A method for recycling vat dyeing wastewater for fabric coating dyeing

Abstract

The present invention discloses a method for recycling reductive dyeing wastewater for fabric coating dyeing, belonging to the field of dyeing and finishing. The method comprises the following steps: filtering the dyeing wastewater to obtain a hairiness filter residue and a filtrate; grinding the hairiness filter residue and then drying it; using the obtained powder as a first dye; adding hydrotalcite to the filtrate; stirring and filtering it to obtain a second dye; mixing the first dye, the second dye, a thickener, a resin, and a color fixing agent into a coating; and coating undyed fabric with the coating to obtain a dyed fabric. The method can recover most of the dye, which is beneficial for reducing the COD of the wastewater. The filter residue is also recovered, greatly reducing the pressure on the subsequent sewage treatment of the filtrate and discharge. The method also realizes the recycling of the dye, forming a closed loop of the added dye, and reusing the excess dye in another type of product, thereby reducing dye waste and environmental impact, and facilitating clean production.

Description

Technical Field

[0001] The invention relates to a method for recycling reduction dyeing wastewater to dye fabric coatings, and belongs to the field of dyeing and finishing. Background Art

[0002] The textile industry is a pillar industry and a livelihood-oriented sector of national development. With economic growth and social progress, the textile industry, through continuous innovation and development, has become interwoven into people's daily lives and remains inextricably linked. China, a major textile producer, holds an irreplaceable position in the development of the textile industry. Industrialization has heightened awareness of water pollution. Fabric production generates significant amounts of dyeing wastewater. For example, the warp yarn of denim fabric is dyed with indigo, a vat dye. Its wastewater has a high COD (chemical oxygen demand). Direct discharge of indigo dyeing wastewater would cause water pollution and undermine the sustainable development of the textile industry. Therefore, indigo dyeing wastewater requires a series of wastewater treatment processes for legal discharge, resulting in high treatment costs.

[0003] The warp yarn of traditional denim fabrics must go through multiple dyeing processes to achieve the dyed yarn effect. Generally, it undergoes a scouring, a clean water washing, 6-8 dyeing treatments, and three clean water treatments in multiple consecutive tanks. The liquid in each tank reaches 800L-1000L. The yarn continuously moving on the production line will bring a large amount of dye liquid to the clean water treatment tank. The clean water treatment tank needs to be constantly replenished with clean water. Therefore, a large amount of wastewater is generated during the warp yarn dyeing process. In addition, when denim clothing is washed and aged to create a retro style, a large amount of dye-containing wastewater is also generated. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention provides a method for recycling vat dyeing wastewater for fabric coating dyeing, which reduces dye waste. While recycling the dye in the vat dyeing wastewater, it also serves as a part of the sewage treatment process, thereby alleviating the pressure of sewage treatment.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A method for recycling vat dyeing wastewater for fabric coating dyeing comprises the following steps:

[0007] Filtering the dyeing wastewater to obtain hairiness residue and filtrate;

[0008] Grinding the hairiness filter residue and drying it to obtain a powder as a first dye;

[0009] adding hydrotalcite to the filtrate, stirring and filtering to obtain a second dye;

[0010] mixing the first colorant, the second colorant, a thickener, a resin, and a color fixing agent to form a coating;

[0011] The coating is used to coat undyed fabric to obtain dyed fabric.

[0012] The method provided in the present application for recycling vat dyeing wastewater for fabric coating dyeing can recover the hairiness and most of the dyes in the vat dyeing wastewater, and use the components that were originally discarded to make coatings for coloring fabrics, which is beneficial to reducing dye waste and alleviating the pressure on sewage treatment.

[0013] Furthermore, the step of grinding the hairiness filter residue and then drying it comprises:

[0014] drying the hairiness filter residue to obtain a dry filter residue;

[0015] Adding a dispersant and water to the dry filter residue to obtain a mixed solution; the mixed solution contains 5wt%-20wt% of the dry filter residue, 5wt%-25wt% of the dispersant, and the balance is water;

[0016] Grinding the mixed solution to obtain a fiber powder suspension; the grinding frequency is 1000 rpm / min-2000 rpm / min, and the grinding time is 5 h-8 h;

[0017] The fiber powder suspension is dried to obtain the first dye.

