JP2013107074A - Method for treating waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating waste water that allows to favorably reduce an organic substance from waste water containing cyclohexanone oxime.SOLUTION: The method for treating waste water comprises subjecting waste water containing cyclohexanone oxime to a Fenton's oxidation treatment and then subjecting the resultant product to a biological treatment.

Description

  The present invention relates to a wastewater treatment method.

  As one method for producing cyclohexanone oxime, a method is known in which cyclohexanone is ammoximation-reacted with hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst (see, for example, Patent Document 1). In Patent Document 1, the target cyclohexanone oxime is recovered by performing extraction with an organic solvent or washing with water on the reaction solution obtained by this ammoximation reaction.

JP 2006-199686 A

  Usually, water (waste water) generated by liquid separation at the time of recovery contains unreacted raw material cyclohexanone, target product cyclohexanone oxime, and other by-products. Therefore, the disposal process cannot be performed unless these organic substances are reduced and the environmental load is reduced. Microbial treatment (biological treatment) using activated sludge is widely used as a treatment method for reducing such organic matter from a large amount of wastewater discharged in factory facilities and the like.

  However, prior examination by the inventors revealed that cyclohexanone oxime contained in wastewater is an inhibiting factor for biological treatment, and it is difficult to reduce organic matter from the above-mentioned wastewater by ordinary biological treatment. It was.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the wastewater treatment method which makes it possible to reduce organic substance suitably from the wastewater containing cyclohexanone oxime.

  In order to solve the above problems, one embodiment of the present invention provides a wastewater treatment method in which wastewater containing cyclohexanone oxime is subjected to biological treatment after Fenton oxidation treatment.

  In one aspect of the present invention, the Fenton oxidation treatment includes adjusting acid to pH 1-2 by adding acid to the wastewater, adding hydrogen peroxide to the wastewater, and adding iron (II) salt to the wastewater. It is desirable to include.

  In one aspect of the present invention, the waste water is obtained by reacting cyclohexanone, hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst to obtain a reaction liquid containing cyclohexanone oxime, water and unreacted cyclohexanone. The aqueous solution is preferably an aqueous layer produced by mixing the reaction solution with an organic solvent and then separating it into an organic layer and an aqueous layer.

  In one aspect of the present invention, it is preferable that the waste water further includes an aqueous layer obtained by mixing the organic layer with water and then separating the organic layer and the aqueous layer.

  In one aspect of the present invention, it is desirable to distill a component having a boiling point equal to or lower than that of cyclohexanone from the waste water prior to the Fenton oxidation treatment.

  According to the present invention, wastewater containing cyclohexanone oxime can be suitably treated.

It is a flowchart which shows the manufacturing process of the cyclohexanone oxime of this embodiment. It is a flowchart which shows the manufacturing process of the cyclohexanone oxime of this embodiment. It is a flowchart which shows the wastewater treatment method of this embodiment.

  Hereinafter, a wastewater treatment method according to an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are flowcharts showing a process for producing cyclohexanone oxime in which wastewater that is a target of the wastewater treatment method of the present embodiment is produced. FIG. 3 is a flowchart showing the wastewater treatment method of the present embodiment.

  In one embodiment, cyclohexanone oxime is obtained by subjecting cyclohexanone to an ammoximation reaction with hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst (hereinafter sometimes simply referred to as “catalyst”) to obtain residual ammonia and cyclohexanone oxime. A reaction step (1) for obtaining a reaction solution comprising: a first distillation step (2) for distilling off residual ammonia from the reaction solution to obtain a mixture of cyclohexanone oxime and water as a bottoms; organic from the mixture Extraction process of cyclohexanone oxime with solvent to obtain cyclohexanone oxime extract (3); Washing process of washing cyclohexanone oxime extract with water (4); Distilling organic solvent from cyclohexanone oxime extract after washing To obtain crude cyclohexanone oxime as bottoms Distillation step (5); and, by distilling off residual cyclohexanone from the crude cyclohexanone oxime, it is prepared by a series of steps in the third distillation step to obtain purified cyclohexanone oxime as a bottom product (6).

  These steps may all be performed continuously, a part may be performed continuously, a part may be performed batchwise, or all may be performed batchwise, but cyclohexanone oxime From the standpoint of productivity and, furthermore, the thermal stability or quality of the resulting cyclohexanone oxime, it is preferable to carry out everything continuously.

