CN105648789A - Indirect electrochemical reduction dyeing method utilizing graphite felt electrodes - Google Patents

Abstract

The invention relates to an indirect electrochemical reduction dyeing method using graphite felt electrodes. In the process, through electrochemical reduction, cotton fabrics (cotton and cotton-type fabrics) are added to the obtained catholyte for dyeing, the bath ratio is 1:100-200; then placed in the air for oxidation, repeated dyeing oxidation, soaping, Wash, tumble dry. The invention can dye in a short time at low temperature, and can avoid the problem of uneven and impermeable dyeing. For deep-colored fabrics, the energy-saving effect is more obvious, the dyeing time is reduced by about 40%, and the energy consumption is saved by 75%-85%. .

Description

A method for indirect electrochemical reduction dyeing using graphite felt electrodes

technical field

The invention belongs to the field of vat dyeing methods, in particular to a method for indirect electrochemical reduction dyeing using graphite felt electrodes.

Background technique

Due to its good dyeing performance, vat dyes have an irreplaceable position among many dye varieties. Because vat dyes are insoluble in water, but can be reduced by reducing agents to form water-soluble leuco dyes, and then have affinity for fibers to dye fibers. At present, the traditional dyeing process uses hydrosulfite to reduce vat dyes, which is likely to cause serious environmental pollution problems. Therefore, reducing the pollution of vat dyes has always been the focus of vat dye dyeing process research.

Electrochemical reduction is a new reduction technology that can replace hydrosulfite (sodium dithionite), including electrocatalytic hydrogenation, direct electrochemical reduction, and indirect electrochemical reduction. The current patent situation includes the direct electrical protection disclosed in U.S. Patent No. US3,953,307 to reduce the consumption process of reducing agent by oxygen; the direct electrochemical reduction process disclosed in ElectrochimicaActa47 (2002) 1989; No. Disclosed in the process through the intermediate as electron transfer. Among them, the direct electrification protection method fails to completely solve the process of replacing the added reducing agent, and the direct electrochemical reduction process, due to the influence of the contact efficiency of the insoluble vat dye to the electrode, the reduction efficiency is not ideal. Therefore, by using a "mediator" to obtain electrons from the surface of the cathode, the indirect electrochemical reduction dyeing technology that transfers electrons to dyes is the most widely studied, and the reduction process of dyes is also approaching maturity.

However, in terms of electrode selection in the reduction process, in view of the limited electrode specific surface area, electrode research is also a research direction at present. The cathode electrode material of the multi-layer filter cathode flow electrolytic cell invented by Yang Lijian uses metal wire, the anode material is nickel mesh, and cation exchange is used. A membrane separates the two polar compartments. Reducing the medium in the cathode chamber reduces the dye to a reduced state at a reduction potential of 500mV to 800mV, that is, to a soluble dye, and flows into the dye vat. Rossler's team used graphite particles as the electrode material and designed a fixed fluidized bed reactor, all trying to improve the current efficiency. Therefore, it is necessary to select a new type of reduction electrode to solve the problem of low current efficiency.

Contents of the invention

The technical problem to be solved by the present invention is to provide an indirect electrochemical reduction dyeing method using graphite felt electrodes, which can dye vat dye leuco bodies on fibers at low temperature and in a short time.

A kind of method utilizing graphite felt electrode indirect electrochemical reduction dyeing of the present invention comprises:

Pour the catholyte and the anolyte into the cathode and anode redox chambers respectively, turn on the electricity for reduction, add the vat dye to the cathode redox solution, and electrochemically reduce to obtain the catholyte; add cotton fabric or cotton blended fabric Dyeing is carried out in the obtained catholyte, the bath ratio is 1:100-200; then placed in the air for oxidation, repeated dyeing oxidation, soaping, washing, and drying; wherein, the cathode is a graphite felt electrode.

The catholyte is a mixture of Fe ₂ (SO ₄ ) ₃ , TEA and NaOH; wherein the concentration of Fe ₂ (SO ₄ ) ₃ is 4.8-5.8 g/L; the concentration of TEA is 35.6-36.7 g/L; The concentration of NaOH is 14.2-15.3g/L.

