A ternary wastewater recycling treatment method

Abstract

The application provides a ternary wastewater recycling treatment method. A polyether sulfone separation membrane is selected, modified treatment is performed on the polyether sulfone separation membrane, permeability and selective separation of the polyether sulfone separation membrane are improved, the anti-pollution property of the membrane is improved, the service life of the membrane is prolonged, and therefore the recycling efficiency of ternary wastewater is increased.

Description

Technical Field

[0001] This invention belongs to the technical field of ternary wastewater treatment, specifically relating to a method for recycling and treating ternary wastewater. Background Technology

[0002] The ternary wastewater mainly consists of mother liquor from centrifugal filtration. This mother liquor is alkaline and contains heavy metals, salts, and ammonia nitrogen. Ammonia nitrogen is primarily in the form of ammonium ions, which can be recovered using a distillation column. The resulting ammonia water is stored in an ammonia storage tank and pumped to the workshop for reuse. The wastewater after ammonia recovery is treated by membrane concentration. The pure water produced by membrane concentration is reused in the product washing section, while the concentrated water is treated by an MVR evaporator. MVR concentration and crystallization has high thermal efficiency, saves energy, and has low operating costs. A portion of the relatively pure sodium sulfate byproduct can be reused in production, while the remainder can be sold. Theoretically, this technology is feasible, and the overall operating cost is low.

[0003] Membrane separation technology has seen rapid development due to its advantages over traditional separation technologies, including low energy consumption, low cost, high separation efficiency, superior effluent quality, and ease of operation. High molecular weight polymers are currently the most researched membrane materials due to their abundant resources and ease of processing. Among polymeric membrane materials, polyethersulfone (PES) shows promising prospects in water treatment due to its excellent chemical and thermal resistance and low cost. Despite its significant advantages in membrane separation technology, PES still faces challenging issues in practical applications, such as filtration process optimization, membrane lifespan, and membrane cleaning and replacement, which urgently need to be addressed.

[0004] Among polymeric membrane-forming materials, polyethersulfone (PES) shows promising potential in water treatment due to its excellent chemical and thermal resistance and low cost. Despite its significant advantages in membrane separation technology, PES still faces challenging issues in practical applications, such as optimizing filtration processes, membrane lifespan, and membrane cleaning and replacement, which require further solutions.

[0005] Another major limitation of PES membrane applications is surface fouling, including inorganic scaling / deposition, colloidal fouling, organic fouling, and biofouling. Irreversible decreases in permeability caused by membrane fouling significantly reduce water treatment efficiency and material lifespan. Therefore, modifying PES membranes to achieve antifouling properties is crucial for improving their permeability, hydrophilicity, and antifouling capabilities.

[0006] Metal-organic frameworks (MOFs) are coordination polymers with three-dimensional porous structures. Due to their advantages such as high porosity, low density, and large specific surface area, they have been widely used in membrane separation. This invention uses PES as the membrane matrix material and prepares water-soluble MOF nanoparticles as functionalizing additives to improve the permeability and selective separation properties of PES membranes. Summary of the Invention

[0007] This invention discloses a ternary wastewater recycling treatment method to solve any of the above-mentioned or potential problems in the prior art. To solve the above-mentioned technical problems, the treatment method of this invention is as follows:

[0008] First, 10% sulfuric acid is added to the ternary wastewater to remove heavy metals, and then the mixture is filtered. 20% liquid alkali is added to the filtrate to adjust the pH to above 11.5. The temperature is then raised to 90°C and the solution enters the distillation tower deammoniation system. The resulting ammonia water is recycled. The bottom liquid is treated by a security filter and membrane to obtain pure water, which is then recycled. The concentrate is treated by MVR evaporation and crystallization to obtain sodium sulfate crystals and condensate, which are then recycled separately.

[0009] The membrane treatment uses a polyethersulfone porous membrane;

[0010] The preparation of the polyethersulfone porous membrane includes: completely dissolving 30-40 parts by mass of 3% modified MOF nanoparticles in 200-300 parts by mass of 20% dimethylacetamide solution at room temperature, then adding 80-120 parts by mass of 18% PES polyethersulfone solution to the mixed solution, stirring at 80-120 RPM for 8-12 hours at room temperature to obtain a uniform casting solution, degassing the casting solution under vacuum for 1 hour and coating it onto a clean glass plate by casting method, then immersing the modified membrane in ultrapure water for 48 hours to remove residual substances in the membrane, and finally drying the prepared modified membrane in a forced-air drying oven at 40℃ for 24 hours.

