Recovery method of photoresist stripping waste liquid

Abstract

The invention discloses a photoresist stripping waste liquid recovery method, which belongs to the technical field of waste liquid treatment, and comprises the following steps: carrying out centrifugal separation treatment on photoresist stripping waste liquid to remove polymer solid impurities in the photoresist stripping waste liquid to obtain pretreated stripping waste liquid; adding a bentonite-based adsorption material into the pretreated stripping waste liquid, stirring, and performing magnetic separation through a magnet to obtain purified stripping waste liquid; carrying out reduced pressure rectification treatment on the purified stripping waste liquid to obtain a recovered stripping liquid and a high-boiling-point substance; according to the recycling method, the high-concentration stripping liquid can be recycled, meanwhile, metal ions, moisture and high-molecular solid impurities influencing the product quality are removed, a dehydrating tower is not needed for dehydration treatment, and the recycling method has the advantages of being simple in process, small in occupied area of equipment and the like; and meanwhile, the pollution of the stripping waste liquid to the environment is also reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of waste liquid treatment, and in particular relates to a method for recovering photoresist stripping waste liquid. Background Art

[0002] In recent years, with the rapid development of my country's economy, an increasing number of electronic products have appeared in the public eye, primarily including LCDs and chips. In the production of modern electronic products, factories use large amounts of photoresist to develop circuit boards. After completing its task of protecting the chips, the photoresist is stripped. The photoresist stripping process involves transferring the photoresist, which has certain strength, adhesion, and high charge density, from the chip into a stripping solution, where it dissolves in an organic solvent.

[0003] Stripping fluid, a wet electronic chemical, primarily consists of organic solvents and a small amount of water. Organic solvents are important chemical materials with a wide range of applications in coatings, electrochemistry, adhesives, paints, and cleaning agents. Stripping fluid is often used to remove photoresist during the film stripping process in electronic product manufacturing, but this produces a significant amount of waste stripping fluid that is difficult to dispose of. Photoresist waste stripping fluid contains large amounts of photoresist, water, and organic solvents, with the organic solvent content being relatively high. If these wastes are not properly handled, they can lead to a large amount of pollutants entering the air or soil, producing numerous harmful substances and causing significant environmental pollution. Furthermore, organic solvents can severely harm water bodies and trigger various environmental problems. They can also produce harmful gases such as carbon monoxide, as well as industrial nitrogen oxides and sulfides that contribute to the greenhouse effect, among other environmental issues.

[0004] Organic solvents refer to solvents that have certain toxicity, good compatibility with environmental media, and are recyclable. Currently, waste stripping liquids mainly include N-methylformamide (NMF), diethylene glycol monomethyl ether (MDG), diethylene glycol monobutyl ether (BDG), organic amines and alcohol ether solvent mixtures and water. These organic waste liquids are difficult to treat due to factors such as high concentration, complex composition, difficulty in degradation, and harm to the human body. With the development of science and technology, more and more researchers have found that waste photoresist stripping liquids contain many high-value organic solvents that can be recycled, and the recycling of these organic solvents can maximize resource utilization. At the same time, the production cost of stripping liquid is relatively high, and the recycled waste stripping liquid can reduce production costs. Therefore, by removing the organic solvents in waste photoresist stripping liquids, the emission of pollutants can be reduced and resource recycling can be achieved.

[0005] Analysis of organic solvents in waste stripping solutions revealed the following drawbacks in their recycling: (1) Due to the complexity and uncertainty of their molecular structures, some organic solvents are difficult to separate or degrade. (2) Some separation processes require high energy consumption and are not highly efficient, resulting in low organic solvent recovery rates and low purity of the recovered products. Summary of the Invention

[0006] The invention provides a method for recovering photoresist stripping waste liquid, which can solve the problems of high energy consumption and low product purity in the photoresist stripping waste liquid recovery process in the prior art.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A method for recovering photoresist stripping waste liquid comprises the following steps:

[0009] S1, centrifugally separating the photoresist stripping waste liquid to remove high molecular solid impurities in the photoresist stripping waste liquid to obtain a pretreated stripping waste liquid;

[0010] S2, adding bentonite-based adsorption material to the pre-treated stripping waste liquid, stirring and then performing magnetic separation with a magnet to obtain purified stripping waste liquid;

[0011] S3, vacuum distilling the purified stripping waste liquid to obtain a recovered stripping liquid and high-boiling products;

[0012] S4. Incinerate the high-boiling substances and recover the stripping liquid for testing.