Preparation of the catholyte: as the catholyte, the required Fe ₂ (SO ₄ ) ₃ , TEA, and NaOH were respectively dissolved in a 250ml beaker, mixed and stirred for 1.5 hours, and suction filtered to obtain a clear and transparent solution.

The anolyte was 30 g/L H ₂ SO ₄ .

The time for the energized reduction is 10 to 25 minutes.

The conditions of the electrochemical reduction are: carry out at room temperature, the working voltage is 4-5V, the corresponding working current is 0.2-0.4A, the electrification time is 20-30min, and the volume of the dye solution is 50-60ml. .

The dyeing time is 10-30 minutes.

The oxidation time in the air is 15-30 minutes; the times of repeated dyeing and oxidation are 3-8.

The soaping conditions are as follows: the bath ratio is 1:100-200, the time is 10-20 minutes, 5g/L standard soap flakes and 5g/L soda ash are mixed and dissolved as standard soaping liquid.

The graphite felt is cleaned before use: the graphite felt electrode is repeatedly rinsed with distilled water, and after the loose debris inside the surface is washed away, it is dried in an oven.

The electrolytic cell used in the electrochemical reduction process in the present invention: the electrolytic cell includes a cathode and an anode, which are separated by an ion exchange membrane between the cathode and the anode, and are respectively formed between the ion exchange membrane, the cathode and the anode. The cathode area and the anode area, and graphite felt is placed in the cathode area as the cathode material, and the cathode area is provided with inlets and outlets for vat dyes to flow in and out. The cathode and the anode are vertically arranged in parallel, and the cathode is located outside the anode.

The method of electrochemically reducing the dye in the present invention is to make the reducing substance pass through the graphite felt electrode in the cathode tank and complete the electrochemical reduction by means of the electron transfer of the mediator under alkaline conditions.

The invention introduces the graphite felt into the leuco dyeing process of vat dyes, increases the leuco dye diffusion system, reduces the activation energy of dye dyeing, and realizes the purpose of dyeing fibers by vat dyes in a short time at low temperature.

Beneficial effect

(1) The present invention achieves the purpose of rapid dyeing at low temperature by adopting a graphite felt as the cathode material; because the graphite felt has a potential range, good stability, and an efficient specific surface area, the dye can be dyed in the reduction process. Fully contact with the polar plate to gain and lose electrons, so as to dye the fabric; this is beneficial to the low temperature, so that the dye can be fully transferred during the rapid dyeing process, ensuring the uniformity of dyeing;

(2) The present invention carries out dyeing with vat dyes, which can be dyed in a short time at low temperature, and can avoid the problem of uneven and impermeable dyeing. For deep-colored fabrics, the energy-saving effect is more obvious, and the dyeing time is reduced by about 40%. Save energy consumption by 75%-85%.

Description of drawings

Fig. 1 is the schematic diagram of electrochemical reduction among the present invention;

Fig. 2 is the mechanism figure of indirect electrochemical reduction dye on graphite felt electrode among the present invention;

Fig. 3 is a graph of cyclic voltammetry at different rates in the present invention.

detailed description

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present 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 the present application.

The graphite felt in the embodiment of the present invention was purchased from Beijing Jinglong Special Carbon Co., Ltd., and the performance parameters are shown in Table 1. All reagents used were of analytical grade and no further purification was required during use.

Table 1 Performance parameters of graphite felt

Example 1

A kind of processing method of dark cotton fabric, concrete steps are:

(1) Treat graphite felt:

a. Rinse the graphite felt electrode repeatedly with distilled water to remove loose debris inside the surface;

b. Dry the cleaned graphite felt in an oven at 100° C. for 1 hour.

