JP2786982B2 - Wastewater treatment agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment agent used for treating wastewater generated by cleaning semiconductor elements, printed circuit boards, and the like.

[0002]

2. Description of the Related Art Conventionally, cleaning of semiconductor elements, printed circuit boards, and the like has been performed using a specific fluorocarbon and a chlorine-based solvent such as 1,1,1-trichloroethane. However, since the possibility of depletion of the ozone layer was pointed out in 1995,
At the end of the year, it was decided to abolish the above CFCs. For this reason, in Japan, development of alternative CFCs for cleaning in place of the above specified CFCs has been actively conducted mainly in the electric and electronic industries. At present, alternative chlorofluorocarbons, which are roughly classified into two types, a solvent-based detergent and a water-based detergent, have been developed.
All of the above solvent-based cleaning agents have flammability except for halogenated hydrocarbons, so that when used, attention must be paid to fire and explosion-proof measures are indispensable. Also,
Handle with care due to toxicity. On the other hand, the above-mentioned water-based detergent is basically not flammable and has very little danger. The above-mentioned water-based cleaning agents are roughly classified into two types: an alkali saponification type cleaning agent and a cleaning agent containing a neutral high concentration surfactant as a main component. The alkaline saponification type cleaning agent is excellent in detergency, but has a problem that, for example, electromigration occurs when the cleaning agent remains due to insufficient rinsing. From such a viewpoint, an aqueous cleaning agent containing a neutral high-concentration surfactant as a main component has recently attracted attention.

On the other hand, the above-mentioned detergent containing a neutral high-concentration surfactant as a main component is suitable for practical use because it is a non-dangerous substance, is easy to handle, and can be rinsed with water. Therefore, development of a cleaning agent containing a neutral high-concentration surfactant as a main component has been actively carried out. However, when cleaning is performed using this cleaning agent, there is a problem in treating wastewater generated after the cleaning. As this wastewater treatment, a method of treating the wastewater with a wastewater filtration system composed of activated carbon, ion exchange resin, activated sludge and the like is generally used.

[0004]

However, the above-mentioned wastewater filtration system has a problem that it is a large-scale facility and requires too much cost for processing. Furthermore, the above-mentioned cleaning agent is composed of a nonionic surfactant and water, and has a problem that the nonionic surfactant cannot be sufficiently removed. As described above, in the treatment of wastewater generated during cleaning using a cleaning agent containing a neutral high-concentration surfactant as a main component, which is attracting attention as an alternative chlorofluorocarbon,
The fact is that an effective treatment method has not yet been established and its development is strongly desired.

[0005] In order to solve such a situation, the present applicant has proposed a wastewater treatment method in which a nonionic surfactant in wastewater is precipitated by using a novolak resin as a main component and using an alkaline substance to separate the nonionic surfactant. (Japanese Patent Application No. 5-51779). However, when the supernatant treated by the above wastewater treatment method was analyzed, a substance having a high chemical oxygen demand (COD) value and not being present in the wastewater was detected. Therefore, even if this supernatant liquid is treated with activated sludge, activated carbon, etc., the COD value of the supernatant liquid is high, and high-level and high-cost treatment is required to treat the supernatant liquid to a level that can be discharged. Becomes

The present invention has been made in view of such circumstances, and it is an object of the present invention to set a nonionic surfactant at a level that enables efficient removal of a nonionic surfactant and a COD value after wastewater treatment that can be discharged. Its purpose is to provide a wastewater treatment agent that can be used.

[0007]

Means for Solving the Problems In order to achieve the above object, the wastewater treatment agent of the present invention is configured to contain the following (A) and (B). (A) A purified novolak resin obtained by removing impurities by elution with water containing an alkaline substance. (B) an alkaline substance.

