Process for treating dyeing wastewater by membrane method

Abstract

The application discloses a process for treating dyeing wastewater by a membrane method, and comprises the following steps: pretreating the dyeing wastewater, including grating, adjusting pool, coagulation and sedimentation, and filtration, to obtain filtered wastewater; the filtered wastewater enters a security filter to be subjected to secondary filtration, to obtain secondary filtered wastewater; the secondary filtered wastewater enters an NXF membrane system, and the wastewater is divided into two streams, one of which is a concentrated solution which does not reach a set concentration, and the other of which is a permeate; the concentrated solution which does not reach the set concentration returns to a front end inlet to be subjected to filtration in the NXF membrane system again; when the concentration reaches the set concentration, the concentrated solution enters a concentration storage tank to be subjected to other treatment; and the permeate enters subsequent treatment. The application aims at solving the technical problem of poor treatment effect of dyeing wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and in particular relates to a membrane process for treating dyeing wastewater. Background Technology

[0002] Different dyeing factories have different processing techniques, which generally include pretreatment, dyeing, printing and finishing processes. The whole process will generate a large amount of wastewater. This wastewater contains a large amount of dyes, auxiliaries, acid and alkali substances, inorganic salts and organic pollutants. Its composition is complex and the water quality varies greatly. If this wastewater is discharged directly without proper treatment, it will have a serious impact on the environment and ecosystem.

[0003] Current dyeing wastewater treatment technologies include physical, chemical, and biological methods. Physical methods mainly transfer or concentrate pollutants between phases without fundamentally degrading them. Chemical methods alter the molecular structure of pollutants through chemical reactions, breaking them down into smaller molecules, which can easily cause secondary pollution. Biological methods utilize the metabolism of microorganisms to degrade pollutants; however, some pollutants cannot be degraded by biochemical methods and may even be toxic to microorganisms. Pretreatment processes are needed to remove or alter the structure of substances that are toxic to or cannot be degraded by microorganisms, making them more suitable for microbial treatment. This approach has disadvantages such as long processing times, complex control procedures, numerous limiting factors for treatment effectiveness, and high investment and operating costs.

[0004] As the composition of dyeing wastewater becomes increasingly complex, existing treatment technologies can no longer guarantee that the effluent meets discharge standards. Therefore, there is an urgent need to develop a low-cost, high-efficiency treatment process to reduce the multiple pressures of dyeing wastewater discharge on the environment and human health, and to achieve sustainable social development. Summary of the Invention

[0005] This invention provides a membrane process for treating dyeing wastewater, which solves the technical problem of poor treatment effect of current dyeing wastewater treatment.

[0006] In view of this, the present invention provides a membrane method for treating dyeing wastewater, comprising the following steps:

[0007] S1: Pre-treatment of dyeing wastewater includes bar filtration, equalization tank homogenization and equalization, coagulation sedimentation, and filtration to obtain pre-filtered wastewater;

[0008] S2: Allow the pre-filtered wastewater to enter the security filter for secondary filtration, resulting in secondary filtered wastewater.

[0009] S3: The wastewater after secondary filtration enters the NXF membrane system. The wastewater will be divided into two streams: one is a concentrated solution that has not reached the set concentration, and the other is the permeate. The concentrated solution that has not reached the set concentration will return to the front inlet and re-enter the NXF membrane system for filtration. When the concentration reaches the set concentration, it will enter the concentration storage tank for further treatment, and the permeate will enter the subsequent treatment.

[0010] In step S1, coagulation and sedimentation require the use of a coagulant.

[0011] Furthermore, a membrane-based process for treating dyeing wastewater includes the following steps:

[0012] S1: Pre-treatment of dyeing wastewater includes bar filtration, equalization tank homogenization and equalization, coagulation sedimentation, and filtration to obtain pre-filtered wastewater;

[0013] S2: The wastewater after the initial filtration is pumped into the security filter for secondary filtration to further remove some fine impurities, resulting in wastewater after secondary filtration.

