JPH0212637B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating a pickling solution for pickling metals.

BACKGROUND ART Conventionally, it is well known that when plating, painting, or other surface treatments are applied to metals such as iron or iron alloy plates, steel plates, etc., pickling is performed for the purpose of removing rust or the like prior to these treatments. The solution used for such pickling is, for example, an aqueous mineral acid solution such as hydrochloric acid or sulfuric acid, and the waste liquid produced by pickling the metal still contains a large amount of acid. If this is disposed of, not only will there be a loss of acid, but there is also the risk of causing pollution, so neutralization is generally carried out, but this is expensive. Therefore, in recent years, attempts have been made to recover and reuse acid from these pickling waste liquids, and in particular, a metal pickling system that combines diffusion dialysis using an anion exchange membrane has been proposed. According to such a system, a part of the solution in the pickling tank is subjected to diffusion dialysis to recover and reuse the acid, and at the same time, the treated solution is disposed of after recovering iron compounds and the like in a separate process depending on the case. Ru. By making effective use of acid in methods such as this system, the actual amount of acid consumed is significantly reduced compared to conventional methods. However, it has been found that another problem is that metals and various impurities inevitably introduced from the chemicals used accumulate in the pickling solution.

In particular, when copper ions in the pickling solution accumulate above a certain concentration, they precipitate and adhere to the surface of metals such as iron.
This may adversely affect surface treatment in the next process.
It must be removed along with the SS portion. The inventors of the present invention filed a patent application in 1982 regarding the method for removing copper ions mentioned above.
-84916 and Japanese Patent Application No. 58-33804. That is, according to these methods, the pickling liquid is extracted from the pickling tank and a soluble sulfur compound is added to the circulating liquid to be resupplied, thereby achieving an extremely good decopper removal effect. However, when coagulating and filtering using a flocculant used to remove SS components and the above-mentioned soluble sulfur compounds, it was difficult to simultaneously satisfy both the copper removal effect and the SS removal effect. .

As a result of studying the above causes, the inventor found that
When using coagulants and soluble sulfur compounds,
The present invention was completed based on the knowledge that the temperature of the processing liquid is extremely important.

That is, the present invention maintains the pickling liquid (i.e., pickling waste liquid) extracted from a metal pickling tank at a temperature of 20 to 50°C, and absorbs soluble sulfur that can form an insoluble compound with a flocculant and copper ions. This method of treating a pickling liquid is characterized in that, after adding a compound and separating a precipitate, at least a portion of the separated liquid is re-supplied to a pickling tank without removing the acid. Therefore, according to the present invention, the pickling liquid that is circulated and re-supplied to the pickling tank becomes an acid solution from which copper ions have been removed and is re-supplied to the pickling tank. This makes it possible to always maintain a low copper ion concentration that does not interfere with metal cleaning.

The present invention also adds specific additives to the pickling waste liquid, and controls the temperature of the pickling waste liquid during coagulation and filtration.
It is important to keep the temperature at 20 to 50°C, preferably 30 to 40°C.By setting the temperature to this temperature, the SS content and copper ions in the pickling waste liquid can be efficiently removed, and the filtration efficiency can be increased. The temperature of pickling waste liquid is
If the temperature is higher than 50°C, the insoluble salt produced by the reaction between the soluble sulfur compound and copper is decomposed and redissolved, resulting in a poor copper removal effect. Furthermore, at temperatures lower than 20°C, the filtration efficiency decreases, making it impossible to achieve the object of the present invention. Methods of controlling the temperature above include, for example, using a fuel exchanger.
There are no particular restrictions.

The flocculant used in the present invention is preferably one that has a large effect of flocculating the SS content in the pickling waste liquid, such as a polymer flocculant, but is not particularly limited, and known agents can be used. I can do it. Further, the flocculant used in the present invention is not limited to the use of other flocculants for the purpose of increasing the above-mentioned effects, and in particular, the flocculant used in the present invention can be used in combination with a filter aid such as diatomaceous earth. The effect becomes noticeable.

The soluble sulfur compounds used in the present invention include substances that form insoluble salts with copper, such as sulfur compounds of alkali metals such as sodium sulfide, sodium hydrogen sulfide, and sodium polysulfide, or thiourea, ethylthiourea, diethylthiourea, and butylthiourea. Thiourea derivatives such as urea and phenylthiourea, or sulfur-containing or thiourea-based removers commonly used as heavy metal removers, such as (trade name: Oritol (manufactured by Oriental Giken), inhibitor: Ivit S
There are substances that form complexes with copper ions and precipitate, such as 600 (manufactured by Asahi Chemical Industries), etc. Among these, those using thiourea and its derivatives are preferred because the effects of the present invention are extremely large.

The amounts of the flocculant and soluble sulfur compound shown above are appropriately selected depending on the SS content and copper ion concentration in the pickling waste solution, but generally the flocculant is 50~
200 ppm and 100-500 ppm of soluble sulfur compounds are used.

At this time, the pickling waste liquid is preferably kept in a reducing atmosphere in order to facilitate agglomeration and prevent re-dissolution of aggregates.

The method, device, etc. used for the filtration of the present invention are not particularly limited, and may include, for example, a method using a filter press.