[0018] Adding a dispersant improves the grinding effect and makes the hairiness more evenly crushed. Moreover, the dispersant added at this time enters the paint along with the first dye, which helps to evenly disperse the paint. In this application, the hairiness filter residue is dried first and then mixed with the dispersant for grinding, which helps to control the ratio of dispersant to hairiness and the amount of dispersant ultimately mixed into the paint.

[0019] Furthermore, the solvent of the coating is water, and each kilogram of the coating includes 30g-60g of the first colorant, 50g-80g of the second colorant, 25g-30g of the thickener, 8g-12g of the resin and 8g-12g of the fixing agent.

[0020] Furthermore, the step of coating undyed fabric with the coating to obtain dyed fabric includes drying at 65°C-75°C for 12min-18min after coating, and then fixing at 160°C-170°C for 25min-35min.

[0021] Conventional warp yarn sizing and dyeing requires repeated immersion and oxidation in a dye solution at around 70°C to achieve color development. The viscosity of the coating prepared in this application is much greater than that of conventional dye solution and is not suitable for immersion. Therefore, after coating, high-temperature oxidation at 160°C-170°C is performed to achieve color fixation.

[0022] Furthermore, the amount of the hydrotalcite is 3 g per liter of the filtrate.

[0023] The vat dyeing wastewater is alkaline, and 3g / L of hydrotalcite can adsorb the vat dye to form a precipitate, separating most of the dyes that have not been dyed from the wastewater.

[0024] Furthermore, the stirring treatment requires stirring at a frequency of 1500-2000 rpm / min for 1.5-3 hours, then reducing the stirring frequency to 500-600 rpm / min and continuing stirring for 15-25 minutes. In other words, high-speed stirring is first used to evenly disperse the hydrotalcite in the dyeing wastewater, followed by switching to low-speed stirring to create a favorable environment for precipitation.

[0025] Furthermore, the fabric undergoes a pre-treatment prior to coating, including singeing and scouring. Undyed fabrics have a large amount of hairiness on their surface, which can hinder contact between the coating and the fabric and consume some of the coating. Singeing removes most of the hairiness, facilitating direct contact between the coating and the fabric, reducing coating waste. Scouring removes wax and grease from the fibers, strengthening the adhesion between the coating and the fabric.

[0026] Furthermore, the scouring treatment is to place the fabric into a treatment liquid and treat it at an ultrasonic frequency of 800Hz-1200Hz, wherein the treatment liquid contains 4g / L-8g / L of ethanol and 1g / L-2g / L of a penetrant.

[0027] Conventional scouring treatment requires placing the fabric in a sodium hydroxide solution of a certain concentration at 90-95°C. This not only consumes a lot of energy, but also creates a humid environment in the hot water tank, making it more likely for hairiness floating in the factory to fall onto equipment, causing stains on the fabric. This application replaces the scouring treatment with a room-temperature ethanol solution, combined with ultrasound assistance, to achieve wax removal, resulting in lower energy consumption and improved surface quality of the treated fabric.

[0028] Furthermore, the pre-treatment also includes irradiating the fabric after the scouring treatment. The irradiation treatment steps include placing the fabric at a distance of 60cm-80cm from the plasma torch nozzle and irradiating it with argon plasma. The irradiation power is 80W-110W and the treatment time is 2min-6min.

[0029] Irradiation with argon plasma can quickly destroy the fiber structure to a certain extent, making it easier for the fiber to combine with the coating when the coating is subsequently applied, and the bonding strength between the fabric and the coating is better.

[0030] Furthermore, the pretreatment also includes oxidation treatment of the fabric after irradiation treatment. The oxidation treatment step includes: soaking the fabric in 0.5% hydrogen peroxide and then placing it in an empty tank, and introducing 0.5L / min-1.5L / min of ozone into the tank. The total time for the oxidation treatment is 5min-10min.

[0031] By irradiating the fabric and combining it with multiple treatments of ozone and hydrogen peroxide, the fiber structure can be further destroyed, etching occurs on the surface of the fiber to form holes, the specific surface area of the fiber will increase, and the roughness of the fiber surface will be significantly enhanced, which can improve the wetting effect of the coating on the fiber.