[0008]

In other words, the present inventor analyzed the components in the supernatant liquid generated when performing wastewater treatment using novolak resin, and found that components not contained in the wastewater were contained.
This was found to be the cause of increasing the COD value of the wastewater-treated supernatant. As a result of repeated research on a substance that causes the increase of the COD value, it was found that the substance was caused by the novolak resin. Next, as a result of repeated studies for removing impurities caused by the novolak resin, impurities in the novolak resin were previously removed by elution with water containing an alkaline substance, and a purified novolak resin and an alkaline substance were contained. The present inventors have found that when wastewater treatment is performed using a wastewater treatment agent, the COD value of the treated supernatant liquid is reduced, and the present invention has been achieved. Therefore, by using the wastewater treatment agent of the present invention, the nonionic surfactant can be efficiently removed, and the COD value of the wastewater treatment liquid can be set to a low level that can be discharged.

Next, the present invention will be described in detail.

[0010] The wastewater treatment agent of the present invention is obtained using a purified novolak resin (A) and an alkaline substance (B).

The purified novolak resin (A) as the main component of the present invention is obtained by purifying a novolak resin to remove impurities. The novolak resin is not particularly limited, and includes conventionally known resins. As the form of the novolak resin, a granular form is preferably used. The term “granular” is intended to include not only granules, powders, flakes, and marbles, but also powders formed into pellets by tableting or the like. As the granular novolak resin, it is preferable to use a resin mainly composed of a novolak resin represented by the following general formula (1). In particular, the number of repetitions n in the general formula (1) is preferably 5 to 7. By using one having a repetition number n of 5 to 7, separation of the nonionic surfactant in the wastewater from the others is more effective.

[0012]

Embedded image

The above alkaline substance (B) is used for the purpose of dissolving the purified novolak resin in wastewater. Examples of such an alkaline substance (B) include an alkali metal hydroxide, an alkaline earth metal hydroxide, ammonia, and an amine. Among them, it is preferable to use sodium hydroxide and potassium hydroxide. The amount of the alkaline substance used is set to an amount necessary to dissolve the novolak resin. For example, the pH is adjusted so that the aqueous liquid containing the novolak resin as a main component has a pH of 8 or more, particularly preferably 9 or more. It is preferred to do so.

The purified novolak resin can be obtained by using the novolak resin, for example, through the following purification step. That is, an alkaline substance and water are added to the novolak resin and stirred to prepare an aqueous liquid containing the novolak resin as a main component, and impurities in the novolak resin are eluted into the aqueous liquid. Next, an acidic substance is added to the aqueous liquid of the novolak resin to precipitate the novolak resin in the aqueous liquid. Next, the supernatant liquid from which the impurities in the novolak resin are eluted is removed from the aqueous liquid containing the precipitated substance of the novolak resin. If further purification of the novolak resin is desired, the above operation is repeated.
In this way, the impurities contained in the novolak resin are eluted into the supernatant and are removed together with the supernatant. By performing such a purification treatment, when the novolak resin is used for wastewater treatment, elution of impurities derived from the novolak resin into the wastewater treatment liquid is reduced, so that the COD value of the supernatant liquid after the wastewater treatment is reduced. It can be set to a low level that can be discharged. This is the most important feature of the present invention.
In addition, this purification method is effective not only for low molecular weight novolak resins but also for high molecular weight ones.

In the above-mentioned purification method, the method for removing the supernatant is not particularly limited, and examples thereof include a method using a device such as a centrifuge or a dehydrator. Further, as a method for further purifying the novolac resin precipitated substance remaining after removing the supernatant liquid from which impurities are eluted, a method of adding water to the substance and washing the same can be cited.

