A method for treating waste water produced in the industrial synthesis of clethodim

Abstract

The present application relates to the field of wastewater treatment, and in particular to a treatment method for wastewater generated in the industrial synthesis of clethodim. The wastewater generated in the synthesis of each intermediate in the industrial synthesis of clethodim is pretreated, the pretreated wastewater is mixed and adjusted to be acidic to obtain acidic mixed wastewater, the acidic mixed wastewater is subjected to extraction separation of impurities under acidic conditions, the wastewater after extraction is subjected to light removal treatment, the wastewater after light removal is subjected to decolorization treatment, the wastewater after decolorization is adjusted to be neutral and subjected to evaporation desalination treatment, and standard industrial sodium chloride and low-concentration wastewater are obtained. The high-salt and high-COD wastewater of clethodim is converted into low-concentration biochemical wastewater and superior industrial sodium chloride, the process is stable, simple to operate and suitable for industrialization.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically a method for treating wastewater generated during the industrial synthesis of clethodim. Background Technology

[0002] Clethodim is an ACCase inhibitor, a systemic herbicide applied foliar in application. It exhibits excellent selectivity, showing strong killing activity against grassy weeds while remaining safe for dicotyledonous crops. After foliar application, it is rapidly absorbed through the leaves and translocated to the meristem. In sensitive plants, it inhibits the biosynthesis of branched-chain fatty acids and flavonoids, disrupting cell division and inhibiting the activity of plant meristems, thus slowing plant growth. It is primarily used to control annual and perennial grassy weeds and free-growing cereal crops such as barnyard grass and silvergrass in broadleaf fields. In resistant plants, it rapidly degrades and loses its activity.

[0003] Equations for the synthesis and side reactions of clethodim:

[0004]

[0005] The process generates three streams of high-salt, high-COD wastewater.

[0006] Process side reactions:

[0007] (1) Acidic decomposition of methyl acetoacetate:

[0008]

[0009] (2) Keto decomposition of methyl acetoacetate:

[0010]

[0011] (3) Propionyl chloride hydrolysis:

[0012]

[0013] Derivatization reaction formula of clethodim byproducts:

[0014] Byproduct acetic acid derivatization reaction formula:

[0015]

[0016] Byproduct propionic acid derivatization reaction formula:

[0017]

[0018] The industrial production of clethodim generates highly saline, high-COD, and high-ammonia-nitrogen odorous wastewater. Direct discharge of this wastewater without treatment can severely impact soil and natural water bodies, causing irreversible harm to the natural environment and human health. Currently, there are few existing technologies for treating this highly saline, high-COD, high-ammonia-nitrogen, and odorous wastewater from clethodim production. Summary of the Invention

[0019] The purpose of this invention is to provide a method for treating wastewater generated during the industrial synthesis of clethodim. The method involves separating organic pollutants and odorous substances from the wastewater. After pretreatment, the wastewater is extracted with n-butanol under acidic conditions to separate impurities. Following extraction, the wastewater undergoes a distillation process to remove light pollutants. During this process, water-soluble n-butanol can decompose residual acetic acid and propionic acid in the wastewater into n-butyl acetate and n-butyl propionate under acidic conditions, which are then separated. The wastewater is then subjected to resin adsorption, neutralization, and MVR (Mechanical Vapor Recompression) evaporation for desalination, yielding high-quality industrial sodium chloride. The resulting low-concentration wastewater is directly subjected to biochemical treatment and discharged in compliance with standards.

[0020] To achieve the above objectives, the present invention adopts the following technical solution:

[0021] A method for treating wastewater generated during the industrial synthesis of clethodim involves pretreating the wastewater generated from the synthesis of various intermediates in the industrial synthesis of clethodim separately, mixing the pretreated wastewater and adjusting it to acidic conditions to obtain acidic mixed wastewater, extracting and separating impurities from the acidic mixed wastewater under acidic conditions, removing light pollutants from the extracted wastewater, decolorizing the wastewater after removing light pollutants, adjusting the decolorized wastewater to neutral conditions, and then evaporating and desalinizing it to obtain industrial sodium chloride that meets the standards and low-concentration wastewater that can be directly biodegraded.

