JP3128249B2 - Wash water treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous detergent such as an aqueous solution of a surfactant, an emulsion detergent, an alkaline detergent, or a semi-aqueous detergent mainly composed of an organic solvent which requires water rinsing, for metal, glass, or the like. The present invention relates to a method for treating rinsing water in a rinsing step of a degreasing cleaning of plastics, ceramics, etc. and a soldering flux of a printed circuit board, returning the rinsing water to the rinsing step, and using the circulating water as the rinsing water.

[0002]

2. Description of the Related Art Rinsing water discharged from a degreasing or flux cleaning process using an aqueous or semi-aqueous detergent includes surfactants derived from detergents and stains, organic solvents, oils, rosins, and alkalis. A large amount of metal salts, emulsions and the like are mixed. In order to use this washing water in circulation, it is necessary to remove these contaminants in a circulation mechanism.

As a treatment method, there are activated carbon, activated sludge, reverse osmosis, coagulation sedimentation, etc. for organic components such as surfactants, oils, organic solvents and rosin, and ions such as metal ions and alkali metal salts. For the components, ion exchange resin,
There are electrodialysis and reverse osmosis. Among these, when considering a treatment method of circulating use of washing water in the washing process of degreasing washing or flux washing, a high-level treatment is performed in a short time, and the above-mentioned mixed components are used until they can be used as washing water. It is desired that the treatment apparatus can be removed and that the treatment apparatus is compact and can be easily installed as an auxiliary equipment of the washing machine.
From this viewpoint, a method using a combination of activated carbon and an ion exchange resin is used. In this case, a method is generally employed in which the washing water is passed through a column filled with activated carbon to remove organic substances, and then passed through a column filled with an ion exchange resin to remove ions.

[0004]

However, in washing water discharged from degreasing washing or flux washing with an aqueous detergent or semi-aqueous detergent, an emulsion of oil, rosin or the like due to a surfactant or alkali in the detergent is contained. And the organic matter load on the activated carbon is very high. For this reason, the ability of the activated carbon having a limited adsorption capacity to remove organic substances is reduced at an early stage, and the frequency of replacing the activated carbon with new activated carbon is increased. If the frequency of replacement of the activated carbon is high, the cost of regeneration and maintenance of the activated carbon is high, and the production is hindered.

[0005] If the concentration of organic components such as surfactants, oils, organic solvents, and emulsions in the wastewater treated by activated carbon is high, the concentration of the organic components in the wastewater after the treatment is also high, and the emulsified product is completely removed. When the treatment with the ion exchange resin is subsequently performed, there is also a problem that the ion exchange resin is organically contaminated and the ion exchange capacity is reduced. From these viewpoints, it is desired to remove the emulsified product in the washing water and reduce the organic substance load on the activated carbon as much as possible.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that ultrafiltration with a hollow fiber ultrafiltration membrane allows simple and compact equipment to be used in washing water. It has been found that the emulsified product is removed and the load of organic substances on the activated carbon is significantly reduced, and the present invention has been completed.

That is, the present invention relates to a method for treating a washing water containing a surfactant and / or an alkali emulsified substance in a washing step of a degreasing washing or a flux washing, returning the washing water to the washing step, and recycling and using the same. The washing water is subjected to activated carbon treatment after ultrafiltration with a hollow fiber ultrafiltration membrane, and then returned to the washing step, and the washing water treated with activated carbon by the above method is subjected to ion exchange. This is a method for treating washing water, which comprises subjecting the resin to a resin treatment and returning to a washing step.

[0008] As the material of the hollow fiber ultrafiltration membrane used in the present invention, polyacrylonitrile, cellulose acetate, polysulfone and the like used in conventional ultrafiltration can be used. When using a hollow fiber ultrafiltration membrane, in order to obtain a large filtration membrane area, a large number of the hollow fibers are filled in a cylindrical container, and epoxy resin or the like is opened in a state where both ends of the hollow fibers are open. It is preferably used as a material sealed with a sealing material such as a polyurethane resin.

