CN117624938A - Recycling method of dye in waste fabric - Google Patents

Abstract

The invention relates to a recycling method of dye in waste fabric, which can greatly improve the recycling efficiency of the waste fabric, realize the recycling of the waste fabric and the dye, has extremely high economic benefit and can save a large amount of resources.

Description

A method for recycling dyes in waste fabrics

Technical field

The invention belongs to the field of waste textiles, and particularly relates to a method for recycling dyes in waste fabrics.

Background technique

Denim clothing is deeply loved by consumers for its rough, simple and free style. With the development of the economy and the improvement of living standards, people's demand for denim clothing is increasing, and the corresponding number of discarded denim is also increasing year by year. According to relevant data, my country produces more than 26 million tons of waste textiles every year, but its recycling rate is less than 20%. Among them, the recycling rate of waste denim is less than 5%. About 20% of waste denim is usually recycled. Discarded in landfill or directly incinerated. The incineration process will also be accompanied by the production of large amounts of carbon dioxide and toxic gases, causing serious pollution problems. It can be seen that the recycling of waste denim clothing is particularly necessary. Waste denim contains a lot of dyes. It is of great significance to recover the dyes in waste denim and realize their reuse.

The prior art discloses a method for recycling indigo dye in waste jeans, which uses electrochemical technology to reduce the indigo dye in waste jeans, and further electrochemical reduction dyeing of the dye to achieve secondary reuse, but this technology needs to be reversible. The redox medium serves as an electron mediator, consumes a lot of chemical reagents and electricity, and the recycling cost is high. The prior art discloses an enzyme washing and decolorizing method for indigo denim, which uses a horseradish peroxidase/hydrogen peroxide catalytic system to decolorize denim. However, although this technology causes low fiber damage, its decolorization efficiency is low. Still needs to be improved. The prior art also discloses a pigment or coating based on waste denim and a preparation method thereof. The waste denim is cut into pieces, ground with a ball mill and then mixed with a cross-linking agent, a thickener and water to prepare the pigment or coating. However, In this method, the waste denim contains a large amount of residual cellulose and chemical reagents, which affects the performance of the pigment coating.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for recycling dyes in waste fabrics, so as to improve the economic benefits of recycling waste fabrics such as denim and promote the development of resource recycling.

A method for recycling dyes in waste fabrics of the present invention includes:

(1) Mix neutral mannanase, auxiliary chemical reagents, and water, and then adjust the pH to obtain a pretreatment solution;

(2) Immerse the waste fabric into the pretreatment liquid, mix, heat treat, wash and dry to obtain activated fabric;

(3) The activated fabric is subjected to efficient electrocatalytic treatment. After the electrolysis is completed, the electrolyte is post-processed to obtain recycled dye.

Preferably, the neutral mannanase concentration in step (1) is 1 to 20% (owf), and the enzyme activity is 20 to 50 U/mg; the auxiliary chemical reagents include potassium salts and/or calcium salts, and stable metal ions. Ligand complexing agent; adjust pH to 7-10.

Preferably, the ligand complexing agent that stabilizes metal ions includes sodium gluconate; potassium salt in the pretreatment liquid is 5 to 50 mmol/L and/or calcium salt is 5 to 50 mmol/L. The ligand complexing agent that stabilizes metal ions is It is 5~100mmol/L.

Preferably, the bath ratio (mass ratio) of waste fabrics and pretreatment liquid in step (2) is 1:10-25; the heat treatment temperature is 40-65°C, and the processing time is 15-60 minutes; the waste fabrics The dyes used for dyeing include one or more of indigo dyes, vat dyes, and sulfur dyes; the waste fabric is waste denim.

Preferably, the electrocatalytic treatment in step (3) includes: adding the activated fabric into the cathode electrolyzer under protective gas protection, performing constant voltage electrolysis at room temperature, and after the electrolysis is completed, the waste fabric (such as Waste denim) is taken out, and the decolored fabric (such as denim) is obtained after sufficient washing and drying; the electrolysis voltage is 1 to 15V, and the electrolysis time is 30 to 200 minutes.

Preferably, the protective gas is nitrogen or argon.

Preferably, the bath ratio (mass ratio) of waste fabric and catholyte in step (3) is 1:20-50.

