A process for the electrochemical stripping of reactive dyeings on wool

Abstract

The application discloses a method for electrochemically stripping reactive dyeing of wool fabric. The method comprises the following steps: S1, dyeing wool fabric with reactive dyes to obtain dyed wool fabric; wherein the reactive dyes are reactive brilliant red X-3B; S2, covering the wool fabric dyed with the reactive dyes on the surface of an anode made of ruthenium iridium titanium and graphite as a cathode, and applying current to electrochemically strip the dyes; the initial concentration of sodium chloride in the electrolyte is 10-15 g / L, and the initial pH value of the electrolyte is 6-8; in the step of applying current, the current density is 10-15 mA / cm ‑2 The method has obvious effects on stripping of the reactive dyeing of the wool fabric, the wool fiber has less damage after stripping, the fiber stretch retention rate is higher, the wool fiber can be re-dyed, and the wool fiber has good recycling performance.

Description

Technical Field

[0001] This invention belongs to the field of textile dyeing and finishing technology, and specifically relates to an electrochemical method for stripping dyed wool fabrics dyed with reactive dyes. It is applicable to the reuse and reprocessing of dyed wool fabrics, realizing the green recycling of wool textiles. Background Technology

[0002] Wool, as a high-quality natural protein fiber, is widely used in the high-end textile and apparel industry due to its excellent warmth retention, moisture absorption, and comfort. With increasing market demands for personalized and environmentally friendly textiles, the need for recycling and reprocessing dyed wool fabrics is growing, making the stripping process a key step in the sustainable utilization of wool.

[0003] Currently, reactive dyes commonly used in industry possess high colorfastness due to their covalent bonding with wool fibers, but stripping them is extremely difficult. Traditional chemical stripping methods rely on strong reducing agents (such as thiourea dioxide and sodium borohydride) or oxidizing agents (such as hydrogen peroxide), requiring high temperatures to destroy the dye structure. This results in high energy consumption, complex processes, and significant damage to wool fibers, leading to a decrease in strength. Furthermore, traditional methods use large amounts of chemical reagents, generating difficult-to-treat wastewater containing sulfur and boron, polluting the environment and incurring high treatment costs. Although some research has attempted to develop mild stripping auxiliaries or physical-assisted stripping technologies (such as ultrasonic treatment), their efficiency is limited and equipment costs are high, making them difficult to scale up for industrial production.

[0004] Electrochemical technology, with its advantages of mild reaction conditions, low reagent consumption, and high controllability, has gained increasing attention in clean production of textile dyeing and finishing in recent years. It can destroy dye chromophores or sever dye-fiber bonds through redox reactions on electrode surfaces, making it suitable for treating recalcitrant dyes. However, existing research largely focuses on the electrochemical reduction or degradation of dyes, with limited systematic studies on its application to the stripping of protein fibers such as wool. The stripping mechanism, fiber damage control, and process optimization remain incomplete. Therefore, developing a high-efficiency, low-consumption, and environmentally friendly new technology for wool stripping has become a key research focus. Summary of the Invention

[0005] The purpose of this invention is to provide a method for electrochemical stripping of reactive dyes used to dye wool fabrics. This method has a significant effect on stripping reactive dyes from wool fabrics, resulting in less damage to the wool fibers after stripping, a higher fiber stretch retention rate, the ability to be re-dyed, and good recyclability.

[0006] In a first aspect, the present invention provides a method for dyeing wool fabrics with electrochemical stripping reactive dyes, comprising the following steps:

[0007] S1. Dye wool fabric with reactive dyes to obtain dyed wool fabric;

[0008] The reactive dye is Reactive Brilliant Red X-3B;

[0009] S2. Using ruthenium-iridium-titanium as the anode, graphite as the cathode, and sodium chloride aqueous solution as the electrolyte, the dyed wool fabric is covered on the anode surface, and an electric current is applied to perform electrochemical stripping treatment.

[0010] The initial concentration of sodium chloride in the electrolyte is 10–15 g / L;

[0011] The initial pH value of the electrolyte is 6 to 8;

[0012] In the step of applying the current, the current density is 10–15 mA / cm². -2 .

