JP2010131489A - Method of treating aromatic amines-containing wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently treating aromatic amines-containing wastewater which reduces the concentration of aromatic amines in the aromatic amines-containing wastewater, and reduces the amount of used solvent. <P>SOLUTION: In the method of treating the aromatic amines-containing wastewater, the aromatic amines-containing wastewater is subjected to extraction treatment with an aromatic hydrocarbon solvent under a condition where pH is 5-8 and temperature is 60-80°C, an aromatic hydrocarbon solvent layer obtained by oil-water separation is subjected to back extraction treatment with an alkaline aqueous solution and an aromatic hydrocarbon solvent layer having a reduced concentration of the aromatic amines, obtained by the oil-water separation is circulated and used for the extraction treatment of the wastewater. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for treating aromatic amine-containing wastewater. Specifically, the present invention relates to a method for treating wastewater containing aromatic amines that efficiently reduces the concentration of aromatic amines in the wastewater.

Wastewater containing organic matter is often treated with activated sludge. However, when the concentration of organic matter is high, there is a problem that the amount of treatment increases because it is diluted and treated at a reduced concentration. If the organic matter concentration is considerably high, it may be burned, but ordinary wastewater is not efficient for incineration because the organic matter concentration is low and the water content is high. In addition, if the amount of waste water is large, there is a problem that the combustion equipment becomes large.
When the organic matter concentration is relatively high and the amount of wastewater is large, usually the organic matter in the wastewater is extracted with an organic solvent to reduce the organic matter concentration in the wastewater. In this case, usually, wastewater having a reduced organic matter concentration is subjected to activated sludge treatment, and the organic matter having an increased concentration is incinerated together with an organic solvent.
Extraction of organic matter in wastewater with an organic solvent is not performed sufficiently by simply mixing the organic solvent and wastewater, and a compound that promotes extraction may be added (see, for example, Patent Document 1). ).

  Aromatic amines such as 4-aminodiphenylamine are extremely important as raw materials, intermediates and the like for pharmaceuticals, agricultural chemicals, additives and the like. Aromatic amine-containing wastewater produced in the production process of such aromatic amines may have a relatively high aromatic amine concentration and a large amount of wastewater. For example, 4-aminodiphenylamine is produced by hydrogenating a 4-nitrosodiphenylamine / alkali metal salt aqueous solution or a 4-nitrosodiphenylamine / tetraalkylammonium salt aqueous solution in the presence of a hydrogenation catalyst (see, for example, Patent Document 2). ). At this time, the reaction solution is oil-water separated into an organic layer containing 4-aminodiphenylamine and waste water. Waste water contains 4-aminodiphenylamine as a reaction product, 4-nitrosodiphenylamine as a reaction raw material, aminophenol derived from decomposition products of 4-nitrosodiphenylamine, etc., and its chemical oxygen demand (COD) is about 2500 to It becomes 5000 ppm. The amount of waste water is also discharged in a large amount (several to several tens of tons / hour) depending on the production amount of 4-aminodiphenylamine.

As a method of treating aromatic amines-containing wastewater discharged from such a production process, there is a method of treating activated sludge after oxidizing it with hypochlorite and reducing its concentration. However, although the hypochlorite remaining in the wastewater is reduced, the activated sludge treatment may be hindered even if a small amount remains.
Further, even if the aromatic amines-containing wastewater is simply extracted with a hydrophobic organic solvent, the extraction of the aromatic amines is not sufficient and the consumption of the organic solvent increases, which is not economical. Therefore, a method for efficiently treating aromatic amine-containing wastewater is desired.
JP 2001-179242 A JP-A-6-306020

  Under such circumstances, as a result of intensive studies on the method for treating aromatic amines-containing wastewater, the present inventors have determined that wastewater containing aromatic amines has a pH of 5-8 and a temperature of 60-80 ° C. Extracting with an aromatic hydrocarbon solvent under the conditions of the above, the resulting aromatic hydrocarbon solvent layer is back-extracted with an aqueous alkali solution, and the resulting aromatic hydrocarbon solvent layer having a reduced concentration of aromatic amines, It has been found that by recycling the wastewater for extraction treatment, the concentration of aromatic amines in the wastewater can be reduced, the amount of solvent used can be reduced, and the wastewater containing aromatic amines can be treated efficiently. The present invention has been reached.