Preferably, the system used in the electrocatalytic treatment in step (3) includes catholyte, anolyte, cathode, anode, and separator;

Preferably, the anolyte includes an auxiliary electrolyte and an alkali solution; the content of the auxiliary electrolyte is 0.05 to 0.4 mol/L, and the content of the alkali solution is 0.5 to 1 mol/L; and the auxiliary electrolyte includes sodium sulfate and sodium chloride. At least one, the lye includes sodium hydroxide;

Further, the anolyte is added to the alkali solution and stirred evenly to obtain the anolyte;

Further, the sodium sulfate content in the anolyte is 0.05-0.2 mol/L and/or the sodium chloride content is 0.1-0.4 mol/L, and the sodium hydroxide content is 0.5-1 mol/L.

Preferably, the catholyte includes an aqueous solution of caustic soda (caustic soda is dissolved in distilled water and stirred evenly), with a pH of 11 to 14;

Preferably, the cathode electrode includes a molybdenum disulfide-based catalytic electrode based on carbon felt;

Preferably, the anode electrode includes at least one of a graphite electrode and a stainless steel electrode;

Preferably, the membrane includes at least one of Nafion-117 and Nafion-324 proton exchange membranes.

Preferably, the post-processing in step (3): the catholyte is fully oxidized, flocculated, filtered, and dried to complete the recovery of the dye; the amount of oxidant used for oxidation is 5-15g/L; the amount of flocculant used for flocculation is 2～10g/L; the oxidant includes hydrogen peroxide (such as using hydrogen peroxide with a mass concentration of 30%); the flocculant includes alum;

Preferably, the oxidation includes: oxidizing with an oxidant at 30°C for 30-60 minutes; the flocculation includes: adjusting the pH of the dye liquor to 5.5-7.5 with glacial acetic acid, adding the flocculant to the fully oxidized catholyte, and quickly Stir evenly and then let it stand for 1 to 3 hours; Filtration: Pour the flocculated catholyte into a filter funnel for suction filtration; Drying: Dry the dye filter cake after suction filtration at 80 to 105°C for 2 to 6 Hour.

The invention provides a pre-reduction liquid based on recycled dye. The pre-reduction liquid is: under the protection of protective gas, the recycled dye obtained by the method is added into a cathode electrolytic tank, and constant voltage electrolysis is performed to obtain a dye pre-reduction liquid. .

Preferably, the recycled dye includes at least one of indigo dye, vat dye, and sulfur dye; the dye concentration is 0.005 to 0.025 mol/L;

Preferably, during the constant voltage electrolysis process, the electrolysis voltage is 1 to 15 V, and the electrolysis time is 30 to 180 minutes;

Preferably, the constant voltage electrolysis system includes catholyte, anolyte, cathode, anode, and separator;

The anolyte includes an auxiliary electrolyte and an alkali solution; the content of the auxiliary electrolyte is 0.05~0.4mol/L, and the content of the alkali solution is 0.5~1mol/L; the auxiliary electrolyte includes at least one of sodium sulfate and sodium chloride. , lye includes sodium hydroxide;

Preferably, the catholyte includes an aqueous solution of caustic soda, with a pH of 11 to 14;

Preferably, the cathode electrode includes a molybdenum disulfide-based catalytic electrode based on carbon felt;

Preferably, the anode electrode includes at least one of a graphite electrode and a stainless steel electrode;

Preferably, the membrane includes at least one of Nafion-117 and Nafion-324 proton exchange membranes.

Further, the preparation of molybdenum disulfide-based catalytic electrodes based on carbon felt includes:

The carbon felt material is subjected to impurity removal, hydrophilic treatment, washing, and drying to obtain a pretreated carbon felt material; then, ammonium molybdate tetrahydrate, thiourea, and a solvent are mixed to obtain a mixed solution. The pretreated carbon felt material The material is put into the mixed solution, subjected to hydrothermal reaction, washed, and vacuum dried to obtain molybdenum disulfide-carbon felt electrode material; the mass ratio of ammonium molybdate tetrahydrate to deionized water is 1:50 to 1:150; sulfur The mass ratio of urea to deionized water is 1:15~1:30; the solvent is a mixed solvent of N,N-dimethylformamide (DMF) and deionized water; the mass ratio of DMF to deionized water is 1: 4~1:16. The hydrothermal reaction conditions are 180 to 240°C for 3 to 8 hours. The vacuum drying conditions are: drying at 50-80°C for 6-12 hours. The mass ratio of the carbon felt material area to the water in the mixed solution is 0.1cm ^{2 /} g ~ 0.3cm ² /g.

The pretreated carbon felt material: first soak the carbon felt material in an acetone solution for 5 to 8 hours to remove surface impurities; then rinse it with deionized water and dry it, and further put the carbon felt material into the mass. In 10% dilute acid, perform hydrophilic treatment at 60-100°C for 2-6 hours, then rinse with deionized water and dry.

