JPS6296700A - Treatment of iron ion-containing liquid - Google Patents

Abstract

PURPOSE:To efficiently remove iron ions from an iron ion-contg. liquid by adjusting the pH of the extraction residue of the previous stage then supplying the same to the subsequent extraction stage in the stage of subjecting the above- mentioned liquid to an extraction treatment with >=2 stages of extraction stages. CONSTITUTION:A plating bath liquid contg. iron ions such as electrogalvanizing bath (extracting material) is first fed to the 1st stage of an extractor 1 by a piping 60 to contact the extractant. The extraction residue after the extraction of the iron ions is fed from a piping 62 to a pH adjusting tank 4 where the pH thereof is adjusted. The extraction residue subjected to the pH adjustment is subjected to the treatment similar to the above-mentioned treatment in a piping 66 by at least two stages of an extractor 2 pH adjusting tank 5, by which the iron ions are removed from the extraction material. The above- mentioned iron ion extraction is preferably executed by bringing the extracting material and extractant into contact with each other through a tubular solid film 30 such as porous polytetrafluoroethylene film. The extractant which contains >=1 kinds of primary - quaternary amines is preferable.

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.

[Conventional technology]

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 known. Zinc sulfate baths are most commonly used because the plating solution is easy to manage.

By the way, the pH of the zinc sulfate plating bath is usually kept low to dissolve zinc. Therefore, the plated iron plate,? Iron is leached from the electrolytic tank, etc., increasing the iron ion concentration in the plating bath and causing various problems. This accelerates the corrosion of metals such as pumps.

Conventionally, as a method for removing iron ions from an electrogalvanizing bath solution, the electrolytic galvanizing bath solution is passed through an exchange tower 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 a chelating ion exchange resin, the iron ion concentration (
Considering the adsorption amount of 1,000 to 1,010,000 pp and the ion exchange resin (0.2 to 0.8 mol/liter/resin), 111 raw waste liquid of about the same amount as raw water is generated, and it is necessary to treat it. In addition, since the adsorption rate is slow (SV=1 hr-'), a large amount of resin is required, and the apparatus has disadvantages such as an increase in size.

The present inventors have provided a method for efficiently removing iron ions from iron ion-containing liquids such as electrogalvanizing bath liquids.
As a method, we have discovered a method for back-extracting iron ions by bringing an iron ion-containing liquid into contact with an extractant containing at least one of -grade to quaternary amines, and then bringing the extractant into contact with dithionite. , a patent application was previously filed by the present applicant (patent application filed in 1983).
0-168340, hereinafter referred to as the "prior application") According to the method of the above-mentioned prior application, it is possible to efficiently treat a liquid containing iron ions.

By the way, in liquid-liquid extraction, the pH of the extract is generally
is an important factor that greatly affects extraction efficiency. That is,
For example, by the method of the previous application, Fe in the electrogalvanizing bath solution is
When extracting 3+ with an amine-based extractant, when the plating bath solution (extraction material) and the amine-based extractant come into contact, the p of the plating bath solution increases.
H increases and Fe(OH):+ is precipitated. Fe (O
When H)3 is precipitated, the membrane becomes clogged when extracted through a solid membrane, and even when extracted without a solid membrane, extraction becomes difficult due to emuldigonization.

Therefore, in this case, adjusting and maintaining the pH of the plating bath solution, which is the extraction material, to less than pH 3 at which Fe (OH) ] does not precipitate leads to improved extraction efficiency.

For this reason, when extracting iron ion-containing liquids such as electrogalvanizing bath liquids, it is necessary to adjust the pH to a suitable range. Generally, this is done only at the inlet of the extraction tower, and the pH of the extracted material within the extraction tower is not always maintained within a suitable range. For this reason, in the extraction process of iron ion-containing liquids, the problem of reduced extraction efficiency due to the precipitation of Fe(OH)3 remains unsolved.

[Means for Solving the L Problems] The present invention solves the above-mentioned conventional problems, and performs extremely efficient processing by well controlling the pH of the extraction material during extraction processing of iron ion-containing liquid. The present invention is a method for extracting iron ions from a liquid by bringing an iron ion-containing liquid into contact with an extractant in at least two extraction steps, the method comprising: The gist of the present invention is a method for treating an iron ion-containing liquid, which comprises adjusting the pH of the discharged raffinate and then subjecting it to a subsequent extraction step.

