JPH105585A - Lithium ion adsorbing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and selectively adsorbing a lithium ion even in a system in which a homologous ion with the lithium ion such as sodium ion coexists by preparing a lithium ion adsorbing agent from a composite material in which an interlaminar controlling material is deposited between the layers of a laminar phosphate expressed by a specified formula. SOLUTION: In the lithium adsorbing agent in the case when the lithium is recovered from an aq. soln. such as geothermal water containing lithium ion, the composite material in which the interlaminar controlling material is deposited between the layers of the laminar phosphate expressed by a general formula shown in a separate paragraph is used. In the formula, M is at least one kind of quadrivalent metal ion selected among Zr, Ti and Sn, A is the metal ion different from M or an ammonium ion, (n) is a number of >=0, (p) and (q) are the number satisfying the formula (p+mq=2), P is an integer, Q is 0 or the integer, (m) is a positive integer representing valency of A. A is preferably an alkali metal such as sodium or alkaline earth metal and an interlaminar distance of the phosphate is kept in the range of 9-40Å.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion adsorbent capable of selectively adsorbing lithium ions even in a system in which ions similar to lithium ions such as sodium ions coexist.

[0002]

2. Description of the Related Art In recent years, lithium metal and its compounds have been used in a wide range of fields, for example, ceramics, batteries, refrigerants, adsorbents, pharmaceuticals, and the like. The demand for lithium is expected to increase significantly.

At present, lithium metal and its compounds are mainly produced from lithium-containing minerals (lithium content: 2 to 6% by weight) such as spodumene, ambrigonite, petalite and lepidrite, and salt lakes and groundwater having a high lithium concentration. Although it is manufactured, most of the demand is currently covered by imports because of the lack of lithium resources mentioned above in Japan.

In order to meet the anticipated increase in demand for lithium, a method for obtaining lithium utilizing domestic resources is desired. On the other hand, geothermal water or hot spring water which contains lithium ions at a low concentration is relatively abundant in Japan, and thus a method for efficiently recovering lithium ions from these resources is considered promising.

As a method for recovering lithium from an aqueous solution, there are a precipitation method by concentration, a coprecipitation method, and an ion exchange method.

As a precipitation method, there is a method of evaporating seawater or salt lake water or the like by irradiating sunlight, removing salt and the like, and collecting a lithium salt. However, this method requires an enormous area and energy. However, it is not practical because of severe restrictions due to weather conditions and the like.

[0007] The coprecipitation method is a method of recovering lithium contained in seawater, hot spring water, groundwater and the like by coprecipitation with aluminum hydroxide. In this method, the amount and rate of adsorption of lithium are small. It has drawbacks and is not practical.

[0008] In order to recover lithium by the ion exchange method, it is necessary to use an adsorbent having excellent selective adsorption to lithium. That is, lithium in natural resources is generally present in an aqueous solution in which alkali metals and alkaline earth metals having similar chemical properties such as sodium coexist at a high concentration, and thus lithium is efficiently recovered from natural resources. To do so, it is necessary to selectively adsorb lithium. Ion exchange resins are widely used adsorbents, but their poor selectivity for lithium makes recovery of lithium difficult.

On the other hand, it is known that inorganic ion exchangers are generally superior in selectivity as compared with ion exchange resins. However, amorphous aluminum hydroxide, metallic aluminum, and phosphates represented by the following general formula [2] all have the property of adsorbing lithium, but have a problem of low selectivity to lithium. H _X A _1-X M ₂ (PO ₄ ) ₃ [2] (where X is a positive number less than 1 and A is Li, N
a is at least one selected from K and M is Z
It is at least one selected from r, Ti and Sn. )

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithium adsorbent having excellent selectivity for lithium.

[0011]

As a result of intensive studies, the present inventor has found that the above object can be attained by supporting an interlayer control substance between specific phosphate layers having a layered crystal structure. They have found and completed the present invention. That is, the present invention is a lithium ion adsorbent comprising a complex in which an interlayer controlling substance is supported between layers of a layered phosphate represented by the following general formula [1]. In _{H p A q M (PO 4} ) 2 · nH 2 O (1) (the above formula, M is Zr, at least one tetravalent metal ion selected from Ti and Sn, A is a metal different from M ions Or an ammonium ion, n is a number greater than or equal to 0, and p and q are both of the formula (p + mq =
2) is a number that satisfies 2), p is a positive number, and q is 0 or a positive number. Here, m is a positive integer representing the valence of A. )