  That is, the present invention is an aromatic carbonization obtained by subjecting waste water containing aromatic amines to extraction treatment with an aromatic hydrocarbon solvent under conditions of pH 5-8 and temperature 60-80 ° C., and oil-water separation. An aromatic hydrocarbon solvent layer having a reduced concentration of aromatic amines obtained by subjecting a hydrogen solvent layer to back extraction with an alkaline aqueous solution and oil-water separation is circulated for use in the extraction treatment of the waste water. This is a method for treating wastewater containing aliphatic amines.

  By the method of the present invention, the concentration of aromatic amines in the aromatic amine-containing wastewater can be reduced, the amount of solvent used can be reduced, and the aromatic amine-containing wastewater can be treated efficiently.

Hereinafter, the present invention will be described in detail. Examples of the aromatic amine-containing wastewater include wastewater generated in the process of producing 4-aminodiphenylamines.
In the production process of 4-aminodiphenylamines, a 4-nitrosodiphenylamine / alkali metal salt aqueous solution or a 4-nitrosodiphenylamine / tetraalkylammonium salt aqueous solution is hydrogenated in the presence of a hydrogenation catalyst, and the resulting reaction solution is separated into oil and water. The 4-aminodiphenylamines are obtained from the organic layer, and the aqueous layer is treated as waste water.
Waste water contains 4-aminodiphenylamine as a reaction product, 4-nitrosodiphenylamine as a reaction raw material, aminophenol derived from a decomposition product of 4-nitrosodiphenylamine, diphenylamine as a reaction raw material of 4-nitrosodiphenylamine, etc. The oxygen demand (COD) can be as high as about 2500 to 5000 ppm.

  Examples of the aromatic hydrocarbon solvent include benzene, toluene, and xylene. In the present invention, toluene or xylene is preferably used because of extraction at a high temperature and ease of handling.

  The extraction has a wastewater pH of about 5-8, preferably about 6-7, a temperature of about 60-80 ° C, preferably about 75-80 ° C, and the amount of solvent used is about 0.05 by weight with respect to the wastewater. -0.4, preferably about 0.1-0.3, extraction time is about 0.01-0.2 hours, preferably about 0.01-0.1 hours, using a stirred tank or line mixer Do.

If the wastewater pH exceeds about 8, the extraction rate is lowered, which is not preferable for reducing the COD of the wastewater. There is no change in the extraction rate even when the pH is less than about 5.
Since the wastewater generated in the process of producing 4-aminodiphenylamines has a pH of more than 12, it is neutralized in advance using a stirring tank or a line mixer, adjusted to a pH of 8 or less, and then extracted.

If the extraction temperature is lower than about 60 ° C., the extraction rate is undesirably low. As the temperature increases, the generation of emulsion decreases, and at about 80 ° C., it is suppressed to an extent that there is no problem in performing the extraction operation. Even if it exceeds about 80 ° C., an effect commensurate with it cannot be obtained, and the heating energy of the waste water increases, which is not preferable.
In addition, when using benzene as a solvent, in order to extract at high temperature, it needs to carry out under pressure, Therefore Toluene or xylene is used preferably. Since toluene azeotropes at about 84 ° C., it is performed at about 80 ° C. or less from this point.
In addition, in the case of wastewater generated in the process of producing 4-aminodiphenylamines, it is preferable to neutralize the reaction solution at about 60 to 80 ° C. without cooling it to room temperature, followed by extraction treatment.