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

Figure 1 shows a method of extracting and back-extracting an electrogalvanizing bath solution as an iron ion-containing solution in accordance with the treatment method of the present invention. Three-liquid layer type equipment having both extraction and back-extraction functions is arranged in series. It is a system diagram showing an example of carrying out.

For convenience of explanation, a three-liquid phase type extraction device suitable for carrying out the present invention will be described. FIG. 2 is a sectional view showing a three-liquid layer type extraction device. A tubular or holofiber type solid body 1112 is attached to the extraction device.

In FIG. 2, 1O is a cylindrical device casing, and in the E part of the casing, partition plates 12.14 are provided in two stages to separate the back extraction side introduction chamber 16 and the extraction material (
An iron ion-containing liquid) introduction chamber 18 is defined. Also,
In the lower part of the device casing 10, a raffinate discharge chamber 24 and a reverse extraction side discharge chamber 26 below the raffinate discharge chamber 24 are defined by partition plates 20 and 22 provided in two stages. In addition, the partition plate 14
A first chamber is provided between and 20, and serves as an extractant chamber 28 through which an extractant flows.

A pipe-shaped solid membrane 30 is provided to communicate the extraction material introduction chamber 18 and the raffinate discharge chamber 24, and a second chamber is provided inside the pipe-shaped solid membrane 30. In addition, the reverse extraction side introduction chamber 1
The lower part of 6 is communicated with the upper part of extractant chamber 28 by a drip tube 32 . In addition, the lower part of the extractant chamber 28 is connected to the connecting pipe 3.
4 communicates with the back extraction side discharge chamber 26.

The extractant is introduced into the first extractant chamber 28 from the inlet 36, flows upward therein, reaches the outlet 38, and is extracted out of the device casing 10. In addition, extraction exit 3
8 and the inlet 36 are connected by a pipe 42 having a pump 40, and the extractant extracted from the extractor 38 is returned to the inlet 36 through this pipe 42 and continuously circulated. Ru.

A liquid containing iron and ions as the extract is introduced into the extract introduction chamber 18 from the supply port 44 and then introduced into the second chamber inside the solid membrane 10 . Then, it flows downward therein and enters the raffinate discharge chamber 24. The extraction material is this pipe-shaped solid 11930
While passing through the interior, the solid 830 comes into contact with the extractant in the extractant chamber 28 via the tube wall surface of the solid 830 . Then, extraction is performed and iron ions in the liquid are transferred into the extractant.

The extracted iron ion-containing liquid (raffinate) enters the raffinate discharge chamber 24 and is then discharged to the outside of the apparatus casing 10 from the raffinate discharge port 46.

The back extractant is introduced into the back extractant introduction chamber 16 through the supply port 48 and then fed into the extractant chamber 28 through the drip tube 32. In the present invention, the back extractant is generally Also has a large specific gravity and has the property that the extractant and the solution do not mix, so when it is sent into the extractant from the lower end of the dripping tube 32, it forms four droplets or a liquid column (in the illustrated example, the liquid The iron ions in the extractant are efficiently transferred into the back-extractant through this direct contact. do.

The back-extracting agent that has undergone this back-extraction is introduced into the back-extracting agent discharge chamber 26 through the connecting pipe 34, and then is introduced into the back-extracting agent discharge port 5.
0 to the outside of the device casing 10. As mentioned above, the specific gravity of the reverse extractant is greater than that of the extractant, so
The extractant in the extractant chamber 28 does not enter the back extraction side discharge chamber 26.

Although Fig. 2 shows an apparatus in which one pipe-shaped solid membrane is installed, there may be two or more solid membranes, and one dropping tube may also have multiple solid membranes. can. The processing capacity can be improved by installing a plurality of solid membranes or drip F tubes.

In the processing method of the present invention shown in FIG. 1 using the above-mentioned extraction device, first, the plating bath solution containing iron ions discharged from the electrolytic galvanizing bath is transferred to the first stage extraction device l through the pipe 60. It is delivered to the extraction chamber and brought into contact with the extractant in the extraction agent chamber via the solid membrane. The raffinate after extraction is sent to the pH adjustment tank 4 through the piping 62 and its pH is adjusted.