Hereinafter, a typical example using the processing method of the present invention will be explained in detail based on the drawings. FIG. 1 is a process diagram showing a processing system using the method of the present invention.
In the figure, 1 is a pickling tank, which is generally a 1 to 10 N, preferably 4 to 8 N aqueous solution of a mineral acid such as hydrochloric acid or sulfuric acid. There is a pickling solution containing several weight percent of iron sulfate, etc., and the metal to be treated is treated by a known cleaning method such as immersing the metal in this or exposing the metal to a shower of the pickling solution. In the present invention, at least a portion of the pickling waste liquid in the pickling tank is extracted through the pipe 11, allowed to settle if necessary, and in some cases, a portion is bypassed through the pipe 21 and sent to the pickling tank. Return it and transfer the remainder to heat exchanger 2.
The temperature is adjusted to 20 to 50°C, and the mixture is sent to a flocculation/filtration tank 3, where predetermined amounts of flocculant and soluble sulfur compound are added, and flocculation/filtration is performed.

The structure of the aggregation/filtration tank is not particularly limited. Generally, soluble sulfur compounds and flocculants can be added anywhere in the extraction line from the pickling tank before the flocculation/filtration tank, but they are added continuously or intermittently in the line after the heat exchanger for flocculation/filtration. It is better. The pickling waste liquid supplied to the coagulation/filtration tank is separated into solid and liquid, and the filtrate (acid) is passed through pipe 13.
and 14 routes to re-supply the pickling tank.

Furthermore, in the present invention, the filtrate (separated liquid) is divided after the pipe 12, and one of the filtrate is directly (i.e., without any additional treatment) into the pipe 1.
It is also preferable that the pickling tank is resupplied through routes 3 and 14, and that at least a portion of the other one is treated by the diffusion dialysis device 4 through the pipe 15. This device is a generally known diffusion dialysis device, and an anion exchange membrane is used as the dialysis membrane.

In the diffusion dialysis device, water is supplied to one side,
The acid is recovered and delivered to the tank 5 through a pipe 16. On the other hand, the liquid from which the acid has been removed is discharged from the system through 17. This is disposed of after performing recovery processing for metal components as necessary. In the tank 5, additional acid is added, water is replenished, or other chemicals are added depending on the pickling condition, and the water is re-supplied from the pipe 18 to the pickling tank via the pipe 14 or not. be done.

The amount of pickling solution circulated in the present invention varies depending on the process, but generally the purpose is to improve the stirring state in the pickling tank, or to maintain the acid concentration in the tank within a predetermined range, and The amount may be selected to suit the desired purpose, such as maintaining the concentration of impurities unavoidably brought into the tank below a certain limit.

In addition, when at least a part of the circulating fluid is subjected to diffusion dialysis treatment, the amount supplied to the diffusion dialysis device is the amount that can keep the salts of metals such as iron produced as by-products in the pickling tank below a certain concentration. In this case, an amount of liquid sufficient to remove the amount of by-product of the metal salt per unit time in the tank may be supplied to the diffusion dialysis apparatus and processed.

EXAMPLES Hereinafter, examples will be shown to explain the present invention in detail, but the present invention is not particularly limited to the following examples.

Example 1 Hydrochloric acid 145.8g/, Fe53.1g/, Cu333ppm,
The pickling waste liquid containing SS325ppm was maintained at 34℃ and the polymer flocculant Himoroku K-380 (manufactured by Kyoritsu Organic Co., Ltd.) was applied.
100 ppm was added and the agglutination reaction was carried out for 5 minutes. Next, 300 ppm of 5% thiourea aqueous solution was treated and reacted for 10 minutes. Add 200ppm of diatomaceous earth to this and add 50
Filtered using cm filter press test machine.

The results were as follows.

Processing capacity: 2.6/Hr Processing liquid Cu: 155ppm Comparative example 1 Hydrochloric acid 145.8g/, Fe53.1g/, Cu333ppm,
The pickling waste solution containing SS925ppm was maintained at 55℃ and the polymer flocculant Himoroku K-380 (manufactured by Kyoritsu Organic Co., Ltd.) was applied.
100 ppm was added and the agglutination reaction was carried out for 5 minutes. Next, 300 ppm of 5% thiourea aqueous solution was added and reacted for 10 minutes. Mix 200ppm of diatomaceous earth with this and make 50
Filtered using cm filter press test machine.

The results were as follows.

Processing capacity: 3.7/Hr Processing liquid Cu: 189ppm Comparative example 2 The same pickling waste liquid as in Comparative example 1 was maintained at 17°C and the polymer flocculant Himorok K-380 (manufactured by Kyoritsu Organic Co., Ltd.) was added.
100 ppm was added and the agglutination reaction was carried out for 5 minutes. Next, 300 ppm of 5% thiourea aqueous solution was added and reacted for 10 minutes. Mix 200ppm of diatomaceous earth with this and make 50
Filtered using cm filter press test machine.

The results were as follows.

Processing capacity: 1.2/Hr Processing liquid Cu: 126ppm

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a processing system using the method of the present invention. In the figure, 1 is a pickling tank, 2 is a heat exchanger, 3 is a coagulation/filtration tank, 4 is a diffusion dialysis device, and 5
is a tank.

Claims (1)

[Claims] 1. The pickling liquid extracted from the metal pickling tank is
After separating the precipitate by adding a flocculant and a soluble sulfur compound that can form an insoluble compound with copper ions while maintaining the temperature at ~50°C, at least a portion of the separated liquid is transferred to a pickling tank without removing the acid. A method for treating a pickling solution, characterized in that the pickling solution is resupplied.