Here, the waste liquid which is the target of the waste liquid treatment method of the present embodiment is an aqueous layer generated in the extraction step (3) and the cleaning step (4). These water layers contain organic substances such as cyclohexanone oxime, which is the target product, cyclohexanone, which is an unreacted raw material, or reaction by-products. Since wastewater containing such organic matter has a high environmental load, it is discarded after reducing the organic matter using the wastewater treatment method of the embodiment of the present invention.
Hereinafter, steps from the production of cyclohexanone oxime to the treatment of wastewater will be described in order.

  As shown in FIG. 1, in the production process of cyclohexanone oxime, a reactor 1 that performs the reaction step (1), a first distillation column 2 that performs the first distillation step (2), and an extractor that performs the extraction step (3). 3. The washing device 4 for performing the washing step (4), the second distillation column 5 for carrying out the second distillation step (5), and the third distillation column 6 for carrying out the third distillation step (6) are used in this order. A cyclohexanone oxime is produced.

  First, a predetermined amount of a reaction solution in which a catalyst is dispersed is retained in the reactor 1, and an ammoximation reaction is performed while supplying cyclohexanone 11, hydrogen peroxide 12, ammonia 13, and a solvent if necessary. The reaction liquid 14 having the same mass as that is extracted [reaction step (1)].

  Here, in extracting the reaction solution 14, it is preferable to extract only the liquid phase through a filter or the like so that the catalyst stays in the reactor 1. When extracting the catalyst together, a step of separating the catalyst from the extracted reaction solution 14 is required, and supply of the catalyst to the reactor 1 is also required. The catalyst concentration is usually 1 g / L or more and 200 g / L or less as the mass per volume of the reaction solution (catalyst + liquid phase), although it depends on the activity and reaction conditions. Further, as the reactor 1, it is preferable to use a glass-lined one or a stainless steel one from the viewpoint of preventing the decomposition of hydrogen peroxide.

  The amount of hydrogen peroxide used is usually 0.5 mol times to 3 mol times, preferably 0.5 mol times to 1.5 mol times with respect to cyclohexanone. Moreover, the usage-amount of ammonia is 1 mol times or more normally with respect to cyclohexanone, Preferably it is 1.5 mol times or more. Here, ammonia is used in excess of cyclohexanone and hydrogen peroxide so as to remain in the reaction solution, thereby increasing the conversion rate of cyclohexanone and the selectivity of cyclohexanone oxime.

  Preferable examples of the reaction solvent that can be used are alcohols having about 1 to 6 carbon atoms because the liquid phase of the reaction mixture can be easily maintained uniformly. Among them, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, s-butyl alcohol, t-butyl alcohol, and t-amyl alcohol, water, or a mixed solvent thereof. Is more preferable.

The reaction temperature is usually 50 ° C. or higher and 120 ° C. or lower, preferably 70 ° C. or higher and 100 ° C. or lower.
The reaction is preferably carried out under pressure in order to increase the solubility of ammonia in the reaction solution.

The reaction solution 14 thus obtained contains, in theory, the product cyclohexanone oxime, and the product water twice the molar amount of cyclohexanone (C ₆ H ₁₀ O + NH ₃ + H ₂ O ₂ → C ₆ H ₁₀ NOH + 2H ₂ O). ). Further, as hydrogen peroxide, an aqueous solution (hydrogen peroxide solution) of about 10% by mass or more and 70% by mass or less is usually used, and water brought in for adding hydrogen peroxide is also included. Furthermore, unreacted ammonia is contained by using ammonia excessively as described above. Further, since it is difficult to completely react cyclohexanone, unreacted cyclohexanone is also included.

Therefore, next, the reaction liquid 14 containing cyclohexanone oxime, water, ammonia and cyclohexanone is introduced into the first distillation column 2 and distilled to recover ammonia as a fraction 15 and cyclohexanone oxime as a bottoms 16. To obtain a mixture of water and cyclohexanone [first distillation step (2)].
This distillation is usually carried out at normal pressure, but may be carried out under pressure or under reduced pressure if necessary.

