JPH06170366A - Method for treating waste cleaning liquid - Google Patents

Abstract

PURPOSE:To obtain an economical method for treating RO by blending a waste organic acid cleaning liquid and a copper removal rust inhibiting liquid together. CONSTITUTION:In a method for treating a waste cleaning liquid by which to blend a waste organic acid cleaning liquid containing carboxylic acid and a reducing agent for enhancing cleaning effects with a copper removal rust inhibiting liquid 2, and adjust the pH value of treatment using a reverse osmosis membrane, the waste organic acid cleaning liquid 1 or a combination of the waste organic acid cleaning liquid 1 and the copper removal rust inhibiting liquid 2 are oxidized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating cleaning waste liquid, and more particularly to a method for treating chemical cleaning waste liquid for boilers, heat exchangers, tanks and the like.

[0002]

2. Description of the Related Art After cleaning an object to be cleaned, which has scales mainly composed of iron oxide, with an organic acid, it is washed with water and then metal copper, which is hardly removable by the acid cleaning, is removed to remove the metal of the object to be cleaned. In many cases, copper removal and anticorrosion treatment are performed to stabilize the surface. After the cleaning is completed, COD, heavy metals and NH ₃ contained in the waste liquid must be treated, but in recent years, a reverse osmosis membrane (hereinafter referred to as RO) treatment, which is reliable and easy to perform, has been applied. Many.

In this case, the pH is adjusted to 5 to 6, preferably 5.5 to 6 in order to increase the dissociation degree of the lower carboxylic acid in the organic acid cleaning waste liquid for the purpose of increasing the RO treatment efficiency. However, when the organic acid cleaning waste liquid is mixed with the copper removal rust preventive solution, the reducing agent contained in the organic acid cleaning solution releases copper in the copper remover rust preventive solution, so both solutions should be received in separate tanks. I had to. As a result, in the conventional waste liquid treatment, the acid waste liquid and the copper removal anticorrosion liquid are separately received in two waste liquid tanks, the pH of the acid waste liquid is adjusted to 5 to 6, and the copper removal anticorrosion liquid does not release copper. After the addition of the chelating agent, in order to improve the NH ₃ removal efficiency, it was necessary to adjust the pH to 5 to 7 and perform the RO treatment for the same reason.

[0004]

As described above, in the prior art, the organic acid cleaning waste liquid and the copper removal anticorrosion liquid must be separately pH-adjusted for RO treatment, which is uneconomical. there were. SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned problems of the prior art and provide an economical method capable of performing RO treatment by mixing an organic acid cleaning waste liquid and a copper removal anticorrosive liquid together.

[0005]

In order to solve the above problems, in the present invention, an organic acid cleaning waste liquid containing a carboxylic acid and a reducing agent for enhancing the cleaning effect is mixed with a copper removing anticorrosive liquid. In the method for treating a cleaning waste liquid in which the pH is adjusted to perform reverse osmosis membrane treatment, the organic acid cleaning waste liquid, or the cleaning waste liquid after mixing the organic acid cleaning waste liquid and the copper removal anticorrosive liquid, is oxidized. It is what In the above method, the carboxylic acid has a low degree of dissociation of the carboxyl group, has a high permeability of the semipermeable membrane at a pH of 4 or less, and has a permeability of 5 in the RO treatment.
More than% monocarboxylic or dicarboxylic acids can be used.

As described above, in the present invention, after the pickling waste liquid is received in the waste liquid tank and before or after receiving the copper removal anticorrosive liquid, Fe ²⁺ contained in the waste liquid is oxidized to Fe ^3+. This makes it possible to receive both waste liquids in one waste liquid tank. FIG. 1 shows a process chart of the present invention, and description will be made based on this. First, the acid cleaning waste liquid 1 is introduced into the waste liquid tank, and then the copper removal rust preventive liquid 2 is introduced. At this time, it is preferable that the oxidation treatments 3 and 3'be performed after the acid cleaning waste liquid 1 is introduced or after the copper removal anticorrosive liquid 2 is introduced. Then, the pH is adjusted to 5 to 6 and then the RO treatment 5 is performed to perform the waste liquid treatment.

