JPS62247884A - Treatment of iron ion-containing liquid - Google Patents

Abstract

PURPOSE:To effectively remove ions from an iron ion-contg. liquid by bringing the iron ion-contg. liquid and an extracting agent contg. at least one kind of primary and quaternary amines into contact with each other and bringing the extracting agent into contact with a back extracting agent having specific pH and contg. a reducing agent. CONSTITUTION:The iron ion-contg. liquid such as electrogalvanizing bath liquid and the extracting agent contg. at least one kind among the primary and quaternary amines are brought into contact with each other via a solid film 2 consisting of a polytetrafluoroethylene, etc., in an extracting device 3. The extracting agent is then brought into contact with the back extracting agent having <=3.5pH and contg. the reducing agent (e.g., dithionite) to back extract the iron ions. As a result, the iron ions in the iron ion-contg. liquid is efficiently removed and the iron ions are back extracted with high back extraction efficiency. The extracting agent can be, therefore, cyclically used. The amt. of the waste liquid to be treated is extremely small. Since the accumulation of the SS in the extracting agent is prevented, the efficient extraction is continuously executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for treating iron ion-containing liquids, and in particular to a method for efficiently removing iron ions from iron ion-containing liquids such as electrogalvanizing bath liquids. This invention relates to a method for treating a liquid containing iron ions.

[Prior Art] As electrogalvanizing baths used in the production of electrogalvanized iron sheets, zinc sulfate baths, chloride baths, borofluoride baths, alkaline cyanide baths, birophosphoric acid baths, etc. are conventionally known. However, among these, the zinc sulfate bath is most commonly used because the plating solution is easy to manage. .

Incidentally, the pH of the zinc sulfate plating bath is usually kept low in order to dissolve zinc. Therefore, iron is leached from the plated iron plate, electrolytic tank, etc., and the iron ion concentration in the plating bath increases, causing various problems. For example, it may deteriorate the surface properties of the resulting electrogalvanized iron plate, or it may accelerate the erosion of metals in electrolytic tanks, piping, pumps, etc.

Conventionally, as a method for removing iron ions from an electrogalvanizing bath solution, the electrolytic galvanizing bath solution is passed through an exchange column filled with a chelating ion exchange resin, and iron ions are adsorbed and removed (Japanese Patent Publication No. 57-27960). ) has been proposed. According to this method, it is possible to selectively remove iron ions from the electrogalvanizing bath solution.

[Problems to be solved by the invention] However, in the method using chelating ion exchange resin, the iron ion concentration (
Considering the amount of adsorption of the ion exchange resin (0.2 to 0.8 moles/resin), approximately the same amount of recycled waste liquid as the raw water is generated and must be treated. Furthermore, since the adsorption rate is slow (SV=about 1 hr'), a large amount of resin is required, and the apparatus has disadvantages such as an increase in size.

[Means for Solving the Problems] The present invention provides a method for efficiently removing iron ions from an iron ion-containing solution such as an electrogalvanizing bath solution, comprising: an iron ion-containing solution; It is characterized by contacting with an extractant containing at least one of primary to quaternary amines, and then contacting the extractant with a back-extracting agent containing a reducing agent at a pH of 3.5 or less to back-extract iron ions. The gist is a method for treating iron ion-containing liquids.

That is, as a method for efficiently removing iron ions from an iron ion-containing liquid, the applicant has developed a method for efficiently removing iron ions from an iron ion-containing liquid.
A method for treating a liquid containing iron ions, which comprises contacting the liquid with an extractant containing at least one type of quaternary amine, and then contacting the extractant with a dithionite salt to back-extract iron ions. ” (Japanese Patent Application No. 168340-1983)
Hereinafter referred to as "prior application". ).

According to the method of the above-mentioned prior application, iron ions can be removed from iron ion-containing liquids with extremely high efficiency. However, if extraction is continued for a long time, SS containing iron in the extractant may It was found that the SS accumulates and, in the case of extraction through the membrane, the SS is deposited on the membrane. Furthermore, even in the case where no membrane is used, there is a risk that the extraction efficiency will deteriorate due to emulsification.

