JPS6018760B2 - Electrolytic recovery method of metallic zinc from acid solution containing zinc and iron generated from a metallic galvanizing factory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrolytically recovering metallic zinc from an acid solution containing zinc and iron generated from an acid dissolution process of defective plated products in a metal galvanizing factory for steel materials.

In electric or hot-dip galvanizing factories for steel materials, zinc whose dissolving power has already decreased due to the process of dissolving zinc with an acid such as defective plated products or dross from molten zinc and zinc oxide residue, etc.
A large amount of acid solution containing iron is generated.

Conventionally, in most cases, such acid solutions have been neutralized with alkali and then discarded, but this not only causes pollution problems but is also unfavorable from the standpoint of effective use of resources. Recently, attempts have been made to recover zinc and iron from acid solutions, but no effective means have yet been developed. The present invention provides a novel method for efficiently recovering active ingredients from acid solutions containing zinc and iron as described above, and has extremely high industrial value. The recovery method of the present invention utilizes electrical energy to convert the acid solution into
By electrolyzing, the main purpose is to recover zinc, which is an active ingredient, as a metal.However, if an acid solution containing zinc and iron is simply electrolyzed, the metal zinc will have a relatively low current efficiency. Although it is often deposited on the cathode, various problems occur when electrolysis is continued further, making electrolysis practically impossible. That is, when electrolysis is continued, the current efficiency for zinc deposition is significantly reduced, and at the same time, a large number of pores are formed on the surface of the metallic zinc deposited on the cathode surface, and the zinc is redissolved. For example, an acid solution consisting of 65 parts of zinc, 25 parts of iron, and 90 parts of free sulfuric acid,
When electrolysis is carried out at 3.4 A/d at 0:00, the current efficiency for zinc deposition is 84% at the beginning of electrolysis, but the current efficiency drops to 72% one hour after the start of electrolysis. If electrolysis is continued further, the zinc deposited on the cathode will be completely dissolved after 5 hours. The inventor of the present invention aims to provide a method for recovering metallic zinc from the acid solution in a stable manner over a long period of time without causing such a phenomenon. It was found that the acid concentration and the iron/zinc concentration ratio have a large influence.

That is, both when the acid concentration is high and when the iron-to-zinc concentration ratio is high, the above phenomenon is accelerated, leading to a decrease in current efficiency and dissolution of precipitated zinc. The present invention provides a method that can achieve the above object by employing a novel means for adjusting the iron/zinc concentration ratio in the acid solution based on the above novel findings.

That is, the feature of the present invention is that a solution containing zinc and iron produced from a metal galvanizing factory is deoxidized to adjust its pH.
After adjusting the concentration of iron/zinc in the solution to O ~ 3, contact it with a chelating ion exchange resin to determine the concentration of iron/zinc in the solution.
The purpose is to perform electrolysis with a ratio of 0.025 or less to selectively deposit metallic zinc on the cathode of an electrolytic cell. Conventionally, there is no known method for selectively removing only iron using a chelating or ion exchange resin as a pretreatment for effectively recovering zinc from an acid solution containing zinc and iron by electrolysis. Surprisingly, in the case of the above acid solution, the chelating ion exchange resin selectively adsorbs almost 100% of iron only, and easily reduces the iron/zinc concentration (T/T) ratio to 0.025 or less. be able to. The above characteristics are exhibited only when the pH of the acid solution is in the above-mentioned relatively large range, but as described above, in the case of the present invention, the acid concentration in the acid solution containing iron and zinc is reduced, Since it is originally necessary to raise the fence, the above-mentioned high pH does not pose any problem.

Hereinafter, the present invention will be explained with reference to FIG. 1 showing a typical flow sheet thereof. An acid solution 1 containing zinc and iron normally discharged from a zinc dissolving tank first enters a pH adjustment step 2 to reduce the pH to 0. -3, preferably in the range of 0.5-1.5.

