Electrochemical bleaching and dyeing method and system

Abstract

The invention discloses an electrochemical bleaching and dyeing method and system. The method comprises the steps that the fabric enters an electrochemical device to be subjected to electrochemical bleaching, electrolyte is contained in the electrochemical device, and after bleaching is completed, the bleached fabric and bleaching wastewater are obtained; the pH value of the bleaching wastewater is adjusted to be acidic, air is blown in for dechlorination, and after dechlorination is completed, dechlorinated wastewater and chlorine-containing waste gas are obtained; the pH value of the dechlorinated wastewater is adjusted to be neutral, then dye and alkali are added for dyeing, and after dyeing is completed, dyed fabric and dyeing wastewater are obtained; the dyeing wastewater is used for absorbing residual chlorine in the chlorine-containing waste gas, and dischargeable tail gas and the dyeing wastewater absorbing the residual chlorine are obtained; and taking the dyeing wastewater absorbing the residual chlorine as an electrolyte in an electrochemical device. The method can solve the problem of wastewater discharge and treatment in the bleaching and dyeing process of the fabric, and meanwhile, has a better dyeing effect.

Description

Technical Field

[0001] The invention belongs to the technical field of textile printing and dyeing, and particularly relates to an electrochemical bleaching and dyeing method and system. Background Art

[0002] A large amount of wastewater is generated during the bleaching and dyeing process of cotton and linen fabrics. These wastewaters have the characteristics of high chroma, high COD, high salt, etc., which cause great pollution to the environment. Therefore, a process is needed to significantly reduce the pollutant emissions during the bleaching and dyeing process. The current cold pile bleaching and dyeing process still has a large gap in bleaching and dyeing effects compared with traditional reactive dyeing, and is not widely used.

[0003] Therefore, how to solve the wastewater discharge and treatment problems in the bleaching and dyeing process of fabrics while taking into account a better dyeing effect has become one of the problems to be solved urgently in this field. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide an electrochemical bleaching and dyeing method and system. The present invention can solve the wastewater discharge and treatment problems in the bleaching and dyeing process of fabrics, while taking into account a better dyeing effect.

[0005] In order to achieve the above object, the first aspect of the present invention provides an electrochemical bleaching and dyeing method, which comprises the following steps:

[0006] (1) placing the fabric into an electrochemical device for electrochemical bleaching, wherein the electrochemical device contains an electrolyte, and after the bleaching is completed, a bleached fabric and bleaching wastewater are obtained;

[0007] (2) adjusting the pH value of the bleaching wastewater in the electrochemical device to acidic and blowing air into it for dechlorination, and after the dechlorination is completed, obtaining dechlorinated wastewater and chlorine-containing waste gas;

[0008] (3) adjusting the pH value of the dechlorinated wastewater in the electrochemical device to neutral, then adding dye and alkali for dyeing, and after the dyeing is completed, obtaining dyed fabric and dyeing wastewater;

[0009] (4) using the dyeing wastewater obtained in step (3) to absorb the residual chlorine in the chlorine-containing waste gas obtained in step (2) to obtain dyeing wastewater that can discharge tail gas and absorb the residual chlorine; and using the dyeing wastewater after absorbing the residual chlorine as the electrolyte in the electrochemical device in step (1).

[0010] According to a specific embodiment of the present invention, preferably, in step (1), the fabric entering the electrochemical device comprises scour cotton and / or linen fabric.

[0011] According to a specific embodiment of the present invention, preferably, in step (1), the electrochemical device includes an electrolytic cell, an anode, and a cathode, and there is an electrolyte in the electrolytic cell; the electrolytic voltage for the electrochemical bleaching is 2 - 30 V, the current is 1 - 10000 A, the operating temperature is room temperature (generally 20 - 30 °C), and the treatment time is 1 - 600 min. More preferably, the electrolytic cell is a diaphragmless electrolytic cell. More preferably, the anode includes a metal oxide electrode, a glassy carbon electrode, a platinum electrode, a graphite electrode, or a BDD electrode, etc., and the cathode includes a pure metal electrode, a carbon material electrode, or an alloy electrode, etc. Among them, the pure metal electrode can include, for example, a copper, lead, zinc, titanium, or stainless steel electrode, etc. The proportional relationship between the amount of the electrolyte and the fabric can be adjusted conventionally by those skilled in the art as long as the fabric is completely immersed in the electrolyte.

