A method for purifying wastewater from photoresist stripping solution

Abstract

This invention relates to the field of wastewater treatment technology, and more particularly to a purification method for photoresist stripping solution wastewater, comprising: pre-treating the photoresist stripping solution wastewater with acidification to obtain pre-treated wastewater; mixing the pre-treated wastewater with a composite coagulant, stirring and mixing, then settling and filtering to obtain primary purified wastewater; pumping the settled wastewater into a Fenton reactor, adjusting the pH of the settled wastewater, adding hydrogen peroxide and ferrous sulfate to carry out an oxidative degradation reaction, adjusting the pH of the wastewater after the reaction, and then settling and filtering to obtain secondary purified wastewater; first treating the secondary purified wastewater with denitrifying bacteria in an anoxic environment, then aerating and oxygenating it, and finally treating it with an activated carbon adsorption tower, and discharging it after water quality monitoring confirms compliance with standards. The entire process of this invention achieves highly efficient purification of photoresist stripping solution wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for purifying photoresist stripping solution wastewater. Background Technology

[0002] Photoresist stripping solution is a key chemical reagent used in semiconductor, flat panel display, and printed circuit board manufacturing processes to remove photoresist films. Its main components include N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), ethanolamine (MEA), and tetramethylammonium hydroxide (TMAH). During production, the wastewater generated after the stripping solution is used contains a large amount of residual photoresist organic polymers (mainly phenolic resin and polyhydroxystyrene) and the aforementioned organic solvents. It is characterized by high COD concentration (usually above 5000 mg / L), high ammonia nitrogen concentration, deep color, and alkaline pH. Furthermore, the wastewater has extremely poor biodegradability (BOD5 / COD is usually below 0.15), classifying it as typical recalcitrant industrial organic wastewater. Direct discharge without effective treatment will cause serious pollution to the aquatic environment.

[0003] Existing technologies for treating this type of wastewater mainly include standalone biological treatment, coagulation and sedimentation, advanced oxidation, and combinations of these methods. Standalone biological treatment is ineffective due to the extremely poor biodegradability of the wastewater; standalone coagulation and sedimentation has limited removal rates of dissolved organic matter, making it difficult to meet discharge standards; while advanced oxidation shows good degradation of organic matter, its high operating costs hinder large-scale application. Existing combined processes, although integrating the advantages of each unit to some extent, still require further improvement in their synergistic treatment effect on characteristic pollutants in photoresist wastewater and their overall process stability in practical engineering applications.

[0004] Patent application CN118811988A discloses a method for treating organic wastewater generated during the synthesis of photoresist resin. This method involves mixing carboxymethyl cellulose, polyacrylamide, ethylenediaminetetraacetic acid (EDTA), and demineralized water at a specific mass ratio to prepare a treatment reagent. This reagent is then mixed with the photoresist resin production wastewater at a volume ratio of 1:300–500. After settling, the mixture is filtered through a filter press for solid-liquid separation, removing organic matter and suspended solids from the wastewater and ensuring that the effluent COD and suspended solids concentrations meet discharge standards. This method features a simple process flow, low treatment cost, and is suitable for photoresist resin synthesis wastewater with a COD concentration of 500–3000 mg / L and relatively simple composition. However, there are significant differences in the pollutant composition between photoresist stripping solution wastewater and photoresist resin synthesis wastewater. The former contains a large amount of high-boiling-point organic solvents such as NMP, DMSO, and ethanolamine, as well as photoresist organic polymer residues. The COD concentration is usually much higher than 5000 mg / L, accompanied by high concentrations of ammonia nitrogen and a darker color, resulting in extremely poor biodegradability. The single coagulation, flocculation, and pressure filtration process used in the above-mentioned technical solutions is not suitable for this type of high-concentration, high-ammonia-nitrogen, and difficult-to-degrade photoresist stripping solution wastewater. It is difficult to achieve effective synergistic removal of complex pollutants in the wastewater and cannot meet the discharge standards for this type of wastewater. Summary of the Invention

[0005] In view of this, the present invention proposes a purification treatment method for photoresist stripping solution wastewater, in order to solve the problem that the existing technology lacks a systematic purification treatment technology route for photoresist stripping solution wastewater with high COD, high ammonia nitrogen and extremely poor biodegradability, and it is difficult to achieve the wastewater discharge standard.