As a means of deoxidizing, it is sufficient to reduce the free acid concentration.
Electrodialysis or diffusion dialysis may be used, but zinc oxidizing gas or dross may simply be added to reduce the free acid concentration. Electrodialysis or diffusion dialysis uses a cation exchange membrane and/or
Alternatively, known means using an anion exchange membrane may be employed. The acid recovered by electrodialysis or diffusion dialysis (in the case of electrodialysis, the concentrated solution, in the case of diffusion dialysis, the recovered solution) is reused in other fields or in the zinc dissolution tank, as necessary.
The pH-adjusted acid solution 3 is then preferably converted to trivalent iron from the divalent iron contained therein using a suitable oxidizing agent such as hydrogen peroxide or chlorine.

Thereafter, it is brought into contact with the acid solution chelating resin 4. Chelate resins include styrene, phenols, phenolics with condensates of aldehydes, acrylester resins, and chelate groups such as amines such as diethylenetriamine, triethylenetetramine, tetraethylenebentamine, and bentaethylenehexamine. imiminoniacetic acid or aminocarboxylic acids which are reactants of the above amines and halogenated acetic acid, alcohol amines such as jetanolamine and dipropanolamine, and those into which chelate groups of ureas such as urea and thiourea have been introduced are used. (However, M is an alkali metal or hydrogen,
A phenolic chelate resin formed by three-dimensionally crosslinking a phenol compound represented by R, , R2 is hydrogen or an alkyl group, a phenol group, and an aldehyde is preferred.

The chelate resin can be, for example, activated carbon, coal,
Can be used supported on silica gel or zeolite. The contact between the acid solution and the chelating resin is performed at a space velocity of preferably 0.
1 to 2.0, particularly 0.2 to 2.0.

The chelate resin is preferably regenerated by the action of a mineral acid regenerant 5 such as sulfuric acid or hydrochloric acid. Thus, the iron/zinc concentration ratio in the acid solution is made to be less than 0.025, preferably less than 0.009. The acid solution 6 whose acid concentration and iron/zinc concentration ratio have been adjusted to the above ranges is then electrolyzed.

In the present invention, known electrolytic cells 7 are used, but preferably, bell, silver-containing lead (about 1% A), or titanium platinum plating is used as the anode, and as the cathode, , aluminum, iron, and stainless steel are used. In particular, the use of aluminum as the cathode makes stripping of the deposited zinc very easy and allows the invention to be carried out successfully. The distance between poles is preferably kept at 15 to 30 legs. As the anion exchange membrane used as needed to lower the free acid concentration, an anion exchange membrane with low acid permeability is preferable. The higher the electrolysis temperature is, the more advantageous it is from the viewpoint of the electrical resistance of the liquid, but if it is too high, the purity of the deposited zinc will decrease, so it is preferably 20 to 50q.
It will be carried out at o. The higher the current density, the better the current efficiency for zinc deposition at the initial stage of electrolysis, but the zinc deposition is more likely to occur in a dendritic form.
It gets worse as the electrolysis progresses, and there is a risk of short circuit with the anode, so in order to obtain a smooth hazy surface and high-purity Kameyori zinc, it is necessary to use 0.5 to 1 sail/d, especially 2 to 1 d. Hiro/d〆 is preferred. When the above acid solution is subjected to electrolysis, the free acid concentration and the iron/zinc concentration ratio in the acid solution change as the electrolysis progresses, and at the same time as zinc precipitates as a metal, free acid Both the concentration and the iron/zinc concentration ratio increase.

Cathode: ZnS04→Zn (metal) 10S042-Anode:.

The free acid concentration and the iron/zinc concentration ratio of the acid solution in electrolysis are preferably a concentration corresponding to 200 μm/or less to pH 4. The range of concentrations corresponding to axis 2 is from up to, in particular, below 50 m/s, and the latter is preferably kept below 0.7, in particular below 0.1.

