Method for treating wastewater concentrate mother liquor

Abstract

This invention provides a method for treating concentrated wastewater mother liquor, comprising the following steps: mixing the concentrated wastewater mother liquor with an organic solvent and then performing solid-liquid separation to obtain a first solid product and a first liquid product; subjecting the first liquid product to distillation or rectification to obtain a treated product; subjecting the treated product to solid-liquid separation to obtain a second solid product and a second liquid product; and subjecting the second liquid product to rectification to recover the organic solvent, obtaining an organic solvent recovery product. This invention significantly reduces the difficulty of treating concentrated wastewater mother liquor. The equipment required for this method is simple, consisting only of a reaction vessel, a distillation column, and solid-liquid separation equipment; the equipment material requirements are low, and the equipment investment is small. The operating conditions of this method are mild, and the safety is good. This method simply completes the final disposal through biochemical treatment, resource utilization, and incineration, without generating other "three wastes" problems.

Description

Technical Field

[0001] This invention relates to a method for treating concentrated wastewater mother liquor, belonging to the field of water pollution control and wastewater treatment. Background Technology

[0002] The chemical industry (especially the fine chemical industry) generates a significant amount of wastewater with high salt and organic matter concentrations. A common treatment method for this type of wastewater is pretreatment to remove most of the organic matter, followed by evaporation and crystallization using mechanical vapor recompression (MVR) evaporators or multi-effect thickeners to produce salt, which is then either recycled or landfilled. However, if the wastewater contains high-boiling-point, highly water-soluble organic matter, this portion often cannot be removed due to limitations in pretreatment costs and effectiveness, and instead accumulates in the concentrated mother liquor during evaporation and crystallization. The higher the concentration of such organic matter in the concentrated mother liquor, the greater the impact on the evaporation capacity of the evaporation system and the quality of the produced salt. Ultimately, this concentrated mother liquor is discharged for further treatment.

[0003] Currently, there are three main methods for treating concentrated mother liquor discharged externally. (1) Concentration + rake drying: Concentration is further achieved using a concentration device (such as a reactor), followed by drying in a rake dryer to evaporate all the liquid and bag the remaining solids. The advantages are simple process and cheap equipment, but the disadvantages are also obvious – high steam consumption and severe scaling of the equipment. (2) Incineration: Concentrated mother liquor is directly sent to a waste liquid incinerator after discharge to burn off the organic matter. The advantages are good salt output, but the disadvantages are high equipment investment, immature technology, and high fuel consumption. (3) Wet oxidation: Under high temperature and pressure, the organic matter in the concentrated mother liquor is degraded into small molecule low-boiling-point organic matter and even mineralized into carbon dioxide and water by oxygen, and then returned to the concentration device. The advantages are simple process flow and low energy consumption, but the disadvantage is that the equipment investment is too large.

[0004] Therefore, researching a treatment method for concentrated wastewater mother liquor can reduce the difficulty of treating concentrated wastewater mother liquor containing high boiling point and high water-soluble organic matter, and has become an urgent technical problem to be solved. Summary of the Invention

[0005] The problem the invention aims to solve

[0006] In view of the technical problems existing in the prior art, such as the difficulty in removing high-boiling-point and highly water-soluble organic matter from wastewater, the present invention first provides a method for treating concentrated wastewater mother liquor. The method for treating concentrated wastewater mother liquor of the present invention reduces the difficulty of treating concentrated wastewater mother liquor containing high-boiling-point and highly water-soluble organic matter.

[0007] Solution for solving the problem

[0008] This invention provides a method for treating concentrated wastewater mother liquor, comprising the following steps:

[0009] After mixing the concentrated mother liquor of wastewater with an organic solvent, solid-liquid separation is performed to obtain a first solid product and a first liquid product.

[0010] The first liquid product is subjected to distillation or rectification to obtain a processed product.

[0011] The processed product is subjected to solid-liquid separation to obtain a second solid product and a second liquid product.

