Process for treating dyeing wastewater by membrane method

Abstract

The invention discloses a process for treating dyeing wastewater by a membrane method, which comprises the following steps: pretreating the dyeing wastewater by a grating, an adjusting tank, coagulating sedimentation and filtration to obtain filtered wastewater; feeding the filtered wastewater into a security filter, and carrying out secondary filtration to obtain wastewater subjected to secondary filtration; the wastewater subjected to secondary filtration enters the NXF membrane system, the wastewater is divided into two streams, one stream is a concentrated solution not reaching the set concentration, the other stream is a permeate, the concentrated solution not reaching the set concentration returns to the front-end inlet and enters the NXF membrane system again to be filtered, and when the concentration reaches the set concentration, the concentrated solution enters the concentration storage tank to be subjected to other treatment; and performing subsequent treatment on the permeate. The technical problem that the dyeing wastewater treatment effect is poor is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to a process for treating dyeing wastewater by a membrane method. Background Technique

[0002] Different dyeing factories have different processing technologies, generally including pretreatment, dyeing, printing, finishing and other processes. A large amount of wastewater will be generated during the whole process. These wastewaters contain a large amount of dyes, auxiliaries, acid-base substances, inorganic salts and organic pollutants, etc. The composition is complex and the water quality changes greatly. If these wastewaters are directly discharged without proper treatment, it will have a serious impact on the environment and the ecosystem.

[0003] At present, the existing dyeing wastewater treatment technologies include physical treatment methods, chemical treatment methods, and biological treatment methods. The physical treatment method mainly transfers pollutants between phases or concentrates them, and does not degrade the pollutants essentially; the chemical treatment method changes the molecular structure of pollutants through chemical reactions and then degrades them into small molecule substances, which is easy to cause secondary pollution; the biological treatment method uses the metabolism of microorganisms to degrade pollutants, but for some pollutants, the biochemical method cannot degrade them, and they are also toxic to microorganisms. It is necessary to adopt a pretreatment process to remove or change the structure of substances that are toxic to microorganisms or cannot be degraded by microorganisms, so as to make them conducive to microbial treatment. This will have disadvantages such as long process, cumbersome control, many limiting factors for treatment effect, high investment and operation costs.

[0004] With the increasing complexity of the components of dyeing wastewater, the existing treatment technologies can no longer ensure that the effluent water quality meets the discharge standards. Therefore, it is urgent to propose a treatment process with low cost and good treatment effect, so as to reduce the multiple pressures of the discharge amount of dyeing wastewater on the environment and humans and realize the sustainable development of society. Summary of the Invention

[0005] The present invention provides a process for treating dyeing wastewater by a membrane method to solve the technical problem of poor treatment effect on dyeing wastewater.

[0006] In view of this, a process for treating dyeing wastewater by a membrane method provided by the present invention includes the following steps:

[0007] S1: Pretreat the dyeing wastewater, including grid filtration, equalization and homogenization in an adjustment tank, coagulation sedimentation, and filtration, to obtain the wastewater after preliminary filtration;

[0008] S2: Make the wastewater after preliminary filtration enter a security filter for secondary filtration to obtain the wastewater after secondary filtration;

[0009] S3: Feed the wastewater after secondary filtration into the NXF membrane system. The wastewater will be divided into two streams. One is the 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-end inlet and re-enter the NXF membrane system for filtration. When the concentration reaches the set concentration, it will enter the concentrated storage tank for further treatment, and the permeate will enter the subsequent treatment.

[0010] Among them, a coagulant is required for coagulation and precipitation in step S1.

[0011] Furthermore, a process for treating dyed wastewater by membrane method includes the following steps:

[0012] S1: Pretreat the dyed wastewater, including grid filtration, equalization and homogenization in the regulating tank, coagulation and precipitation, and filtration to obtain the wastewater after preliminary filtration.