[0013] First, the photoresist stripping waste liquid is centrifuged to remove high-molecular solid impurities, and then bentonite-based adsorption materials are added. By utilizing their excellent water absorption and metal ion adsorption properties, the moisture and metal ions in the pretreatment stripping waste liquid are removed, thereby reducing the corrosion of metal ions to equipment during the subsequent distillation process. It is also beneficial to obtain high-purity recycled stripping liquid.

[0014] In some embodiments, the photoresist stripping waste liquid in S1 mainly comprises N-methylformamide (NMF) and diethylene glycol methyl ether (MDG), and also includes water and metal ion impurities.

[0015] In some embodiments, the water content of the photoresist stripping waste liquid in S1 is 1-10%.

[0016] In some embodiments, the centrifugal separation treatment in S1 is performed by drum sedimentation centrifugation.

[0017] In some embodiments, the amount of bentonite-based adsorption material in S2 is 2-10% of the mass of the pre-treated stripping waste liquid.

[0018] In some embodiments, a refining tower is used for vacuum distillation in S3, and the refining tower is a sieve plate tower, the top pressure is set to 10-12 kPa, the top temperature is 90-120° C., and the bottom temperature is 130-160° C.

[0019] In some embodiments, the raw materials for preparing the bentonite-based adsorption material include unsaturated siloxane-modified magnetic bentonite, methacrylic acid, allyl hydroxamic acid, potassium persulfate, and N,N'-methylenebisacrylamide.

[0020] In some embodiments, the method for preparing the bentonite-based adsorption material comprises the following steps:

[0021] Unsaturated siloxane-modified magnetic bentonite is ultrasonically dispersed in deionized water, and then methacrylic acid, allyl hydroxamic acid ethanol solution, potassium persulfate and N,N'-methylenebisacrylamide are added and stirred for 15-30 minutes. Then the temperature is raised to 80°C, stirred for reaction for 2-4 hours, and naturally cooled to room temperature. After that, the mixture is transferred to an oven at 80-100°C and dried to constant weight, and finally crushed and passed through a 40-100 mesh sieve to obtain a bentonite-based adsorption material.

[0022] In some embodiments, the ratio of unsaturated siloxane-modified magnetic bentonite, deionized water, methacrylic acid, allyl hydroxamic acid ethanol solution, potassium persulfate and N,N'-methylenebisacrylamide is 3.4 g: 60-100 mL: 3-5 g: 30-50 mL: 0.1 g: 0.01-0.02 g, and the allyl hydroxamic acid ethanol solution is obtained by mixing allyl hydroxamic acid and 50-55°C anhydrous ethanol in a mass ratio of 1 g: 10 mL.

[0023] Bentonite has excellent water absorption and ion exchange properties. When directly applied to the treatment of photoresist stripping waste liquid, although water can be removed by adsorption, it is difficult to separate and new impurities are easily introduced into the stripping waste liquid by ion exchange. To this end, the present invention produces ferroferric oxide on the surface of bentonite by a coprecipitation method, giving the material magnetic response characteristics so that it can be quickly separated from the solid by a magnet. Unsaturated siloxane is then used to modify the magnetic bentonite to give it reaction activity. Finally, a polymerization reaction of unsaturated bonds is utilized to prepare a bentonite-based adsorption material carrying an absorbent resin using unsaturated siloxane-modified magnetic bentonite, methacrylic acid, allyl hydroxamic acid, potassium persulfate, and N,N'-methylenebisacrylamide as raw materials. The bentonite-based adsorption material not only has high water absorption, but also has better adsorption properties for metal ions due to the carboxyl and oxime groups carried on the surface, and can effectively adsorb water and metal ion impurities in the stripping waste liquid. In addition, due to the presence of the surface polymer, cation exchange between bentonite layers can be suppressed by a masking effect, thereby avoiding the introduction of new impurities into the recovered stripping liquid.