[0012] According to a specific embodiment of the present invention, preferably, in step (1), the whiteness of the bleached fabric is 65.0 - 85.0.

[0013] According to a specific embodiment of the present invention, preferably, in step (1), the residual chlorine concentration of the bleaching wastewater is 0.1 - 3 g / L, and the chromaticity is 4 - 32 times.

[0014] According to a specific embodiment of the present invention, preferably, in step (2), adjusting the pH value of the bleaching wastewater in the electrochemical device to acidic means adjusting the pH value to 1.0 - 4.0. More preferably, the pH value of the bleaching wastewater is adjusted using an acid, such as hydrochloric acid and / or sulfuric acid, etc. In the present invention, the pH value of the bleaching wastewater is adjusted to acidic, and air is blown in for dechlorination. Under acidic conditions, hypochlorite ions are converted into chlorine gas and are blown off from the wastewater. If the pH value of the bleaching wastewater is not adjusted to acidic and air is directly blown in for dechlorination, then the hypochlorite ions will not be removed.

[0015] According to a specific embodiment of the present invention, preferably, in step (2), the volume ratio of the air blown in to the bleaching wastewater with the pH value adjusted to acidic is 5:1 - 100:1, and the time for blowing in air is 30 min - 8 h.

[0016] According to a specific embodiment of the present invention, preferably, in step (2), the residual chlorine concentration of the dechlorinated wastewater is 0.1 - 5 mg / L.

[0017] According to a specific embodiment of the present invention, preferably, in step (3), adjusting the pH value of the dechlorinated wastewater in the electrochemical device to neutral means adjusting the pH value to 6.0 - 7.0. More preferably, the pH value of the dechlorinated wastewater is adjusted using an alkali, such as sodium hydroxide. After adjusting the pH value of the dechlorinated wastewater to neutral in the present invention, adding a dye and an alkali for dyeing can protect the stability of the dye and avoid interference with dyeing during the acid-base neutralization process. If the pH value of the dechlorinated wastewater is not adjusted to neutral but directly adding a dye and an alkali for dyeing, it is likely to cause problems such as uneven dyeing and low dye utilization rate.

[0018] According to a specific embodiment of the present invention, preferably, in step (3), the alkali used for adding a dye and an alkali for dyeing includes a substitute alkali, etc. The dosage of the substitute alkali is 1 - 5 g / L, that is, based on 1 L of dechlorinated wastewater with a pH value adjusted to neutral, the addition amount of the substitute alkali is 1 - 5 g. The composition of the substitute alkali is a conventional component in the art, preferably including one or more of a phosphate system substitute alkali, a silicate system substitute alkali, and a carbonate system substitute alkali, etc. The dosage of the dye can be routinely adjusted by those skilled in the art.

[0019] According to a specific embodiment of the present invention, preferably, in step (3), the operating temperature of the dyeing is 45 - 80 °C, and the treatment time is 30 - 120 min.

[0020] According to a specific embodiment of the present invention, preferably, in step (4), using the dyed wastewater obtained in step (3) to absorb the residual chlorine in the chlorine-containing waste gas obtained in step (2) is carried out using a spray tower. The dyed wastewater is brought into contact with the chlorine-containing waste gas by spraying to absorb the residual chlorine therein, obtaining an exhaust gas that can be discharged and the dyed wastewater after absorbing the residual chlorine. In the present invention, the dyed wastewater is used to absorb the residual chlorine in the chlorine-containing waste gas by spraying. The residual chlorine in the chlorine-containing waste gas reacts with the dye in the dyed wastewater, and the spraying method can improve the mass transfer efficiency between the two, thereby removing most or even all of the residual chlorine in the chlorine-containing waste gas, realizing the safe discharge of the exhaust gas, and at the same time removing most of the dye in the dyed wastewater, which can reduce the load when it is used as an electrolyte for electrochemical bleaching.

