Method for recovering wastewater of hydrogen peroxide concentration rectifying tower

Abstract

The invention relates to the technical field of wastewater treatment, and discloses a method for recovering wastewater of a hydrogen peroxide concentration rectifying tower. According to the method, a vacuum evaporation, pervaporation and rectification recovery synergistic process is adopted, gradient utilization of energy is achieved through a heat pump system driven by steam waste heat, and hydrogen peroxide molecules are efficiently and selectively separated through a special composite membrane; the composite membrane is prepared by blending fluoroalkylated polyimide and surface modified titanium dioxide, the synergistic effect is enhanced through molecular structure modification and micro-nano composite, and the pollution resistance and the separation stability of the membrane are remarkably improved; a pervaporation trapped fluid is preheated and then mixed with a raw material liquid for rectification, and deep enrichment and purification of hydrogen peroxide are realized by combining a vacuum low-temperature evaporation technology. According to the method, the hydrogen peroxide component in the wastewater can be efficiently recovered, pollutant emission is greatly reduced, the resource recovery efficiency and the system operation stability are remarkably improved, and the method has outstanding industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more particularly to a method for recovering wastewater from a hydrogen peroxide concentration and rectification tower. Background Art

[0002] As an important inorganic chemical raw material, hydrogen peroxide is widely used in chemical synthesis, environmental disinfection, and other fields. During its concentration production process, the vapor phase generated by the falling film evaporator enters the bottom of the distillation tower, where it contacts the reflux pure water in a countercurrent manner to achieve mass transfer, and the chemical-grade hydrogen peroxide product is obtained at the bottom of the tower. In this process, a large amount of evaporating steam is condensed in the overhead condenser to form a distillate. Because this distillate contains a small amount of hydrogen peroxide, it cannot be directly recovered and usually needs to be transported to a sewage treatment system for treatment. Currently, direct biochemical degradation or oxidative decomposition processes are mostly used to treat this distillate. This not only wastes the hydrogen peroxide resource, but also increases the company's environmental treatment costs due to the large processing volume and the unique pollutant composition. Among existing recovery technologies, simple vacuum evaporation methods suffer from high energy consumption and the easy decomposition of hydrogen peroxide. Conventional membrane separation technologies are limited by shortcomings such as insufficient membrane material selectivity and poor anti-pollution performance, making efficient enrichment difficult. Therefore, the present invention provides a method for recovering wastewater from a hydrogen peroxide concentration distillation tower to address the above-mentioned technical problems. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a method for recovering wastewater from a hydrogen peroxide concentration distillation tower. This method can efficiently recover the hydrogen peroxide component in the wastewater, significantly reduce pollutant emissions, significantly improve resource recovery efficiency and system operation stability, and has outstanding industrial application value.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for recovering wastewater from a hydrogen peroxide concentration distillation tower comprises the following steps:

[0006] S1. Treat the distillate with a vacuum evaporation concentration process, control the vacuum degree in the tank to 0.08-0.09 MPa, heat with 70-75°C hot water at a mass ratio of (1.2-1.5):1 to the distillate, maintain the evaporation temperature at 45-50°C, and evaporate for 50-60 minutes to 1 / 5-1 / 4 of the original volume to obtain a concentrated mother liquor and secondary steam, which is condensed and reused;

[0007] S2. The concentrated mother liquor is introduced into a modified membrane pervaporation separation system using a composite membrane, with the membrane module temperature controlled at 40-45°C and the permeate side vacuum at 0.09-0.095 MPa. The material is fed at a flow rate of 50-80 L / h and separated until the volume of the retentate is 1 / 3-1 / 2 of the feed volume to obtain an enriched liquid;

[0008] S3, after the enriched liquid is preheated to 50-60°C, it is pumped into the middle feed port of the distillation tower at a flow rate of 80-120L / h for distillation;

[0009] S4. When the membrane flux drops to 60-70% of the initial value, flush the membrane assembly with 25-35℃ water in reverse for 15-20 minutes until the pH of the effluent reaches 6-7;

[0010] S5: The 70-80℃ secondary steam generated by S1 is introduced into the heat pump system and transferred to the S2 feed preheating section through the shell and tube heat exchanger to preheat the concentrated mother liquor to 35-40℃.

[0011] Preferably, the method for preparing the composite membrane in step S2 comprises the following steps:

[0012] A1. Add polyimide to mixed acid and nitrate at 20-30°C for 25-35 minutes. Immerse the product in 5-8% sodium thiosulfate and reduce it at 25-35°C for 30-40 minutes to obtain amino polyimide.