[0013] S2: Lift the wastewater after preliminary filtration by a water pump and feed it into the security filter for secondary filtration to further remove some fine impurities and obtain the wastewater after secondary filtration.

[0014] S3: Feed the wastewater after secondary filtration into the NXF membrane system. The wastewater will be divided into two streams. One is the 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-end inlet and re-enter the NXF membrane system for filtration. When the concentration reaches the set concentration, it will enter the concentrated storage tank for further treatment, and the permeate will enter the subsequent treatment.

[0015] Among them, a coagulant is required for coagulation and precipitation in step S1;

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

[0017] The equalization and homogenization in the regulating tank in step S1 means that the wastewater enters the regulating tank for water quality and quantity adjustment to keep the water quality and quantity of the wastewater relatively stable, providing stable inlet conditions for subsequent treatment. At the same time, a stirring device can be set in the regulating tank to mix the wastewater evenly.

[0018] The coagulation and precipitation in step S1 is to add a coagulant and a flocculant aid to the wastewater to coagulate the colloidal particles and fine suspended solids in the wastewater into larger flocs, and then remove them through precipitation. The flocculant aid is polyacrylamide; for every 1 m 3 The dosage of the coagulant in the wastewater is 0.04 - 0.08 kg, and for every 1 m 3 The dosage of the flocculant aid in the wastewater is 0.02 - 0.04 kg.

[0019] The filtration in step S1 usually adopts methods such as sand filtration and activated carbon filtration to further remove impurities such as fine particles and organic matter in the wastewater. Sand filtration can remove larger particles, while activated carbon filtration is mainly used to adsorb and remove dissolved organic matter, pigments, etc. in the wastewater, reducing the chromaticity and COD of the wastewater;

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

[0021] Optionally, a coagulant is required for coagulation precipitation in step S1, and the coagulant is prepared by modifying a biochar / palygorskite composite material with 2-(3-aminopropyl)ethyltriethoxysilane and loading nano zero-valent aluminum.

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

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

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

[0025] A3: Under the protection of an inert gas, put aluminum chloride into an ethanol solution, mix evenly to obtain an aluminum salt solution, put the mixture into the aluminum salt solution, mix evenly, under the action of ultrasound, rotate and oscillate, then add a sodium borohydride solution, continuously stir, react, filter, and separate to prepare the coagulant.

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

[0027] A1: Mix biochar and palygorskite, put them into a sodium hydroxide solution with a mass fraction of 30%, mix evenly, impregnate for 4-6h, filter, take out, dry the solid, crush, grind, and then pyrolyze, wash with water until neutral, and dry to obtain a biochar / palygorskite composite material;

[0028] A2: Put the biochar / palygorskite composite material into an ethanol solution with a mass fraction of 30%, then add 2-(3-aminopropyl)ethyltriethoxysilane, mix evenly, heat up to 60-90°C, react, cool, first wash 3-5 times with absolute ethanol, then wash 3-5 times with water, and dry to obtain a mixture;

[0029] A3: Under the protection of nitrogen, put aluminum chloride into an ethanol solution with a mass fraction of 30%, mix evenly to obtain an aluminum salt solution, put the mixture into the aluminum salt solution, mix evenly, under the action of ultrasonic waves with a power of 80 - 120w, rotate and oscillate, then add a sodium borohydride solution with a mass fraction of 10%, continuously stir, react for 1 - 3h, filter by suction, separate, and prepare a coagulant;

[0030] Among them, the addition amount of sodium hydroxide solution for every 1g of attapulgite in step A1 is 10 - 14mL, the addition amount of ethanol solution for every 1g of biochar / attapulgite composite in step A2 is 10 - 15mL, in step A3, the addition amount of ethanol solution for every 1g of aluminum chloride is 8 - 12mL, and the addition amount of sodium borohydride solution for every 1g of aluminum chloride is 7 - 9mL.