[0006] The technical solution of this invention is implemented as follows: This invention provides a method for purifying wastewater from photoresist stripping solution, comprising the following steps: S1. The photoresist stripping solution wastewater is pretreated by acidification to obtain pretreated wastewater; S2. Mix the pretreated wastewater and composite coagulant, stir and mix, then settle and filter to obtain the purified wastewater. S3. Pump the settled wastewater into the Fenton reaction tank, adjust the pH of the settled wastewater to 3-4, add hydrogen peroxide and ferrous sulfate to carry out the oxidation degradation reaction, adjust the pH of the wastewater to 7-8 after the reaction, and obtain the secondary purified wastewater after sedimentation and filtration. S4. The wastewater after secondary purification is first treated by denitrifying bacteria in an anaerobic environment, then treated by aeration and oxygen supply, and finally treated by activated carbon adsorption tower. After the water quality meets the standards, it is discharged.

[0007] Specifically, in step S1, acidification treatment causes organic amines in the wastewater to protonate under acidic conditions, reducing their solubility. Simultaneously, the dissolved photoresist organic polymers undergo acid precipitation under acidic conditions, transforming from a dissolved state to suspended solids, facilitating subsequent coagulation and sedimentation removal. This achieves initial reduction of high-concentration organic pollutants in the wastewater and effectively reduces the treatment load on subsequent treatment units. In step S2, a two-stage stirring method—first rapid stirring, then slow stirring for flocculation—ensures the coagulant is fully dispersed in the wastewater and comes into contact with pollutants, promoting the flocculation of suspended and colloidal photoresist organic matter and suspended particles into flocs. In step S3, Fe in the system... 2+ Catalytic decomposition of H2O2 generates a large number of hydroxyl radicals. These hydroxyl radicals possess extremely strong oxidizing activity, capable of oxidizing and attacking residual recalcitrant organic solvents (such as NMP, DMSO, MEA, etc.) in wastewater, causing ring-opening and chain scission of large organic molecules, degrading them into intermediate products such as small-molecule organic acids. This significantly reduces the COD of the wastewater and simultaneously improves its biodegradability. After the reaction, the remaining Fe in the system... 2+ / Fe 3+ The wastewater flocculates and precipitates as hydroxides, and the resulting iron-based flocs simultaneously adsorb residual organic matter from the wastewater. In step S4, the secondary purified wastewater is introduced into the A / O biological treatment unit, where it is first treated by denitrifying bacteria in an anoxic environment. The denitrifying bacteria utilize the organic carbon source in the wastewater to convert nitrate nitrogen (NO3) into nitrogen. - Under anaerobic conditions, the nitrogen is reduced to N2 and released, achieving biological denitrification. It then enters the aerobic aeration section, where continuous aeration provides oxygen, and the microorganisms in the activated sludge further degrade residual organic matter in the wastewater. Simultaneously, nitrifying bacteria convert NH4+ into nitrogen. + Oxidized to NO3 - The process involves completing the nitrification reaction, thereby achieving the synergistic removal of organic matter and ammonia nitrogen from the wastewater. Finally, the wastewater is treated by an activated carbon adsorption tower, which utilizes the porous structure of activated carbon to adsorb and remove the remaining recalcitrant organic matter and color substances after biochemical treatment, ensuring that the effluent COD, ammonia nitrogen, and color stably meet the discharge standards.

[0008] Based on the above technical solutions, preferably, in step S1, the acidification pretreatment includes: adjusting the pH of the photoresist stripping solution wastewater to 3-4 using dilute sulfuric acid with a mass fraction of 15-20%, then allowing it to settle for a settling time, followed by filtration to obtain the pretreated wastewater.

[0009] Based on the above technical solutions, preferably, in step S2, the amount of composite coagulant added is 200~600mg / L, and the mixture is stirred and mixed at 100~150 r / min for 2~5 min, and then stirred and flocculated at 30~50 r / min for 15~20 min; the settling time is 1~2h.

[0010] Based on the above technical solutions, the preferred method for preparing the composite coagulant includes the following steps: A1. Polyaluminum chloride and zirconium oxychloride are dissolved in deionized water, the pH of the solution is adjusted to 2-3, and hydrothermally treated at 70-80℃ for 1-2 h. After the reaction is completed, the solution is concentrated under reduced pressure and dried to obtain zirconium-doped polyaluminum chloride. A2. Disperse zirconium-doped polyaluminum chloride in an aqueous ethanol solution, add γ-aminopropyltriethoxysilane, stir and react at 55-65℃ for 1-2 h, and after the reaction is completed, centrifuge, wash and dry to obtain aminated polyaluminum chloride; A3. Disperse aminated polyaluminum chloride in deionized water, adjust the pH of the solution to 8-9, add resorcinol diglycidyl ether, and stir the reaction at 55-65℃ for 2-3 h. After the reaction is completed, centrifuge, wash and dry to obtain the composite coagulant.