The larger the amount of the solvent, the shorter the extraction time. However, even if the weight ratio exceeds about 0.4 with respect to the wastewater, an effect commensurate with it cannot be obtained. If the extraction time is less than about 0.05, it is necessary to lengthen the extraction time. However, if the extraction time is increased, the generation of emulsion increases.
When the extraction time is shorter than about 0.01 hour, the extraction becomes insufficient, and when it exceeds about 0.2 hour, the generation of emulsion increases, which is not preferable.

  After the extraction process, oil and water are separated in a separation tank. The residence time of the aqueous layer in the separation tank is about 0.3 to 0.7 hours, preferably 0.4 to 0.5 hours. If the residence time is shorter than about 0.3 hours, the COD of the aqueous layer (waste water) becomes high, which is not preferable. Even if it is longer than about 0.7 hours, the COD does not further decrease, and it is not preferable only that the separation tank is enlarged.

By the above treatment, the concentration of aromatic amines in the wastewater is lowered, and COD is lowered. For example, in wastewater generated in the process of producing 4-aminodiphenylamines having a COD of about 2500 to 5000 ppm, the COD is reduced to about 1000 ppm or less, usually about 700 to 800 ppm. Moreover, the aromatic hydrocarbon solvent to contain is 10 ppm or less.
The aromatic amines-containing wastewater with reduced COD is finally subjected to activated sludge treatment.

The separated aromatic hydrocarbon solvent layer is extracted (back-extracted) with an alkaline aqueous solution, and the aromatic hydrocarbon solvent layer having a reduced concentration of aromatic amines obtained by oil-water separation is used for waste water extraction treatment. Recycled as an aromatic hydrocarbon solvent.
The extraction with an alkaline aqueous solution is performed at a weight ratio of about 10 to 25% by weight, preferably about 15 to 20% by weight, with respect to the aromatic hydrocarbon solvent layer. 0.3 to 0.6, the temperature is about 60 to 80 ° C., preferably about 65 to 75 ° C., the extraction time is about 0.3 to 1 hour, preferably about 0.5 to 1 hour, and the stirring tank Etc.

As the alkaline aqueous solution, a caustic soda solution is usually used. If the concentration is lower than about 10% by weight, the extraction ability is low, and if it is higher than about 20% by weight, tar is precipitated, which is not preferable.
If the amount of the alkaline aqueous solution is less than about 0.05 by weight, the extraction ability is low, the viscosity increases and it becomes difficult to handle, and if it is more than about 0.75, the corresponding effect cannot be obtained.
When the temperature is less than about 60 ° C, the liquid separation rate is slow, and when it exceeds about 80 ° C, the effect corresponding to that cannot be obtained, the heating energy increases, and measures to suppress the evaporation of the aromatic hydrocarbon solvent are necessary. It is not preferable.
If the extraction time is shorter than about 0.3 hours, the extraction becomes insufficient, and even if it exceeds about 1 hour, an effect commensurate with it cannot be obtained.

  After extraction with an alkaline aqueous solution, oil and water are separated in a separation tank. The residence time of the aqueous layer in the separation tank is about 0.3 to 1 hour, preferably 0.5 to 1 hour. If the residence time is shorter than about 0.3 hours, the separation is not sufficient, and even if the residence time is longer than about 1 hour, an effect commensurate with it cannot be obtained.

  The aromatic hydrocarbon solvent layer, which has been separated to reduce the concentration of aromatic amines, is recycled as an extraction solvent for wastewater. The alkaline aqueous solution layer contains about 3 to 7% by weight of tar-like aromatic amines and is incinerated.

  According to the present invention, for example, in the case of aromatic amine-containing wastewater produced in the process of producing 4-aminodiphenylamines having a COD of about 2500 to 5000 ppm, the wastewater with a COD of about 1000 ppm or less is reduced, and the load of activated sludge treatment is reduced. Moreover, it can be set as the alkaline aqueous solution which contains about 3-5 weight% tar-like aromatic amines of the amount of about 4-5 weight% with respect to the wastewater which can be combusted.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples. The COD was measured by the method described in JIS K0102.

