A method for preparing an ultraporous ceramic membrane for NMP purification

Abstract

This invention belongs to the field of ceramic membranes and electronic chemical recycling, specifically relating to a method for preparing an ultraporous ceramic membrane for NMP purification. The method includes the following steps: (1) pretreatment of the ceramic membrane; (2) modification treatment of the ceramic membrane; and (3) preparation of the ultraporous ceramic membrane for NMP purification. Compared with existing technologies, the advantages of this invention are: 1) This invention can efficiently purify NMP from NMP waste liquid with different impurity contents, has a wide range of applications, and does not generate new pollutants during the entire process. The process is mature and stable and can be applied to the recycling and comprehensive treatment of various NMP-containing waste liquids. 2) This invention uses specific ultraviolet (UV) light irradiation conditions to modify the ceramic membrane surface. The surface grafting polymerization technology mainly focuses on the formation of active centers. Furthermore, the UV grafting modification only occurs on the surface of the ceramic membrane material and does not damage the internal structure of the ceramic membrane material. The ceramic membrane has good stability, high purity of NMP waste liquid recovery, and few impurity ions.

Description

Technical Field

[0001] This invention belongs to the field of ceramic membranes and electronic chemical recycling, specifically relating to a method for preparing an ultraporous ceramic membrane for NMP purification. Background Technology

[0002] With the rapid development of the electronics industry, the requirements for ultra-clean, high-purity reagents are becoming increasingly stringent. N-methylpyrrolidone (NMP) is a highly polar aprotic solvent with advantages such as high boiling point, strong polarity, low viscosity, strong solubility, non-corrosiveness, low toxicity, good thermal stability, and complete miscibility with water, making it widely used in photoresist stripping solutions. Traditional production methods employ a two-step continuous synthesis of NMP using ZSM molecular sieve-based catalysts; however, limitations such as catalyst lifetime restrict its large-scale industrial production.

[0003] In the field of NMP recycling, NMP dehydration membrane pervaporation purification systems have been reported. Application number 202020778088.0 discloses a pervaporation membrane device for purifying NMP aqueous solutions. This device mainly includes a pervaporation membrane body, an atomization mechanism, a separation mechanism, and a condensation mechanism. By atomizing and pressurizing the NMP aqueous solution, the atomized NMP aqueous solution passes through the vaporization membrane assembly, achieving rapid purification of the NMP aqueous solution. However, the vaporization membrane in this device is costly and not pressure-resistant.

[0004] Application No. 201821973533.8 discloses an NMP dehydration membrane pervaporation purification system. This system mainly includes a gas booster pump, a first pervaporation membrane partition, a medium-temperature cooling chamber, and a second pervaporation membrane partition. This system utilizes the high-temperature characteristics of NMP gas to perform staged cooling and pervaporation filtration, separating the NMP gas from water vapor to ultimately obtain high-purity NMP reagent. However, this system has a relatively complex internal structure, is prone to impurity contamination, and is primarily designed for purifying existing NMP aqueous solutions, making it difficult to apply to various NMP waste liquid systems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an ultraporous ceramic membrane for NMP purification, addressing the problems existing in the prior art.

[0006] The technical solution adopted to achieve the purpose of this invention is as follows: a method for preparing an ultraporous ceramic membrane for NMP purification, comprising the following preparation steps:

[0007] 1) Pretreatment of ceramic membrane

[0008] Dimethyldichlorosilane was dissolved in chloroform to prepare a dimethyldichlorosilane solution. The ceramic membrane was immersed in the dimethyldichlorosilane solution. After immersion, the ceramic membrane was removed and rinsed with chloroform. The rinsed ceramic membrane was then heat-treated. After heat treatment, the ceramic membrane was ultrasonically cleaned in an ethanol solution to remove contaminants or adsorbed impurities. After cleaning, the ceramic membrane was immersed in pure water to displace the ethanol. The ceramic membrane was then dried to constant weight to obtain the pretreated ceramic membrane.

[0009] 2) Modification treatment of ceramic membranes

[0010] The pretreated ceramic membrane from step 1) was placed in a benzophenone / methanol solution and allowed to stand to allow benzophenone to precipitate on the surface of the ceramic membrane. The ceramic membrane was then removed and dried to allow the benzophenone to fully react on the surface of the ceramic membrane. The ceramic membrane was then pre-irradiated under ultraviolet light to initiate the hydrogen abstraction reaction of benzophenone. A dimethylsiloxane monomer aqueous solution was added dropwise, and the irradiation continued under the same ultraviolet light.

[0011] 3) Ultraporous ceramic membranes for NMP purification

[0012] After the irradiation in step 2), the ceramic membrane is taken out, rinsed with methanol / water solution, placed in pure water and allowed to stand, and then freeze-dried under vacuum to constant weight to obtain an ultraporous ceramic membrane for NMP purification.