[0011] Specifically, in step A1, Zr is reacted via a hydrothermal reaction. 4+ Zr is incorporated into the PAC framework structure via coordination doping; 4+ The introduction of [a specific ingredient] increases the positive charge density on the surface of the coagulant particles and their complexation and adsorption capacity for anionic organic pollutants, thereby enhancing the coagulation activity of the matrix material. In step A2, aminopropyl groups are stably anchored on the particle surface in the form of Si-O covalent bonds. In step A3, the epoxy groups at both ends of resorcinol diglycidyl ether undergo ring-opening addition reactions with the amino groups on the particle surface, forming a cross-linked network containing resorcinol structural units on the surface of the coagulant particles. The benzene ring structure in this cross-linked network can undergo π-π stacking adsorption with aromatic organic pollutants such as phenolic resin and polyhydroxystyrene in photoresist wastewater. The aliphatic hydroxyl groups generated after the epoxy groups open can form hydrogen bonds with the polar functional groups on the photoresist organic polymer, further enhancing the adsorption affinity for the target pollutants. At the same time, the cross-linked network itself has a certain bridging flocculation effect, thereby achieving efficient removal of organic pollutants from photoresist wastewater.

[0012] Based on the above technical solutions, preferably, in step A1, the mass ratio of polyaluminum chloride to zirconium oxychloride is 8~10:1.

[0013] Based on the above technical solutions, preferably, in step A2, the amount of γ-aminopropyltriethoxysilane added is 8% to 12% of the mass of zirconium-doped polyaluminum chloride.

[0014] Based on the above technical solutions, preferably, in step A3, the amount of resorcinol diglycidyl ether added is 15% to 25% of the mass of the aminated polyaluminum chloride.

[0015] Based on the above technical solutions, preferably, in step S3, the mass fraction of hydrogen peroxide is 27% to 30%, the amount of hydrogen peroxide added is 2 to 8 g / L, the molar ratio of ferrous sulfate to hydrogen peroxide is 5:1 to 10:1, and the sedimentation time is 1 to 1.5 h.

[0016] Based on the above technical solutions, preferably, in step S4, the denitrifying bacteria treatment time is 4~6h, the aeration and oxygen supply treatment time is 6~10h, and the dissolved oxygen is maintained at 2~4mg / L during the aeration and oxygen supply process.

[0017] Based on the above technical solutions, preferably, in step S4, the empty bed contact time of the activated carbon adsorption tower is 15~20 min.

[0018] The purification treatment method for photoresist stripping solution wastewater of the present invention has the following advantages over the prior art: (1) This invention combines and links acidification pretreatment, coagulation sedimentation, Fenton oxidation, biological denitrification and aerobic degradation, and terminal activated carbon adsorption, so that different forms of pollutants in the photoresist stripping solution wastewater are removed in different units in a graded manner: first, the system stability is reduced and the easily precipitated / flocculated components are reduced, then the residual recalcitrant organic matter is oxidized and chain-broken to improve treatability, and finally stable deep purification is achieved through biochemical and adsorption, thereby improving the treatment adaptability and effluent stability of this type of high-concentration, complex wastewater.

[0019] (2) The present invention introduces a composite coagulant, which, based on the charge neutralization and adsorption bridging of the inorganic coagulation matrix, improves the surface activity of the particles and their ability to act on specific anions / polar components through zirconium doping, and introduces amino groups as surface reaction and adsorption sites through silane coupling, further constructing an organic network layer containing aromatic ring structure on the surface, so that it has better affinity adsorption and flocculation ability for aromatic polymer residues and colloidal organic matter in photoresist stripping wastewater; therefore, a single sedimentation filtration can more effectively remove suspended solids, colloidal organic matter and some dissolved organic matter, reducing the burden of subsequent oxidation and biochemical treatment.

[0020] (3) By setting up a Fenton oxidation unit after coagulation, organic matter that is still difficult to remove by conventional physicochemical separation after one purification can be non-selectively oxidized and degraded, causing some macromolecular or structurally stable organic pollutants to undergo chain breakage and transformation, thereby reducing the treatment difficulty of subsequent biochemical units and improving the overall process adaptability; after the reaction is completed, pH adjustment and sedimentation filtration are used to remove the precipitates and entrained substances formed during the reaction, reducing interference to the subsequent biological treatment system.

[0021] (4) The present invention adopts a biological treatment method that combines anoxic denitrification and aerobic aeration after secondary purification, so that nitrogen pollutants can be removed by denitrification in the anoxic section and further complete the biodegradation of organic matter and the conversion of ammonia nitrogen in the aerobic section, thereby improving the synergistic removal capacity of nitrogen pollutants and residual organic matter. This setting helps to improve the stability of effluent water quality and reduce the problem of being easily affected by influent fluctuations under single biological treatment conditions. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the initial water quality of the photoresist stripping solution wastewater to be treated in this embodiment and the comparative example is as follows: COD is 8500-9500 mg / L, ammonia nitrogen is 350-420 mg / L, color is 800-1000 times, and pH is 10-11.