[0021] According to a specific embodiment of the present invention, preferably, in step (4), the chlorine concentration of the exhaust gas that can be discharged is 0.5 mg / m 3 or less.

[0022] According to a specific embodiment of the present invention, preferably, in step (4), the pH value of the dyed wastewater after absorbing the residual chlorine is 8.0 - 11.0, more preferably 10.0 - 11.0, the sodium chloride concentration is 50 - 110 g / L, and the chromaticity is 32 - 400 times.

[0023] According to a specific embodiment of the present invention, preferably, the above method further includes step (5): subjecting the dyed fabric obtained in step (3) to soaping and color fixation to obtain a fabric after soaping and color fixation. The process of soaping and color fixation can be carried out in a conventional manner in the art, and the present invention does not specifically limit it. Soaping can be carried out first, and then color fixation; or soaping and color fixation can be carried out simultaneously.

[0024] The present invention uses dyeing wastewater as an electrolyte and bleaches the fabric electrochemically. During the bleaching process, the dyeing wastewater is electrolyzed to generate strongly oxidizing substances such as hypochlorite, chlorine gas, ozone, hydroxyl radicals, and chlorine radicals, thereby realizing the bleaching of the fabric without adding an external bleaching agent. After that, instead of draining the bleaching wastewater in the electrolytic cell, the pH value is directly adjusted to be acidic, and air is blown in for dechlorination. During the dechlorination process, the hypochlorite in the bleaching wastewater is converted into chlorine gas and blown off by the air to obtain dechlorinated wastewater and chlorine-containing waste gas. Then, the pH value of the dechlorinated wastewater in the electrolytic cell is adjusted to be neutral, and then the fabric is dyed by using reactive dyes, adding dyes and alkali for dyeing to obtain a dyed fabric and dyeing wastewater. The present invention uses dyeing wastewater to absorb the residual chlorine in the chlorine-containing waste gas. The residual chlorine in the chlorine-containing waste gas reacts with the dyes in the dyeing wastewater, so that most or even all of the residual chlorine in the chlorine-containing waste gas can be removed, realizing the safe emission of the tail gas. At the same time, most of the dyes in the dyeing wastewater can be removed, which can reduce the load during electrochemical bleaching as an electrolyte. Subsequently, the present invention uses the dyeing wastewater after absorbing residual chlorine as the electrolyte for electrochemical bleaching, realizing the recycling of the dyeing wastewater. At the same time, through the synergistic effect of the above steps of the present invention, and by further controlling the process conditions of the above steps within the above range, a better dyeing effect is also achieved.

[0025] The second aspect of the present invention provides an electrochemical dyeing and bleaching system for realizing the above electrochemical dyeing and bleaching method. The system includes: an electrochemical device, a residual chlorine absorption device, a chlorine-containing waste gas conveying pipeline, a dyeing wastewater conveying pipeline, and a conveying pipeline for the dyeing wastewater after absorbing residual chlorine;

[0026] Among them, the electrochemical device includes an electrolytic cell, an anode, and a cathode, and there is an electrolyte in the electrolytic cell; the electrochemical device is provided with an air blowing assembly; the electrochemical device is used for electrochemically bleaching, dechlorinating, neutralizing, and dyeing the fabric to obtain a dyed fabric; the electrochemical device is connected to the chlorine-containing waste gas conveying pipeline and the dyeing wastewater conveying pipeline;

[0027] The chlorine-containing waste gas conveying pipeline and the dyeing wastewater conveying pipeline are connected to the residual chlorine absorption device for enabling the dyeing wastewater to absorb the residual chlorine in the chlorine-containing waste gas to obtain an exhaust gas that can be discharged and the dyeing wastewater after absorbing residual chlorine;

[0028] The pipeline for transporting the dyed wastewater after chlorine absorption is connected to the chlorine absorption device and the electrolytic cell of the electrochemical device, and is used to transport the dyed wastewater after chlorine absorption into the electrochemical device as the electrolyte.