[0014] S3: The wastewater after secondary filtration enters the NXF membrane system. The wastewater will be divided into two streams: one is a concentrated solution that has not reached the set concentration, and the other is the permeate. The concentrated solution that has not reached the set concentration will return to the front inlet and re-enter the NXF membrane system for filtration. When the concentration reaches the set concentration, it will enter the concentration storage tank for further treatment, and the permeate will enter the subsequent treatment.

[0015] In step S1, coagulation and sedimentation require the use of a coagulant;

[0016] The bar filtration in step S1 is to intercept larger suspended and floating objects in the dyeing wastewater, such as fibers, hair, and rags, to prevent these impurities from entering subsequent treatment equipment and causing blockage or damage.

[0017] In step S1, the equalization tank is used to equalize the flow rate and quality of wastewater entering the equalization tank. This process helps to stabilize the wastewater's quality and quantity, providing stable influent conditions for subsequent treatment. Additionally, a stirring device can be installed in the equalization tank to ensure uniform mixing of the wastewater.

[0018] The coagulation and sedimentation in step S1 involves adding coagulants and coagulant aids to the wastewater, causing colloidal particles and tiny suspended solids in the wastewater to aggregate into larger flocs, which are then removed through sedimentation. The coagulant aid is polyacrylamide; per 1m 3 The dosage of coagulant added to wastewater is 0.04-0.08 kg per 1 m³. 3 The amount of coagulant added to the wastewater is 0.02-0.04 kg.

[0019] The filtration in step S1 usually uses sand filtration, activated carbon filtration and other methods to further remove fine particles, organic matter and other impurities from the wastewater. Sand filtration can remove larger particles, while activated carbon filtration is mainly used to adsorb and remove dissolved organic matter, pigments and other substances from the wastewater, thereby reducing the color and COD of the wastewater.

[0020] After filtration by the security filter in step S2, the NXF membrane system is protected, and the filtration accuracy is 50 μm.

[0021] Optionally, in step S1, coagulation and sedimentation require the use of a coagulant, which is prepared by modifying the biochar / attapulgite composite material with 2-(3-aminopropyl)ethyltriethoxysilane and loading it with nano-zero-valent aluminum.

[0022] Optionally, the coagulant is prepared using the following method:

[0023] A1: Mix biochar and attapulgite, put them into sodium hydroxide solution, mix evenly, impregnate, filter, take out, dry, crush, grind, and then pyrolyze, wash and dry to obtain biochar / attapulgite composite material.

[0024] A2: Place the biochar / attapulgite composite material into an ethanol solution, then add 2-(3-aminopropyl)ethyltriethoxysilane, mix well, heat to a higher temperature, react, cool, wash, and dry to obtain a mixture;

[0025] A3: Under the protection of an inert gas, aluminum chloride is placed in an ethanol solution and mixed evenly to obtain an aluminum salt solution. The mixture is then placed in the aluminum salt solution and mixed evenly. Under the action of ultrasound, the mixture is rotated and oscillated. Sodium borohydride solution is then added, and the mixture is stirred continuously to react. The mixture is then filtered and separated to obtain a coagulant.

[0026] Furthermore, the coagulant is prepared using the following method:

[0027] A1: Mix biochar and attapulgite, place them in a 30% sodium hydroxide solution, mix evenly, soak for 4-6 hours, filter, remove, dry the solid, crush, grind, then pyrolyze, wash with water until neutral, and dry to obtain biochar / attapulgite composite material.

[0028] A2: Place the biochar / attapulgite composite material into a 30% ethanol solution, then add 2-(3-aminopropyl)ethyltriethoxysilane, mix well, heat to 60-90℃, react, cool, wash with anhydrous ethanol 3-5 times, then wash with water 3-5 times, and dry to obtain the mixture.

[0029] A3: Under nitrogen protection, aluminum chloride is placed in a 30% ethanol solution and mixed evenly to obtain an aluminum salt solution. The mixture is then placed in the aluminum salt solution and mixed evenly. Under the action of ultrasound at 80-120W, the mixture is rotated and oscillated. A 10% sodium borohydride solution is then added and stirred continuously for 1-3 hours. The mixture is then filtered and separated to obtain the coagulant.

