Active dye adsorbent and preparation method thereof, and environmentally-friendly dyeing method for denim fabric

Abstract

The application discloses an active dye adsorbent and a preparation method thereof, and an environmentally-friendly dyeing method for jean fabric, and belongs to the field of textiles. The preparation method comprises the following steps: dissolving sucrose and sodium periodate in water, adjusting the mixed solution to be acidic, adding a precipitant after reaction, and filtering to obtain a formyl sucrose solution; dissolving chitosan in an acetic acid solution to obtain a chitosan solution; mixing the formyl sucrose solution and the chitosan solution, stirring, and filtering to obtain a solid active dye adsorbent. The adsorbent has good adsorption capacity for active blue 19 in an acidic environment, can elute the active blue 19 in an alkaline environment, and has good reusability, so that the active dye and the adsorbent can be reused, the environmentally-friendly dyeing method for jean fabric is applied, waste water can also have value, waste of the active dye can be reduced, subsequent waste water treatment pressure can be reduced, and waste water treatment cost can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to an active dye adsorbent and a preparation method thereof, and an environmentally-friendly dyeing method for denim fabric, and belongs to the field of textiles. BACKGROUND

[0002] With the rapid development of economy and the rapid growth of world population, the textile industry has ushered in a booming development, but also led to a large amount of water resources being seriously polluted. The usable amount of water resources is getting less and less, and now the scarcity of clean water resources has become an unbreakable shackles that restricts the development of the world. According to statistics, about 30% of the world's population cannot obtain safe drinking water. In some areas, sewage discharge is not strictly controlled, and the discharge of unqualified sewage contains various pollutants in the water, which has a huge impact on the environment and ecosystem.

[0003] Denim clothing has always stood on the stage of the clothing market and become an irreplaceable fashion element. When producing denim clothing, yarn is first dyed with indigo dye, and after the clothing is made, part of the dye is washed off through a washing process, which can give denim clothing additional value, and the appearance effect of "imitation old" retro can be achieved after the indigo dye is washed off. The bonding force of indigo dye with fibers is poor, and some processes use reactive dyes to dye yarn or fabric to make denim clothing with better color fastness. The wastewater after dyeing is usually treated and discharged, and the reactive dyes cannot be recycled. If the reactive dyes in the wastewater can be recycled, it will be beneficial to reduce the difficulty of subsequent wastewater treatment and reduce the waste of reactive dyes.

[0004] With the innovation and development of technology, a large number of new adsorbents have been developed. The current dye adsorbent has low adsorption capacity, and the unsatisfactory defect is poor reusability, which leads to high wastewater treatment cost. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the present application provides an active dye adsorbent with good reusability, a preparation method thereof, and an environmentally-friendly dyeing method for denim fabric by means of the adsorbent.

[0006] The technical scheme adopted by the present application to solve its technical problems is:

[0007] In a first aspect, the present application provides a preparation method of an active dye adsorbent, comprising the following steps:

[0008] Sodium periodate and sucrose are dissolved in water, and the pH is adjusted to 5.4-5.8 with phosphoric acid. After reacting for 3h-6h, barium chloride solution is added until no more precipitate is generated, and a formyl sucrose solution is obtained by filtration;

[0009] Chitosan is dissolved in a 4g / L-7g / L acetic acid solution to obtain a chitosan solution;

[0010] Mixing the formyl sucrose solution and the chitosan solution, filtering after stirring to obtain the solid active dye adsorbent.

[0011] The adsorbent provided by the application has good adsorption capacity for active blue 19 in an acidic environment, can elute active blue 19 in an alkaline environment, and has good reusability, so that the active dye and the adsorbent can both be reused, which is conducive to reducing the wastewater treatment cost.

[0012] Further, the chitosan is obtained by the following steps: adding chitin powder to a sodium hydroxide solution with a mass concentration of 40%, soaking at 120-130 DEG C for 12-16 hours, and then cooling to room temperature, and centrifuging to obtain the chitosan.

[0013] Further, the step of adjusting the mixture to be acidic includes adjusting the pH of the mixture to 5.4-5.8 with a phosphate buffer; and the step of adding a precipitant includes adding barium chloride solution until no more precipitate is produced.