[0029] According to a specific embodiment of the present invention, preferably, the air injection assembly may include an air pipe and the like.

[0030] According to a specific embodiment of the present invention, preferably, the chlorine absorption device includes a spray tower, which is used to make the dyed wastewater contact with the chlorine-containing waste gas in a spray manner to absorb the residual chlorine therein.

[0031] According to a specific embodiment of the present invention, preferably, the above-mentioned electrochemical dyeing and bleaching system further includes: a soaping and fixing device, which is used to soap and fix the dyed fabric.

[0032] The present invention has at least the following beneficial effects:

[0033] The present invention solves the problems of wastewater discharge and treatment in the dyeing and bleaching process of fabrics, realizes the recycling of dyed wastewater, zero wastewater discharge, and does not require additional wastewater treatment processes; and the present invention realizes the simultaneous removal of residual chlorine in waste gas and dyes in wastewater, the tail gas can be safely discharged, and the use of wastewater for electrochemical bleaching can reduce the load; therefore, the present invention has a low operating cost and simple process operation. At the same time, the present invention also takes into account a good dyeing effect. Description of the Drawings

[0034] Figure 1 It is a process flow chart of the electrochemical dyeing and bleaching method in the embodiment. Specific Embodiments

[0035] In order to have a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will be described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0036] It should be noted that unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0037] All kinds of raw materials, reagents, instruments, and equipment used in the present invention, unless otherwise specifically stated, can be obtained through market purchase or can be prepared by existing methods.

[0038] It should be understood that the terms "comprising", "including", and / or "containing" when used herein specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0039] In the ranges disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0040] Test method:

[0041] pH value of the wastewater: Measured using a pH meter.

[0042] Sodium chloride concentration and residual chlorine concentration of the wastewater: The sodium chloride concentration is measured by the conductivity meter method, and the residual chlorine concentration is measured by the residual chlorine electrode method.

[0043] Colority of the wastewater: Measured by the dilution multiple method.

[0044] Whiteness of the fabric: Measured using a colorimeter according to the records in GB 8424.2 - 2001.

[0045] Dyeing color difference of the fabric: Measured using a color difference meter.

[0046] Chlorine concentration in the tail gas: Measured by the iodometric method.

[0047] Example 1

[0048] This example provides an electrochemical dyeing and bleaching method, as Figure 1 shown, which includes the following steps:

[0049] (1) Let the cotton / linen fabric after scouring enter the electrochemical device for electrochemical bleaching. The fabric used is 100 g of 30 - count pure cotton grey fabric; the electrochemical device includes an electrolytic cell, an anode, and a cathode. The electrolytic cell is a diaphragmless electrolytic cell, the anode is a ruthenium - iridium - titanium electrode, and the cathode is a pure titanium electrode; there is an electrolyte in the electrolytic cell. The electrolyte is the dyed wastewater after absorbing residual chlorine, with a pH value of 10.3, a sodium chloride concentration of 100 g / L, a colority of 200 times, and a water volume of 1 L; the electrolysis area of the anode is 200 cm 2 , and electrolyze for 2 h under the conditions of an electrolysis voltage of 10 V, a current of 10 A, and a temperature of 30 °C. After bleaching is completed, the bleached fabric and bleaching wastewater are obtained; the whiteness of the bleached fabric is 75.6, the pH value of the bleaching wastewater is 10.2, the colority is 8 times, and the residual chlorine concentration is 2100 mg / L;

[0050] (2) Add hydrochloric acid to adjust the pH value of the bleaching wastewater in the electrolytic cell to 3.5 and introduce air for dechlorination. The flow rate of the introduced air is 1 L / min and the time is 30 min, that is, the total volume ratio of the introduced air to the bleaching wastewater after adjusting the pH value to acidic is 30:1. After dechlorination is completed, dechlorinated wastewater and chlorine-containing waste gas are obtained; the residual chlorine concentration of the dechlorinated wastewater is 5 mg / L;

