CN1116448C - Method for treating waste liquor from final water washing tank used in cation electrodeposition painting - Google Patents

Abstract

This invention aims at providing a method of treating a waste liquor from a final water washing tank used in the cation electrodeposition painting, which method is capable of reutilizing the waste liquor as final water washing water by recovering the waste liquor without discarding the same. A method of treating a waste liquor from a final water washing tank, characterized by the steps of separating the waste liquor, which is discharged from the final water washing tank, into a raw painting material-containing condensed liquid and a filtrate by using a semi-permeable membrane while maintaining the waste liquor pH not higher than 6.4 at all times in a condensation tank, returning the whole or a part of the filtrate to the final water washing tank, and reusing this filtrate as final water washing cleaning water.

Description

Treatment method of final washing tank waste liquid in cationic electrodeposition painting

                      

The invention relates to a treatment method for the waste liquid of the final washing tank in cationic electrodeposition painting.

Background technique

Electrodeposition painting is widely used because of its easy management and economical features, and the technological progress is also remarkable. Among them, it has only been a little over 15 years since the transition from anionic electrodeposition coatings to cationic electrodeposition coatings. Especially in the automotive field, almost 100% of cationic electrodeposition coatings are used today. Cationic electrodeposition coating is not limited to the automotive field, but is also entering a wide range of fields such as building materials, general metal products, electrical products, and industrial machinery.

The background leading to the development of cationic electrodeposition paints that are so suitable for painting automobiles and the like is the development of cationic electrodeposition paints excellent in ultrafiltration (UF) characteristics, the development of ultrafiltration membranes suitable for cationic electrodeposition paints, and Development of an ultrafiltration system combining these.

In such cationic electrodeposition painting systems that have been developed subsequently, a washing process is provided after electrodeposition of the object to be coated. That is, the undried coating film electrodeposited by the object to be coated in the electrodeposition tank is finished by drying and baking in a drying oven, but the coating film lifted from the electrodeposition tank is attached with the paint in the tank. , negatively charged counterions, etc. If it is dried and baked as it is, processing defects such as hanging, flowing, ringing, pitting, etc. will occur. In order to avoid this situation, the general electrodeposition paint system is to go through the washing process after electrodeposition and then dry-bake.

The washing process after electrodeposition is divided into filtering the washing waste liquid containing a large amount of electrodeposition tank liquid or paint, returning the recovered liquid containing paint components to the electrodeposition tank, and returning the filtrate as washing water to be recycled and reused separately. The loop water washing process, and the second process of the final water washing process provided separately as a subsequent process. The former uses the filtrate treated by ultrafiltration of the paint in the electrodeposition tank to wash the coated object, so the paint components attached to the coated object can be recovered and washed with water. The latter is an extremely important process for deep washing. The current situation is to use pure water, industrial water, tap water and other water for fine washing to wash away the rare paint components or counter ions that the former could not wash off, and the washing waste liquid is discharged. outside the system.

However, the amount of water required for this final washing is extremely large, and this washing waste liquid also contains a small amount of paint or impurity ions, which are not allowed to be discharged to the outside. No matter from an environmental point of view or an economic point of view, final washing waste liquid is required special treatment techniques.

However, this final washing process waste liquid hardly contains organic acid or dissolution aid, and since it is mostly water, it is in a state where a small amount of paint components contained is easy to precipitate. Therefore, this kind of washing wastewater can be purified and reused by membrane treatment, but it is difficult to carry out due to problems such as agglutination and clogging of membrane pores in the membrane treatment device, and it cannot be put into practical use.

The technique of reusing the waste liquid of the final washing process without discarding it has been disclosed in JP-A-7-207495. This gazette discloses that in a washing process that relies on pure water as the final washing process, an ultrafiltration filtrate obtained by ultrafiltration of washing water is used as the final washing water. However, this publication does not mention the ultrafiltration treatment conditions, especially the strategy of continuing the ultrafiltration stably for a long time, nor does it describe that pH adjustment can achieve stable ultrafiltration.

Invention Disclosure

The present invention aims at the difficulty of waste liquid treatment as described above, so that the waste liquid of the final washing process can be processed without agglomeration and blockage of membrane pores in the membrane treatment device, and the paint residue remaining in the waste liquid is concentrated to achieve While it is in a state where it is easy to discard, it refines a large amount of washing wastewater to a state where it can be reused as washing water, making it a closed system that does not drain to the outside at all, or providing a technology that can refine it to a drainable state.