[0030] In step A1, the amount of sodium hydroxide solution added per 1g of attapulgite is 10-14mL; in step A2, the amount of ethanol solution added per 1g of biochar / attapulgite composite material is 10-15mL; and in step A3, the amount of ethanol solution added per 1g of aluminum chloride is 8-12mL, and the amount of sodium borohydride solution added per 1g of aluminum chloride is 7-9mL.

[0031] Optionally, the weight ratio of attapulgite, biochar, 2-(3-aminopropyl)ethyltriethoxysilane, and aluminum chloride is 1:(0.2-1):(0.3-0.6):(0.2-0.5).

[0032] Optionally, the attapulgite soil undergoes the following pretreatment before use:

[0033] B1: Put the attapulgite clay into water, add the dispersant, mix evenly, and then ultrasonically disperse to obtain a mixture;

[0034] B2: Let the mixture stand, separate into layers, centrifuge to obtain the precipitate, wash, heat, and activate to obtain activated attapulgite.

[0035] B3: The activated attapulgite is placed in acid solution, mixed evenly, heated to a higher temperature, reacted, cooled, filtered, and the solids are washed to obtain pretreated attapulgite.

[0036] Furthermore, the attapulgite soil undergoes the following pretreatment before use:

[0037] B1: Put the attapulgite clay into water, add the dispersant, mix well, and then ultrasonically disperse it for 20-40 minutes at a power of 70-90W to obtain a mixture.

[0038] B2: Let the mixture stand, separate into layers, centrifuge to obtain the precipitate, wash with water 3-5 times, heat to 250-400℃, activate for 1-3 hours to obtain activated attapulgite.

[0039] B3: Place the activated attapulgite into the acid solution, mix evenly, heat to 70-90℃, react for 1-2 hours, cool, filter, wash the solid with water until neutral, and obtain the pretreated attapulgite.

[0040] In step B1, the amount of water added per 1g of attapulgite is 10-20mL, the weight ratio of attapulgite to dispersant is 1:(0.1-0.4), and the dispersant is sodium hexametaphosphate; in step B3, the acid solution is a 30% hydrochloric acid solution, and the amount of acid solution added per 1g of activated attapulgite is 8-15mL.

[0041] Optionally, the biochar is one or more of wheat straw, corn straw, and rice straw.

[0042] Optionally, the NXF membrane system includes a housing, an A-end cap, a B-end cap, a quick-release fastening kit, a membrane element, and permeate conduits located inside the A-end cap and the B-end cap, respectively. The housing is a hollow cylinder with openings at both ends. The A-end cap and the B-end cap are both hollow cylinders with openings at one end. The A-end cap is located at the bottom of the housing, and the B-end cap is located at the top of the housing. The opening ends of the two end caps are fixed to the housing by quick-release fastening kits. An inlet is fixed on the A-end cap, and a concentrate outlet is fixed on the B-end cap. The membrane element is wound into a cylinder coaxial with the housing and fixed inside the housing, forming a permeate cavity at the center along the height direction of the housing. Two permeate conduits are respectively arranged along the height direction of the housing, with the ends near the membrane element extending into and communicating with the permeate cavity. The end of the permeate conduit located inside the B-end cap extends out of the B-end cap and is fixed with a permeate outlet.

[0043] Optionally, the membrane element is an NXF membrane, and is a hollow fiber nanofiltration membrane.

[0044] Optionally, the subsequent treatment of the permeate in step S3 includes reuse or discharge.

[0045] Furthermore, the subsequent treatment of the permeate in step S3 includes reuse or discharge;

[0046] Among them, reuse or discharge means that if the water quality meets the requirements for production reuse water, it can be reused in the washing and rinsing stages of the dyeing process to realize the recycling of water resources; if the produced water does not meet the reuse standard, but meets the local sewage discharge standard, it can be discharged into the municipal sewage pipe network or natural water bodies; if there are higher discharge requirements, appropriate treatment processes can be matched according to the discharge requirements.