[0012] The second liquid product is subjected to distillation to recover the organic solvent, resulting in an organic solvent recovery product.

[0013] According to the treatment method of the present invention, the wastewater concentrate mother liquor includes saline concentrate wastewater; preferably, the salt content in the saline concentrate wastewater is 20% or more.

[0014] According to the processing method of the present invention, the salt component is insoluble in the organic solvent; preferably, the salt component includes one or more of sodium sulfate, sodium chloride, ammonium sulfate, ammonium chloride, potassium sulfate, and potassium chloride.

[0015] According to the treatment method of the present invention, the concentrated saline wastewater contains organic matter; preferably, the total organic carbon in the concentrated saline wastewater is 10,000 mg / L or more; more preferably, the boiling point of the concentrated saline wastewater is 110-130°C; and even more preferably, the boiling point of the organic matter is greater than 130°C.

[0016] According to the processing method of the present invention, the boiling point of the organic solvent is higher than that of water, preferably, the boiling point of the organic solvent is 120-210°C.

[0017] Preferably, the boiling point of the organic solvent is lower than the boiling point of the organic compound;

[0018] Preferably, the organic solvent includes one or a combination of two or more of ethylene glycol monomethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0019] According to the treatment method of the present invention, the amount of organic solvent used is 20% to 200% of the volume of the concentrated wastewater mother liquor.

[0020] According to the processing method of the present invention, a dehydrating agent is also added during the distillation process;

[0021] Preferably, the dehydrating agent is insoluble in water, and the boiling point of the dehydrating agent is lower than that of the organic solvent; more preferably, the boiling point of the dehydrating agent is 70-145°C.

[0022] According to the processing method of the present invention, the dehydrating agent includes one or a combination of two or more of toluene, dichloroethane, ethyl acetate, and xylene.

[0023] According to the treatment method of the present invention, the amount of the dehydrating agent is 5%-50% of the volume of the concentrated wastewater mother liquor.

[0024] According to the processing method of the present invention, the processing method further includes the step of washing the first solid product and / or the second solid product with an inorganic solvent.

[0025] The effects of the invention

[0026] The wastewater concentrate mother liquor treatment method of the present invention significantly reduces the difficulty of treating wastewater concentrate mother liquor, and its beneficial effects can be reflected in the following aspects:

[0027] 1) The processing method of the present invention requires simple equipment, including only a reaction vessel, a distillation column, and a solid-liquid separation device, with low requirements for equipment materials and low equipment investment;

[0028] 2) The processing method of the present invention operates under mild conditions and has good safety;

[0029] 3) The treatment method of the present invention can separate the concentrated mother liquor of wastewater into three parts: water, salt and distillation residue. The final disposal can be completed simply through biochemical treatment, resource utilization and incineration without generating other "three wastes" problems. Attached Figure Description

[0030] Figure 1 A schematic diagram of the wastewater concentrate mother liquor treatment process according to one embodiment of the present invention is shown. Detailed Implementation

[0031] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0032] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0033] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0034] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0035] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0036] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0037] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 15-25℃.

[0038] This invention provides a method for treating concentrated wastewater mother liquor, comprising the following steps:

[0039] After mixing the concentrated mother liquor of wastewater with an organic solvent, solid-liquid separation is performed to obtain a first solid product and a first liquid product.

[0040] The first liquid product is subjected to distillation or rectification to obtain a processed product.

[0041] The processed product is subjected to solid-liquid separation to obtain a second solid product and a second liquid product.

[0042] The second liquid product is subjected to distillation to recover the organic solvent, resulting in an organic solvent recovery product.

[0043] The treatment method of the present invention requires simple equipment, including only a reaction vessel, a distillation column, and a solid-liquid separation device. The equipment has low material requirements and low investment. The treatment method of the present invention operates under mild conditions and has good safety. The treatment method of the present invention can separate the concentrated mother liquor of wastewater into three parts: water, salt, and distillation residue. The final disposal can be easily completed through biochemical treatment, resource utilization, and incineration without generating other "three wastes" problems.