[0051] (3) Add sodium hydroxide to adjust the pH value of the dechlorinated wastewater in the electrolytic cell to 6.8, then add 5.4 g of reactive black and 4 g of substitute alkali. The substitute alkali is a carbonate system substitute alkali, mainly composed of a mixture of sodium carbonate, sodium hydroxide, sodium citrate, etc. Dyeing is carried out at 60 °C for 60 min. After dyeing is completed, the dyed fabric and dyeing wastewater are obtained;

[0052] (4) Introduce the dyeing wastewater obtained in step (3) and the chlorine-containing waste gas obtained in step (2) into the spray tower. The dyeing wastewater is brought into contact with the chlorine-containing waste gas by spraying to absorb the residual chlorine therein, and the tail gas that can be discharged and the dyeing wastewater after absorbing the residual chlorine are obtained; the chlorine concentration of the tail gas that can be discharged is 0.2 mg / m 3 ; The dyeing wastewater after absorbing the residual chlorine is used as the electrolyte in the electrolytic cell in step (1).

[0053] As Figure 1 shown, this embodiment may further include step (5): Soaping and color fixation are carried out on the dyed fabric obtained in step (3) to obtain the soaped and color-fixed fabric.

[0054] Compare the dyed fabric of this embodiment with the dyed fabric obtained by the conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process. The color difference (△E) is 0.32, which proves that this embodiment has a good dyeing effect.

[0055] Among them, the conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process includes:

[0056] Conventional oxygen bleaching process conditions for 30s pure cotton grey fabric: 2 g / L of sodium hydroxide, 2 g / L of hydrogen peroxide concentration, bleaching temperature 98 °C, time 60 min, and the whiteness of the bleached fabric is 72.1.

[0057] Conventional fresh sodium chloride dyeing conditions: 100 g / L of sodium chloride, 4 g / L of carbonate system substitute alkali, the bath ratio of the fabric to water is 1:10, the reactive black dye is 5.4% of the weight of the fabric, and dyeing is carried out at 60 °C for 60 min.

[0058] Example 2

[0059] This embodiment provides an electrochemical dyeing and bleaching method, as Figure 1 shown, which includes the following steps:

[0060] (1) The cotton / flax fabric after scouring is introduced into an electrochemical device for electrochemical bleaching. The fabric used is 100 g of 30-count pure cotton grey fabric. The electrochemical device includes an electrolytic cell, an anode, and a cathode. The electrolytic cell is a diaphragmless electrolytic cell. The anode is a BDD electrode, and the cathode is a pure titanium electrode. There is an electrolyte in the electrolytic cell. The electrolyte is the dyestuff wastewater after absorbing residual chlorine, with a pH value of 10.2, a sodium chloride concentration of 102 g / L, a chromaticity of 400 times, and a water volume of 1 L. The electrolytic area of the anode is 200 cm 2 , and electrolysis is carried out for 30 min under the conditions of an electrolytic voltage of 10 V, a current of 10 A, and a temperature of 30 °C. The bleaching is completed, and the bleached fabric and bleaching wastewater are obtained. The whiteness of the bleached fabric is 72.6, the pH value of the bleaching wastewater is 10.0, the chromaticity is 4 times, and the residual chlorine concentration is 1200 mg / L;

[0061] (2) Hydrochloric acid is added to adjust the pH value of the bleaching wastewater in the electrolytic cell to 3.3, and air is blown in for dechlorination. The flow rate of the blown-in air is 0.8 L / min, and the time is 30 min. That is, the total volume of the blown-in air and the volume ratio of the air to water of the bleaching wastewater after adjusting the pH value to acidic is 24:1. The dechlorination is completed, and dechlorinated wastewater and chlorine-containing waste gas are obtained. The residual chlorine concentration of the dechlorinated wastewater is 4 mg / L;