[0011] The preparation of MOF nanoparticles includes: rapidly pouring 80 parts of a 20% Zn(NO3)2·6H2O methanol solution into 120-150 parts of a 5% (w / w) mixed methanol solution at room temperature, stirring and reacting for 3 hours, centrifuging at 200 RPM for 10 minutes, washing with methanol 3 times, and then collecting the modified MOF nanoparticles and drying them in a vacuum oven for 24 hours.

[0012] The mixed methanol solution is obtained by mixing diphenylimidazolium and dimethoxyphenylbutenoic acid in a methanol solution at a ratio of 3:2-4.

[0013] The advantages and beneficial effects of this invention are as follows:

[0014] 1. This invention provides a method for recycling ternary wastewater. By selecting a polyethersulfone separation membrane, modifying it to improve its permeability and selective separation, and improving the membrane's antifouling properties and extending its service life, the efficiency of ternary wastewater recycling is increased.

[0015] 2. Compared to the original PES membrane, the dense layer on the surface of the MOF-modified membrane is thinner. By reducing the thickness of the dense skin layer on the surface of the modified membrane, the transport resistance of the membrane can be effectively reduced, thereby improving the permeation performance of the modified membrane. However, because the membrane layer is thinner, the antifouling properties of the membrane are also affected and reduced to some extent.

[0016] 3. Therefore, this invention etches and grafts small molecule dimethoxyphenylbutyric acid onto the surface of MOF and introduces this synthesized functionalized MOF material as a filler into the PES matrix. As a hydrophilic modifier, dimethoxyphenylbutyric acid easily entangles and binds with MOF and polysulfone molecules, resulting in relatively fast phase separation on the membrane surface and easy formation of a dense layer. This hinders further inward diffusion of non-solvents, causing small aggregates in the support layer to aggregate and become unable to be pushed apart. Consequently, a large number of sponge-like pores are formed in the membrane matrix. When exchange occurs at the interface of the nascent membrane fibers, the strong hydrophilicity of dimethoxyphenylbutyric acid drives phase separation to develop rapidly, gradually causing the finger-like pores to disappear and develop into a sponge-like structure. The large number of sponge-like pores can significantly reduce the transport resistance of the permeate in the membrane, thereby further improving the permeation performance of the modified membrane.

[0017] 4. MOFs synergistically etched and surface-functionalized with dimethoxyphenylbutyric acid not only retain the high-porosity structure of MOFs but also exhibit improved hydrophilicity. Furthermore, the introduction of these hydrophilic molecules and their uniform entanglement with polysulfone molecules effectively immobilize MOF additives on the modified membrane, thereby enhancing the stability of the MOF additives within the membrane. This significantly improves the membrane's permeate flux and antifouling performance, ultimately extending its lifespan. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the embodiments. In the following embodiments, the treatment process for ternary wastewater is as follows: First, 10% sulfuric acid is added to the ternary wastewater to remove heavy metals, and the mixture is filtered. Then, 20% liquid alkali is added to the filtrate to adjust the pH to above 11.5. The temperature is then raised to 90°C, and the mixture enters the distillation column's ammonia removal system. The resulting ammonia water is recycled. The bottom liquid undergoes security filtration and membrane treatment to obtain pure water, which is also recycled. The concentrate undergoes MVR evaporation and crystallization treatment to obtain sodium sulfate crystals and condensate, which are then recovered. The specific membrane process is shown in the following embodiments and comparative examples.

[0019] Example 1

[0020] The preparation of MOF nanoparticles includes: rapidly pouring 80 parts of a 20% Zn(NO3)2·6H2O methanol solution into a mixed methanol solution of 135 parts of a 5% diphenylimidazolium and dimethoxyphenylbutenoic acid in a 3:3 ratio at room temperature, stirring and reacting for 3 hours, centrifuging at 200 RPM for 10 minutes, washing three times with methanol, and then collecting the modified MOF nanoparticles and drying them in a vacuum oven for 24 hours.

[0021] The preparation of polyethersulfone porous membrane includes: completely dissolving 35 parts by mass of 3% modified MOF nanoparticles in 250 parts by mass of 20% dimethylacetamide solution at room temperature, then adding 100 parts by mass of 18% PES polyethersulfone solution to the mixed solution, stirring at 100 RPM for 10 h at room temperature to obtain a uniform casting solution, degassing the casting solution under vacuum for 1 h and coating it onto a clean glass plate by casting method, then immersing the modified membrane in ultrapure water for 48 h to remove residual substances in the membrane, and finally drying the prepared modified membrane in a forced-air drying oven at 40℃ for 24 h.