The invention provides an application of the pre-reduction liquid in fabric dyeing. For example, dyeing specifically includes: immersing the fabric (denim fabric) previously moistened with distilled water into the dye pre-reduction liquid for dyeing for 1 to 30 minutes. After completion, the post-dyeing treatment is completed through ventilated oxidation, soap boiling and water washing. The specific dyeing bath ratio is 1:5 to 100.

The present invention proposes an efficient and environmentally friendly method for recycling dyes in waste fabrics (denim). The proposed method can greatly improve the recycling efficiency of waste fabrics (denim) and realize the reuse of waste fabrics (denim) and dyes. It has extremely high economic benefits and can save a lot of resources.

beneficial effects

The present invention uses a green and environmentally friendly mannanase enzymatic hydrolysis system to activate and pretreat waste denim. Neutral mannanase and alkali metal complexes can swell the cellulose and hemicellulose on the surface of waste fabrics such as waste denim. At the same time, alkali metals have an activating effect on mannanase and carbonyl groups in dyes on waste fabrics such as waste denim, which is more conducive to the separation of fibers and dyes in the next step. Using electrocatalytic hydrogenation reduction technology, waste fabrics such as waste denim are added to the cathode electrolyzer for electrolysis. The active hydrogen generated in situ on the cathode electrode by electrolyzed water reduces the vat dye on waste fabrics such as waste denim into soluble leuco bodies. , thereby being desorbed from fabrics such as denim, and further transformed into water-insoluble dye through full oxidation. After flocculation, filtration, and drying, the dye can be recovered. Among them, the molybdenum disulfide-based carbon felt catalytic electrode with low price, large specific surface area and excellent conductivity is used as the cathode material for the electrocatalytic electrolysis recycling of waste fabrics such as waste denim. The difference between the active sites between metals and non-metals in the catalytic electrode The qualitative and synergistic effects can greatly promote its adsorption of active hydrogen and dyes, thereby promoting the hydrogenation and reduction of dyes and improving decolorization efficiency.

Compared with the traditional chemical decolorization process, the method of the present invention for recycling dyes in waste fabrics such as waste denim does not destroy the dye structure. After the dye is recovered, a pre-reducing liquid is further prepared through electrocatalytic hydrogenation and reduction, thereby realizing the recycling of the dye, and the decolorized Waste fabrics such as waste denim have less performance damage and can achieve secondary reuse. The present invention avoids the use of reversible redox media in traditional indirect electrochemical reduction and decolorization. It consumes less chemical reagents, has a short treatment process, simple operation methods, and can be recycled It has high efficiency, can significantly reduce energy consumption and environmental pollution, and also reduces the overall cost of production. It is easy to realize industrial production and has good application prospects.

Description of drawings

Figure 1 is the infrared spectrum of the indigo dye recovered in Example 1 and the standard indigo dye;

In Figure 2, (a) is the appearance of the waste denim without recycling; (b) is the appearance of the treated denim in Example 1 of the present invention; (c) is the appearance of the comparative example 1. The appearance picture; (d) is the appearance picture after processing of Comparative Example 2;

Figure 3 (a) shows the appearance of the denim fabric after being dyed with the recycled dye electrocatalytic pre-reduction solution after being treated in Example 1; (b) is the appearance of the denim fabric after being dyed with the cathode reduction solution after being treated in Comparative Example 2. Appearance picture;

Figure 4 is a diagram of the redox potential and dye reduction rate of the catholyte during the high-efficiency electrocatalytic recovery and treatment of waste indigo jeans in Example 1.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the invention and are not intended to limit the scope of the invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Source of raw materials

Neutral mannanase, enzyme activity (30U/mg) (Shanghai McLean Biochemical Technology Co., Ltd.)

The specific preparation method of molybdenum disulfide-carbon felt material (made in the laboratory) is: 1). First soak the 2cm×2cm carbon felt material in acetone solution for 8 hours to remove surface impurities; then rinse with deionized water drying. The carbon felt material was further put into a dilute acid with a mass fraction of 10% for hydrophilic treatment at 80°C for 2 hours, and then rinsed with deionized water and dried. 2). Preparation of molybdenum disulfide-carbon felt material: Dissolve 0.175g ammonium molybdate tetrahydrate and 0.91g thiourea in a mixed solvent containing 5g DMF and 25g water. After complete dissolution, transfer to the polytetrafluoroethylene lining. Place the pretreated carbon felt into a polytetrafluoroethylene lining, transfer the polytetrafluoroethylene lining to a stainless steel autoclave, and react at 240°C for 3 hours. After the reaction, the electrode material was fully washed with water and ethanol, and then vacuum dried at 50°C for 10 hours to obtain the final molybdenum disulfide-carbon felt electrode material.

