JP3095461B2 - Acid recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new method for efficiently and selectively recovering or removing an acid from an acid-containing solution by diffusion dialysis using a cation exchange membrane. Form metal complex anions like ions
The present invention relates to a method for separating and recovering an acid from an acid solution containing formed impurities .

[0002]

Use BACKGROUND ART anion exchange membrane, acid and metal ions
So-called diffusion dialysis, in which an acid is recovered from a solution containing ON and a metal ion is separated by using a difference in concentration as a driving force, and so-called diffusion dialysis is already used in many fields. Numerous documents and patents have been reported for such acid diffusion dialysis membranes.
The most practical and as beneficial, chloromethylstyrene (or vinyl pyridine) - amination of divinylbenzene copolymer (or quaternary pyridinium reduction) is an anion exchange membrane made of material. However, recovery of an acid from a hydrochloric acid solution or the like containing impurities such as trivalent iron ions using these anion exchange membranes has a drawback in that the acid permeability and the selective separation are significantly reduced.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks and provides a method for diffusion dialysis capable of recovering an acid from an acid solution containing impurities forming metal complex anions , such as iron ions in hydrochloric acid. Further, the present invention provides a method for separating and recovering acid by diffusion dialysis, which is useful for environmental protection and resource saving by applying to a manufacturing process solution or waste liquid treatment which was conventionally considered to have no recovery merit. The purpose is to:

[0004]

According to the present invention, a mixture of an acid having a formula weight of 100 or less and an impurity is provided on one surface of an ion exchange membrane.
By bringing the mixed solution into contact and bringing the other surface into contact with water or a dilute solution of the acid, the acid in the mixed solution is
Separation and recovery by permeating the other surface of the ion exchange membrane
Method, wherein the ion exchange membrane has 1 g of sulfonic acid groups.
Containing 0.5 to 4.5 mg equivalent per dry resin, and
When measured in a solution of the above acid at a concentration of 0.5 M, the electric resistance is 0 . This is a method for separating and recovering an acid which is a cation exchange membrane of 5 Ω · cm ² or less.

The method for separating and recovering an acid of the present invention is completely different from the conventional method for separating an acid by diffusion dialysis using an anion exchange membrane, and is characterized by using a cation exchange membrane .

The present invention will be described in more detail below. The cation exchange membrane used in the present invention has 1 g of sulfonic acid groups.
0.5 to 4.5 mg equivalent, preferably 0.8 to 3 mg equivalent per dry resin, and the concentration of acid to be recovered is 0.5
The electrical resistance measured in a solution of M is 0.5Ω · c
m ² or less, preferably 0.2 Ω · cm ² or less is used.

[0007] The electric resistance of the ion exchange membrane in the present invention is represented by an AC resistance measured in an aqueous solution having a concentration of 0.5 M of the acid to be recovered. In a cation exchange membrane having an electric resistance higher than 0.5 Ω · cm ² , the permeation rate of the acid is low, and even if the selectivity is high, it is not practical to recover the acid. on the other hand,
If the electric resistance is too small, the selectivity of the acid will be small. Therefore, it is appropriate that the electric resistance is preferably 0.001 Ω · cm ² or more.

The cation exchange membrane used in the present invention is, for example, a cast polymerization membrane, a graft polymerization membrane, a plasma polymerization membrane using a polymer such as styrene, perfluorocarbon, or engineering plastic such as polysulfone. A film, a melt-molded film, a cast film, or the like can be used.

As a specific example of such a cation exchange membrane, CF ₂ ＣＦCFO (CF ₂ CF ( CF ₃ ) O) _n (C
F ₂ ) _m SO ₂ F (n is 0 to 2 and m is 0 in the chemical formula)
4, but n and m do not take 0 at the same time. ) And made of a copolymer of tetrafluoroethylene, a cation exchange membrane which has been converted SO ₂ F groups to SO ₃ H groups, film thickness is 0.1 to 200 [mu] m, preferably 1~100μm Sun
An ion-exchange membrane is used because of its excellent acid permselectivity , easy handling, and easy availability of the membrane.

Another preferred cation exchange membrane for use in the present invention is a polymer substantially composed of an aromatic ring and a linking group, wherein a repeating unit represented by the general formula -X
-Ar-Y- (where X and Y represent the same or different electron-donating linking groups, preferably -O- or -S-, and Ar represents an aromatic ring). A cation exchange membrane comprising an aromatic polymer having a sulfonic acid group introduced into its aromatic ring is used. Such cation exchange membranes is superior to the main chain mechanical properties since it has an aromatic ring, heat resistance, and chemical resistance.

As such a cation exchange membrane, for example,
A sulfonic acid group is added to a polymer containing a repeating unit such as Chemical formula 1 in an amount of 0.5 to 4.0 mg equivalent / g dry resin, preferably 1.
A cation exchange membrane into which 0 to 2.0 mg equivalent / g dry resin is introduced is exemplified.

