Aqueous polyurethane adhesive waste liquid treatment method

Abstract

The application discloses a water-based polyurethane adhesive waste liquid treatment method, and raw materials used in the method contain solid alkali, solid acid, flocculants, layered double hydroxide, composite magnetic material and heavy metal capturing agent. The composite magnetic material is composed of magnetic nano catalyst and ferroferric oxide nanoparticles. The solid alkali is a mixture of sodium hydroxide and sodium carbonate. The solid acid is a mixture of oxalic acid and phosphoric acid. The application is implemented by five steps. The water-based polyurethane adhesive waste liquid treatment method significantly improves the COD removal rate through the synergistic effect of multiple steps including the acid-alkali oscillation demulsification stage, the flocculation catalytic degradation stage, the magnetic catalytic deep purification stage and the magnetic separation stage. The effluent turbidity is extremely low, and the separation time is greatly shortened by the magnetic separation technology. The treatment effect and efficiency are far superior to those of traditional methods, fully proving the innovativeness and technical advantages of the application.

Description

Technical Field

[0001] This invention relates to the field of post-treatment technology for waterborne polyurethane adhesives used in automotive interior and exterior trim, and particularly to a method for treating waste liquid from waterborne polyurethane adhesives. Background Technology

[0002] Currently, waterborne polyurethane adhesives are widely used in automotive interior and exterior trim due to their environmentally friendly properties. However, the wastewater generated during their production and use is complex, mainly originating from cleaning wastewater, residual adhesive from equipment, and expired products. It contains large amounts of emulsified polyurethane resin, organic solvents, unreacted isocyanate monomers, organic solvents (such as acetone), additives (leveling agents, defoamers), and small amounts of heavy metals. It has a high chemical oxygen demand (COD), strong stability, and is difficult to biodegrade. It also contains trace amounts of volatile organic compounds (VOCs). Although its toxicity is lower than that of solvent-based adhesives, direct discharge still pollutes water bodies. Common treatment methods include open storage of the dried adhesive, coagulation and sedimentation, and membrane separation.

[0003] Existing technologies often employ demulsification-flocculation methods, but these suffer from problems such as incomplete demulsification, slow floc settling speed, large footprint, and limited removal rate of dissolved organic matter. While magnetic separation technology can accelerate solid-liquid separation, how to construct an efficient and integrated treatment system for such highly stable waste liquids remains a technical challenge in this field.

[0004] Therefore, it is essential to provide a method for treating wastewater from waterborne polyurethane adhesives to address the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for treating waterborne polyurethane adhesive wastewater. This method significantly improves the COD removal rate, produces extremely low turbidity in the treated water, and greatly shortens the separation time.

[0006] The above-mentioned objectives of the present invention are achieved through the following technical measures:

[0007] A method for treating waterborne polyurethane adhesive waste liquid is provided, using raw materials containing solid alkali, solid acid, flocculant, layered bimetallic hydroxide, composite magnetic material, and heavy metal capture agent.

[0008] Preferably, the above-mentioned composite magnetic material is composed of magnetic nanocatalysts and iron oxide nanoparticles.

[0009] Preferably, the solid alkali is a mixture of sodium hydroxide and sodium carbonate.

[0010] Preferably, the solid acid is a mixture of oxalic acid and phosphoric acid.

[0011] The process is as follows:

[0012] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to perform alkali demulsification, and proceed to S2.

[0013] S2, Add solid acid to perform acid demulsification, then proceed to S3;

[0014] S3. Add flocculant and layered bimetallic hydroxide sequentially, then proceed to S4;

[0015] S4. Add composite magnetic materials and heavy metal trapping agents, then proceed to S5;

[0016] S5. A magnetic field is added to separate the flocculants from the water, resulting in treated water and magnetic sludge.

[0017] The method for treating waterborne polyurethane adhesive waste liquid of the present invention comprises the following steps:

[0018] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 10.5-11.5 to carry out alkali demulsification, and control the stirring speed at 250r / min-350r / min for 1min-5min, then proceed to S2.

[0019] S2. Add solid acid to the container to adjust the pH value to 3.0-4.5 to perform acid demulsification, and control the stirring speed at 250r / min-350r / min for 1min-5min, then proceed to S3.