[0024] In some embodiments, the raw materials for preparing the unsaturated siloxane-modified magnetic bentonite include magnetic bentonite and unsaturated siloxane, and the mass ratio of the magnetic bentonite to the unsaturated siloxane is 100:5-10.

[0025] In some embodiments, the unsaturated siloxane is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltri(2-methoxyethoxy)silane, and methacryloxypropyltrimethoxysilane.

[0026] In some embodiments, the preparation process of the unsaturated siloxane modified magnetic swelling is as follows:

[0027] The magnetic bentonite was ultrasonically dispersed in an ethanol solution, and then unsaturated siloxane was added, stirred at 60-80°C for 12 hours, filtered, and the filter cake was washed and dried to obtain unsaturated siloxane-modified magnetic bentonite.

[0028] In some embodiments, the amount of ethanol solution is 10-15 times the mass of the magnetic bentonite, and the mass fraction of the ethanol solution is 50-90%.

[0029] In some embodiments, the magnetic bentonite is prepared by a co-precipitation method, and the preparation raw materials include calcium bentonite, FeCl3·6H2O, FeSO4·7H2O and sodium hydroxide, and the mass ratio of sodium bentonite, FeCl3·6H2O, FeSO4·7H2O and sodium hydroxide is 13.5-15.6:14.8:15.2:2.19.

[0030] In some embodiments, the magnetic bentonite preparation method is as follows:

[0031] Sodium bentonite, FeCl3·6H2O, FeSO4·7H2O and sodium hydroxide were added into deionized water, stirred evenly, and then heated to 60-80°C and stirred for reaction for 24 hours. After the reaction was completed, the mixture was filtered, and the filter cake was washed until the washing liquid was neutral, and dried to obtain magnetic bentonite.

[0032] In some embodiments, the preparation method of allylhydroxamic acid is as follows:

[0033] Keeping the system temperature below 10°C, methanol, hydroxylamine hydrochloride, sodium hydroxide, and methyl 2-(allyloxy)benzoate were added to the reaction kettle, stirred evenly, and then heated to 50-60°C and stirred for reaction for 4-6 hours. After the reaction was completed, the temperature was lowered to below 10°C, concentrated hydrochloric acid was added to adjust the pH to 5-6, and then the temperature was raised to 40-50°C. The mixture was filtered while hot and the methanol was recovered by vacuum distillation to obtain allyl hydroxamic acid.

[0034] The reaction structure is as follows:

[0035]

[0036] In some embodiments, the molar ratio of hydroxylamine hydrochloride, sodium hydroxide, and methyl 2-(allyloxy)benzoate is 1.05-1.2:2.05:1.

[0037] Beneficial effects of the present invention:

[0038] The present invention provides a method for recovering photoresist stripping waste liquid, which can recover high-concentration stripping liquid and simultaneously remove metal ions, moisture and high-molecular solid impurities that affect product quality. The purity of the recovered stripping liquid reaches above 99.4%, and the metal impurity content is lower than 0.1ppm. No dehydration tower is required for dehydration treatment. The method has the advantages of simple process, small equipment footprint, etc., is conducive to large-scale industrial promotion, and also reduces the pollution caused to the environment by the stripping waste liquid. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0040] The terms used in the examples of this application are for the purpose of describing specific implementation rules only and are not intended to limit this application. The singular forms "a", "an", "the" and "the" used in the implementation rules of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0041] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0042] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass described in the examples of this application may be a mass unit known in the chemical industry, such as μg, mg, g, kg, etc.

[0043] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0044] Sodium bentonite with a montmorillonite content of >70% was purchased from Liancheng County Henghe Bentonite Co., Ltd. The photoresist stripping waste liquid was sourced from a liquid crystal display manufacturer in Anhui Province. The indicators of the photoresist stripping waste liquid from the manufacturer were as follows: N-methylformamide (NMF) 31.40%, diethylene glycol monomethyl ether (MDG) 53.64%, copper ion content 2.572 mg / L, silver ion content 0.364 mg / L, water 8.5%, and high-boiling impurities 5.0%. Other raw materials, reagents, instruments, and equipment used in this application can be purchased on the market or prepared by existing methods.