[0031] Optionally, the weight ratio of the 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 is pretreated as follows before use:

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

[0034] B2: Let the mixed solution stand, stratify, centrifuge to obtain a precipitate, wash, heat, and activate to obtain activated attapulgite;

[0035] B3: Put the activated attapulgite into an acid solution, mix evenly, heat up, react, cool, filter, and wash the solid to obtain pretreated attapulgite.

[0036] Furthermore, the attapulgite is pretreated as follows before use:

[0037] B1: Put the attapulgite into water, add a dispersant, mix evenly, and perform ultrasonic dispersion for 20 - 40min at a power of 70 - 90w to obtain a mixed solution;

[0038] B2: Let the mixed solution stand, stratify, centrifuge to obtain a precipitate, wash with water 3 - 5 times, heat to 250 - 400°C, and activate for 1 - 3h to obtain activated attapulgite;

[0039] B3: Put the activated attapulgite into an acid solution, mix evenly, heat up to 70 - 90°C, react for 1 - 2h, cool, filter, and wash the solid with water until neutral to obtain pretreated attapulgite;

[0040] Among them, in step B1, the water addition amount per 1 g of attapulgite is 10 - 20 mL, 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 hydrochloric acid solution with a mass fraction of 30%, and the acid solution addition amount per 1 g of activated attapulgite is 8 - 15 mL.

[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 cover, a B end cover, a quick - installation fastening kit, a membrane element, and water production conduits located in the A end cover and the B end cover respectively. The housing is arranged in a cylindrical shape with a hollow interior and open ends. The A end cover and the B end cover are both arranged in a cylindrical shape with a hollow interior and one open end. The A end cover is arranged at the bottom of the housing, and the B end cover is arranged at the top of the housing. Their open ends are fixed to the housing through the quick - installation fastening kit respectively. An inlet is fixedly provided on the A end cover, and a concentrated water outlet is fixedly provided on the B end cover. The membrane element is wound into a cylinder coaxial with the housing and is fixedly arranged inside the housing, and a water production cavity is formed at the central position along the height direction of the housing. The two water production conduits are arranged along the height direction of the housing, and the ends close to the two ends of the membrane element extend into the water production cavity and are connected to it. The end of the water production conduit located in the B end cover away from the membrane element extends out of the B end cover and is fixedly provided with a water production 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] Further, 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 of production recycled water, it can be reused in the washing, rinsing and other links 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 body; if there are higher discharge requirements, appropriate treatment processes can be configured according to the discharge requirements.

[0047] From the above technical solutions, it can be seen that the embodiments of the present invention have the following advantages:

[0048] 1. The present invention adopts the NXF membrane system, where the NXF membrane is a hollow fiber nanofiltration membrane. During the printing and dyeing production process, some dyes may not be fully dyed onto the fabric and are discharged with the wastewater. The NXF membrane can selectively intercept the dye molecules in the wastewater, recycle and reuse them, improve the utilization rate of dyes, and reduce production costs. It can also separate and concentrate the powder and salts in the wastewater. The concentrated dye solution can be recycled and used in the production process to achieve the recycling of resources and improve the economic benefits of the enterprise.

[0049] In addition, it can effectively intercept organic substances such as auxiliaries and multivalent ions in the wastewater, especially has a good interception effect on substances with a molecular weight of about 200 - 1000 Da. It can significantly reduce the chromaticity and COD of the wastewater. After nanofiltration treatment, the wastewater is clear, and its biodegradability is improved, creating good conditions for subsequent advanced treatment or reuse. The treated water can meet the water quality requirements for production recycled water.

[0050] 2. The present invention uses 2-(3-aminopropyl)ethyltriethoxysilane to modify the biochar / palygorskite composite material and load nano-zero-valent aluminum to obtain a coagulant, which can further improve the treatment effect on wastewater. First, using biochar and palygorskite as the composite material not only realizes the recycling of biochar and reduces production costs, but also both biochar and palygorskite 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 of wastewater. In addition, biochar mainly adsorbs organic substances and heavy metal ions, and palygorskite mainly adsorbs dye molecules and heavy metal ions. The two complement each other to reduce chromaticity and COD and further improve the treatment effect on wastewater.