[0022] Wastewater pretreatment generated during intermediate synthesis is as follows:

[0023] (1) The wastewater generated during the synthesis of intermediate 6-ethylthio-4-hydroxy-2-heptanone was adjusted to alkaline and then subjected to continuous distillation to obtain alkaline pretreated wastewater 1.

[0024] (2) Wastewater generated during the synthesis of intermediate 6-(2-(ethylthio)propyl)-2-oxo-4-(propionyloxy)cyclohex-3-en-carboxylic acid ethyl ester was treated by continuous distillation to obtain pretreated wastewater 2;

[0025] (3) Wastewater generated during the synthesis of intermediate 5-(2-(ethylthio)propyl)-3-hydroxy-2-propionyl-2-en-cyclohexanone was treated by continuous distillation to obtain pretreated wastewater 3;

[0026] (4) The alkaline pretreated wastewater 1, pretreated wastewater 2, pretreated wastewater 3, and MVR desalination mother liquor are introduced into the acidification tank to adjust the pH to acidic, and acidic mixed wastewater is obtained.

[0027] (5) The acidic mixed wastewater and the extraction solvent are respectively fed into a continuous extraction separator for extraction and separation. The aqueous phase is fed into the next stage of continuous extraction. The acidic mixed wastewater is extracted three times in a row, and the extraction solvent is fed into the solvent recovery system to recover the solvent.

[0028] (6) The wastewater obtained in step (5) is fed into a continuous distillation column for light removal;

[0029] (7) The wastewater after light removal in step (6) is decolorized by a resin adsorption tower;

[0030] (8) The decolorized wastewater enters the neutralization kettle and the pH is adjusted to neutral to obtain neutralized wastewater;

[0031] (9) The neutralized wastewater is subjected to evaporation and desalination treatment to obtain industrial sodium chloride. The MVR desalination mother liquor is reused.

[0032] Acidic mixed wastewater, distilled into low-concentration wastewater;

[0033] (10) Distilled low-concentration wastewater is diluted and then enters the biochemical tank for further treatment.

[0034] The continuous distillation process in step (1) is as follows: distillation to a kettle temperature of 105-106℃ and a column top temperature of 97-98℃ to obtain alkaline pretreated wastewater 1;

[0035] The continuous distillation process in step (2) is as follows: distillation to a kettle temperature of 104-105℃ and a column top temperature of 94-95℃ to obtain neutral pretreated wastewater 2;

[0036] The continuous distillation process in step (3) is as follows: distillation to a kettle temperature of 103-104℃ and a column top temperature of 92-94℃ to obtain acidic pretreated wastewater 3.

[0037] Step (1) Adjust the wastewater generated during the synthesis of intermediate 6-ethylthio-4-hydroxy-2-heptanone to pH ≥ 12.

[0038] Step (4) The pretreated wastewater is mixed and adjusted to pH ≤ 1.5 to obtain acidic mixed wastewater; preferably, the pH is 0.5 to 1.5.

[0039] Step (5) The extraction solvent is one or more of n-butanol, pentanol, n-butyl acetate, n-butyl propionate, and methyl isobutyl ketone; preferably n-butanol; the mass ratio of acidic mixed wastewater to solvent is 1:0.3 to 1:1, preferably 1:0.3.

[0040] Step (6): The bottom temperature of the continuous light distillation column is 105-106℃, and the top temperature is 95-96℃.

[0041] In step (7), the adsorption resin is either cationic L16G or anionic XDA-1, with cationic adsorption resin L16G being preferred.

[0042] Step (8) The decolorized wastewater enters the neutralization tank and the pH is adjusted to 6.5-7.5 to obtain neutralized wastewater.