  The ammonia recovered as the fraction 15 is preferably recycled to the reactor 1. When an organic solvent is used in the reaction step (1), that is, when an organic solvent is supplied to the reactor 1, the organic solvent is contained in the reaction liquid 14 and introduced into the first distillation column 2. This is also preferably recovered as a fraction 15 and recycled to the reactor 1. In order to recycle the organic solvent to the reactor 1, the organic solvent used in the reaction step (1) needs to have a lower boiling point than that of cyclohexanone oxime. Depending on the type of organic solvent, water is entrained and distilled due to its azeotropic composition and the like, and this water may be recycled to the reactor 1 together. For example, in the case of t-butyl alcohol, water is distilled off in a state containing about 12% by mass or more and 18% by mass or less. Therefore, this water-containing t-butyl alcohol may be recycled to the reactor 1. In addition, ammonia is usually recycled to the reactor 1 using a compressor in a gas state, but cooled to a low temperature under pressure, dissolved in an organic solvent or a water-containing organic solvent, and recycled to the reactor 1 as a solution. May be.

  The bottoms 16 extracted from the first distillation column 2 is introduced into the extractor 3, mixed with the organic solvent 17, and then the organic layer 18 obtained by extracting cyclohexanone oxime and cyclohexanone in the bottoms 16 with the organic solvent. And the aqueous layer 19 that is the extraction residual liquid [extraction step (3)].

  The organic solvent 17 for extraction needs to be able to be separated from water, have a cyclohexanone oxime solubility, and have a lower boiling point than that of cyclohexanone oxime. Preferred examples thereof include aromatic hydrocarbons such as toluene; alicyclic hydrocarbons such as cyclohexane; aliphatic hydrocarbons such as hexane and heptane; diisopropyl ether and t-butyl methyl ether. Ethers such as ethyl acetate, aromatic hydrocarbons such as toluene, and aliphatic hydrocarbons such as cyclohexane and heptane are preferred, especially aromatic carbon such as toluene. Hydrogens are preferred.

  The usage-amount of the organic solvent 17 is 0.1 mass times or more and 2 mass times or less normally with respect to the cyclohexanone oxime in the bottoms 16, and preferably 0.3 mass times or more and 1 mass times or less. The extraction temperature is usually selected in the range from room temperature to the boiling point of the organic solvent 17, and is preferably 40 ° C or higher and 90 ° C or lower.

  In addition, as the extractor 3, a multi-stage extractable one may be used, or a so-called mixer-settler type in which a mixing part and a liquid separation part are separated may be used in one stage or multiple stages.

  The organic layer 18 from the extractor 3 is introduced into the cleaning device 4, mixed with water 20, and then an organic layer 21 obtained by removing impurities from the organic layer 18 by washing with water, and an aqueous layer formed by dissolving these impurities in water. [Washing step (4)].

  Examples of the impurities include ammonium nitrate and ammonium nitrite that can be by-produced in the reaction step (1). The amount of water 20 used for washing is usually 0.05 to 1 times the cyclohexanone oxime in the organic layer 18, and the washing temperature is usually 40 to 90 ° C. In addition, as the washer 4, one that can perform multi-stage extraction may be used as in the case of the extractor 3, or a so-called mixer-settler type with a mixing part and a liquid separation part separated may be used in one stage or multiple stages. Also good.

  The water layer 19 generated in the above-described extractor 3 and the water layer 22 generated in the cleaning device 4 are processed in a later-described wastewater treatment process.

  By introducing the organic layer 21 from the cleaning device 4 into the second distillation column 5 and distilling it, the organic solvent in the organic layer 21 can be recovered as a fraction 23, and as a bottoms 24, A crude cyclohexanone oxime containing the unreacted cyclohexanone can be obtained [second distillation step (5)].

  At that time, water contained in a dissolved or dispersed state in the organic layer 21 is recovered as a fraction 23 together with the organic solvent. This distillation is usually carried out at normal pressure to slightly reduced pressure depending on the boiling point of the organic solvent.

  The organic solvent and water recovered as the fraction 23 are at least a part of the extraction organic solvent 17 introduced into the extractor 3 and at least a part of the washing water 20 introduced into the washer 4, respectively. It is desirable to recycle. Specifically, the organic solvent and water recovered as the fraction 23 are introduced into the separator 7 and separated into an organic layer mainly containing the organic solvent 17 and an aqueous layer mainly containing the water 20, and organic The layer may be introduced into the extractor 3 and the aqueous layer may be introduced into the cleaning device 4.

  By introducing the crude cyclohexanone oxime extracted as the bottoms 24 of the second distillation column 5 into the third distillation column 6 and distilling it, the cyclohexanone can be recovered as the fraction 25 and the bottoms 26, a purified cyclohexanone oxime from which cyclohexanone is removed or reduced can be obtained [third distillation step (6)].