[0013] Based on the above technical solutions, the method of the present invention optimizes the electrochemical stripping treatment conditions. The initial concentration of sodium chloride in the selected electrolyte, the initial pH value of the electrolyte, and the current density not only have a significant effect on stripping wool fabrics dyed with reactive dyes, but also result in less damage to the wool fibers after stripping and a higher fiber stretch retention rate.

[0014] In a preferred embodiment of the present invention, the initial concentration of sodium chloride in the electrolyte is 15 g / L;

[0015] The initial pH value of the electrolyte is 6;

[0016] In the current application step, the current density is 15 mA / cm². -2 .

[0017] The applied current is supplied by a DC power supply.

[0018] According to an embodiment of the present invention, the wool fabric is 100% pure wool. As an example, the specifications of the wool fabric are as follows: filament 11.2-11.3, 26 / 2N, E12G.

[0019] Furthermore, the staining step includes:

[0020] 1) Place the wool fabric in the dye bath of the reactive dye, add an acidic reagent to adjust the pH value to 3-4, and keep it at 40℃-50℃ for 25-30 minutes (e.g., keep it at 40℃ for 25 minutes).

[0021] 2) Heat to 60-70℃, add sodium sulfate to the system in step 1) and keep warm for 20-30 minutes (e.g., heat to 60℃ and keep warm for 20 minutes).

[0022] 3) Heat to 90-95℃, add sodium hydroxide to the system in step 2) and keep warm for 30-40 minutes (e.g., heat to 95℃ and keep warm for 30 minutes).

[0023] 4) Cool down to 75-85℃, add sodium carbonate to the system in step 3) and keep warm for 10-20 minutes (if cooling down to 80℃, keep warm for 10 minutes).

[0024] 5) Cool down to 55-65℃ and keep warm for 10-15 minutes (if cool down to 60℃, keep warm for 10 minutes).

[0025] 6) Soap washing, dehydration and drying.

[0026] Furthermore, as an example, in step 1), the concentration of the reactive dye in the dyeing solution is 0.01 g / L; optionally, the acidic reagent is acetic acid;

[0027] In step 2), the concentration of sodium sulfate in the system is 25 g / L;

[0028] In step 3), the concentration of sodium hydroxide in the system is 1 g / L;

[0029] In step 4), the concentration of sodium carbonate in the system is 2 g / L;

[0030] In steps 1)-5), the bath ratio is 1 g: 20 mL.

[0031] To remove lanolin and dust, the wool fabric dyed with the reactive dye is pre-dyed by: washing the wool fabric with anhydrous ethanol at 30-40°C and drying it, such as by drying at room temperature.

[0032] According to an embodiment of the present invention, the initial pH value of the electrolyte is adjusted by acetic acid.

[0033] According to an embodiment of the present invention, the size of the wool fabric dyed by the reactive dye is consistent with the size of the surface of the anode used to cover the wool fabric; as an example, the size of the anode is 50×100mm and the thickness is 1mm.

[0034] According to an embodiment of the present invention, each 5cm × 3cm piece of the wool fabric is placed in 1L of the electrolyte; as an example, the amount of the electrolyte is 1L.

[0035] According to an embodiment of the present invention, the electrochemical stripping treatment time is 60 min.

[0036] The present invention has the following beneficial effects:

[0037] (1) The present invention uses an electrochemical method for color stripping, with sodium chloride as the electrolyte. It does not require the use of strong reducing or oxidizing agents, reduces the consumption of chemical reagents, and reduces the discharge of difficult-to-treat wastewater containing sulfur and boron. Moreover, the electrolyte can be recycled. After 11 cycles, the color stripping effect can still reach 80%, which is more environmentally friendly.

[0038] (2) Electrochemical stripping is carried out at room temperature, the reaction conditions are relatively mild, and the damage to wool fibers is small. At the same time, the reaction is precisely controlled by adjusting the current density, there is no thermal inertia loss, and the energy saving effect is significant.

[0039] (3) The method of the present invention can effectively control the damage to wool fibers, and the tensile strength retention rate of wool fabric after stripping is relatively high, and the stripping efficiency is over 90%.