In order to solve these problems, the wood inventors mainly studied the pH of the back-extracting agent, and found that
The present invention was completed based on the finding that when the pH at which SS is dissolved is 1, that is, pH 3.5 or lower, there is almost no accumulation of SS and no adhesion to the membrane.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a system diagram showing an example in which extraction and back-extraction of an electrolytic galvanizing bath solution as an iron ion-containing solution are performed using independent devices, respectively, according to the treatment method of the present invention.

In this example, the plating bath solution containing iron ions discharged from the electrolytic galvanizing bath 1 is first transferred to the solid film 2 through the pipe 6.
The extractant is fed to the extraction chamber 3a of the extraction device 3 partitioned by 1, and brought into contact with the extractant containing at least one of primary to quaternary amines in the extractant chamber 3b via the solid membrane 2.

In this extraction process, if the pH of the plating bath solution, which is the extraction material, is 3 or higher, precipitates may precipitate and adhere to the solid membrane, reducing extraction efficiency. For this reason, the pH of the plating bath solution to be treated is preferably less than 3.

In the present invention, the extractant used is preferably one in which at least one of primary to quaternary amines is adjusted to an amine concentration of about 1 to 80% by weight using a diluent such as a petroleum hydrocarbon.

Preferred specific examples of primary to quaternary amines used include tert-icosylamine, 1-(3-ethylpentyl)-4-ethyloctylamine, 1,1,3.3
- Primary amines such as tetramethylbutylamine and laurylamine; secondary amines such as di(2-ethylhexyl)amine, dilaurylamine, 3.3,5,5,7.7-hexamethyloctylamine, nitrihexylamine, Trioctylamine, triisooctylamine, trilaurylamine, dimethyllaurylamine, dimethylhexadecylamine, methyldi(tridecyl)amine, dimethyloleylamine, dimethylcocoamine, tricaprylylamine, tridecylamine, dilaurylbenzylamine, etc. Quaternary amines include quaternary amines such as methyltrioctylaminemonium chloride, dimethyldilauryl ammonium chloride, and trimethyldecylammonium chloride.

The iron ions in the plating bath liquid are extracted by the extractant and removed by the extraction device 3.

The plating bath liquid (raffinate liquid) from which iron ions have been removed is transferred to piping 7.
It is returned to the electrolytic galvanizing bath 1 and reused.

That is, when an extracted plating bath solution is reused in an electrolytic galvanizing bath, problems may occur if the plating bath contains an extractant. However, in the apparatus shown in Figure 1, extraction is carried out using a solid membrane contact method with little loss of extractant, so there is almost no extraction agent mixed into the plating bath liquid from the raffinate solution, and the plating bath liquid is not recycled. It becomes possible to use it.

The solid membrane 2 of the extraction device 3 may be a flat membrane type or a tubular type.
Various forms are used, such as a mold and a holofiber type.

The solid membrane may be porous, such as polytetrafluoroethylene (hereinafter referred to as "rPTFE"),
Semipermeable membranes such as cellulose acetate, polysulfone, polyvinyl chloride, polypropylene, and polyamide may be used, but PTFE is particularly preferred. In general, PTFE has excellent chemical resistance and hydrophobicity, and also has an extremely high extraction rate, making it suitable for use as a solid membrane. Porous PTFE membrane is
The membrane thickness, pore size, etc. are selected depending on the extractant used.

It is not clear why the extraction rate of the PTFE solid membrane is so fast, but due to its network structure and extreme hydrophobicity (lipophilicity), the contact area between the extractant and the extraction agent is not limited to the pores, but covers the entire membrane surface. This is presumed to be due to fast diffusion within the film.

Although FIG. 1 shows an extraction device in which the extraction material (i.e., plating bath liquid) and the extractant are brought into contact with each other through a solid membrane, in the present invention, a mixer-settler type, a spray tower, etc. An extraction method in which the extraction material and the extractant are brought into direct contact may also be adopted. However, as mentioned above, from the viewpoint of reusing the raffinate, it is preferable to use the solid membrane contact method.

