A method for treating wastewater containing carbonate and DMF

Abstract

This invention relates to the field of pesticide synthesis technology, specifically to a method for treating wastewater containing carbonates and DMF. The wastewater is acidified, and after acidification, it is extracted to separate the aqueous phase and DMF. The separated aqueous phase is neutralized with alkali, then evaporated to remove light content, concentrated, and filtered to obtain salt and mother liquor, thus achieving the treatment of wastewater containing carbonates and DMF. In this method, DMF in the wastewater is extracted using an organic solvent, followed by distillation separation and reuse in the synthesis process. The resulting DMF-containing effluent requires no further treatment and can be directly recycled for use in the post-treatment process of the next batch of synthesis, significantly reducing wastewater discharge. The mother liquor is reused in the next batch of wastewater treatment. The entire process conforms to the concept of green environmental protection and embodies economic efficiency and practicality.

Description

Technical Field

[0001] This invention relates to the field of pesticide synthesis technology, specifically to a method for treating wastewater containing carbonates and DMF. Background Technology

[0002] The carbonate / DMF reaction system is a common acid reaction system. After the reaction is completed, DMF is distilled, and extractant and water are added to separate the layers, producing wastewater containing carbonate and DMF. This wastewater is characterized by high COD, high salinity, high total nitrogen, and poor biodegradability, making it a difficult-to-treat industrial wastewater.

[0003] Existing methods for treating wastewater containing carbonates and DMF involve centrifugal extraction of industrial wastewater containing organic matter, DMF, and carbonates. The resulting raffinate is then evaporated in an evaporator to obtain condensate and mixed salts. The collected condensate undergoes biochemical degradation treatment in a biochemical degradation tank. The mixed salts are first heated at a low temperature sufficient to decompose dimethylamine hydrochloride, producing dimethylamine gas, which is then condensed and recovered. The mixed salts are then carbonized by heating at an increased temperature of 400-800°C. However, due to the low solubility of carbonates, a large amount of water needs to be added during extraction to dissolve them. Furthermore, the condensate contains DMF, which is harmful to organisms during the biochemical degradation process.

[0004] In summary, the current treatment methods for wastewater containing carbonates and DMF are still not perfect. Summary of the Invention

[0005] To address the aforementioned problems, the purpose of this invention is to propose a method for treating wastewater containing carbonates and DMF.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for treating wastewater containing carbonates and DMF involves acidifying the wastewater, extracting the acidified wastewater to separate the aqueous phase and DMF, neutralizing the separated aqueous phase with alkali, evaporating to remove light, concentrating, and filtering to obtain salt and mother liquor, thereby achieving the treatment of wastewater containing carbonates and DMF.

[0008] Specifically, the following steps are included:

[0009] (1) Acidification: Transfer the wastewater to be treated into the acidification kettle, add acidifying agent to acidify, and adjust the pH value to 3-5;

[0010] (2) Extraction: Transfer the acidified wastewater from step (1) into the extraction vessel, add extractant into the extraction vessel, set the extraction pressure and extraction temperature in the vessel, and let it stand to separate the aqueous phase and organic phase after extraction.

[0011] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel and add alkali to neutralize it;

[0012] (4) Remove light phase: Transfer the neutralized aqueous solution from step (3) into the evaporator. After setting the pressure and evaporation temperature inside the evaporator, the vapor phase below 98°C is transferred into the collection tank, while the aqueous solution remains temporarily in the evaporator.

[0013] (5) Concentration: Continue heating the aqueous solution after removing light in step (4) to evaporate it, concentrate it until the solid and liquid volumes are equal, then stop heating and collect the distilled water in a collection tank;

[0014] (6) Filtration: The concentrated aqueous solution is cooled to a specific temperature and separated by centrifugation to obtain wet salt and mother liquor. The mother liquor is reused for the next batch of wastewater treatment.

[0015] The carbonates in wastewater containing carbonates and DMF are potassium carbonate or sodium carbonate.

[0016] The acidifying agent in step (1) is hydrochloric acid, the acidification temperature is 20-40℃, and the pH value after acidification is 2-5.

[0017] The extractant in step (2) is one or more of dichloromethane, chloroform, 1,2-dichloroethane, and 1,1,2-trichloroethane, preferably chloroform, and the extraction is performed 4 to 6 times.

[0018] In step (2), the pressure inside the extraction vessel is atmospheric pressure, the temperature is 20-40℃, and the amount of extractant used each time is 15-30% of the mass of the acidified solution.

[0019] The extraction stirring time is 15-30 minutes, and the standing time for separation after extraction is 15-30 minutes.