[0062] (3) Sodium hydroxide is added to adjust the pH value of the dechlorinated wastewater in the electrolytic cell to 6.6, then 5.4 g of reactive black and 4 g of substitute alkali are added. The substitute alkali is a carbonate system substitute alkali, mainly composed of a mixture of sodium carbonate, sodium hydroxide, sodium citrate, etc. Dyeing is carried out at 60 °C for 60 min. The dyeing is completed, and the dyed fabric and dyeing wastewater are obtained;

[0063] (4) The dyeing wastewater obtained in step (3) and the chlorine-containing waste gas obtained in step (2) are introduced into a spray tower. The dyeing wastewater is sprayed to contact the chlorine-containing waste gas to absorb the residual chlorine therein, and the tail gas that can be discharged and the dyeing wastewater after absorbing the residual chlorine are obtained. The chlorine concentration of the tail gas that can be discharged is 0.3 mg / m 3 ; The dyeing wastewater after absorbing the residual chlorine is used as the electrolyte in the electrolytic cell in step (1).

[0064] As Figure 1 shown, this embodiment may further include step (5): The dyed fabric obtained in step (3) is soaped and fixed color to obtain the soaped and fixed-color fabric.

[0065] The dyed fabric of this embodiment is compared with the dyed fabric obtained by the conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process. The color difference (△E) is 0.28, proving that this embodiment has a good dyeing effect. The conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process is the same as that in Example 1.

[0066] Example 3

[0067] This embodiment provides an electrochemical dyeing and bleaching system for implementing the electrochemical dyeing and bleaching method of the above embodiment. The system includes: an electrochemical device, a residual chlorine absorption device, a chlorine-containing waste gas transmission pipeline, a dyed wastewater transmission pipeline, and a dyed wastewater transmission pipeline after absorbing residual chlorine;

[0068] Among them, the electrochemical device includes an electrolytic cell, an anode, and a cathode, and there is an electrolyte in the electrolytic cell; the electrochemical device is provided with an air injection component; the electrochemical device is used to perform electrochemical bleaching, dechlorination, neutralization, and dyeing on the fabric to obtain the dyed fabric; the electrochemical device is connected to the chlorine-containing waste gas transmission pipeline and the dyed wastewater transmission pipeline;

[0069] The chlorine-containing waste gas transmission pipeline and the dyed wastewater transmission pipeline are connected to the residual chlorine absorption device, and are used to make the dyed wastewater absorb the residual chlorine in the chlorine-containing waste gas to obtain the exhaust gas that can be discharged and the dyed wastewater after absorbing residual chlorine;

[0070] The dyed wastewater transmission pipeline after absorbing residual chlorine is connected to the residual chlorine absorption device and the electrolytic cell of the electrochemical device, and is used to transport the dyed wastewater after absorbing residual chlorine to the electrochemical device as the electrolyte.

[0071] Among them, the air injection component may include an air pipe, etc.

[0072] The residual chlorine absorption device includes a spray tower, which is used to make the dyed wastewater contact the chlorine-containing waste gas in a spray manner to absorb the residual chlorine therein.

[0073] The electrochemical dyeing and bleaching system may further include: a soaping and color fixing device, which is used to perform soaping and color fixing on the dyed fabric.

[0074] Comparative Example 1

[0075] This comparative example provides an electrochemical dyeing and bleaching method, which is basically the same as that of Example 1, except that: in step (2), the pH value of the bleaching wastewater was not adjusted to 3.5, but air was directly injected for dechlorination. The flow rate of the injected air, the gas-water volume ratio, and the time were the same as those in Example 1. After dechlorination was completed, dechlorinated wastewater and chlorine-containing waste gas were obtained; the residual chlorine concentration of the dechlorinated wastewater was 1800 mg / L. The remaining steps and conditions were the same as those in Example 1. The pH value of the dyed wastewater after absorbing residual chlorine in this comparative example was 10.4, the sodium chloride concentration was 101 g / L, and the chromaticity was 5000 times. The dyed fabric in this comparative example was compared with the dyed fabric obtained by the conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process, and the color difference (△E) was 5.3. The conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process was the same as that in Example 1.