[0032] The beneficial effects of the present invention are as follows: in the method of the present invention for recycling vat dyeing wastewater for dyeing fabric coatings, filtering the vat dyeing wastewater is also a link in the general vat dyeing wastewater treatment process, and the treatment of the filtrate can recover most of the dye, which is beneficial to reducing the COD of the wastewater, and the filter residue is also recovered, which greatly reduces the pressure of subsequent sewage treatment for treating the filtrate and discharging it. The present invention can effectively recover the dye in the vat dyeing wastewater, realize the recycling and reuse of the dye, form a closed loop of the added dye, and reuse the excess dye in another type of product, thereby reducing dye waste, reducing the impact on the environment, and being beneficial to achieving clean production.

[0033] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or may be understood through implementation of the present application. DETAILED DESCRIPTION

[0034] On the one hand, the synthesis of dyes is a complicated process, and the production of dyes causes great environmental pollution. On the other hand, vat dyes are the main culprit for the high COD value of vat dyeing wastewater. Recycling and reusing vat dyes can not only avoid the production of more dyes, but also reduce the COD value of vat dyeing wastewater.

[0035] The present invention provides a method for recycling dyeing wastewater to dye fabric coatings, comprising the following steps:

[0036] S1: Filter the dyeing wastewater to obtain hairiness residue and filtrate.

[0037] S2: Grinding the hairiness residue and drying it to obtain a powder which is used as the first dye.

[0038] S3: adding hydrotalcite to the filtrate, stirring and filtering to obtain a second dye.

[0039] S4: Mix the first colorant, the second colorant, the thickener, the resin, and the color fixing agent to form a coating.

[0040] S5: coating the undyed fabric with a coating to obtain a dyed fabric.

[0041] Among them, step S1 is originally a link in the general process of reducing dyeing wastewater treatment. After completing the embodiment of the present application, it is actually equivalent to treating half of the reducing dyeing wastewater. After further treatment, it can meet the discharge standard. The embodiment of the present application can recover most of the dye, which is beneficial to reducing the COD of the wastewater, and the filter residue is also recovered, which greatly reduces the pressure of sewage treatment for subsequent treatment of the filtrate and discharge. In addition, the embodiment of the present application can effectively recover the dye in the reducing dyeing wastewater, realize the recycling and reuse of the dye, form a closed loop of the added dye, and reuse the excess dye in another type of product, which is equivalent to making the sewage treatment process also produce some benefits, reducing dye waste, reducing the impact on the environment, and facilitating clean production.

[0042] Specifically, step S2 includes:

[0043] S21: Drying the hairiness filter residue to obtain a dry filter residue.

[0044] S22: adding a dispersant and water to the dry filter residue to obtain a mixed solution, wherein the mixed solution contains 5 wt%-20 wt% of the dry filter residue, 5 wt%-25 wt% of the dispersant, and the balance is water.

[0045] S23: Grinding the mixed solution to obtain a fiber powder suspension. The grinding frequency is 1000 rpm / min-2000 rpm / min, and the grinding time is 5 h-8 h.

[0046] S24: Drying the fiber powder suspension to obtain a first dye.

[0047] Adding a dispersant improves the grinding effect and evenly crushes the hairiness. Furthermore, the dispersant added in step S2 enters the coating along with the first dye in step S4, promoting uniform dispersion of the coating. The present invention first dries the hairiness filter residue before mixing it with the dispersant and grinding it. This facilitates controlling the ratio of dispersant to hairiness and the amount of dispersant ultimately incorporated into the coating, eliminating the need for additional dispersant to be added to subsequent coatings.

[0048] Specifically, the solvent of the paint is water, and each kilogram of the paint includes 30g-60g of the first colorant, 50g-80g of the second colorant, 25g-30g of the thickener, 8g-12g of the resin and 8g-12g of the color fixing agent.

[0049] Using this coating, step S5 includes drying at 65°C-75°C for 12-18 minutes after coating, followed by color fixation at 160°C-170°C for 25-35 minutes. Conventional warp yarn sizing requires repeated immersion and oxidation in a dye liquor at around 70°C to achieve color development. The viscosity of the coating prepared in this application is much greater than that of conventional dye liquor, making it unsuitable for immersion. Therefore, after coating, high-temperature oxidation at 160°C-170°C is performed to achieve color fixation.

[0050] Traditional denim fabric is constructed from sizing and dyeing warp yarns and natural white weft yarns woven into a twill weave. After weaving, it undergoes a post-weaving treatment (using oxygen bleaching, chlorine bleaching, and other aging processes), resulting in a vintage blue-white effect on the front. Preferably, in the embodiments of the present application, the coated fabric is a cotton-stretch denim fabric containing a face yarn and spandex. By utilizing the difference in the coating's binding strength between the two fibers, the coated fabric is washed to remove any loose coating, creating a vintage denim effect even on the fully coated fabric. Furthermore, the fabric exhibits excellent color fastness, enabling energy-efficient and environmentally friendly production.