[0045] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0046] Preparation Example 1

[0047] The preparation steps of bentonite-based adsorption materials are as follows:

[0048] 34g of unsaturated siloxane-modified magnetic bentonite was ultrasonically dispersed in 600mL of deionized water. 30g of methacrylic acid, 300mL of allylhydroxamic acid ethanol solution, 1g of potassium persulfate, and 0.1g of N,N'-methylenebisacrylamide were then added and stirred for 15 minutes. The mixture was then heated to 80°C and stirred for 2 hours. After cooling to room temperature, the mixture was dried in an oven at 80°C to constant weight and finally pulverized through a 40-mesh sieve to obtain a bentonite-based adsorbent. The allylhydroxamic acid ethanol solution was prepared by mixing allylhydroxamic acid and 50°C anhydrous ethanol in a mass ratio of 1g:10mL.

[0049] The preparation process of the unsaturated siloxane modified magnetic bentonite is as follows:

[0050] 50 g of magnetic bentonite was ultrasonically dispersed in 500 mL of 50 wt% ethanol solution, and then 2.5 g of vinyltrimethoxysilane was added. The mixture was stirred at 60° C. for 12 h, filtered, and the filter cake was washed and dried to obtain unsaturated siloxane-modified magnetic bentonite.

[0051] The magnetic bentonite preparation method is as follows:

[0052] 135 g of sodium bentonite, 148 g of FeCl3·6H2O, 152 g of FeSO4·7H2O and 21.9 g of sodium hydroxide were added to 1.5 L of deionized water, stirred evenly, and then heated to 60°C and stirred for reaction for 24 h. After the reaction was completed, the mixture was filtered, the filter cake was washed until the washing liquid was neutral, and dried to obtain magnetic bentonite.

[0053] The preparation method of allylhydroxamic acid is as follows:

[0054] Keeping the system temperature below 10°C, 2L of methanol, 1.05mol of hydroxylamine hydrochloride, 2.05mol of sodium hydroxide, and 1mol of methyl 2-(allyloxy)benzoate were added to the reactor and stirred evenly. The temperature was raised to 50°C and stirred for 6h. After the reaction was completed, the temperature was lowered to below 10°C, concentrated hydrochloric acid (36wt%) was added to adjust the pH to 5, and then the temperature was raised to 40°C. The mixture was filtered while hot and the methanol was recovered by distillation under reduced pressure to obtain allylhydroxamic acid.

[0055] Preparation Example 2

[0056] The preparation steps of bentonite-based adsorption materials are as follows:

[0057] 34g of unsaturated siloxane-modified magnetic bentonite was ultrasonically dispersed in 800mL of deionized water. Then, 40g of methacrylic acid, 400mL of allylhydroxamic acid ethanol solution, 1g of potassium persulfate, and 0.1g of N,N'-methylenebisacrylamide were added and stirred for 20 minutes. The mixture was then heated to 80°C and stirred for 3 hours. After cooling to room temperature, the mixture was transferred to an oven and dried at 90°C to constant weight. Finally, the mixture was pulverized and passed through a 60-mesh sieve to obtain a bentonite-based adsorbent. The allylhydroxamic acid ethanol solution was prepared by mixing allylhydroxamic acid and 52°C anhydrous ethanol in a mass ratio of 1g:10mL.

[0058] The preparation process of the unsaturated siloxane modified magnetic bentonite is as follows:

[0059] 50 g of magnetic bentonite was ultrasonically dispersed in 500 mL of 70 wt% ethanol solution, and then 4 g of vinyltriethoxysilane was added. The mixture was stirred at 70° C. for 12 h, filtered, and the filter cake was washed and dried to obtain unsaturated siloxane-modified magnetic bentonite.

[0060] The magnetic bentonite preparation method is as follows:

[0061] 145 g of sodium bentonite, 148 g of FeCl3·6H2O, 152 g of FeSO4·7H2O and 21.9 g of sodium hydroxide were added to 1.5 L of deionized water, stirred evenly, and then heated to 70°C and stirred for reaction for 24 h. After the reaction was completed, the mixture was filtered, the filter cake was washed until the washing liquid was neutral, and dried to obtain magnetic bentonite.