[0076] Comparative Example 2

[0077] This comparative example provides an electrochemical dyeing and bleaching method, which is basically the same as Example 1, except that: in step (3), the pH value of the dechlorinated wastewater was not adjusted to 6.8, but instead, reactive black and substitute alkali were directly added for dyeing. The dosages and components of reactive black and substitute alkali were the same as those in Example 1, and the dyeing temperature and time were also the same as those in Example 1. After dyeing, the dyed fabric and dyeing wastewater were obtained. The remaining steps and conditions were the same as those in Example 1. The pH value of the dyeing wastewater after absorbing residual chlorine in this comparative example was 9.5, the sodium chloride concentration was 103 g / L, and the chromaticity was 200 times. Comparing the dyed fabric of this comparative example with the dyed fabric obtained by the conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process, the color difference (△E) was 2.1. The conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process was the same as that in Example 1.

[0078] Comparative Example 3

[0079] This comparative example provides an electrochemical dyeing and bleaching method, which is basically the same as Example 1, except that: in step (4), the dyeing wastewater was not used to absorb the residual chlorine in the chlorine-containing waste gas, but instead, the dyeing wastewater was directly used as the electrolyte in the electrolytic cell in step (1). The remaining steps and conditions were the same as those in Example 1. The residual chlorine concentration in the chlorine-containing waste gas in this comparative example was 64 mg / m 3 , and direct discharge would cause pollution. This comparative example directly used the dyeing wastewater as the electrolyte in the electrolytic cell in step (1), which increased the load of electrochemical bleaching by 0.5 times compared with Example 1. The pH value of the dyeing wastewater before absorbing residual chlorine in this comparative example was 11.2, the sodium chloride concentration was 100 g / L, and the chromaticity was 8000 times. Comparing the dyed fabric of this comparative example with the dyed fabric obtained by the conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process, the color difference (△E) was 0.5. The conventional oxygen bleaching + fresh sodium chloride dyeing and bleaching process was the same as that in Example 1.

Claims

1. An electrochemical bleaching and dyeing method, comprising the following steps: (1) placing the fabric into an electrochemical device for electrochemical bleaching, wherein the electrochemical device contains an electrolyte, and after the bleaching is completed, a bleached fabric and bleaching wastewater are obtained; (2) adjusting the pH value of the bleaching wastewater in the electrochemical device to acidic and blowing air into it for dechlorination, and after the dechlorination is completed, obtaining dechlorinated wastewater and chlorine-containing waste gas; (3) adjusting the pH value of the dechlorinated wastewater in the electrochemical device to neutral, then adding dye and alkali for dyeing, and after the dyeing is completed, obtaining dyed fabric and dyeing wastewater; (4) using the dyeing wastewater obtained in step (3) to absorb the residual chlorine in the chlorine-containing waste gas obtained in step (2) to obtain dyeing wastewater that can discharge tail gas and absorb the residual chlorine; and using the dyeing wastewater after absorbing the residual chlorine as the electrolyte in the electrochemical device in step (1).

2. The electrochemical bleaching and dyeing method according to claim 1, wherein: In step (1), the fabric entering the electrochemical device includes scour cotton and / or linen fabric.

3. The electrochemical bleaching and dyeing method according to claim 1, wherein: In step (1), the electrochemical device comprises an electrolytic cell, an anode and a cathode, and the electrolytic cell contains an electrolyte; the electrolytic voltage of the electrochemical bleaching is 2-30V, the current is 1-10000A, the operating temperature is room temperature, and the treatment time is 1-600min; Preferably, the electrolytic cell is a diaphragmless electrolytic cell; Preferably, the anode includes a metal oxide electrode, a glassy carbon electrode, a platinum electrode, a graphite electrode or a BDD electrode, and the cathode includes a pure metal electrode, a carbon material electrode or an alloy electrode.