The present invention relates to the treatment method of the waste liquid of the final washing tank, which is characterized in that, in the treatment method of the waste liquid discharged from the final washing tank of the cationic electrodeposition painting process, the pH of the waste liquid in the concentration tank 6 is always kept below 6.4, by making This waste liquid is circulated in the filter unit 9 equipped with a semipermeable membrane, and it is separated into a concentrate containing paint components and a filtrate.

The terms such as the final washing tank or the final washing process in this specification refer to the washing tank used in the final finishing washing that is set independently from the so-called closed circuit composed of the electrodeposition tank and the washing tank generally used in the electrodeposition painting process or washing process.

The present invention is characterized in that all or part of the filtrate separated by the semipermeable membrane is returned to the final washing tank.

The present invention is also characterized in that the concentrate is drawn out from the concentrate tank at the stage when the concentration of the concentrate in the concentrate tank for circulating waste liquid reaches a maximum of 200 times.

Another aspect of the present invention relates to the treatment method of the waste liquid of the final washing tank, which is characterized in that the waste liquid discharged from the final washing tank of the cationic electrodeposition painting process is separated into In the final washing tank waste treatment of the concentrate and filtrate of paint components, the semipermeable membrane is backwashed with the filtrate added with 300-3,000ppm of organic acid, so that the pH of the concentrate in the concentration tank is always kept below 6.4.

In the cationic electrodeposition painting process, the pH of the water in the final washing process is usually around 6.0-7.0. The amount of paint carried out is about 0.05-0.2% (weight) in the water after washing, and the pH rises to about 6.5-7.0. If it is sent into the membrane treatment device as it is, the paint particles will usually agglomerate and precipitate on the filter membrane. In order to prevent this from happening, the present invention adjusts the pH of the water in the concentration tank 6 to below 6.4, preferably below 6.0, and more preferably 4.5 to 6.0, and then sends it into a semi-permeable membrane, especially an ultrafiltration membrane. filter unit 9. In this way, the pH of the washing waste liquid is simply adjusted to below 6.4, and the paint in the waste liquid can exist stably even under the pressure or shear conditions in the membrane treatment device, and will not coagulate in the device and block the membrane pores And so on. The concentrated solution obtained by membrane treatment in this way can be continuously concentrated through the membrane, and can be concentrated to a volume ratio of about 400 times. At this time, troubles such as aggregation and clogging of membrane pores will not occur.

Moreover, the filtrate can be completely recovered and returned to the final washing tank as the final washing water for recycling and reuse. Therefore, the washing waste liquid can not be discharged to the outside, and a substantially complete closed circuit can be achieved. In addition, this filtrate can also be discharged outside in whole or in part without worrying about environmental pollution. When this filtrate is used as a part of the final wash water, it is surprising that even if it is used in this way, it does not form so-called pitting of paint fine bumps on the object to be coated and stain the coating film.

On the other hand, when the concentrated circulating concentrated liquid is processed in the filtering device 9 equipped with a semi-permeable membrane, the concentration of other solid components except the paint components will gradually increase, and the concentration of the concentrated liquid in the concentration tank reaches the highest 200 times The stage should be withdrawn from the thickening tank. The extracted concentrated liquid is small and can be further concentrated if necessary so that it can be safely incinerated. Furthermore, if it is kept stably as a solution, it can be returned to the electrodeposition tank, which is economically more advantageous.

The above concentration refers to the rate of change based on the initial state of operation, and can be expressed by volume ratio, non-volatile matter concentration ratio, conductive substance content ratio, etc., and is expressed by volume ratio in this specification. The volume ratio is defined as the ratio of the total volume of waste liquid sent to the concentration tank for treatment to the volume of the remaining concentrated liquid in the concentration tank.

It is difficult to adjust the pH in the concentration tank at the beginning of operation, so a certain amount of washing waste liquid should be stored in the concentration tank, and the pH of the liquid in the concentration tank should be adjusted to below 6.0 at the beginning of operation until the circulation through the filter device starts. , preferably 4.5 to 5.5.

In order to stabilize the filtration capacity of a filter unit equipped with a semipermeable membrane, the filter unit can also be backwashed (backwashed) with acid. Backwashing is carried out periodically with the filtrate added with about 300-3,000ppm of organic acid, so that the pH in the concentration tank can be kept below 6.4.