[0024] Example 1 This embodiment provides a method for purifying photoresist stripping solution wastewater, specifically including the following steps: S1. Take 1000 L of photoresist stripping solution wastewater and place it in an acidification pretreatment tank. Under stirring conditions, slowly add 18% dilute sulfuric acid to adjust the pH of the wastewater to 4. During the adjustment process, continue stirring for 10 min to make the system uniform. Then let it stand and settle for 0.8 h, filter, and obtain the pretreated wastewater. S2. Transfer the pretreated wastewater to a coagulation reaction tank, add 400 mg / L of composite coagulant, and first stir rapidly at 120 r / min for 3 min to ensure that the coagulant is evenly dispersed and fully contacts the pollutants in the wastewater. Then reduce the speed to 40 r / min and stir slowly for 18 min to allow fine particles to gradually aggregate and form settleable flocs. Subsequently, transfer the wastewater to a sedimentation tank and let it settle for 1.5 h. Filter to obtain the first-stage purified wastewater. S3. Pump the purified wastewater into the Fenton reactor. Under stirring, add dilute sulfuric acid to adjust the pH of the wastewater to 4. Then add 5 g / L of 30% hydrogen peroxide. Add ferrous sulfate heptahydrate at a molar ratio of 8:1 (ferrous sulfate to hydrogen peroxide). After thorough mixing, carry out the oxidative degradation reaction at room temperature for 75 min. After the reaction is completed, slowly add 15% NaOH solution under stirring to adjust the pH of the wastewater to 7.5. This allows the remaining iron ions in the system to fully flocculate and precipitate as hydroxides. After settling for 1.2 h, filter to obtain the purified wastewater. S4. The wastewater after secondary purification is discharged at a rate of 3 m 3 The wastewater is pumped into the anoxic tank at a flow rate of / h. Under anoxic conditions (dissolved oxygen < 0.5 mg / L), it is treated by denitrifying bacteria for 5 h, using residual organic carbon in the wastewater as a carbon source to complete denitrification. Subsequently, the wastewater enters the aerobic aeration tank, where oxygen is continuously supplied by blower aeration for 8 h, and the dissolved oxygen is controlled to be maintained at 3 mg / L. The microorganisms in the activated sludge further degrade the residual organic matter and complete the nitrification reaction. After the aerobic treatment effluent is settled in the secondary sedimentation tank for 1.2 h, the supernatant enters the activated carbon adsorption tower for further treatment. The empty bed contact time of the activated carbon adsorption tower is controlled to be 18 min. The effluent is discharged after testing and meeting the standards.

[0025] The preparation method of the composite coagulant includes the following steps: A1. Dissolve 90g of polyaluminum chloride and 10g of zirconium oxychloride in 500 mL of deionized water, adjust the pH of the solution to 3 with dilute hydrochloric acid, place it in a hydrothermal reactor and hydrothermally treat it at 75℃ for 1.5 h; after the reaction is completed, take it out, concentrate it under reduced pressure to 1 / 3 of the original volume, dry it, grind it through a 200-mesh sieve to obtain zirconium-doped polyaluminum chloride. A2. 100g of zirconium-doped polyaluminum chloride was dispersed in 500 mL of ethanol-water solution with a volume ratio of 4:1 and ultrasonically dispersed for 10 min. 10g of γ-aminopropyltriethoxysilane was added and the mixture was mechanically stirred at 60℃ for 1.5 h. After the reaction was completed, the mixture was centrifuged (5000 r / min, 10 min), washed, and dried to obtain aminated polyaluminum chloride. A3. Disperse 100g of aminated polyaluminum chloride in 500 mL of deionized water, sonicate for 10 min, adjust the pH of the solution to 9, add 20g of resorcinol diglycidyl ether, stir and react at 60℃ for 2.5 h, after the reaction is completed, centrifuge (5000 r / min, 10 min), wash, dry, grind through a 200 mesh sieve to obtain the composite coagulant.