[0051] The reduced dyeing wastewater is alkaline. In step S3, 3 g / L of hydrotalcite can adsorb the reduced dye to form a precipitate, separating most of the undyed dye from the wastewater. After filtration in step S3, the filter residue is the second dye, and the COD value in the filtrate is greatly reduced, which helps to reduce the difficulty of subsequent wastewater treatment.

[0052] The stirring process in step S3 requires stirring at a frequency of 1500-2000 rpm / min for 1.5-3 hours, then reducing the frequency to 500-600 rpm / min and continuing stirring for 15-25 minutes. This means that high-speed stirring is initially used to evenly disperse the hydrotalcite in the dyeing wastewater, followed by switching to low-speed stirring to create a favorable environment for precipitation.

[0053] Preferably, the fabric is pre-treated before coating to improve the utilization rate of the coating and enhance the bonding strength between the fabric and the coating. The pre-treatment includes, in order: singeing, scouring, irradiation and oxidation.

[0054] During the singeing treatment, the treatment temperature is 300-500°C and the machine speed is 70m / min-80m / min.

[0055] The scouring treatment is to place the fabric in a treatment liquid and treat it at an ultrasonic frequency of 800Hz-1200Hz. The treatment liquid contains 4g / L-8g / L of ethanol and 1g / L-2g / L of penetrant.

[0056] There are a lot of hairs on the surface of undyed fabrics, which will hinder the contact between the paint and the fabric, and will consume part of the paint. The singeing treatment can remove most of the hairs on the surface of the undyed fabric, which is beneficial for the direct contact between the paint and the fabric, reducing paint waste. The scouring treatment can remove wax and grease in the fiber, which is beneficial for the paint to have a stronger bonding force with the fabric. In addition, the conventional scouring treatment requires the fabric to be placed in a sodium hydroxide solution of a certain concentration and treated at a high temperature of 90-95°C. In addition to the high energy consumption, the high-temperature water tank forms a humid environment, and the hairs floating in the factory are more likely to fall onto the equipment, forming stains on the fabric. The present application changes the scouring treatment to use a room temperature ethanol solution, combined with ultrasonic assistance, to achieve wax removal, with lower energy consumption and fewer stains on the surface of the treated fabric.

[0057] The irradiation process involves placing the fabric 60-80 cm from the plasma torch nozzle and irradiating it with argon plasma at a power of 80-110 W for 2-6 minutes. Irradiation with Ar plasma quickly and to a certain extent breaks down the fiber structure, making it easier for the fibers to bond with the coating during subsequent coating application, resulting in a better bond between the fabric and the coating.

[0058] The oxidation treatment process involves soaking the fabric in 0.5% hydrogen peroxide and then placing it in an empty tank. Ozone is then introduced into the tank at a rate of 0.5-1.5 L / min. The total oxidation treatment time is 5-10 minutes. The tank used is a standard sizing and dyeing machine tank.

[0059] By irradiating the fabric and combining it with multiple treatments of ozone and hydrogen peroxide, the fiber structure can be further destroyed, etching occurs on the surface of the fiber to form holes, the specific surface area of the fiber will increase, and the roughness of the fiber surface will be significantly enhanced, which can improve the wetting effect of the coating on the fiber.

[0060] Example 1

[0061] Wastewater from the three water treatment tanks of the combined sizing and dyeing machine in production line No. 1 was collected and filtered using a ceramic membrane with a pore size distribution of 30nm-300nm to obtain a hairiness residue and a filtrate. The hairiness residue was dried, and a dispersant and water were added to the dry residue to form a mixture containing 20wt% dry residue and 25wt% dispersant. The mixture was ground at 1500rpm / min for 8 hours to obtain a fiber powder suspension. The fiber powder suspension was dried to obtain the first dye. Hydrotalcite was added to the filtrate to 3g / L, and the stirring frequency was increased to 2000rpm / min for 3 hours. The stirring frequency was then reduced to 500rpm / min and the treatment time was 15 minutes. The mixture was then filtered and the COD value of the filtrate was measured to be 568mg / L. The residue was the second dye, and the COD value was reduced by 753mg / L compared to the collected wastewater.