[0043] Step (9) The MVR desalination produces low-concentration wastewater with COD < 2000 mg / L, preferably up to 1000-2000 mg / L; NH3-N < 30 mg / L; TN < 50 mg / L.

[0044] Step (10) Detect the low concentration wastewater from desalination distillation diluted to below 2000 mg / L, NH3-N < 30 mg / L; TN < 50 mg / L, conductivity controlled within 10000 mg / L, pH adjusted to between 6 and 9, introduce into the biological treatment tank, control the wastewater to aerobic sludge settling ratio at 20-30%, turn on aeration for biological treatment.

[0045] Wastewater is discharged after undergoing biological treatment to meet local wastewater discharge standards (Liaoning Province Integrated Wastewater Discharge Standard DB21 / 1627-2008).

[0046] This invention utilizes the chemical properties of organic components in high-salt, high-COD wastewater from clethodim production to conduct targeted pretreatment. After pretreatment, the wastewater is mixed and acidified for extraction, separating tar, organic acids, and organic impurities. The separated wastewater is then decolorized via resin adsorption, neutralized, and subjected to MVR desalination, effectively removing malodorous odors and organic impurities while recovering high-grade industrial sodium chloride. This solves the problem of difficult-to-manage high-salt, high-COD, and malodorous wastewater during clethodim production, offering advantages of safety, greenness, and environmental friendliness. Low-concentration wastewater, after biochemical treatment, meets local wastewater discharge standards before being discharged (complying with Liaoning Province Integrated Wastewater Discharge Standard DB21 / 1627-2008).

[0047] Advantages of this invention:

[0048] This invention pretreats different wastewater streams using different reactions based on their different components. Then, through continuous extraction, continuous distillation, resin adsorption, and MVR equipment, the wastewater is continuously treated to convert high-salt, high-COD wastewater into low-concentration biochemical wastewater and high-grade industrial sodium chloride. The process is stable, simple to operate, and suitable for industrial application.

[0049] Specifically, this application sets the following pH values ​​for each stage: For intermediate I, 6-ethylthio-4-hydroxy-2-heptanone wastewater, the pH is adjusted to ≥12 to release dissolved alkaline organic compounds such as triethylamine and hexahydropyridine, which are then separated via a distillation column. For the acidic mixed wastewater from n-butanol extraction, the pH is adjusted to ≤1.5. This serves two purposes: first, to release organic acids from the wastewater and dissolve them in n-butanol, thus separating the organic acids; second, during the light removal process in the acidic distillation column, the organic acids react with n-butanol to form esters such as n-butyl acetate and n-butyl propionate, further separating the organic acids from the wastewater. For the neutralization wastewater before MVR, the pH is adjusted to 6.5–7.5 to neutralize the wastewater, resulting in the discharge of neutral biochemical wastewater and preventing corrosion of the equipment by the acidic wastewater. The distillation conditions in this application are designed to separate organic components from wastewater; reduce the organic content in wastewater to avoid the negative impact of high COD, ammonia nitrogen, and total nitrogen levels on biochemical wastewater; and prevent organic matter from affecting the quality of the byproduct sodium chloride. The extraction settings in this application aim to release organic acids from the wastewater into the solvent n-butanol for extraction, thus separating the organic acids. The organic acids are then reacted with the extraction solvent n-butanol to form esters such as n-butyl acetate and n-butyl propionate, further separating the organic acids. The extraction solvent n-butanol also extracts impurities and tar from the wastewater. The resin selection in this application aims to adsorb colored groups in the wastewater, thus decolorizing it. In this application, pretreated wastewater 1 is alkaline, pretreated wastewater 2 is neutral, and pretreated wastewater 3 is acidic. Mixing these pretreated wastewaters reduces hydrochloric acid consumption. Detailed Implementation

[0050] The following examples further illustrate specific embodiments of the present invention. It should be noted that the specific embodiments described herein are merely for illustration and explanation and are not intended to limit the scope of the present invention.