That is, as described above, in the extraction process of the present invention, if the pH of the plating bath solution, which is the extraction material, is 3 or more, precipitates may precipitate and adhere to the solid membrane, reducing the extraction efficiency. For this reason, in the pH adjustment tank 4, a pH adjustment agent such as an acid is added from the pipe 64 to adjust the pH of the raffinate to less than 3. (It goes without saying that it is preferable that the pH of the plating bath liquid supplied to the extraction device L from the piping 60 is less than 3.) However, if the pH of the extraction material is too low, the amount of extraction will decrease. Speed decreases. Therefore, it is most preferable to adjust the pH of the raffinate to about 2.4 to 2.5.

The raffinate liquid whose pH has been adjusted in the pH adjustment tank 4 is transferred to a pipe 66.
Then, it is sent to the second-stage extraction device 2 and subjected to extraction processing in the same manner. Then, the raffinate liquid is sent to the pH adjustment tank 5 through a pipe 68, and after being similarly adjusted to pH less than 3 with a pH adjustment agent from a pipe 70, it is sent to the third-stage extraction device 3 through a pipe 72.

The raffinate liquid from which iron ions have been sufficiently removed by the extraction process in the extractor 3 is returned to the electrolytic galvanizing bath through the piping 74 and reused.

When the extracted raffinate is reused in an electrolytic galvanizing bath, inconveniences occur if the raffinate contains an extractant. However, in the apparatus shown in Fig. 2, 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, and the plating bath liquid can be reused. becomes possible.

The extractant used in the present invention 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 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; di(2-ethylhexyl)amine and dilaurylamine.

3. Secondary amines such as 3,5,5,7.7-hexamethyloctylamine; trihexylamine, trioctylamine, triisooctylamine, trilaurylamine,
Tertiary amines such as dimethyllaurylamine, dimethylhexadecylamine, methyldi(tridecyl)amine, dimethyloleylamine, dimethylcocoamine, trioctylamine, tridecylamine, dilaurylbenzylamine; methyltrioctylammonium chloride, dimethyldilauryl ammonium Examples include quaternary amines such as chloride and trimethyldecylammonium chloride.

The extractants that have extracted iron ions in each of the extraction devices 1 to 3 are back-extracted by the back-extractants supplied through the pipes 76, 78, and 80, and then used for circulation in each extraction device in a circulation system (not shown). be done.

In the present invention, the back-extracting agent is preferably a solution containing dithionite. For example, it is preferable to use an aqueous solution of sodium dithionite, potassium dithionite, ammonium dithionite, etc. By back-extracting with an acid salt, ferric ions in the extractant are reduced to ferrous ions, which facilitates back-extraction, making it possible to perform back-extraction at a high back-extraction rate. Moreover, the ferrous ions back-extracted into the back-extracting agent can be easily crystallized and recovered.

The back-extracting agent that has been back-extracted the extractant is
is discharged from each extraction device 1 to 3, and passes through piping 88 to p.
After passing through the H adjustment tank 6, solid-liquid separation tank 71 and reaction tank 8, it is used again in the extraction devices 1 to 3.

That is, in the present invention, back extraction is performed at a higher pH than extraction.
That is, it is preferable to perform the extraction at a pH of 3 or more, especially in a neutral range. Therefore, the back extraction agent is first added to the pH adjustment tank 6 through the pipe 90 to adjust the pH to a suitable pH.
Adjust to.

Furthermore, when the back-extracted iron ions are highly concentrated in the back-extracting agent, the iron ions precipitate as ferrous salt or ferric salt crystals. Alternatively, when zinc is present in the back-extracting agent, the back-extracted iron reacts with the zinc to form a precipitate. Therefore, the pH-adjusted back extractant is sent to the solid-liquid separation tank 7 through a pipe 92 for solid-liquid separation, and iron solids are recovered from the back extractant through a pipe 94. As the solid-liquid separation tank 7, a filtration tank, a precipitation tank, a crystallization tank, etc. are preferable.

Since the crystallization and recovery of iron solids is promoted by the coexistence of zinc, the method of the present invention is particularly effective in treating liquids containing both iron and zinc, such as electrogalvanizing bath liquids. . However, even if the liquid does not contain zinc,
Crystallization recovery can be carried out advantageously by separately adding a zinc salt to the back-extracting agent.