[0013] A2. Dissolve the amino polyimide in DMF, add 2,3,4,5-tetrafluorobenzoyl chloride and triethylamine, and react at 65-75°C for 5-7 hours. Then, pour into 3-5 times the volume of the mixed solvent and stir for 10-15 minutes to precipitate the polymer. Filter, wash, and vacuum dry to obtain the fluoroalkylated polyimide.

[0014] A3. Dissolve the fluoroalkylated polyimide and modified titanium dioxide in DMF and grind for 18-25 minutes. Add polyoxyethylene-b-polymethyl methacrylate and stir for 20-30 minutes to obtain a casting solution. Apply the solution to the support layer with a doctor blade to a wet film thickness of 70-90 μm. Allow the solution to separate at 20-30°C and a relative humidity of 55-65% for 25-35 minutes.

[0015] A4. The wet film was heated at 110-130°C for 0.5-1.5 hours, then raised to 240-260°C and held for 1.5-2.5 hours, and then raised to 290-310°C and held for 0.5-1.5 hours. Finally, the composite film was hot-pressed at 0.08-0.12 MPa and 140-160°C for 8-12 minutes.

[0016] Preferably, the preparation steps of the modified titanium dioxide in step A1 are: dispersing nano titanium dioxide in anhydrous ethanol, adding NDZ-201, shearing and dispersing at 60-80°C and 2000-3000 rpm for 15-25 minutes, then ultrasonically treating at 40-60KHz for 20-40 minutes, vacuum filtering, drying and crushing to obtain 30-40μm modified nano titanium dioxide.

[0017] Preferably, the mixed acid in step A1 is composed of nitric acid and sulfuric acid in a volume ratio of 1:(1-3), and the mixed solvent in step A2 is composed of ethanol and water in a volume ratio of (3-5):1.

[0018] Preferably, in step A1, the components include 8-10 parts of polyimide, 40-60 parts of mixed acid and 10-15 parts of sodium thiosulfate in parts by weight.

[0019] Preferably, the step A2 comprises 4-6 parts by weight of amino polyimide, 30-40 parts by weight of DMF, 0.25-0.3 parts by weight of 2,3,4,5-tetrafluorobenzoyl chloride and 0.4-0.6 parts by weight of triethylamine.

[0020] Preferably, the ingredients in step A3 are 8-10 parts by weight of fluoroalkylated polyimide, 45-55 parts of DMF, 0.2-0.3 parts of modified titanium dioxide, and 0.1-0.15 parts of polyoxyethylene-b-polymethyl methacrylate.

[0021] Preferably, in the step of preparing the modified titanium dioxide in step A1, the components by weight are 20-25 parts of nano titanium dioxide, 90-100 parts of anhydrous ethanol and 0.5-0.9 parts of NDZ-201.

[0022] Preferably, the treatment means in step A4 is heating at 110-130°C for 0.5-1.5h, heating to 240-260°C and keeping warm for 1.5-2.5h, heating to 290-310°C and keeping warm for 0.5-1.5h, and finally hot pressing at 0.08-0.12MPa and 140-160°C for 8-12min.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention adopts a synergistic process of vacuum evaporation, pervaporation and distillation recovery, combines heat pump coupling heat exchange to achieve energy cascade utilization, and maintains membrane performance through a specific cleaning strategy to construct a complete hydrogen peroxide recovery system. This method achieves preliminary concentration of the distillate under low temperature conditions through vacuum evaporation, avoids the decomposition of hydrogen peroxide due to high temperature, and ensures the recovery rate of the target component; the pervaporation separation system further enriches hydrogen peroxide with the help of the selective separation effect of the special composite membrane, and then mixes it with the raw material liquid for distillation to achieve deep purification. The synergistic effect of multiple processes greatly improves the resource recovery efficiency. At the same time, the heat pump system uses the waste heat of secondary steam generated by vacuum evaporation to preheat the pervaporation feed, achieving efficient energy recycling and reducing overall energy consumption; when the membrane flux decreases, water reverse flushing is used to restore membrane performance, effectively extending the service life of the membrane assembly and ensuring the long-term stability of the system, thereby improving recovery efficiency while reducing operating costs and pollutant emissions.

[0025] 2. The composite membrane of the present invention is prepared by nitrating and reducing polyimide to obtain amino polyimide, which is then modified by fluoroalkylation and blended with surface-modified titanium dioxide to obtain a casting solution, which is then processed by scraping, phase separation, and a series of heat treatments. In this preparation process, the fluoroalkylation modification gives the polyimide a specific molecular structure, which enables it to have excellent selective adsorption and permeability for hydrogen peroxide molecules; the surface-modified titanium dioxide enhances the mechanical strength and anti-pollution performance of the membrane through micro-nanocomposite with the fluoroalkylated polyimide, and the synergistic effect of the two significantly improves the separation stability of the membrane; the series of heat treatment steps further optimize the microstructure of the membrane, ensuring that the membrane maintains a high flux and selectivity during long-term operation, thereby providing reliable material support for the pervaporation separation process and ensuring the quality and separation efficiency of the enriched liquid. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used are purchased from conventional biochemical reagent stores unless otherwise specified. The quantitative experiments in the following examples were all repeated three times, and the data are the average or mean ± standard deviation of the three repeated experiments.