  This distillation is usually performed at a temperature of 140 ° C. or lower under a reduced pressure of 10 kPa or lower. The purified cyclohexanone oxime thus obtained is excellent in thermal stability and can be suitably used as a raw material for gas phase Beckmann rearrangement. From the viewpoint of suppressing side reactions in the gas phase Beckmann rearrangement, the distillation conditions may be adjusted so that the concentration of cyclohexanone in the purified cyclohexanone oxime is 1% by mass or less, preferably 0.5% by mass or less.

  The cyclohexanone recovered as the fraction 25 is preferably recycled to the reactor 1. In addition, if accumulation of impurities in the fraction 25 becomes remarkable due to long-term operation or the like, at least a part may be purified by rectification or the like.

  In order to further enhance the thermal stability of the purified cyclohexanone oxime obtained by the above process, the washing step (4) is devised. Specifically, the washing step (4) is changed to the first washing step with an aqueous solution containing a base ( It is preferable to perform a two-stage washing including 4a) and a second washing step (4b) with normal water substantially free of base (so-called distilled water, deionized water, purified water, etc.). At this time, the aqueous solution containing the base used in the first washing step (4a) is prepared by mixing the aqueous layer generated in the second washing step (4b) with the base, thereby washing step (4). The amount of the water layer generated as a whole can be reduced. Moreover, the water which is a fraction of a 2nd distillation process can be used as water which does not contain the base used by a 2nd washing | cleaning process (4b) substantially.

  Furthermore, in order to reduce the loss of cyclohexanone oxime in the above process, cyclohexanone oxime that can be contained in a trace amount in the aqueous layer discharged in the extraction step (3) and the aqueous layer discharged in the washing step (4) is reduced. It is desirable to extract and recover with an organic solvent. The organic solvent used here can be the same as that used in the extraction step (3). Therefore, it is desirable that the organic solvent for use in the extraction step (3) is first used for recovering a trace amount of cyclohexanone oxime from the aqueous layer and then used in the extraction step (3). The cyclohexanone oxime is preferably recovered by multistage extraction.

  FIG. 2 is a flowchart schematically showing an example of the above-described two-step cleaning and cyclohexanone oxime recovery, and the portion surrounded by a broken line in FIG. 1 can be replaced with the flowchart of FIG.

  That is, first, regarding the above-described two-stage cleaning, the organic layer 18 from the extractor 3 is introduced into the first cleaner 4a, mixed with the aqueous solution 20a containing the base, and then separated into the organic layer 21a and the aqueous layer 22a. [First cleaning step (4a)]. Here, examples of the base contained in the aqueous solution 20a include alkali metal hydroxides, carbonates, and ammonia. Specific examples of the alkali metal hydroxide and carbonate include potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate. The density | concentration in the aqueous solution 20a is 0.01-2N normally, Preferably it is 0.05-0.5N. The washing temperature is preferably 60 to 90 ° C., and the amount of the aqueous solution 20a containing the base is preferably 0.2 to 2 times by mass with respect to cyclohexanone oxime in the organic layer 18. Next, the organic layer 21a from the first washer 4a is introduced into the second washer 4b, mixed with water 20b substantially free of base, and then separated into an organic layer 21b and an aqueous layer 22b [first Two washing steps (4b)]. The amount of water 20b that does not substantially contain a base is preferably 0.1 to 10 times the mass of cyclohexanone oxime in the organic layer 21b. And the organic layer 21b is introduce | transduced into the 2nd distillation column 5, and distillation is performed. The aqueous layer 22b is mixed with a base or an aqueous solution 27 thereof, and this mixed liquid is recycled as at least a part of the aqueous solution 20a containing the base introduced into the first cleaning device 4a. The water layer (water 20) from the fraction 23 of the second distillation column 5 can be used as at least part of the water 20b substantially free of base introduced into the second washer 4b.

  Next, regarding the cyclohexanone oxime recovery described above, the aqueous layer 19 from the extractor 3 and the aqueous layer 22a from the first cleaning device 4a are introduced into the recovery device 8 and mixed with the organic solvent 17, and then the aqueous layer 19 and water A small amount of cyclohexanone oxime in the layer 22a is separated into an organic layer 28 obtained by extraction with the organic solvent 17 and an aqueous layer 29 as an extraction residual liquid. Then, the organic layer 28 is introduced into the extractor 3 and used as at least a part of an organic solvent for extracting cyclohexanone oxime from the bottoms 16 of the first distillation column 2. Moreover, the water layer 29 is processed as waste water. As at least a part of the organic solvent 17 introduced into the recovery unit 8, the organic layer (organic solvent 17) from the fraction 23 of the second distillation column 5 can be used. In addition, as the extractor 3 and the washer 4, the recoverer 8 may be a multistage extractable one, or a so-called mixer-settler type in which the mixing part and the liquid separation part are separated from one stage to the other. It may be used in multiple stages.