[0051] This invention, particularly through pH-controlled distillation separation of organic components, separates organic components in wastewater under different pH conditions. Organic impurities and byproducts from each wastewater stream are extracted and analyzed with n-butanol. After mixing, the resulting high-salt acidic wastewater undergoes light-removal treatment. Water-soluble n-butanol can decompose residual acetic acid and propionic acid in the wastewater into n-butyl acetate and n-butyl propionate via a distillation column. After resin adsorption, neutralization, and MVR treatment, high-quality industrial sodium chloride and biodegradable wastewater are obtained.

[0052] Biochemical method: Dilute the COD of the wastewater to below 2000 mg / L, control the conductivity to below 10000 mg / L, and adjust the pH to between 6 and 9; place the prepared water sample in a graduated cylinder, inoculate with a certain amount of aerobic sludge until the settling ratio reaches 20-30%, turn on aeration to conduct the experiment; detect COD at 24h-168h and calculate the removal rate.

[0053] The analysis of industrial sodium chloride shall be performed in accordance with the analytical method of industrial salt GB / T5462-2015.

[0054] Example 1

[0055] Equations for the synthesis and side reactions of clethodim:

[0056]

[0057] The process generates three streams of high-salt, high-COD wastewater.

[0058] Process side reactions:

[0059] (1) Acidic decomposition of methyl acetoacetate:

[0060]

[0061] (2) Keto decomposition of methyl acetoacetate:

[0062]

[0063] (3) Propionyl chloride hydrolysis:

[0064]

[0065] ① Take the 6-ethylthio-4-hydroxy-2-heptanone synthesis wastewater produced by the above process, adjust the pH to 12.5, distill to a kettle temperature of 106.0℃ and a column top temperature of 97.7℃, distill to remove the odorous solvent and incinerate to obtain alkaline pretreated wastewater 1, and detect the changes in COD, ammonia nitrogen and total nitrogen before and after treatment.

[0066]

[0067] ② The neutral wastewater generated during the synthesis of ethyl 6-(2-(ethylthio)propyl)-2-oxo-4-(propionyloxy)cyclohex-3-en-carboxylate produced by the above process was distilled to a boil temperature of 104.7℃ and a top temperature of 94.5℃ to obtain neutral pretreated wastewater 2. The changes in COD, ammonia nitrogen, and total nitrogen before and after treatment were detected. The solvent was removed by distillation to obtain toluene and water. After separation, the toluene was recovered, and the aqueous phase was returned to the distillation column for re-distillation treatment.

[0068]

[0069] ③ The 5-(2-(ethylthio)propyl)-3-hydroxy-2-propionyl-2-en-cyclohexanone synthesis wastewater produced by the above process was distilled to a boiling point of 103.8℃ and a top temperature of 93.7℃ to obtain acidic pretreated wastewater 3. The changes in COD, ammonia nitrogen, and total nitrogen before and after treatment were detected. The solvent removed by distillation was petroleum ether and water. After separation, the petroleum ether was recovered, and the aqueous phase was returned to the distillation column for re-distillation treatment.

[0070]

[0071] ④ The pretreated wastewater 1, pretreated wastewater 2, pretreated wastewater 3 and the produced MVR desalination mother liquor are introduced into the acidification tank through a metering pump to adjust the pH to 0.75, thus obtaining acidic mixed wastewater.

[0072] ⑤ The above-mentioned acidic mixed wastewater and n-butanol are fed into a 3-stage continuous extraction separator at a mass ratio of 1:0.3 for extraction and separation. The aqueous phase enters the next stage of continuous extraction. The acidic mixed wastewater is extracted three times in a row, and the n-butanol enters the n-butanol recovery system to recover the n-butanol.

[0073] ⑥ The wastewater from the previous extraction step is fed into a continuous distillation column for light removal. The bottom temperature of the column is 105.9℃ and the top temperature is 95.4℃.

