JPS6058177B2 - Method for recovering iron from etching waste liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering iron from an etching waste solution consisting of a ferric chloride hydrochloric acid solution.

In recent years, etching of various metals, particularly stainless steel, copper, straight brass, etc., has become widespread, and the treatment of waste liquid and recovery of metals have become issues.

For example, there are engravings on stainless steel doors, stainless steel etching on mixer/juicer filtration screens, copper etching on printed circuit boards for automobile switches, etc., and ferric chloride solution is mainly used as the etching agent. Since the waste liquid contains impurities such as Zn, Ni, and Cr, it is not easy to treat it and recover iron.

It is known that trivalent iron in a hydrochloric acid solution can be extracted with trialkyl phosphoric acid or a diluted solution thereof (Japanese Patent Publication No. 45-25581), but the present inventors have discovered that in this extraction operation, Ni, It was discovered that Cr is not extracted and only a small amount of Zn is extracted, and by skillfully applying this phenomenon, the present invention was completed.

The distribution ratio when trivalent iron is extracted into a hydrochloric acid acidic solvent will of course vary depending on the hydrochloric acid concentration.

As the trialkyl phosphoric acid, for example, tributyl phosphate (hereinafter T
, B, P. ), it is desirable to keep the hydrochloric acid concentration in the etching waste liquid in the range of 1 to 2 N. If it is lower than this, it is difficult to extract iron efficiently, and if it is higher than this, it is difficult to dispose of the extraction residual liquid. Expenses will increase. When trialkyl phosphoric acid has a high concentration of hydrochloric acid, it is extracted at the same time, so a large amount of iron is used during back extraction, which is a problem especially in the case of multi-stage extraction.

Reverse extraction of iron from an extract containing hydrochloric acid is possible with just water, but a large amount of water is required to transfer the iron to the hydrated side with water alone, especially when using undiluted trialkyl phosphoric acid. When using , the amount of water increases.

This means that the recovered ferrous chloride solution becomes dilute, and there is a problem in that the number of stages of countercurrent multistage extraction increases in order to obtain a high concentration. Therefore, in the present invention, this problem was solved by adding not only water but also iron during back extraction of the extract containing hydrochloric acid. When iron is used in combination with water, hydrochloric acid reacts with iron to form iron chloride, and ferric chloride also reacts with iron to form ferrous chloride. divalent iron and 3
If hydrochloric acid does not coexist, the valent iron will migrate to the aqueous layer side, so the iron content can be efficiently recovered from the extract with a small amount of water, and a highly concentrated ferrous chloride aqueous solution can be obtained.

For example, it is possible to recover Fece2 as a saturated aqueous solution with a concentration of 40%. Describing the embodiments of the present invention in detail, first, as the etching waste liquid containing ferric chloride, which is the object of the present invention, waste liquid after etching stainless steel is particularly suitable, but waste liquid containing copper is also suitable. Can be applied. In that case, iron is added, copper is removed using the usual method, and chlorine is injected to convert the iron to ferric chloride. The iron concentration in the etching waste liquid is preferably as high as possible, for example, 30% or more as FeCl3, from the viewpoint of efficiency.
Hydrochloric acid is added to this solution to give a hydrochloric acid concentration of 1 to 2N. This hydrochloric acid is not limited to industrial use; cheap waste hydrochloric acid can also be used. As the trialkyl phosphoric acid which is an extraction solvent, T. B. P. is suitable.

Although it is possible to use a solvent such as chloroform or kerosene together with trialkyl phosphoric acid,
% is more advantageous because a solvent with a higher iron concentration can be obtained. Although a liquid ratio of organic layer to aqueous layer of 1/1 is sufficient, it may be less than 1/1 in order to increase the iron concentration in the solvent. When the liquid ratio is set to 1 or more, the iron concentration in the organic layer decreases, but on the other hand, the iron content of the extraction residual liquid decreases, and the iron recovery rate improves. When countercurrent multi-stage extraction is used for extraction with trialkyl phosphoric acid, the iron concentration in the organic layer is even higher, resulting in extraction residue. It is industrially advantageous because the concentration of the liquid is lowered and the iron recovery rate is improved, but two to three stages of countercurrent extraction are usually sufficient. Water and iron are added to the organic layer thus obtained, and both hydrochloric acid and ferric chloride are replaced with ferrous chloride, and back-extracted into the aqueous phase.