[0026] Example 2 This embodiment provides a method for purifying photoresist stripping solution wastewater, specifically including the following steps: S1. Take 1000 L of photoresist stripping solution wastewater and place it in an acidification pretreatment tank. Under stirring conditions, slowly add 15% dilute sulfuric acid to adjust the pH of the wastewater to 3. During the adjustment process, continue stirring for 10 min to make the system uniform. Then let it stand and settle for 0.5 h, filter, and obtain the pretreated wastewater. S2. Transfer the pretreated wastewater to the coagulation reaction tank, add 200 mg / L of composite coagulant, and first stir rapidly at 100 r / min for 5 min to ensure that the coagulant is evenly dispersed and fully contacts the pollutants in the wastewater. Then reduce the speed to 30 r / min and stir slowly for 15 min to allow fine particles to gradually aggregate and form settleable flocs. Subsequently, transfer the wastewater to a sedimentation tank and let it stand for 1 hour. Filter to obtain the first-stage purified wastewater. S3. Pump the purified wastewater into the Fenton reactor. Under stirring, add dilute sulfuric acid to adjust the pH of the wastewater to 3. Then add 2 g / L of 27% hydrogen peroxide. Add ferrous sulfate heptahydrate at a molar ratio of 10:1 to hydrogen peroxide. After stirring thoroughly, carry out the oxidative degradation reaction at room temperature for 90 min. After the reaction is completed, slowly add 10% NaOH solution under stirring to adjust the pH of the wastewater to 7. This allows the remaining iron ions in the system to fully flocculate and precipitate in the form of hydroxides. After settling for 1 h, filter to obtain the purified wastewater. S4. The wastewater after secondary purification is discharged at a rate of 2 m... 3 The wastewater is pumped into the anoxic tank at a flow rate of / h. Under anoxic conditions (dissolved oxygen < 0.5 mg / L), it is treated by denitrifying bacteria for 6 hours, using residual organic carbon in the wastewater as a carbon source to complete denitrification. Subsequently, the wastewater enters the aerobic aeration tank, where oxygen is continuously supplied by blower aeration for 10 hours, and the dissolved oxygen is controlled to be maintained at 2 mg / L. The microorganisms in the activated sludge further degrade the residual organic matter and complete the nitrification reaction. After the aerobic treatment effluent is settled in the secondary sedimentation tank for 1 hour, the supernatant enters the activated carbon adsorption tower for further treatment. The empty bed contact time of the activated carbon adsorption tower is controlled to be 15 minutes. The effluent is discharged after testing and meeting the standards.

[0027] The preparation method of the composite coagulant includes the following steps: A1. Dissolve 80g of polyaluminum chloride and 10g of zirconium oxychloride in 500 mL of deionized water, adjust the pH of the solution to 2 with dilute hydrochloric acid, place it in a hydrothermal reactor and hydrothermally treat it at 70℃ for 2 h; after the reaction is completed, take it out, concentrate it under reduced pressure to 1 / 3 of the original volume, dry it, grind it through a 200-mesh sieve to obtain zirconium-doped polyaluminum chloride. A2. 100g of zirconium-doped polyaluminum chloride was dispersed in 500 mL of ethanol-water solution with a volume ratio of 4:1 and ultrasonically dispersed for 10 min. 8g of γ-aminopropyltriethoxysilane was added and the mixture was mechanically stirred at 55℃ for 2 h. After the reaction was completed, the mixture was centrifuged (5000 r / min, 10 min), washed, and dried to obtain aminated polyaluminum chloride. A3. Disperse 100g of aminated polyaluminum chloride in 500 mL of deionized water, sonicate for 10 min, adjust the pH of the solution to 8, add 15g of resorcinol diglycidyl ether, stir and react at 55℃ for 3 h, after the reaction is completed, centrifuge (5000 r / min, 10 min), wash, dry, grind through a 200 mesh sieve to obtain the composite coagulant.

[0028] Example 3 This embodiment provides a method for purifying photoresist stripping solution wastewater, specifically including the following steps: S1. Take 1000 L of photoresist stripping solution wastewater and place it in an acidification pretreatment tank. Under stirring conditions, slowly add 20% dilute sulfuric acid to adjust the pH of the wastewater to 4. During the adjustment process, continue stirring for 10 min to make the system uniform. Then let it stand and settle for 1 h, filter, and obtain the pretreated wastewater. S2. Transfer the pretreated wastewater to the coagulation reaction tank, add 600 mg / L of composite coagulant, and first stir rapidly at 150 r / min for 2 min to ensure that the coagulant is evenly dispersed and fully contacts the pollutants in the wastewater. Then reduce the speed to 50 r / min and stir slowly for 15 min to allow fine particles to gradually aggregate and form settleable flocs. Subsequently, transfer the wastewater to a sedimentation tank and let it stand for 2 hours. Filter to obtain the first-stage purified wastewater. S3. Pump the purified wastewater into the Fenton reactor. Under stirring, add dilute sulfuric acid to adjust the pH of the wastewater to 4. Then add 8 g / L of 30% hydrogen peroxide. Add ferrous sulfate heptahydrate at a molar ratio of 5:1 to hydrogen peroxide. After stirring thoroughly, carry out the oxidative degradation reaction at room temperature for 60 min. After the reaction is completed, slowly add 15% NaOH solution under stirring to adjust the pH of the wastewater to 8. This allows the remaining iron ions in the system to fully flocculate and precipitate in the form of hydroxides. After settling for 1.5 h, filter to obtain the purified wastewater. S4. The wastewater after secondary purification is discharged at a rate of 4 m³. 3The wastewater is pumped into the anoxic tank at a flow rate of / h. Under anoxic conditions (dissolved oxygen < 0.5 mg / L), it is treated by denitrifying bacteria for 4 hours, using residual organic carbon in the wastewater as a carbon source to complete denitrification. Subsequently, the wastewater enters the aerobic aeration tank, where oxygen is continuously supplied by blower aeration for 6 hours, controlling the dissolved oxygen to be maintained at 4 mg / L. The microorganisms in the activated sludge further degrade the residual organic matter and complete the nitrification reaction. After the aerobic treatment effluent is settled in the secondary sedimentation tank for 1.5 hours, the supernatant enters the activated carbon adsorption tower for further treatment. The empty bed contact time of the activated carbon adsorption tower is controlled at 20 minutes. The effluent is discharged after testing and meeting the standards.