Furthermore, when using a reducing agent such as dithionite as a back-extracting agent, the liquid after solid-liquid separation is sent to the reaction tank 8 through piping 96, and the reducing agent is added through piping 98 to achieve a reducing effect. Preferably, it is restored.

The back extractant thus regenerated is circulated to the extractors 1 to 3 through the pipes 100 and 76 to 80, respectively.

The processing method shown in FIGS. 1 and 2 is an example of the method of implementing the present invention, and the present invention is not limited to the method shown in FIGS. 1 and 2. .

For example, as the extraction device, a three-liquid layer type device having both an extraction function and a back-extraction function as shown in FIG. 2 may be used, or an independent extraction device and a back-extraction device may be used.

In addition, in FIG. 1, the extractor is of a three-column series type, but a Z-column or four or more columns may be arranged as necessary. However, separate circulation lines may be provided for each.

Further, in the above, an extraction method in which the extraction material (i.e., plating bath liquid) and the extractant are brought into contact through a solid membrane has been described, but in the present invention, a mixer Φ settler type,
An extraction method such as a spray tower in which the extraction material and the extractant come into direct contact may be employed.However, as mentioned above, from the viewpoint of reusing the raffinate, a solid membrane contact method is preferable.

As the solid membrane of the extraction device, various types such as a tubular type, a hollow fiber type, and a flat membrane type can be used.

Further, the solid membrane may be porous, such as polytetrafluoroethylene (hereinafter referred to as "rPTFE"),
Cellulose acetate, polysulfone.

Examples include semipermeable membranes made of polyvinyl chloride, polypropylene, polyamide, etc., with PTFE being particularly preferred;
TFE has excellent chemical resistance and hydrophobicity, and has an extremely high extraction rate, making it suitable for use as a solid membrane.

Porous PTFE membrane.

The membrane thickness, pore size, etc. are selected depending on the extractant used.

The reason why the extraction rate of the PTFE solid membrane is so fast is not clear, but due to its network structure and extreme hydrophobicity (lipophilicity), the contact area between the extracted material and the oil agent covers not only the pores but also the entire membrane surface. Therefore, it is presumed that this is because the diffusion within the membrane is also fast.

The back-extraction agent and the extractant may be brought into contact through a solid membrane, or may be brought into direct contact without going through a solid membrane. Generally, if they are brought into contact through a solid membrane, emulsification etc. can be prevented. Good extraction can be carried out, and when direct contact is made without intervening a solid membrane, the extraction rate is fast, and there is an advantage that there is no possibility of crystals adhering to the solid membrane.

Examples of the iron ion-containing liquid to be treated in the method of the present invention include stainless steel pickling wastewater, steel sheet manufacturing wastewater, air preheater cleaning wastewater, and the like.

In addition, as a liquid containing iron ions and zinc ions,
In addition to the above-mentioned electrogalvanizing bath solution, zinc moisture control type metallurgical waste solution and the like can be mentioned.

[Function] In the present invention, the extraction process is divided into two or more stages, and the raffinate in the first stage is pH-adjusted and then sent to the second stage extraction process.

To ensure that the pH is adjusted within the appropriate pH range for extraction.

Iron ions in the iron ion-containing liquid can be efficiently removed.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example I pH containing 2890 ppm of Fe, 91000 ppm of Zn
The electrolytic galvanizing bath solutions Nos. 1 and 8 were extracted according to the method of the present invention by arranging three extraction devices in series as shown in FIG. However, in this example, the raffinate from the third column was circulated to the inlet of the first column.

As the solid M30 of each extraction device, a tubular membrane made of polytetrafluoroethylene with an inner diameter of 10 mm and an area of 150 crnj was used. Through this solid membrane 30, plating bath solution tiL is passed from the extraction chamber 18 at a rate of 1600 ml/min.
Add 40voJL of triisooctylamine to the extractant chamber 28.
1.4ft of kerosene liquid containing 1200mJL/min
I circulated it. On the other hand, 100 g/H of NA3 S204 (pH 6.0-6.5 with NaOH) was used as a back-extractant.
@) 500ml for 200m! Back extraction was carried out by directly dropping droplets into the extractant at a flow rate of L/min. The plating bath liquid is supplied to the extraction device l at the inlet of the extraction device. The raffinates from 1 and 2 are pH-adjusted with H2SO4 in pH adjustment tanks 4 and 5, respectively, and kept at a constant pH of 2.
, 4 to 2.5. In addition, the back extractant is used in the pH adjustment tank 6. It was passed through a solid-liquid separation tank 7 and a reaction tank 8 for circulation use.