[0012]

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Above all, when an aromatic polymer is a block copolymer composed of two kinds of repeating units, and a cation exchange membrane having a sulfonic acid group introduced into the aromatic ring is used, the permeability, This is preferable in that a film having high selectivity and excellent mechanical properties is obtained.

Examples of such a block copolymer include polyphenylene oxide / polyether sulfone copolymer, polyphenylene sulfide / polyether sulfone copolymer, polyaryl ether sulfone / polyether sulfone copolymer, polyaryl ether arylate / polyarylate. Copolymers or polyarylethersulfone / polythioethersulfone copolymers are exemplified.
Of these, preferred block copolymers include those represented by the following chemical formula 2.

[0015]

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In the formula 2, m and n are 2 to 200, m / n
Is 0.1 to 100. Such copolymers are disclosed in Japanese Patent Application Laid-Open Nos. 1-215348 and 2-24503 by the present applicant.
5 and JP-A-2-248434.

The cation exchange membrane used in the present invention can be reinforced with a porous substrate in order to impart practical strength for ensuring dimensional stability, handling properties, and the like. Such a porous substrate can be embedded in an ion exchanger layer and used as a reinforced cation exchange membrane, and for the purpose of increasing acid permeability, a thin film layer of an ion exchanger and a porous substrate layer can be used. Of the present invention can be a multilayer anion exchange membrane.

The shape of the membrane is not limited to a general flat shape, but may be a bag shape, a hollow fiber, a hollow tube, or the like. As such a cation exchange membrane, a cation exchange membrane having a thickness of 0.01 to 100 μm, preferably 0.5 to 50 μm is used.

[0019] As the acid to be separated and recovered by diffusion dialysis using the above cation exchange membrane, wherein the amount of acid radical is 100 or less acid. As an acid having a formula weight of 100 or less,
HBr, HCl, HClO ₃ , HF, HI, HNO ₃ ,
Examples thereof include inorganic acids such as H ₂ SO ₄ and H ₃ PO ₄ and organic acids such as formic acid and acetic acid. Among them, HCl, HF, HNO ₃ , H ₂ SO ₄ and H ₂
One or more mixed acid selected <br/> from the group selected from the group consisting of ₃ PO ₄ is used.

The impurities in the mixed solution in the present invention include cations and / or anions other than hydrogen ions. Examples of the cation include group 2A of the periodic table (M
g, Ca, etc.), 2B group (Zn, Cd, etc.), 3A group
(Y, La etc.), 3B group (Al, Ga etc.), Group 8 (Fe, Co, Ni, platinum group metals etc.) metal ions
Is exemplified. Typical examples are iron, nickel,
Zinc and aluminum ions are exemplified. Specific acid solutions containing these impurity cations include a sulfuric acid pickling solution of iron, an acid plating solution of nickel or zinc, and a hydrochloric acid etching solution of aluminum.

On the other hand, examples of the anion which is an impurity in the mixed solution include anions having a formula weight of 150 or more, and include a group 1B (such as Cu), a group 2B (such as Zn and Cd), and a group 3A of the periodic table. (U etc.), 3B group (Al, Ga etc.) ,
4A group (Ti, Zr, etc.), 4B group (Ge, Sn, Pb
Etc.), 5A Group (V, Nb, etc.), 6 A group (Cr, M
o, W, etc.), Group 6B (Se, etc.) , Group 7A (Mn, etc.) or Group 8 (Fe, Co, Ni, platinum group metals, etc.)
Examples thereof include an oxygen oxy group of a metal, an acid group of a polyacid (isopoly acid, heteropoly acid) of the metal, and a metal complex anion of the metal . In addition, organic anions which are acid radicals such as organic sulfonic acids having 5 or more carbon atoms and organic carboxylic acids having 8 or more carbon atoms are shown.

Typical examples of these are acid radicals such as vanadate, niobate, molybdate, tungstate, uranate, selenate, telluric acid, and the like.
Acid root of their isopolyacids and heteropoly acid.
You. In addition, chloroplatinic acid, chloropalladium acid, [C
o (NH ₃ ) ₂ (NO ₂ ) ₄ ] ⁻¹ , [Fe (CN) ₆ ]
^-4 , [Ni (CN) ₄ ] ^-2 , FeCl ₆ ^-3 and the like, and organic anions such as alkylbenzenesulfonic acid radicals.

Thus , according to the present invention , on one surface of the cation exchange membrane , the formula weight of the acid radical containing impurities is 100 or less.
Solution of the acid into contact with, by brought into contact with water or a dilute solution of the acid on the other side, by a method known spreading dialysis, the cation or anion as impurities of acid solution, the cation exchange The above acids without passing through the membrane
Acids having a formula weight of the root of 100 or less selectively permeate the membrane, and such acids can be selectively separated and recovered.