[0044] In this invention, the concentrated wastewater mother liquor refers to the discharged mother liquor wastewater after evaporation, crystallization, and desalination using mechanical vapor recompression (MVR) evaporators, multi-effect concentrators, or similar devices. Specifically, in this invention, the concentrated wastewater mother liquor includes saline concentrated wastewater; preferably, the salt content in the saline concentrated wastewater is 20% or more, for example, 20-50%. Generally, the salt content in the concentrated wastewater mother liquor is saturated.

[0045] Specifically, the salt component is insoluble in the organic solvent; separation of the salt component is only possible when the salt component is insoluble in the organic solvent. Preferably, the salt component includes one or more of sodium sulfate, sodium chloride, ammonium sulfate, ammonium chloride, potassium sulfate, and potassium chloride. More preferably, the content of the salt soluble in the organic solvent in the salt component is less than 1 wt%, such as ammonium nitrate.

[0046] Furthermore, the concentrated saline wastewater of the present invention contains organic matter; preferably, the total organic carbon in the concentrated saline wastewater is 10,000 mg / L or more, for example, 10,000-100,000 mg / L; more preferably, the boiling point of the concentrated saline wastewater is 110-130°C, for example, 112°C, 115°C, 118°C, 120°C, 122°C, 125°C, 128°C, etc.

[0047] This invention involves mixing concentrated wastewater mother liquor with an organic solvent and then separating the solid and liquid components to obtain a first solid product and a first liquid product. The organic solvent used in this invention is an aprotic polar solvent. Since the molecules of an aprotic polar solvent are polar, they will affect the solute molecules and produce a solvation effect.

[0048] In some specific embodiments, the boiling point of the organic solvent is higher than that of water. This invention involves adding an organic solvent with a boiling point higher than water to the concentrated wastewater mother liquor, removing water through distillation or rectification, and then separating the solid product from the organic solvent. The resulting solid product has a very high salt content and can be recycled after washing. The organic solvent used can be recovered through rectification, and the rectification residue can be disposed of by incineration. Preferably, the boiling point of the organic solvent is lower than that of the organic compound; by making the boiling point of the organic solvent lower than that of the organic compound, it is beneficial to recover the organic solvent.

[0049] In this invention, the boiling point of the organic solvent is 120-210℃, for example: 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, etc. The boiling point of the organic compound is generally above 130℃, for example: 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, etc.

[0050] Specifically, in this invention, the organic solvent includes one or more of ethylene glycol monomethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0051] Furthermore, in order to maximize the effectiveness of the organic solvent, the amount of the organic solvent used is 20% to 200% of the volume of the concentrated wastewater mother liquor, for example: 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, etc.

[0052] When mixing concentrated wastewater mother liquor with organic solvents, stirring or ultrasonic methods can be used to assist in mixing in order to make the mixture more uniform.

[0053] Furthermore, the first liquid product is subjected to distillation or rectification to obtain a treated product. Distillation or rectification can remove most or even all the water from the concentrated wastewater mother liquor.

[0054] Specifically, when using distillation, the water can be directly removed because the boiling point of the organic solvent is higher than that of water. Furthermore, in this invention, the boiling point of the dehydrating agent is 70-145℃, for example: 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, etc.

[0055] When using distillation, if water cannot be removed directly, a dehydrating agent can be used to assist in water removal. Specifically, a dehydrating agent can be added to the first liquid product during distillation. Preferably, the dehydrating agent is insoluble in water, and its boiling point is lower than that of the organic solvent. By using a dehydrating agent with a boiling point lower than that of the organic solvent, water can be distilled off during distillation, with minimal distillation of the organic solvent. During distillation, the dehydrating agent distills off with water in the form of an azeotrope. After condensation and separation, the dehydrating agent is returned to the distillation apparatus to continue dehydration until the dehydration is complete.