[0020] S3. First, add flocculant to the container, control the stirring speed at 50 r / min to 80 r / min, and stir for 1 min to 5 min; then add layered bimetallic hydroxide, and control the stirring speed at 50 r / min to 80 r / min, and stir for 4 min to 7 min, then proceed to S4.

[0021] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed to 50 r / min to 80 r / min. Stir for 8 min to 15 min, and then proceed to S5.

[0022] S5. Move the container to the permanent magnet separator and let it stand for 1 min to 5 min to separate the treated water and magnetic sludge.

[0023] The method for treating waterborne polyurethane adhesive waste liquid of the present invention comprises the following steps:

[0024] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 11.0 to carry out alkali demulsification, and control the stirring speed at 300r / min. Stir for 3 minutes to carry out alkali demulsification, and then proceed to S2.

[0025] S2. Add solid acid to the container to adjust the pH value to 4.0 to perform acid demulsification, and control the stirring speed at 300 r / min. Stir for 3 minutes and then proceed to S3.

[0026] S3. First, add flocculant to the container, control the stirring speed at 60 r / min, and stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, and stir for 5 min, then proceed to S4.

[0027] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and proceed to S5.

[0028] S5. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge.

[0029] The amount of raw material added per liter of water-based polyurethane adhesive waste liquid is:

[0030] Solid alkali: 0.5g~1.5g;

[0031] Solid acid: 0.3g~1.0g;

[0032] Flocculant: 50mg~200mg;

[0033] Layered bimetallic hydroxide: 100mg~300mg;

[0034] Composite magnetic materials: 40mg~200mg;

[0035] Heavy metal scavenging agent: 10mg~50mg.

[0036] Furthermore, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0037] Solid alkali: 1.2g;

[0038] Solid acid: 0.6g;

[0039] Flocculant: 125mg;

[0040] Layered bimetallic hydroxide: 225 mg;

[0041] Composite magnetic material: 150mg;

[0042] Heavy metal scavenger: 36mg.

[0043] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:(1~1.5).

[0044] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is (2.5-3.5):1.

[0045] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:(1.8 to 2.5).

[0046] Preferably, the above-mentioned magnetic nanocatalyst is a Fe3O4@TiO2 magnetic nanocatalyst.

[0047] Preferably, the above-mentioned layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is (2-4):1.

[0048] Preferably, the flocculant is polyaluminum chloride.

[0049] Preferably, the heavy metal scavenging agent is a dithiocarbamate.

[0050] This invention discloses a method for treating waterborne polyurethane adhesive wastewater, using raw materials comprising a solid alkali, a solid acid, a flocculant, a layered bimetallic hydroxide, a composite magnetic material, and a heavy metal scavenging agent. The composite magnetic material is composed of magnetic nanocatalysts and iron(III) oxide nanoparticles. The solid alkali is a mixture of sodium hydroxide and sodium carbonate. The solid acid is a mixture of oxalic acid and phosphoric acid. The invention proceeds through the following steps: S1, adding waterborne polyurethane adhesive wastewater to a container, then adding a solid alkali for alkali demulsification, proceeding to S2; S2, adding a solid acid for acid demulsification, proceeding to S3; S3, sequentially adding a flocculant and a layered bimetallic hydroxide, proceeding to S4; S4, adding the composite magnetic material and the heavy metal scavenging agent, proceeding to S5; S5, applying a magnetic field to separate the flocculants from the water, obtaining treated water and magnetic sludge. This waterborne polyurethane adhesive wastewater treatment method significantly improves COD removal rate and produces extremely low effluent turbidity through the synergistic effect of multiple steps, including acid-base oscillation demulsification, flocculation catalytic degradation, magnetic catalytic deep purification, and magnetic separation. Furthermore, the magnetic separation technology greatly shortens the separation time, and the treatment effect and efficiency are far superior to traditional methods, fully demonstrating the innovation and technical advantages of this invention. Detailed Implementation

[0051] The technical solution of the present invention will be further described in conjunction with the following embodiments. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods. Unless otherwise specified, the raw materials and reagents used in the following embodiments can be purchased from conventional biochemical reagent stores or pharmaceutical companies. Polyaluminum chloride is polyaluminum chloride from Hubei Yuntu Chemical Co., Ltd. Magnesium aluminum hydrotalcite is Alfa Aesar's 042794 product from Thermo Fisher Scientific. Fe3O4@TiO2 magnetic nanocatalyst is Sigma-Aldrich's 718309 product, with a particle size of 20 nm and a Pd loading of 1.5 wt%. Iron tetroxide nanoparticles are Alfa Aesar's F3W011 product from Thermo Fisher Scientific, with a particle size of 20-30 nm. Sodium dithiocarbamate is Tokyo Chemical Industry Co., Ltd.'s D1041 product from TCL.