[0051] Using 2-(3-aminopropyl)ethyltriethoxysilane to modify the biochar / palygorskite composite material, through the reaction of siloxane groups with the hydroxyl groups on the surfaces of biochar and palygorskite, stable chemical bonds are formed, which can not only improve the mechanical strength of the composite material, but also introduce amino functional groups. The amino functional groups can form hydrogen bonds or coordination bonds with pollutants such as dye molecules and heavy metal ions in the wastewater, which can further reduce chromaticity, adsorb pollutants, and improve the treatment effect on wastewater.

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

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

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

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

[0056] Figure 3 is to represent the cross-sectional view of the membrane element.

[0057] Description of the reference numerals in the drawings

[0058] 1. Outer shell; 2. A end cover; 21. Water inlet; 3. B end cover; 31. Concentrate water outlet; 4. Quick-install fastening kit; 5. Membrane element; 51. Water production cavity; 6. Water production conduit; 61. Water production outlet. Specific embodiments

[0059] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than 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 making creative efforts shall fall within the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0060] The biochar is wheat straw.

[0061] Preparation examples

[0062] Preparation example 1

[0063] A coagulant is prepared by the following method:

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

[0065] A2: Put the biochar / attapulgite clay composite material into an ethanol solution with a mass fraction of 30%, then add 0.6 kg of 2-(3-aminopropyl)ethyltriethoxysilane, mix evenly, heat up to 75 °C, react, cool, wash 5 times with anhydrous ethanol first, then wash 5 times with water, and dry to obtain a mixture;

[0066] A3: Under the protection of nitrogen, 0.4 kg of aluminum chloride was put into an ethanol solution with a mass fraction of 30%, and the mixture was stirred evenly to obtain an aluminum salt solution. The mixture was then put into the aluminum salt solution and stirred evenly. Under the action of ultrasonic waves with a power of 100 w, it was rotated and oscillated, and then a sodium borohydride solution with a mass fraction of 10% was added. After continuous stirring for 2 h, filtration was carried out to separate and obtain a coagulant;

[0067] Among them, the addition amount of sodium hydroxide solution for every 1 g of attapulgite in step A1 was 12 mL, the addition amount of ethanol solution for every 1 g of biochar / attapulgite composite material in step A2 was 13 mL. In step A3, the addition amount of ethanol solution for every 1 g of aluminum chloride was 10 mL, and the addition amount of sodium borohydride solution for every 1 g of aluminum chloride was 8 mL.

[0068] Preparation Example 2

[0069] A coagulant, the difference from Preparation Example 1 is that the addition amount of biochar is different. The addition amount of biochar in Preparation Example 2 is 1.2 kg.

[0070] Preparation Example 3

[0071] A coagulant, the difference from Preparation Example 1 is that the addition amount of biochar is different. The addition amount of biochar in Preparation Example 3 is 2 kg.

[0072] Preparation Example 4

[0073] A coagulant, the difference from Preparation Example 2 is that the addition amount of 2-(3-aminopropyl)ethyltriethoxysilane is different. The addition amount of 2-(3-aminopropyl)ethyltriethoxysilane in Preparation Example 4 is 0.9 kg.

[0074] Preparation Example 5

[0075] A coagulant, the difference from Preparation Example 2 is that the addition amount of 2-(3-aminopropyl)ethyltriethoxysilane is different. The addition amount of 2-(3-aminopropyl)ethyltriethoxysilane in Preparation Example 5 is 1.2 kg.

[0076] Preparation Example 6

[0077] A coagulant, the difference from Preparation Example 4 is that the addition amount of aluminum chloride is different. The addition amount of aluminum chloride in Preparation Example 6 is 0.7 kg.

