lithium adsorbents have been proposed (for example, JP-A-61-171535, JP-A-61-278347, and 61-283).
Nos. 341 and 63-80844). According to these, an excellent lithium adsorbent can be obtained by pulverizing a lithium compound and a manganese compound or heating a lithium-containing manganese oxide or a lithium oxide at a predetermined temperature and then eluting lithium with an acid. It is shown.

[Problems to be Solved by the Invention] In order to practically adsorb and recover lithium from a dilute solution containing lithium, it is necessary to have an excellent selective adsorption property to lithium, a large adsorption rate and an adsorption capacity, and a stable solution in a dilute solution. There is a need for the development of a technology that has low toxicity and can be repeatedly adsorbed and desorbed, and that can produce a lithium adsorbent at a high yield in consideration of economics.

When the prior art is examined in consideration of such characteristics, it is difficult to say that all the requirements are satisfied. That is, in the prior art, no consideration is given to the atmosphere during the heat treatment, and there is no indication that the synthesis is performed while forcibly supplying oxygen or air.Therefore, the oxygen required for the reaction tends to be insufficient, There was a problem that the reaction rate was low and the productivity was low. In addition, since the contact reaction area between the raw material and oxygen is particularly small by the conventional heating using the fixed bed method, a large amount of unreacted material remains in the obtained lithium adsorbent. This is the cause of the decrease in lithium adsorption.

The present invention has been made in order to solve such technical problems, and aims to improve the productivity by promoting the synthesis reaction of the adsorbent, and to reduce the unreacted reaction which is the cause of the decrease in lithium adsorption performance. An object of the present invention is to provide a method for producing a lithium adsorbent having a further improved adsorption performance by minimizing the residual amount of the substance.

[Means for Solving the Problems] The present invention, which has achieved the above-mentioned object, means that after pulverizing and mixing a lithium compound and a manganese compound, air or an oxygen-enriched gas is forcibly supplied to the mixture. While controlling so that the oxygen partial pressure becomes 0.20 or more, heat treatment at a temperature of 350 ° C. or more to synthesize a lithium-containing manganese oxide, and elute lithium from the oxide using an acid. It is a method for producing a lithium adsorbent having the same.

[Action] The present inventors have studied from various angles a means for accelerating the synthesis reaction of the lithium-containing manganese oxide and minimizing unreacted substances in the lithium adsorbent.
As a result, after pulverizing and mixing the lithium compound and the manganese compound (the order of pulverization and mixing does not matter; the same applies hereinafter),
In the step of heat-treating the mixture (hereinafter sometimes simply referred to as a raw material), by controlling the oxygen partial pressure to be 0.20 or more while forcibly supplying air or an oxygen-enriched gas into the reactor, The inventors have found that the productivity is remarkably improved, the residual amount of unreacted substances during the heat treatment can be reduced, and a lithium adsorbent having more excellent adsorption performance can be obtained. Thus, the present invention has been completed. That is, according to the study of the present inventor, if the synthesis reaction is performed while maintaining the oxygen partial pressure during the heat treatment at 0.20 or more, the synthesis reaction between the lithium compound and the manganese compound can be promoted, thereby increasing the productivity. And the unreacted substances were reduced. However,
The oxygen-enriched gas in the present invention is intended to include the case of only oxygen. In the present invention, since such a gas is forcibly supplied, the oxygen partial pressure in the reaction atmosphere can be constantly increased to 0.20 or more even if oxygen is consumed by the progress of the reaction. The preferred range of the oxygen partial pressure is 0.25 to 0.5, and the still more preferred range is 0.3 to 0.5. For the total amount of oxygen supply,
The amount is preferably 3 × 10 ⁻⁴ Nm ³ / g or more, more preferably 4 × 10 ⁻⁴ Nm ³ / g or more in terms of oxygen with respect to the raw material without affecting the synthesis time.

Examples of the lithium compound used in the present invention include hydroxides, oxides, carbonates, bicarbonates, halides, and nitrates of lithium. One or more of these may be used in an appropriate combination. . The manganese compound used in the present invention includes a manganese hydrate [Mn
OOH, Mn (OH) ₂ etc.], oxides, carbonates, bicarbonates, halides, nitrates and the like, and one or more of these may be used in an appropriate combination.

The mixing ratio of the lithium compound and the manganese compound is not particularly limited, but it is appropriate to mix them so that the ratio of the number of moles of lithium to the number of moles of manganese is 0.1 to 1.0, preferably about 0.5 to 1.0.

The adsorbent of the present invention, the above mixture under a predetermined oxygen partial pressure 35
It can be obtained by synthesis by heat treatment at a temperature of 0 ° C. or higher, preferably 400 ° C. or higher, or by eluting lithium from a lithium-containing manganese compound using an acid. At this time, the heat treatment temperature needs to be 350 ° C. or higher as described above. This is the one that has been heat-treated at a temperature below 350 ° C.
This is because the reaction between the lithium compound and the manganese compound does not sufficiently proceed, and the adsorption performance of the obtained adsorbent is significantly reduced. The heat treatment time is 5 minutes to 10 hours, preferably 30 minutes.
A suitable time is about minutes to 6 hours. The acid used to elute lithium from the lithium-containing manganese oxide includes:
Any acidic solution having a pH of 3 or less may be used, but a mineral acid of 0.1 N or more is preferred.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The following examples are not intended to limit the present invention, and any change in design based on the above and following points is included in the technical scope of the present invention.

