JPH01168652A - Method for purifying aqueous solution of complexing agent - Google Patents

Abstract

PURPOSE:To readily, economically and efficiently obtain the title aqueous solution useful for waste liquor treatment containing metals, etc., by feeding an aqueous solution containing a complexing agent of amino-polyacetic acids and impurities to a column filled with a strong acid cation exchanger under specific conditions, adsorbing the complexing agent thereon, etc. CONSTITUTION:An aqueous solution containing a complexing agent of amino- polyacetic acids (e.g., N-hydroxyethylenediaminetriacetic acid hereinafter abbreviated to HEDTA) and impurities [yttrium (Y) ion as a cationic impurity and chloride ion as an anionic impurity] is fed to a column filled with a strong acidic cation exchanger until the concentration of the complexing agent in the resultant effluent attains 5-80% based on that of the feed solution and the adsorbed complexing agent is then desorbed to carry out purification.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applications] The present invention relates to a method for purifying an aqueous solution of an aminopolyacetate complex-forming agent (hereinafter simply referred to as "complex-forming agent") containing impurities.

Complex-forming agents are widely used in processes for treating waste liquids containing metals, separation and purification of metal ions using ion exchange methods, and the like. however,#! J-forming agents are generally expensive;
When used on an industrial scale, recovery and reuse are essential.

In particular, in the fractional purification of rare earth elements using a cation exchanger and an aqueous solution of a complexing agent, the purity of the aqueous solution of the complexing agent recovered and reused differs from the purity of each rare earth element obtained by separation. It resonates loudly. Therefore, purification of the complexing agent aqueous solution is important.

[Prior art and problems to be solved by the invention] Conventionally, crystallization purification has not been mainly used to purify an aqueous solution of a complexing agent. That is, an alkali is added to an aqueous solution of a complex forming agent forming a complex with heavy metal ions, and the heavy metal ions are precipitated and separated as hydroxides.

Next, acid is added and/or cooled to generate a complex-forming agent precipitate, which is then filtered, washed with water, and purified and recovered. However, in this method, the slight difference in solubility depending on the PH1 temperature of the complex forming agent is used for crystallization, purification and recovery, so #! I
Recovery rate of forming agent is low. Also, within the shell, the complexing agent is used as a dilute solution, and when processing such a solution, the aqueous complexing agent solution must be concentrated before processing. Because of this, it is inefficient to carry out on an industrial scale, and is economically and technically disadvantageous.

In addition, an anion exchange resin is used to purify the complexing agent aqueous solution,
There is a method of purification by adsorbing a complex forming agent. In this method, complexing agents can be adsorbed and cationic impurities can be removed. However, C1-1NOs-1F-1
Anionic impurities such as 804''-1SiQ1''- are adsorbed together with the complexing agent and cannot be removed. Furthermore,
Anion exchange resins have low heat resistance and large swelling and contraction, so their chemical and physical stability is poor and their use is discouraged.

The present invention has been made to solve the above-mentioned problems of the prior art, and provides a method for simply, economically and efficiently purifying and recovering a complex-forming agent from an aqueous solution of a complex-forming agent containing impurities. The purpose is to

[Means for solving problems]

The present inventors have conducted extensive studies in order to find a method for purifying and recovering a complexing agent more simply, economically, and efficiently from an aqueous complexing agent solution containing impurities.

As a result, when an aqueous solution of a complex-forming agent containing impurities is supplied and brought into contact with a limited cation exchanger, the complex-forming agent is adsorbed by the cation exchanger, and anionic impurities and nonionic impurities are Historically, cationic impurities, especially polyvalent cationic impurities, are not adsorbed by ion exchangers and can be removed, and cationic impurities, especially polyvalent cationic impurities, are adsorbed or have a difference in adsorption power with the complex forming agent.

They discovered that the adsorbed complex-forming agent can also be recovered as a concentrated aqueous solution of the complex-forming agent, and finally completed the present invention.

That is, in the present invention, an aqueous solution of an aminopolyacetic acid complex-forming agent containing impurities is passed through a column filled with a strongly acidic cation exchanger such that the concentration of the complex-forming agent in the solution flowing out is 5 to 80% that of the feed solution.
%, and then the adsorbed complex forming agent is desorbed.