[0028] Polyimide was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number T25297;

[0029] Polyoxyethylene-b-polymethyl methacrylate was purchased from Xi'an Ruixi Biotechnology Co., Ltd.;

[0030] NDZ-201 was purchased from Hubei Rishengchang New Material Technology Co., Ltd., item number 67691-13-8.

[0031] Example 1

[0032] A method for recovering wastewater from a hydrogen peroxide concentration distillation tower comprises the following steps:

[0033] S1. The distillate was introduced into a vacuum evaporator, and the vacuum degree in the evaporator was set to 0.08 MPa. 70°C hot water was introduced into the heating jacket at a mass ratio of 1.2:1 to the distillate. The evaporation temperature was maintained at 45°C, and the stirring speed was continuously stirred at 200 rpm. The evaporation was continued for 60 min to 1 / 4 of the original volume to obtain a concentrated mother liquor and secondary steam, which was reused after condensation;

[0034] S2. The concentrated mother liquor is introduced into a modified membrane pervaporation separation system and separated by a composite membrane. The temperature of the membrane module is controlled at 40°C and the vacuum degree on the permeate side is 0.09 MPa. The feed rate is 50 L / h and the separation is carried out at a stirring speed of 150 rpm until the volume of the retained liquid is 1 / 2 of the feed amount to obtain an enriched liquid.

[0035] S3, after preheating the enriched liquid to 50°C, pump it into the middle feed port of the distillation tower at a flow rate of 80L / h for distillation;

[0036] S4. When the membrane flux drops to 60% of the initial value, use 25℃ water to reversely flush the membrane assembly for 20 minutes until the pH of the effluent reaches 6;

[0037] S5: The 70℃ secondary steam generated by S1 is introduced into the heat pump system and transferred to the S2 feed preheating section through the shell and tube heat exchanger to preheat the concentrated mother liquor to 35℃.

[0038] The method for preparing the composite film in step S2 comprises the following steps:

[0039] A1. 8 parts by weight of polyimide were added to 40 parts of a mixture of nitric acid and sulfuric acid in a volume ratio of 1:1, and the mixture was nitrated at 20°C with a stirring speed of 240 rpm for 35 minutes. The product was immersed in 10 parts of a 5% sodium thiosulfate solution and reduced at 25°C with a stirring speed of 200 rpm for 40 minutes to obtain an amino polyimide.

[0040] A2. Dissolve 4 parts of amino polyimide in 30 parts of DMF, add 0.25 parts of 2,3,4,5-tetrafluorobenzoyl chloride and 0.4 parts of triethylamine, and react at 65°C with a stirring speed of 280 rpm for 7 hours. Pour the reaction solution into 3 times the volume of a mixed solvent (ethanol and water volume ratio of 3:1), stir at 180 rpm for 15 minutes, precipitate the polymer, filter, wash, and vacuum dry to obtain the fluoroalkylated polyimide;

[0041] A3. Dissolve 8 parts of fluoroalkylated polyimide and 0.2 parts of modified titanium dioxide in 45 parts of DMF, grind and disperse at 340 rpm for 25 min, add 0.1 parts of polyoxyethylene-b-polymethyl methacrylate, and stir at 200 rpm for 30 min to obtain a casting solution. Apply the casting solution on the polyester support layer with a knife to control the wet film thickness to 70 μm. Allow to stand for phase separation at 20° C. and 55% relative humidity for 35 min.

[0042] A4. The wet film after phase separation was first heated at 110°C for 1.5 h, then heated to 240°C and kept warm for 2.5 h, then heated to 290°C and kept warm for 1.5 h, and finally hot-pressed at 0.08 MPa and 140°C for 12 min to obtain a composite membrane.

[0043] Among them, the preparation steps of the modified titanium dioxide in step A1 are as follows: 20 parts by weight of nano-titanium dioxide are dispersed in 90 parts of anhydrous ethanol, 0.5 parts of NDZ-201 are added, shear dispersion is carried out at 60°C and 2000 rpm for 25 minutes, and then ultrasonic treatment is carried out at a frequency of 40 kHz for 40 minutes. After vacuum filtration, drying and crushing, 40 μm modified titanium dioxide is obtained.