[0020] The alkali used in step (3) is an aqueous solution of potassium hydroxide or sodium hydroxide; the pH after neutralization is 6-9.

[0021] The pressure inside the evaporator in step (4) is atmospheric pressure, and the evaporation temperature is 98-100℃.

[0022] The evaporation pressure in step (5) is from atmospheric pressure to -0.099 MPa, and the evaporation temperature is set to 100 to 130°C.

[0023] Step (6) Cool the concentrated aqueous solution from step (5) to 20-40°C.

[0024] The present invention has the following advantages:

[0025] The present invention provides a method for treating carbonate and DMF-containing wastewater. DMF in the wastewater is extracted using an organic solvent, then separated by distillation and reused in the synthesis process. The resulting DMF-containing effluent requires no further treatment and can be directly recycled for use in the post-treatment process of the next batch of synthesis, significantly reducing wastewater discharge. The mother liquor is reused in the next batch of wastewater treatment. The entire process conforms to the concept of green environmental protection and demonstrates both economic efficiency and practicality. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] (1) Acidification: 224.2g of wastewater containing potassium carbonate and DMF (DMF content 9.7%) was transferred into the acidification kettle, the temperature was set to 30℃, and 24g of 30% hydrochloric acid was added to adjust the pH to 5;

[0029] (2) Extraction: The wastewater after acidification in step (1) is transferred into the extraction vessel. The pressure in the extraction vessel is set to atmospheric pressure and the temperature is set to 30°C. It is extracted with chloroform four times, each time using 56g of chloroform. After extraction, the DMF content in the wastewater is reduced to 2.2%. After extraction, the mixture is allowed to stand and separate into layers. The stirring time after extraction is 30 minutes, and the separation time after extraction is 30 minutes. The aqueous phase and organic phase are separated.

[0030] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 1g of 48% potassium hydroxide to adjust the pH to 7;

[0031] (4) Light component removal: The aqueous solution after neutralization in step (3) is transferred into the evaporator. The pressure inside the evaporator is set to atmospheric pressure. Light component removal is carried out under atmospheric pressure until the temperature at the top of the column reaches 100°C. 15.1g of light component is collected by distillation.

[0032] (5) Concentration: Continue evaporation at normal pressure in the evaporator, set the evaporation temperature to 130℃, and distill out 162g of water. The remaining solid and liquid volumes are basically equal, and the distilled water has a remaining DMF content of 4.0%. Of this, 160g of distilled water is reused in the next batch of synthesis post-processing.

[0033] (6) Filtration: After distillation, the temperature was lowered to 30°C and separated by centrifugation to obtain 27.1g of wet potassium chloride, 21.3g of mother liquor, and DMF content of 10.2%. The mother liquor was reused for the next batch of wastewater treatment.

[0034] Example 2

[0035] (1) Acidification: 254.5g of wastewater containing potassium carbonate and DMF (DMF content 8.6%), 21.3g of the previous batch mother liquor (DMF content 10.2%), were added and transferred into the acidification kettle. The temperature was set to 25℃, and 23g of 30% hydrochloric acid was added to adjust the pH to 4.

[0036] (2) Extraction: The acidified wastewater from step (1) is transferred into the extraction vessel. The pressure inside the extraction vessel is set to atmospheric pressure and the temperature is set to 25°C. It is extracted four times with chloroform, each time using 56g of chloroform. After extraction, the DMF content in the wastewater is reduced to 3.0%. After extraction, the mixture is allowed to stand and separate into layers. The stirring time after extraction is 30 minutes, and the separation time after extraction is 30 minutes. The aqueous phase and organic phase are separated.

[0037] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 1g of 48% potassium hydroxide to adjust the pH value to 8;

[0038] (4) Light component removal: The aqueous solution after neutralization in step (3) is transferred into the evaporator. The pressure inside the evaporator is set to atmospheric pressure. Light components are removed under atmospheric pressure until the temperature at the top of the column reaches 100°C. 14.1g of light components are distilled off and collected.

[0039] (5) Concentration: Continue to evaporate under reduced pressure in the evaporator (vacuum degree -0.095MPa), set the evaporation temperature to 100℃, and distill out 208g of water. The remaining solid and liquid volumes are basically equal. The DMF content of the distilled water is 4.6%, of which 160g of distilled water is reused in the next batch of synthesis post-processing.

[0040] (6) Filtration: After distillation, the temperature was lowered to 25°C and separated by centrifugation to obtain 36.9g of wet potassium chloride, 24.7g of mother liquor, and DMF content of 9.8%. The mother liquor was reused for the next batch of wastewater treatment.