The principle of the present invention is that a complex forming agent aqueous solution containing N-hydroxyethylethylenediamine 3 & 1 (HBDTA) as a complex forming agent, yttrium (Y) as a 1m ion impurity, and chloride ions as an ion and anion impurity,
An example will be explained in which a liquid is passed through a column packed with a proton-type strongly acidic cation exchanger.

That is, when an HF1DTA aqueous solution containing Y ions and chloride ions is passed through a column packed with a proton-type strongly acidic cation exchanger, the chloride ions flow out of the column without being adsorbed by the ion exchanger, while HEDTA and Y ions are adsorbed on the ion exchanger. A very interesting fact was discovered that when the liquid flow was continued further, HEDTA broke through, a concentrated effluent of HEDTA was obtained, and then Y ions broke through. Furthermore, the REDTA of the effluent
Purge the initial effluent until the concentration is 5-80% of the feed solution (EDTA 6°C) to remove the adsorbed HED.
HED purified by desorbing and recovering TA
It was possible to obtain a TA aqueous solution.

The present invention will be explained in more detail below.

The complexing agents used in the present invention include ethylenediaminetetraacetic acid (EDTA), N-hydroxyethylethylenediaminetriacetic acid (HEDTA), and 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (DCTA). ,
Diethylenetriamine-N, N, N', NIP, Nl/
-pentaacetic acid (DTPA), ethylene glycol-bis(2
-aminoethyl)ether-N%N%N', N'-tetraacetic acid (DB), bis(2-aminoethyl)ether-N,
These are polyaminoacetic acids such as N, N', N'-tetraacetic acid (ME), nitrilotriacetic acid (NTA), and iminoniacetic acid (IMPA). There are no particular restrictions on the concentration of the complexing agent, but
It is usually 0.001 to 0.2 m01/l.

Impurities are soluble impurities other than dissolving and complexing agents, and are divided into anionic impurities, cationic impurities, and nonionic impurities. Anionic impurities such as 0l-1N03-1F25O42-1Si03'-, etc., and cationic impurities such as -valent ions and multivalent ions, and the present invention particularly targets multivalent ions.

Specific examples include Ca 2 +, Mg”, Cu 2+, z
Examples include n2+, A13+, rare earth element ions, and the like. Examples of nonionic impurities include alcohols, ketones, and various carbohydrates.

These impurity concentrations are not particularly limited.

The ion exchanger used is a harsh cation exchanger and has a sulfonic acid group.

There are no restrictions on its form or parent body.

Specifically, Amberlight IR-120B, Amberlight IR-252, Annoku-Light CG-120 (
The above are manufactured by Organo■), Diaion 5KIB, Diaion RMK-808, Diaion PK216 (the above are manufactured by Mitsubishi Chemical Industries (t@)), DOWEX 50W1 DOWEX 88 (all manufactured by Dow Chemical Company), Toshikuseki Examples include ion exchange fibers, etc. However, in the case of a weakly acidic ion exchanger in which the exchange group is a weak acid group, the adsorption amount of the complex forming agent is too small, and therefore it is not suitable for the present invention.

Further, a mixed type of a sulfonic acid group and a weak acid group such as a carboxylic acid group, a phenol group, or a phosphoric acid group may be used.

Specifically, JP-A-53-4787, JP-A-58
Examples include ion exchange fibers that are a mixture of sulfonic acid groups and carboxylic acid groups and are disclosed in Japanese Patent Publication No. -45541. In the mixed type, the ratio of exchange capacity of sulfonic acid groups to weak acid groups is preferably 11.0 or more, and the adsorption amount of the complex forming agent can be increased.

A weakly acidic cation exchanger in which the exchange group is a weak acid group has too little ability to adsorb a complexing agent and cannot achieve the object of the present invention.

The counter ion of the exchange group is preferably a proton (H+). When the counterion is of the type ■, the amount of adsorption of the complex forming agent on the strongly acidic cation exchanger increases.

The ratio of H+ to all counterions (g ions) is preferably 30% or more, more preferably 50% or more.

Other counter ions are preferably monovalent cations such as sodium ion (Na"), potassium ion (K"), ammonium ion (NH:), and the like.