  The water layer 29 generated in the above-described recovery device 8 is treated in a wastewater treatment process described later.

Further, in order to recover cyclohexanone oxime that can be contained in a trace amount in the aqueous layer discharged in the washing step (4), the aqueous layer is separated from cyclohexanone oxime, which is the bottoms of the first distillation step (2), and water. It is also advantageous to subject it to the extraction step (3) together with the mixed solution. At this time, if this extraction step (3) is performed by multi-stage extraction, the aqueous layer discharged from the extraction step (3) can be made substantially free of cyclohexanone oxime and need not be recovered. It is advantageous.
As described above, cyclohexanone oxime is produced.

  On the other hand, the water layer 19 and the water layer 22 in FIG. 1 or the water layer 29 in FIG. 2 are treated in the waste water treatment step shown in FIG. These water layers contain organic substances such as cyclohexanone oxime, which is the target product, cyclohexanone, which is an unreacted raw material, or reaction by-products. According to studies by the inventors, cyclohexanone oxime contained in such an aqueous layer (waste water) becomes an inhibitory factor for microbial treatment in activated sludge used for ordinary waste water treatment, and it is difficult to reduce organic matter by microbial treatment. It turns out that.

  Therefore, in the wastewater treatment method of this embodiment, wastewater treatment is performed by performing biological treatment after performing Fenton oxidation treatment on wastewater containing cyclohexanone oxime. Specifically, acid is added to wastewater to adjust to pH 1-2, hydrogen peroxide is added, and then iron (II) salt is further added to perform Fenton oxidation treatment, and then a base is added to adjust the pH to 4 or more. Biological treatment of wastewater raised to 10 or less. Prior to the Fenton oxidation treatment, components having a boiling point lower than the boiling point of cyclohexanone (that is, 155.65 ° C. or lower) are distilled from the wastewater to reduce the load of the subsequent wastewater treatment process. . The “component having a boiling point lower than that of cyclohexanone” includes cyclohexanone and components having a boiling point lower than that of cyclohexanone.

  As shown in FIG. 3, in such a wastewater treatment process, the Fenton oxidation treatment of the distillation tower 31, the water layer 19, 22, or 29 that distills the low boiling point component contained in the water layer 19, 22, or 29 is performed. An oxidation treatment tank 32 to be performed, a neutralization tank 33 to adjust pH by adding a base, and a sludge tank 34 to perform biological treatment are used in this order to treat waste water.

  First, the water layer 19, 22 or 29 discharged in the above-described cyclohexanone oxime production process is introduced into a distillation column 31 and distilled, and a component having a boiling point equal to or lower than the boiling point of cyclohexanone (low-boiling component 41) is obtained as a fraction. ) Is recovered and waste water containing cyclohexanone oxime and cyclohexanone is obtained as bottoms 42.

Next, the bottoms 42 is introduced into the oxidation treatment tank 32 and Fenton oxidation treatment is performed.
In the oxidation treatment tank 32, first, an acid 43 and hydrogen peroxide 44 are added to the introduced bottom liquid 42 (that is, waste water). As the acid 43, any organic acid or inorganic acid can be used as long as the pH of the wastewater can be lowered to 1 or 2, but it increases the process load in the Fenton oxidation treatment and biological treatment described later. Therefore, it is preferable to use an inorganic acid.
As the inorganic acid, sulfuric acid is preferable. The order in which the acid 43 and the hydrogen peroxide 44 are added may be either first or simultaneously.

  As the hydrogen peroxide 44, an aqueous solution (hydrogen peroxide solution) having a normal concentration of about 10% by mass to 70% by mass can be used.

Here, by reducing the pH of the wastewater to 1 to 2, the cyclohexanone oxime contained in the wastewater undergoes a hydrolysis reaction in the presence of an acid catalyst and decomposes into cyclohexanone and hydroxylamine (C ₆ H ₁₀ NOH + H _{2 O → C 6 H 10 O} + NH 2 OH). As described above, cyclohexanone oxime is an inhibitor of biological treatment, but the total amount of cyclohexanone oxime can be reduced favorably by the hydrolysis.