[0052] Example 1

[0053] A method for treating waterborne polyurethane adhesive waste liquid uses raw materials containing solid alkali, solid acid, flocculant, layered bimetallic hydroxide, composite magnetic material, and heavy metal capture agent.

[0054] It should be noted that the layered bimetallic hydroxide of this invention is magnesium aluminum hydrotalcite, in which the molar ratio of Mg²⁺ to Al³⁺ is (2-4):1, and the specific surface area is >50 m² / g. The physical basis for the high-efficiency adsorption performance of the layered bimetallic hydroxide lies in the fact that its nanosheet structure provides more active sites and a larger contact area, which is beneficial for adsorption and sweeping. In this positively charged system, it is more conducive to the adsorption of negatively charged organic pollutants and colloidal particles. If the Mg²⁺ in the magnesium aluminum hydrotalcite is higher than that in the magnesium aluminum hydrotalcite, the adsorption of negatively charged organic pollutants and colloidal particles is even more favorable. 2+ And Al 3+ A decrease in the molar ratio results in a relative increase in the content of aluminum ions, leading to a higher positive charge density. To balance the charge between the layers, more anions will be embedded, causing the interlayer spacing to decrease and affecting the adsorption of macromolecular organic matter. Conversely, an increase in the molar ratio will cause the interlayer spacing to increase, weakening the charge neutralization ability and making it difficult to form a regular layered structure.

[0055] The flocculant is polyaluminum chloride; the basicity (B value) of polyaluminum chloride is between 70% and 85%, and its effective ingredient content is ≥30%. This flocculant can effectively play the dual role of charge neutralization and adsorption bridging, making the formed flocs denser and the sedimentation performance better.

[0056] The heavy metal scavenger is a dithiocarbamate, which can form water-insoluble chelate precipitates with a broad spectrum of heavy metal ions. Dithiocarbamate can also form stable chelates with potential heavy metal ions released during demulsification (from catalyst residues, etc.).

[0057] The composite magnetic material is composed of magnetic nanocatalysts and iron(III) oxide nanoparticles, with a weight ratio of 1:(1-1.5). The magnetic nanocatalyst is Fe3O4@TiO2 magnetic nanocatalyst. The iron(III) oxide nanoparticles are ordinary magnetic nanoparticles with a particle size between 20-50 nm.

[0058] It should be noted that the magnetic nanocatalyst of the present invention can catalyze the degradation of small molecule organic matter under a weak magnetic field or its own action.

[0059] The solid alkali is a mixture of sodium hydroxide and sodium carbonate, wherein the weight ratio of sodium hydroxide to sodium carbonate in the solid alkali is (2.5–3.5):1. In the solid alkali, the carbonate ions provided by sodium carbonate can react with Ca... 2+ Mg 2+ Micro-precipitates form, which in turn aid in demulsification.

[0060] The solid acid is a mixture of oxalic acid and phosphoric acid, wherein the weight ratio of oxalic acid to phosphoric acid is 1:(1.8 to 2.5). In the solid acid, the buffering effect of phosphoric acid prevents excessive drop in pH, while oxalate ions can complex with certain metal ions, enhancing the demulsification effect.

[0061] The method for treating waterborne polyurethane adhesive waste liquid of the present invention comprises the following steps:

[0062] S1, Alkali Shaking Demulsification Stage: Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali for alkali demulsification, and proceed to S2;

[0063] S2, Acid Shaking Demulsification Stage: Solid acid is added for acid demulsification, proceeding to S3;

[0064] S3, flocculation-catalytic degradation stage: Flocculant and layered bimetallic hydroxide are added sequentially, and then proceed to S4;

[0065] S4, Magnetic-borne Catalysis-Heavy Metal Chelation Deep Purification Stage: Add composite magnetic materials and heavy metal scavengers, then proceed to S5;

[0066] S5. Magnetic separation stage: A magnetic field is added to separate the flocculants from the water, resulting in treated water and magnetic sludge.