Therefore, if the free acid concentration or iron/zinc concentration ratio exceeds the above range, either stop electrolysis or adjust the free acid concentration and iron/zinc concentration ratio to the above range by appropriate means and then start electrolysis. can continue. To control the free acid concentration of the acid solution within the above range, for example, electrodialysis or diffusion dialysis is used.

For these electrodialysis or diffusion dialysis, known means using intestinal ion exchange membranes and/or anion exchange membranes are adopted, and a part of the acid solution during electrolysis is taken out of the system and subjected to electrodialysis or diffusion dialysis. Thereby, the acid in the acid solution is removed therefrom and the deoxidized acid solution is returned to the electrolysis. The acid recovered by electrodialysis or diffusion dialysis (concentrated solution during electrodialysis, recovered solution during diffusion dialysis) is reused in other fields or in the zinc dissolution tank as necessary. The free acid concentration can also be controlled by separating the cathode and anode of the electrolytic cell 7 for electrolyzing the acid solution with an anion exchange membrane 8, and supplying the acid solution to the cathode chamber for electrolysis. That is,
(2), the acid radicals ( For example, S04--, 01-, etc.) migrate to the anode through an anion exchange membrane, react with hydrogen ions generated at the anode, and produce and recover acid. ), if
It is particularly favorable for the deposition of zinc at the cathode, since in the cathode chamber the acid concentration does not increase beyond what was originally supplied. Further, the iron/zinc concentration ratio in the acid solution can be easily controlled by, for example, reducing the free acid concentration as described above and then bringing it into contact with the chelate resin described above.

Thus, according to the present invention, the electrolysis of the acid solution is carried out without any problems, and the electrolyzed metal zinc recovered at the cathode of the electrolytic cell has excellent purity and quality, and can be used for various purposes as metal zinc. For example, it can be recycled to molten zinc.

On the other hand, the acid solution 9, which is the mother liquor after zinc precipitation, has a reduced concentration of zinc and iron, so it can be recycled to the zinc dissolving tank again. Of course, depending on the case, it may be disposed of after being neutralized without being recycled. In addition, as mentioned above, the acid solution containing zinc and iron (zinc and iron are in the form of an acid salt) treated in the present invention is used to remove defective plated products, Or a zinc concentration of 50 to 10, such as that obtained as so-called waste liquid from a dissolution process using acids such as molten zinc-grade dross or zinc oxide gas.
0 evening/evening, iron concentration 5~100 evening/so, free acid concentration 50~
100 evenings/ itself is the main target. This does not need to be particularly called a waste liquid, and may be one that is still effective as an acid dissolving liquid. Examples of the acid include sulfuric acid and hydrochloric acid, but sulfuric acid solution is preferred because of ease of electrolytic operation. In addition to the above-mentioned zinc and iron, the Shun solution may contain other metals or substances that do not interfere with the implementation of the present invention, especially the electrolysis. Examples are given below to demonstrate the present invention more specifically, but
The present invention is not limited by the above description and the following examples, and various modifications can be made within the scope of the present invention.

Example 1 Defective hot-dip galvanized products, zinc discharged from the acid dissolving tank of the jig: 97.6 yen/so, iron: 6.4 yen, sulfuric acid: 60 yen/so
Oxidation treatment of iron ions in the waste liquid was carried out by dissolving 380 g of zinc oxide gas in the waste liquid containing 10.8 g and reducing the free sulfuric acid to 10 g/g and further adding 40 g of hydrogen peroxide. I did this.

As a result, zinc 131/Z, iron 6.4/Z, sulfuric acid 1
0 evening/It became so. 5.42 ml of this treated solution was supplied to a chelate resin tower to remove iron. A -CH2Nr(CH2COOH)2 acid solution was used as the chelate resin and supplied at a space velocity of 0.4.