[0044] Example 2

[0045] A method for recovering wastewater from a hydrogen peroxide concentration distillation tower comprises the following steps:

[0046] S1. The distillate was introduced into a vacuum evaporator, and the vacuum degree in the evaporator was set to 0.082 MPa. 72°C hot water was introduced into the heating jacket at a mass ratio of 1.3:1 to the distillate. The evaporation temperature was maintained at 46°C. The stirring speed was continuously stirred at 210 rpm. The evaporation was continued for 58 min to 1 / 4 of the original volume to obtain a concentrated mother liquor and secondary steam, which was reused after condensation.

[0047] S2. The concentrated mother liquor is introduced into a modified membrane pervaporation separation system and separated by a composite membrane. The temperature of the membrane module is controlled at 42°C and the vacuum degree on the permeate side is controlled at 0.091 MPa. The feed rate is 55 L / h and the separation is carried out at a stirring speed of 160 rpm until the volume of the retained liquid is 1 / 2 of the feed amount to obtain an enriched liquid.

[0048] S3, after preheating the enriched liquid to 52°C, pump it into the middle feed port of the distillation tower at a flow rate of 85L / h for distillation;

[0049] S4. When the membrane flux dropped to 62% of the initial value, the membrane assembly was flushed in reverse with 27°C water for 19 minutes until the pH of the effluent reached 6.3;

[0050] S5: The 72℃ secondary steam generated by S1 is introduced into the heat pump system and transferred to the S2 feed preheating section through a shell and tube heat exchanger to preheat the concentrated mother liquor to 36℃.

[0051] The method for preparing the composite film in step S2 comprises the following steps:

[0052] A1. 9 parts by weight of polyimide were added to 42 parts of a mixture of nitric acid and sulfuric acid in a volume ratio of 1:2, and the mixture was nitrated at 21°C with a stirring speed of 250 rpm for 34 minutes. The product was then immersed in 11 parts of a 6% sodium thiosulfate solution and reduced at 26°C with a stirring speed of 210 rpm for 39 minutes to obtain an amino polyimide.

[0053] A2. Dissolve 5 parts of amino polyimide in 31 parts of DMF, add 0.26 parts of 2,3,4,5-tetrafluorobenzoyl chloride and 0.5 parts of triethylamine, and react at 67°C with a stirring speed of 285 rpm for 6.8 hours. Pour the reaction solution into 4 times the volume of a mixed solvent (ethanol and water volume ratio of 4:1), stir at 190 rpm for 14 minutes, precipitate the polymer, filter, wash, and vacuum dry to obtain the fluoroalkylated polyimide;

[0054] A3. Dissolve 9 parts of fluoroalkylated polyimide and 0.21 parts of modified titanium dioxide in 46 parts of DMF, grind and disperse at 345 rpm for 24 min, add 0.11 parts of polyoxyethylene-b-polymethyl methacrylate, and stir at 210 rpm for 29 min to obtain a casting solution. Apply the casting solution on a polyester support layer with a knife to control the wet film thickness to 75 μm. Allow to stand for phase separation at 22° C. and 56% relative humidity for 34 min.

[0055] A4. The wet film after phase separation was first heated at 113°C for 1.4 h, then heated to 244°C and kept warm for 2.4 h, then heated to 294°C and kept warm for 1.4 h, and finally hot pressed at 0.09 MPa and 142°C for 11 min to obtain a composite membrane.

[0056] Among them, the preparation steps of the modified titanium dioxide in step A1 are as follows: 21 parts of nano-titanium dioxide are dispersed in 91 parts of anhydrous ethanol, 0.6 parts of NDZ-201 are added, shear dispersion is carried out at 62°C and 2100 rpm for 24 minutes, and then ultrasonic treatment is carried out at a frequency of 42 kHz for 38 minutes. After vacuum filtration, drying and crushing, 38 μm modified titanium dioxide is obtained.

[0057] Example 3

[0058] A method for recovering wastewater from a hydrogen peroxide concentration distillation tower comprises the following steps:

[0059] S1. The distillate was introduced into a vacuum evaporator, and the vacuum degree in the evaporator was set to 0.084 MPa. 73°C hot water was introduced into the heating jacket at a mass ratio of 1.4:1 to the distillate. The evaporation temperature was maintained at 47°C. The stirring speed was continuously stirred at 220 rpm. The evaporation was continued for 56 min to 1 / 5 of the original volume to obtain a concentrated mother liquor and secondary steam, which was reused after condensation.

[0060] S2. The concentrated mother liquor is introduced into a modified membrane pervaporation separation system and separated by a composite membrane. The temperature of the membrane module is controlled at 43°C and the vacuum degree on the permeate side is 0.093 MPa. The feed rate is 60 L / h and the separation is carried out at a stirring speed of 170 rpm until the volume of the retained liquid is 1 / 2 of the feed amount to obtain an enriched liquid.