The final washing tank can be either a single tank or a multi-stage type with 2 to 3 tanks cascaded. In the case of multi-stage, the washing water is preferably in the opposite direction to the direction of the object to be coated, that is, the washing water flows from the last tank to the first tank for countercurrent washing. In this case, the washing waste liquid is discharged from the first tank, and the filtrate from the filter device can be used to directly wash the coated object in the last tank of the final washing tank, or can be returned to the last tank of the final washing tank. in the slot.

Semipermeable membranes are reverse osmosis (RO) membranes, ultrafiltration (UF) membranes, precision filtration (MF) membranes, etc., but ultrafiltration membranes are best used for waste liquid filtration. The reverse osmosis membrane is excellent in the ability to remove paint components, but the processing capacity per unit time is small, and the economy is not good. On the contrary, membranes with a pore size above ultrafiltration, such as precision filtration membranes, have excellent membrane processing capabilities but a large amount of coating components enter the filtrate, which cannot meet the drainage water quality standards required for drainage. When the filtrate is reused as the final washing water, the washing effect is poor. There is a problem of staining the coating film by forming so-called pockmarks of fine bumps of paint on the object to be coated. From the comprehensive point of view of the processing capacity and the components in the filtrate, the ultrafiltration membrane is no problem in practical application. The ultrafiltration membrane can be a membrane with a molecular weight ranging from 3,000 to 1,000,000 and made of any material such as polyacrylonitrile, polystyrene, polyolefin and its chemical modification. The applicability of the material, molecular weight range, etc. varies with the conditions of the liquid to be treated, so it is best to research and select in advance.

When it is necessary to obtain a filtrate closer to pure water, the ultrafiltration filtrate can also be subjected to reverse osmosis treatment as shown in Figure 10. In this way, water with a lower BOD can be obtained.

The pH of the wastewater discharged from the final washing tank in cationic electrodeposition painting is about 6.5 to 7 as described above. Therefore, in the present invention, acid is used to adjust the pH of the concentration tank to 6.4 or less. Suitable acids are organic acids, such as carboxylic acids, sulfonic acids, sulfates, phosphates, phenols, etc., but water-soluble carboxylic acids are particularly preferred. Specifically, formic acid, acetic acid, propionic acid, butyric acid, lactic acid, citric acid, maleic acid, fumaric acid, oxalic acid, malic acid, tartaric acid, oxaloacetic acid, malonic acid, nitrilotriacetic acid, Phthalic acid, trimellitic acid, and inorganic acids such as sulfamic acid, carbonic acid, etc. Particularly preferred are formic acid, acetic acid, lactic acid and the like. Electrode solution discharged from the diaphragm unit can also be used. That is to say, the diaphragm device discharges the anions such as acid in the free paint by electrodeposition as anolyte out of the electrodeposition tank through the ion exchange membrane device arranged in the electrodeposition tank, which can be used to adjust pH.

In the waste liquid treatment of the final washing tank of the present invention, there is no hindrance to installing an appropriate pre-filter before the semi-permeable membrane.

In order to make the above description easier to understand, the present invention will be described below with reference to FIG. 1 .

In cationic electrodeposition painting, the object 18 suspended on the conveyor 17 moves continuously, and first enters the electrodeposition tank 1 . The object to be coated 18 after electro-deposition painting is then run sequentially along the three-stage ultrafiltration filtrate recovery water washing process line composed of the first water washing tank 2 , the second water washing tank 3 and the third water washing tank 4 . In the ultrafiltration filtrate recovery water washing process, the coating liquid in the electrodeposition tank 1 is filtered by the ultrafiltration device 8, and the filtrate obtained enters from the third washing tank 4, and flows to the second washing tank 3 along the countercurrent direction with the object to be coated. The first water washing tank 2 is then returned to the electrodeposition tank, and the uncoated paint is recovered while washing the object to be coated. In each washing tank, the lotion in the tank is sprayed on the coated object and circulated, and the excess washing liquid overflows and is sent to the previous level of washing tank.

The object to be coated leaving the third washing tank 4 is further washed with pure water, industrial water, tap water, etc. in the final washing tank 5, and then sent to the drying and baking process.