[0040] (4) The color stripping system of the present invention has a low bath ratio and the BOD / COD value of the color stripping waste liquid after electrochemical color stripping is the highest, which reduces water consumption and wastewater treatment costs. In addition, the equipment and reagents used are low in cost, simplifying the process and facilitating industrial promotion. It has broad application prospects in the field of clean production of textile dyeing and finishing. Attached Figure Description

[0041] Figure 1 This is a process flow diagram of dyeing wool fabric with reactive dyes in Embodiment 1 of the present invention.

[0042] Figure 2 This illustrates the effect of current density on the bleaching and stretching properties of dyed wool in Example 1 of the present invention.

[0043] Figure 3 This illustrates the effect of the initial NaCl concentration on the decolorization and tensile properties of dyed wool in Example 2 of this invention.

[0044] Figure 4 This illustrates the effect of the initial pH of the electrolyte solution on the decolorization and tensile properties of dyed wool in Example 3 of the present invention.

[0045] Figure 5 The image shows the infrared spectra of the wool fabric dyed with reactive dyes before and after stripping in Example 4 of this invention.

[0046] Figure 6 SEM images of wool fibers dyed with reactive dyes before and after stripping in Example 4 of the present invention: dyed wool fabric (a); dyed wool fabric after electrochemical treatment (b).

[0047] Figure 7 The color charts are of the raw wool fabric, the wool fabric dyed with reactive dyes, and the fabric samples taken every 10 minutes during electrochemical treatment in Example 4 of the present invention.

[0048] Figure 8The values ​​are the BOD / COD values ​​of the electrochemical solution before and after color stripping in Example 4 of this invention. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0050] Unless otherwise specified, the methods used in the following embodiments are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0051] The wool fabric (Lami 11.2-11.3, 100% wool, 26 / 2N, E12G) in the following examples was provided by Erdos Group Co., Ltd.

[0052] Sodium sulfate was purchased from Aladdin Holdings Group Limited.

[0053] The Ti / TiO2-RuO2-IrO2 electrode and the graphite electrode were both purchased from Suzhou Shuertai Industrial Technology Co., Ltd., and both are 50×100mm in size and 1mm thick.

[0054] The performance testing methods in the following embodiments are as follows:

[0055] Color intensity of dyed and faded fabrics was measured at 600 nm using a Data Color 800 colorimeter under D65 light source / 10° observer conditions, including specular reflection. The color intensity of dyed fabrics is expressed as a K / S value, representing the ratio of absorbed to reflected light. K / S values ​​were measured in four different regions selected from each side of the fabric sample, and the average value was calculated.

[0056] Color peeling performance:

[0057]

[0058] in, This represents the arithmetic mean of the K / S values ​​of a single sample before color stripping. This represents the arithmetic mean of the K / S values ​​for a single sample after color stripping.

[0059] Tensile properties:

[0060]

[0061] Among them, R TSThis indicates the tensile strength retention rate (%) of a single sample after color peeling. This indicates the tensile strength value of the wool fabric sample before color stripping. This indicates the tensile strength value of a wool fabric sample after it has been decolorized using an electrochemical method.

[0062] BOD / COD values: Chemical oxygen demand (COD) was determined by the dichromate method, and biochemical oxygen demand (BOD) was determined by the standard dilution method.

[0063] Example 1

[0064] This embodiment investigated the effect of current density on the bleaching and tensile properties of dyed wool. The specific steps are as follows:

[0065] (1) Pretreatment of wool fabrics: Add anhydrous ethanol to the wool fabrics and ultrasonically clean them at 30°C to remove lanolin and dust. Dry them at room temperature for later use.

[0066] (2) Dyeing wool fabrics: such as Figure 1 As shown, the wool fabric was dyed according to the following steps: 1) In a small-scale dyeing machine, the pretreated wool fabric was placed in a dye bath of Reactive Brilliant Red X-3B, with a concentration of 0.01 g / L. Acetic acid was added to adjust the pH to 3-4, and the mixture was kept at 40°C for 25 min; 2) The temperature was raised to 60°C, and sodium sulfate was added to the system in step 1) and kept at 25 g / L for 20 min; 3) The temperature was raised to 95°C, and NaOH was added to the system in step 2) and kept at 1 g / L for 30 min; 4) The temperature was lowered to 80°C, and sodium carbonate was added to the system in step 3) and kept at 2 g / L for 10 min; 5) The temperature was lowered to 60°C and kept at 10 min; In steps 1)-5), the liquor ratio was 1 g: 20 mL; 6) Soaping, dehydration, and drying were performed.