4. The electrochemical bleaching and dyeing method according to claim 1, wherein: In step (1), the whiteness of the bleached fabric is 65.0-85.0; Preferably, in step (1), the residual chlorine concentration of the bleaching wastewater is 0.1-3 g / L, and the chromaticity is 4-32 times.

5. The electrochemical bleaching and dyeing method according to claim 1, wherein: In step (2), adjusting the pH value of the bleaching wastewater in the electrochemical device to be acidic is adjusting the pH value to 1.0-4.0; Preferably, in step (2), the volume ratio of the blown air to the bleaching wastewater after the pH value is adjusted to acidic is 5:1-100:1, and the blowing time is 30min-8h; Preferably, in step (2), the residual chlorine concentration of the dechlorination wastewater is 0.1-5 mg / L.

6. The electrochemical bleaching and dyeing method according to claim 1, wherein: In step (3), adjusting the pH value of the dechlorination wastewater in the electrochemical device to neutral is adjusting the pH value to 6.0-7.0; Preferably, in step (3), the alkali used in dyeing by adding the dye and the alkali comprises a substitute alkali, and the amount of the substitute alkali is 1-5 g / L; Preferably, in step (3), the dyeing operation temperature is 45-80°C and the treatment time is 30-120 min.

7. The electrochemical bleaching and dyeing method according to claim 1, wherein: In step (4), the dyeing wastewater obtained in step (3) is used to absorb the residual chlorine in the chlorine-containing waste gas obtained in step (2) by using a spray tower, and the dyeing wastewater is contacted with the chlorine-containing waste gas by spraying to absorb the residual chlorine therein, thereby obtaining the dyeing wastewater that can discharge tail gas and absorb the residual chlorine; Preferably, in step (4), the chlorine concentration of the exhaust gas is 0.5 mg / m 3 the following; Preferably, in step (4), the pH value of the dyeing wastewater after absorbing residual chlorine is 8.0-11.0, the sodium chloride concentration is 50-110 g / L, and the chromaticity is 32-400 times.

8. The electrochemical bleaching and dyeing method according to claim 1, wherein: The method further comprises step (5): soaping and fixing the dyed fabric obtained in step (3) to obtain the soaped and fixed fabric.

9. An electrochemical bleaching and dyeing system, used to implement the electrochemical bleaching and dyeing method according to any one of claims 1 to 8, the system comprising: Electrochemical device, residual chlorine absorption device, chlorine-containing waste gas transmission pipeline, dyeing wastewater transmission pipeline and dyeing wastewater transmission pipeline after absorbing residual chlorine; The electrochemical device comprises an electrolytic cell, an anode and a cathode, wherein the electrolytic cell contains an electrolyte; the electrochemical device is provided with an air blowing component; the electrochemical device is used to electrochemically bleach, dechlorinate, neutralize and dye the fabric to obtain the dyed fabric; the electrochemical device is connected to the chlorine-containing waste gas delivery pipeline and the dyeing wastewater delivery pipeline; The chlorine-containing waste gas delivery pipeline and the dyeing waste water delivery pipeline are connected to the residual chlorine absorption device, which is used to make the dyeing waste water absorb the residual chlorine in the chlorine-containing waste gas to obtain the dyeing waste water that can discharge tail gas and absorb the residual chlorine; The dyeing wastewater conveying pipeline after absorbing residual chlorine is connected to the residual chlorine absorption device and the electrolytic cell of the electrochemical device, and is used to convey the dyeing wastewater after absorbing residual chlorine to the electrochemical device as electrolyte.

10. The electrochemical bleaching and dyeing system according to claim 9, wherein: The residual chlorine absorption device comprises a spray tower, which is used to make the dyeing wastewater contact with the chlorine-containing waste gas in a spraying manner to absorb the residual chlorine therein; Preferably, the electrochemical bleaching and dyeing system further comprises: a soaping and color fixing device for soaping and color fixing the dyed fabric.

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