[0078] Preparation Example 7

[0079] A coagulant, the difference from Preparation Example 4 is that the addition amount of aluminum chloride is different. The addition amount of aluminum chloride in Preparation Example 7 is 1 kg.

[0080] Examples

[0081] Reference Figures 1-3 , the NXF membrane system in step S3 (detailed below) includes multiple single membranes, and different numbers of single membranes are set according to different water volumes, and multiple single membranes can be arbitrarily connected in parallel or in series as needed. Each single membrane includes a housing 1, an A end cover 2, a B end cover 3, a quick-install fastening kit 4, a membrane element 5, and a water production conduit 6. The housing 1 is set in a cylindrical shape with a hollow interior and open ends at both ends. Both the A end cover 2 and the B end cover 3 are set in a cylindrical shape with a hollow interior and an open end at one end. The A end cover 2 is arranged at the bottom end of the housing 1, and the B end cover 3 is arranged at the top end of the housing 1. And their open ends are respectively fixed to the housing 1 through the quick-install fastening kit 4. An inlet 21 is fixedly arranged on the side of the A end cover 2, and a concentrated water outlet 31 is fixedly arranged on the side of the B end cover 3. The membrane element 5 is arranged along the height direction of the housing 1. The membrane element 5 is wound into a cylinder coaxial with the housing 1 and is fixedly arranged inside the housing 1, and a cavity is formed at the central position, which is the water production cavity 51. The water production cavity 51 is arranged along the height direction of the housing 1. The number of the water production conduits 6 is two, which are respectively fixedly arranged at the central positions of the A end cover 2 and the B end cover 3 and are arranged along the height direction of the housing 1. The two ends of the water production conduits 6 close to the membrane element 5 extend into the water production cavity 51 and are communicated with it. The end of the water production conduit 6 located in the B end cover 3 far from the membrane element 5 extends out of the B end cover 3 and is fixedly provided with a water production port 61.

[0082] During use, the secondary-filtered wastewater will enter from the inlet 21 of the A end cover 2. The wastewater will enter the membrane element 5. After being filtered by the membrane element 5, it is divided into two parts. One part is the permeate, which enters the water production cavity 51 and is discharged from the water production port through the water production conduit 6 for collection. The other part is the concentrated solution, which enters the B end cover 3 and is discharged from the concentrated water outlet 31. Among them, the A end cover 2 and the B end cover 3 can be interchanged.

[0083] Example 1

[0084] Reference Figure 1 , a process for treating dyeing wastewater by membrane method, includes the following steps:

[0085] S1: Pretreat 100 m 3 of dyeing wastewater, including grid filtration. Larger suspended solids and floating substances in the dyeing wastewater are intercepted by the grid, and then enter the regulating tank for water quality and water volume regulation to keep the water quality and water volume of the wastewater relatively stable and provide stable inlet conditions for subsequent treatment; then add 6 kg of the coagulant prepared in Preparation Example 1 and 3 kg of polyacrylamide to the wastewater passing through the regulating tank to make the colloidal particles and tiny suspended solids in the wastewater coagulate into larger flocs, and remove them through sedimentation, and then further remove fine particles, organic matters and other impurities in the wastewater through methods such as sand filtration and activated carbon filtration to obtain the preliminarily filtered wastewater;

[0086] S2: Lift the preliminarily filtered wastewater by a water pump and feed it into a security filter for secondary filtration to obtain the wastewater after secondary filtration;