[0074] ⑦ The acidic wastewater after light removal is decolorized by a cation exchange resin (L16G) adsorption tower.

[0075] ⑧ The resin-adsorbed wastewater enters the neutralization reactor. The pH of the wastewater is adjusted to 6.8 by an online pH meter and a liquid alkali adjustment chain, resulting in neutralized wastewater.

[0076] ⑨ The neutralized wastewater is pumped into the MVR desalination equipment to obtain industrial sodium chloride. The MVR desalination mother liquor is reused in ④ acidic mixed wastewater, and the distillation fraction is low-concentration wastewater.

[0077]

[0078] ⑩ Distilled low-concentration wastewater is diluted with 50% water and then enters the biological treatment tank for biological treatment.

[0079] Biochemical methods: Dilute the COD of the wastewater to below 2000 mg / L and control the conductivity to 10000.

[0080] Adjust the pH to 7.5 if the concentration is below mg / L; place the prepared water sample in a graduated cylinder, inoculate with aerobic sludge until the settling ratio reaches 20-30%, turn on aeration to conduct the experiment; detect COD at 24h-168h and calculate the removal rate.

[0081] After biochemical treatment, the wastewater will be discharged in accordance with local wastewater discharge standards (Liaoning Province Integrated Wastewater Discharge Standard DB21 / 1627-2008).

[0082]

[0083] The obtained industrial sodium chloride is a superior grade of industrial dry salt, and the analysis was performed according to the analytical method of industrial salt GB / T5462-2015.

[0084]

[0085] Example 2

[0086] ① Take the 6-ethylthio-4-hydroxy-2-heptanone synthesis wastewater produced by the process in Example 1, adjust the pH to 12.9, distill to a kettle temperature of 105.7℃ and a column top temperature of 97.3℃, distill to remove the odorous solvent and incinerate to obtain alkaline pretreated wastewater 1, and detect the changes in COD, ammonia nitrogen and total nitrogen before and after treatment.

[0087]

[0088] ② The strongly acidic wastewater generated during the synthesis of 5-(2-(ethylthio)propyl)-3-hydroxy-2-propionyl-2-en-cyclohexanone from the process of Example 1 was distilled to a boil temperature of 104.4℃ and a top temperature of 94.7℃ to obtain neutral pretreated wastewater 2. The changes in COD, ammonia nitrogen, and total nitrogen before and after treatment were detected. The solvent was removed by distillation to obtain toluene and water. After separation, the toluene was recovered, and the aqueous phase was returned to the distillation column for re-distillation treatment.

[0089]

[0090] ③ The wastewater from the synthesis of ethyl 6-(2-(ethylthio)propyl)-2-oxo-4-(propionyloxy)cyclohex-3-en-carboxylate produced by the process in Example 1 was distilled to a boil temperature of 105.3℃ and a top temperature of 95.6℃ to obtain acidic pretreated wastewater 3. The changes in COD, ammonia nitrogen, and total nitrogen before and after treatment were detected. The solvent removed by distillation was petroleum ether and water. After separation, the petroleum ether was recovered, and the aqueous phase was returned to the distillation column for re-distillation treatment.

[0091]

[0092] ④ The pretreated wastewater 1, pretreated wastewater 2, pretreated wastewater 3 and the produced MVR desalination mother liquor are introduced into the acidification tank through a metering pump to adjust the pH to 1.1, thus obtaining acidic mixed wastewater.

[0093] ⑤ The above-mentioned acidic mixed wastewater and n-butanol are fed into a 3-stage continuous extraction separator at a mass ratio of 1:0.3 for extraction and separation. The aqueous phase enters the next stage of continuous extraction. The acidic mixed wastewater is extracted three times in a row, and the n-butanol enters the n-butanol recovery system to recover the n-butanol.

[0094] ⑥ The wastewater from the previous extraction step is fed into a continuous distillation column for light removal. The bottom temperature of the column is 105.3℃ and the top temperature is 95.6℃.