[0014] Adjusting the pH with a phosphate buffer is conducive to inhibiting pH fluctuation in a long-time reaction process, and after the reaction, only an acidic environment needs to be maintained, without the need for strict pH control. After the reaction, the system contains iodate, which is a reduction product of periodate, and may also contain elemental iodine, which is a reduction product of iodate, and unreacted periodate. After adding barium chloride, insoluble barium periodate and barium iodate are formed, and the iodine-containing components can be removed by filtration. In the subsequent step, the formyl sucrose solution needs to be mixed with the chitosan solution, and chitosan phosphorylation can improve the water solubility of chitosan, which is not conducive to subsequent collection of the solid adsorbent. However, the addition of barium chloride not only helps to remove the iodine-containing components, but also forms barium phosphate and barium hydrogen phosphate precipitates, which facilitates the removal of phosphate.

[0015] Further, in the raw material of the formyl sucrose solution, the mass ratio of the sucrose is 5-8, the mass ratio of the sodium periodate is 9-11, and the mass ratio of the water is 85-95.

[0016] Controlling the pH and using the raw material dosage can avoid complete degradation of the carbon-carbon bond of sucrose, and promote more sucrose to react into formyl sucrose.

[0017] Further, in the step of mixing the formyl sucrose solution and the chitosan solution, the dosage of the formyl sucrose solution is 4wt%-8wt% of the dosage of the chitosan solution.

[0018] In a second aspect, the application provides an active dye adsorbent, which is prepared by the method for preparing an active dye adsorbent according to the first aspect, and has good adsorption capacity for active blue 19 in an acidic environment and can elute active blue 19 in an alkaline environment.

[0019] In a third aspect, the present application provides an environmentally-friendly dyeing method for denim fabric, comprising the following steps:

[0020] Filtering the wastewater containing reactive dyes to obtain wastewater filtrate and fiber residue;

[0021] Grinding the fiber residue to obtain a first dye;

[0022] Adjusting the wastewater filtrate to be acidic, then adding an adsorbent for adsorption, filtering to obtain adsorbent residue, eluting the adsorbent residue with an alkaline solution to obtain desorption solution and regenerated adsorbent; the adsorbent is selected from the reactive dye adsorbent of the second aspect, or the regenerated adsorbent is combined with the reactive dye adsorbent of the second aspect;

[0023] Mixing polyurethane emulsion, dispersant, crosslinking agent, ethylene-vinyl acetate, the first dye and the desorption solution to obtain a regenerated coating;

[0024] Coating the regenerated coating on the white denim fabric and baking to achieve color fixation.

[0025] The environmentally-friendly dyeing method divides the wastewater containing reactive blue 19 into two parts, the first part is the dyed fiber fluff, and the second part uses the adsorbent of the second aspect to absorb the reactive dyes, and the remaining components in the dyeing wastewater are less adsorbed, and the reactive blue 19 in the wastewater can be extracted after elution. This method can also fully recycle the dyes on the fiber fluff, and the adsorbent with good regeneration performance is used to extract the reactive dyes in the wastewater, so that the wastewater also has value, which is conducive to reducing the waste of reactive dyes, reducing the pressure of subsequent wastewater treatment, and reducing the cost of wastewater treatment.

[0026] Further, the step of grinding the fiber residue to obtain a first dye includes: placing the fiber residue into a shock-type grinding instrument, the grinding frequency is 2800 times / min-3500 times / min, the grinding time is 6 min-10 min, and the first dye with a particle size of 30 μm-100 μm is obtained by screening, which is convenient for subsequent uniform dispersion in the coating.

[0027] Further, in the step of adjusting the wastewater filtrate to be acidic, the pH of the wastewater filtrate is adjusted to 2, which is conducive to the full adsorption of the adsorbent to the reactive dyes; and the alkaline solution is a 1 g / L sodium hydroxide solution, which is conducive to the elution of as much reactive dyes as possible from the adsorbent.

[0028] Further, by mass, the regenerated coating includes 30-60 parts of the polyurethane emulsion, 2-4 parts of the dispersing agent, 1-3 parts of the cross-linking agent, 3-5 parts of the ethylene-vinyl acetate, 6-15 parts of the first dyeing agent, and 6-15 parts of the desorption liquid. The ethylene-vinyl acetate is melted in the process of baking and adheres to the surface of the fabric, which can improve the bonding degree with the fabric.