The acid solution thus iron-removed contained 131 t/d of zinc, 0.2 d/d of iron, and 10 d/d of sulfuric acid. Next, the above acid solution was applied to a non-separated electrolytic tank using aluminum as the cathode and lead as the anode (cathode area: 4 mm, distance between electrodes: 2
伽) while maintaining the liquid temperature at 40℃.
I carried out electrolysis.

After electrolysis continued for 9.5 hours, the purity of the cathode was 99.9%.
471.4 pieces of metallic zinc were obtained, and the deposition current efficiency was 83%. The acid solution discharged from the electrolytic cell contains 43.7 t/d of zinc, 0.22/d of iron, and 100.8 d/d of sulfuric acid.
It was used again for circulation in the acid dissolution tank. Comparative Example Unlike the Example, the oxidized liquid obtained in the Example was directly electrolyzed in an electrolytic cell without being supplied to an ion exchanger.

The same type of electrolytic cell as in the example was used and the experiment was carried out under the same conditions. At the beginning of electrolysis, metallic zinc was deposited with a current efficiency of 97%, but when electrolysis was continued, it decreased to 52% 2 hours after the start of electrolysis, and after another 3 hours, the zinc deposited on the cathode was absorbed into the electrolyte. It started to dissolve. Example 2 Zinc discharged from the plating melting process of defective hot-dip galvanized products: 75.0 mm of zinc/10.1 mm of iron/70.1 mm of sulfuric acid
The waste liquid containing S/N was deoxidized by electrodialysis and the pH
．． The zero-strength liquid was supplied to a chelate resin tower to remove iron.

The same chelate resin as in Example 1 was used, and the acid solution was supplied at a space velocity of 1.0. The acid solution thus obtained had an iron/zinc concentration ratio of 0.003, and was electrolyzed. In the electrolytic cell, the anode and cathode are the same as in Example 1, but an anion exchange membrane "Celemion A" is used between the two electrodes.
A cathode chamber and an anode chamber were separated using "AV" (a hydrogen ion permeable anion exchange membrane product name manufactured by Asahi Glass Co., Ltd.), and the deoxidizing solution was supplied and circulated to the cathode chamber at a rate of 150 evenings/hour. , the sulfuric acid was supplied to the anode chamber at a flow rate of 100 m/hour,
It was cycled and operated for one period at a current density of 5 A/d. Metallic zinc with a purity of 99.9% and a beautiful appearance was deposited on the cathode, and the deposition current efficiency was %. The composition of the catholyte at this point was zinc oxide/oxide, iron oxide/oxide, and sulfuric acid oxide/oxide, and the sulfuric acid concentration in the anolyte was 123 oxide/oxide, which was recycled to the acid dissolution tank.

[Brief explanation of drawings]

FIG. 1 is an example of a flow sheet for carrying out the method of the present invention. 1... Acid solution containing zinc and iron, 2... Suppression step, 4... Chelate resin tower, 7...
・Electrolytic cell.

Claims (1)

[Claims] 1. After deoxidizing an acid solution containing zinc and iron produced from a metal galvanizing factory and adjusting the pH to 0 to 3, the general formula ▲ includes mathematical formulas, chemical formulas, tables, etc. ▼ (however, M is an alkali metal or hydrogen, R_1 and R_2 are hydrogen or alkyl groups), and the iron/zinc in the solution is brought into contact with a phenolic chelate resin obtained by cross-linking three-dimensionally phenols and aldehydes. Electrolyze with a concentration (g/l) ratio of 0.025 or less,
A method for electrolytically recovering metallic zinc from an acid solution containing zinc and iron, characterized in that metallic zinc is selectively deposited on the cathode of an electrolytic cell. 2. The method according to claim 1, in which deoxidation is performed by electrodialysis or diffusion dialysis. 3. A patent claim in which electrolysis is carried out using an electrolytic cell partitioned by an anion exchange membrane, and by electrolyzing the acid solution in the cathode chamber of the electrolytic cell, the acid radicals are transferred to the anode chamber and deoxidized. The method described in item 1.