The acidic substance used to form a precipitate consisting of the novolak resin by adding to the aqueous solution of the novolak resin in the purification step includes hydrochloric acid, sulfuric acid, and the like.
Oxalic acid and the like. As the addition amount of the acidic substance,
Any amount can be used as long as it can insolubilize the novolak resin in the aqueous liquid. For example, an amount capable of lowering the pH of the entire system to 8 or less, preferably to a substantially neutral range of pH 7.5 to 6.5. Is set to

The wastewater treatment using the wastewater treatment agent of the present invention is performed, for example, as follows. That is, a novolak resin (A) and an alkaline substance (B) purified by the above-mentioned purification method are prepared, and these are blended into wastewater and mixed uniformly. Next, an acidic substance is added to the mixture. Through such a process, the wastewater is separated into a precipitated substance and a supernatant. In the step of blending the purified novolak resin (A) and the alkaline substance (B), one of A and B may be added to the wastewater in advance, and then the rest may be added. Alternatively, the purified novolak resin (A) and the alkaline substance (B) may be mixed in advance, and this mixture may be added to the wastewater.

The amount of the purified novolak resin (A) depends on the type of the nonionic surfactant contained in the wastewater,
It is appropriately determined depending on the composition of impurities in the wastewater,
For example, with respect to 100 parts by weight of a nonionic surfactant in wastewater (hereinafter abbreviated as “parts”), 10 parts of novolak resin
It is preferable to set the ratio to 150 parts.

In the wastewater treatment step, the kind and amount of the acidic substance to be added to the wastewater after adding the purified novolak resin (A) and the alkaline substance (B) are set in the same manner as in the step of purifying the novolak resin. Is done.

In the wastewater treatment using the wastewater treatment agent of the present invention, it is preferable not to use a conventionally used adsorbent or the like. For example, when an inorganic coagulant is used, the amount of the precipitated substance and the volume occupied by the precipitated substance increase, and the cost of removing the precipitated substance and the like increases, and the cost of wastewater treatment increases.

As described above, in the wastewater treatment using the wastewater treatment agent of the present invention, the novolak resin is dissolved in the wastewater by using an alkaline substance in combination, and then the nonionic resin in the wastewater is added by adding an acidic substance. The surfactant is incorporated and precipitated. For this reason, it becomes possible to separate the wastewater into a supernatant liquid and a precipitate, and the wastewater can be treated by removing the precipitate. The supernatant is transparent and contains almost no impurities derived from novolak resin as well as dry solids.
Therefore, the COD value of the supernatant is reduced to a level at which it can be discharged, and the biological treatment of activated sludge or the like can also reduce the BOD value (biochemical oxygen demand) of the supernatant. As a result, wastewater treatment is further advanced.

[0022]

As described above, the wastewater treatment agent of the present invention comprises a purified novolak resin (A) from which impurities are removed by elution of water containing an alkaline substance and an alkaline substance (B).
It is composed of Therefore, since the novolak resin has been purified in advance, the nonionic surfactant can be removed without impurities derived from the novolak resin being eluted into the wastewater treatment liquid. As described above, by using the wastewater treatment agent of the present invention, the wastewater in the wastewater after washing with the aqueous detergent mainly containing a neutral high-concentration surfactant, which was very difficult to treat by the conventional method, is used. The nonionic surfactant can be separated and removed at a low cost, easily and at a high level, and the wastewater after the wastewater treatment can have a low COD value that can be discharged as it is. Therefore, the wastewater treatment agent of the present invention is most suitable for treating wastewater for cleaning in the field of semiconductors, which is being switched to cleaning with alternative CFCs. Furthermore, the wastewater treatment agent of the present invention can be used not only for wastewater containing nonionic surfactants, but also for wastewater containing polyvinyl alcohol (PVA) generated in the yarn-making process, and cationic, anionic and amphoteric other than nonionic surfactants. Wastewater containing surfactants can also be separated into precipitated material and clear supernatant. Since the supernatant does not contain impurities derived from the novolak resin, the COD value can be set to a low level at which the supernatant can be discharged. Furthermore, by effectively treating the treatment liquid with activated sludge, activated carbon, etc., not only COD value but also B
It is easy to set the OD value to a level that allows wastewater to be discharged.

Next, the present invention will be described in detail based on embodiments.