[0041] Example 3

[0042] (1) Acidification: Add 94.3 kg of wastewater containing potassium carbonate and DMF (DMF content 8.2%) to the acidification reactor, set the temperature to 20℃, and add 10.2 kg of 30% hydrochloric acid to adjust the pH to 5;

[0043] (2) Extraction: The acidified wastewater from step (1) is transferred into the extraction vessel. The pressure inside the extraction vessel is set to atmospheric pressure and the temperature is set to 20°C. It is extracted five times with chloroform, using 20 kg of chloroform each time. After extraction, the DMF content drops to 2.2%. After extraction, the mixture is allowed to stand and separate into layers. The stirring time after extraction is 30 minutes, and the separation time after extraction is 30 minutes. The aqueous phase and organic phase are separated.

[0044] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 0.6 kg of 48% potassium hydroxide to adjust the pH value to 8;

[0045] (4) Light component removal: The aqueous solution after neutralization in step (3) is transferred into the evaporator. The pressure inside the evaporator is set to atmospheric pressure. Light components are removed under atmospheric pressure until the temperature at the top of the tower reaches 100°C. 6.7 kg of light components are collected by distillation.

[0046] (5) Concentration: Continue to evaporate under reduced pressure in the evaporator (vacuum degree -0.09MPa), set the evaporation temperature to 100℃, and distill out 69.1kg of water. The remaining solid and liquid volumes are basically equal. The distilled water has a DMF content of 4.3%. The distilled water is reused in the next batch of synthesis post-processing.

[0047] (6) Filtration: After distillation, the temperature is lowered to 20°C and filtered by centrifuge to obtain 8.3 kg of wet salt and 8.7 kg of mother liquor with DMF content of 10.8%. The mother liquor is reused for the next batch of wastewater treatment.

[0048] Example 4

[0049] (1) Acidification: Add 111.7 kg of wastewater containing potassium carbonate and DMF (DMF content 9.2%) to the acidification reactor, add 8.7 kg of the previous batch of mother liquor, set the temperature to 30℃, and add 11.0 kg of 30% hydrochloric acid to adjust the pH to 3;

[0050] (2) Extraction: The acidified wastewater from step (1) is transferred into the extraction vessel. The pressure inside the extraction vessel is set to atmospheric pressure and the temperature is set to 30°C. Chloroform is used for extraction six times, with 20 kg of chloroform each time. After extraction, the DMF content drops to 1.5%. After extraction, the mixture is allowed to stand and separate into layers. The stirring time after extraction is 30 minutes, and the separation time after extraction is 30 minutes. The aqueous phase and organic phase are separated.

[0051] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 0.7 kg of 48% potassium hydroxide to adjust the pH value to 7;

[0052] (4) Light component removal: The aqueous solution after neutralization in step (3) is transferred into the evaporator. The pressure inside the evaporator is set to atmospheric pressure. Light components are removed under atmospheric pressure until the temperature at the top of the column reaches 100°C. 7.2 kg of light components are collected by distillation.

[0053] (5) Concentration: Continue to evaporate under reduced pressure in the evaporator (vacuum degree -0.095MPa), set the evaporation temperature to 100℃, and distill out 87.1Kg of water. The remaining solid and liquid volumes are basically equal. The DMF content of the distilled water is 6.1%. Among them, 65Kg of distilled water is reused in the next batch of synthesis post-processing.

[0054] (6) Filtration: After distillation, the temperature is reduced to 30°C and filtered by centrifuge to obtain 14.7 kg of wet salt and 9.7 kg of mother liquor with DMF content of 9.3%. The mother liquor is reused for the next batch of wastewater treatment.

[0055] Example 5

[0056] (1) Acidification: 204.3g of wastewater containing sodium carbonate and DMF (DMF content 8.7%) was transferred into the acidification reactor, the temperature was set to 35℃, and 23.7g of 30% hydrochloric acid was added to adjust the pH to 5;

[0057] (2) Extraction: The acidified wastewater from step (1) is transferred into the extraction vessel. The pressure inside the extraction vessel is set to atmospheric pressure and the temperature is set to 35°C. It is extracted four times with chloroform, each time using 51g of chloroform. After extraction, the DMF content in the wastewater is reduced to 1.9%. After extraction, the mixture is allowed to stand and separate into layers. The stirring time after extraction is 30 minutes, and the separation time after extraction is 30 minutes. The aqueous phase and organic phase are separated.

[0058] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 1g of 30% sodium hydroxide to adjust the pH value to 7;

[0059] (4) Light component removal: The aqueous solution after neutralization in step (3) is transferred into the evaporator. The pressure inside the evaporator is set to atmospheric pressure. Light component removal is carried out under atmospheric pressure until the temperature at the top of the column reaches 100°C. 13.1g of light component is collected by distillation.