[0067] (3) Electrochemical stripping: An electrolytic cell was constructed, with ruthenium-iridium-titanium (Ti / TiO2-RuO2-IrO2) as the anode and graphite as the cathode. The initial pH of the electrolyte solution (15 g / L sodium chloride) was adjusted to 6 with acetic acid. The volume of the electrolyte solution in the electrolytic cell was 1 L. A DC power supply was connected, and different currents were applied to achieve current densities of 5 mA / cm². -2 10 mA / cm -2 15 mA / cm -2 20mA / cm -2 Add dyed wool fabric (5cm x 3cm) to the anode and treat for 60 minutes. After treatment, remove the wool fabric, wash it clean, and air dry at room temperature.

[0068] Depend on Figure 2 It is evident that the applied current density plays a crucial role in the electrochemical oxidation process, directly affecting the generation efficiency of hydroxyl radicals and other oxidants on the electrode surface. When the current density is 15 mA / cm²,... -2 At this time, the stripping rate of wool fabric reached 96.5%, and the tensile retention rate of the fabric also reached 86.0%. In an electrolyte solution containing chloride ions, an electric current is applied to form active chlorine species with strong oxidizing properties. These species react with the dye molecules on the wool fabric, effectively destroying the chromophores and molecular structure of the dye, causing the dye to detach from the fabric. At this time, the amount of active chlorine generated is just enough to efficiently strip the dye, and the damage to the fiber structure is within an acceptable range.

[0069] Example 2

[0070] This example investigated the effect of the initial concentration of sodium chloride on the decolorization and tensile properties of dyed wool.

[0071] The difference from Example 1 lies in adjusting the conditions of step (3). The remaining steps (1) and (2) are completely identical. Specifically, step (3) is as follows: Electrochemical stripping: An electrolytic cell is constructed, with ruthenium-iridium-titanium (Ti / TiO2-RuO2-IrO2) as the anode and graphite as the cathode. The initial pH of the electrolyte solution (sodium chloride solutions with initial concentrations of 5 g / L, 10 g / L, 15 g / L, 20 g / L, and 25 g / L, respectively) is adjusted to 6 using acetic acid. A DC power supply is then applied at 15 mA / cm². -2 The current density was adjusted. Dyed wool fabric (5cm x 3cm) was placed over the anode and treated for 60 minutes. After treatment, the wool fabric was removed, cleaned, and air-dried at room temperature.

[0072] Depend on Figure 3 It can be seen that when the initial concentration of sodium chloride is 15 g / L, the stripping rate of wool fabrics increases significantly to 93%, and the tensile retention rate can reach 78.6%. The increase of NaCl concentration improves the conductivity of the solution, enhances the current efficiency of the electrochemical system, and increases the amount of active chlorine substances converted at the anode, effectively destroying the chromophores of the dye, thereby increasing the stripping efficiency of wool fabrics.

[0073] Example 3

[0074] This example investigated the effect of the initial pH of the electrolyte solution on the decolorization and tensile properties of dyed wool.

[0075] The difference from Example 1 lies in adjusting the conditions of step (3). The remaining steps (1) and (2) are completely identical. Specifically, step (3) is as follows: Electrochemical stripping: An electrolytic cell is constructed, with ruthenium-iridium-titanium (Ti / TiO2-RuO2-IrO2) as the anode and graphite as the cathode. The initial pH of the electrolyte solution (sodium chloride solution with an initial concentration of 15 g / L) is adjusted to 2, 4, 6, 8, 10, and 12 respectively using acetic acid. A DC power supply is then applied at 15 mA / cm². -2 The current density was adjusted. Dyed wool fabric (5cm x 3cm) was placed over the anode and treated for 60 minutes. After treatment, the wool fabric was removed, cleaned, and air-dried at room temperature.