[0095] ⑦ The acidic wastewater after light removal is decolorized by a cation exchange resin (L16G) adsorption tower.

[0096] ⑧ The resin-adsorbed wastewater enters the neutralization reactor. The pH of the wastewater is adjusted to 7.4 by an online pH meter and a liquid alkali adjustment chain, resulting in neutralized wastewater.

[0097] ⑨ The neutralized wastewater is pumped into the MVR desalination equipment to obtain industrial sodium chloride. The MVR desalination mother liquor is reused in ④ acidic mixed wastewater, and the distillation fraction is low-concentration wastewater.

[0098]

[0099]

[0100] ⑩ Distilled low-concentration wastewater is discharged into a biological treatment pond for biochemical treatment.

[0101] Biochemical method: Dilute the COD of the wastewater to below 2000 mg / L, control the conductivity to below 10000 mg / L, and adjust the pH to 8.2; place the prepared water sample in a graduated cylinder, inoculate with a certain amount of aerobic sludge until the settling ratio reaches 20-30%, turn on the aeration to conduct the experiment; detect COD at 24h-168h and calculate the removal rate.

[0102] After biochemical treatment, the wastewater will be discharged in accordance with local wastewater discharge standards (Liaoning Province Integrated Wastewater Discharge Standard DB21 / 1627-2008).

[0103]

[0104] The obtained industrial sodium chloride is a superior grade of industrial dry salt, and the analysis was performed according to the analytical method of industrial salt GB / T5462-2015.

[0105]

[0106] Comparative Example 1

[0107] ① Take the 6-ethylthio-4-hydroxy-2-heptanone synthesis wastewater produced by the process in Example 1, and test the pH = 7.3. Distill it to a kettle temperature of 106.0℃ and a column top temperature of 97.5℃. Distill it to remove the odorous solvent and incinerate it to obtain pretreated wastewater 1. Test the changes in COD, ammonia nitrogen and total nitrogen before and after treatment.

[0108]

[0109] The wastewater from the synthesis of 6-ethylthio-4-hydroxy-2-heptanone underwent neutral distillation, resulting in a COD residue of 58,200 mg / L (72% removal rate) and a TN residue of 2,903 mg / L (45% removal rate). Both COD and TN levels were significantly higher than the wastewater discharge standards.

[0110] ② Take the above-mentioned pretreated wastewater 1, pretreated wastewater 2 and pretreated wastewater 3 from Example 1, and the produced MVR desalination mother liquor, and introduce them into the acidification tank through a metering pump to adjust the pH to 0.75 to obtain acidic mixed wastewater.

[0111] ③ The above-mentioned acidic mixed wastewater and chloroform are fed into a 3-stage continuous extraction separator at a mass ratio of 1:0.3 for extraction and separation. The aqueous phase enters the next stage of continuous extraction. The acidic mixed wastewater is extracted three times in a row, and the chloroform enters the chloroform recovery system to recover the chloroform.

[0112] ④ The wastewater from the previous extraction step is fed into a continuous distillation column for light removal. The bottom temperature of the column is 105.6℃ and the top temperature is 95.7℃.

[0113]

[0114] ⑤ After removing light pollutants, the acidic wastewater is treated with activated carbon adsorption for decolorization.

[0115] ⑥ The activated carbon adsorbed wastewater enters the neutralization kettle. The pH of the wastewater is adjusted to 7.2 by an online pH meter and liquid alkali adjustment chain control, thus obtaining neutralized wastewater.

[0116]

[0117] ⑦ The neutralized wastewater is pumped into the MVR desalination equipment to obtain industrial sodium chloride. The MVR desalination mother liquor is reused in the above-mentioned acidic mixed wastewater and distilled into low-concentration wastewater.

[0118]

[0119] ⑧ Dilute the distilled low-concentration wastewater with twice the amount of water before it enters the biological treatment tank for biological treatment.