[0013] Preferably, the ceramic membrane described in step 1) of the present invention is a tubular membrane or a dense multichannel membrane.

[0014] Preferably, when the ceramic membrane of the present invention is a tubular membrane, the membrane material is α-alumina; when the ceramic membrane is a dense multi-channel membrane, the membrane material is zirconium dioxide.

[0015] Preferably, the dimethyldichlorosilane solution in step 1) of the present invention has a concentration of 0.1-0.3 mol / L; and the soaking time is 12-36 h.

[0016] Preferably, the heat treatment described in step 1) of the present invention is performed at a temperature of 100°C for a time of 24 hours.

[0017] Preferably, the concentration of the benzophenone / methanol solution in step 2) of the present invention is 0.4-0.6 mol / L.

[0018] Preferably, in step 2) of the present invention, the pre-irradiation under ultraviolet light has a wavelength of 298-345nm, the pre-irradiation time is 7-9min, and the power of the ultraviolet high-pressure mercury lamp is 350-400W.

[0019] Preferably, the mass percentage of the dimethylsiloxane monomer aqueous solution in step 2) of the present invention is 3.5-5.8%.

[0020] Preferably, the irradiation time in step 2) of the present invention is 10-15 minutes.

[0021] Preferably, in step 3) of the present invention, the methanol / water solution has a volume ratio of methanol to water of 1:20.

[0022] Compared with the prior art, the technical advantages of the present invention are as follows:

[0023] 1) This invention can efficiently purify NMP from NMP waste liquid with different impurity contents. It has a wide range of applications and does not generate new pollutants in the entire process. The process is mature and stable and can be applied to the recycling and comprehensive treatment of various NMP-containing waste liquids.

[0024] 2) This invention uses specific ultraviolet (UV) light irradiation conditions to modify the surface of ultra-microporous ceramic membranes. The surface grafting polymerization technology is mainly reflected in the way active centers are formed. Furthermore, the UV grafting modification only occurs on the surface of the ceramic membrane material and will not damage the internal structure of the ceramic membrane material. The ceramic membrane has good stability and high purity and few impurity ions in the recovery of NMP waste liquid.

[0025] 3) Compared with other materials, ultra-microporous ceramic membranes are less prone to biofouling due to their biological inertness, which solves the problem of clogging that is often encountered in the NMP waste liquid recycling process, causing problems such as unstable operation, increased energy consumption, and frequent chemical cleaning.

[0026] 4) This invention uses an ultra-microporous ceramic membrane as the main modification material. Its porosity and high selective flux improve the transport controllability of the ceramic membrane. This invention selects ceramic membranes of different materials, primarily α-alumina and zirconium dioxide, and uses different ceramic membrane shapes to achieve high recovery efficiency and purity for various NMP waste liquids. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments. Example 1

[0028] A ceramic membrane (tubular membrane, pore size 100nm, outer diameter φ30mm, length 1016mm, number of pores 19, effective membrane area 0.24m²) was used. 2 Flux 2000 L / m 2The ceramic membrane (made of α-alumina, suitable pH 1-14, working pressure 0.3-0.6 MPa, backwash pressure difference 0.1-0.3 MPa) was immersed in a modified solution (0.15 mol / L modified solution prepared by dissolving dimethyldichlorosilane in chloroform) for 24 hours. After removal, the ceramic membrane was rinsed with chloroform, and the modification was repeated 3 times. The rinsed ceramic membrane was then placed in an oven for heat treatment at 100℃ for 24 hours. After heat treatment, the ceramic membrane was ultrasonically cleaned in an ethanol solution for 25 minutes to remove contaminants and adsorbed impurities from the microporous ceramic membrane. After cleaning, it was immersed in pure water for 35 minutes to gradually displace the ethanol, and dried at 75℃ to constant weight. The dried membrane was then placed in a 0.40 mol / L benzophenone / methanol solution and allowed to stand for 1.5 hours to allow benzophenone to precipitate on the surface of the ceramic membrane. The ceramic membrane was then removed and dried at room temperature for 2 hours to allow benzophenone to fully react on its surface. The membrane was then placed in a quartz reaction tube and pre-irradiated for 9 minutes under a 298 nm high-pressure mercury lamp at a power of 350 W to initiate the hydrogen abstraction reaction of benzophenone. A 3.5% (w / w) aqueous solution of dimethylsiloxane monomer was added dropwise, and irradiation continued under the same UV intensity for 10 minutes. After irradiation, the ceramic membrane was removed, rinsed in a methanol / water solution (methanol to water volume ratio 1:20) at 45°C for 2 hours, placed in pure water and allowed to stand for 12 hours, and then dried to constant weight using a vacuum freeze dryer to obtain the ultraporous ceramic membrane JINGXIE-A. This ceramic membrane is suitable for purifying NMP waste liquid with a moisture content of 10,000-20,000 ppm, impurity ion content (Mn, Cu, K, Na, Mg) of 500-1,000 μg / kg, total content of phosphate, sulfate, nitrate and chloride of 10,000-20,000 ppb, and relative density of 1.01-1.04. The purified NMP content is ≥99.9%. Example 2