[0062] White cotton stretch denim fabric was pre-treated, including singeing and scouring. The scouring treatment was performed at an ultrasonic frequency of 1200 Hz, with the treatment solution containing 6 g / L ethanol and 2 g / L penetrant.

[0063] The coating is prepared. The solvent of the coating is water. Each kilogram of the coating includes 30g of the first colorant, 70g of the second colorant, 30g of the thickener, 12g of the resin and 10g of the color fixing agent.

[0064] The resulting coating was applied to the pre-treated fabric, dried at 70±1°C for 15 minutes, and then fixed at 165±1°C for 30 minutes. After washing once and drying, the fabric's dry rubbing color fastness was measured to be level 5, and its wet rubbing color fastness was level 3-4.

[0065] Example 2

[0066] Wastewater from the three clear water treatment tanks of the combined sizing and dyeing machine in production line No. 2 was collected and filtered using a ceramic membrane with a pore size distribution of 30nm-300nm to obtain a hairiness residue and a filtrate. The hairiness residue was dried, and a dispersant and water were added to the dry residue to create a mixture containing 5wt% dry residue and 8wt% dispersant. The mixture was ground at 2000rpm / min for 5 hours to obtain a fiber powder suspension. The fiber powder suspension was dried to obtain the first dye. Hydrotalcite was added to the filtrate to 3g / L, and the stirring frequency was increased to 1500rpm / min for 3 hours. The stirring frequency was then reduced to 600rpm / min for 25 minutes. The mixture was then filtered and allowed to stand. The COD value of the filtrate was measured to be 591mg / L. The residue was the second dye, representing a COD reduction of 730mg / L compared to the collected wastewater.

[0067] White cotton-stretch denim fabric was pre-treated, including singeing, scouring, and irradiation. Scouring was performed at an ultrasonic frequency of 800 Hz using a treatment solution containing 8 g / L ethanol and 1.5 g / L penetrant. Irradiation involved irradiating the fabric with argon plasma at a power of 110 W for 2 minutes, while the fabric was positioned 60-80 cm from the plasma torch.

[0068] The coating is prepared. The solvent of the coating is water. Each kilogram of the coating includes 50g of the first colorant, 50g of the second colorant, 25g of the thickener, 8g of the resin and 8g of the fixing agent.

[0069] The resulting coating was applied to the pre-treated fabric, dried at 68±1°C for 18 minutes, and then fixed at 168±1°C for 25-35 minutes. After washing once and drying, the fabric's dry rubbing color fastness was measured to be level 4, and its wet rubbing color fastness was level 2-3.

[0070] Example 3

[0071] Wastewater from the three clear water treatment tanks of the combined slurry and dyeing machine in production line No. 3 was collected and filtered using a ceramic membrane with a pore size distribution of 30nm-300nm to obtain a hairiness residue and a filtrate. The hairiness residue was dried, and a dispersant and water were added to the dry residue to prepare a mixture containing 10wt% dry residue and 13wt% dispersant. The mixture was ground at 1000rpm / min for 7 hours to obtain a fiber powder suspension. The fiber powder suspension was dried to obtain the first dye. Hydrotalcite was added to the filtrate to 3g / L, and the stirring frequency was increased to 1800rpm / min for 2 hours. The stirring speed was then reduced to 550rpm / min and the treatment was continued for 20 minutes. The mixture was then filtered and the COD value of the filtrate was measured to be 584mg / L. The residue was the second dye, which showed a COD reduction of 737mg / L compared to the collected wastewater.

[0072] White cotton-stretch denim fabric underwent pretreatment, including singeing, scouring, irradiation, and oxidation. Scouring was performed at an ultrasonic frequency of 1000 Hz, using a treatment solution containing 6 g / L of ethanol and 1 g / L of a penetrant. Irradiation involved placing the fabric 60-80 cm from the plasma torch and irradiating it with argon plasma at 80 W for 6 minutes. Oxidation involved soaking the fabric in 0.5% hydrogen peroxide for 1 minute before placing it in an empty tank, where ozone was introduced at a flow rate of 0.5 L / min for 8 minutes.

[0073] The coating is prepared. The solvent of the coating is water. Each kilogram of the coating includes 40g of the first colorant, 50g of the second colorant, 28g of the thickener, 10g of the resin and 9g of the fixing agent.