[0076] Depend on Figure 4 It can be seen that when the pH is 6, it enters the weakly acidic neutral region, and the surface charge of TiO2 tends to be neutral (charge balance is reached at pH≈6.3). At this time, the OH- yield is maximized, and the active chlorine substances generated by NaCl electrolysis can efficiently destroy the chromophores of the dye. In addition, wool fibers are negatively charged because the pH is higher than the isoelectric point, which increases the electrostatic repulsion between the wool fibers and the dye anions, promoting dye desorption and making the dye easier to peel off. The pH environment in this range is relatively mild, and oxidation mainly acts on the dye. The fiber matrix is ​​relatively intact, the electrolyte ion strength enhances dye diffusion, reduces local peroxidation, and also reduces local damage to the fabric. Therefore, the fabric has good tensile strength retention.

[0077] Example 4

[0078] This embodiment compares the characterization results of wool fabrics dyed with electrochemical stripping reactive dyes before and after stripping treatment.

[0079] The difference from Example 1 is that the conditions in step (3) are adjusted to the optimal conditions determined in Examples 1-3 above. The remaining steps (1) and (2) are completely the same. Specifically, step (3) is as follows: Electrochemical stripping: An electrolytic cell is built, with ruthenium-iridium-titanium (Ti / TiO2-RuO2-IrO2) as the anode and graphite as the cathode. The initial pH of the electrolyte solution (sodium chloride solution with an initial concentration of 15 g / L) is adjusted to 6 with acetic acid. A DC power supply is then applied at 15 mA / cm. -2 The current density was adjusted. Dyed wool fabric (5cm x 3cm) was placed over the anode and treated for 60 minutes. After treatment, the wool fabric was removed, cleaned, and air-dried at room temperature.

[0080] Figure 5 The results showed that the Fourier transform infrared spectra of the wool fabrics after the stripping treatment differed significantly from those dyed with reactive dyes. The difference was most pronounced in the 3400-3200 cm⁻¹ range. -1Within the wavenumber range, changes in hydrogen bonding are key to resolving the exfoliation process. 3281 cm⁻¹ -1 A broad and strong absorption band is observed at this point, which is a strong hydrogen bond coupling peak formed by the interaction between the NH stretching vibration of wool keratin and the OH stretching vibration of the Reactive Brilliant Red X-3B anthraquinone parent ring. This indicates that the dye is tightly anchored to the wool fiber through hydrogen bonds. After stripping, 3325 cm⁻¹ -1 The corresponding stretching vibration of free keratin NH indicates that the intrinsic state of wool fibers is gradually restored.

[0081] At 1700-1500 cm -1 The breaking process of characteristic bonds of chromophores was observed in the key wavenumber range. At 1550 cm⁻¹ -1 The amide II band at the location is interfered with by the characteristic peak of the dye azo group, forming a distinct shoulder peak. After stripping, at 1550 cm⁻¹ -1 The disappearance of the shoulder peak and the restoration of symmetrical NH bending vibration indicate that the azo bond is reduced and broken to generate two molecules of primary amine.

[0082] In 1300-1100 cm -1 In the fingerprint area, the dissociation process of covalent bonds in active groups is clearly visible. After peeling, 1295cm -1 The decrease in peak intensity indicates that the vinyl sulfone group was reduced to a water-soluble sulfinate, and the breaking of the covalent bond led to a change in its chemical structure; 1172 cm -1 The increased peak intensity confirms the dissociation of the sulfonic acid group ionic bond.

[0083] 1120 cm -1 The disulfide bond characteristic peak at the oxidative stress is a key indicator for verifying the integrity of wool fibers. Before and after the stripping process, the position and intensity of this peak remained stable with minimal changes, and no new oxidation peaks appeared. This proves that the electrochemical stripping process did not damage the cross-linking structure of wool keratin, ensuring that the intrinsic properties of wool fibers were maintained while achieving efficient stripping.

[0084]

[0085] As shown in Table 1, the nitrogen and sulfur elements decreased significantly after stripping, indicating that the chromophores of the dye were destroyed and the dye was effectively removed.