[0029] The preparation method of the composite coagulant includes the following steps: A1. Dissolve 100g of polyaluminum chloride and 10g of zirconium oxychloride in 500 mL of deionized water, adjust the pH of the solution to 3 with dilute hydrochloric acid, place it in a hydrothermal reactor and hydrothermally treat it at 80℃ for 1 h; after the reaction is completed, take it out, concentrate it under reduced pressure to 1 / 3 of the original volume, dry it, grind it through a 200-mesh sieve to obtain zirconium-doped polyaluminum chloride. A2. 100g of zirconium-doped polyaluminum chloride was dispersed in 500 mL of ethanol-water solution with a volume ratio of 4:1 and ultrasonically dispersed for 10 min. 12g of γ-aminopropyltriethoxysilane was added and the mixture was mechanically stirred at 65℃ for 1 h. After the reaction was completed, the mixture was centrifuged (5000 r / min, 10 min), washed, and dried to obtain aminated polyaluminum chloride. A3. Disperse 100g of aminated polyaluminum chloride in 500 mL of deionized water, sonicate for 10 min, adjust the pH of the solution to 9, add 25g of resorcinol diglycidyl ether, stir and react at 65℃ for 2 h, after the reaction is completed, centrifuge (5000 r / min, 10 min), wash, dry, grind through a 200 mesh sieve to obtain the composite coagulant.

[0030] Comparative Example 1 This comparative example discloses a purification treatment method for photoresist stripping solution wastewater. The treatment method is the same as in Example 1, except that zirconium-doped polyaluminum chloride is used as a composite coagulant.

[0031] Comparative Example 2 This comparative example discloses a purification treatment method for photoresist stripping solution wastewater. The treatment method is the same as in Example 1, except that aminated polyaluminum chloride is used as a composite coagulant.

[0032] Comparative Example 3 This comparative example discloses a purification method for photoresist stripping solution wastewater. The treatment method is the same as in Example 1, except that resorcinol diglycidyl ether is added in the form of physical mixing. That is, the preparation method of the composite coagulant includes: A1~A2 are the same as in Example 1; A3. Place 100 g of aminated polyaluminum chloride and 20 g of resorcinol diglycidyl ether in a mixer and mechanically stir dry for 30 min at room temperature to ensure uniform mixing, thus obtaining the composite coagulant.

[0033] Comparative Example 4 This comparative example discloses a purification method for photoresist stripping solution wastewater. The treatment method is the same as in Example 1, except that: Fenton oxidation treatment is performed first, followed by coagulation treatment. Specifically: S1 is the same as in Example 1 S2. The pretreated wastewater is pumped into the Fenton reactor. Dilute sulfuric acid is added under stirring to adjust the pH of the wastewater to 4. Then, 5 g / L of 30% hydrogen peroxide is added, followed by ferrous sulfate heptahydrate at a molar ratio of 8:1 to hydrogen peroxide. After thorough mixing, the oxidative degradation reaction is carried out at room temperature for 75 min. After the reaction is completed, 15% NaOH solution is slowly added under stirring to adjust the pH of the wastewater to 7.5, so that the remaining iron ions in the system can be fully flocculated and precipitated in the form of hydroxide. After settling for 1.2 h, the mixture is filtered to obtain the first-stage purified wastewater.

[0034] S3. Transfer the wastewater after primary purification to a coagulation reaction tank, add 400 mg / L of composite coagulant, and first stir rapidly at 120 r / min for 3 min to ensure that the coagulant is evenly dispersed and fully contacts the pollutants in the wastewater. Then reduce the speed to 40 r / min and stir slowly for 18 min to allow fine particles to gradually aggregate and form settleable flocs. Subsequently, transfer the wastewater to a sedimentation tank and let it settle for 1.5 h. After filtration, obtain the wastewater after secondary purification.