[Preparation of Simulated Waste Water] A cleaning agent containing a neutral high-concentration surfactant containing a nonionic surfactant, which is one of the alternative CFCs, is prepared. Simulated wastewater (nonionic surfactant content: 45000 ppm) having substantially the same components was prepared. As a detergent containing a neutral high-concentration surfactant, Clean-through 700 manufactured by Kao Corporation was used.

Prior to the examples, the following three types of novolak resins were prepared. Novolak resin A: a powdery material having a repeating number n of 5 in the general formula (1). Novolak resin B: a powdery material having a repeating number n of 7 in the general formula (1). Novolak resin C: a powdery material having a repetition number n of 6 in the general formula (1).

[0026]

Examples 1 to 5 Each of the above novolak resins was purified by the method described above. That is, first, the novolak resin 2
To 0 parts, 80 parts of an aqueous sodium hydroxide solution was blended and dissolved by stirring to elute impurities in the novolak resin. Next, 4 parts of hydrochloric acid having a concentration of 37% was added to the above solution to separate into a precipitate consisting of a novolak resin and a supernatant from which impurities were eluted. Then, the precipitated substance composed of the novolak resin and the supernatant were separated by a centrifugal separator, and the supernatant was removed. The impurities eluted in the supernatant were analyzed by gas chromatography (Hullet Packer,
HP5971). As a result, most of the impurities are phenol, 2,2'-methylenebis, 4,
It was found to be 4'-methylenebis. In addition, the conditions of gas chromatography are 1 ml / min with a column: HP-5 and a carrier gas: He.

Next, wastewater treatment of pseudo wastewater was performed under the conditions shown in Table 1 below. That is, first, a novolak resin purified by the above method shown in Table 1 below and sodium hydroxide were added to the pseudo wastewater at a ratio shown in the same table, and the mixture was stirred and uniformly mixed. Then, hydrochloric acid (concentration: 37%) was added at a rate shown in the same table with stirring to make the pH substantially neutral. Then, after further stirring, the mixture was left to stand.

[0028]

[Table 1]

[0029]

[Comparative Example] Novolak resin was not purified. Other than that, the pseudo wastewater treatment was performed by the same operation as in Example 1 under the conditions shown in Table 2 below.

[0030]

[Table 2]

The pseudo wastewater treated in this manner was separated into a precipitated substance and a clear supernatant liquid in Examples 1 to 5 and Comparative Example. Then, by measuring the concentration of the nonionic surfactant in the supernatant, the removal rate of the nonionic surfactant was calculated from the concentration of the nonionic surfactant before the treatment. Further, the precipitated substance was evaporated to dryness and solidified, and the weight was measured to determine the solid content. Further, the transmittance of the supernatant and C
The OD value was measured. The results are shown in Table 3 below.
The measurement of the concentration of the nonionic surfactant was carried out according to c.
m. c concentration (micelle formation concentration) or more was carried out by the potassium ferrocyanide method, and c. m. If the concentration is less than c, use a white light source with a Dunoi's surface tensiometer
The transmittance (%) is shown with distilled water as 100. Further, the COD value was measured by an acidic sodium permanganate method.

[0032]

[Table 3]

From the results shown in Table 3, it can be seen that the nonionic surfactant in the supernatant liquid treated in each of the examples and comparative examples was almost completely removed. In addition, the solid content of the precipitated material was not so large, the supernatant was easily separated from the precipitated material, and the volume of the precipitated material was small. However, the COD value of the wastewater treated according to Examples 1 to 5 is a low level that can be discharged, whereas the COD value of the wastewater treated according to the comparative example is very high, and a large amount of impurities are contained in the supernatant. It can be seen that it was eluted.

Claims (1)

(57) [Claims] 1. A wastewater treatment agent comprising the following (A) and (B): (A) A purified novolak resin obtained by removing impurities by elution with water containing an alkaline substance. (B) an alkaline substance.