[0029] Further, in the step of baking, an eight-section oven is used, and the temperatures are set to 110℃, 120℃, 130℃, 130℃, 120℃, 110℃, 100℃, and 90℃, respectively. This is beneficial to avoid the rigidity of the coating after curing and color fixing and to keep the fabric soft.

[0030] The adsorbent prepared by the application has good adsorption capacity for active blue 19 in an acidic environment and can elute active blue 19 in an alkaline environment, and has good reusability, so that the active dye and the adsorbent can be reused, applied to the environmentally friendly dyeing method of denim fabric, and make the wastewater also have value, which is beneficial to reduce the waste of active dyes, reduce the subsequent wastewater treatment pressure, and reduce the wastewater treatment cost.

[0031] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. DETAILED DESCRIPTION

[0032] With the rapid development of the textile industry, the pressure of treating textile wastewater is increasing. If a large amount of textile printing and dyeing wastewater (containing organic matter, dyes, etc.) is discharged into water, it will seriously affect the safety of ecological water. In order to reduce the dyeing wastewater, people on the one hand strive to develop new non-toxic organic dyes, and on the other hand develop new adsorption materials to recover dyes in wastewater. The textile industry is large in scale, and how to reduce the discharge of wastewater containing organic dyes is a problem that needs to be solved urgently today.

[0033] Denim production enterprises will encounter the problem of discharging wastewater containing reactive dyes. The ideal adsorbent for absorbing reactive dyes should be able to eliminate various interactions between the adsorbent and the reactive dyes, and achieve efficient desorption. At the same time, the adsorbent should be able to repeatedly adsorb and desorb pollutants. Chitosan is a very promising candidate for a textile dye biosorbent because it is low in cost and has nearly 6 mmol / g of amine groups. Cross-linking, grafting and blending are common means to improve the wet stability and durability of chitosan-based adsorbents. However, many treatments have side effects, such as reducing the adsorption capacity of chitosan, for example, the reusability is poor. Most of the modification processes of chitosan use high temperature, which causes the physical form of the adsorbent to change, and the size of the adsorbent to shrink sharply. Before use, the distance between the polymer chains in the adsorbent is far apart, after the size of the adsorbent shrinks, the distance between the polymer chains is reduced, the interaction between the polymer and the absorbed dye is strengthened, and finally, the desorption capacity of the adsorbent is greatly weakened. Many chitosan-based adsorbents can only be used once, resulting in high cost of dyeing wastewater treatment, and if a recyclable adsorbent can be developed, the cost of dyeing wastewater treatment can be greatly reduced.

[0034] The present application provides a method for preparing a reactive dye adsorbent, comprising the following steps:

[0035] S01: Dissolve sucrose and sodium periodate in water, adjust the mixture to be acidic, after 3-6 hours of reaction, add a precipitant, and filter to obtain a formyl sucrose solution. The reaction formula (main reaction) of this step is shown in formula 1.

[0036] ;

[0037] Formula 1.

[0038] S02: Dissolve chitosan in a 4g / L-7g / L acetic acid solution to obtain a chitosan solution.

[0039] S03: Mix the formyl sucrose solution and the chitosan solution, stir and filter to obtain a solid reactive dye adsorbent. The reaction formula (main reaction) of this step is shown in formula 2, and Chitosan is chitosan.

[0040] ;

[0041] Formula 2.

[0042] The adsorbent provided by the embodiments of the present application has good adsorption capacity for active blue 19 in an acidic environment, and can elute active blue 19 in an alkaline environment, and has good reusability, so that both the reactive dyes and the adsorbent can be reused, which is conducive to reducing the cost of wastewater treatment.

[0043] In step S01, more raw materials are more conducive to react according to formula 1 by strictly controlling pH. After the reaction, especially after the consumption of sodium periodate, as long as the acidic environment is maintained, there is no need to strictly control the pH. Preferably, step S01 is specifically: dissolve sucrose and sodium periodate in water, adjust the mixture to 5.4-5.8 with a phosphate buffer solution, after 3h-6h of reaction, add barium chloride solution until no more precipitate is produced, and filter to obtain a formyl sucrose solution.