(2) Solution configuration:

a. Catholyte, dissolve Fe ₂ (SO ₄ ) ₃ , TEA, and NaOH in a 250ml beaker respectively, and the concentration of each substance meets: 4.9g/LFe ₂ (SO ₄ ) ₃ , 35.65g/LTEA, 14.24g/LNaOH ; After mixing and stirring for 1.5h, filter with suction to obtain a clear and transparent solution;

b. Anolyte, H ₂ SO ₄ of 30g/L;

c. Soaping liquid: 5g/L standard soap flakes and 5g/L soda ash are mixed and dissolved as standard soaping liquid.

(3) Indirect electrochemical reduction dyeing:

a. The electrolyte prepared above is poured into the cathode and anode redox chambers respectively;

b. After energized reduction for 15 minutes, add 0.1 g of vat dye to the cathode redox solution for electrochemical reduction; the conditions for electrochemical reduction here: at room temperature, the working voltage is 5V, and the corresponding working current is 0.2A. The time is 20min, and the volume of dye solution is 50ml.

c. Pour catholyte into a beaker and add cotton cloth, the bath ratio is 1:100, and dye for 15 minutes;

d. Then put it in the air for 20 minutes to oxidize until it no longer changes color, repeat the dyeing and oxidation 5 times, and finally use the prepared soap boiling liquid to soap boil, the liquor ratio is 1:100, boil for 15 minutes, wash and dry after soap boiling Dry.

Example 2

A kind of processing method of light-colored cotton fabric, concrete steps are:

(1) Treat graphite felt:

a. Rinse the graphite felt motor repeatedly with distilled water to remove loose debris inside the surface;

b. Dry the cleaned graphite felt in an oven at 100° C. for 1 hour.

(2) Solution configuration:

Catholyte, dissolve Fe ₂ (SO ₄ ) ₃ , TEA, and NaOH in a 250ml beaker respectively, and the concentration of each substance meets: 4.9g/LFe ₂ (SO ₄ ) ₃ , 35.65g/LTEA, 14.24g/LNaOH; mix After stirring for 1.5h, filter with suction to obtain a clear and transparent solution;

b. Anolyte, H ₂ SO ₄ of 30g/L;

c. Soaping liquid: 5g/L standard soap flakes and 5g/L soda ash are mixed and dissolved as standard soaping liquid.

(3) Indirect electrochemical reduction dyeing:

a. The electrolyte prepared above is poured into the cathode and anode redox chambers respectively;

b. After energizing and reducing for 20 minutes, add 0.1g of vat dye to the cathode redox solution for electrochemical reduction; the conditions for electrochemical reduction here: at room temperature, the working voltage is 5V, and the corresponding working current is 0.2A. The time is 20min, and the volume of dye solution is also 50ml.

c. Pour catholyte into a beaker and add cotton cloth, the bath ratio is 1:100, and dye for 20 minutes;

d. Then put it in the air for 25 minutes to oxidize until it no longer changes color, repeat the dyeing and oxidation 5 times, and finally use the prepared soap boiling liquid to soap boil, the bath ratio is 1:100, boil for 15 minutes, wash and dry after soap boiling Dry.

The electrochemical workstation CHI660E of Shanghai Chenhua Instrument Co., Ltd. uses graphite felt as the working electrode, platinum electrode as the counter electrode, and calomel electrode as the reference electrode to scan the dye solution medium system after electrochemical reduction, and pass 0.02V /s, 0.05V/s, 0.2V/s to scan to obtain different rate cyclic voltammetry curves, as shown in Figure 3, when the voltage negatively scans to the reduction potential of the iron amine complex (Fe ³⁺ L) When , Fe ³⁺ L is reduced on the electrode. Since the solution is static, the concentration of Fe ³⁺ L on the electrode surface will be lower than the concentration in the solution body, resulting in concentration polarization. According to the Nernst equation, a reduction peak current is formed. When the voltage is further increased to a certain negative value, the reaction speed of Fe ³⁺ L on the electrode is accelerated, and the diffusion speed of Fe ³⁺ L to the solution body cannot keep up with the reaction speed of the electrode. In an instant, the concentration of Fe ³⁺ L on the electrode surface tends to zero, and the current value reaches the maximum, i=k _s (c _o -c _s ). The higher the reduction peak current value, the greater the concentration polarization, and the more Fe ³⁺ L adsorbed on the electrode surface. After that, because Fe ²⁺ L produces zero concentration difference on the electrode surface, diffusion movement will occur, and the electrode surface The amount of Fe ²⁺ L decreases, so its current value begins to drop. It can be seen from the figure that the reduction potential of the media system is -932.4mV, which can reduce most of the vat dyes.