Hereinafter, the adsorbent of the present invention and a method for using the same will be described. The adsorbent of the present invention is obtained by supporting an interlayer controlling substance on a specific layered phosphate. <Layered phosphate> The layered phosphate in the present invention is represented by the following general formula (1) (hereinafter simply referred to as layered phosphate). In _{H p A q M (PO 4} ) 2 · nH 2 O (1) (the above formula, M is Zr, at least one tetravalent metal ion selected from Ti and Sn, A is a metal different from M ions Or an ammonium ion, n is a number greater than or equal to 0, and p and q are both of the formula (p + mq =
2) is a number that satisfies 2), p is a positive number, and q is 0 or a positive number. Here, m is a positive integer representing the valence of A. )

The layered phosphate in the present invention is an anhydrous salt or a hydrated salt, and there are α-form (monohydrate), β-form (anhydrous salt) and γ-form (dihydrate) depending on the water content. The layered phosphate has a regular repeating structure of a (001) layer in its crystal structure, and the interlayer distance can be changed by supporting an interlayer control substance between the layers. . The preferred interlayer distance of the layered phosphate in the present invention is from 9 to 40 angstroms. If it is less than 9 angstroms, the ability to selectively adsorb lithium ions is insufficient, and if it is more than 40 angstroms, the complex becomes unstable. There is a risk of becoming.

A in the above general formula [1] is a metal ion or ammonium ion different from M, and is a component that can be supported on the adsorbent of the present invention as long as the effect of the present invention is not impaired. Preferred A includes alkali metals and alkaline earth metals such as sodium, potassium, magnesium and calcium. Preferred adsorbents of the present invention include the following. That is, H ₂ Zr (PO ₄ ) ₂・ H ₂ OH _1.995 Na _0.005 Zr (PO ₄ ) ₂・ H ₂ OH _1.500 Na _0.500 Zr (PO ₄ ) ₂・ H ₂ OH _1.980 Cu _0.010 Zr (PO ₄ ) ₂・ _{H 2 OH 1.560 Na 0.040 Cu 0.200} Zr (PO 4) 2 · 2H 2 OH 1.700 Cr 0.100 Zr (PO 4) 2 · H 2 OH 1.700 Bi 0.100 Zr (PO 4) 2 · H 2 OH 1.100 Na 0.300 Cr 0.200 Zr _{(PO 4) 2 · 3H 2} OH 1.100 Na 0.300 Bi 0.200 Zr (PO 4) compounds of Zr in ₂ · 3H ₂ O and the compound was replaced with Ti or Sn, as well as Cu ²⁺ in the above compounds, Zn ²⁺ , Mn ²⁺ ,
There are compounds substituted with Ni ²⁺ , Pb ²⁺ , Hg ²⁺ , Sn ²⁺ or Cd ²⁺ .

<Interlayer Control Substance> The interlayer control substance in the present invention is generally called a pillar and is a substance capable of controlling the interlayer distance of a layered compound to a desired size, and may be any substance as long as it can be supported on a layered phosphate. A compound having a functional group which can be easily ionized at both ends is desirable. Of these, compounds having an amine group such as butanediamine and hexanediamine are preferred, and amine compounds having 2 to 12 carbon atoms are particularly preferred. Even if an amine compound having less than 2 carbon atoms is supported, the lithium selectivity of the adsorbent is poor, and if the amine compound has more than 12 carbon atoms, it may be difficult to support the layered phosphate. Specific examples of preferred interlayer control substances include ethylenediamine, propanediamine,
There are aliphatic amine compounds such as butanediamine, hexanediamine and dodecanediamine.

<Synthesis Method of Layered Phosphate> The layered phosphate in the present invention can be easily obtained by a known method. For example, in the case of zirconium phosphate, it can be easily obtained as follows. . That is, zirconium oxychloride is added to a concentrated aqueous solution of phosphoric acid, and after heating and refluxing for 24 hours, the precipitate is filtered, washed with water, dried and pulverized to obtain zirconium phosphate (Zr (HPO ₄ ) ₂ .H ₂ O). obtain. In the layered phosphate of the present invention, as an A ion, an alkali metal, an alkaline earth metal, Cu ²⁺ , Zn ²⁺ , Sn ²⁺ , Mn ²⁺ , Ni ²⁺ , Pb ²⁺ , Hg ²⁺ ,
For those carrying ions such as Bi ²⁺ , Cd ²⁺ and Cr ^2+, the layered phosphate obtained as described above is immersed in an aqueous solution containing these metal ions to perform ion exchange. Ion exchange of some of the protons
Can be easily obtained.

<Synthesis Method of Composite> The method of supporting the interlayer controlling substance between layers includes (1) a method of coexisting an interlayer controlling substance during crystal synthesis, and (2) an ion exchange method after synthesizing a layered phosphate. A method for supporting an interlayer control substance between layers by using the method and
(3) There is a method of synthesizing a crystal using a reaction product (for example, phosphonate) of an interlayer control substance and phosphoric acid as a raw material. Industrially, the method (2) is the cheapest and advantageous.