[0087] S3: Feed the wastewater after secondary filtration into the NXF membrane system from the water inlet 21 of the A end cap 2. The wastewater will enter the membrane element 5 and be divided into two streams after filtration. One is the concentrated solution that does not reach the set concentration, and the other is the permeate. The concentrated solution that does not reach the set concentration will enter the B end cap 3 through the filtration of the membrane element 5 and be discharged from the concentrated water outlet 31. Then, repeat the above operation, enter the water inlet 21 of the A end cap 2 again, enter the membrane element 5 for filtration again. When the concentration reaches the set concentration, it will be discharged from the concentrated water outlet 31 of the B end cap 3 and enter the concentrated storage tank for other treatments. The permeate will enter the water production cavity 51 and be discharged from the water production outlet 61 for subsequent treatment;

[0088] The subsequent treatment includes reuse or discharge. Among them, reuse or discharge means that if the water quality meets the requirements of production recycled water, it can be recycled for water washing, rinsing and other links in 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 body; if there are higher discharge requirements, appropriate treatment processes can be supported according to the discharge requirements.

[0089] Examples 2 - 7

[0090] A process for treating dyeing wastewater by membrane method, which is different from Example 1 in that the sources of the coagulants are different. The coagulants in Examples 2 - 7 are respectively prepared by Preparation Examples 2 - 7.

[0091] Example 8

[0092] A process for treating dyeing wastewater by membrane method, which is different from Example 6 in that the attapulgite in the coagulant is pretreated by the following method before use:

[0093] B1: Put the attapulgite into water, add sodium hexametaphosphate, mix evenly, and perform ultrasonic dispersion at a power of 80w for 30min to obtain a mixed solution;

[0094] B2: Let the mixed solution stand, stratify, and centrifuge to obtain a precipitate. Wash it with water 5 times, heat it to 350°C, and activate it for 2h to obtain the activated attapulgite;

[0095] B3: Put the activated attapulgite into a hydrochloric acid solution with a mass fraction of 30%, mix evenly, heat it up to 80°C, react for 1.5h, cool it, filter it, and wash the solid with water until it is neutral to obtain the pretreated attapulgite;

[0096] Among them, the addition amount of water for every 1 g of attapulgite in step B1 is 15 mL, the weight ratio of attapulgite to sodium hexametaphosphate is 1:0.25, and the addition amount of acid solution for every 1 g of activated attapulgite is 12 mL.

[0097] Comparative example

[0098] Comparative example 1

[0099] A process for treating dyed wastewater by membrane method, the difference between it and Example 1 is that the coagulant is not modified by 2-(3-aminopropyl) ethyltriethoxysilane.

[0100] Comparative example 2

[0101] A process for treating dyed wastewater by membrane method, the difference between it and Example 1 is that the coagulant is not loaded with nano zero-valent aluminum.

[0102] Comparative example 3

[0103] A process for treating dyed wastewater by membrane method, the difference between it and Example 1 is that the coagulant is polyferric sulfate.

[0104] Comparative example 4

[0105] A process for treating dyed wastewater by membrane method, the difference between it and Example 1 is that the wastewater after secondary filtration in step S3 is filtered through a polysulfone nanofiltration membrane.

[0106] Performance detection test

[0107] The following performance detections are carried out on the treated wastewater in Examples 1-8 and Comparative Examples 1-3:

[0108] COD: The COD in the treated wastewater is determined according to HJ-T399-2007 "Determination of Chemical Oxygen Demand in Water Quality - Fast Digestion Spectrophotometry Method", and the detection results are shown in Table 1.

[0109] Chromaticity: The chromaticity in the treated wastewater is determined according to GB11903-1989 "Determination of Chromaticity in Water Quality", and the detection results are shown in Table 1.

[0110] Ammonia nitrogen: The ammonia nitrogen in the treated wastewater is determined according to HJ535-2009 "Determination of Ammonia Nitrogen in Water Quality - Nessler's Reagent Spectrophotometry Method", and the detection results are shown in Table 1.

[0111] Total nitrogen: The total nitrogen in the treated wastewater is determined according to HJ636-2012 "Determination of Total Nitrogen in Water Quality - Alkaline Potassium Persulfate Digestion Ultraviolet Spectrophotometry Method", and the detection results are shown in Table 2.

