JP2678328B2 - Treatment method of monobasic acid waste liquid containing aluminum phosphate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of treating a monobasic acid waste liquid containing aluminum phosphate, recovering the monobasic acid and reusing it. INDUSTRIAL APPLICABILITY The present invention can be suitably applied to, for example, the production process of aluminum electrolytic capacitors and the treatment of waste liquid discharged from the chemical polishing process of aluminum.

[0002]

2. Description of the Related Art In the field of electrolytic foil industry, high quality aluminum electrode foil is produced by etching and chemical conversion processes. Etching is a process in which the surface of an aluminum foil is made uneven by the action of chemicals or electricity to increase the surface area. By this process, the electrostatic capacitance of the aluminum electrolytic capacitor is dramatically improved, and downsizing is possible. Chemical conversion is a technology to form an oxide film by electro-chemically treating the surface of aluminum foil that has undergone etching treatment.The thickness of this film determines the pressure resistance, and the delicacy is highly reliable and highly reliable. It has been decided to extend the service life. In recent years, it has been desired to improve capacitor performance such as downsizing of products, and in order to meet the demand, etching and chemical conversion treatment technologies have been further advanced. Along with this, the composition and concentration of the chemicals used are also complicated, and the composition of the waste liquid discharged from these processes is also complicated. A mixed acid obtained by adding phosphoric acid or sulfuric acid to a monobasic acid such as hydrochloric acid or nitric acid has come to be used, and it has become very difficult to treat the waste liquid.

Conventionally, the waste liquid discharged from the electrolytic foil industry-related factories producing aluminum electrolytic capacitors is
It was either discarded after the neutralization treatment or used at most as a coagulant in a paper mill. Since a large amount of alkali is consumed in the neutralization treatment of the waste liquid, not only the treatment cost becomes high, but also it is difficult to separate the aluminum hydroxide by-produced by the neutralization.

The present inventors have already proposed various methods for treating the waste liquid as described above. For example, as a treatment method of aluminum-containing waste hydrochloric acid, a method of adding sulfuric acid to a waste liquid to precipitate high-quality aluminum sulfate crystals to recover aluminum (JP-A 1-153517) or an oxalic acid solution containing aluminum As a treatment method, sulfuric acid is added to the waste liquid to recover oxalic acid (Japanese Patent Publication No. 55-3
No. 0697) is proposed.

[0005]

However, with the recent technological progress, as a new waste liquid problem, an effective treatment method of a monobasic acid waste liquid containing a non-volatile acid such as sulfuric acid or phosphoric acid is required. When a flocculant is produced from this kind of waste liquid as in the conventional case, not only the salt of the acid group of the monobasic acid and aluminum precipitates, but also the sulfate salt or phosphate salt of aluminum simultaneously precipitates. Since the whole was coagulated into a gel when it was allowed to cool to room temperature, its treatment was difficult.

Therefore, the present inventor efficiently removes and recycles aluminum metal ions, which are the main impurities contained in the monobasic acid waste liquid containing aluminum phosphate, which is generated in a large amount during the manufacturing process of aluminum electrolytic capacitors. The research on the method of regenerating possible monobasic acid aqueous solution was carried out. Efficient removal of aluminum is indispensable in order to make the monobasic acid waste liquid containing aluminum phosphate recyclable. However, if the waste solution is simply subjected to diffusion dialysis as it is, the recovery rate of the monobasic acid contained in the waste solution is low and the removal rate of aluminum is also poor. However, surprisingly, when the waste liquid is concentrated and phosphoric acid is added and then diffusion dialysis is performed, the monobasic acid is very efficiently treated by 70% to 95% as compared with the case where the monobasic acid is directly subjected to diffusion dialysis.
It has been found that since it is also possible to recover, a recyclable monobasic acid aqueous solution can be regenerated and aluminum phosphate can also be efficiently recovered.
The present invention is based on these findings.

[0007]

Accordingly, the present invention comprises the steps of concentrating a monobasic acid waste liquor containing aluminum phosphate, and adding phosphoric acid to said monobasic acid waste liquor containing aluminum phosphate. The present invention relates to a method for treating a monobasic acid waste liquid containing aluminum phosphate, which comprises performing a diffusion dialysis treatment.

The waste liquid to be treated by the method of the present invention is not particularly limited as long as it is a waste liquid produced by performing aluminum metal treatment with a treatment liquid containing a monobasic acid and phosphoric acid as main components. This is a large amount of waste liquid generated from the manufacturing process of aluminum electrolytic capacitors and the chemical polishing process of aluminum. In addition to containing monobasic acid and phosphoric acid, and their aluminum salts in the waste liquid,
It may contain various other inorganic acids (for example, sulfuric acid). The monobasic acid referred to here is an acid in which one molecule of acid is ionized to release one hydrogen ion, and particularly hydrochloric acid or nitric acid.