[0060] (5) Concentration: Continue evaporation at atmospheric pressure in the evaporator, set the evaporation temperature to 130℃, and distill out 158.2g of water. The remaining solid and liquid volumes are basically equal, and the distilled water has a DMF content of 3.8%. Of this, 144g of distilled water is reused in the next batch of synthesis post-processing.

[0061] (6) Filtration: After distillation, the temperature was lowered to 25°C and separated by centrifugation to obtain 23.1g of wet sodium chloride, 19.3g of mother liquor, and DMF content of 9.9%. The mother liquor was reused for the next batch of wastewater treatment.

[0062] Example 6

[0063] (1) Acidification: 244.9g of wastewater containing sodium carbonate and DMF (DMF content 8.4%), along with 19.3g of the previous batch mother liquor (DMF content 9.9%), were transferred into the acidification reactor. The temperature was set to 30℃, and 23g of 30% hydrochloric acid was added to adjust the pH to 4.

[0064] (2) Extraction: The wastewater after acidification in step (1) is transferred into the extraction vessel. The pressure in the extraction vessel is set to atmospheric pressure and the temperature is set to 30°C. It is extracted with chloroform four times, each time using 56g of chloroform. After extraction, the DMF content in the wastewater is reduced to 2.9%. After extraction, the mixture is allowed to stand and separate into layers. The stirring time after extraction is 30 minutes, and the separation time after extraction is 30 minutes. The aqueous phase and organic phase are separated.

[0065] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 1g of 30% sodium hydroxide to adjust the pH value to 8;

[0066] (4) Light component removal: The aqueous solution after neutralization in step (3) is transferred into the evaporator. The pressure inside the evaporator is set to atmospheric pressure. Light components are removed under atmospheric pressure until the temperature at the top of the column reaches 100°C. 14.9g of light components are collected by distillation.

[0067] (5) Concentration: Continue to evaporate under reduced pressure in the evaporator (vacuum degree -0.095MPa), set the evaporation temperature to 100℃, and 196g of water is distilled out. The remaining solid and liquid volumes are basically equal. The DMF content of the distilled water is 4.6%, of which 144g of distilled water is reused in the next batch of synthesis post-processing.

[0068] (6) Filtration: After distillation, the temperature was lowered to 20°C and separated by centrifugation to obtain 34.9g of wet sodium chloride, 26.7g of mother liquor, and DMF content of 9.28%. The mother liquor was reused for the next batch of wastewater treatment.

[0069] Comparative Example 1

[0070] (1) Acidification: 224.2g of wastewater containing potassium carbonate and DMF (DMF content 9.7%) was transferred into the acidification reactor, the temperature was set to 30℃, and 28g of 30% hydrochloric acid was added to adjust the pH to 1;

[0071] (2) Extraction: The wastewater after acidification in step (1) is transferred into the extraction vessel. The pressure in the extraction vessel is set to atmospheric pressure and the temperature is set to 30°C. It is extracted four times with chloroform, each time using 56g of chloroform. After extraction, the DMF content in the wastewater is reduced to 2.2%. After extraction, the mixture is allowed to stand and separate into aqueous and organic phases.

[0072] (3) Neutralization: Transfer the aqueous phase extracted from the extraction vessel in step (2) into the neutralization vessel, and add 7.8g of 48% potassium hydroxide to adjust the pH to 7;

[0073] (4) Light component removal: Transfer the neutralized aqueous solution from step (3) into the evaporator, set the pressure inside the evaporator to atmospheric pressure, remove light components under atmospheric pressure until the temperature at the top of the tower reaches 100°C, and distill off and collect 15g of light components.

[0074] (5) Concentration: Continue evaporation at normal pressure in the evaporator, set the evaporation temperature to 130℃, and distill out 171g of water. The remaining solid and liquid volumes are basically equal, and the distilled water has a remaining DMF content of 4.0%. Of this, 160g of distilled water is reused in the next batch of synthesis post-processing.

[0075] (6) Filtration: After distillation, the temperature was lowered to 30°C and separated by centrifugation to obtain 29.1g of wet potassium chloride, 21.3g of mother liquor, and DMF content of 10.2%. The mother liquor was reused for the next batch of wastewater treatment.

[0076] Comparative Example 2

[0077] (1) Centrifugal extraction: 1 kg of industrial wastewater containing 250 g / L organic matter, 180 g / L DMF and 280 g / L salts is added to a centrifugal extractor with a rotating drum. 250 g chloroform is used as the extractant for centrifugal extraction to obtain the extract phase as the organic phase and the raffinate phase as the aqueous phase.