[0062] The preparation method of allylhydroxamic acid is as follows:

[0063] Keeping the system temperature below 10°C, 2L of methanol, 1.1mol of hydroxylamine hydrochloride, 2.05mol of sodium hydroxide, and 1mol of methyl 2-(allyloxy)benzoate were added to the reactor and stirred evenly. The temperature was raised to 55°C and stirred for reaction for 5h. After the reaction was completed, the temperature was lowered to below 10°C, concentrated hydrochloric acid (36wt%) was added to adjust the pH to 6, and then the temperature was raised to 45°C. The mixture was filtered while hot and the methanol was recovered by distillation under reduced pressure to obtain allylhydroxamic acid.

[0064] Preparation Example 3

[0065] The preparation steps of bentonite-based adsorption materials are as follows:

[0066] 34g of unsaturated siloxane-modified magnetic bentonite was ultrasonically dispersed in 1000mL of deionized water. 50g of methacrylic acid, 500mL of allylhydroxamic acid ethanol solution, 1g of potassium persulfate, and 0.2g of N,N'-methylenebisacrylamide were then added and stirred for 30 minutes. The mixture was then heated to 80°C and stirred for 4 hours. After cooling to room temperature, the mixture was dried in an oven at 100°C to constant weight and finally pulverized through a 100-mesh sieve to obtain the bentonite-based adsorbent. The allylhydroxamic acid ethanol solution was prepared by mixing allylhydroxamic acid and 55°C anhydrous ethanol in a mass ratio of 1g:10mL.

[0067] The preparation process of unsaturated siloxane-modified magnetic bentonite was the same as that of Preparation Example 2, and the preparation of allyl hydroxamic acid was the same as that of Preparation Example 1.

[0068] Comparative Example 1

[0069] The preparation of the bentonite-based adsorption material was different from that in Preparation Example 1 except that the allylhydroxamic acid ethanol solution was removed and the amount of methacrylic acid was adjusted from 30 g to 60 g.

[0070] Comparative Example 2

[0071] The preparation of the bentonite-based adsorption material is different from that in Preparation Example 1, except that the unsaturated siloxane-modified magnetic bentonite in Preparation Example 1 is replaced with an equal mass of magnetic bentonite, and the preparation process of the magnetic bentonite is the same as that in Preparation Example 1.

[0072] Comparative Example 3

[0073] This comparative example is magnetic bentonite, and the preparation process is the same as that of Preparation Example 1.

[0074] Example 1

[0075] A method for recovering photoresist stripping waste liquid comprises the following steps:

[0076] S1, performing drum sedimentation centrifugation on the photoresist stripping waste liquid to remove high molecular solid impurities in the photoresist stripping waste liquid to obtain a pretreated stripping waste liquid;

[0077] S2, adding the bentonite-based adsorption material of Preparation Example 1 to the pre-treated stripping waste liquid, wherein the amount of the bentonite-based adsorption material is 2% of the mass of the pre-treated stripping waste liquid, stirring, and then performing magnetic separation by a magnet to obtain a purified stripping waste liquid;

[0078] S3, vacuum distilling the purified stripping waste liquid to obtain a recovered stripping liquid and high-boiling products;

[0079] S4. Incinerate the high-boiling substances and recover the stripping liquid for testing.

[0080] In S3, a refining tower is used for vacuum distillation. The refining tower is a sieve plate tower with 18 plates, the 5th plate is fed, the reflux ratio is 1.5, the tower top pressure is set to 10 kPa, the tower top temperature is 90°C, and the tower bottom temperature is 130°C.

[0081] Example 2

[0082] A method for recovering photoresist stripping waste liquid is provided. Compared with Example 1, the only difference is that the amount of bentonite-based adsorption material used in this embodiment is 5% of the mass of the pre-treated stripping waste liquid.

[0083] Example 3

[0084] A method for recovering photoresist stripping waste liquid is provided. Compared with Example 1, the only difference is that the amount of bentonite-based adsorption material used in this embodiment is 10% of the mass of the pre-treated stripping waste liquid.