Graphite electrodes and carbon felt electrodes (Beijing Jinglong Special Carbon Technology Co., Ltd.)

Test Methods:

Decolorization rate: Use Color-i5 color measurement and matching instrument (American X-Rite Company) to measure the K/S value of waste denim before and after treatment, and use Formula 1 to calculate the decolorization rate.

In formula (1), K/S ₀ is the K/S value of the waste denim fabric before treatment, and K/S ₁ is the K/S value after recycling.

Strength retention rate: Use the YG365 universal strength machine to test the breaking strength of waste denim before and after treatment, and use Formula 2 to calculate the strength retention rate.

Reduction potential ORP: Refer to the industry standard SL94-1994 redox potential measurement method, use a redox potentiometer, put the reduction potentiometer into the dye solution at room temperature, and read the reduction potential value after the value is stable.

Dye conversion rate (reduction rate RE): Weigh the dye and dissolve it in 1.0M caustic soda solution at the concentrations of 1g/L, 2g/L, 3g/L, 4g/L and 5g/L, and then use excess insurance powder or vulcanization Sodium reduces the dye to its leuco form. Use a Cary60 UV spectrophotometer to determine the maximum absorption wavelength of the dye leucobody, and draw a concentration and absorbance standard curve. Put the UV spectrophotometer probe into the catholyte after electrocatalytic reduction, test its absorbance, and calculate the dye conversion rate based on the absorbance. K/S value: Fold the sample into 4 layers (opaque) and test it with a colorimeter. Measure 3 different positions and take the average.

Example 1

A method for recycling dyes in waste indigo denim, which includes the following steps:

(1) Dissolve 15% (owf) neutral mannanase (enzyme activity 30U/mg), 1mmol calcium chloride and 2mmol sodium gluconate in 100mL deionized water, stir well, and then use sodium hydroxide to dissolve the above The pH of the solution was adjusted to 9.

(2) Immerse 5g of waste indigo denim into the pretreatment liquid, mix evenly, heat treat at 60°C for 15 minutes, and then wash and dry to obtain activated denim.

(3) The activated denim is subjected to high-efficiency electrocatalytic recycling. Specifically, molybdenum disulfide-carbon felt material is used as the cathode catalytic electrode, the graphite electrode is the anode, and the separator is a Nafion-117 proton exchange membrane. The anolyte (100mL) consists of 0.5mol/L sodium hydroxide and 0.1mol/L sodium sulfate; the catholyte (100mL) is adjusted to pH 12 with caustic soda. Under nitrogen protection, the activated denim is added to In the cathode electrolytic cell, perform constant voltage (3V) electrolysis at room temperature for 60 minutes. During this period, the dye solution reduction potential and dye reduction rate in the cathode electrolyte are tested. After the electrolysis is completed, the waste denim is taken out, washed and dried thoroughly to obtain the decolorized result. of denim, tested for discoloration and strong retention. At the same time, add 0.5g hydrogen peroxide to the catholyte and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with glacial acetic acid, then add 0.5g alum, stir thoroughly, and let it stand for 2 hours. Finally, flocculate the The catholyte is suction filtered, and the obtained filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

(4) Perform electrocatalytic hydrogenation reduction of the recovered indigo dye to prepare a pre-reduction solution. Specifically, molybdenum disulfide-carbon felt material is used as the cathode catalytic electrode, the graphite electrode is the anode, and the separator is a Nafion-117 proton exchange membrane. The anolyte (100 mL) consists of 0.5 mol/L sodium hydroxide and 0.1 mol/L sodium sulfate; the catholyte (100 mL) is adjusted to pH 12 with caustic soda. Under nitrogen protection, the recovered dye is added to the cathode. In the electrolytic cell, perform electrolysis at a constant voltage (6V) for 30 minutes, and test the redox potential and dye reduction rate of the catholyte after electrolysis.

(5) Further immerse the denim fabric (5g) previously moistened with distilled water into the above dye pre-reduction solution for dyeing for 1 minute. After the dyeing is completed, the post-dying treatment is completed through air oxidation, soaping and water washing, and the final fabric is tested. Obtain color depth K/S value.

Example 2

A method for recycling dyes in waste indigo denim, which includes the following steps:

(1) Dissolve 10% (owf) neutral mannanase (enzyme activity 30U/mg), 1mmol calcium chloride and 2mmol sodium gluconate in 100mL deionized water, stir well, and then use sodium hydroxide to dissolve the above The pH of the solution was adjusted to 9.