[0074] The resulting coating was applied to the pre-treated fabric, dried at 66±1°C for 18 minutes, and then fixed at 162±1°C for 35 minutes. After washing once and drying, the fabric's dry rubbing color fastness was measured to be 4-5, and its wet rubbing color fastness was 3.

[0075] The present invention recycles dyes from wastewater produced by reactive dyeing of fabrics. First, fiber hairiness in the wastewater is collected and ground to obtain a first dye. A second dye is recovered using hydrotalcite, and the resulting dye is coated on the fabric to achieve dyeing. This effectively recovers the dye from the wastewater, enabling dye recycling, reducing dye production steps, and effectively minimizing environmental impact, thereby facilitating clean production. The coated fabric is then cleaned to remove some of the weak dye, resulting in a denim-like vintage effect and excellent color fastness.

[0076] Throughout this specification, references to terms such as "one embodiment," "certain embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" indicate that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0077] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for recycling vat dyeing wastewater for fabric coating dyeing, characterized in that: The following steps are involved: Filtering the reduction dyeing wastewater to obtain hairiness residue and filtrate; Grinding the hairiness filter residue and drying it to obtain a powder as a first dye; Adding hydrotalcite to the filtrate, stirring, and filtering to obtain a second dye; the amount of the hydrotalcite is 3 g per liter of the filtrate; the stirring process is required to first stir at a stirring frequency of 1500 rpm / min-2000 rpm / min for 1.5 hours to 3 hours, then reduce the stirring frequency to 500 rpm / min-600 rpm / min, and continue stirring for 15 minutes to 25 minutes; Mixing the first colorant, the second colorant, a thickener, a resin, and a color fixing agent to form a coating; the solvent of the coating is water, and each kilogram of the coating comprises 30g-60g of the first colorant, 50g-80g of the second colorant, 25g-30g of the thickener, 8g-12g of the resin, and 8g-12g of the color fixing agent; Using the coating to coat undyed fabric to obtain dyed fabric; The undyed fabric is a cotton-stretch denim fabric containing cotton yarn and spandex.

2. The method for recycling vat dyeing wastewater for fabric coating dyeing according to claim 1, characterized in that: The step of grinding the hairiness filter residue and then drying it comprises: drying the hairiness filter residue to obtain a dry filter residue; Adding a dispersant and water to the dry filter residue to obtain a mixed solution; the mixed solution contains 5wt%-20wt% of the dry filter residue, 5wt%-25wt% of the dispersant, and the balance is water; Grinding the mixed solution to obtain a fiber powder suspension; the grinding frequency is 1000 rpm / min-2000 rpm / min, and the grinding time is 5 h-8 h; The fiber powder suspension is dried to obtain the first dye.

3. The method for recycling vat dyeing wastewater for fabric coating dyeing according to claim 1, characterized in that: The step of coating undyed fabric with the coating to obtain dyed fabric comprises drying at 65-75° C. for 12-18 minutes after coating, and then fixing the color at 160-170° C. for 25-35 minutes.

4. The method for recycling vat dyeing wastewater for fabric coating dyeing according to claim 1, characterized in that: The fabric is pre-treated before coating, and the pre-treatment includes singeing treatment and scouring treatment.

5. The method for recycling vat dyeing wastewater for fabric coating dyeing according to claim 4, characterized in that: The scouring treatment is to place the fabric into a treatment liquid and treat it at an ultrasonic frequency of 800 Hz to 1200 Hz. The treatment liquid contains 4 g / L to 8 g / L of ethanol and 1 g / L to 2 g / L of a penetrant.

6. The method for recycling vat dyeing wastewater for fabric coating dyeing according to claim 4, characterized in that: The pre-treatment also includes irradiating the fabric after the scouring treatment. The irradiation treatment steps include placing the fabric at a distance of 60cm-80cm from the plasma torch and irradiating it with argon plasma. The irradiation power is 80W-110W and the treatment time is 2min-6min.

7. The method for recycling vat dyeing wastewater for fabric coating dyeing according to claim 6, characterized in that: The pretreatment also includes oxidation treatment of the fabric after irradiation treatment. The oxidation treatment step includes: soaking the fabric in 0.5% hydrogen peroxide and then placing it in an empty box tank, and introducing 0.5L / min-1.5L / min of ozone into the box tank. The total time of the oxidation treatment is 5min-10min.