[0029] A ceramic membrane (tubular membrane, pore size 100nm, outer diameter φ30mm, length 1016mm, number of pores 19, effective membrane area 0.24m²) was used. 2 Flux 2000 L / m 2The ceramic membrane (made of α-alumina, suitable pH 1-14, working pressure 0.3-0.6 MPa, backwash pressure difference 0.1-0.3 MPa) was immersed in a modification solution (0.1 mol / L modified solution prepared by dissolving dimethyldichlorosilane in chloroform) for 36 hours. After removal, the ceramic membrane was rinsed with chloroform, and the modification was repeated 3 times. The rinsed ceramic membrane was then placed in an oven for heat treatment at 100℃ for 24 hours. After heat treatment, the ceramic membrane was ultrasonically cleaned in an ethanol solution for 30 minutes to remove contaminants and adsorbed impurities. After cleaning, it was immersed in pure water for 30 minutes to gradually displace the ethanol, and dried at 75℃ to constant weight. The dried membrane was then placed in a 0.50 mol / L benzophenone / methanol solution and allowed to stand for 1.5 hours to allow benzophenone to precipitate on the surface of the ceramic membrane. The ceramic membrane was then removed and dried at room temperature for 2 hours to allow the benzophenone to fully react on the surface of the ceramic membrane. The ceramic membrane was then placed in a quartz reaction tube and pre-irradiated for 7 minutes under ultraviolet light (345 nm) from a high-pressure mercury lamp at a power of 400 W to initiate the hydrogen abstraction reaction of benzophenone. A 4.5% (w / w) aqueous solution of dimethylsiloxane monomer was added dropwise, and irradiation continued under the same ultraviolet light intensity for 10 minutes. After irradiation, the ceramic membrane was removed, rinsed in a methanol / water solution (methanol to water volume ratio 1:20) at 45°C for 2 hours, placed in pure water and allowed to stand for 10 hours, and then dried to constant weight using a vacuum freeze dryer to obtain the ultra-microporous ceramic membrane JINGXIE-B. This ceramic membrane is suitable for purifying NMP waste liquid with a moisture content >20000 ppm, impurity ion (Mn, Cu, K, Na, Mg) content >1000 μg / kg, total phosphate, sulfate, nitrate, and chloride content >20000 ppb, and relative density >1.02, achieving a purified NMP content ≥99.9%. Example 3

[0030] The ceramic membrane (dense multi-channel membrane, pore size 100nm, outer diameter φ80mm, length 865mm, pore count 191, effective membrane area 1.98m²) was used. 2 Flux 1800 L / m 2The ceramic membrane (made of zirconium dioxide, suitable pH 1-14, working pressure 0.1-0.3 MPa, backwash pressure difference 0.1-0.3 MPa) was immersed in a modification solution (prepared by dissolving dimethyldichlorosilane in chloroform to obtain a concentration of 0.3 mol / L) for 12 hours. After removal, the ceramic membrane was rinsed with chloroform, and the modification was repeated 3 times. The rinsed ceramic membrane was then placed in an oven for heat treatment at 100℃ for 24 hours. After heat treatment, the ceramic membrane was ultrasonically cleaned in an ethanol solution for 25 minutes to remove contaminants and adsorbed impurities. After cleaning, it was immersed in pure water for 30 minutes to gradually displace the ethanol, and dried at 75℃ to constant weight. The dried membrane was then placed in a 0.60 mol / L benzophenone / methanol solution and allowed to stand for 2 hours to allow benzophenone to precipitate on the surface of the ceramic membrane. The ceramic membrane was then removed and dried at room temperature for 1 hour to allow the benzophenone to fully react on the surface of the ceramic membrane. The ceramic membrane was then placed in a quartz reaction tube and pre-irradiated for 8 minutes under ultraviolet light (325 nm) from a high-pressure mercury lamp at a power of 380 W to initiate the hydrogen abstraction reaction of benzophenone. A 5.8% (w / w) aqueous solution of dimethylsiloxane monomer was added dropwise, and irradiation continued under the same ultraviolet light intensity for 15 minutes. After irradiation, the ceramic membrane was removed, rinsed in a methanol / water solution (methanol to water volume ratio 1:20) at 45°C for 2 hours, placed in pure water and allowed to stand for 12 hours, and then dried to constant weight using a vacuum freeze dryer to obtain the ultraporous ceramic membrane JINGXIE-C. This ceramic membrane is suitable for purifying NMP waste liquid with a moisture content >10000ppm, other organic solvent content >200ppm, impurity metal ion content (Mn, Cu, K, Na, Mg) content >500μg / kg, total impurity inorganic ion content (phosphate, sulfate, nitrate, chloride) >10000ppb, and relative density ≤1.03, with a purified NMP content ≥99.9%.