(2) Immerse 5g of waste indigo denim into the pretreatment liquid, mix evenly, heat treat at 60°C for 15 minutes, and then wash and dry to obtain activated denim.

(3) The activated denim is subjected to high-efficiency electrocatalytic recycling. Specifically, molybdenum disulfide-carbon felt material is used as the cathode catalytic electrode, the graphite electrode is the anode, and the separator is a Nafion-117 proton exchange membrane. The anolyte (100 mL) consists of 0.5 mol/L sodium hydroxide and 0.1 mol/L sodium sulfate; the catholyte (100 mL) is adjusted to pH 12 with caustic soda. Under nitrogen protection, the activated denim is added to In the cathode electrolytic cell, perform constant voltage (3V) electrolysis at room temperature for 60 minutes. During this period, the dye solution reduction potential and dye reduction rate in the cathode electrolyte are tested. After the electrolysis is completed, the waste denim is taken out, washed and dried thoroughly to obtain the decolorized result. of denim, tested for discoloration and strong retention. At the same time, add 0.5g hydrogen peroxide to the catholyte and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with glacial acetic acid, then add 0.5g alum, stir thoroughly, and let it stand for 2 hours. Finally, flocculate the The catholyte is suction filtered, and the obtained filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

Example 3

A method for recycling dyes in waste indigo denim, which includes the following steps:

The waste indigo denim is subjected to efficient electrocatalytic recycling. Specifically, molybdenum disulfide-carbon felt material is used as the cathode catalytic electrode, the graphite electrode is the anode, and the separator is a Nafion-117 proton exchange membrane. The anolyte (100mL) consists of 0.5mol/L sodium hydroxide and 0.1mol/L sodium sulfate; the catholyte (100mL) is adjusted to pH 12 with caustic soda. Under nitrogen protection, waste indigo denim is added to the cathode electrolysis In the tank, perform constant voltage (3V) electrolysis at room temperature for 60 minutes. During this period, the reduction potential and dye reduction rate of the dye solution in the catholyte are tested. After the electrolysis is completed, the waste denim is taken out, and the decolorized denim is obtained after sufficient washing and drying. cloth to test the decolorization rate and strong retention rate. At the same time, add 0.5g hydrogen peroxide to the catholyte and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with glacial acetic acid, then add 0.5g alum, stir thoroughly, and let it stand for 2 hours. Finally, flocculate the The catholyte is suction filtered, and the obtained filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

Example 4

A method for recycling dyes in waste indigo denim, which includes the following steps:

(1) Dissolve 15% (owf) neutral mannanase (enzyme activity 30U/mg), 1mmol calcium chloride and 2mmol sodium gluconate in 100mL deionized water, stir well, and then use sodium hydroxide to dissolve the above The pH of the solution was adjusted to 9.

(2) Immerse 5g of waste indigo denim into the pretreatment liquid, mix evenly, heat treat at 60°C for 15 minutes, and then wash and dry to obtain activated denim.

(3) The activated denim is subjected to high-efficiency electrocatalytic recycling. Specifically, the carbon felt electrode is used as the cathode, the graphite electrode is used as the anode, and the separator is a Nafion-117 proton exchange membrane. The anolyte (100 mL) consists of 0.5 mol/L sodium hydroxide and 0.1 mol/L sodium sulfate; the catholyte (100 mL) is adjusted to pH 12 with caustic soda. Under nitrogen protection, the activated denim is added to In the cathode electrolytic cell, perform constant voltage (3V) electrolysis at room temperature for 60 minutes. During this period, the dye solution reduction potential and dye reduction rate in the cathode electrolyte are tested. After the electrolysis is completed, the waste denim is taken out, washed and dried thoroughly to obtain the decolorized result. of denim, tested for discoloration and strong retention. At the same time, add 0.5g hydrogen peroxide to the catholyte and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with glacial acetic acid, then add 0.5g alum, stir thoroughly, and let it stand for 2 hours. Finally, flocculate the The catholyte is suction filtered, and the obtained filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

(4) Perform electrocatalytic hydrogenation reduction of the recovered indigo dye to prepare a pre-reduction solution. Specifically, molybdenum disulfide-carbon felt material is used as the cathode catalytic electrode, the graphite electrode is the anode, and the separator is a Nafion-117 proton exchange membrane. The composition of the anolyte (100mL) is 0.5mol/L sodium hydroxide and 0.1mol/L sodium sulfate; the catholyte (100mL) is adjusted to pH 12 with caustic soda. Under nitrogen protection, the recovered dye is added to the cathode electrolysis In the tank, perform electrolysis at constant voltage (6V) for 30 minutes, and test the redox potential and dye reduction rate of the catholyte after electrolysis. .