[0047] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

[0048] 1. This invention employs an NXF membrane system, wherein the NXF membrane is a hollow fiber nanofiltration membrane. During the dyeing and printing process, some dyes may not be completely applied to the fabric and are discharged with the wastewater. The NXF membrane can selectively retain dye molecules in the wastewater, allowing for their recycling and reuse, thus improving dye utilization and reducing production costs. Furthermore, it can separate and concentrate powders and salts in the wastewater, and the concentrated dye solution can be reused in the production process, achieving resource recovery and improving the company's economic benefits.

[0049] In addition, it can effectively retain organic matter such as additives and polyvalent ions in wastewater, especially substances with a molecular weight of about 200-1000 Da. It can significantly reduce the color and COD of wastewater. Wastewater treated by nanofiltration is clear and has improved biodegradability, creating good conditions for subsequent deep treatment or reuse. The treated water can meet the water quality requirements for reuse in production.

[0050] 2. This invention uses 2-(3-aminopropyl)ethyltriethoxysilane to modify a biochar / attapulgite composite material and loads it with nano-zero-valent aluminum to prepare a coagulant, which can further improve the treatment effect on wastewater. First, using biochar and attapulgite as a composite material not only realizes the recycling of biochar and reduces production costs, but also, both biochar and attapulgite have rich porous structures and high specific surface areas, and both have adsorption properties, which can form a synergistic adsorption effect to improve the treatment effect on wastewater. In addition, biochar mainly adsorbs organic matter and heavy metal ions, while attapulgite mainly adsorbs dye molecules and heavy metal ions. The two complement each other, reducing color and COD, and further improving the treatment effect on wastewater.

[0051] 2-(3-aminopropyl)ethyltriethoxysilane was used to modify biochar / attapulgite composites. By reacting the siloxane groups with the hydroxyl groups on the surface of biochar and attapulgite, stable chemical bonds were formed. This not only improved the mechanical strength of the composites but also introduced amino functional groups. These amino functional groups can form hydrogen bonds or coordination bonds with pollutants such as dye molecules and heavy metal ions in wastewater, which can further reduce color, adsorb pollutants, and improve the treatment effect of wastewater.

[0052] Finally, nano-zero-valent aluminum is loaded. Nano-zero-valent aluminum has extremely high reducing and reactivity, and exhibits excellent removal effects on a variety of pollutants. Its strong reducing ability enables it to effectively reduce heavy metal ions, organic pollutants, etc. in wastewater, and it can also convert pollutants into harmless or low-toxic substances through chemical reactions. Nano-zero-valent aluminum is prone to agglomeration. After being loaded, its dispersibility is improved, allowing it to play a better role and further improving the treatment effect on wastewater. Attached Figure Description

[0053] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0054] Figure 1 This is the overall process flow diagram of the present invention.

[0055] Figure 2 This is a schematic diagram of the overall structure of a single membrane in the NXF membrane system.

[0056] Figure 3 It is a cross-sectional view to represent the membrane component.

[0057] Explanation of reference numerals in the attached figures

[0058] 1. Outer shell; 2. A-end cap; 21. Inlet; 3. B-end cap; 31. Concentrate inlet; 4. Quick-release fastening kit; 5. Membrane; 51. Product water cavity; 6. Product water conduit; 61. Product water outlet. Detailed Implementation

[0059] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the present invention can be purchased on the market or prepared by existing methods.

[0060] Biochar is made from wheat straw.

[0061] Preparation Example

[0062] Preparation Example 1

[0063] A coagulant prepared by the following method:

[0064] A1: Mix 0.4 kg of biochar and 2 kg of attapulgite, put them into a 30% sodium hydroxide solution, mix evenly, soak for 5 hours, filter, take out, dry the solid, crush, grind, then pyrolyze, wash with water until neutral, and dry to obtain biochar / attapulgite composite material.

[0065] A2: The biochar / attapulgite composite material was placed in a 30% ethanol solution, and 0.6 kg of 2-(3-aminopropyl)ethyltriethoxysilane was added. The mixture was mixed evenly, heated to 75°C, reacted, cooled, washed 5 times with anhydrous ethanol, then washed 5 times with water, and dried to obtain the mixture.