[0085] Example 4

[0086] A method for recovering photoresist stripping waste liquid, compared with Example 1, the only difference is that in Example S3, a refining tower is used for vacuum distillation, the refining tower is a sieve plate tower with 18 tower plates, the 5th plate is fed, the reflux ratio is 1.5, the tower top pressure is set to 11 kPa, the tower top temperature is 110°C, and the tower bottom temperature is 140°C.

[0087] Example 5

[0088] A method for recovering photoresist stripping waste liquid, compared with Example 1, the only difference is that in Example S3, a refining tower is used for vacuum distillation, the refining tower is a sieve plate tower with 18 tower plates, the 5th plate is fed, the reflux ratio is 1.5, the tower top pressure is set to 12 kPa, the tower top temperature is 120°C, and the tower bottom temperature is 160°C.

[0089] Example 6

[0090] A method for recovering photoresist stripping waste liquid is disclosed. Compared with Example 1, the only difference is that the bentonite-based adsorption material in Example 1 is replaced by the product prepared in Preparation Example 2 of equal mass.

[0091] Example 7

[0092] A method for recovering photoresist stripping waste liquid is disclosed. Compared with Example 1, the only difference is that the bentonite-based adsorption material in Example 1 is replaced by the product prepared in Preparation Example 3 of equal mass.

[0093] Example 8

[0094] A method for recovering photoresist stripping waste liquid is provided. Compared with Example 2, the only difference is that the bentonite-based adsorption material in Example 2 is replaced by the product prepared in Preparation Example 2 of equal mass.

[0095] Comparative Example 1

[0096] A method for recovering photoresist stripping waste liquid is disclosed. Compared with Example 1, the only difference is that the bentonite-based adsorption material in Example 1 is replaced by a product prepared in Control Example 1 of equal mass.

[0097] Comparative Example 2

[0098] A method for recovering photoresist stripping waste liquid is disclosed. Compared with Example 1, the only difference is that the bentonite-based adsorption material in Example 1 is replaced by the product prepared in Control Example 2 of equal mass.

[0099] Comparative Example 3

[0100] A method for recovering photoresist stripping waste liquid is disclosed. Compared with Example 1, the only difference is that the bentonite-based adsorption material in Example 1 is replaced by the product prepared in Control Example 3 of equal mass.

[0101] The recovered stripping solutions obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were subjected to yield calculation and quality testing. Recovery (%) = (NMF mass in original waste solution + MDG mass in original waste solution) / (NMF mass in recovered solution + MDG mass in recovered solution) × 100%, NMF and MDG concentrations (%) = NMF concentration + MDG concentration, NMF concentration (%) = NMF mass in recovered solution / total mass of recovered solution × 100%, MDG concentration (%) = MDG mass in recovered solution / total mass of recovered solution × 100%;

[0102] The results are shown in Table 1:

[0103] Table 1

[0104]

[0105] It can be seen from the data recorded in Table 1 that the purity of the recovered stripping liquid obtained in Examples 1 to 8 is above 99.4%, and the metal impurity content is less than 0.1 ppm. Specifically, it can be seen from the test results in Example 1 and Comparative Example 1 that when allyl hydroxamic acid is removed from the prepared bentonite-based adsorption material and the recovery process remains unchanged, the concentrations of NMF and MDG in the recovered liquid decrease, and the metal ion content increases significantly. It can be seen from the test results in Example 1 and Comparative Example 2 that when the unsaturated siloxane-modified magnetic bentonite in the prepared bentonite-based adsorption material is replaced with an equal mass of magnetic bentonite, the recovery rate of the stripping liquid decreases, the concentrations of NMF and MDG in the recovered liquid decrease, and the metal ion content increases significantly. It can be seen from the test results in Example 1 and Comparative Example 3 that when magnetic bentonite is used as an adsorption material to treat photoresist stripping waste liquid, not only the stripping liquid recovery rate is low, but also the concentration decreases, and the water content and metal ion content increase significantly. Therefore, the bentonite-based adsorption material prepared by the present invention is more conducive to obtaining a stripping liquid with higher purity and good recovery rate.