Further, in the oxidation treatment tank 32, iron (II) salt 45 is added to the waste water. By iron (II) salt and hydrogen peroxide 44 (Fenton's reagent) is reacted, resulting OH radicals ^{_{(H 2 O 2 + Fe 2+}} → Fe 3+ + OH - + · OH), organic material wherein OH radicals contained in the waste water Is oxidized (Fenton oxidation treatment).

As the iron (II) salt 45, various salts can be used as long as they are water-soluble, but it is preferable that the counter ion is in common with the acid counter ion used in the above pH adjustment. As described above, since sulfuric acid is suitably used as the acid for adjusting the pH, the iron (II) salt 45 is preferably iron (II) sulfate.
The amount of hydrogen peroxide used is preferably 0.01 to 20% by mass, more preferably 0.05 to 5% by mass with respect to the waste water.
The amount of iron (II) salt used is preferably 0.0001 to 1 mol times, more preferably 0.0005 to 0.5 mol times with respect to hydrogen peroxide.
The Fenton oxidation treatment is preferably stirred at a temperature of 50 to 150 ° C. for 0.1 to 10 hours after adding the iron (II) salt 45.

  By such Fenton oxidation treatment, cyclohexanone and reaction by-products contained in the wastewater are oxidized and decomposed. For cyclohexanone oxime, for example, the total amount can be controlled to 1 ppm or less in the wastewater. In this way, waste water that has undergone Fenton oxidation treatment is obtained as the bottoms 46 of the oxidation treatment tank 32.

Further, in the neutralization tank 33, a base 47 is added to adjust the pH of the bottoms 46. As the base 47, either an organic base or an inorganic base can be used as long as the pH of the wastewater can be raised to 4 or higher. However, in order not to increase the process load in the biological treatment described later, the inorganic base is used. Is preferably used. As the inorganic base, for example, an aqueous sodium hydroxide solution is preferably used.
The pH of the waste water after adding the base is preferably 4 or more and 10 or less.

  When treating wastewater containing high-concentration organic matter, the method using the above-described Fenton oxidation treatment can reduce the processing cost compared to the method using physicochemical treatment such as aggregation, precipitation, filtration, and adsorption. Is possible. Furthermore, in the wastewater treatment method of this embodiment, since a part of the organic matter contained in the wastewater is decomposed by the Fenton oxidation treatment, even if the amount of the organic matter contained in the wastewater varies, the amount of Fenton reagent or the Fenton oxidation treatment By changing the treatment time, waste water reduced to an amount of organic substances suitable for biological treatment can be obtained.

For example, as an indicator of the amount of organic substances contained in wastewater, chemical oxygen demand (COD) and total organic carbon (TOC) are used. In the Fenton oxidation treatment, the COD and TOC values are lower than the threshold value by adjusting the processing time of the Fenton oxidation treatment, the amount of reagent to be used, and other treatment conditions using these COD and TOC values as a reference (threshold value). Can be controlled. Thereby, after reducing the value of COD and TOC of wastewater until it becomes a value suitable for biological treatment, the operation | movement of sending liquid to the latter sludge tank 34 is attained.
The “threshold value” is the maximum value at which biological treatment can be performed without inhibiting microbial reactions.

Next, the bottoms 48 discharged from the neutralization tank 33 is introduced into the sludge tank 34, and biological treatment is performed. Activated sludge is stored in the sludge tank 34, and it is good also as having the stirring equipment which stirs activated sludge, and the aeration equipment which performs aeration processing. Since the cyclohexanone oxime contained in the water layer 19, 22 or 29 is well reduced by the above-mentioned Fenton oxidation treatment, it is preferable to carry out the organic treatment by appropriately performing the biological treatment without inhibiting the microbial reaction. Can be reduced.
“Biological treatment” is a method of treating wastewater using the purification action of microorganisms such as bacteria, and includes an activated sludge method and a biofilm method.
“Activated sludge” refers to a flocculent lump that is produced when wastewater is treated for a long time in an aerated state, and is composed of suspended matter, bacteria, protozoa, and the like in the wastewater.

In this way, waste water with reduced organic matter can be obtained as the bottomed liquid 49 of the sludge tank 34, and a dumping process can be performed.
As described above, wastewater treatment is performed.

  According to the wastewater treatment method as described above, wastewater containing cyclohexanone oxime can be suitably treated.