Calculation of energy consumption for reduction by traditional hydrosulfite method: Since hydrosulfite can exert its reduction effect only at a high temperature above 60°C, the reduction temperature of the selected reduction temperature dyeing solution is 60°C, the room temperature is set at 20°C, and the dyeing solution is calculated as 50ml . Since the mass of the dye is very small, the heat obtained by the dye can be ignored. The heat consumed in this process can be considered as the heat required for 50ml of water to rise from room temperature 20°C to 60°C. The specific calculation process is as follows:

Q _heat = C _water M _water × (t ₂ -t ₁ ) + C _dye M _dye × (t ₂ -t ₁ )

=4.2×50×40

=8400J

Calculation of energy consumption of electrochemical reduction: Electrochemical reduction has no requirement on temperature, it is selected to be carried out at room temperature, the working voltage is 5V, the corresponding working current is 0.2A, the power-on time is 20min, and the volume of the dyeing solution is also 50ml. There is no change, the system does not absorb heat from the outside, and the heat consumed in this process is the energy consumed by electrification. The extreme process is as follows:

E electricity = UIt = 5 × 0.2 × 20 × 60 = 1200J

Saving rate = 1-E _electricity \ Q _heat × 100% = 85.7%

The dyeing time used for dyeing the fabric by the above method is 15-20 minutes, and the energy consumption is saved by 75%-85%. The dyeing time used for dyeing the fabric by adopting the method in the prior art is 20-25 minutes. It can be seen that the dyeing time of the present invention is reduced by about 40% compared with the prior art. It is not difficult to find that using the method of the present invention to dye vat dyes can be dyed at low temperature in a short time, and can avoid the problem of uneven and impermeable dyeing. For deep-colored fabrics, the energy-saving effect is more obvious and the dyeing time is reduced. About 40%, saving energy consumption by 75%-85%.

Claims (8)

1. utilize a method for graphite felt electrode indirect electrochemical vat dyeing, comprising:

Catholyte and anolyte being poured into respectively in negative electrode, anode oxidoreductase room, energising reduction, joins vat dyes in cathode oxidation reduced liquid, by electrochemical reduction, obtains catholyte; Cotton and cotton fabric being joined in the catholyte obtained and dye, bath raio is 1:100��200; Then being placed in air oxidation, dual-staining is oxidized, soap boiling, and washing is dried; Wherein, negative electrode is graphite felt electrode.

2. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterised in that, described catholyte is Fe₂(SO₄)₃, TEA and NaOH mixed solution; Wherein Fe₂(SO₄)₃Concentration be 4.8��5.8g/L; The concentration of TEA is 35.6��36.7g/L; The concentration of NaOH is 14.2��15.3g/L.

3. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterised in that, described anolyte is the H of 30g/L₂SO₄��

4. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterised in that, the time of described energising reduction is 10��25min.

5. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterized in that, the condition of described electrochemical reduction is: carry out under room temperature, operating voltage is 4-5V, corresponding working current is 0.2-0.4A, conduction time 20-30min, dye liquor volume is 50-60ml.

6. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterised in that, the time of described dyeing is 10��30min.

7. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterised in that, in described air, the time of oxidation is 15��30min; The number of times of dual-staining oxidation is 3��8.

8. a kind of method utilizing graphite felt electrode indirect electrochemical vat dyeing according to claim 1, it is characterized in that, the condition of described soap boiling is: bath raio is 1:100��200, and the time, to be the standard soap flakes of 10��20min, 5g/L and the soda ash mixed dissolution of 5g/L soaped liquid as standard.