The pH of the aqueous complex forming agent solution containing impurities is preferably 5 or less, particularly preferably 0 to 4. If the pH is too low, not only will the amount of acid used increase, but the complexing agent may precipitate on the ion exchanger. If the pH is too high, the amount of adsorption of the complex forming agent decreases. Furthermore, if heavy metal ions are included as cationic impurities, hydroxides of the heavy metals will be produced, making operation difficult.

There is no problem with the contact temperature between the aqueous solution of the complexing agent containing impurities and the strongly acidic cation exchanger as long as the solubility is higher than the concentration of the complexing agent, but in order to increase the adsorption amount of the complexing agent, the lower the better. . The preferred temperature is 30-100°C, particularly preferably 40-80°C. If the temperature is too high, the adsorption amount of the complex forming agent decreases and a large amount of thermal energy is required. On the other hand, if the temperature is too low, a large amount of cooling energy is required, and in some cases, the complex forming agent may precipitate.

When an aqueous solution of a complexing agent containing impurities is brought into contact with a strongly acidic cation exchanger, the complexing agent is adsorbed.

On the other hand, most of the anions and nonionic impurities remain in the aqueous solution without being adsorbed. Cation impurities vary depending on their type, pH, temperature, etc., but polyvalent cation impurities are easily adsorbed, and -valent cation impurities are difficult to adsorb.

Therefore, by purging the effluent, impurities other than the complexing agent and polycationic impurities, particularly monoionic impurities and nonionic impurities, can be separated. 4 yen tons of impurities
! As the supply of the complex forming agent continues, the adsorption of the complex forming agent reaches saturation and some of the complex forming agent flows out into the aqueous solution.

The complexing agent concentration in the effluent is 5% of the complexing agent concentration in the feed solution.
When the amount reaches ~80%, the supply is finished and the liquid that has flowed out up to that point is purged. This allows most of the impurities to be separated and removed from the complex forming agent.

If the contact is terminated when the concentration of the complexing agent in the effluent is lower than 5% of the concentration of the feed solution, the contact is stopped with the complexing agent adsorption capacity of the naori ram remaining, and the capacity of the complexing agent is reduced per cycle and column capacity. This will reduce the processing capacity of each unit. On the other hand, if the supply is finished at a point higher than 80%, the adsorption amount of the complex-forming agent can be increased, but a large amount of the complex-forming agent will be purged as a processing liquid, which will lower the yield.

A more preferable range is 10 to 50%.

After adsorption of the complexing agent, it is desorbed. The temperature at that time was 30-1
20°C is preferred, particularly 50-95°C. Furthermore, the temperature is preferably 10° C. or more higher than the treatment temperature for adsorption. If the temperature is too low, it will take a long time to desorb the complexing agent, and the amount of water required will increase. Also, as a result, attachment and detachment
The concentration of the recovered complexing agent becomes lower. If the humidity is too high, a large amount of thermal energy is required, and the strongly acidic cation exchanger deteriorates rapidly.

The pH of the liquid used to desorb the complexing agent is preferably increased by adding an alkali such as ammonia to the extent that heavy metals are not separated and precipitated from the column.

This is because within the above range, the higher the pH, the easier the complex forming agent is to be desorbed, and the more difficult it is for polyvalent cation impurities to be desorbed.

This pH varies depending on the type of liquid for desorption, as explained below. It is recognized that this is due to the fact that the effect of the ion exchange resin is different, and the degree of pH reduction in the column is different.

In order to obtain a complexing agent aqueous solution with particularly high purity, water may be used as the desorption liquid. Although pure water may be used, a small amount of alkali such as ammonia may be added to facilitate desorption, ie, concentration, of the complex forming agent. In this way, p
Even if H is set to about 8, heavy metals do not precipitate in the column because the pH is below 5. When the amount of water used is large, the desorption rate of the complexing agent increases, but the concentration of the complexing agent recovered, drained, and rinsed becomes low. Furthermore, if the amount of water used is small, the concentration of the complexing agent recovered and purified can be increased, but the desorption rate will be reduced. Regardless of the water spray used and the concentration of the complexing agent in the impurity-containing raw material liquid previously supplied during adsorption, the concentration of the complexing agent in the recovered liquid is 0.01 to 0, s mol/
It is preferable to set the amount to t. That is, when the concentration of the complexing agent in the raw material liquid is low, it is recovered as a highly concentrated purified liquid. Since the liquid flowing out at the beginning of desorption contains impurities that remained in the liquid in the column at the end of the adsorption step, it may be fractionated and mixed with the raw material liquid for reprocessing.