[Examples] First, in order to understand how the amount of oxygen at the time of synthesizing a lithium-containing manganese oxide affects the amount of lithium adsorbed by an adsorbent, the present inventors conducted the measurement in a nitrogen atmosphere (oxygen content). Pressure: O) and in an air atmosphere (oxygen partial pressure: approx.
The lithium adsorption amount of each adsorbent synthesized in each of 21) was compared and examined.

As raw materials, lithium carbonate (Li ₂ CO ₃ ) and manganese carbonate (MnCO ₃ ) pulverized to a predetermined particle size, Li / Mn molar ratio
What was mixed with a V-type mixer so as to be 0.8 was used.
Then, 150 g of the above-mentioned raw materials were charged into a reaction vessel of an electric heating rotary furnace as shown in FIG. 1, heated to 400 ° C. in a nitrogen atmosphere, and rolled while sending nitrogen or air at a rate of 4 l / min. Heat treatment was performed below. In FIG. 1, 1 is a bearing, 2 is a rotation motor, 3 is a refractory brick, 4 is a reaction vessel, 5 is an electric furnace, 6 is a raw material, 7
Indicates thermocouples, respectively. The heating time was 1 to 4 hours in a nitrogen atmosphere and 1 to 6 hours in an air atmosphere. After the heat treatment, the reaction vessel 4 is cooled to room temperature in a nitrogen atmosphere,
Take out each sample in the reaction vessel 4 and add 0.2N-HCl (pH 0.7)
(Solid-liquid ratio: 10 g / l, treatment time: 90 minutes × 2 times), eluted lithium, and air-dried to obtain a lithium adsorbent. 1 g of each of the obtained lithium adsorbents was collected and immersed in 250 ml of simulated brine ([Li] = 130 ppm, pH 8), shaken for 24 hours, and the lithium concentration in the brine before and after the adsorption experiment was determined. The amount of adsorption was determined.

The relationship between the heat treatment time (synthesis time) of each adsorbent and the amount of lithium adsorbed is as shown in FIG. As is clear from FIG. 2, the lithium adsorbed amount of the adsorbent synthesized in the nitrogen atmosphere is extremely low at 2 mg / g or less in each case.
The amount of lithium adsorbed by the adsorbent synthesized in an air atmosphere increases as the time increases up to a synthesis time of 4 hours. Even if the treatment time is longer, the adsorption amount does not decrease, and the maximum is 28.5 mg / g. And very high values.

From these experimental results, it has been clarified that the amount of oxygen during the heat treatment plays an extremely important role in obtaining an adsorbent having excellent adsorption performance. It was also found that the amount of oxygen used for the raw material during the synthesis time (4 hours) when the lithium adsorption amount was saturated was 1.34 l / g.

The present inventors have attempted to synthesize lithium-containing manganese oxides under various oxygen partial pressures in order to understand in more detail the effect of oxygen partial pressure during the synthesis of lithium-containing manganese oxide based on the above experimental results. The effect of pressure on the amount of lithium adsorbed was studied.

Except for adjusting the oxygen partial pressure in the atmosphere by diluting pure oxygen with nitrogen, according to the method described above, lithium-containing manganese oxides are synthesized under various oxygen partial pressures, and these are acid-treated to form a lithium adsorbent. Then, the lithium adsorption amount of these adsorbents was determined by the same method as described above. The oxygen partial pressure was 0 to 1.0 when the synthesis time was 1 and 2 hours, and 0 to 0.3 when the synthesis time was 3 and 4 hours.

The relationship between the amount of lithium adsorbed by the obtained adsorbent and the oxygen partial pressure during the synthesis is as shown in FIG.

As is clear from FIG. 3, in the adsorbent obtained when the synthesis time is 1 hour or 2 hours, the oxygen partial pressure is reduced.
By setting the ratio to 0.25 to 0.3, the amount of adsorbed lithium is significantly increased. Further, under the above synthesis time conditions, even if the oxygen partial pressure was increased above 0.3, lithium adsorption hardly changed. On the other hand, in the adsorbent obtained when the synthesis time is 3 hours or 4 hours, even if the oxygen partial pressure is increased from 0.21 to 0.3, almost no increase in the amount of lithium adsorbed is recognized. From these, the oxygen partial pressure during synthesis is 0.20 or more,
It can be seen that a lithium agent having excellent adsorption performance can be obtained in a short time by preferably setting the range of 0.25 to 0.5.