The present invention is implemented at the final washing tank 5 in the final washing process of the above general paint-washing process. For ease of understanding, the process of performing membrane treatment on the wastewater discharged ^* from this washing tank 5 will be described below. In this final washing tank 5, the washing water in the tank 5 is polluted due to paint components, foreign ions, etc. brought in from the previous process together with the object 18 to be coated. The polluted washing liquid cannot be used as the final washing water, nor can it be discarded just like this, but it is pumped out and sent to the concentration tank 6, and then the mixed substances are separated and removed in the following manner. Add acid to the washing waste liquid extracted from the concentration tank 6 to adjust the pH to below 6.4, and then send it to the membrane treatment device 9 for treatment. The concentrated solution can be further circulated through the membrane treatment device 9 to concentrate to about 400 times the volume ratio. The filtrate is collected in the filtrate tank 7, and all or a part of it can be returned to such as the washing tank 5, or directly reused as the coating spray liquid. In addition, the filtrate entering the filtrate tank 7 can also be further filtered through the reverse osmosis treatment device 10 and reused. On the other hand, the concentrated solution produced by the membrane processing device 9 can also be extracted from the concentration tank when the concentration of the concentrate in the concentration tank reaches a maximum of 200 times as described in detail above.

Fig. 2 illustrates a final washing tank waste liquid treatment method in the case where the final washing tank is composed of multiple tanks (three tanks are drawn in the figure as an example). In the previous process, the object to be coated by electrodeposition painting and washing first enters the first tank of this final washing tank. The coated object after washing then enters the second tank and the third tank sequentially, and on the other hand, the washing water is transported from the last tank to the first tank along the countercurrent direction. The filtrate that comes out from membrane treatment device 9 or 10 enters the 3rd groove (24 of Fig. 2) (or enters the 3rd groove after directly washing the object to be coated, overflows after repeated washing is sent from the second groove The washing waste liquid enters the second groove (23 of Fig. 2), repeats the coated object sent from the first groove (22 of Fig. 2) here equally. Like this, the waste liquid of each groove all overflows to the front respectively In one tank, the waste liquid discharged from the initial tank (22 in Fig. 2) is introduced into the concentration tank, and at least a part of the filtrate is returned to the last tank of the final washing tank through the filtering device.

The filtrate after membrane treatment in Fig. 2 is returned to the last tank (24 in Fig. 2) of the final water washing tank, but in the case of final washing with pure water, the filtrate may not return to the last tank, but return in front of it The groove (for example 22,23 of Fig. 2), on the 3rd groove, import pure water to wash.

A brief description of the attached drawings

Fig. 1 is a flow chart illustrating the flow of waste liquid treatment of the final washing tank in the electrodeposition painting process.

Fig. 2 is a flow chart of final washing waste liquid treatment using multi-stage (taking the case of three tanks as an example) final washing tanks.

The meanings of the codes in the figure are as follows:

1. Electrodeposition tank; 2. First washing tank; 3. Second washing tank; 4. Third washing tank; 5. Final washing tank; 6. Concentrating tank; 7. Filtrate tank; 8. Ultrafiltration device; 9 .Filtration device equipped with a semi-permeable membrane; 10. Reverse osmosis device; 11, 12, 13, 14, 15, 16 represent pumps; 17. Conveyor; 18. Object to be coated; 19. Spray device for washing; 20 . Concentrate; 21. Filtrate; 22. First tank of final washing tank; 23. Second tank of final washing tank; 24. Third tank of final washing tank.

Invention Examples

The following examples illustrate the present invention.

In the following examples, the so-called non-volatile components in the concentrated solution refer to the residual components when the concentrated solution is dried at 110° C. to reach a constant weight.

Example 1

The cationic electrodeposition paint (manufactured by Nippon Paint Co., Ltd.: パワ-トップ (registered trademark) U-2500) managed with NV (non-volatile component concentration) = 20% by weight, pH = 6.5, and MEQ = 25 was placed in a 10 m tank. Under the conditions of liquid temperature = 28°C, CV (painting voltage) = 250V, and energization time = 2 to 3 minutes, the electrodeposition coating is carried out, and the ultrafiltration recovery water is used for three stages of washing, and the final water washing stage is used for online water washing. The coated object after ultrafiltration recovery and washing is washed with pure water with a conductivity of 2 μs/cm in the final washing tank, but due to the coating components brought in at this time, the waste liquid of the final washing tank becomes NV=0.1% pH=6.5.