[0066] A3: Under nitrogen protection, 0.4 kg of aluminum chloride was placed in a 30% ethanol solution and mixed evenly to obtain an aluminum salt solution. The mixture was then placed in the aluminum salt solution and mixed evenly. Under the action of 100 W of ultrasound, the mixture was rotated and oscillated. Then, a 10% sodium borohydride solution was added and stirred continuously for 2 hours. The mixture was then filtered and separated to obtain a coagulant.

[0067] In step A1, the amount of sodium hydroxide solution added per 1g of attapulgite is 12mL; in step A2, the amount of ethanol solution added per 1g of biochar / attapulgite composite material is 13mL; and in step A3, the amount of ethanol solution added per 1g of aluminum chloride is 10mL, and the amount of sodium borohydride solution added per 1g of aluminum chloride is 8mL.

[0068] Preparation Example 2

[0069] A coagulant, which differs from Preparation Example 1 in that the amount of biochar added is different; in Preparation Example 2, the amount of biochar added is 1.2 kg.

[0070] Preparation Example 3

[0071] A coagulant, which differs from Preparation Example 1 in that the amount of biochar added is different; in Preparation Example 3, the amount of biochar added is 2 kg.

[0072] Preparation Example 4

[0073] A coagulant, which differs from Preparation Example 2 in that the amount of 2-(3-aminopropyl)ethyltriethoxysilane added is different; in Preparation Example 4, the amount of 2-(3-aminopropyl)ethyltriethoxysilane added is 0.9 kg.

[0074] Preparation Example 5

[0075] A coagulant, which differs from Preparation Example 2 in that the amount of 2-(3-aminopropyl)ethyltriethoxysilane added is different; in Preparation Example 5, the amount of 2-(3-aminopropyl)ethyltriethoxysilane added is 1.2 kg.

[0076] Preparation Example 6

[0077] A coagulant, which differs from Preparation Example 4 in that the amount of aluminum chloride added is different; in Preparation Example 6, the amount of aluminum chloride added is 0.7 kg.

[0078] Preparation Example 7

[0079] A coagulant, which differs from Preparation Example 4 in that the amount of aluminum chloride added is different; in Preparation Example 7, the amount of aluminum chloride added is 1 kg.

[0080] Example

[0081] Reference Figure 1-3 The NXF membrane system in step S3 (detailed below) includes multiple individual membranes, with different numbers of individual membranes set according to different water volumes. These individual membranes can be arbitrarily connected in parallel or series as needed. Each individual membrane includes a housing 1, an A-end cap 2, a B-end cap 3, a quick-connect fastening kit 4, a membrane element 5, and a permeate conduit 6. The housing 1 is a hollow cylinder with openings at both ends. Both the A-end cap 2 and the B-end cap 3 are hollow cylinders with one open end. The A-end cap 2 is located at the bottom of the housing 1, and the B-end cap 3 is located at the top of the housing 1. The open ends of both are fixed to the housing 1 via the quick-connect fastening kit 4. An inlet 21 is fixed to the side of the A-end cap 2, and a concentrate inlet 31 is fixed to the side of the B-end cap 3. The membrane element 5 is arranged along the height direction of the outer shell 1. The membrane element 5 is wound into a cylinder coaxial with the outer shell 1 and fixed inside the outer shell 1, forming a cavity at its center, which is the permeate cavity 51. The permeate cavity 51 is arranged along the height direction of the outer shell 1. There are two permeate conduits 6, which are fixed at the center of end cap A 2 and end cap B 3 respectively, and are arranged along the height direction of the outer shell 1. The two ends of the two permeate conduits 6 near the membrane element 5 extend into the permeate cavity 51 and are connected to it. The end of the permeate conduit 6 located in end cap B 3, away from the membrane element 5, extends out of end cap B 3 and is fixed with a permeate outlet 61.