[0035] S4 is the same as in Example 1.

[0036] Comparative Example 5 This comparative example discloses a purification method for photoresist stripping solution wastewater. The treatment method is the same as in Example 1, except that: S1~S2 are the same as in Example 1; S3. The wastewater after secondary purification is discharged at a rate of 3 m 3 The wastewater is pumped into the anoxic tank at a flow rate of / h. Under anoxic conditions (dissolved oxygen < 0.5 mg / L), it is treated by denitrifying bacteria for 5 h, using residual organic carbon in the wastewater as a carbon source to complete denitrification. Subsequently, the wastewater enters the aerobic aeration tank, where oxygen is continuously supplied by blower aeration for 8 h, and the dissolved oxygen is controlled to be maintained at 3 mg / L. The microorganisms in the activated sludge further degrade the residual organic matter and complete the nitrification reaction. The aerobic treatment effluent is then settled in the secondary sedimentation tank for 1.2 h to obtain the secondary purified wastewater.

[0037] S4. Pump the secondary purified wastewater into the Fenton reactor. Under stirring, add dilute sulfuric acid to adjust the pH of the wastewater to 4. Then add 5 g / L of 30% hydrogen peroxide. Add ferrous sulfate heptahydrate at a molar ratio of 8:1 (ferrous sulfate to hydrogen peroxide). After thorough mixing, carry out the oxidative degradation reaction at room temperature for 75 min. After the reaction, slowly add 15% NaOH solution under stirring to adjust the pH of the wastewater to 7.5, so that the remaining iron ions in the system can be fully flocculated and precipitated in the form of hydroxide. After settling for 1.2 h, filter. The supernatant enters the activated carbon adsorption tower for deep treatment. The empty bed contact time of the activated carbon adsorption tower is controlled at 18 min. The effluent is discharged after passing the test.

[0038] Performance testing The final effluent (i.e., effluent treated by the activated carbon adsorption tower) obtained from the examples and comparative examples was used for water quality testing. Chemical oxygen demand (COD) was determined using the dichromate method, following standard HJ 828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method"; ammonia nitrogen was determined using the Nessler's reagent spectrophotometric method, following standard HJ 535-2009 "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometric Method"; and color was determined using the dilution factor method, following standard HJ 1182-2021 "Determination of Color in Water - Dilution Factor Method". Water sample collection and preservation were carried out in accordance with HJ 493-2009 "Technical Regulations for the Preservation and Management of Water Samples". The effluent discharge standard conformed to the Class I standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996). Based on the test results, the COD removal rate, ammonia nitrogen removal rate, and color removal rate were calculated respectively, and the removal rate was calculated according to the formula (1 - C_effluent / C_influent) × 100%. The test results are shown in Table 1.

[0039] Table 1

[0040] As shown in Table 1, the entire process of "acidification pretreatment—coagulation and flocculation—Fenton oxidation—biochemical treatment—activated carbon deep treatment" of the present invention, combined with the composite coagulant prepared by the present invention, can achieve efficient purification of photoresist stripping solution wastewater, and the treated wastewater meets the discharge standards. The removal rate of Comparative Example 1 is lower than that of Example 1, indicating that although simple zirconium doping modification improves the flocculation activity of PAC, the particle surface lacks amino functional groups and resorcinol diglycidyl ether organic crosslinking network, which lacks effective complexation and adsorption capacity for dissolved aromatic organic pollutants in wastewater, limiting the coagulation efficiency, and thus leading to a higher load on the subsequent Fenton and biochemical units, ultimately resulting in substandard effluent quality. Comparative Example 2, due to the lack of benzene ring hydrophobic framework and hydroxyl sites introduced by resorcinol diglycidyl ether crosslinking, has insufficient hydrophobic adsorption and multi-point synergistic binding capacity for characteristic aromatic pollutants of photoresist, and its removal effect is still weaker than that of Example 1. In Comparative Example 3, during the physical mixing process, resorcinol diglycidyl ether adsorbed onto the surface of the aminated PAC particles only through weak interactions such as van der Waals forces and hydrogen bonds. In actual use, due to wastewater dilution and hydraulic shear, resorcinol diglycidyl ether easily desorbed and detached from the particle surface, becoming ineffective and unable to form a stable organic functional layer on the particle surface, thus leading to reduced purification efficiency. In Comparative Example 4, the iron-based hydroxide colloids and precipitates generated by the Fenton reaction interfered with the residual colloidal organic matter in the wastewater, occupying the adsorption active sites of the composite coagulant and severely inhibiting the selective adsorption of organic pollutants by the coagulant. Simultaneously, the formation of iron sludge made the floc structure loose and difficult to settle, significantly reducing the actual pollutant removal efficiency. In Comparative Example 5, the wastewater still contained a high concentration of recalcitrant organic matter after primary purification. Without Fenton oxidation to enhance biodegradability, the wastewater directly entered the biochemical unit, resulting in extremely low utilization of the substrate by microorganisms and insufficient biodegradation efficiency. On the other hand, the biochemical effluent was "stained" by a large number of microbial metabolites (such as extracellular polysaccharides and humic substances). When Fenton oxidation was carried out on this basis, these biologically derived organic substances would consume a large amount of hydrogen peroxide and ferrous ions, making it impossible for Fenton reagent to be used to degrade the target pollutants. This resulted in low reagent utilization and poor deep treatment effect.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying wastewater from photoresist stripping solution, characterized in that, Includes the following steps: S1. The photoresist stripping solution wastewater is pretreated by acidification to obtain pretreated wastewater; S2. Mix the pretreated wastewater and composite coagulant, stir and mix, then settle and filter to obtain the purified wastewater. S3. Pump the settled wastewater into the Fenton reaction tank, adjust the pH of the settled wastewater to 3-4, add hydrogen peroxide and ferrous sulfate to carry out the oxidation degradation reaction, adjust the pH of the wastewater to 7-8 after the reaction, and obtain the secondary purified wastewater after sedimentation and filtration. S4. The wastewater after secondary purification is first treated by denitrifying bacteria in an anaerobic environment, then treated by aeration and oxygen supply, and finally treated by activated carbon adsorption tower. After the water quality meets the standards, it is discharged.