The extractant from which iron ions have been extracted in the extraction device 3 is sent to the back extraction device 4 through a pipe 8, and brought into contact with a back extraction agent containing a reducing agent at a pH of 3.5 or lower to perform back extraction.

In the present invention, as the reducing agent, it is preferable that dithionite salts such as sodium dithionite, potassium dithionite, and ammonium dithionite have a strong reducing power, but other salts such as sulfites, etc. Reducing agents can also be used.

In addition, when dithionite is used as a reducing agent, it is preferable to add it at a high concentration to the back-extracting agent at the beginning of back-extraction because dithionite is easily decomposed at low pH. Rather, it is preferable to periodically add small amounts using ORP control or a metered injection method.

The back extractant and the extractant may be brought into contact with each other in the back extraction device 4 through a solid membrane, or may be brought into direct contact without going through a solid membrane. In general, if the contact is made through a solid membrane, emulsification etc. can be prevented and good extraction can be carried out, and if the contact is made directly without going through a solid membrane, the extraction speed is fast.
There is an advantage that there is no possibility of crystal attachment to the solid film.

It is preferable to recycle and reuse the extractant after back extraction as much as possible from the viewpoint of waste liquid treatment or resource saving. It can then be treated in the alkaline washing tower 5, and then directly circulated to the extraction device 3 via piping 11 for reuse.

On the other hand, by circulating the back-extracting agent through the pipe 13, the back-extracted iron ions are highly concentrated in the back-extracting agent. In this case, iron ions can be crystallized and recovered from the back-extracting agent as ferrous salt crystals (piping 15 in FIG. 1). By doing this, the Tokuko Sho 57-2
In the treatment method using an ion exchange resin disclosed in No. 7960, an extremely small amount of the back extractant liquid corresponding to the welfare waste liquid of the ion exchange resin is sufficient, and problems such as waste liquid treatment are also solved.

In addition, as mentioned above, in the present invention, back extraction is performed at pH 3,
This pH adjustment is carried out at a pH of 5 or less, and a common acid or, if necessary, an alkali can be used for this pH adjustment.

In addition, when zinc is present in the back-extracting agent, the back-extracted iron reacts with the zinc to form a precipitate, making it easier to crystallize and recover iron from the back-extracting agent. The method of the present invention is particularly effective in treating solutions containing both iron and zinc, such as electrogalvanizing bath solutions. However, even if the liquid does not contain zinc, it is possible to advantageously perform crystallization and recovery by separately adding a zinc salt to the back-extracting agent.

Examples of the iron ion-containing liquid to be treated in the method of the present invention include stainless steel pickling wastewater, steel plate manufacturing wastewater, electric preheater cleaning wastewater, and the like. In addition, examples of the liquid containing iron ions and zinc ions include the electrolytic galvanizing bath liquid described above, a zinc moisture control type metallurgical waste liquid, and the like.

The above describes the case where the method of the present invention is implemented using an independent and separate extractor and back-extractor.
The method of the present invention can be easily carried out using a three-liquid layer type device that has both an extraction function and a back extraction function.

[Function] By extracting the iron ion-containing liquid with an extractant containing at least one of primary to quaternary amines, iron ions in the liquid can be efficiently removed.

In addition, by back-extracting the extractant with a reducing agent such as dithionite, the ferric ions in the extractant are reduced to ferrous ions, making back-extraction easier and increasing the back-extraction rate. Back-extracted at speed.

However, if the pH of this back extractant is 3.5 or less,
Iron ions are difficult to turn into ferric ions, and even if they become ferric ions, they dissolve and do not become a source of SS. This prevents the accumulation of iron-containing SS in the extractant, and prevents SS from adhering to the membrane.
Long-term operation is not hindered by emulsification etc.

Therefore, it is possible to recirculate the extractant in the extraction process and continue the process stably for a long period of time.

The ferrous ions back-extracted into the back-extracting agent can be easily crystallized and recovered.