[0082] During use, the wastewater after secondary filtration enters through the inlet 21 of end cap A 2 and enters the membrane element 5. After filtration by the membrane element 5, it is divided into two parts. One part is the permeate, which enters the permeate cavity 51 and is discharged from the permeate outlet through the permeate conduit 6 for collection. The other part is the concentrated solution, which enters the end cap B 3 and is discharged from the concentrate outlet 31. End cap A 2 and end cap B 3 can be interchanged.

[0083] Example 1

[0084] Reference Figure 1 A membrane-based process for treating dyeing wastewater includes the following steps:

[0085] S1: 100m 3 The dyeing wastewater undergoes pretreatment, including bar filtration, which intercepts larger suspended solids and floating matter in the wastewater before it enters an equalization tank to regulate the water quality and quantity, ensuring relative stability and providing stable influent conditions for subsequent treatment. Then, 6 kg of the coagulant prepared in Example 1 and 3 kg of polyacrylamide are added to the wastewater passing through the equalization tank, causing colloidal particles and small suspended solids in the wastewater to coagulate into larger flocs, which are then removed through sedimentation. The wastewater is further filtered by sand filtration and activated carbon filtration to remove fine particles, organic matter, and other impurities, resulting in pre-filtered wastewater.

[0086] S2: The wastewater after preliminary filtration is pumped into the security filter for secondary filtration to obtain wastewater after secondary filtration.

[0087] S3: The wastewater after secondary filtration enters the NXF membrane system through the inlet 21 of end cap A 2. The wastewater enters the membrane element 5 and is separated into two streams after filtration. One stream is the concentrated solution that has not reached the set concentration, and the other stream is the permeate. The concentrated solution that has not reached the set concentration will be filtered from the membrane element 5 into end cap B 3 and discharged from the concentrate outlet 31. The above operation is repeated, and the wastewater enters the inlet 21 of end cap A 2 again and enters the membrane element 5 for filtration again. When the concentration reaches the set concentration, it is discharged from the concentrate outlet 31 of end cap B 3 and enters the concentration storage tank for further treatment. The permeate will enter the permeate cavity 51 and be discharged from the permeate outlet 61 for subsequent treatment.

[0088] Subsequent treatment includes reuse or discharge. If the water quality meets the requirements for reused water in production, it can be reused in the washing and rinsing processes of the dyeing process to achieve the recycling of water resources. If the produced water does not meet the reuse standards but meets the local sewage discharge standards, it can be discharged into the municipal sewage network or natural water bodies. If there are higher discharge requirements, appropriate treatment processes can be matched according to the discharge requirements.

[0089] Examples 2-7

[0090] A membrane process for treating dyeing wastewater differs from Example 1 in that the source of the coagulant is different; the coagulants in Examples 2-7 were prepared using the methods described in Examples 2-7.

[0091] Example 8

[0092] A membrane-based process for treating dyeing wastewater differs from Example 6 in that the attapulgite in the coagulant is pretreated using the following method before use:

[0093] B1: Put the attapulgite clay into water, add sodium hexametaphosphate, mix well, and ultrasonically disperse it for 30 minutes at 80W to obtain a mixture.

[0094] B2: Let the mixture stand, separate into layers, centrifuge to obtain the precipitate, wash with water 5 times, heat to 350℃, activate for 2 hours to obtain activated attapulgite.

[0095] B3: The activated attapulgite is placed in a 30% hydrochloric acid solution, mixed evenly, heated to 80°C, reacted for 1.5 hours, cooled, filtered, and the solid was washed with water until neutral to obtain pretreated attapulgite.

[0096] In step B1, the amount of water added per 1g of attapulgite is 15mL, the weight ratio of attapulgite to sodium hexametaphosphate is 1:0.25, and the amount of acid added per 1g of activated attapulgite is 12mL.

[0097] Comparative Example

[0098] Comparative Example 1

[0099] A membrane process for treating dyeing wastewater differs from Example 1 in that the coagulant is not modified with 2-(3-aminopropyl)ethyltriethoxysilane.

[0100] Comparative Example 2

[0101] A membrane process for treating dyeing wastewater differs from Example 1 in that the coagulant is not loaded with nano-zero-valent aluminum.