[0067] Furthermore, the waterborne polyurethane adhesive waste liquid treatment method of the present invention is carried out by the following steps:

[0068] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 10.5-11.5 to carry out alkali demulsification, and control the stirring speed at 250r / min-350r / min for 1min-5min, then proceed to S2.

[0069] S2. Add solid acid to the container to adjust the pH value to 3.0-4.5 to perform acid demulsification, and control the stirring speed at 250r / min-350r / min for 1min-5min, then proceed to S3.

[0070] S3. First, add flocculant to the container, control the stirring speed at 50 r / min to 80 r / min, and stir for 1 min to 5 min; then add layered bimetallic hydroxide, and control the stirring speed at 50 r / min to 80 r / min, and stir for 4 min to 7 min, then proceed to S4.

[0071] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed to 50 r / min to 80 r / min. Stir for 8 min to 15 min, and then proceed to S5.

[0072] S5. Move the container to the permanent magnet separator and let it stand for 1 min to 5 min to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0073] In this invention, the amount of raw material added to each liter of water-based polyurethane adhesive waste liquid is:

[0074] Solid alkali: 0.5g~1.5g;

[0075] Solid acid: 0.3g~1.0g;

[0076] Flocculant: 50mg~200mg;

[0077] Layered bimetallic hydroxide: 100mg~300mg;

[0078] Composite magnetic materials: 40mg~200mg;

[0079] Heavy metal scavenging agent: 10mg~50mg.

[0080] This embodiment is a general process description. Specific parameters can be adjusted by referring to the preferred range or optimal value of embodiments 2-4 below.

[0081] This waterborne polyurethane adhesive wastewater treatment method significantly improves COD removal rate and produces extremely low effluent turbidity through the synergistic effect of multiple steps, including acid-base oscillation demulsification, flocculation catalytic degradation, magnetic catalytic deep purification, and magnetic separation. Furthermore, the magnetic separation technology greatly shortens the separation time, and the treatment effect and efficiency are far superior to traditional methods, fully demonstrating the innovation and technical advantages of this invention.

[0082] Example 2

[0083] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0084] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 10.5 to carry out alkali demulsification, and control the stirring speed at 350 r / min. Stir for 1 min, then proceed to S2.

[0085] S2. Add solid acid to the container to adjust the pH value to 4.5 to perform acid demulsification, and control the stirring speed at 350 r / min. Stir for 5 minutes and then proceed to S3.

[0086] S3. First, add flocculant to the container, control the stirring speed at 50 r / min, and stir for 5 min; then add layered bimetallic hydroxide, control the stirring speed at 50 r / min, and stir for 7 min, then proceed to S4.

[0087] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 50 r / min. Stir for 8 min and then proceed to S5.

[0088] S5. Move the container to the permanent magnet separator and let it stand for 1 minute to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0089] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0090] Solid alkali: 0.5g;

[0091] Solid acid: 0.3g;

[0092] Flocculant: 50mg;

[0093] Layered bimetallic hydroxide: 300 mg;

[0094] Composite magnetic material: 40mg;

[0095] Heavy metal scavenging agent: 10mg.

[0096] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 2.5:1.

[0097] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.5.

[0098] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.5.

[0099] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 2:1.

[0100] Example 3

[0101] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0102] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 11.5 to carry out alkali demulsification, and control the stirring speed at 250r / min. Stir for 5 minutes to carry out alkali demulsification, and then proceed to S2.

[0103] S2. Add solid acid to the container to perform acid demulsification and adjust the pH value to 3.0 to perform acid demulsification. Control the stirring speed at 250 r / min and stir for 1 min. Then proceed to S3.

[0104] S3. First, add flocculant to the container, control the stirring speed at 80 r / min, and stir for 5 min; then add layered bimetallic hydroxide, control the stirring speed at 80 r / min, and stir for 7 min, then proceed to S4.

[0105] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 80 r / min. Stir for 15 min and then proceed to S5.

[0106] S5. Move the container to the permanent magnet separator and let it stand for 5 minutes to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0107] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0108] Solid alkali: 1.5g;

[0109] Solid acid: 1.0g;

[0110] Flocculant: 200mg;

[0111] Layered bimetallic hydroxide: 100 mg;

[0112] Composite magnetic material: 200mg;

[0113] Heavy metal scavenging agent: 50mg.