[Examples] The present invention will be explained in more detail below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example I pH containing 3250pp of lFe, 37400pp of ZZn
EXAMPLE 2.1 Electrolytic galvanizing bath liquid was subjected to extraction treatment according to the method of the present invention using the apparatus shown in FIG.

A polytetrafluoroethylene membrane with an area of 150 cm' is used as the solid membrane 2 of the extraction device 3, and the plating bath liquid of the plating bath 1 is supplied to the extraction chamber 3a through the piping 6.
The liquid is passed through the extractant chamber 3 at a rate of 1,500m/min.
1.05 ml of kerosene solution containing 40 vol% of tri-n-octylamine was passed through b at a rate of 3000 m ml/min. The extractant was fed at a flow rate of 200 mu/min to the back extractor 4 through which 1.6 mt of back extractant was circulated through a pipe 8.

Note that this back-extracting agent contains NA35204 and Na in distilled water.
From Rucotoni adding OH and H2SO4, pH 3,0
The treatment was carried out under adjustment control at ~3.5.0 RP -280 to -320 mV.

As a result, the extraction rate of iron ions from the plating bath solution was 8.
The temperature was maintained at about 9 g-Fe/m'-hr, and no SS deposition occurred on the membrane even after continuous treatment for 50 hours.

Example 2 Using N a 2 S O3 as the reducing agent of the back extractant,
0RP300-310mV (Na in Example 1
The treatment was carried out in the same manner as in Example 1, except that the added amount was adjusted to a value that was approximately the same as the added weight of 2S 204.

As a result, the extraction rate of iron ions from the plating bath solution was 8.
The temperature was maintained at approximately 8 g-Fe/rn'·hr, and no SS precipitation adhered to the film even after continuous treatment for 50 hours.

Comparative Example 1 Reverse extractant 100 g/l Na2S
The treatment was carried out in the same manner as in Example 1, except that 204 was used and the pH was adjusted to 5.8 to 5.9.

As a result, the initial extraction rate of iron ions from the plating bath solution was approximately 8.8 g-Fe/g-hr, but from around 20 hours after the start of extraction, SS began to adhere to the membrane, and the extraction rate gradually increased. decreased.

From the results of the above Examples and Comparative Examples, it is clear that according to the method of the present invention, continuous treatment can be performed stably and with high efficiency over a long period of time.

[Effects of the Invention] As detailed above, the method for treating an iron ion-containing liquid of the present invention provides a method for treating an iron ion-containing liquid by treating the iron ion-containing liquid with at least one of primary to quaternary amines.
contact with an extractant containing seeds, and also adjust the pH of the extractant after extraction.
This method performs back extraction with a back extraction agent containing a reducing agent with a molecular weight of 3.5 or less, and (1) iron ions in an iron ion-containing liquid can be removed extremely efficiently.

■ Iron ions can be back-extracted with high back-extraction efficiency.

■ This makes it possible to recycle the extractant.

■ The amount of waste liquid to be treated is extremely small.

In addition, it has the following advantages: ■ It prevents the accumulation of SS in the extractant, reducing the amount of S on the membrane.
No S adhesion or emulsification occurs,
It becomes possible to perform efficient extraction stably and continuously for a long period of time.

This effect is produced and it is extremely advantageous industrially and economically.

[Brief explanation of drawings]

FIG. 1 is a system diagram illustrating the method of the present invention. ■...Electrogalvanizing bath, 2...Solid film, 3...
・Extraction device, 4... Reverse extraction device.

Claims (4)

[Claims] (1) After bringing the iron ion-containing liquid into contact with an extractant containing at least one of primary to quaternary amines, the extractant is adjusted to pH 3.
．． A method for treating an iron ion-containing liquid, the method comprising back-extracting iron ions by bringing the liquid into contact with a back-extracting agent containing a reducing agent at a concentration of 5 or less. (2) The treatment method according to claim 1, wherein the iron ion-containing liquid and the extractant are brought into contact through a solid membrane. (3) The treatment method according to claim 1 or 2, wherein the iron ion-containing liquid is an electrogalvanizing bath liquid. (4) The treatment method according to any one of claims 1 to 3, wherein the reducing agent is a dithionite salt.