If a small amount of impurity is allowed to be mixed into the complexing agent aqueous solution obtained, the impurity-containing raw material liquid itself can be used as the desorption liquid. Although this liquid may be used as it is, concentration becomes easier if the pH is increased by 1 or more compared to that during adsorption using an alkali such as ammonia. If this liquid is continued to be supplied, the complexing agent concentration in the effluent increases. If the pH of the feed solution or the process temperature is higher than in the adsorption step, the effluent will have a higher concentration of m-former than the feed solution, the concentration will pass through a maximum value and begin to decrease until it reaches the same level as the feed solution. The concentration will be the same. Such conditions may be used when the purpose is to obtain an aqueous complex-forming agent solution having a higher concentration than that of the raw material solution. The concentration ratio can be increased to 1.2 times or more, and in some cases to 2 times or more.

If the purpose is only to remove polyvalent cations, a large amount of the desorption liquid can be flowed through the process, and the pH and treatment temperature of the liquid can be the same as the supply liquid in the deposition process. It is sufficient to continue flowing until the point at which polyvalent cations break through.

Since the polyvalent cations remaining adsorbed on the column interfere with the adsorption of the complex forming agent in the adsorption step, after the above desorption treatment, the polyvalent cations are removed by desorption using hydrochloric acid, nitric acid, sulfuric acid, or the like. This treatment turns the counterion of the strongly acidic cation exchanger into H+, so the column can be used as is for the above adsorption treatment.

〔Effect of the invention] Next, the effects of the present invention will be listed.

(2) According to the present invention, an aqueous complex-forming agent solution containing additives can be purified with simple operations and simple equipment.

■ A complex forming agent aqueous solution containing impurities can be purified and concentrated at the same time.

■ RN can be produced with almost no loss of expensive complexing agents.

■ Conventionally, HE has a high solubility and a small difference in solubility depending on pH and temperature, making it extremely difficult to purify.
Purification of DTA and DTPA can be easily carried out.

■ There are various methods for desorption of complex-forming agents adsorbed on strongly acidic cation exchangers, and the method suitable for the purpose can be applied.

■ Polyvalent cations as impurities can be separated and recovered from the complex forming agent.

As described above, the present invention is a technically and economically extremely efficient method.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these.

Example 1 Strongly acidic cation exchange resin (Amberly) IR-120
B) Pack 300 m7 into a jacketed glass column,
By passing 3N hydrochloric acid 2.000 #It,
The counter ion of the strongly acidic cation exchange resin was removed and washed with pure water.Next, the jacket temperature was maintained at 60°C, and the HB
DTA: 0. [118 mol/l, al-: a
, 1eq/l, yttrium (Y)=95119/l
, pH 2, 817) The HED'l'A aqueous solution was passed through the column at a superficial velocity of about Hr-'. When the initial effluent is further passed through, HEDTA breaks through and the HEDTA concentration in the effluent reaches α002 m at the time of 6.91 inflow.
ol/t, and the flow of fluid was stopped (Y had not broken through). All previous effluent was purged.

Next, 4.4 t of pure water was passed through the SV near Hr' for cleaning at 80° C., the initial effluent was stored separately to avoid containing 200 d of Cjl-, and 4.2 t of the subsequent effluent was collected. Vaginal fluid contained HEDTA: 0.027 mol/l, C1:
Below 0.005eq/, Y: 0.01 cumulative ti/
was as follows, and a purified HEDTA aqueous solution was obtained.

Claims (1)

[Claims] (1) Supply an aqueous solution of an aminopolyacetic acid complex-forming agent containing impurities to a column packed with a strongly acidic cation exchanger until the concentration of the complex-forming agent in the flowing liquid becomes 5 to 80% of that in the feed liquid. , and then desorbing the adsorbed complex forming agent.