The thickness of the hollow fiber ultrafiltration membrane used in the present invention is preferably from 10 to 400 μm, preferably from 20 to 100 μm.
Is more preferred. Further, the inner diameter of the hollow fiber ultrafiltration membrane is preferably 100 to 1000 μm, and 100 to 400 μm.
μm is more preferred. The molecular weight cut-off of the hollow fiber ultrafiltration membrane is preferably from 5,000 to 15,000, more preferably from 6,000 to 13,000. Further, the filtration rate of water of the hollow fiber ultrafiltration membrane is preferably 10 l / h or more per 1 m ^{2 of} membrane area.
More preferably, it is 1 / h or more.

[0010] Before ultrafiltration, it is preferable to place a pre-filter such as a film, a cotton, or a wind type for removing dust. As the hollow fiber ultrafiltration membrane used in the present invention, those manufactured by the methods disclosed in JP-A-47-50398 and JP-A-57-136903 can be used.

The washing water ultrafiltered by the specific hollow fiber ultrafiltration membrane is then treated with activated carbon.
Usually, an activated carbon column is used for this. As the activated carbon filled in the activated carbon column, water-treated granular activated carbon is generally used. The amount of activated carbon is determined by the amount of treated water, installation space, replacement frequency, and the like, depending on the individual case.

When a large amount of ions are contained in the washing water thus treated with activated carbon, it is possible to remove the ionic components with an ion-exchange resin or the like, and then return to the washing step to recycle the washing water. it can. Removal of the ionic component is also possible by electrodialysis or reverse osmosis.

[0013]

The present invention will be described below in detail with reference to examples.

[0014]

EXAMPLES 1-5 AND COMPARATIVE EXAMPLE A washing water model liquid (permeability: 44%, COD: 640 ppm) containing sodium carbonate, sodium silicate, surfactant, oil, and rosin was used as a hollow fiber ultra-thin powder as shown in Table 2. Ultrafiltration was performed using filtration membranes A to E, and then the mixture was passed through a column filled with granular activated carbon for water treatment (manufactured by Kuraray Co., Ltd., trade name: Kuraray Coal KW10 to 30 mesh). The transmittance and COD of the washing water after ultrafiltration, and the transmittance and COD of the washing water after passing through the activated carbon column were measured.
Table 1 shows the results.

The washing water from which emulsions and organic substances have been removed by the above method still contains an alkali salt and has a conductivity of 1,6.
Since it showed a high value of 70 μS / cm and could not be reused as washing water, when this washing water was passed through a cation exchange resin column and an anion exchange resin column, washing water having a conductivity of 10 μS / cm was obtained. Possible washing water was obtained.

[0016] For comparison, a case where ultrafiltration was not performed was also performed. Table 1 shows the results. In addition, the said transmittance | permeability is a value measured at 550 nm with a visible absorption spectrometer, and this numerical value is so large that the quantity of an emulsion is small, and 100% of transmittance | permeability shows that an emulsion is not seen. Also, CO
D is a value measured by the method described in JIS-K0102 (1986), and a smaller value indicates a smaller amount of organic matter. Further, the conductivity is a value measured by a conductivity meter AOL-40 manufactured by Electrochemical Instruments.

FIG. 1 shows one embodiment of the above-mentioned circulating flow of washing water.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

According to the present invention, the organic matter load on the activated carbon can be greatly reduced by a simple method, the life of the activated carbon is extended, the frequency of replacement of the activated carbon is reduced, and the organic matter of the washing water after the activated carbon treatment is reduced. The level can be reduced, and high-quality washing water can be recycled.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a washing water treatment method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 Ultrafiltration device using hollow fiber ultrafiltration membrane 2 Activated carbon column 3 Ion exchange resin column 4 Rinse tank 5 Rinse water circulation path

Claims (2)

(57) [Claims] In a method of treating a washing water containing an emulsified product with a surfactant and / or an alkali in a washing step of a degreasing washing or a flux washing, the washing water is returned to the washing step, and the washing water is recycled. A method for treating washing water, comprising performing ultrafiltration with a hollow fiber ultrafiltration membrane, treating with activated carbon, and returning to a washing step. 2. A method for treating a washing water containing a surfactant and / or an alkali emulsified product in a washing step of a degreasing washing or a flux washing, returning the washing water to the washing step, and circulating and reusing the washing water. A method for treating washing water, comprising ultrafiltration with a hollow fiber ultrafiltration membrane, treatment with activated carbon, treatment with an ion exchange resin, and returning to the washing step.