[0114] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3.5:1.

[0115] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:1.8.

[0116] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.

[0117] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 4:1.

[0118] Example 4

[0119] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0120] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 11.0 to carry out alkali demulsification, and control the stirring speed at 300r / min. Stir for 3 minutes to carry out alkali demulsification, and then proceed to S2.

[0121] S2. Add solid acid to the container to adjust the pH value to 4.0 to perform acid demulsification, and control the stirring speed at 300 r / min. Stir for 3 minutes and then proceed to S3.

[0122] S3. First, add flocculant to the container, control the stirring speed at 60 r / min, and stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, and stir for 5 min, then proceed to S4.

[0123] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and proceed to S5.

[0124] S5. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0125] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0126] Solid alkali: 1.2g;

[0127] Solid acid: 0.6g;

[0128] Flocculant: 125mg;

[0129] Layered bimetallic hydroxide: 225 mg;

[0130] Composite magnetic material: 150mg;

[0131] Heavy metal scavenger: 36mg.

[0132] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3:1.

[0133] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.

[0134] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.2.

[0135] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 3:1.

[0136] Comparative Example 1

[0137] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0138] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 12.5, and control the stirring speed at 300r / min. Stir for 5 minutes to carry out alkali demulsification, and then proceed to S2.

[0139] S2. Add solid acid to the container to adjust the pH value to 2.8, and control the stirring speed at 300 r / min. Stir for 3 minutes, then proceed to S3.

[0140] S3. First, add flocculant to the container, control the stirring speed at 60 r / min, and stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, and stir for 5 min, then proceed to S4.

[0141] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and proceed to S5.

[0142] S5. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0143] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0144] Solid alkali: 2.8g;

[0145] Solid acid: 2.0g;

[0146] Flocculant: 350mg;

[0147] Layered bimetallic hydroxide: 80 mg;

[0148] Composite magnetic material: 30mg;

[0149] Heavy metal scavenging agent: 200mg.

[0150] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3.5:1.

[0151] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.

[0152] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.2.

[0153] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 3:1.

[0154] Comparative Example 2

[0155] A method for treating waterborne polyurethane adhesive waste liquid, which is otherwise the same as that in Example 4, except that:

[0156] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 1.5:1.

[0157] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:1.5.

[0158] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1.2:1.

[0159] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 1:1.

[0160] Comparative Example 3

[0161] A method for treating waterborne polyurethane adhesive waste liquid, which is otherwise the same as that in Example 4, except that:

[0162] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 1:1.5.

[0163] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1.5:1.

[0164] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:2.

[0165] Preferably, the above-mentioned layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 1:2.

[0166] Comparative Example 4

[0167] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0168] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid acid to adjust the pH value to 4.0 to carry out acid demulsification, and control the stirring speed at 300r / min. Stir for 3min and then proceed to S2.

[0169] S2. Then add solid alkali to the container to adjust the pH value to 11.0 to carry out alkali demulsification, and control the stirring speed at 300 r / min. Stir for 3 min and then proceed to S3.

[0170] S3. First, add flocculant to the container, control the stirring speed at 60 r / min, and stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, and stir for 5 min, then proceed to S4.

[0171] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and proceed to S5.

[0172] S5. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0173] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0174] Solid alkali: 1.6g;

[0175] Solid acid: 0.4g;

[0176] Flocculant: 125mg;

[0177] Layered bimetallic hydroxide: 225 mg;

[0178] Composite magnetic material: 150mg;

[0179] Heavy metal scavenger: 36mg.

[0180] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3:1.

[0181] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.

[0182] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.2.

[0183] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 3:1.

[0184] Comparative Example 5

[0185] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0186] S1. Add water-based polyurethane adhesive waste liquid to the container, first add flocculant, control the stirring speed at 60 r / min, stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, stir for 5 min, and then proceed to S2.

[0187] S2. Add solid alkali to the container to adjust the pH value to 11.0, and control the stirring speed at 300 r / min. Stir for 3 minutes to break the alkali emulsion, and proceed to S3.

[0188] S3. Add solid acid to the container to adjust the pH value to 4.0, and control the stirring speed at 300 r / min. Stir for 3 minutes and then proceed to S4.

[0189] S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and proceed to S5.