Example 1
822 g of aromatic amine-containing wastewater (pH: 14.1, COD: 2900 ppm) generated in the process of producing 4-aminodiphenylamines is placed in a flask, and the temperature is kept at 65 ° C. while stirring, and 98% by weight sulfuric acid Neutralized to pH 7. Next, 81.4g of recovered toluene (oil layer extracted with caustic soda and separated into oil and water) and 0.8g of new toluene (solvent amount with respect to waste water: 0.1 by weight) are added and extracted at 65 ° C for 10 minutes. Thereafter, the mixture was allowed to stand for 30 minutes for oil / water separation.
The separated aqueous layer (waste water) was 880 g, and its COD was 720 ppm.
To the separated oil layer (toluene layer), 25 g of caustic soda solution of 25% by weight (amount of caustic soda solution with respect to the oil layer: about 0.3 by weight) was added, extracted for 10 minutes, and then allowed to stand for 30 minutes for oil-water separation. went. The obtained oil layer was 76.9 g, and the water layer (caustic soda solution) was 50.7 g. The COD of the aqueous layer is about 5% by weight.

Example 2
The extraction pH was changed (neutralization pH was changed), and extraction was performed in the same manner as in Example 1 except that 82.2 g of new toluene was used, and the relationship between the extraction pH and the treated water COD was determined. The results are shown in FIG. When the extraction pH exceeds 8, the extraction rate decreases.

Example 3
Extraction was carried out in the same manner as in Example 1 except that the extraction temperature was changed and 82.2 g of new toluene was used, and the relationship between the extraction temperature and treated water COD and the amount of treated water decreased were determined. The results are shown in FIG. When the extraction temperature is lower than about 60 ° C., the extraction rate is lowered.

Example 4
Extraction was performed in the same manner as in Example 1 except that 82.2 g of new toluene was used and the extraction time was changed, and the relationship between the extraction time and the emulsion layer height was determined. The results are shown in FIG. The higher emulsion layer is due to the increase in emulsion. The longer the extraction time, the more emulsion is generated.

Example 5
1201 g of aromatic amine-containing wastewater (pH: 13.1, COD: 3700 ppm) generated in the process of producing 4-aminodiphenylamines is placed in a flask, and the temperature is maintained at 60 ° C. while stirring, and 98% by weight sulfuric acid Neutralized to pH 7.7. Next, 60 g of xylene (amount of solvent with respect to waste water: 0.05 by weight) was added, extraction treatment was performed at the same temperature for 10 minutes, and then allowed to stand for 30 minutes for oil-water separation.
The separated aqueous layer (waste water) was 1291 g, and its COD was 940 ppm.
The separated oil layer (xylene layer) was 58.8 g.

It is a figure which shows the relationship between extraction pH and treated water COD in an Example. It is a figure which shows the relationship between extraction temperature and treated water COD in an Example. It is a figure which shows the relationship between extraction time and oil layer height in an Example.

Claims (4)

  Wastewater containing aromatic amines is extracted with an aromatic hydrocarbon solvent under conditions of pH 5 to 8 and temperature 60 to 80 ° C., and the aromatic hydrocarbon solvent layer obtained by oil-water separation is alkalinized. Aromatic amine-containing wastewater characterized in that an aromatic hydrocarbon solvent layer having a reduced concentration of aromatic amines obtained by back extraction with an aqueous solution and oil-water separation is circulated for use in the extraction treatment of the wastewater. Processing method.   The method for treating aromatic amine-containing wastewater according to claim 1, wherein the extraction time is about 0.01 to 0.2 hours.   The method for treating aromatic amine-containing wastewater according to claim 1, wherein the aromatic amine is 4-aminodiphenylamine and / or aminophenol.   The method for treating wastewater containing aromatic amines according to claim 1, wherein the aromatic hydrocarbon solvent is toluene or xylene.

Images