[0061] S3, after preheating the enriched liquid to 54°C, pump it into the middle feed port of the distillation tower at a flow rate of 90L / h for distillation;

[0062] S4. When the membrane flux dropped to 64% of the initial value, the membrane assembly was flushed in reverse with 29°C water for 17 minutes until the pH of the effluent reached 6.5.

[0063] S5: The 74°C secondary steam generated by S1 is introduced into the heat pump system and transferred to the S2 feed preheating section through a shell and tube heat exchanger to preheat the concentrated mother liquor to 37°C.

[0064] The method for preparing the composite film in step S2 comprises the following steps:

[0065] A1. 9 parts by weight of polyimide were added to 44 parts of a mixture of nitric acid and sulfuric acid in a volume ratio of 1:2, and the mixture was nitrated at 22°C with a stirring speed of 255 rpm for 32 minutes. The product was then immersed in 12 parts of a 7% sodium thiosulfate solution and reduced at 27°C with a stirring speed of 215 rpm for 37 minutes to obtain an amino polyimide.

[0066] A2. Dissolve 5 parts of amino polyimide in 33 parts of DMF, add 0.27 parts of 2,3,4,5-tetrafluorobenzoyl chloride and 0.55 parts of triethylamine, and react at 69°C with a stirring speed of 290 rpm for 6.6 hours. Pour the reaction solution into 4 times the volume of a mixed solvent (ethanol and water volume ratio of 4:1), stir at 195 rpm for 13 minutes, precipitate the polymer, filter, wash, and vacuum dry to obtain a fluoroalkylated polyimide;

[0067] A3. Dissolve 9 parts of fluoroalkylated polyimide and 0.3 parts of modified titanium dioxide in 47 parts of DMF, grind and disperse at 355 rpm for 22 min, add 0.13 parts of polyoxyethylene-b-polymethyl methacrylate, and stir at 220 rpm for 27 min to obtain a casting solution. Apply the casting solution on a polyester support layer with a knife to control the wet film thickness to 80 μm. Allow to stand for phase separation at 23° C. and 59% relative humidity for 32 min.

[0068] A4. The wet film after phase separation was first heated at 120°C for 1 h, then heated to 245°C and kept warm for 2 h, then heated to 300°C and kept warm for 0.8 h, and finally hot pressed at 0.1 MPa and 150°C for 10 min to obtain a composite membrane.

[0069] Among them, the preparation steps of the modified titanium dioxide in step A1 are as follows: 22 parts of nano-titanium dioxide are dispersed in 94 parts of anhydrous ethanol, 0.7 parts of NDZ-201 are added, shear dispersion is carried out at 64°C and 2300 rpm for 22 minutes, and then ultrasonic treatment is carried out at a frequency of 45KHz for 36 minutes. After vacuum filtration, drying and crushing, 36μm modified titanium dioxide is obtained.

[0070] Example 4

[0071] A method for recovering wastewater from a hydrogen peroxide concentration distillation tower comprises the following steps:

[0072] S1. The distillate was introduced into a vacuum evaporator, and the vacuum degree in the evaporator was set to 0.09 MPa. 75°C hot water was introduced into the heating jacket at a mass ratio of 1.5:1 to the distillate. The evaporation temperature was maintained at 50°C, and the stirring speed was continuously stirred at 260 rpm. The evaporation was continued for 50 min to 1 / 5 of the original volume to obtain a concentrated mother liquor and secondary steam, which was reused after condensation;

[0073] S2. The concentrated mother liquor is introduced into a modified membrane pervaporation separation system and separated by a composite membrane. The temperature of the membrane module is controlled at 50°C and the vacuum degree on the permeate side is controlled at 0.095 MPa. The feed rate is 80 L / h and the separation is carried out at a stirring speed of 200 rpm until the volume of the retained liquid is 1 / 2 of the feed amount to obtain an enriched liquid.

[0074] S3, after preheating the enriched liquid to 60°C, pump it into the middle feed port of the distillation tower at a flow rate of 120L / h for distillation;

[0075] S4. When the membrane flux drops to 70% of the initial value, use 35℃ water to reversely flush the membrane assembly for 15 minutes until the pH of the effluent reaches 7;

[0076] S5: The 80℃ secondary steam generated by S1 is introduced into the heat pump system and transferred to the S2 feed preheating section through the shell and tube heat exchanger to preheat the concentrated mother liquor to 40℃.