[0102] Comparative Example 3

[0103] A membrane process for treating dyeing wastewater differs from Example 1 in that the coagulant is polyferric sulfate.

[0104] Comparative Example 4

[0105] A membrane process for treating dyeing wastewater differs from Example 1 in that the wastewater after secondary filtration in step S3 is filtered through a polysulfone nanofiltration membrane.

[0106] Performance testing

[0107] The following performance tests were performed on the treated wastewater from Examples 1-8 and Comparative Examples 1-3:

[0108] COD: The COD in the treated wastewater was determined according to HJ-T399-2007 "Determination of Chemical Oxygen Demand in Water - Rapid Digestion Spectrophotometric Method". The test results are shown in Table 1.

[0109] Color: The color of the treated wastewater was measured in accordance with GB11903-1989 "Determination of Color in Water". The test results are shown in Table 1.

[0110] Ammonia nitrogen: The ammonia nitrogen in the treated wastewater was determined according to HJ535-2009 "Determination of ammonia nitrogen in water quality by Nessler's reagent spectrophotometric method". The test results are shown in Table 1.

[0111] Total nitrogen: The total nitrogen in the treated wastewater was determined according to HJ636-2012 "Determination of total nitrogen in water quality by alkaline potassium persulfate digestion ultraviolet spectrophotometry". The test results are shown in Table 2.

[0112] Suspended solids: The suspended solids in the treated wastewater were determined according to GB / T11901-1989 "Determination of suspended solids in water by gravimetric method". The test results are shown in Table 2.

[0113] The initial dyeing wastewater contained a COD of 2500 mg / L, a color of 500 times, an ammonia nitrogen content of 150 mg / L, a total nitrogen content of 200 mg / L, and a suspended solids content of 400 mg / L.

[0114] Table 1 Test Results

[0115]

[0116] Table 2 Detection Results

[0117]

[0118]

[0119] As can be seen from Tables 1 and 2, the membrane process for treating dyeing wastewater of this application significantly reduces the content of COD, color, ammonia nitrogen, total nitrogen, and suspended solids in the wastewater through the interaction between each step, thereby improving the treatment effect of the wastewater. Specifically, the removal rate of COD is 99.928-99.968%, the removal rate of color is 97.4-99.0%, the removal rate of ammonia nitrogen is 98.07-99.87%, the removal rate of total nitrogen is 97.1-98.95%, and the removal rate of suspended solids is 99.95-100%.

[0120] Combining Example 1 and Comparative Examples 1-3, it can be seen that the COD removal rate in Example 1 is 99.928%, the color removal rate is 97.4%, the ammonia nitrogen removal rate is 98.07%, the total nitrogen removal rate is 97.1%, and the suspended solids removal rate is 100%, which is better than that in Comparative Examples 1-3. This indicates that the coagulant modified with 2-(3-aminopropyl)ethyltriethoxysilane to modify the biochar / attapulgite composite material and loaded with nano-zero-valent aluminum is more suitable and can better improve the removal rate of COD, color, ammonia nitrogen, total nitrogen, and suspended solids in wastewater.

[0121] Combining Example 1 and Comparative Example 4, it can be seen that the COD removal rate in Example 1 is 99.928%, the color removal rate is 97.4%, the ammonia nitrogen removal rate is 98.07%, the total nitrogen removal rate is 97.1%, and the suspended solids removal rate is 100%, which is better than that in Comparative Example 4. This indicates that the use of NXF membrane is more suitable, as it can effectively retain organic matter such as additives and polyvalent ions in wastewater, significantly reduce the color and COD of wastewater, and improve the treatment effect of wastewater.

[0122] As can be seen from Examples 1-7, the COD removal rate in Example 6 was 99.964%, the color removal rate was 98.6%, the ammonia nitrogen removal rate was 98.73%, the total nitrogen removal rate was 98.7%, and the suspended solids removal rate was 100%, which was better than other examples. This indicates that the coagulant prepared in Example 6 was more suitable, and the amount of biochar, 2-(3-aminopropyl)ethyltriethoxysilane, and aluminum chloride added in Example 6 was more appropriate. If the amount added was too small, it would not have a good adsorption effect, and if the amount added was too large, it might cause agglomeration, resulting in uneven dispersion and affecting its function, thus affecting the treatment effect on wastewater.