In this case, iron such as a piece of iron plate is sufficient, but
It is desirable to have a low content of impurities such as oil adhesion and heavy metals, and the amount thereof is preferably 1 to 1.1 times the theoretical amount required to convert hydrochloric acid and ferric chloride to ferrous chloride. Even if you start the operation at room temperature, the temperature will be 30~30℃ due to exothermic reaction.
The temperature will rise to about 40°C, but heating to about 60'C will speed up the reaction, and it is also good to stir with a pump and blades. When the reaction is completed, foaming ceases, and after filtering out insoluble matter from the liquid, it is separated into an organic layer and an aqueous layer. The amount of water used for back extraction may be appropriately determined depending on the FeCe3, Hce concentration in the organic layer or the desired ferrous chloride solution and concentration.
The ferrous chloride solution in the aqueous layer thus obtained has a concentration of approximately 30
All of the heavy metals such as Ni, Zn, and Cr that were present in the etching waste liquid have been removed and the concentration has reached ~40%.
It becomes 0 ppm or less. According to the present invention, the iron content in the etching waste liquid can be efficiently recovered as a highly concentrated ferrous chloride aqueous solution with few impurities through a simple operation.

Furthermore, by chlorinating the recovered aqueous solution, a ferric chloride aqueous solution containing less heavy metals can be obtained. Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. Example 1 Fece330%, Fece2O. l%, Hce7.3
% heavy metal salts ZnCf2, NiCe2, CrC'3 each 0
．． For 1000y of etching waste solution containing 4%,
T. as extractant. B. P. When extracted by adding lOOOf, the organic layer was 1270y'C-FeC'314.0%
, FeCl2O. 7%, HCI3. 1%, heavy metal salt Zn
A solution containing Ce2, NiC'2, and CrCe3 each of 10 ppm or less was obtained.

The water layer at this time was 730y, Fe3l7.2%, Fe
ce2O. 2%, Hce3.8%, heavy metal salt Znce2
, NiCe2, and crce were each 0.5%. 1000 fI of this organic layer, 50 y of iron (Dalai powder) and 40 y of water.
After adding Of, the reaction was carried out with stirring at 60° C. for 1 hour, and the mixture was filtered and separated to obtain an organic layer 817y and an aqueous layer 512g. Where the organic layer was analyzed Fece3l. 9% FeCl2O. 4% HceO. 1% Where the aqueous layer was analyzed FeCf3O. 2% Fece235. 1% HceO. It was 1%.

Example 2 T was added as an extractant to ferric chloride solutions 932y and Hce68y containing 30.0% of FeC'3, 20.1% of FeC'3, and 0.4% each of heavy metal salts ZnC'2, NiCe2, and CrC'3. ．． B. P. When 100y was added and countercurrent extraction was performed using 3 theoretical plates, the organic layer was 1327y'C'Fe.
ce3l8.9%, FeCl2O. 7%, HC'3.1
%, heavy metal salts Znce2, NlCe2, CrCe3 are each 10 ppm or less, and the aqueous layer is 643y'C'Fec
e36.2%, FeC'20.1%, HCI4.4%,
The heavy metal salts ZnCl)2, NiC'2, and CrC13 were each 0.5%.

1000y of this organic layer, 55y of iron (Dalai powder) and 5y of water
02y was added thereto, the reaction was carried out with stirring at 60°C for 1 hour, and the mixture was filtered and separated to obtain an organic layer 770V and an aqueous layer 767y.

Where the organic layer was analyzed Fece2l. 3% Face2O. 9% HceO. 3% Where the water layer was analyzed FeCf3O. l% Fece23O. O% HC′ 0.1% It was hot.

Comparative Example 1 Using the organic layer extracted by the method of Example 1, back extraction was performed in one stage in the same manner as in Example 1 using only water without using iron.The result was as follows.

Claims (1)

[Claims] 1. From a hydrochloric acid solution of ferric chloride etching waste containing a large amount of iron and a small amount of heavy metal components, iron content consisting of ferric chloride is extracted with hydrochloric acid using trialkyl phosphoric acid, and water and iron are added to the extracted liquid. A method for recovering iron from an etching waste solution, which comprises extracting highly concentrated ferrous chloride by adding ferrous chloride.