[0077] The method for preparing the composite film in step S2 comprises the following steps:

[0078] A1. 10 parts by weight of polyimide were added to 60 parts of a mixture of nitric acid and sulfuric acid in a volume ratio of 1:3, and the mixture was nitrated at 30°C with a stirring speed of 300 rpm for 25 minutes. The product was immersed in 15 parts of an 8% sodium thiosulfate solution and reduced at 35°C with a stirring speed of 250 rpm for 30 minutes to obtain an amino polyimide.

[0079] A2. Dissolve 6 parts of amino polyimide in 40 parts of DMF, add 0.3 parts of 2,3,4,5-tetrafluorobenzoyl chloride and 0.6 parts of triethylamine, and react at 75°C with a stirring speed of 330 rpm for 5 hours. Pour the reaction solution into 5 times the volume of a mixed solvent (ethanol and water volume ratio of 5:1), stir at 230 rpm for 10 minutes, precipitate the polymer, filter, wash, and vacuum dry to obtain a fluoroalkylated polyimide;

[0080] A3. Dissolve 10 parts of fluoroalkylated polyimide and 0.3 parts of modified titanium dioxide in 55 parts of DMF, grind and disperse at 380 rpm for 18 min, add 0.15 parts of polyoxyethylene-b-polymethyl methacrylate, and stir at 260 rpm for 20 min to obtain a casting solution. Apply the casting solution on the polyester support layer with a knife to control the wet film thickness to 90 μm. Allow to stand for phase separation at 30°C and 66% relative humidity for 25 min.

[0081] A4. The wet film after phase separation was first heated at 130°C for 0.5h, then heated to 260°C and kept warm for 1.5h, then heated to 310°C and kept warm for 0.5h, and finally hot pressed at 0.12MPa and 160°C for 8min to obtain a composite membrane.

[0082] The preparation steps of the modified titanium dioxide in step A1 are as follows: 25 parts of nano-titanium dioxide are dispersed in 100 parts of anhydrous ethanol, 0.9 parts of NDZ-201 are added, and shear dispersion is carried out at 80°C and 3000 rpm for 15 minutes, followed by ultrasonic treatment at 60 kHz for 20 minutes, and vacuum filtration, drying and crushing to obtain 30 μm modified titanium dioxide.

[0083] Example 5

[0084] A method for recovering wastewater from a hydrogen peroxide concentration distillation tower comprises the following steps:

[0085] S1. The distillate was introduced into a vacuum evaporator, and the vacuum degree in the evaporator was set to 0.09 MPa. 75°C hot water was introduced into the heating jacket at a mass ratio of 1.5:1 to the distillate. The evaporation temperature was maintained at 50°C, and the stirring speed was continuously stirred at 250 rpm. The evaporation was continued for 55 min to 1 / 5 of the original volume to obtain a concentrated mother liquor and secondary steam, which was reused after condensation;

[0086] S2. The concentrated mother liquor is introduced into a modified membrane pervaporation separation system and separated by a composite membrane. The temperature of the membrane module is controlled at 50°C and the vacuum degree on the permeate side is 0.094 MPa. The feed rate is 70 L / h and the separation is carried out at a stirring speed of 200 rpm until the volume of the retained liquid is 1 / 2 of the feed amount to obtain an enriched liquid.

[0087] S3, after preheating the enriched liquid to 60°C, pump it into the middle feed port of the distillation tower at a flow rate of 100 L / h for distillation;

[0088] S4. When the membrane flux drops to 70% of the initial value, use 35℃ water to reversely flush the membrane assembly for 15 minutes until the pH of the effluent reaches 7;

[0089] S5: The 7080℃ secondary steam generated by S1 is introduced into the heat pump system and transferred to the S2 feed preheating section through the shell and tube heat exchanger to preheat the concentrated mother liquor to 40℃.

[0090] The method for preparing the composite film in step S2 comprises the following steps:

[0091] A1. 10 parts by weight of polyimide were added to 60 parts of a mixture of nitric acid and sulfuric acid in a volume ratio of 1:3, and the mixture was nitrated at 30°C with a stirring speed of 300 rpm for 30 min. The product was immersed in 14 parts of a 6% sodium thiosulfate solution and reduced at 35°C with a stirring speed of 240 rpm for 35 min to obtain an amino polyimide.