This waste liquid was introduced into a concentration tank, adjusted to pH = 5.0 with acetic acid, and then supplied to a filtration device equipped with an ultrafiltration membrane (manufactured by Asahi Kasei Industries, Ltd., Micro-Z (registered trademark) KCV3010) for filtration.

The filtering conditions at this time are: inlet pressure=2.5kg/cm, outlet pressure=0.5kg/cm.

The amount of filtrate was 12 l/min at the initial stage and 6 l/min after 100-fold concentration, showing excellent filtration stability.

When the waste liquid supplied for filtration is 5000 l, 4950 l of filtrate and 50 l of concentrated liquid are obtained by supplying ultrafiltration membrane, and the concentrated liquid is pumped into other containers.

The filtrate was NV=0.04%, pH=5.2, and the concentrate was NV=6.2%, pH=6.3.

This filtrate was returned to the final washing tank and used as a substitute for pure water. The washing effect was good, and the result of the redissolution test of the coated object was not problematic.

The concentrated liquid pumped into other containers should be evaporated to dryness and then incinerated.

Furthermore, despite reusing the filtrate in continued repeat trials, the operation was extremely stable and continued without trouble after 6 months.

Example 2

The waste liquid discharged from the pure water washing tank used in Example 1 was adjusted to pH=5.0 with the polar liquid (the main component is about 0.05% acetic acid) of the electrodeposition tank, and then supplied to an ultrafiltration membrane (manufactured by Asahi Kasei Industries, Ltd., Micro-Z (registered trademark) KCV3010) processing.

The filtration conditions at this time are inlet pressure=2.5kg/cm ² and outlet pressure=0.5kg/cm ² .

The amount of filtrate was 12 l/min at the initial stage, and it was 3 l/min after 200-fold concentration, and the filtration stability was excellent.

When the waste liquid supplied for filtration is 5000 l, 4975 l of filtrate and 25 l of concentrated liquid are obtained by supplying ultrafiltration membrane.

The filtrate was NV=0.05%, pH=5.2, and the concentrate was NV=10%, pH=6.4.

This filtrate was returned to the final washing tank again to replace pure water, and the washing effect was good, and the result of the redissolution test of the coated object was also satisfactory.

Example 3

The concentrated solution of Example 2 was returned to the electrodeposition tank. After returning to the electrodeposition tank, the operating state is still stable, and the surface of the product after baking is still in good condition.

Example 4

The waste liquid discharged from the pure water washing tank used in Example 1 was supplied to a concentration tank with a total volume of 5000 liters, adjusted to pH=6.0 with acetic acid, and then supplied to an ultrafiltration membrane (manufactured by Asahi Kasei Co., Ltd.: Micro-Za (registered trademark) KCV3010) deal with.

The filtration conditions at this time are inlet pressure=2.5kg/cm ² and outlet pressure=0.5kg/cm ² . And in the filtration operation, the filtration process performs a 30-second acid backwash every 30 minutes. For acid backwashing, 300 ppm acetic acid was added to the filtrate, and 15 l of the resulting solution was used as backwashing solution each time. As a result, the pH of the concentrate is often adjusted to be in the range of 6.0 to 6.3. The filtrate volume was 12 l/min at the beginning, 10 l/min after 10-fold concentration, and 6 l/min after 100-fold concentration, showing excellent filtration stability. In addition, the filtration was carried out continuously for 4 days, and 5000l of filtrate was obtained every day, which was sent to the washing tank, and on the other hand, the pure water washing tank waste liquid in an amount equivalent to the amount of the filtrate was often added to the concentration tank. On the 5th day, stop adding the waste liquid of the washing tank with pure water, and carry out intermittent concentration treatment to the 5000l concentrate, so that it can be further concentrated to 250l. (Concentration ratio is 100 times) when the waste liquid that supplies filtration adds up to 25000l, obtain filtrate 24750l, concentrated solution 250l by supplying ultrafiltration membrane.

On the 5th day, the filtrate at the initial stage of intermittent concentration (5-fold concentration) was NV=0.04%, pH=5.9, and the final concentrate (100-fold concentration) was NV=6.1%, pH=6.2. This filtrate is still often returned to the final washing tank to replace pure water, but the washing effect is good, and the results of the coating redissolution test are not problematic.

Example 5

The same test as in Example 4 was carried out, and a part of the obtained ultrafiltration filtrate was subjected to a reverse osmosis membrane (manufactured by Toray Co., Ltd.: SU-700) for treatment. The reverse osmosis filtrate is used to spray the coated object when it exits the final washing tank, and the drenched water is recovered in the final washing tank, but the washing effect is good, and the result of the coated object redissolving test is not problematic.