[0112] Suspended solids: The suspended solids in the treated wastewater were determined according to GB / T 11901-1989 "Gravimetric Method for the Determination of Suspended Solids in Water Quality", and the test results are shown in Table 2.

[0113] The COD content in the initial dyeing wastewater was 2500 mg / L, the chromaticity was 500 times, the ammonia nitrogen content was 150 mg / L, the total nitrogen content was 200 mg / L, and the suspended solids content was 400 mg / L.

[0114] Table 1 Test Results

[0115]

[0116] Table 2 Test Results

[0117]

[0118]

[0119] Combining Table 1 and Table 2, it can be seen that the process of treating dyeing wastewater by the membrane method in this application significantly reduces the contents of COD, chromaticity, ammonia nitrogen, total nitrogen, and suspended solids in the wastewater through the interaction between various steps, and improves the treatment effect of the wastewater. Among them, the removal rate of COD is 99.928 - 99.968%, the removal rate of chromaticity 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 removal rate of COD in Example 1 is 99.928%, the removal rate of chromaticity is 97.4%, the removal rate of ammonia nitrogen is 98.07%, the removal rate of total nitrogen is 97.1%, and the removal rate of suspended solids is 100%, which is better than that of Comparative Examples 1 - 3. This shows that it is more appropriate to modify the biochar / palygorskite composite material with 2-(3-aminopropyl)ethyltriethoxysilane as the coagulant and load nano-zero-valent aluminum, which can more effectively improve the removal rate of COD, chromaticity, ammonia nitrogen, total nitrogen, and suspended solids in the wastewater.

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

[0122] Combined with Examples 1-7, it can be seen that the removal rate of COD in Example 6 is 99.964%, the removal rate of chromaticity is 98.6%, the removal rate of ammonia nitrogen is 98.73%, the removal rate of total nitrogen is 98.7%, and the removal rate of suspended solids is 100%, which is better than other examples. This indicates that it is more appropriate to use the coagulant prepared in Preparation Example 6, and the addition amounts of biochar, 2-(3-aminopropyl)ethyltriethoxysilane, and aluminum chloride in Preparation Example 6 are more appropriate. If the addition amount is too small, the optimal adsorption effect cannot be achieved; if the addition amount is too large, agglomeration may occur, resulting in uneven dispersion and affecting the performance, thus affecting the treatment effect of wastewater.

[0123] Combined with Example 6 and Example 8, it can be seen that the removal rate of COD in Example 8 is 99.968%, the removal rate of chromaticity is 99.0%, the removal rate of ammonia nitrogen is 99.87%, the removal rate of total nitrogen is 98.95%, and the removal rate of suspended solids is 100%, which is better than Example 6. This indicates that it is more appropriate to pretreat attapulgite before use, removing the impurities in attapulgite and dredging the pores. This can not only increase the specific surface area and pore volume, but also improve the cation exchangeability and adsorption capacity, further enhancing the adsorption of pollutants such as COD and organic matter in wastewater, and thus improving the treatment effect of wastewater.

[0124] As mentioned above, the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples or perform equivalent substitutions for some of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the present invention in each example.

Claims

1. A process for treating dyed wastewater by membrane method, characterized in that: It includes the following steps: S1: Pretreat the dyed wastewater, including grille filtration, equalization in the equalization tank, coagulation sedimentation, and filtration to obtain the preliminarily filtered wastewater; S2: Let the preliminarily filtered wastewater enter the cartridge filter for secondary filtration to obtain the secondary filtered wastewater; S3: Let the secondary filtered wastewater enter the NXF membrane system. The wastewater will be divided into two streams. One is the concentrated solution that does not reach the set concentration, and the other is the permeate. The concentrated solution that does not reach the set concentration will return to the front-end inlet and enter the NXF membrane system for filtration again. When the concentration reaches the set concentration, it will enter the concentrated storage tank for other treatments, and the permeate will enter the subsequent treatment; Among them, a coagulant is required for coagulation sedimentation in step S1.