[0092] A2. Dissolve 6 parts of amino polyimide in 40 parts of DMF, add 0.28 parts of 2,3,4,5-tetrafluorobenzoyl chloride and 0.5 parts of triethylamine, and react at 75°C with a stirring speed of 320 rpm for 6 hours. Pour the reaction solution into 5 times the volume of a mixed solvent (ethanol and water volume ratio of 4:1), stir at 220 rpm for 12 minutes, precipitate the polymer, filter, wash, and vacuum dry to obtain the fluoroalkylated polyimide;

[0093] A3. Dissolve 10 parts of fluoroalkylated polyimide and 0.2 parts of modified titanium dioxide in 54 parts of DMF, grind and disperse at 360 rpm for 20 min, add 0.14 parts of polyoxyethylene-b-polymethyl methacrylate, and stir at 260 rpm for 24 min to obtain a casting solution. Apply the casting solution on the polyester support layer with a knife to control the wet film thickness to 85 μm. Allow to stand for phase separation at 28° C. and relative humidity of 65% for 30 min.

[0094] A4. The wet film after phase separation was first heated at 125°C for 0.6 h, then heated to 260°C and kept warm for 1.5 h, then heated to 300°C and kept warm for 0.6 h, and finally hot pressed at 0.1 MPa and 150°C for 10 min to obtain a composite membrane.

[0095] The preparation steps of the modified titanium dioxide in step A1 are as follows: 25 parts of nano-titanium dioxide are dispersed in 100 parts of anhydrous ethanol, 0.6 parts of NDZ-201 are added, and shear dispersion is carried out at 80°C and 2000 rpm for 20 minutes, followed by ultrasonic treatment at 60 kHz for 25 minutes, and vacuum filtration, drying and crushing to obtain 30 μm modified titanium dioxide.

[0096] Comparative Example 1

[0097] A method for recovering hydrogen peroxide wastewater differs from Example 5 in that a non-fluoroalkylated polyimide membrane is used in step A2 of composite membrane preparation. Specifically, the fluoroalkylation reaction in step A2 is omitted, and the amino-modified polyimide prepared in step A1 is directly blended with modified titanium dioxide to form a cast membrane. Other process conditions are the same as in Example 5.

[0098] Comparative Example 2

[0099] A method for recovering hydrogen peroxide wastewater differs from Example 5 in that modified titanium dioxide is not added in step A3 during composite membrane preparation. Specifically, the amount of modified titanium dioxide in step A3 is reduced to 0 parts, and the casting solution is prepared using only fluoroalkylated polyimide and polyoxyethylene-b-polymethyl methacrylate. Other process conditions are the same as in Example 5.

[0100] Comparative Example 3

[0101] A method for recovering hydrogen peroxide wastewater differs from Example 5 in that an unmodified polysulfone membrane is used in step S2 instead of the special composite membrane. Specifically, a commercial polysulfone ultrafiltration membrane is directly used as the composite membrane, and other process conditions are identical to those of Example 5.

[0102] Comparative Example 4

[0103] A method for recovering hydrogen peroxide wastewater differs from Example 5 in that the distillation cycle step is omitted. Specifically, step S3 is omitted, and the enriched liquid preheating and distillation operations of mixing with the raw liquid are not performed. The enriched liquid obtained in the pervaporation unit is directly output as the final product. Other process conditions and parameters are the same as in Example 5.

[0104] Comparative Example 5

[0105] A method for recovering hydrogen peroxide wastewater differs from Example 5 in that the vacuum evaporation concentration step S1 is omitted. Specifically, the distillate from the rectification tower is directly introduced into the pervaporation separation system without concentration treatment. Other process conditions and composite membrane preparation parameters are the same as those in Example 5.

[0106] Performance Testing

[0107] The performance tests of the hydrogen peroxide wastewater recovery methods of Examples 1-5 and Comparative Examples 1-5 were performed, and the test results are shown in Table 1 below.

[0108] Table 1:

[0109] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Yield % 91.28 92.56 93.57 90.89 93.85 85.92 87.10 76.58 91.67 68.42 purity% 98.53 98.72 99.01 98.34 99.54 92.08 95.46 88.22 91.15 95.08

[0110] The hydrogen peroxide yield and purity of Examples 1-5 were both maintained at high levels, with yields generally exceeding 90%, reaching a maximum of 93.85%, and purities approaching or exceeding 98%, reaching a maximum of 99.54%. This demonstrates that the coordinated process of vacuum evaporation, pervaporation, and distillation, combined with the application of specialized composite membranes and the cascaded utilization of heat pump energy, can effectively improve hydrogen peroxide recovery efficiency and final product purity. The coordinated coordination of various process steps plays a key role in improving resource recovery.

[0111] The yield and purity of Comparative Examples 1-5 are significantly lower than those of the embodiment. Comparative Example 1 may be due to the fact that the composite membrane is not modified by fluoroalkylation, which reduces the selectivity for hydrogen peroxide molecules and leads to a decrease in separation effect; Comparative Example 2 lacks modified titanium dioxide, and the membrane's anti-pollution and structural stability are insufficient, affecting the long-term separation efficiency; Comparative Example 3 uses an ordinary membrane instead of a special composite membrane, and the separation performance of the membrane cannot meet the requirements of efficient enrichment; Comparative Example 4 omits the distillation step, and cannot achieve deep purification of the enriched liquid, and the purity is naturally reduced; Comparative Example 5 does not undergo vacuum evaporation pretreatment, and the raw liquid concentration is low, which increases the separation load of pervaporation, resulting in a decrease in yield.