[0120] ⑨ Biochemical method: Dilute the COD of the wastewater to below 2000 mg / L, control the conductivity to below 10000 mg / L, and adjust the pH to 7.8; place the prepared water sample in a graduated cylinder, inoculate with a certain amount of aerobic sludge until the settling ratio reaches 20-30%, turn on the aeration to conduct the experiment; detect COD at 24h-168h and calculate the removal rate.

[0121] The wastewater after biochemical treatment cannot meet the local wastewater discharge standards, with COD and total nitrogen exceeding the standards. It needs to be further diluted before discharge (in accordance with Liaoning Province Integrated Wastewater Discharge Standard DB21 / 1627-2008).

[0122]

[0123]

[0124] The obtained industrial sodium chloride meets the second-grade standard for industrial dry salt, but cannot meet the superior grade standard for industrial dry salt. The analysis was performed according to the analytical method of GB / T5462-2015 for industrial salt.

[0125]

[0126] As can be seen from the comparison of the examples and comparative examples, in Example 1, the 6-ethylthio-4-hydroxy-2-heptanone synthesis wastewater, controlled at pH ≥ 12, achieved a COD removal rate of 87% and a TN removal rate of 98% during distillation. In Comparative Example 1, the 6-ethylthio-4-hydroxy-2-heptanone synthesis wastewater, after neutral distillation, had a residual COD of 58200 mg / L (72% removal rate) and a residual TN of 2903 mg / L (45% removal rate), with TN levels far exceeding the wastewater discharge standards. After extraction with n-butanol, the acidic mixed wastewater showed a COD reduction to approximately 3772 mg / L (75% removal rate), and after chloroform extraction, the COD reduction to approximately 15200 mg / L, with a COD removal rate of only 36%. The n-butanol extraction C... The OD removal rate is better than that of chloroform. Furthermore, in the examples, the sodium chloride obtained after adsorption of the mixed wastewater by cation exchange resin L16G is white, while in Comparative Example 2, the sodium chloride obtained after adsorption of the mixed wastewater by activated carbon is light brown. The decolorization effect of cation exchange resin L16G is superior to that of activated carbon. Therefore, the sodium chloride content obtained in Examples 1 and 2 is greater than 99.1%, classifying it as white, high-grade industrial dry salt with a COD of less than 300 mg / L and a TN of less than 5 mg / L. The sodium chloride content obtained in Comparative Example 2 is less than 97.5%, classifying it as light brown, high-grade industrial wet salt with a COD of greater than 9000 mg / L and a TN of greater than 200 mg / L. The economic value of white, high-grade industrial dry salt and light brown, high-grade industrial wet salt differs significantly. In Examples 1 and 2, the desalination distillation wastewater meets the biochemical standards and is directly discharged into the biochemical tank. After biochemical treatment, it can meet the Liaoning Provincial Integrated Wastewater Discharge Standard DB21 / 1627-2008. In Comparative Example 1, the desalination distillation wastewater needs to be diluted with 2 times the amount of low-concentration wastewater to meet the biochemical standards of the biochemical tank for COD. After biochemical treatment, it needs to be diluted with 4 times the amount of concentrated wastewater to meet the discharge standards for TN. Therefore, Comparative Example 1 requires more water to dilute in order to meet the Liaoning Provincial Integrated Wastewater Discharge Standard DB21 / 1627-2008, resulting in a huge water consumption.