[0007]

In the present invention, since an acidic cleaning solution and an alkaline copper removing anticorrosive solution are mixed and treated, the pH of each is conventionally changed.
By reducing the amount of acid and alkali consumed for adjustment, the injection of extra salt is reduced and the concentration rate in RO treatment is increased. In addition, since it is not necessary to add an expensive chelating agent, which is conventionally required, the amount of chemicals required for the treatment is reduced. The oxidizing agent that oxidizes Fe ²⁺ to Fe ³⁺ does not have to be particularly limited, but in order not to impose a load on the subsequent RO treatment, increase the salt concentration of air, oxygen, ozone, hydrogen peroxide, etc. Those that do not do are desirable.

[0008]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 An experiment was conducted in which a pickling waste liquid A having the composition shown in Table 1 below and a copper removal anticorrosive liquid B were mixed and treated.

[0009]

[Table 1]

The results were as follows. (A), the pickling waste liquid (A) having the composition shown in Table 1 and the copper removal anticorrosive liquid (B) (hereinafter (A) liquid (B) liquid) are mixed at a ratio of 2: 1 and p
When H5.5 to 6 was adjusted, copper was immediately released. When the liquids of (b) and (a) were oxidized by air oxidation, copper was dissolved again. (C) When liquid (A) which had been air-oxidized in advance was operated in the same manner as in (a), liberation of copper did not occur.

The operations of (d), (b) and (c) were carried out by using Fe ²⁺ and hydrogen peroxide solution (35% H ₂ O ₂ , 1.8 ml) necessary for oxidizing sodium erythorbate. The copper melted as a result. (E), (A) solution pH, when mixed with (B) solution
Adjust in advance so as to be 5.5 to 6 (b) to
After the treatment by the oxidizing means shown in (d), when mixed, copper was dissolved. Copper was dissolved by such an oxidation treatment.

Next, the waste liquid was treated as follows according to the flow shown in FIG. After liquid A is air-oxidized, liquid B is mixed. The ratio at that time was A: B = 2: 1. This solution was adjusted to pH 5.5 with sodium hydroxide and then subjected to RO treatment. As a comparative example, solution A and solution B were individually pH-adjusted and subjected to RO treatment. In this case, the solution A is adjusted to pH 5.5 with NaOH,
Before neutralizing the solution B, EDTA was added as a chelating agent to a concentration of 830 mg / liter, which is a slight excess equivalent to copper ions, and then the pH was adjusted to 7.0 with sulfuric acid and subjected to RO treatment. The results are shown in Table 2.

[0013]

[Table 2]

Concentration rate = Raw water liquid amount / Concentrated water liquid amount Concentration ratio of the conventional method: 400 + 200/54 + 25 =
7.6 Concentration rate of the present invention: 600/75 = 8.0 As is clear from Table 2, the RO treatment according to the present invention is performed by mixing two liquids in terms of the property of the permeated liquid as compared with the result obtained by the conventional method. Despite this, almost no change was observed and the concentration rate was also improved.

[0015]

According to the present invention, the waste liquid receiving tank can be changed from the conventional two tanks to one tank, and the amount of the pH adjuster used is reduced. Furthermore, the addition of the chelating agent, which was conventionally required, is no longer necessary.

[Brief description of drawings]

FIG. 1 is a process drawing showing a processing method of the present invention.

[Explanation of symbols]

1: Acid cleaning waste liquid, 2: Copper removal rust preventive liquid, 3 ': Oxidation treatment, 4: pH adjustment, 5: RO treatment

Claims (1)

[Claims] 1. A method for treating a cleaning waste liquid, which comprises mixing an organic acid cleaning waste liquid containing a carboxylic acid and a reducing agent for enhancing the cleaning effect with a copper removal rust preventive solution and adjusting the pH to perform reverse osmosis membrane treatment. 3. The method for treating a cleaning waste liquid, comprising oxidizing the organic acid cleaning waste liquid or the cleaning waste liquid after mixing the organic acid cleaning waste liquid and the copper removal anticorrosive liquid.