[0044] Adjusting the pH with a phosphate buffer solution is conducive to maintaining the pH of the reaction system for a long time. In the system after the reaction, there are iodate, the reduction product of periodate, and elemental iodine, the reduction product of iodate, and unreacted periodate. After adding barium chloride, insoluble barium periodate and barium iodate are formed, and the iodine-containing components can be removed by filtration. At the same time, barium phosphate and barium hydrogen phosphate precipitates are formed, which facilitates the removal of phosphate.

[0045] Specifically, step S01 can be: dissolving 5-8 parts of sucrose and 9-11 parts of sodium periodate by mass in water, adjusting the mixture to 5.4-5.8 with a phosphate buffer solution, after 3h-6h of reaction, adding barium chloride solution until no more precipitate is produced, and filtering to obtain a formyl sucrose solution. Controlling the pH and using this amount of raw materials avoids the complete breakage of the carbon-carbon bond of sucrose and the complete degradation of sucrose, which is conducive to promoting more sucrose to react to formyl sucrose according to formula 1.

[0046] Preferably, step S03 is specifically: mixing the formyl sucrose solution and the chitosan solution, the amount of formyl sucrose solution is 4wt%-8wt% of the amount of chitosan solution, stirring for 25min-35min, and then filtering to obtain a solid active blue 19 adsorbent.

[0047] The application also provides an environmentally friendly dyeing method for denim fabric, which comprises the following steps:

[0048] S1: filtering wastewater containing active blue 19 to obtain wastewater filtrate and fiber filter residue.

[0049] S2: grinding the fiber filter residue to obtain a first dye.

[0050] S3: adjusting the wastewater filtrate to be acidic, then adding an adsorbent for adsorption, filtering to obtain adsorbent filter residue, washing the adsorbent filter residue with an alkali solution to obtain desorption liquid and regenerated adsorbent.

[0051] The adsorbent is the adsorbent prepared in the above embodiments, including the adsorbent just prepared and the regenerated adsorbent recovered again.

[0052] S4: mixing polyurethane emulsion, dispersant, crosslinking agent, ethylene-vinyl acetate, first dye, and desorption liquid to obtain a regenerated coating.

[0053] S5: Apply the regenerated paint on the white denim fabric, and bake to achieve color fixation.

[0054] The method divides the wastewater containing active dyes into two parts, the first part is the dyed fiber fluff, and the second part uses the adsorbent of the second aspect to absorb the active dyes, and the remaining components in the dyeing wastewater are less adsorbed, and the active blue 19 in the wastewater can be extracted after elution. The method can also fully recycle the dyes on the fiber fluff, and use the adsorbent with good regeneration performance to extract the active dyes in the wastewater, so that the wastewater can also have value, which is conducive to reducing the waste of active dyes, reducing the pressure of subsequent wastewater treatment, and reducing the cost of wastewater treatment.

[0055] In step S1, the wastewater containing active blue 19 can be desizing wastewater, which contains a large amount of fiber fluff, and can collect more first dyes. The desizing wastewater can be filtered by a ceramic membrane with a pore size of 30-300 nm.

[0056] In step S2, the fiber filter residue can be put into a shock type grinder, the grinding frequency is 2800-3500 times / min, the grinding time is 6-10 min, and the first dye with a particle size of 30-100 μm can be obtained by screening, which is convenient for subsequent uniform dispersion in the paint.

[0057] In step S3, the pH of the wastewater filtrate is adjusted to 2, and the alkali solution is 1 g / L of sodium hydroxide solution, which is conducive to protecting the adsorbent and improving the recyclable times of the adsorbent.

[0058] In step S4, the paint includes polyurethane emulsion 30-60 parts, dispersant 2-4 parts, crosslinking agent 1-3 parts, ethylene-vinyl acetate 3-5 parts, first dye 6-15 parts, and desorption liquid 6-15 parts by mass. The mixing time is 20-30 min. Ethylene-vinyl acetate will melt during baking and adhere to the surface of the fabric, which can improve the bonding degree with the fabric.