[0106] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0107] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering photoresist stripping waste liquid, characterized in that: The following steps are involved: S1, centrifugally separating the photoresist stripping waste liquid to remove high molecular solid impurities in the photoresist stripping waste liquid to obtain a pretreated stripping waste liquid; S2, adding bentonite-based adsorption material to the pre-treated stripping waste liquid, stirring and then performing magnetic separation with a magnet to obtain purified stripping waste liquid; S3, vacuum distilling the purified stripping waste liquid to obtain a recovered stripping liquid and high-boiling products; S4. Incinerate the high-boiling substances and recover the stripping liquid for testing.

2. The method for recycling photoresist stripping waste liquid according to claim 1, wherein: The main components of the photoresist stripping waste liquid in S1 are N-methylformamide and diethylene glycol methyl ether, and also include water and metal ion impurities.

3. The method for recycling photoresist stripping waste liquid according to claim 1, wherein: The amount of bentonite-based adsorption material in S2 is 2-10% of the mass of the pre-treated stripping waste liquid.

4. The method for recycling photoresist stripping waste liquid according to claim 1, wherein: In S3, a refining tower is used for vacuum distillation. The refining tower is a sieve plate tower with a top pressure of 10-12 kPa, a top temperature of 90-120° C., and a bottom temperature of 130-160° C.

5. The method for recycling photoresist stripping waste liquid according to claim 1, wherein: The method for preparing the bentonite-based adsorption material comprises the following steps: Unsaturated siloxane-modified magnetic bentonite is ultrasonically dispersed in deionized water, and then methacrylic acid, allyl hydroxamic acid ethanol solution, potassium persulfate and N,N'-methylenebisacrylamide are added and stirred for 15-30 minutes. Then the temperature is raised to 80°C, stirred for reaction for 2-4 hours, and naturally cooled to room temperature. After that, the mixture is transferred to an oven at 80-100°C and dried to constant weight, and finally crushed and passed through a 40-100 mesh sieve to obtain a bentonite-based adsorption material.

6. The method for recycling photoresist stripping waste liquid according to claim 5, characterized in that: The dosage ratio of unsaturated siloxane-modified magnetic bentonite, deionized water, methacrylic acid, allyl hydroxamic acid ethanol solution, potassium persulfate and N,N'-methylenebisacrylamide is 3.4 g: 60-100 mL: 3-5 g: 30-50 mL: 0.1 g: 0.01-0.02 g. The allyl hydroxamic acid ethanol solution is obtained by mixing allyl hydroxamic acid and 50-55°C anhydrous ethanol in a mass ratio of 1 g: 10 mL.

7. The method for recycling photoresist stripping waste liquid according to claim 5, characterized in that: The raw materials for preparing the unsaturated siloxane-modified magnetic bentonite include magnetic bentonite and unsaturated siloxane, and the mass ratio of the magnetic bentonite to the unsaturated siloxane is 100:5-10.

8. The method for recycling photoresist stripping waste liquid according to claim 7, wherein: The unsaturated siloxane is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltri(2-methoxyethoxy)silane and methacryloxypropyltrimethoxysilane.

9. The method for recycling photoresist stripping waste liquid according to claim 7, wherein: The magnetic bentonite is prepared by a coprecipitation method. The preparation raw materials include calcium bentonite, FeCl3·6H2O, FeSO4·7H2O and sodium hydroxide. The mass ratio of sodium bentonite, FeCl3·6H2O, FeSO4·7H2O and sodium hydroxide is 13.5-15.6:14.8:15.2:2.

19.

10. The method for recycling photoresist stripping waste liquid according to claim 6, characterized in that: The preparation method of allylhydroxamic acid is as follows: The system temperature is maintained below 10°C, methanol, hydroxylamine hydrochloride, sodium hydroxide, and methyl 2-(allyloxy)benzoate are added to a reaction kettle, stirred evenly, and then heated to 50-60°C and stirred for reaction for 4-6 hours. After the reaction is completed, the temperature is lowered to below 10°C, concentrated hydrochloric acid is added to adjust the pH to 5-6, and then the temperature is raised to 40-50°C. The mixture is filtered while hot and methanol is recovered by vacuum distillation to obtain allylhydroxamic acid. The molar ratio of hydroxylamine hydrochloride, sodium hydroxide, and methyl 2-(allyloxy)benzoate is 1.05-1.2:2.05:1.

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