[0022] Example 2

[0023] The preparation of MOF nanoparticles includes: rapidly pouring 80 parts of a 20% Zn(NO3)2·6H2O methanol solution into a mixed methanol solution of 120 parts of a 5% diphenylimidazolium and dimethoxyphenylbutenoic acid in a 3:2 ratio at room temperature, stirring and reacting for 3 hours, centrifuging at 200 RPM for 10 minutes, washing three times with methanol, and then collecting the modified MOF nanoparticles and drying them in a vacuum oven for 24 hours.

[0024] The preparation of the polyethersulfone porous membrane includes: completely dissolving 40 parts by mass of 3% modified MOF nanoparticles in 200 parts by mass of 20% dimethylacetamide solution at room temperature, then adding 120 parts by mass of 18% PES polyethersulfone solution to the mixed solution, stirring at 80 RPM for 12 h at room temperature to obtain a uniform casting solution, degassing the casting solution under vacuum for 1 h and coating it onto a clean glass plate by casting method, then immersing the modified membrane in ultrapure water for 48 h to remove residual substances in the membrane, and finally drying the prepared modified membrane in a forced-air drying oven at 40℃ for 24 h.

[0025] Example 3

[0026] The preparation of MOF nanoparticles includes: rapidly pouring 80 parts of a 20% Zn(NO3)2·6H2O methanol solution into a mixed methanol solution of 150 parts of a 5% diphenylimidazolium and dimethoxyphenylbutenoic acid in a 3:4 ratio at room temperature, stirring and reacting for 3 hours, centrifuging at 200 RPM for 10 minutes, washing three times with methanol, and then collecting the modified MOF nanoparticles and drying them in a vacuum oven for 24 hours.

[0027] The preparation of polyethersulfone porous membrane includes: completely dissolving 30 parts by mass of 3% MOF nanoparticles in 200-300 parts by mass of 20% dimethylacetamide solution at room temperature, then adding 80 parts by mass of 18% PES polyethersulfone solution to the mixed solution, stirring at 120 RPM for 8 hours at room temperature to obtain a uniform casting solution, degassing the casting solution under vacuum for 1 hour and coating it onto a clean glass plate by casting method, then immersing the modified membrane in ultrapure water for 48 hours to remove residual substances in the membrane, and finally drying the prepared modified membrane in a forced-air drying oven at 40℃ for 24 hours.

[0028] Comparative Example 1

[0029] The difference between this comparative example and Example 1 is that the membrane treatment in this comparative example is polysulfone membrane treatment. The specific membrane preparation process is as follows: The preparation of the polyethersulfone porous membrane includes: adding 100 parts of a 18% PES polyethersulfone solution to 250 parts of a 20% dimethylacetamide solution at room temperature, stirring at 100 RPM for 10 hours at room temperature to obtain a uniform casting solution, degassing the casting solution under vacuum for 1 hour and coating it onto a clean glass plate by casting, then immersing the modified membrane in ultrapure water for 48 hours to remove residual substances in the membrane, and finally drying the prepared modified membrane in a forced-air drying oven at 40°C for 24 hours; the rest is the same as in Example 1.

[0030] Comparative Example 2

[0031] The difference between this comparative example and Example 1 is that the MOF nanoparticles are not modified in this comparative example. The specific membrane preparation process is as follows: Preparation of MOF nanoparticles: At room temperature, 80 parts of 20% Zn(NO3)2·6H2O methanol solution are quickly poured into 135 parts of 5% diphenylimidazolium methanol solution and stirred for 3 hours. Then, the mixture is centrifuged at 200 RPM for 10 minutes and washed 3 times with methanol. The modified MOF nanoparticles are then collected and dried in a vacuum oven for 24 hours.

[0032] The preparation of the polyethersulfone porous membrane includes: completely dissolving 35 parts by mass of 3% MOF nanoparticles in 250 parts by mass of 20% dimethylacetamide solution at room temperature, then adding 100 parts by mass of 18% PES polyethersulfone solution to the mixed solution, stirring at 100 RPM for 10 h at room temperature to obtain a uniform casting solution, degassing the casting solution under vacuum for 1 h and coating it onto a clean glass plate by casting method, then immersing the modified membrane in ultrapure water for 48 h to remove residual substances in the membrane, and finally drying the prepared modified membrane in a forced-air drying oven at 40°C for 24 h; the rest is the same as in Example 1.

[0033] Comparative Example 3

[0034] The difference between this comparative example and Example 1 is that the dimethoxyphenylbutenoic acid is benzotricarboxylic acid, while the rest is the same as in Example 1.