[0059] In the prior art, a fixed temperature of 120°C is used during baking, which not only wastes energy, but also makes the fabric become stiff and not soft enough. If a continuously increasing temperature is used, the paint will not adhere firmly to the fabric at the beginning, which will cause the baking cylinder to be stained, resulting in quality problems of the coated fabric. Preferably, in step S5, the temperatures of the eight ovens are set to 110°C, 120°C, 130°C, 130°C, 120°C, 110°C, 100°C, and 90°C, respectively, which is conducive to avoiding the stiffness of the coated fabric after color fixation and color fixation, and maintaining the softness of the fabric, while avoiding the problem of staining the baking cylinder.

[0060] Example 1

[0061] Dissolve 5 parts of sucrose and 9 parts of sodium periodate in water by mass, adjust the mixture to 5.4-5.8 with a phosphate buffer solution, after 3h of reaction, add barium chloride solution until no more precipitate is produced, filter to obtain a formyl sucrose solution.

[0062] Dissolve chitosan in 4g / L acetic acid solution to obtain a chitosan solution. The chitosan is treated by the following steps: add chitin powder (Baoji Haiyunxin New Energy Technology Co., Ltd., hereinafter the same) to a 40% sodium hydroxide solution by mass, soak at 120-130℃ for 12h, then cool to room temperature, and centrifuge to obtain chitosan.

[0063] Mix the formyl sucrose solution and the chitosan solution, the amount of formyl sucrose solution is 4wt% of the amount of chitosan solution, stir for 25min, then filter to obtain the reactive dye adsorbent of Example 1.

[0064] Example 2

[0065] Dissolve 8 parts of sucrose and 11 parts of sodium periodate in water by mass, adjust the mixture to 5.4-5.8 with a phosphate buffer solution, after 4h of reaction, add barium chloride solution until no more precipitate is produced, filter to obtain a formyl sucrose solution.

[0066] Dissolve chitosan in 7g / L acetic acid solution to obtain a chitosan solution. The chitosan is treated by the following steps: add chitin powder to a 40% sodium hydroxide solution by mass, soak at 120-130℃ for 16h, then cool to room temperature, and centrifuge to obtain chitosan.

[0067] Mix the formyl sucrose solution and the chitosan solution, the amount of formyl sucrose solution is 8wt% of the amount of chitosan solution, stir for 35min, then filter to obtain the reactive dye adsorbent of Example 2.

[0068] Example 3

[0069] Dissolve 7 parts of sucrose and 10 parts of sodium periodate in water by mass, adjust the mixture to 5.4-5.8 with a phosphate buffer solution, after 6h of reaction, add barium chloride solution until no more precipitate is produced, filter to obtain a formyl sucrose solution.

[0070] Dissolve chitosan in 5g / L acetic acid solution to obtain a chitosan solution. The chitosan is treated by the following steps: add chitin powder to a 40% sodium hydroxide solution by mass, soak at 120-130℃ for 12-16h, then cool to room temperature, and centrifuge to obtain chitosan.

[0071] The formyl sucrose solution and the chitosan solution were mixed, the amount of the formyl sucrose solution was 6wt% of the amount of the chitosan solution, and after stirring for 30 min, filtration was performed to obtain the active dye adsorbent of Example 3.

[0072] Example 4

[0073] The desizing wastewater of the first production line was filtered by a ceramic membrane with a pore size of 300 nm to obtain wastewater filtrate and fiber residue.

[0074] The fiber residue was placed in a shock mill, the grinding frequency was 2800 times / min, the grinding time was 6 min, and screening was performed to obtain the first dye with a particle size of 30-100 μm.

[0075] The wastewater filtrate was adjusted to pH=2, and then the adsorbent prepared in Example 1 was added for adsorption, and filtration was performed to obtain adsorbent residue and residual wastewater of Example 4. The adsorbent residue was eluted with 1 g / L sodium hydroxide solution to obtain desorption liquid and regenerated adsorbent.

[0076] The absorbance of the desorption liquid and the residual wastewater after adsorption was measured by ultraviolet spectrophotometry at a wavelength of 592 nm, and the concentration of reactive blue 19 was indirectly calculated, and the removal rate of the dye was calculated to be 96.3%; and according to the volume and concentration of the desorption liquid, it was calculated that 87.9% of the dye in the adsorbent was removed.