The concentration step adjusts the concentrations of monobasic acid and aluminum in the waste liquid. The dialysis coefficient of an acid varies depending on its concentration and type, and the recovery capacity of the target acid by diffusion dialysis treatment also varies. Although depending on the dialysis membrane used, for example, with hydrochloric acid or nitric acid, the dialysis coefficient increases when the concentration is about 2N to 6N. Therefore, the waste liquid is concentrated to a concentration that maximizes the dialysis coefficient of the monobasic acid that is contained in the waste acid to be treated and that is to be recovered. In the concentration step when adjusting the concentration, the aluminum concentration is preferably 30 to 60 g / liter. When the aluminum concentration is less than 30 g / liter, the dialysis efficiency is deteriorated, which is not preferable, and when it exceeds 60 g / liter, aluminum salt crystals are likely to be deposited, which causes clogging of the dialysis membrane and leakage of aluminum during the diffusion dialysis treatment. Is more likely to occur. The concentration operation can be carried out by evaporative concentration under reduced pressure, for example.

Since almost no free monobasic acid is present in the waste liquor, phosphoric acid is added to replace the aluminum salt consisting of the acid group of the monobasic acid with aluminum phosphate, and the free monobasic acid generated by this is replaced. Collect by diffusion dialysis treatment. Since the added phosphoric acid has a lower dialysis coefficient than that of the monobasic acid, it does not hinder the dialysis of the monobasic acid, and since it is one component of the etching solution, etc., it can be added to the waste solution.
There is an advantage that unnecessary impurities will not be added to the treatment liquid after regeneration. It is preferable to adjust the PO ₄ / Al molar ratio to a ratio of 1 to 5, preferably 1.1 to 2 by adding phosphoric acid. When the molar ratio of PO ₄ / Al is less than 1 or exceeds 5, aluminum salt crystals are likely to precipitate in the apparatus due to the decrease of the monobasic acid during the diffusion dialysis treatment for recovering the monobasic acid.

The order of the concentration step and the phosphoric acid addition step is arbitrary, and the concentration step may be performed first and then the phosphoric acid addition step, or vice versa. Next, the waste liquid that has been subjected to the concentration treatment and the phosphoric acid addition treatment is subjected to diffusion dialysis treatment using an anion exchange membrane. The anion exchange membrane used here is not particularly limited, but a membrane that selectively permeates free monobasic acid and hardly permeates metal ions and phosphate ions is desirable.

The diffusion dialysis treatment is performed according to a conventional method. For example, it is carried out by using a diffusion dialysis tank configured in a filter press type in which a large number of anion exchange membranes are arranged, and circulating the waste liquid and water countercurrently through the anion exchange membranes.
The supply rate of waste liquid and water is not particularly limited, but is 0.5 to 3
It may be supplied at a rate of about 1 liter / hr · m ² . Since the anion exchange membrane has the property of not permeating cations other than hydrogen ions, the acid (that is, hydrochloric acid or nitric acid) diffuses from the waste liquid side to the water side due to the difference in concentration between the waste liquid and water, and the acid liquid (recovered) Acid) is obtained, while free acid is removed on the waste liquid side to form a dialysis waste liquid.

Next, the dialysis waste liquid obtained by the above diffusion dialysis treatment is evaporated and concentrated by a decompression method so that the PO ₄ ion concentration becomes 500 g / liter or more, and free monobasic acid is distilled and recovered together with water. Further, the dialysis waste liquid obtained by removing the monobasic acid again in this manner is a phosphoric acid-rich solution. Since the solubility of aluminum phosphate in the phosphoric acid aqueous solution decreases in correlation with the decrease in phosphoric acid concentration, aluminum phosphate can be easily separated by precipitation by diluting the phosphoric acid-rich aqueous solution with water.

[0014]

EXAMPLES The present invention will be described below in more detail with reference to examples, but these examples do not limit the scope of the present invention. Example 1 18 liters of waste nitric acid obtained by etching an aluminum foil (15.9 g / liter as Al, 1 as PO ₄
2.2 g / liter and 121.5 g / liter as NO ₃ ) were evaporated and concentrated to about 1/3 by a reduced pressure method (30 mmHg). Next, about 1.64 kg of 75% by weight phosphoric acid was added to the mixture, 40.7 g / liter of Al and 199.0 g / liter of PO ₄ were added.
About 7 liters of a solution of 311.2 g / liter of NO ₃ was obtained.

Next, a diffusion dialysis treatment was carried out at room temperature using the solution. For the diffusion dialysis treatment, a filter press type diffusion dialysis tank provided with 19 sheets of anion exchange membranes (effective area: 0.397 m ² ) was used, and the waste liquid and water were supplied in countercurrent. The test was carried out for 20 hours at a waste liquid supply rate of 230 ml / hr and a water supply rate of 500 ml / hr. as a result,
7.36 liters of recovered acid (0.6 g / liter as Al, 10.1 g / liter as PO ₄ , 136.6 g / liter as NO ₃ ), dialysis waste liquid 7.24 liters (25.2 g / liter as Al, PO ₄ as 11
6.1 g / liter and NO ₃ as 58.8 g / liter) were obtained. The recovery rate of nitric acid was 70%.