(5) Further immerse the denim fabric (5g) previously moistened with distilled water into the above dye pre-reduction solution for dyeing for 1 minute. After the dyeing is completed, the post-dying treatment is completed through air oxidation, soaping and water washing, and the final fabric is tested. Obtain color depth K/S value.

Example 5

A method for recycling dyes in waste indigo denim, which includes the following steps:

(1) Dissolve 15% (owf) neutral mannanase (enzyme activity 30U/mg), 1mmol calcium chloride and 2mmol sodium gluconate in 100mL deionized water, stir well, and then use sodium hydroxide to dissolve the above The pH of the solution was adjusted to 9.

(2) Immerse 5g of waste indigo denim into the pretreatment solution, mix evenly, and heat-treat at 60°C for 15 minutes for decolorization. After decolorization, wash and dry to obtain decolorized denim. Test the decolorization rate and strong retention rate. At the same time, add 0.5g hydrogen peroxide to the stripping treatment liquid and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with alkali solution, then add 0.5g alum, stir thoroughly, let it stand for 2 hours, and finally perform suction filtration to obtain The filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

Comparative example 1

A method for enzymatic washing and decolorization of waste indigo denim, which includes the following steps:

According to the bath ratio of 1:10, immerse the indigo denim in a buffer with a pH of 4.5 (composed of acetic acid, sodium acetate, and penetrating agent JFC, with a mass ratio of 10:5:1), and then add a concentration of 3% (owf ) cellulase, stir for 5 minutes and mix evenly to obtain a mixture; then, the mixture is heated to 60°C at a heating rate of 2°C/min, and kept for 60 minutes to decolorize. After decolorization is completed, wash and dry to obtain decolorized denim. cloth to test the decolorization rate and strong retention rate. At the same time, add 0.5g hydrogen peroxide to the stripping treatment liquid and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with alkali solution, then add 0.5g alum, stir thoroughly, let it stand for 2 hours, and finally perform suction filtration to obtain The filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

Comparative example 2

A method for recycling dyes in waste indigo denim, which includes the following steps:

(1) Prepare 100ml of 0.1mol/L citric acid solution, and add cellulase to the citric acid solution so that the concentration of cellulase is 1g/L;

(2) Place 5g of waste denim in a citric acid solution containing cellulase and soak it at 40°C for 30 minutes;

(3) The waste denim soaked in citric acid solution is electrolytically recycled. The details are as follows: the cathode electrode material and the anode electrode material are both nickel mesh, the separator is Nafion-117 proton exchange membrane, and the anolyte (100mL) is 40g /L sodium hydroxide, the catholyte (100mL) is 15g/L ferric sulfate, 30g/L triethanolamine, 21.5g/L sodium hydroxide, 1g/L indigo, 1.5g/L insurance powder, which will be passed through the citric acid solution The soaked waste denim is immersed in a cathode electrolytic tank for constant current electrolysis, where the electrolysis current is 1A, the electrolysis time is 30 minutes, and the electrolysis temperature is 60°C. After the electrolysis is completed, the waste denim is taken out, and the decolored denim is obtained after sufficient washing and drying. Test decolorization rate and strong retention rate. At the same time, the denim fabric (5g) previously moistened with distilled water was immersed in the catholyte for dyeing for 1 minute. After the dyeing was completed, it was subjected to ventilation oxidation, soap boiling and water washing to complete the post-dyeing treatment, and the color depth K/ of the final fabric was tested. S value. Finally, add 0.5g hydrogen peroxide to the catholyte and fully oxidize it at 30°C for 45 minutes. Further, adjust the pH to 7.5 with glacial acetic acid, then add 0.5g alum, stir thoroughly, and let it stand for 2 hours. Finally, flocculate the The catholyte is suction filtered, and the obtained filter cake is dried at 105°C, and finally the recovered indigo dye is obtained.

The specifications of the waste indigo denim used in the embodiment are: warp and weft yarn count 6s×10s, warp density 237 threads/10cm, weft density 178 threads/10cm, fabric weave 3/1 right bias, extra dark blue, width 150 /155cm (Guangdong Qianjin Denim Co., Ltd.).