[0056] Preferably, the dehydrating agent is poorly soluble in water. Specifically, the dehydrating agent includes one or more of toluene, dichloroethane, ethyl acetate, and xylene.

[0057] In some specific implementations, the amount of the dehydrating agent is 5%-50% of the volume of the concentrated wastewater mother liquor, for example: 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc. When the amount of the dehydrating agent is 5%-50% of the volume of the concentrated wastewater mother liquor, its effect can be effectively exerted.

[0058] The water separated by the present invention through distillation or fractional distillation contains virtually no salt and has a low organic content, and can be reused after further biochemical treatment.

[0059] The product obtained after separating water through distillation or fractional distillation is essentially a solid-liquid mixture, a state in which solid and liquid coexist. Due to the presence of organic solvents, the organic matter in the concentrated wastewater mother liquor dissolves in the organic solvent, and the salt components in the concentrated wastewater mother liquor are uniformly dispersed in the organic solvent in the form of crystalline particles, avoiding the caking of organic matter and salt components on the equipment surface during the dehydration process of distillation or fractional distillation.

[0060] The present invention does not impose any particular limitation on the method of rectification or distillation, and rectification or distillation can be carried out under atmospheric pressure or reduced pressure. When using reduced pressure, the vacuum degree of reduced pressure distillation or rectification can be below 0.5 MPa, for example 0.001-0.2 MPa.

[0061] The processed product is then subjected to solid-liquid separation to obtain a second solid product and a second liquid product. Further, the processing method includes a step of washing the first solid product and / or the second solid product with an inorganic solvent. Specifically, both the first and second solid products can be washed to obtain wash water and wash product. The wash product can be utilized for resource recovery. If the wash product is a single salt, it can be combined with the salt obtained from previous evaporation and crystallization; if the wash product is a mixed salt, it can be separated according to the properties of the salts and then utilized for resource recovery. Additionally, the wash water can be combined with the concentrated mother liquor of the next batch of wastewater for further treatment.

[0062] The present invention does not impose any particular limitation on inorganic solvents; generally, any feasible solvent such as water can be used.

[0063] The present invention does not specifically limit the method of solid-liquid separation, but commonly used separation methods in the art, such as centrifugation, filtration (pressure filtration, vacuum filtration), etc.

[0064] Furthermore, the second liquid product is subjected to distillation to recover the organic solvent, yielding an organic solvent recovery product. The recovered organic solvent recovery rate is over 95%. Specifically, the organic solvent can be recovered using atmospheric distillation or vacuum distillation. When vacuum distillation is used, the vacuum level can be below 0.5 MPa, for example, 0.001-0.2 MPa. Additionally, when a dehydrating agent is used, the distillation of the second liquid product recovers a mixture of the organic solvent and the dehydrating agent. Both the recovered organic solvent and / or the dehydrating agent can be reused.

[0065] Finally, after recovering the organic solvent, a distillation residue remains. Compared with the concentrated wastewater mother liquor, the mass of the distillation residue is greatly reduced, and the salt and moisture content is extremely low, making it suitable for incineration in common incinerator types. Furthermore, it has a high calorific value, which can significantly reduce fuel consumption.

[0066] The wastewater concentrate mother liquor treatment method of the present invention avoids the problems of large equipment investment, difficult equipment operation and high energy consumption of existing treatment methods, and has strong practical value.

[0067] Example

[0068] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0069] The sample used in this example was a concentrated mother liquor of dye wastewater from a company in Zhejiang Province, obtained through evaporation and crystallization to recover ammonium chloride. The organic matter in the wastewater mainly consisted of organic amine compounds. The concentrated mother liquor was brownish-black, with a TOC (total organic carbon) of 6.2 × 10⁻⁶. 4 The concentration of the wastewater concentrate is mg / L, and the total salt content is 33.6%, of which ammonium chloride accounts for 65% of the total salt mass. Under normal pressure, the boiling point of the concentrated wastewater mother liquor is 112℃, and the boiling point of the organic matter in the concentrated wastewater mother liquor is greater than 175℃.