7.24 liters of the dialysis waste solution was evaporated and concentrated to a PO ₄ concentration of 600 g / liter by a depressurization method, nitric acid was recovered by evaporation together with water, and then 8 liters of water was added to precipitate aluminum phosphate. Then, separation filtration was performed to recover about 730 g of aluminum phosphate.

Example 2 10 liters of waste nitric acid obtained by etching an aluminum foil (14.5 g / liter as Al, 1 as PO ₄
840 g of 75 wt% phosphoric acid was added to 0 g / liter and 108 g / liter as NO ₃ ), and subsequently evaporated and concentrated to about 1/3 by a reduced pressure method (30 mmHg) to obtain 41.2 g / liter of Al and PO. ₄ is 201 g / liter,
About 3.5 liters of a solution consisting of 308 g / liter of NO ₃ was obtained.

Next, the solution was subjected to a diffusion dialysis treatment at room temperature using the same apparatus as in Example 1. The test was carried out for 10 hours with the waste liquid supply rate set to 200 ml / hr and the water supply rate set to 600 ml / hr. As a result, the recovered acid was 4.62 liters (0.5 g / liter as Al and 6.7 as PO _4).
g / liter, NO ₃ as 98.4 g / liter),
A dialysis waste liquid of 3.35 liters (23.9 g / liter as Al, 110 g / liter as PO ₄ , and 48.1 g / liter as NO ₃ ) was obtained. Recovery rate of nitric acid is 73
%Met.

3.35 liters of the dialysis waste liquid was evaporated and concentrated to a PO ₄ concentration of 600 g / liter by a reduced pressure method, nitric acid was recovered by evaporation together with water, and then 4 liters of water was added to precipitate aluminum phosphate. Then, separation filtration was performed to recover about 330 g of aluminum phosphate.

Example 3 9 liters of waste hydrochloric acid obtained by etching an aluminum foil (11.0 g / liter as Al, 1 as PO ₄
1.5 g / liter, 118 g / liter as Cl)
Was concentrated to about 1/3 by vacuum method (30 mmHg),
Subsequently, about 440 g of 75% by weight phosphoric acid was added, and the Al content was 3%.
A solution of 0.1 g / liter, 131.2 g / liter of PO ₄ , and 323.7 g / liter of Cl about 3.
2 liters were obtained.

Next, using the same apparatus as in Example 1, the solution was subjected to diffusion dialysis treatment at room temperature. The test was conducted for 10 hours with the waste liquid supply rate set to 240 ml / hr and the water supply rate set to 510 ml / hr. As a result, the recovery acid 3.8 l (Al as 0.6 g / l, as PO ₄ 10.
2 g / liter, Cl 184.0 g / liter), dialysis waste liquid 3.7 liter (Al 18.9 g)
/ Liter, as PO ₄ 74.6 g / liter, Cl
20.9 g / liter) was obtained. The recovery rate of hydrochloric acid was 90%.

3.7 liters of the above dialysis waste liquid was evaporated and concentrated to a PO ₄ concentration of 600 g / liter by a reduced pressure method,
Nitric acid was recovered by evaporation together with water, and then 4 liters of water was added to precipitate aluminum phosphate. Then, separation filtration was performed to recover about 250 g of aluminum phosphate.

[0023]

According to the method of the present invention, a monobasic acid having a small amount of metal impurities can be efficiently recovered and recycled from a monobasic acid waste liquid containing aluminum phosphate, which is extremely effective in preventing pollution. . In addition, aluminum phosphate can be recovered as a by-product, which can be effectively used.

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Claims (4)

(57) [Claims] 1. A diffusion dialysis treatment is carried out after the step of concentrating the monobasic acid waste liquid containing aluminum phosphate and the step of adding phosphoric acid to the monobasic acid waste liquid containing aluminum phosphate. A method for treating a monobasic acid waste liquid containing aluminum phosphate. 2. The aluminum concentration in the concentration step is 30.
The method according to claim 1, wherein the method is -60 g / liter. 3. The method according to claim 1, wherein the PO ₄ / Al molar ratio is adjusted to 1 to 5 in the phosphoric acid addition step. 4. After recovering the monobasic acid solution by the diffusion dialysis treatment, the permeation liquid is concentrated to collect and remove the monobasic acid remaining in the permeation liquid, and water is added to the residual liquid. The method according to any one of claims 1 to 3, wherein the aluminum phosphate that precipitates and precipitates is separated and the residual phosphoric acid is recovered.