[0123] Combining Examples 6 and 8, it can be seen that the COD removal rate in Example 8 is 99.968%, the color removal rate is 99.0%, the ammonia nitrogen removal rate is 99.87%, the total nitrogen removal rate is 98.95%, and the suspended solids removal rate is 100%, which is better than Example 6. This indicates that pretreatment of attapulgite before use is more suitable, as it removes impurities from the attapulgite, unblocks the pores, increases the specific surface area and pore volume, improves cation exchangeability, and enhances adsorption, thereby improving the adsorption of pollutants such as COD and organic matter in wastewater and thus improving the wastewater treatment effect.

[0124] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A membrane process for treating dyeing wastewater, characterized in that: Includes the following steps: S1: Pre-treatment of dyeing wastewater includes bar filtration, equalization tank homogenization and equalization, coagulation sedimentation, and filtration to obtain pre-filtered wastewater; S2: Allow the pre-filtered wastewater to enter the security filter for secondary filtration, resulting in secondary filtered wastewater. S3: The wastewater after secondary filtration enters the NXF membrane system. The wastewater will be divided into two streams: one is a concentrated solution that has not reached the set concentration, and the other is the permeate. The concentrated solution that has not reached the set concentration will return to the front inlet and re-enter the NXF membrane system for filtration. When the concentration reaches the set concentration, it will enter the concentration storage tank for further treatment, and the permeate will enter the subsequent treatment. The NXF membrane in the NXF membrane system is a hollow fiber nanofiltration membrane; In step S1, coagulation and sedimentation require the use of a coagulant; The coagulant is prepared by modifying biochar / attapulgite composite material with 2-(3-aminopropyl)ethyltriethoxysilane and loading it with nano-zero-valent aluminum. The coagulant is prepared using the following method: A1: Mix biochar and attapulgite, put them into sodium hydroxide solution, mix evenly, impregnate, filter, take out, dry, crush, grind, and then pyrolyze, wash and dry to obtain biochar / attapulgite composite material. A2: The biochar / attapulgite composite material was placed in an ethanol solution, and then 2-(3-aminopropyl)ethyltriethoxysilane was added. The mixture was mixed evenly, heated to a higher temperature, reacted, cooled, washed, and dried to obtain a mixture. A3: Under the protection of an inert gas, aluminum chloride is placed in an ethanol solution and mixed evenly to obtain an aluminum salt solution. The mixture is then placed in the aluminum salt solution and mixed evenly. Under the action of ultrasound, the mixture is rotated and oscillated. Sodium borohydride solution is then added, and the mixture is stirred continuously to react. The mixture is then filtered and separated to obtain a coagulant. The weight ratio of attapulgite, biochar, 2-(3-aminopropyl)ethyltriethoxysilane, and aluminum chloride is 1:(0.2-1):(0.3-0.6):(0.2-0.5).

2. The membrane treatment process for dyeing wastewater according to claim 1, characterized in that: The attapulgite soil undergoes the following pretreatment before use: B1: Put the attapulgite clay into water, add the dispersant, mix evenly, and then ultrasonically disperse to obtain a mixture; B2: Let the mixture stand, separate into layers, centrifuge to obtain the precipitate, wash, heat, and activate to obtain activated attapulgite. B3: The activated attapulgite is placed in acid solution, mixed evenly, heated to a higher temperature, reacted, cooled, filtered, and the solids are washed to obtain pretreated attapulgite.

3. The membrane treatment process for dyeing wastewater according to claim 1, characterized in that: The biochar is one or more of wheat straw, corn straw, and rice straw.

4. The membrane treatment process for dyeing wastewater according to claim 1, characterized in that: The subsequent treatment of the permeate in step S3 includes reuse or discharge.

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