FIG. 4 is a graph showing a comparison of the amount of lithium adsorbed by the adsorbent synthesized when the oxygen partial pressure was 0.21 (in air) and 0.3. As is clear from this result, the oxygen partial pressure was 0.3
The adsorbent synthesized by the method is hardly affected by the synthesis time, and the synthesis time is 4 hours even when the synthesis time is 2 hours.
The adsorption amount comparable to that of the time is obtained. This also indicates that the synthesis time can be significantly reduced by increasing the oxygen partial pressure to 0.3.

X-ray diffraction of the lithium-containing manganese oxide obtained under both conditions to clarify the reason why the amount of lithium adsorbed by increasing the oxygen partial pressure from 0.21 to 0.3 increased.
The results shown in FIGS. 5A and 5B were obtained.

According to FIG. 5, in the lithium-containing manganese oxide synthesized at an oxygen partial pressure of 0.3, MnCO ₃ and Li were recognized as unreacted substances in the lithium-containing manganese oxide synthesized at an oxygen partial pressure of 0.21. It was found that ₂ CO ₃ was reduced or completely disappeared. That is, by increasing the oxygen partial pressure, the contact reaction area between the raw material and oxygen increases, the reaction rate increases, and the reaction proceeds uniformly and sufficiently, thereby reducing unreacted substances. It is considered that the amount of lithium adsorbed by the obtained adsorbent is improved.

FIG. 6 is a graph showing the relationship between the total amount of supplied oxygen and the amount of lithium adsorbed by the adsorbent. As apparent from FIG. 6, the amount of lithium adsorbed increased with an increase in the total oxygen supply up to 1 × 10 ⁻³ Nm ³ / g. ^When it exceeds ^-3 Nm ³ / g, it is almost saturated. From this result, in order to obtain an adsorbent having excellent adsorption performance (adsorption amount: 20 mg / g or more), the total amount of oxygen supplied to the raw material should be 3 × 10 ^−3.
It can be seen that it is better to be at least Nm ³ / g, preferably at least 4 × 10 ⁻³ Nm ³ / g.

As shown in FIG. 7, the adsorbent obtained in the present invention hardly shows a decrease in the adsorbed amount due to the repeated operation of adsorption and desorption, and can withstand repeated use.

[Effects of the Invention] The present invention is configured as described above. In the process of synthesizing a lithium-containing manganese oxide, an oxygen-containing gas is forcibly supplied to appropriately control the oxygen partial pressure in the synthesis atmosphere, and the heating is performed. By performing the treatment, it has become possible to efficiently produce a lithium adsorbent excellent in adsorption performance with very little unreacted substance.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of the configuration of a rotary furnace used in the present invention, FIG. 2 is a graph showing the relationship between the synthesis time and the amount of lithium adsorbed by an adsorbent under each atmosphere, and FIG. FIG. 4 is a graph showing the relationship between the oxygen partial pressure and the amount of lithium adsorbed on the adsorbent, FIG. 4 is a graph comparing the amount of lithium adsorbed on the adsorbent synthesized when the oxygen partial pressure was 0.21 and 0.3, and FIG. X-ray diffraction diagrams of various lithium-containing manganese oxides, FIG. 6 is a graph showing the relationship between the amount of oxygen supplied to the raw material and the amount of lithium adsorbed by the adsorbent, and FIG. It is a graph which shows an influence. DESCRIPTION OF SYMBOLS 1 ... Bearing 2 ... Rotating motor 3 ... Refractory brick 4 ... Reaction vessel 5 ... Electric furnace 6 ... Raw material (mixture) 7 ... Thermocouple

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor ▲ Mio Sakakihara 2-3-3 Hananomiyacho, Takamatsu-shi, Kagawa Pref. Shikoku Industrial Technology Laboratory (72) Inventor Yoshifumi Kameoka Kobe, Hyogo Prefecture 7-3-3-334 Takamaru, Tarumizu-ku (72) Inventor Junji Kumamoto 2-10-E 6706 (72) Inventor Toshinobu Nishimura 2-70, Shinohara Akumanoyama-cho, Nada-ku, Kobe-city, Hyogo Prefecture 3-1 (72) Inventor Norio Matsumoto 1-29-3, Tomimatsu-cho, Amagasaki-shi, Hyogo (72) Inventor Genichiro Kamagaya 1845, Takasago-cho, Ninjincho, Takasago-shi, Hyogo Examiner Masahiro Inoue (56) References JP 61-283341 (JP, A) JP-A-62-83035 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 20/04 C01D 15/00

Claims (2)

(57) [Claims] A lithium compound and a manganese compound are crushed.
After mixing, while controlling the oxygen partial pressure to be 0.20 or more while forcibly supplying air or an oxygen-enriched gas to the mixture, the mixture is heated at a temperature of 350 ° C or more to oxidize lithium-containing manganese. A method for producing a lithium adsorbent, comprising synthesizing a product and eluting lithium from the oxide using an acid. 2. The method according to claim 1, wherein the total amount of supplied oxygen is at least 3 × 10 ⁻⁴ Nm ³ / g in terms of oxygen relative to the mixture.