[0035] Comparative Example 4

[0036] The difference between this comparative example and Example 1 lies in the amount of dimethoxyphenylbutenoic acid added. The specific process is as follows: The preparation of MOF nanoparticles includes: at room temperature, 80 parts of a 20% Zn(NO3)2·6H2O methanol solution are rapidly poured into a mixed methanol solution obtained by mixing 135 parts of a 5% diphenylimidazole and dimethoxyphenylbutenoic acid in a 3:6 ratio, and the mixture is stirred and reacted for 3 hours. After stirring, the mixture is centrifuged at 200 RPM for 10 minutes and washed three times with methanol. The modified MOF nanoparticles are then collected and dried in a vacuum oven for 24 hours. The rest is the same as in Example 1.

[0037] Comparative Example 5

[0038] The difference between this comparative example and Example 1 lies in the amount of dimethoxyphenylbutenoic acid added. The specific process is as follows: The preparation of MOF nanoparticles includes: at room temperature, 80 parts of a 20% Zn(NO3)2·6H2O methanol solution are rapidly poured into a mixed methanol solution obtained by mixing 135 parts of a 5% diphenylimidazolium and dimethoxyphenylbutenoic acid in a 3:1 ratio, and the mixture is stirred and reacted for 3 hours. After stirring, the mixture is centrifuged at 200 RPM for 10 minutes and washed three times with methanol. The modified MOF nanoparticles are then collected and dried in a vacuum oven for 24 hours. The rest is the same as in Example 1.

[0039] Experiment 1: Performance Testing

[0040] The separation membranes prepared in Comparative Examples 1-3 and Comparative Examples 1-5 were compared, and the final system effluent parameters were tested. The results are shown in Table 1 below.

[0041] Table 1 Removal rate results

[0042] Group TP removal rate TN removal rate COD removal rate Example 1 98 95 99 Example 2 97 94 98 Example 3 97 94 99 Comparative Example 1 80 70 80 Comparative Example 2 86 79 88 Comparative Example 3 89 82 90 Comparative Example 4 94 90 95 Comparative Example 5 91 88 92

[0043] Experiment 2: Antifouling performance test

[0044] The antifouling performance of the membrane was evaluated by static adsorption of BSA protein. The concentration of the filtered solution was measured after adding 50 mg / L of BSA protein solution; the difference was taken as the adsorption capacity. The results are shown in Table 2.

[0045] Table 2 Antifouling performance test

[0046] Group Adsorption capacity (mg / L) Example 1 4.3 Example 2 4.2 Example 3 4.0 Comparative Example 1 37.2 Comparative Example 2 25.8 Comparative Example 3 17.5 Comparative Example 4 8.7 Comparative Example 5 12.9

Claims

1. A method for recycling and treating ternary wastewater, characterized in that, The processing method specifically includes the following steps: First, 10% sulfuric acid is added to the ternary wastewater to remove heavy metals, and then the mixture is filtered. 20% liquid alkali is added to the filtrate to adjust the pH to above 11.

5. The temperature is then raised to 90°C and the mixture enters the distillation tower deammoniation system. The resulting ammonia water is recycled. The bottom liquid is treated by a security filter and membrane to obtain pure water, which is recycled. The concentrate is treated by MVR evaporation and crystallization to obtain sodium sulfate crystals and condensate, which are then recycled separately. The membrane treatment involves a polyethersulfone porous membrane, prepared by: completely dissolving 30-40 parts by mass of 3% MOF nanoparticles in 200-300 parts by mass of 20% dimethylacetamide solution at room temperature; adding 80-120 parts by mass of 18% PES polyethersulfone solution to the mixed solution; stirring at 80-120 RPM at room temperature for 8-12 hours to obtain a uniform casting solution; degassing the casting solution under vacuum for 1 hour and coating it onto a clean glass plate using a casting method; immersing the modified membrane in ultrapure water for 48 hours to remove residual substances; and finally drying the prepared modified membrane in a 40°C forced-air drying oven for 24 hours. The preparation of MOF nanoparticles includes: rapidly pouring 80 parts of a 20% Zn(NO3)2•6H2O methanol solution into 120-150 parts of a 5% (w / w) mixed methanol solution at room temperature, stirring and reacting for 3 hours, centrifuging at 200 RPM for 10 minutes, washing with methanol 3 times, and then collecting the modified MOF nanoparticles and drying them in a vacuum oven for 24 hours. The mixed methanol solution is obtained by mixing diphenylimidazolium and dimethoxyphenylbutenoic acid in a methanol solution at a ratio of 3:2-4.