Table 1 Dyeing K/S value and breaking strength of waste indigo denim before and after treatment under different embodiments

Figure 1 shows the infrared spectra of the indigo dye recovered in Example 1 and the standard indigo dye. It can be seen that the infrared spectra of the indigo dye recovered through the treatment in Example 1 of the present invention and the standard indigo dye are basically consistent. Figure 4 shows the redox potential and dye reduction rate of the catholyte during the high-efficiency electrocatalytic recovery and treatment of waste indigo jeans in Example 1. It can be seen that as the electrolysis process proceeds, the absolute value of the reduction potential of the dye solution gradually increases. When the leuco body potential of the indigo dye is reached, the indigo dye on the waste denim is gradually reduced to the dye leuco body, which further forms a soluble leuco body sodium salt with the sodium ions in the electrolyte and is desorbed from the denim.

The dyeing K/S value and breaking strength of waste indigo denim before and after recycling under different embodiments are shown in Table 1. The K/S value of the waste indigo denim used in each embodiment before treatment is 18.7532, and the breaking strength is 1319.8. N. The quality, decolorization rate and strong retention rate of the indigo dye recovered under different embodiments are shown in Table 2.

Examples 1, 2, and 3 compare the effects of neutral mannanase on the decolorization and recycling of waste denim dyes. It can be seen that after the waste denim is activated and pretreated by the mannanase enzymatic hydrolysis system, the dye The recovery efficiency and decolorization rate are higher. The neutral mannanase and the alkali metal complex can swell the cellulose and hemicellulose on the surface of the waste denim and loosen the fibers. At the same time, the alkali metal can bind to the mannanase and the waste denim. The carbonyl group in the dye has an activating effect, which is more conducive to the separation of fiber and dye in the next step, so it can greatly improve the dye recovery efficiency. Examples 1, 3, and 5 compare the synergistic effects of mannan enzymatic activation pretreatment and molybdenum disulfide-carbon felt electrocatalytic reduction on the decolorization and recycling of waste denim dyes. It can be seen that the present invention can be used alone The effect of mannanase enzymatic decolorization and the single use of molybdenum disulfide-carbon felt electrocatalytic reduction decolorization is far less effective than the simultaneous simultaneous treatment of the two. Their synergistic effect can achieve efficient recovery of dyes in waste denim.

Examples 1 and 4 compare the effects of molybdenum disulfide-carbon felt catalytic electrodes and ordinary carbon felt electrodes on electrochemical decolorization and recycling. It can be seen that loading molybdenum disulfide catalyst on the carbon felt can greatly improve the quality of waste indigo denim. The decolorization efficiency of dyes is due to the excellent conductivity of the nanometallic molybdenum disulfide catalyst, which can greatly improve the electron mobility and ion diffusion rate on the electrode surface. In addition, its higher specific surface area shortens the ion diffusion path, as The cathode material recycled by electrocatalytic electrolysis of waste denim can greatly promote its adsorption of active hydrogen and dyes, thereby improving the efficiency of dye recovery.

In addition, it can be seen from Figure 2, Table 1 and Table 2 that the high-efficiency electrocatalytic recovery and treatment method of dyes in waste denim of the present invention is better than the traditional chemical enzyme elution and color recovery treatment method (Comparative Example 1) and indirect electrochemical decolorization and recovery. The treatment method (Comparative Example 2) recovers a large amount of dye, has a high decolorization rate and strong retention, and uses less chemical reagents to achieve a decolorization rate of more than 90%. At the same time, the strong retention rate is high and can meet the requirements of denim fabrics. As for the requirements for decolorization and finishing, it can be seen from Figure 3 that the denim fabric is darker in color after being dyed with the recycled dye electrocatalytic pre-reduction solution after treatment by the present invention. The K/S is 15.7545, which can reach 84.01% of the original dyeing depth, achieving secondary reuse. The invention can significantly reduce energy consumption and environmental pollution, and at the same time reduce the overall cost of production. It is easy to realize industrial production and has good application prospects.

Table 2 The quality, decolorization rate and strong retention rate of indigo dye recovered under different embodiments

sample Recycled dye mass/mg Decolorization rate/% Strong retention rate/% Example 1 189.5 95.27 93.16 Example 2 166.3 92.15 93.39 Example 3 50.1 68.28 95.45 Example 4 66.7 72.46 94.23 Example 5 36.6 50.12 96.72 Comparative example 1 33.2 56.49 85.52 Comparative example 2 100.4 82.13 89.68

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. A method for recycling dye in waste fabric comprises the following steps:

(1) Uniformly mixing neutral mannase, an auxiliary chemical reagent and water, and then regulating pH to obtain a pretreatment liquid;

(2) Immersing the waste fabric into the pretreatment liquid, uniformly mixing, carrying out heat treatment, washing and drying to obtain activated fabric;

(3) And (3) carrying out electrocatalytic treatment on the activated fabric, and carrying out aftertreatment on electrolyte after the electrolysis is finished to obtain the recovered dye.