[0024]

[Action] It is not always clear why the acid can be recovered by the cation exchange membrane, but it is considered to be due to the following action. A cation exchange membrane having a sulfonic acid group has a function of preventing permeation of anions since the sulfonic acid group can be dissociated in an acid solution . And the transmission of that anion
Is considered to depend on the mass of the anion. Cation exchange membranes with low electric resistance in acid solution have excellent proton permeability, so that not only protons can permeate, but also small mass anions can be permeated to maintain electrical balance, but large mass anions. Can not be permeated through a cation exchange membrane, and as a result, an acid containing a small anion as a component is selectively permeated and separated. However, this description is given for the understanding of the present invention, and the present invention is not limited by this description.

[0025]

Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 4,4'-diphenol and dichlorodiphenylsulfone were reacted in the same manner as in the synthesis method described in JP-A-61-168629, and the intrinsic viscosity of an aromatic polysulfone unit was reduced to 0. the .22 precursor of synthesizing, then reacted with the sodium sulfide with said precursor and dichloro diphenyl sulfone, an aromatic polysulfone and polythioether sulfone equimolar to obtain a block copolymer a of the intrinsic viscosity of 0.65.

Next, the copolymer A was reacted with a sulfuric anhydride / triethyl phosphate complex to obtain a sulfonated copolymer B. From NMR measurement of the copolymer B, selectively sulfonic acid group to the aromatic ring of the diphenol it was introduced.
The copolymer B thus obtained was dissolved in N-methylpyrrolidone, and then the solution was cast and dried by heating at 50 ° C. for 2 hours to prepare a cation exchange membrane comprising a cast membrane C having a thickness of 30 μm. did. The ion exchange capacity of the cation exchange membrane was 1.9 mg equivalent / g dry resin, and the electric resistance in 0.5 M hydrochloric acid was 0.05 Ω · cm ² .

[0028] 2 by cation exchange membrane obtained by nuclear
One chamber of the dialysis cell divided into 7 chambers contains 7N hydrochloric acid and 0.1 ml of 0.1N.
A mixed solution containing 5M ferric chloride was filled, the other chamber was filled with pure water, and the permeation rate of acid and iron permeating into the pure water side was determined. In this mixed solution, iron is a metal complex.
It is an anion state.

The permeation rate of the acid is 4.9 mol / m ² · hr
-It was Δc . It is a measure of selectivity (permeation rate of iron /
The acid transmission rate) ratio was 0.002. It can be seen that the permeability and selectivity are superior to the anion exchange membrane of Comparative Example 1 . Note that Δc is a difference in molar concentration.

Comparative Example 1 The copolymer A of Example 1 was chlormethylated and then reacted with trimethylamine to obtain an ion exchange capacity.
There was obtained an anion-exchange membrane D of 2.0mg equivalent / g dry resin der RumakuAtsu 25 [mu] m. The electrical resistance in the hydrochloric acid concentration of 0.5M in the D film was 0.25 ohms · cm ^2.

In the same manner as in Example 1, 7N hydrochloric acid and 0.5
When the performance of diffusion dialysis with a mixed solution containing M ferric chloride was determined, the acid permeation rate was 0.14 mol / m ² ···
hr · Δc , and the ratio of (permeation speed of iron / permeation speed of acid) was 0.26.

[0032]

According to the conventional diffusion dialysis of an acid using an anion exchange membrane, when recovering hydrochloric acid from hydrochloric acid containing ferric chloride, the permeability of the acid and the selectivity of the acid decrease. Although it was practically impossible to recover the acid, diffusion dialysis using the cation exchange membrane of the present invention can provide a practical acid separation and recovery process, thereby preserving the environment and effectively using resources. .

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 61/24

Claims (4)

(57) [Claims] 1. The method according to claim 1 , wherein the acid radical has a formula weight of 10 on one side of the ion exchange membrane.
0 contacting the mixed solution of the following acids and impurities, by contacting water or a dilute solution of the acid on the surface of the other side,
The acid in the mixed solution is transferred to the other surface of the ion exchange membrane.
A method for separating and recovering by permeation, wherein the ion exchange membrane has a sulfonic acid group content of 0.5 to 0.5 g per 1 g of dry resin.
4.5mg equivalents contained, and the electrical resistance is zero when measured in solvent <br/> solution of the acid concentration 0.5 M. 5Ω · cm ² or less
A method for separating and recovering an acid as a cation exchange membrane. An acid having a formula weight of 100 or less is HCl,
HF, consisting HNO _3, H ₂ SO ₄ and H ₃ PO ₄
One or a method of separating and recovering two or more acids according to claim 1, wherein the mixed acid selected from the group selected from the group. 3. The method according to claim 1, wherein the impurity is a cation and the periodic table
Group consisting of 2A, 2B, 3A, 3B and 8
More least one of claims 1 or 2 separation process for recovering acids wherein the cation of a metal selected. 4. The impurity is an anion having a formula weight of 150 or more , and is composed of groups 1B, 2B, 3A, 3B, or 3B of the periodic table .
Groups 4A, 4B, 5A, 6A, 6B, 7A and
Of at least one metal selected from the group consisting of
Oxyacid or polyacid acid radicals, or selected from this group
At least one of claims 1 or 2 separation process for recovering acid wherein the metal complex anion of a metal.