[0112] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for recovering wastewater from a hydrogen peroxide concentration distillation tower, characterized in that: The following steps are involved: S1. The distillate is treated by vacuum evaporation and concentration process to obtain concentrated mother liquor and secondary steam, which is condensed and reused; S2, introducing the concentrated mother liquor into a modified membrane pervaporation separation system, and performing separation treatment using a composite membrane to obtain an enriched liquid; S3, preheating the enriched liquid and pumping it into the middle feed port of the distillation tower for distillation; S4. When the membrane flux drops to 60-70% of the initial value, use water to reversely flush the membrane assembly until the pH of the effluent is 6-7; S5, using heat pump coupled heat exchange technology, introduces the secondary steam generated by S1 into the heat pump system, transfers heat to the S2 feed preheating section through the shell and tube heat exchanger, and preheats the concentrated mother liquor.

2. A method for recovering wastewater from a hydrogen peroxide concentration and rectification tower according to claim 1, characterized in that: The method for preparing the composite film in step S2 comprises the following steps: A1. The polyimide is added to the mixed acid for nitration reaction, and the product is immersed in sodium thiosulfate for reduction to obtain an amino polyimide; A2. Dissolve the amino polyimide in DMF, add 2,3,4,5-tetrafluorobenzoyl chloride and triethylamine to react, pour the reaction solution into a mixed solvent, stir, precipitate the polymer, filter, wash, and vacuum dry to obtain a fluoroalkylated polyimide; A3. The fluoroalkylated polyimide and modified titanium dioxide were dissolved in DMF, ground and dispersed, and then polyoxyethylene -b- polymethyl methacrylate was added, stirred to obtain a casting solution, applied to the support layer, and allowed to stand for phase separation; A4. The wet film after phase separation is heated, heated and kept warm, and hot-pressed in sequence to obtain a composite membrane.

3. A method for recovering wastewater from a hydrogen peroxide concentration and rectification tower according to claim 1, characterized in that: The preparation steps of the modified titanium dioxide in step A1 are as follows: dispersing nano titanium dioxide in anhydrous ethanol, adding NDZ-201, and subjecting the mixture to shear dispersion, ultrasonic treatment, vacuum filtration, drying and crushing.

4. A method for recovering wastewater from a hydrogen peroxide concentration and rectification tower according to claim 2, characterized in that: The mixed acid in step A1 is composed of nitric acid and sulfuric acid in a volume ratio of 1:(1-3), and the mixed solvent in step A2 is composed of ethanol and water in a volume ratio of (3-5):

1.

5. A method for recovering wastewater from a hydrogen peroxide concentration and rectification tower according to claim 2, characterized in that: In the step A1, the components include 8-10 parts of polyimide, 40-60 parts of mixed acid and 10-15 parts of sodium thiosulfate in parts by weight.

6. A method for recovering wastewater from a hydrogen peroxide concentration distillation tower according to claim 2, characterized in that: In step A2, the following components are prepared by weight: 4-6 parts of amino polyimide, 30-40 parts of DMF, 0.25-0.3 parts of 2,3,4,5-tetrafluorobenzoyl chloride, and 0.4-0.6 parts of triethylamine.

7. A method for recovering wastewater from a hydrogen peroxide concentration and rectification tower according to claim 2, characterized in that: In step A3, the components, by weight, include 8-10 parts of fluoroalkylated polyimide, 45-55 parts of DMF, 0.2-0.3 parts of modified titanium dioxide, and 0.1-0.15 parts of polyoxyethylene-b-polymethyl methacrylate.

8. A method for recovering wastewater from a hydrogen peroxide concentration and rectification tower according to claim 3, characterized in that: In the preparation step of the modified titanium dioxide in step A1, the following components are used in parts by weight: 20-25 parts of nano titanium dioxide, 90-100 parts of anhydrous ethanol, and 0.5-0.9 parts of NDZ-201.

9. A method for recycling wastewater from a hydrogen peroxide concentration and rectification tower according to claim 1, characterized in that: The treatment means in step A4 is to heat at 110-130° C. for 0.5-1.5 h, heat to 240-260° C. and keep warm for 1.5-2.5 h, heat to 290-310° C. and keep warm for 0.5-1.5 h, and finally hot press at 0.08-0.12 MPa and 140-160° C. for 8-12 min.