2. The method according to claim 1, wherein the concentration of neutral mannanase in step (1) is 1-20% (owf), and the enzyme activity is 20-50U/mg; auxiliary chemical reagents comprise potassium salt and/or calcium salt, and ligand complexing agents for stabilizing metal ions; the pH is regulated to 7-10.

3. The method of claim 2, wherein the ligand-complexing agent for stabilizing the metal ion comprises sodium gluconate; 5-50 mmol/L of potassium salt and/or 5-50 mmol/L of calcium salt in the pretreatment liquid, and 5-100 mmol/L of ligand complexing agent for stabilizing metal ions.

4. The method of claim 1, wherein the waste cloth and pretreatment liquid bath ratio in step (2) is 1:10 to 25; the heat treatment temperature is 40-65 ℃ and the treatment time is 15-60 min; the dye for dyeing the waste fabric comprises one or more of indigo dye, vat dye and sulfur dye; the waste fabric is waste jean.

5. The method of claim 1, wherein the electrocatalytic treatment in step (3) comprises: under the protection of protective gas, adding the activated fabric into a cathode electrolytic tank, and carrying out constant voltage electrolysis at room temperature;

wherein the electrolysis voltage is 1-15V, and the electrolysis time is 30-200 min; the bath ratio of the waste fabric to the catholyte is 1: 20-50; and taking out the waste fabric after the electrolysis is finished, and obtaining the decolored fabric.

6. The method of claim 1, wherein the system used for the electrocatalytic treatment in step (3) comprises a catholyte, an anolyte, a cathode, an anode, a membrane;

wherein the anolyte comprises auxiliary electrolyte and alkali liquor; wherein the content of the auxiliary electrolyte is 0.05-0.4 mol/L, and the content of the alkali liquor is 0.5-1 mol/L; wherein the auxiliary electrolyte comprises at least one of sodium sulfate and sodium chloride, and the alkali liquor comprises sodium hydroxide;

the catholyte comprises aqueous solution of caustic soda, and the pH value is 11-14;

the cathode electrode comprises a molybdenum disulfide-based catalytic electrode taking a carbon felt as a substrate;

the anode electrode comprises at least one of a graphite electrode and a stainless steel electrode;

the membrane comprises at least one of Nafion-117 and Nafion-324 proton exchange membranes.

7. The method of claim 1, wherein the post-treatment in step (3): the catholyte is oxidized, flocculated, filtered and dried to complete the recovery of dye; wherein the dosage of the oxidant adopted in the oxidation is 5-15g/L; the dosage of the flocculant adopted by flocculation is 2-10 g/L; wherein the oxidant comprises hydrogen peroxide; the flocculant comprises alum;

wherein the oxidizing comprises: oxidizing the oxidant at 30 ℃ for 30-60min; flocculation includes: adjusting pH of the dye liquor to 5.5-7.5 by glacial acetic acid, adding a flocculating agent into the oxidized catholyte, uniformly stirring, and standing for 1-3 hours; filtering comprises the steps of carrying out suction filtration on the flocculated catholyte; drying comprises the following steps: drying the dye filter cake after suction filtration for 2-6 hours at the temperature of 80-105 ℃.

8. A pre-reduction solution based on recovered dye, characterized in that it: under the protection of protective gas, the recovered dye obtained by the method of claim 1 is added into a cathode electrolytic tank for constant voltage electrolysis to obtain dye pre-reduction liquid.

9. The pre-vat liquid of claim 8, wherein said recovery dye comprises at least one of an indigo dye, a vat dye, a sulphur dye; the dye concentration is 0.005-0.025 mol/L;

the voltage is 1-15V in the constant voltage electrolysis process, and the electrolysis time is 30-180 min;

the constant-voltage electrolysis system comprises a catholyte, an anolyte, a cathode, an anode and a diaphragm;

wherein the anolyte comprises auxiliary electrolyte and alkali liquor; wherein the content of the auxiliary electrolyte is 0.05-0.4 mol/L, and the content of the alkali liquor is 0.5-1 mol/L; wherein the auxiliary electrolyte comprises at least one of sodium sulfate and sodium chloride, and the alkali liquor comprises sodium hydroxide;

the catholyte comprises aqueous solution of caustic soda, and the pH value is 11-14;

the cathode electrode comprises a molybdenum disulfide-based catalytic electrode taking a carbon felt as a substrate;

the anode electrode comprises at least one of a graphite electrode and a stainless steel electrode;

the membrane comprises at least one of Nafion-117 and Nafion-324 proton exchange membranes.

10. Use of the pre-reduction solution of claim 8 for dyeing fabrics.