[0190] S5. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0191] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0192] Solid alkali: 1.3g;

[0193] Solid acid: 0.7g;

[0194] Flocculant: 125mg;

[0195] Layered bimetallic hydroxide: 225 mg;

[0196] Composite magnetic material: 150mg;

[0197] Heavy metal scavenger: 36mg.

[0198] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3:1.

[0199] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.

[0200] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.2.

[0201] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 3:1.

[0202] Comparative Example 6

[0203] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0204] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 11.0 to carry out alkali demulsification, and control the stirring speed at 300r / min. Stir for 3 minutes to carry out alkali demulsification, and then proceed to S2.

[0205] S2. Add solid acid to the container to adjust the pH value to 4.0 to perform acid demulsification, and control the stirring speed at 300 r / min. Stir for 3 minutes and then proceed to S3.

[0206] S3. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and then proceed to S4.

[0207] S4. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0208] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0209] Solid alkali: 1.2g;

[0210] Solid acid: 0.6g;

[0211] Composite magnetic material: 300mg;

[0212] Heavy metal scavenging agent: 100mg.

[0213] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3:1.

[0214] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.

[0215] In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:1.2.

[0216] Comparative Example 7

[0217] A method for treating wastewater from waterborne polyurethane adhesives comprises the following steps:

[0218] S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 11.0 to carry out alkali demulsification, and control the stirring speed at 300r / min. Stir for 3 minutes to carry out alkali demulsification, and then proceed to S2.

[0219] S2. Add solid acid to the container to adjust the pH value to 4.0 to perform acid demulsification, and control the stirring speed at 300 r / min. Stir for 3 minutes and then proceed to S3.

[0220] S3. First, add flocculant to the container, control the stirring speed at 60 r / min, and stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, and stir for 5 min, then proceed to S4.

[0221] S4. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge. The magnetic field strength of the permanent magnet separator is ≥0.3T.

[0222] In this invention, the amount of each raw material added to each liter of water-based polyurethane adhesive waste liquid is as follows:

[0223] Solid alkali: 1.2g;

[0224] Solid acid: 0.6g;

[0225] Flocculant: 300mg;

[0226] Layered bimetallic hydroxide: 500mg.

[0227] In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is 3:1.

[0228] In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:2.

[0229] The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is 3:1.

[0230] Example of effect

[0231] Under identical conditions, aqueous polyurethane adhesive waste liquid from the same source was treated using the methods described in Examples 2 to 4 and Comparative Examples 1 to 7. The final treated water was tested for CODcr (dichromate method) and turbidity, as shown in Table 1. The aqueous polyurethane adhesive waste liquid before treatment was a slightly grayish-white powder with a pH of 9.5. CODcr (dichromate method) testing was performed using a spectrophotometric COD rapid analyzer at a wavelength of 420 nm. Turbidity was measured using a turbidimeter.

[0232] Table 1. Effects of Waterborne Polyurethane Adhesive Waste Liquid Treatment Methods

[0233]

[0234] Wherein COD removal rate = (raw water COD - treated water COD) / raw water COD × 100%.

[0235] As can be seen from Table 1, the embodiments of the present invention achieve efficient processing through a multi-step collaborative mechanism, while the comparative example shows a significant decrease in effect due to deviation from the core process, which fully verifies the scientific nature and necessity of the process design, raw material ratio and parameter range of the present invention.

[0236] This invention is based on a synergistic mechanism of acid-base oscillation demulsification, flocculation adsorption, magnetic catalysis, and magnetic separation. First, solid alkali and solid acid are used to disrupt the stability of polyurethane emulsion by sudden pH changes, completely releasing the emulsified organic matter. Then, through the charge neutralization and adsorption bridging effect of polyaluminum chloride and the layered adsorption characteristics of magnesium aluminum hydrotalcite, the organic matter and colloids are aggregated into dense flocs. Finally, with the help of the catalytic degradation and magnetic responsiveness of composite magnetic materials, the flocs are rapidly separated under the action of permanent magnet magnetic separators. At the same time, heavy metals are captured by dithiocarbamate, ultimately achieving a COD removal rate of 92.0%-92.4% and a low turbidity of 2-5 NTU.

[0237] Comparative Examples 1-7 all showed a sharp drop in COD removal rate and a significant increase in turbidity due to disruption of this synergistic mechanism, such as pH exceeding the range leading to incomplete demulsification, reversed steps preventing the flocculant from acting on the demulsified organic matter, and the lack of flocculant and magnetic materials leading to adsorption or separation failure.