[0077] 30 parts of polyurethane emulsion (Hefei Huaiyue New Material Technology Co., Ltd., the same below), 2 parts of dispersing agent, 3 parts of crosslinking agent, 4 parts of ethylene-vinyl acetate, 7 parts of the first dyeing agent, and 10 parts of desorption liquid were mixed, and the mixed solution was stirred for 20 min to obtain a regenerated coating.

[0078] The regenerated coating was coated on a white denim fabric, and baking was performed to realize fixation. During baking, the temperatures of the eight ovens were set to 110℃, 120℃, 130℃, 130℃, 120℃, 110℃, 100℃, and 90℃, respectively.

[0079] The dry rubbing fastness of the fabric was measured to be 4-5 grade, and the wet rubbing fastness was 3 grade.

[0080] Example 5

[0081] The desizing wastewater of the first production line was filtered by a ceramic membrane with a pore size of 200 nm to obtain wastewater filtrate and fiber residue.

[0082] The fiber residue was placed in a shock mill, the grinding frequency was 3500 times / min, the grinding time was 10 min, and screening was performed to obtain the first dye with a particle size of 30-100 μm.

[0083] The wastewater filtrate is adjusted to pH = 2, and then the adsorbent prepared in Example 2 is added for adsorption, and filtration is performed to obtain adsorbent filter residue and residual wastewater of Example 5. The adsorbent filter residue is eluted with 1 g / L sodium hydroxide solution to obtain desorption solution and regenerated adsorbent.

[0084] The absorbance of the residual wastewater desorption solution and the residual wastewater after being adsorbed is measured by a UV spectrophotometer at a wavelength of 592 nm, so as to indirectly calculate the concentration of Reactive Blue 19, and it is calculated that the removal rate of the dye is 92.3%; and then according to the volume and concentration of the desorption solution, it is calculated that 86.4% of the dye in the adsorbent is removed.

[0085] The 50 parts of polyurethane emulsion, 4 parts of dispersant, 2 parts of crosslinking agent, 5 parts of ethylene-vinyl acetate, 10 parts of first dyeing agent, and 6 parts of desorption solution are mixed, and the mixed solution is stirred for 30 min to obtain a regenerated coating.

[0086] The regenerated coating is coated on the white jean fabric, and baking is performed to realize fixation. When baking, the temperatures of the eight sections of the oven are set to 110℃, 120℃, 130℃, 130℃, 120℃, 110℃, 100℃, and 90℃, respectively.

[0087] It is measured that the dry rubbing color fastness of the fabric is 4-5 grade, and the wet rubbing color fastness is 3 grade.

[0088] Example 6

[0089] The desizing wastewater of the first production line is filtered by a ceramic membrane with a pore size of 100 nm to obtain wastewater filtrate and fiber filter residue.

[0090] The fiber filter residue is placed in a shock mill, the grinding frequency is 3000 times / min, and the grinding time is 8 min. Screening is performed to obtain a first dyeing agent with a particle size of 30-100 μm.

[0091] The wastewater filtrate is adjusted to pH = 2, and then the adsorbent prepared in Example 3 is added for adsorption, and filtration is performed to obtain adsorbent filter residue and residual wastewater of Example 6. The adsorbent filter residue is eluted with 1 g / L sodium hydroxide solution to obtain desorption solution and regenerated adsorbent.

[0092] The absorbance of the residual wastewater desorption solution and the residual wastewater after being adsorbed is measured by a UV spectrophotometer at a wavelength of 592 nm, so as to indirectly calculate the concentration of Reactive Blue 19, and it is calculated that the removal rate of the dye is 97.6%; and then according to the volume and concentration of the desorption solution, it is calculated that 89.1% of the dye in the adsorbent is removed.

[0093] The 60 parts of polyurethane emulsion, 4 parts of dispersant, 3 parts of crosslinking agent, 4 parts of ethylene-vinyl acetate, 8 parts of first dyeing agent, and 10 parts of desorption solution are mixed, and the mixed solution is stirred for 25 min to obtain a regenerated coating.

[0094] The regenerated paint is coated on the white jean fabric, and baking is performed to realize color fixing. During the baking, the temperature of the eight-section oven is set to 110℃, 120℃, 130℃, 130℃, 120℃, 110℃, 100℃, and 90℃, respectively.