  In the present embodiment, waste water (the above-mentioned water layer 19 described above) generated in a factory facility for producing cyclohexanone oxime by reacting cyclohexanone, hydrogen peroxide, and ammonia (ammoximation reaction) in the presence of a titanosilicate catalyst. , 22, or 29) has been described as being processed, but is not limited thereto.

  For example, in the production process for producing cyclohexanone oxime by another method, when the water layer separated from the reaction solution is discarded, the waste water treatment method of the present invention is also used when the water layer contains cyclohexanone oxime. It is possible to apply. That is, also for an aqueous layer (waste liquid) generated by another method for producing cyclohexanone oxime, waste water treatment can be suitably performed by subjecting the aqueous layer to Fenton oxidation treatment in advance and then biological treatment. .

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. The combinations of the components shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[1. Verification of inhibition of biological treatment]
First, we examined the inhibition of biological treatment due to the presence of cyclohexanone oxime.

  In the examples, cyclohexanone oxime was added to pure water to prepare cyclohexanone oxime aqueous solutions (hereinafter referred to as simulated waste water) having concentrations of 0.1 mass%, 0.5 mass%, and 1.0 mass%.

  The simulated wastewater is subjected to biological treatment using activated sludge, and the amount of nitrogen contained in the simulated wastewater at the start of treatment and 21 hours after the start of treatment is measured. The amount of nitrogen decreased from (the amount of nitrogen decrease) was measured. The activated sludge used is for fixing nitrogen in wastewater in the form of nitrate. Biological treatment was performed by mixing 1 L of running water drainage sampled from the activated sludge tank of the actual machine, 1 L of activated mud slurry, and 90 ml of simulated wastewater, and maintaining at 32 ° C. while stirring.

Based on the obtained measured value, nitrification inhibitory property indicating the degree of inhibition of biological treatment was calculated from the following formula. The larger the nitrification inhibitory value, the more biological treatment is inhibited. The calculation results are shown in Table 1 below.
Nitrification inhibition (%) = [(XY) / X] × 100
(X: Nitrogen reduction amount when treating simulated wastewater with 0% concentration of cyclohexanone oxime, Y: Nitrogen reduction amount when treating simulated wastewater with each concentration)

  The amount of nitrogen contained in the wastewater was measured according to JIS K-0102 (factory drainage test method).

  As a result of verification, it was confirmed that nitrification was inhibited (biological treatment was inhibited) as the concentration of cyclohexanone oxime increased.

[2. Verification of Fenton oxidation effect]
Next, the effect of wastewater treatment by Fenton oxidation treatment was verified.
In the embodiment, actual waste water generated in a factory facility for producing cyclohexanone oxime by reacting cyclohexanone, hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst (ammoximation reaction) (the above-described aqueous layers 19, 22). Or corresponding to 29), the effect of the present invention was verified by measuring the values of COD and TOC and the concentration of cyclohexanone oxime.

(Measurement of pH)
As the pH of the wastewater, an average value measured twice using a pH meter (model number D-53S, manufactured by HORIBA Ltd.) was adopted.

(Measurement of cyclohexanone oxime)
Analysis was performed using gas chromatography, and the concentration of cyclohexanone oxime was calculated by area percentage.

(Sample adjustment for COD and TOC measurement)
The wastewater COD and TOC were added to 0.3 g of a 1% decomposing enzyme (Aqua Super, manufactured by Mitsubishi Gas Chemical Co., Ltd., main component: catalase) solution in 100 g of wastewater after the Fenton oxidation treatment by the method described later. It measured about the sample liquid obtained by stirring for 1 hour.

(Measurement of COD)
The COD of wastewater was measured according to JIS K-0102 (factory drainage test method).

(Measurement of TOC)
The TOC of wastewater was measured according to JIS K-0102 (factory drainage test method).

Example 1
After mixing 200.1 g of waste water (cyclohexanone oxime concentration is 640 ppm) and 0.84 g of 98% sulfuric acid to adjust to pH = 1.6 (27 ° C.), the temperature of the waste water was raised to 90 ° C. The wastewater is 1.19 g of 60% hydrogen peroxide (about 0.36% by mass as hydrogen peroxide relative to the wastewater) and 0.59 g of iron (II) sulfate heptahydrate (about 0.1% relative to hydrogen peroxide). 1 mol ratio) was further added, and the mixture was stirred at 90 ° C. for 1 hour, and then cooled until the temperature of the wastewater became 40 ° C. or lower. 0.69 g of sodium hydroxide is added to the cooled wastewater and stirred, and adjusted to pH> 4, so that it can be used for wastewater (the above-mentioned canned liquid 48) before being fed into the sludge tank after the Fenton oxidation treatment. A treatment liquid was obtained.