[0070] Example 1

[0071] Take 1000 mL of the concentrated wastewater mother liquor, add 500 mL of N,N-dimethylacetamide (DMAc), stir, and filter to obtain a first solid product and a first filtrate. Place the first filtrate in the reboiler of a distillation column, stir, and heat to separate most of the water through distillation. The separated water mass is approximately 97% of the water mass in the concentrated wastewater mother liquor, yielding a distillation product. Cool the distillation product and filter to obtain a second solid product and a second filtrate. Wash the first and second solid products with 100 mL of water and dry to obtain a solidified product containing salt and wash water. The obtained solidified product is white, and the salt content accounts for 84.3% of the total salt mass in the wastewater. Recover N,N-dimethylacetamide by vacuum distillation of the second filtrate at a vacuum degree of 0.08 MPa, obtaining an N,N-dimethylacetamide recovery product and distillation residue. The obtained N,N-dimethylacetamide recovery product is approximately 97.2% of the N,N-dimethylacetamide dosage. The obtained distillation residue has good fluidity at 80℃, accounts for 11.5% of the concentrated wastewater mother liquor by mass, and has a calorific value of 6200 kcal / kg.

[0072] Take another 1000 mL of the concentrated wastewater mother liquor, add the washing water and N,N-dimethylacetamide recovery product sequentially, and then add fresh N,N-dimethylacetamide to make up to 500 mL. After stirring, filter to obtain the third solid product and the third filtrate. Place the third filtrate in the bottom of a distillation column, stir and heat, and separate most of the water by distillation. The mass of the separated water is approximately 98% of the water mass in the concentrated wastewater mother liquor, with the remaining distillation product. Cool the distillation product and filter to obtain the fourth solid product and the fourth filtrate. Wash the third and fourth solid products with 100 mL of water and dry to obtain a solid product containing salt and washing water. The obtained solid product is white, and the salt content accounts for 98.8% of the total salt mass in the wastewater. Recover N,N-dimethylacetamide by vacuum distillation of the fourth filtrate at a vacuum degree of 0.08 MPa to obtain the N,N-dimethylacetamide recovery product and the distillation residue.

[0073] Example 2

[0074] Take 1000 mL of the concentrated wastewater mother liquor, add 500 mL of N,N-dimethylacetamide (DMAc), stir, and filter to obtain a first solid product and a first filtrate. Place the first filtrate in a glass reactor for distillation. Add 150 mL of xylene, stir, and heat. Separate most of the water using a water separator. The separated water accounts for approximately 97% of the water mass in the concentrated wastewater mother liquor, yielding a distillation product. Filter the distillation product to obtain a second solid product and a second filtrate. Wash the first and second solid products with 100 mL of water and dry to obtain a solidified product containing salt and wash water. The obtained solidified product is white, and the salt content accounts for 82.0% of the total salt mass in the wastewater. Recover xylene and N,N-dimethylacetamide by vacuum distillation of the second filtrate. The vacuum distillation vacuum degree is 0.08 MPa, yielding a mixed recovery of xylene and N,N-dimethylacetamide and distillation residue. The total amount of the recovered xylene and N,N-dimethylacetamide mixture was approximately 96.6% of the total mass of xylene and N,N-dimethylacetamide added. The obtained distillation residue had good fluidity at 80°C, accounted for 12.8% of the concentrated wastewater mother liquor by mass, and had a calorific value of 6350 kcal / kg.