Wherein, the reverse osmosis filtration is carried out at an operating pressure of 15kg/cm ² , the reverse osmosis filtrate is collected at a speed of 3 l/min, and the reverse osmosis concentrate is returned to the washing tank. The water quality of the reverse osmosis filtrate is below NV=0.001%, pH=6.4, conductivity=2μs/cm.

Comparative example 1

The final washing tank waste liquid of Example 1 was not adjusted to any pH, and was supplied to an ultrafiltration membrane (manufactured by Asahi Kasei Industry Co., Ltd.: Micro-Za (registered trademark) KCV3010) as in Example 1 to separate it into a concentrate and a filtrate. The pH of the concentrate rose from 6.5 to 7.0. The amount of filtrate produced by the ultrafiltration membrane is initially 12l/min, and it will gradually decrease as the concentration continues to circulate, and it will be reduced to below 1l/min when it is concentrated 5 times, and the filtration stability is not very good.

Comparative example 2

Operate under the same conditions as in Example 1, add acetic acid to adjust it to pH=6.0 by adding acetic acid to the waste liquid of NV=0.1% and pH=6.5 discharged from the final washing tank, and carry out ultrafiltration treatment the same as in Example 1. The volume of filtrate produced by ultrafiltration is initially 12l/min, but as the concentration continues to circulate, the pH of the concentrate will slowly rise, and on the other hand, the volume of filtrate will slowly decrease. To below 1l/min, in fact the ultrafiltration process can no longer continue.

Claims (9)

1. waste liquor from final water washing tank used treatment process, it is characterized in that, in the treatment process of the final water washing tank used institute of cation electrodeposition painting technology effluent discharge, make the pH of the interior waste liquid of thickener (6) often remain on below 6.4, allow this waste liquid in the filtration unit that has been equipped with semi-permeable membranes (9), circulate, make it to be separated into the concentrated solution and the filtrate that contain coating composition.

2. the waste liquor from final water washing tank used treatment process described in the claim 1 is characterized in that, all or part of returns and utilizes with washing water as final washing in final water washing tank used again to separate the filtrate obtain by semi-permeable membranes.

3. the waste liquor from final water washing tank used treatment process described in the claim 1 or 2, it is characterized in that, accumulate a certain amount of washing waste liquid in the thickener (6),, add acid the pH of liquid in the thickener is adjusted to below 6.0 until start of run by filtration unit (9) circulation beginning.

4. any one described waste liquor from final water washing tank used treatment process in the claim 1～3 is characterized in that the degree of enrichment of concentrated solution reaches the highest 200 times stage in the thickener of above-mentioned circulation waste liquid, and concentrated solution is extracted out from thickener.

5. any one described waste liquor from final water washing tank used treatment process in the claim 1～4, it is characterized in that, use multiple-grooved as final water washing tank used situation under, the waste liquid of final water washing tank used each groove all returns in separately the last groove, the waste liquid of final water washing tank used initial groove is sent into thickener to supply with filtration unit, and at least a portion of filtrate is returned final water washing tank used final groove and utilized with washing water as final washing again.

6. any one described waste liquor from final water washing tank used treatment process in the claim 1～5, it is characterized in that, during the waste liquor from final water washing tank used that the waste liquid of final water washing tank used discharge is separated into the concentrated solution that contains coating composition and filtrate by the filtration unit circulation that has been equipped with semi-permeable membranes in the cation electrodeposition painting technology is handled, semi-permeable membranes is with having added 300～3, the back flushing of 000ppm organic acid filtrate keeps through being everlasting below 6.4 the pH of concentrated solution in the thickener.

7. any one described waste liquor from final water washing tank used treatment process in the claim 1～6, wherein the pH value of waste liquor from final water washing tank used is adjusted with electrode solution or organic acid or thionamic acid, carbonic acid and is carried out.

8. any one described waste liquor from final water washing tank used treatment process in the claim 1～7, wherein semi-permeable membranes is a ultra-filtration membrane.

9. any one described waste liquor from final water washing tank used treatment process in the claim 1～7, wherein to separate be the filtrate that ultra-filtration and separation is handled to be carried out reverse osmosis isolation again handle to semi-permeable membranes.

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