The composite obtained as described above is generally in the form of a powder, and preferably has an average particle size of 0.01 to 100 μm, and more preferably has an average particle size of 0.1 to 10 μm. If the average particle size is less than 0.01 μm, the powders may cause agglomeration phenomenon, or when molding with a binder, the powdery particles will be covered with the binder and exhibit sufficient ion exchange properties. Conversely, if the average particle size is larger than 100 μm, when molding with a binder, the contact portion between the particles and the binder decreases and a molded body with high mechanical strength cannot be obtained. There is fear. The adsorbent of the present invention may be in the form of a powder, but when used in a column packing method or the like, the adsorbent is formed into an appropriate size and shape such as a granular shape, a rod shape, and a cylindrical shape in order to reduce flow resistance. It is preferable to have mechanical strength enough to withstand operations such as backwashing and regeneration.

<Molding method> The molding method may be a conventionally known method, and is roughly classified into a method using a binder and a method not using a binder.

1) Method Using a Binder A binder is classified into an organic binder and an inorganic binder. Preferred inorganic binders include clay minerals and metal alkoxides or hydrolysates thereof. -Clay minerals Clay minerals include, for example, bentonite, kaolin, diatomaceous earth, Kibushi clay, Frogme clay, etc. Any hydrated silicate-based swellable layered compound may be used. Among these, bentonite is particularly preferred because it is industrially easily available. Metal alkoxides or hydrolysates thereof Metal alkoxides are compounds in which the hydrogen of the hydroxyl group of alcohols is replaced with a metal, and specific examples thereof include Si (OR) ₄ , Ti
(OR) ₄ , Al ₂ (OR) ₃ and Zr (OR) ₄ (R is methyl, ethyl,
Alkoxides such as propyl and butyl). Of these, silicon alkoxides are preferred because they have a lower hydrolysis rate than alkoxides of other metals and can be easily formed into a stable sol. The metal alkoxide hydrolyzate can be prepared by an ordinary method, and becomes a sol or a gel according to the degree of progress of hydrolysis and polymerization of the metal alkoxide in a solvent. In order to facilitate kneading in the process, it is preferable to use a sol. O Molding process Various molded articles may be molded through a general molding process including mixing and kneading, granulation, and firing.

2) Method without using a binder A pressure molding method, a plastic molding method, a cast molding method, etc.
A compact having excellent mechanical strength can be easily obtained by forming the powdery adsorbent into an appropriate shape such as a granule, a bar, a pellet, and the like, and then calcining the compact.

<Usage Method> After contact with the lithium-containing liquid, the adsorbent is separated, and the separated adsorbent is contacted with the eluent, whereby the lithium adsorbed on the adsorbent can be recovered.

<Liquid-Containing Liquid> The target liquid from which lithium can be recovered by contact with the adsorbent of the present invention is not limited as long as it is a liquid containing lithium. There are natural water such as gas brackish water, geothermal water and hot spring water or salt-brine water, factory wastewater, and wastewater containing organic solvents. The temperature of these lithium-containing liquids may be any as long as the object to be ion-exchanged is liquid.In general, the higher the temperature of the lithium-containing liquid, the higher the lithium adsorption rate tends to be. The temperature of the lithium-containing liquid is preferably high.
Further, the pH value of the lithium-containing liquid is preferably 12 or less, but if the PH is 4 or less, the amount of lithium adsorbed tends to decrease.
5-11. The contact between the adsorbent of the present invention and the lithium-containing liquid can be performed by either a batch system or a continuous system, and the operation of separating the adsorbent after the contact from the lithium-containing liquid can be performed by a general solid-liquid separation means. I'll do it.

<Eluent> As an eluent for eluting lithium from the adsorbent that has adsorbed lithium as described above, there are inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid. May be used. Further, these inorganic acids and an aqueous solution of an ammonium salt may be used in combination. As the elution conditions, the higher the concentration of the eluent, the higher the temperature, and the longer the processing time, the higher the desorption rate of lithium tends to be. However, if there are operational restrictions, temperatures near room temperature are sufficient. Hereinafter, specific examples will be described.

Synthesis Example 1 Zirconium oxychloride was added to a concentrated aqueous phosphoric acid solution, and the mixture was heated under reflux for 24 hours, and the precipitate was filtered, washed with water, dried, and dried.
By pulverization, zirconium phosphate [Zr (HPO ₄ ) ₂ .H ₂ O] was obtained.

[0026] Instead of Synthesis Example 2 zirconium oxychloride, titanium tetrachloride using a chloride, titanium phosphate in the same manner as in Synthesis Example 1 _{[Ti (HPO 4) 2 · H} 2
O].