[0238] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for treating waterborne polyurethane adhesive waste liquid, characterized in that: The raw materials used include solid alkali, solid acid, flocculant, layered bimetallic hydroxide, composite magnetic material, and heavy metal capture agent; The composite magnetic material is composed of magnetic nanocatalysts and iron oxide nanoparticles. The solid alkali is a mixture of sodium hydroxide and sodium carbonate; The solid acid is a mixture of oxalic acid and phosphoric acid; The process is as follows: S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 10.5-11.5 to carry out alkali demulsification, and control the stirring speed at 250r / min-350r / min for 1min-5min, then proceed to S2. S2. Add solid acid to the container to adjust the pH value to 3.0-4.5 to perform acid demulsification, and control the stirring speed at 250r / min-350r / min for 1min-5min, then proceed to S3. S3. First, add flocculant to the container, control the stirring speed at 50 r / min to 80 r / min, and stir for 1 min to 5 min; then add layered bimetallic hydroxide, and control the stirring speed at 50 r / min to 80 r / min, and stir for 4 min to 7 min, then proceed to S4. S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed to 50 r / min to 80 r / min. Stir for 8 min to 15 min, and then proceed to S5. S5. Move the container to the permanent magnet separator and let it stand for 1 min to 5 min to separate the treated water and magnetic sludge. In the composite magnetic material, the weight ratio of magnetic nanocatalyst to iron oxide nanoparticles is 1:(1~1.5); In the solid alkali, the weight ratio of sodium hydroxide to sodium carbonate is (2.5–3.5):1; In the solid acid, the weight ratio of oxalic acid to phosphoric acid is 1:(1.8 to 2.5); The layered bimetallic hydroxide is magnesium aluminum hydrotalcite, in which Mg 2+ And Al 3+ The molar ratio is (2-4):

1.

2. The method for treating waterborne polyurethane adhesive waste liquid according to claim 1, characterized in that, The process is as follows: S1. Add water-based polyurethane adhesive waste liquid to the container, then add solid alkali to adjust the pH value to 11.0 to carry out alkali demulsification, and control the stirring speed at 300r / min. Stir for 3 minutes to carry out alkali demulsification, and then proceed to S2. S2. Add solid acid to the container to adjust the pH value to 4.0 to perform acid demulsification, and control the stirring speed at 300 r / min. Stir for 3 minutes and then proceed to S3. S3. First, add flocculant to the container, control the stirring speed at 60 r / min, and stir for 3 min; then add layered bimetallic hydroxide, control the stirring speed at 60 r / min, and stir for 5 min, then proceed to S4. S4. Add composite magnetic material and heavy metal scavenging agent to the container, and control the stirring speed at 70 r / min. Stir for 10 min and proceed to S5. S5. Move the container to the permanent magnet separator and let it stand for 3 minutes to separate the treated water and magnetic sludge.

3. The method for treating waterborne polyurethane adhesive waste liquid according to claim 2, characterized in that, The amount of raw material added per liter of water-based polyurethane adhesive waste liquid is: Solid alkali: 0.5g~1.5g; Solid acid: 0.3g~1.0g; Flocculant: 50mg~200mg; Layered bimetallic hydroxide: 100mg~300mg; Composite magnetic materials: 40mg~200mg; Heavy metal scavenging agent: 10mg~50mg.

4. The method for treating waterborne polyurethane adhesive waste liquid according to claim 3, characterized in that: The amount of raw material added per liter of water-based polyurethane adhesive waste liquid is: Solid alkali: 1.2g; Solid acid: 0.6g; Flocculant: 125mg; Layered bimetallic hydroxide: 225 mg; Composite magnetic material: 150mg; Heavy metal scavenger: 36mg.

5. The method for treating waterborne polyurethane adhesive waste liquid according to any one of claims 1 to 4, characterized in that: The magnetic nanocatalyst is a Fe3O4@TiO2 magnetic nanocatalyst.

6. The method for treating waterborne polyurethane adhesive waste liquid according to any one of claims 1 to 4, characterized in that: The flocculant is polyaluminum chloride.

7. The method for treating waterborne polyurethane adhesive waste liquid according to any one of claims 1 to 4, characterized in that: The heavy metal capturing agent is a dithiocarbamate.

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