Claims

1. A method for treating wastewater generated during the industrial synthesis of clethodim, characterized in that: Wastewater generated during the synthesis of various intermediates in the industrial synthesis of clethodim was pretreated separately. The pretreated wastewater was mixed and adjusted to acidity to obtain acidic mixed wastewater. Impurities were separated by extraction under acidic conditions. The extracted wastewater was then treated to remove light pollutants. After removing light pollutants, the wastewater was decolorized. The decolorized wastewater was then adjusted to neutral and evaporated for desalination to obtain high-quality industrial sodium chloride and low-concentration wastewater that can be directly biodegraded. Wastewater pretreatment generated during intermediate synthesis is as follows: Step (1) The wastewater generated during the synthesis of intermediate 6-ethylthio-4-hydroxy-2-heptanone was adjusted to pH ≥ 12 and then subjected to continuous distillation to obtain alkaline pretreated wastewater 1; The wastewater generated during the synthesis of intermediate 6-(2-(ethylthio)propyl)-2-oxo-4-(propionyloxy)cyclohex-3-en-carboxylic acid ethyl ester in step (2) was subjected to continuous distillation to obtain neutral pretreated wastewater 2. The wastewater generated during the synthesis of intermediate 5-(2-(ethylthio)propyl)-3-hydroxy-2-propionyl-2-en-cyclohexanone in step (3) was subjected to continuous distillation to obtain acidic pretreated wastewater 3. Step (4) introduce alkaline pretreated wastewater 1, pretreated wastewater 2, pretreated wastewater 3, and MVR desalination mother liquor into an acidification tank and adjust the pH to ≤1.5 to obtain acidic mixed wastewater; Step (5) The acidic mixed wastewater and the extraction solvent are respectively fed into a continuous extraction separator for extraction and separation. The aqueous phase is fed into the next stage of continuous extraction. The acidic mixed wastewater is extracted three times in a row. The extraction solvent is fed into the solvent recovery system to recover the solvent. Step (6) The wastewater obtained in step (5) is fed into a continuous distillation column for light component removal; Step (7) The wastewater after light removal in step (6) is decolorized by a resin adsorption tower; Step (8) The decolorized wastewater enters the neutralization kettle and the pH is adjusted to neutral to obtain neutralized wastewater; In step (9), the neutralized wastewater is evaporated and desalinated to obtain industrial sodium chloride. The MVR desalination mother liquor is reused in the acidic mixed wastewater, and the distillation fraction is low-concentration wastewater. Step (10) The distilled low-concentration wastewater is diluted and then enters the biochemical tank for further treatment.

2. The method for treating wastewater generated during the industrial synthesis of clethodim according to claim 1, characterized in that: The continuous distillation process in step (1) is as follows: distillation to a kettle temperature of 105-106°C and a column top temperature of 97-98°C; The continuous distillation process in step (2) is as follows: distillation to a kettle temperature of 104-105℃ and a column top temperature of 94-95℃; The continuous distillation process in step (3) is as follows: distillation to a kettle temperature of 103-104℃ and a column top temperature of 92-94℃.

3. The method for treating wastewater generated during the industrial synthesis of clethodim according to claim 1, characterized in that: Step (5) The extraction solvent is one or more of n-butanol, pentanol, n-butyl acetate, n-butyl propionate, and methyl isobutyl ketone; the mass ratio of acidic mixed wastewater to solvent is 1:0.3 to 1:

1.

4. The method for treating wastewater generated during the industrial synthesis of clethodim according to claim 2, characterized in that: Step (6): The bottom temperature of the continuous light distillation column is 105-106℃, and the top temperature is 95-96℃.

5. The method for treating wastewater generated during the industrial synthesis of clethodim according to claim 1, characterized in that: In step (7), the adsorption resin is either cationic L16G or anionic XDA-1.

6. The method for treating wastewater generated during the industrial synthesis of clethodim according to claim 1, characterized in that: Step (8) The decolorized wastewater enters the neutralization kettle and the pH is adjusted to 6.5-7.5 to obtain neutralized wastewater.

7. The method for treating wastewater generated during the industrial synthesis of clethodim according to claim 1, characterized in that: Step (10) Dilute low-concentration wastewater to COD < 2000 mg / L; NH3-N < 30 mg / L; TN < 50 mg / L, control conductivity within 10000 mg / L, adjust pH to between 6 and 9, introduce into biological treatment tank, control the wastewater to aerobic sludge settling ratio at 20-30%, turn on aeration for biological treatment.

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