2. The process for treating dyed wastewater by membrane method according to claim 1, characterized in that: The coagulant is prepared by modifying a biochar / palygorskite composite with 2-(3-aminopropyl)ethyltriethoxysilane and loading nano-zero-valent aluminum.

3. The process for treating dyed wastewater by membrane method according to claim 1, characterized in that: The coagulant is prepared by the following method: A1: Mix biochar and palygorskite, put them into a sodium hydroxide solution, mix evenly, impregnate, filter, take out, dry, crush, grind, and then pyrolyze, wash, and dry to obtain the biochar / palygorskite composite; A2: Put the biochar / palygorskite composite into an ethanol solution, add 2-(3-aminopropyl)ethyltriethoxysilane, mix evenly, heat up, react, cool, wash, and dry to obtain a mixture; A3: Under the protection of an inert gas, put aluminum chloride into an ethanol solution, mix evenly to obtain an aluminum salt solution, put the mixture into the aluminum salt solution, mix evenly, under the action of ultrasound, rotate and oscillate, then add a sodium borohydride solution, continuously stir, react, filter by suction, and separate to prepare the coagulant.

4. The process for treating dyed wastewater by membrane method according to claim 3, characterized in that: The weight ratio of palygorskite, biochar, 2-(3-aminopropyl)ethyltriethoxysilane, and aluminum chloride is 1:(0.2 - 1):(0.3 - 0.6):(0.2 - 0.5).

5. The process for treating dyed wastewater by membrane method according to claim 1, characterized in that: The palygorskite is pretreated as follows before use: B1: Put palygorskite into water, add a dispersant, mix evenly, and ultrasonically disperse to obtain a mixed solution; B2: Let the mixed solution stand, stratify, and centrifuge to obtain a precipitate, wash, heat, and activate to obtain the activated palygorskite; B3: Put the activated palygorskite into an acid solution, mix evenly, heat up, react, cool, filter, and wash the solid to obtain the pretreated palygorskite.

6. The process for treating dyed wastewater by membrane method according to claim 1, characterized in that: The biochar is one or more of wheat straw, corn straw, and rice straw.

7. The process for treating dyed wastewater by membrane method according to claim 1, characterized in that: The NXF membrane system includes a housing (1), an A end cap (2), a B end cap (3), a quick-install fastening kit (4), a membrane element (5), and water production conduits (6) respectively located in the A end cap (2) and the B end cap (3). The housing (1) is arranged in a cylindrical shape with a hollow interior and open ends. The A end cap (2) and the B end cap (3) are both arranged in a cylindrical shape with a hollow interior and one open end. The A end cap (2) is arranged at the bottom end of the housing (1), and the B end cap (3) is arranged at the top end of the housing (1). The open ends of both are fixed to the housing (1) through the quick-install fastening kit (4). An inlet (21) is fixedly provided on the A end cap (2), and a concentrated water outlet (31) is fixedly provided on the B end cap (3). The membrane element (5) is wound into a cylinder coaxial with the housing (1) and is fixedly arranged inside the housing (1), and a water production cavity (51) is formed at the central position along the height direction of the housing (1). The two water production conduits (6) are respectively arranged along the height direction of the housing (1), and the two ends close to the membrane element (5) respectively extend into the water production cavity (51) and are communicated with it. The end of the water production conduit (6) located in the B end cap (3) away from the membrane element (5) extends out of the B end cap (3) and is fixedly provided with a water production outlet (61).

8. The process for treating dyed wastewater by membrane method according to claim 7, characterized in that: The membrane element (5) is an NXF membrane and is a hollow fiber nanofiltration membrane.

9. The process for treating dyed wastewater by membrane method according to claim 1, characterized in that: The subsequent treatment of the permeate in step S3 includes reuse or discharge.

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