2. The purification treatment method for photoresist stripping solution wastewater as described in claim 1, characterized in that: In step S2, the amount of composite coagulant added is 200~600mg / L. First, stir and mix at 100~150 r / min for 2~5 min, then stir and flocculate at 30~50 r / min for 15~20 min; the settling time is 1~2h.

3. The purification treatment method for photoresist stripping solution wastewater as described in claim 2, characterized in that: The preparation method of the composite coagulant includes the following steps: A1. Polyaluminum chloride and zirconium oxychloride are dissolved in deionized water, the pH of the solution is adjusted to 2-3, and hydrothermally treated at 70-80℃ for 1-2 h. After the reaction is completed, the solution is concentrated under reduced pressure and dried to obtain zirconium-doped polyaluminum chloride. A2. Disperse zirconium-doped polyaluminum chloride in an aqueous ethanol solution, add γ-aminopropyltriethoxysilane, stir and react at 55-65℃ for 1-2 h, and after the reaction is completed, centrifuge, wash and dry to obtain aminated polyaluminum chloride; A3. Disperse aminated polyaluminum chloride in deionized water, adjust the pH of the solution to 8-9, add resorcinol diglycidyl ether, and stir the reaction at 55-65℃ for 2-3 h. After the reaction is completed, centrifuge, wash and dry to obtain the composite coagulant.

4. The purification treatment method for photoresist stripping solution wastewater as described in claim 3, characterized in that: In step A1, the mass ratio of polyaluminum chloride to zirconium oxychloride is 8~10:

1.

5. The purification treatment method for photoresist stripping solution wastewater as described in claim 3, characterized in that: In step A2, the amount of γ-aminopropyltriethoxysilane added is 8% to 12% of the mass of zirconium-doped polyaluminum chloride.

6. The purification treatment method for photoresist stripping solution wastewater as described in claim 3, characterized in that: In step A3, the amount of resorcinol diglycidyl ether added is 15% to 25% of the mass of the aminated polyaluminum chloride.

7. The purification treatment method for photoresist stripping solution wastewater as described in claim 1, characterized in that: In step S1, the acidification pretreatment includes: adjusting the pH of the photoresist stripping solution wastewater to 3-4 using dilute sulfuric acid with a mass fraction of 15-20%, then allowing it to settle for 0.5-1 hour, followed by filtration to obtain the pretreated wastewater.

8. The purification treatment method for photoresist stripping solution wastewater as described in claim 1, characterized in that: In step S3, the mass fraction of hydrogen peroxide is 27% to 30%, the amount of hydrogen peroxide added is 2 to 8 g / L, the molar ratio of ferrous sulfate to hydrogen peroxide is 5:1 to 10:1, and the sedimentation time is 1 to 1.5 h.

9. The purification treatment method for photoresist stripping solution wastewater as described in claim 1, characterized in that: In step S4, the denitrifying bacteria treatment time is 4~6 hours, the aeration and oxygen supply treatment time is 6~10 hours, and the dissolved oxygen is maintained at 2~4 mg / L during the aeration and oxygen supply process.

10. The purification treatment method for photoresist stripping solution wastewater as described in claim 1, characterized in that: In step S4, the empty bed contact time of the activated carbon adsorption tower is 15-20 minutes.

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