[0078] (2) Aqueous phase evaporation: The obtained raffinate phase is evaporated in an evaporator to obtain evaporation condensate as cooling water and evaporation concentrate at the bottom of the evaporator. The evaporation concentrate is filtered to obtain mixed salts and concentrate.

[0079] (3) Biochemical treatment of condensate: The collected condensate is subjected to biochemical degradation treatment in a biochemical degradation treatment tank;

[0080] (4) Harmless treatment of mixed salts: The mixed salts are first heated at a low temperature sufficient to cause the decomposition of dimethylamine hydrochloride. The dimethylamine hydrochloride decomposes to produce dimethylamine gas, which is condensed and recovered. Then the mixed salts are heated at an increased temperature of 400-800℃ for carbonization.

[0081] As can be seen from the above examples and comparative examples, Comparative Example 1, due to changes in acidification conditions and the addition of excessive hydrochloric acid to adjust the pH to 1, resulted in a significant increase in the amount of alkali required for subsequent neutralization, thus increasing wastewater treatment costs. Comparative Example 2 omitted the acidification and neutralization processes; due to the low solubility of carbonates, a large amount of water needed to dissolve them during extraction, and the condensate contained DMF, which is harmful to organisms during biochemical degradation. Therefore, the specific reaction conditions of this invention ensure that the distillate can be used for the next batch of post-synthesis treatment, and the mother liquor can be used for the next batch of wastewater treatment, reducing wastewater discharge, improving economic efficiency, and meeting process design requirements.

Claims

1. A method for treating wastewater containing carbonates and DMF, characterized in that: The wastewater to be treated is acidified, and after acidification, the wastewater is extracted to separate the aqueous phase and DMF. The separated aqueous phase is neutralized with alkali and then evaporated to remove light, concentrated and filtered to obtain salt and mother liquor, thus realizing the treatment of wastewater containing carbonate and DMF.

2. The method for treating wastewater containing carbonates and DMF according to claim 1, characterized in that: Includes the following steps: (1) Acidification: Add an acidifying agent to the wastewater to be treated for acidification; (2) Extraction: Add the extractant to the acidified solution in step (1) and extract. After extraction, let it stand to separate the aqueous phase and the organic phase. (3) Neutralization: Add the aqueous phase from step (2) to the alkali for neutralization; (4) Remove light phase: Heat the aqueous solution after neutralization in step (3) to evaporate. The vapor phase below 98°C is transferred into the collection tank, while the aqueous solution remains in the evaporation vessel. (5) Concentration: Continue to heat and evaporate the aqueous solution after removing light in step (4) until the solid and liquid volumes are equal, then stop heating and collect the distilled water; (6) Filtration: Cool the concentrated aqueous solution from step (5) and filter it to obtain wet salt and mother liquor. The mother liquor is reused for the next batch of wastewater treatment.

3. The method for treating wastewater containing carbonates and DMF according to claim 2, characterized in that: The acidifying agent in step (1) is hydrochloric acid, the acidification temperature is 20-40℃, and the pH value after acidification is 2-5.

4. The method for treating wastewater containing carbonates and DMF according to claim 2, characterized in that: The extractant in step (2) is one or more of dichloromethane, chloroform, 1,2-dichloroethane, and 1,1,2-trichloroethane; the number of extractions is 4 to 6, and the amount of extractant used each time is 15 to 30% of the mass of the acidified solution. The extraction stirring time is 15-30 minutes, and the standing time for separation after extraction is 15-30 minutes.

5. The method for treating wastewater containing carbonates and DMF according to claim 2, characterized in that: The extraction pressure in step (2) is atmospheric pressure, and the temperature is 20-40℃.

6. The method for treating post-production wastewater containing carbonates and DMF according to claim 2, characterized in that: The alkali used in step (3) is an aqueous solution of potassium hydroxide or sodium hydroxide; the pH after neutralization is 6-9.

7. The method for treating wastewater containing carbonates and DMF according to claim 2, characterized in that: Step (4) The heating and evaporation pressure is atmospheric pressure, and the evaporation temperature is 98-100℃.

8. The method for treating wastewater containing carbonates and DMF according to claim 2, characterized in that: Step (5) The heating and evaporation pressure is from atmospheric pressure to -0.099 MPa, and the evaporation temperature is 100 to 130°C.

9. The method for treating wastewater containing carbonates and DMF according to claim 2, characterized in that: In step (6), the concentrated aqueous solution from step (5) is cooled to 20–40°C.