[0095] It is measured that the dry rubbing color fastness of the fabric is 4-5 levels, and the wet rubbing color fastness is 3 levels.

[0096] The embodiment of the present application can effectively recycle and reuse the reactive blue 19 in the wastewater. First, the fiber hair in the wastewater is filtered and recycled, the fiber hair containing the dye is ground into small materials through a grinding process, and then the dye in the wastewater is further adsorbed by using a formyl sucrose-chitosan adsorbent, and the color removal rate is as high as 92%-98%. After desorption treatment, the adsorbed dye can be recycled, and the remaining impurities in the dyeing wastewater enter the next step of wastewater treatment with the remaining wastewater. The adsorbent can continue to be used for adsorption of the dye in the wastewater, realizing recycling and regeneration. It is conducive to realizing clean production, reducing pollution to the environment, and even the remaining wastewater can be used for water cleaning after dyeing, achieving recycling of water resources.

[0097] In the description of the present specification, the description referring to the terms "one embodiment", "certain embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the described embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0098] The above is the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered to be within the scope of protection of the present application.

Claims

1. An eco-friendly dyeing method of denim fabric, characterized in that, The method comprises the following steps: filtering wastewater containing active dyes to obtain wastewater filtrate and fiber residue; the active dyes are active blue 19; grinding the fiber residue to obtain a first dye; adjusting the wastewater filtrate to be acidic, then adding an adsorbent for adsorption, filtering to obtain adsorbent residue, eluting the adsorbent residue with an alkali solution to obtain desorption liquid and regenerated adsorbent; the adsorbent is an active dye adsorbent, or the regenerated adsorbent is combined with the active dye adsorbent; mixing polyurethane emulsion, dispersant, crosslinking agent, ethylene-vinyl acetate, the first dye and the desorption liquid to obtain regenerated paint; coating the regenerated paint on white jean fabric and baking to realize fixation; the preparation steps of the active dye adsorbent comprise: dissolving sucrose and sodium periodate in water, adjusting the pH of the mixture to 5.4-5.8 with a phosphate buffer solution, adding a precipitant after 3h-6h of reaction, and filtering to obtain a formyl sucrose solution; dissolving chitosan in 4g / L-7g / L acetic acid solution to obtain a chitosan solution; mixing the formyl sucrose solution and the chitosan solution, stirring and filtering to obtain the solid active dye adsorbent; in the raw materials of the formyl sucrose solution, the sucrose is 5 parts-8 parts by mass, the sodium periodate is 9 parts-11 parts by mass, and the water is 85 parts-95 parts by mass.

2. The method of eco-friendly dyeing of denim fabric as claimed in claim 1 wherein, The step of grinding the fiber residue to obtain a first dye comprises: placing the fiber residue into a shock type grinder, grinding at a frequency of 2800 times / min-3500 times / min for 6min-10min, and sieving to obtain the first dye with a particle size of 30μm-100μm.

3. The method of eco-friendly dyeing of denim fabric as claimed in claim 1 wherein, In the step of adjusting the wastewater filtrate to be acidic, the pH of the wastewater filtrate is adjusted to 2; and the alkali solution is 1g / L sodium hydroxide solution.

4. The method of eco-friendly dyeing of denim fabric as claimed in claim 1 wherein, The regenerated paint comprises, by mass, 30 parts-60 parts of the polyurethane emulsion, 2 parts-4 parts of the dispersant, 1 part-3 parts of the crosslinking agent, 3 parts-5 parts of the ethylene-vinyl acetate, 6 parts-15 parts of the first dye, and 6 parts-15 parts of the desorption liquid.

5. The method of eco-friendly dyeing of denim fabric as claimed in claim 1 wherein, In the step of baking, an eight-section oven is used, and the temperatures are set to 110℃, 120℃, 130℃, 130℃, 120℃, 110℃, 100℃ and 90℃, respectively.

6. The method of eco-friendly dyeing of denim fabric as claimed in claim 1 wherein, The step of adding a precipitant comprises: adding barium chloride until no more precipitate is produced.

7. The method of eco-friendly dyeing of denim fabric as claimed in claim 1 wherein, In the step of mixing the formyl sucrose solution and the chitosan solution, the amount of the formyl sucrose solution is 4wt%-8wt% of the amount of the chitosan solution.