(Examples 2-9)
A treatment liquid was prepared in the same manner as in Example 1 except that the treatment conditions of the iron (II) sulfate amount, the hydrogen peroxide amount, and the stirring time at 90 ° C. were changed to the conditions described in Tables 1 and 2 below. Got.

(Comparative Example 1)
A treatment solution was obtained in the same manner as in Example 1 except that iron (II) sulfate was not added.

(Comparative Example 2)
A treatment liquid was obtained in the same manner as in Example 1 except that 0.21 g of 98% sulfuric acid was mixed with the waste water and the pH was adjusted to 2.9 (27 ° C.).

(Comparative Example 3)
A treatment solution was obtained in the same manner as in Example 1 except that 0.06 g of 98% sulfuric acid was mixed with the waste water and the pH was adjusted to 3.8 (27 ° C.).

  Tables 2 and 3 below show the respective treatment conditions and the measurement results of the concentrations of COD, TOC, and cyclohexanone oxime.

  As a result of measurement, in Examples 1 to 9, it was confirmed that COD, TOC and cyclohexanone oxime were significantly reduced from the waste water stock solution. Furthermore, compared with the comparative example 1 which does not add iron sulfate (II) and does not perform a Fenton oxidation process, the further reduction | decrease of COD, TOC, and cyclohexanone oxime has been confirmed.

  According to the present invention, since cyclohexanone oxime can be reduced below the detection limit from waste water before biological treatment, it is possible to suitably carry out biological treatment without being inhibited by cyclohexanone oxime. You can expect to be there. In addition, since the organic matter in the wastewater is decomposed by performing the Fenton oxidation treatment, it is possible to reduce the load of biological treatment in the subsequent stage.

It was also confirmed that the values of COD and TOC can be suitably controlled by controlling the amount of hydrogen peroxide and the amount of iron (II) sulfate used and adjusting the treatment time.
From these results, the usefulness of the present invention was confirmed.

  According to the present invention, wastewater containing cyclohexanone oxime can be suitably treated.

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... 1st distillation tower, 3 ... Extractor, 4 ... Washing machine, 4a ... 1st washing machine, 4b ... 2nd washing machine, 5 ... 2nd distillation tower, 6 ... 3rd distillation tower, DESCRIPTION OF SYMBOLS 7 ... Separator, 8 ... Recovery machine, 11 ... Cyclohexanone, 12, 44 ... Hydrogen peroxide, 13 ... Ammonia, 14 ... Reaction liquid, 15, 23, 25 ... Fraction, 17 ... Organic solvent, 18, 21, 21a, 21b, 28 ... organic layer, 19, 22, 22a, 22b, 29 ... water layer, 20, 20b ... water, 20a ... aqueous solution, 27 ... base or its aqueous solution, 31 ... distillation tower, 32 ... oxidation treatment tank, 33 ... neutralization tank, 34 ... sludge tank, 41 ... low boiling point component, 16, 24, 26, 42, 46, 48, 49 ... bottoms, 43 ... acid, 45 ... iron (II) salt, 47 ... base

Claims (5)

  A wastewater treatment method in which a wastewater containing cyclohexanone oxime is subjected to biological treatment after Fenton oxidation treatment.   The said Fenton oxidation process includes adding acid to the said wastewater, adjusting to pH 1-2, adding hydrogen peroxide to the said wastewater, and adding an iron (II) salt to the said wastewater. Wastewater treatment method.   The waste water is reacted with cyclohexanone, hydrogen peroxide and ammonia in the presence of a titanosilicate catalyst to obtain a reaction solution containing cyclohexanone oxime, water and unreacted cyclohexanone, and then the reaction solution is mixed with an organic solvent. The wastewater treatment method according to claim 1, wherein the wastewater treatment method is an aqueous layer produced by mixing into an organic layer and an aqueous layer after mixing.   The wastewater treatment method according to claim 3, wherein the wastewater further includes an aqueous layer obtained by mixing the organic layer with water and then separating the organic layer into an aqueous layer.   The wastewater treatment method according to any one of claims 1 to 4, wherein a component having a boiling point lower than that of cyclohexanone is distilled from the wastewater prior to the Fenton oxidation treatment.

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