As a result, F in the plating bath solution of the raffinate from the extractor 3
e is 1300 ppm, and the average extraction rate is 8,8
Fe was removed very efficiently at g-Fe/tn'·hr. (Note that in this extraction process, p
H2SO4 used for H adjustment was 4000 ppm.

) From the solid-liquid separation tank 7 of the back extractant, a precipitate equivalent to 1940 ppm of Fe and 2440 ppm of Zn was precipitated.

In addition, in the above experiment, when the back extractant was recycled without any treatment, the Fe content in the back extractant was 2550.
ppm and Zn were 3450 PPm, indicating a decrease in back extraction efficiency.

Comparative example 1.

The plating bath solution was extracted in the same manner as in Example 1 except that no pH adjustment was performed.

As a result, the pH of the plating bath solution of the raffinate in the extractor 3 was 3.
．． 1, the membranes of each extraction device became clogged, and the extraction speed decreased significantly.

Comparative example 2 Extraction device! The total amount of H 2 SO 4 used in Example 1 (4000 ppm) was added to the plating bath solution supplied to the il, so that the pH of the solution was 1.4), and the pH in the pH adjustment tank 4.5 was increased.
Extraction treatment of the nozzle bath liquid was carried out in the same manner as in Example 1 except that H adjustment was not performed.

As a result, the plating bath solution of the raffinate from the extraction device 13 has a p
H is 2.4, its Fe content is 1780PPm,
The average extraction rate was 6.2 g-Fe/m'·hr.

From the results of Example 1 and Comparative Examples 1 and 2, it is clear that extremely excellent treatment effects can be achieved by dividing the extraction process and adjusting the pH between each extraction process as in the present invention.

[Effects] As detailed above, the method for treating an iron ion-containing liquid according to the present invention involves extracting the iron ion-containing liquid through at least two extraction steps, adjusting the pH of the raffinate in the first stage, and then adjusting the pH of the raffinate in the second stage. It is used for the extraction process, and it becomes possible to always maintain the iron ion-containing liquid in the extraction system in the optimum pH range for extraction.

Therefore, iron ions in the iron ion-containing liquid can be removed extremely efficiently under optimal pH conditions.

[Brief explanation of drawings]

FIG. 1 is a system diagram for explaining the method of the present invention, and FIG. 2 is a diagram showing the configuration of a unit extraction device suitable for implementing the present invention. 1.2.3...Extraction device, 4.5...pH adjustment tank. 6...pH adjustment tank, 7...solid-liquid separation tank. 8... Reaction tank, 10... Device casing,
16... Reverse extraction agent introduction chamber, 18... Extraction material introduction chamber, 2
4... Raffinate discharge chamber, 26... Reverse extractant discharge chamber, 2
8... Extraction chamber, 30... Solid membrane. Agent Patent Attorney Tsuyoshi Shigeno Figure 1 Figure 2

Claims (5)

[Claims] (1) A method of extracting iron ions from the liquid by bringing the iron ion-containing liquid into contact with an extractant in at least two extraction steps, and adjusting the pH of the raffinate liquid discharged from the previous extraction step. 1. A method for treating an iron ion-containing liquid, which is characterized in that the iron ion-containing liquid is subjected to a subsequent extraction step. (2) The processing method according to claim 1, wherein the extraction in the extraction step involves bringing the extraction material into contact with the extractant through a solid membrane. (3) The treatment method according to claim 1 or 2, wherein the extractant contains at least one type of primary to quaternary amine. (4) The treatment method according to any one of claims 1 to 3, characterized in that the extractant is brought into contact with a back-extractant and then recycled and reused. (5) The treatment method according to claim 4, wherein the back extractant is subjected to solid-liquid separation after pH adjustment and then recycled and reused.