[0031] Table 1 compares the effects of different membranes on NMP waste liquid with low impurity content, and Table 2 compares the effects of different membranes on NMP waste liquid with high impurity content.

[0032] Table 1. Comparison of the effects of different membranes on NMP waste liquid with low impurity content.

[0033]

[0034] Table 2 Comparison of the treatment effects of different membranes on NMP waste liquid with high impurity content

[0035]

[0036] As can be seen from Tables 1 and 2, the different ultra-microporous ceramic membranes of the JINXIE series used in Examples 1-3 for NMP waste liquid with different impurity contents can all meet the requirements of NMP water content <100ppm, impurity metal ion content (Mn, Cu, K, Na, Mg) content <50μg / kg, total impurity inorganic ion content (phosphate, sulfate, nitrate, chloride) <1000ppb, and NMP content ≥99.9%. Compared with the existing vaporization membrane process, the NMP purification solution has high purity and low impurity content.

[0037] This invention employs a UV grafting method, setting specific UV irradiation conditions to generate free radicals on the polymer chains on the surface of an ultraporous ceramic membrane. These free radicals then further graft onto the membrane with modified monomers or branches composed of several monomers, resulting in a copolymerization reaction on the membrane surface to achieve modification. This surface grafting polymerization technology primarily focuses on the formation of active centers. Furthermore, UV grafting modification only occurs on the surface of the ultraporous ceramic membrane material, without damaging its internal structure. It exhibits good stability, high purity NMP recovery, and low impurity ion content, making it applicable to the recovery and treatment of various types of NMP wastewater. The market prospects are broad.

Claims

1. A method for preparing an ultraporous ceramic membrane for NMP purification, characterized in that: The preparation steps are as follows: 1) Pretreatment of ceramic membrane Dimethyldichlorosilane was dissolved in chloroform to prepare a dimethyldichlorosilane solution. The ceramic membrane was immersed in the dimethyldichlorosilane solution. After immersion, the ceramic membrane was removed and rinsed with chloroform. The rinsed ceramic membrane was then heat-treated. After heat treatment, the ceramic membrane was ultrasonically cleaned in an ethanol solution to remove contaminants or adsorbed impurities. After cleaning, the ceramic membrane was immersed in pure water to displace the ethanol. The ceramic membrane was then dried to constant weight to obtain the pretreated ceramic membrane. 2) Modification treatment of ceramic membranes The pretreated ceramic membrane from step 1) was placed in a benzophenone / methanol solution and allowed to stand to allow benzophenone to precipitate on the surface of the ceramic membrane. The ceramic membrane was then removed and dried to allow the benzophenone to fully react on the surface of the ceramic membrane. The ceramic membrane was then pre-irradiated under ultraviolet light to initiate the hydrogen abstraction reaction of benzophenone. Dimethylsiloxane monomer aqueous solution was then added dropwise and irradiated under the same ultraviolet light. 3) Preparation of ultraporous ceramic membranes for NMP purification After the irradiation in step 2), the ceramic membrane is taken out, rinsed with methanol / water solution, placed in pure water and allowed to stand, and then freeze-dried under vacuum to constant weight to obtain the ultraporous ceramic membrane for NMP purification.

2. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: The ceramic membrane mentioned in step 1) is a tubular membrane or a dense multichannel membrane.

3. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 2, characterized in that: When the ceramic membrane is a tubular membrane, the membrane material is α-alumina; when the ceramic membrane is a dense multi-channel membrane, the membrane material is zirconium dioxide.

4. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: The dimethyldichlorosilane solution mentioned in step 1) has a concentration of 0.1-0.3 mol / L; the soaking time is 12-36 h.

5. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: The heat treatment described in step 1) is performed at a temperature of 100°C for 24 hours.

6. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: The concentration of the benzophenone / methanol solution in step 2) is 0.4-0.6 mol / L.

7. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: In step 2), the pre-irradiation under ultraviolet light has a wavelength of 298-345nm, the pre-irradiation time is 7-9min, and the power of the ultraviolet high-pressure mercury lamp is 350-400W.

8. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: The mass percentage of the dimethylsiloxane monomer aqueous solution mentioned in step 2) is 3.5-5.8%.

9. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: Continue irradiation as described in step 2), with an irradiation time of 10-15 minutes.

10. The method for preparing an ultraporous ceramic membrane for NMP purification according to claim 1, characterized in that: The methanol / water solution mentioned in step 3) wherein the volume ratio of methanol to water is 1:20.

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