Synthesis Example 3 Instead of zirconium oxychloride, tin chloride was used.
Tin phosphate [Sn (HPO ₄ ) ₂ .H ₂ O] was obtained in the same manner as in Synthesis Example 1.

[0028]

Examples 1 to 8 Layered zirconium phosphate [α-zirconium phosphate: H ₂ Zr (PO ₄ ) ₂ .H ₂ O] obtained in the above synthesis example
Or layered titanium phosphate [α-titanium phosphate: H ₂ Ti (PO ₄ ) ₂
[H ₂ O] 10 g is dispersed in ion-exchanged water 100 ml,
10 mmol of a predetermined interlayer control substance shown in Table 1 below was added, and the mixture was uniformly stirred and then suspended in a constant temperature shaking tank at 40 ° C. for 24 hours. Thereafter, the slurry is subjected to solid-liquid separation and the solid content is washed. For cleaning, the electric conductivity of the cleaning liquid is 100 μS.
/ Until it becomes below. The solid content after the washing was dried at 80 ° C. to obtain a composite having a layered control substance supported between layers.

[0029]

[Table 1]

[0030]

COMPARATIVE EXAMPLE 10 g of layered α-zirconium phosphate or layered α-titanium phosphate was dispersed in ion-exchanged water, and an interlayer controlling substance was carried in the same manner as in the example except that no interlayer controlling substance was added. No layered phosphate was obtained (Table 1).

[Evaluation] <Bottom spacing of product> The above Examples 1 to 6 and Comparative Example 1,
With respect to the sample synthesized in 2, the distance between the bottom surfaces of the crystals (synonymous with the interplanar distance of the (001) plane) was measured using the powder X-ray diffraction method. The measurement conditions of the powder X-ray diffraction are as shown in Table 2 below, and the distance between the bottom surfaces is shown in Table 3 below.

[0032]

[Table 2]

[0033]

[Table 3]

Note: The distance between the bottom surfaces in Table 3 is the d value according to Bragg's equation, and the unit is angstrom.

<Ion Exchange Test> The samples synthesized in Examples 1 to 6 and Comparative Examples 1 and 2 were subjected to an ion exchange test using a mixed solution of sodium ion and lithium ion under the test conditions shown in Table 4 to obtain a sample. Table 5 below shows the ion exchange capacity per unit gram.

[0036]

[Table 4]

[0037]

[Table 5]

Note) Ion exchange capacity unit: meq / g IEC (Li): Lithium ion exchange capacity IEC (Na): Sodium ion exchange capacity

<Lithium ion selectivity> Lithium ion exchange capacity / sodium ion exchange capacity [IE (Li) / IE (N
a)] is shown in Table 5 above. As can be seen from these results, the conventional zirconium phosphate or titanium phosphate having nothing carried between the layers exchanges sodium ions more preferentially than lithium ions (Comparative Examples 1 and 2). .
On the other hand, the composite of the present invention in which the layer spacing is widened by the layer control material has the property of more selectively ion-exchanging lithium ions than sodium ions (Examples 1 to 8). In particular, the composites in which the layer control substance was supported between the layers of titanium phosphate (Examples 5 to 8) had an increased lithium ion exchange capacity as compared with Comparative Example 2, whereas the composites having sodium ion The exchange capacity has dropped sharply, resulting in IE (Li) / IE
It can be seen that the value of (Na) is remarkably large, and the selectivity for lithium is extremely large.

[0040]

Since the adsorbent of the present invention has a characteristic of selectively adsorbing lithium, it can remove lithium from natural water such as geothermal water, hot spring water, natural gas brackish water, salt-produced brackish water and seawater or various factory waste liquids. Lithium can be easily recovered by very efficiently adsorbing and then eluting with an inorganic acid. Therefore, the present invention is extremely useful in the liquid treatment industry for natural water such as seawater and groundwater or various wastewater containing lithium.

Claims (2)

[Claims] 1. A lithium ion adsorbent comprising a composite in which an interlayer controlling substance is supported between layers of a layered phosphate represented by the following general formula [1]. In _{H p A q M (PO 4} ) 2 · nH 2 O (1) (the above formula, M is Zr, at least one tetravalent metal ion selected from Ti and Sn, A is a metal different from M ions Or an ammonium ion, n is a number greater than or equal to 0, and p and q are both of the formula (p + mq =
2) is a number that satisfies 2), p is a positive number, and q is 0 or a positive number. Here, m is a positive integer representing the valence of A. ) 2. The lithium ion adsorbent according to claim 1, wherein the distance between the (001) planes of the layered phosphate carrying the interlayer controlling substance is 9 to 40 angstroms.