[0086] The surface morphology of the immobilized reactive Brilliant Red X-3B dye on a wool fabric substrate before and after electrochemical treatment was observed using scanning electron microscopy, and its surface chemical composition was also analyzed. Figure 6 The dyeing of wool fabrics was performed at magnifications of 100x, 1000x, and 5000x, respectively, and at an initial pH of 6 and a current density of 15 mA / cm². -2Scanning electron microscope image of wool fabric after electrochemical treatment for 60 min at a sodium chloride concentration of 15 g / L.

[0087] Figure 7 This is a color chart for wool fabrics. The first color chart shows the original color of the wool fabric. From the second to the last color chart, they show the colors of wool fabrics dyed with reactive dyes and fabric samples taken every 10 minutes after electrochemical treatment.

[0088] Figure 8 The values ​​represent the BOD / COD ratios before and after electrochemical solution stripping. A higher BOD / COD ratio indicates better aerobic biological treatment; a BOD / COD ratio > 0.3 indicates that the wastewater is biodegradable. Figure 8 As shown, the BOD / COD value of the decolorization wastewater treated by the electrochemical decolorization method was the highest. After 11 cycles, the BOD / COD value increased to 0.48, indicating that the decolorization wastewater treated by the electrochemical decolorization method is more prone to chemical and biological degradation, greatly reducing the burden of wastewater treatment.

[0089] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including modifications made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A method for dyeing wool fabrics with electrochemical stripping reactive dyes, characterized in that, Includes the following steps: S1. Dye wool fabric with reactive dyes to obtain dyed wool fabric; The wool fabric is 100% pure wool, and the reactive dye is Reactive Brilliant Red X-3B. The staining steps include: 1) Place the wool fabric in the dye bath of the reactive dye, add an acidic reagent to adjust the pH value to 3-4, and keep it at 40℃-50℃ for 25-30 minutes; 2) Heat to 60-70℃, add sodium sulfate to the system in step 1), and keep warm for 20-30 minutes; 3) Heat to 90-95℃, add sodium hydroxide to the system in step 2), and keep warm for 30-40 minutes; 4) Cool down to 75-85℃, add sodium carbonate to the system in step 3), and keep warm for 10-20 minutes; 5) Cool down to 55-65℃ and keep warm for 10-15 minutes; 6) Soap washing, dehydration, and drying; S2. Using ruthenium-iridium-titanium as the anode, graphite as the cathode, and sodium chloride aqueous solution as the electrolyte, the dyed wool fabric is covered on the anode surface, and an electric current is applied to perform electrochemical stripping treatment. The initial concentration of sodium chloride in the electrolyte is 15 g / L; The initial pH value of the electrolyte is 6; In the current application step, the current density is 15 mA / cm². -2 ; The electrochemical stripping treatment time is 60 min.

2. The method for dyeing wool fabrics with electrochemical stripping reactive dyes according to claim 1, characterized in that: In step 1), the concentration of the reactive dye in the dyeing solution is 0.01 g / L; In step 1), the acidic reagent is acetic acid; In step 2), the concentration of sodium sulfate in the system is 25 g / L; In step 3), the concentration of sodium hydroxide in the system is 1 g / L; In step 4), the concentration of sodium carbonate in the system is 2 g / L; In steps 1)-5), the liquor ratio is 1 g: 20 mL.

3. The method for dyeing wool fabrics with electrochemical stripping reactive dyes according to claim 1, characterized in that: Before the dyeing step, the wool fabric is washed with anhydrous ethanol at 30-40°C and then dried.

4. The method for dyeing wool fabrics with electrochemical stripping reactive dyes according to claim 1, characterized in that: The initial pH of the electrolyte is adjusted by acetic acid.

5. The method for dyeing wool fabrics with electrochemical stripping reactive dyes according to claim 1, characterized in that: Each 5cm x 3cm piece of the wool fabric is placed in 1L of the electrolyte.

6. The method for dyeing wool fabrics with electrochemical stripping reactive dyes according to claim 1, characterized in that: The method further includes the step of repeatedly using the electrolyte to electrochemically strip the dyed wool fabric.

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