[0075] Take another 1000 mL of the concentrated wastewater mother liquor, add the washing water and the mixed recovery product of N,N-dimethylacetamide and xylene sequentially, and make up to 650 mL with fresh N,N-dimethylacetamide. After stirring, filter to obtain the third solid product and the third filtrate. Place the third filtrate in a glass reactor, stir and heat, and separate most of the water through a water separator. The separated water mass is about 98% of the water mass in the concentrated wastewater mother liquor, with the remainder being distillation product. Filter the distillation product to obtain the fourth solid product and the fourth filtrate. Wash the third and fourth solid products with 100 mL of water and dry to obtain a solidified product containing salt and washing water. The obtained solid product is white, and the salt content is about 96.5% of the total salt mass in the wastewater. Recover xylene and N,N-dimethylacetamide by vacuum distillation of the fourth filtrate. The vacuum distillation vacuum degree is 0.08 MPa to obtain the N,N-dimethylacetamide recovery product and the distillation residue.

[0076] Comparative Example 1

[0077] 1000 mL of the concentrated wastewater mother liquor was placed in a glass reactor and stirred. Using thermally conductive silicone oil as a heat source, the water was evaporated, and the mother liquor was concentrated to 780 mL to obtain a concentrated product. The concentrated product was released while hot and placed in an oven at 120°C for drying. A small amount of ammonium chloride decomposed during the drying process. After drying to constant weight, the remaining solids were obtained. The remaining solids were semi-solid, viscous, and difficult to process further. The remaining solids accounted for 51.2% of the total concentrated wastewater mother liquor mass.

[0078] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0079] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for treating concentrated wastewater mother liquor, characterized in that, Includes the following steps: The concentrated wastewater mother liquor is mixed with an organic solvent and then subjected to solid-liquid separation to obtain a first solid product and a first liquid product. The concentrated wastewater mother liquor includes saline concentrated wastewater containing organic matter. The organic solvent is an aprotic polar solvent. The boiling point of the organic solvent is 145-210℃, and the boiling point of the organic matter is above 150℃. The boiling point of the organic solvent is higher than that of water, and lower than that of the organic matter. The salt components in the saline concentrated wastewater are insoluble in the organic solvent. The first liquid product is subjected to distillation or rectification to obtain a processed product. The processed product is subjected to solid-liquid separation to obtain a second solid product and a second liquid product. The second liquid product is subjected to distillation to recover the organic solvent, resulting in an organic solvent recovery product.

2. The processing method according to claim 1, characterized in that, The salt content in the concentrated saline wastewater is above 20%.

3. The processing method according to claim 2, characterized in that... The salt composition includes one or more of sodium sulfate, sodium chloride, ammonium sulfate, ammonium chloride, potassium sulfate, and potassium chloride.

4. The processing method according to any one of claims 1-3, characterized in that, The total organic carbon in the concentrated saline wastewater is above 10,000 mg / L.

5. The processing method according to claim 4, characterized in that, The boiling point of the concentrated saline wastewater is 110-130℃.

6. The processing method according to any one of claims 1-3, characterized in that, The organic solvent includes one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

7. The processing method according to any one of claims 1-3, characterized in that, The amount of organic solvent used is 20% to 200% of the volume of the concentrated wastewater mother liquor.

8. The processing method according to any one of claims 1-3, characterized in that, A dehydrating agent is also added during the distillation process.

9. The processing method according to claim 8, characterized in that, The dehydrating agent is insoluble in water, and the boiling point of the dehydrating agent is lower than that of the organic solvent.

10. The processing method according to claim 9, characterized in that, The boiling point of the water-removing agent is 70-145℃.

11. The processing method according to claim 9 or 10, characterized in that, The water-removing agent includes one or more of toluene, dichloroethane, ethyl acetate, and xylene.

12. The processing method according to claim 11, characterized in that, The amount of the water-removing agent used is 5%-50% of the volume of the concentrated wastewater mother liquor.

13. The processing method according to any one of claims 1-3, characterized in that, The processing method further includes the step of washing the first solid product and / or the second solid product with an inorganic solvent.

Images