Process for purifying reactive dyes

Abstract

The application provides a purification process method of active dyes, and specifically comprises (1) a color paste pretreatment process; (2) an ultrafiltration desalination process; (3) a concentration treatment process; and (4) a content detection process. The application uses an ultrafiltration membrane to perform desalination treatment on the dyes, thereby avoiding the problems of low desalination efficiency and the inability to effectively intercept sulfate ions when a nanofiltration membrane is used. Meanwhile, in the application, the ultrafiltration membrane is negatively charged, and the active dyes generally contain acidic groups and are negatively charged, so that the electrostatic repulsion force is strong, the interception rate of the dyes is high, and the membrane has good anti-pollution performance. In addition, the process flow is low pressure first and high pressure later, and the dyes are concentrated at specific nodes, so that different ionic impurities of the active dyes obtain a best desalination effect, and the concentration treatment is realized by stopping the water supplement operation, so that the operation is simple, other concentration equipment does not need to be replaced, cost is saved, and the work efficiency is high.

Description

Technical Field

[0001] This invention relates to the technical field of desalting reactive dye pastes, and more specifically to a purification process for reactive dyes. Background Technology

[0002] In modern printing technology, reactive dyes are widely used in inkjet printing due to their rich colors and excellent printing effects. However, in the dye production process, in order to improve the dye's fixation rate, a large amount of inorganic salts such as sodium sulfate, sodium oxide, and potassium oxide are used and generated. The presence of these inorganic salts can easily affect the stability and accuracy of ink droplets, thereby affecting the resolution, color saturation, and durability of the printed pattern; on the other hand, they pose a risk of clogging the printhead during printing, causing damage to the printing equipment.

[0003] Existing purification processes mostly employ nanofiltration membranes. For example, CN102504648B uses a two-stage nanofiltration device to purify reactive dyes. However, nanofiltration membranes have a molecular weight cutoff range of 200 Daltons to 1000 Daltons, and pore sizes are generally between 0.002 micrometers and 0.1 micrometers. They have a higher rejection capacity for smaller molecules, resulting in a high sulfate rejection rate and low permeability, which is unsuitable for the current inkjet industry with high purity requirements. Ultrafiltration membranes typically have a molecular weight cutoff between 1,000 Daltons and 300,000 Daltons. Using ultrafiltration membranes for reactive dye purification results in larger pore sizes and higher desalination efficiency, but the purification effect is not as good, and ineffective desalination may occur, failing to meet the desalination requirements of dyes. Summary of the Invention

[0004] The purpose of this invention is to provide a purification process for reactive dyes, which solves the problem of low efficiency or inability to meet desalination requirements in existing dye desalination processes.

[0005] To achieve the purpose of this invention, a purification process for reactive dyes according to this invention includes the following steps: (1) Pretreatment of dye paste: The reactive dye is prepared into a reactive dye paste, and the reactive dye paste is passed through a pretreatment device. The pretreatment process includes at least degreasing treatment; (2) Ultrafiltration desalination process: The pretreated reactive dye paste is desalinated through an ultrafiltration membrane device. The ultrafiltration membrane in the ultrafiltration membrane device is negatively charged. Water replenishment is performed simultaneously during the desalination process in the ultrafiltration membrane device; (3) Concentration process: The concentration of ions in the reactive dye paste is detected. When the concentration of ions reaches a first preset value, the water replenishment operation is stopped, so that the reactive dye paste enters the concentration process; (4) Content detection process: The content of each ion in the reactive dye paste is detected. When the content of each ion reaches the desalination standard, the desalination process is ended, and the purified dye is obtained.

[0006] As can be seen from the above scheme, the present invention uses an ultrafiltration membrane to desalinate dyes, avoiding the problem of high sulfate ion rejection rate when using nanofiltration membranes. Furthermore, in this application, the ultrafiltration membrane is negatively charged, while reactive dyes generally contain acidic groups and are negatively charged. The strong electrostatic repulsion between the dye and the ultrafiltration membrane results in a high dye rejection rate and gives the membrane good antifouling properties. In addition, the inventors have discovered that during membrane separation, especially in pressure-driven membrane separation, a boundary layer with a high solute concentration forms near the membrane surface. When the boundary layer concentration exceeds the solubility of the solute, precipitation and scaling easily occur, significantly reducing desalination efficiency. The decline in high-valence salts (such as sulfate ions) is gradual. Concentrating the dye at this point ensures a dynamic balance between the accumulation of solute on the membrane surface and the rate of removal from the boundary layer. This stabilizes the thickness and concentration distribution of the boundary layer, accelerating the desalination of high-valence salts and achieving optimal desalination efficiency. During the ultrafiltration desalination process, a water replenishment operation is performed. The water flow rate must be set to ensure that the concentration of the reactive dye paste remains relatively constant. After the dye is dissolved and prepared into a dye paste, the concentration of the dye in the dye paste should be between 12% and 22%. Specifically, reactive dye dye pastes can be prepared at concentrations of 10%, 15%, and 20%.

[0007] The water replenishment operation ensures that the concentration of the reactive dye paste tends to a relatively stable value, with a small fluctuation range (not exceeding 3%). This ensures optimal matching with process conditions, achieving the best desalination effect and avoiding significant impact on membrane lifespan. Concentration is achieved by stopping the water replenishment operation, which is simple to operate, requires no replacement of other concentration equipment, saves costs, and is highly efficient.

[0008] A further approach is to run the ultrafiltration membrane device at a low pressure of 0.8MPa to 1MPa for a set time during the ultrafiltration desalination process, and then adjust it to a high pressure of 1.5MPa to 1.7MPa to continue operation.

[0009] As can be seen from the above scheme, the ultrafiltration membrane device starts with low-pressure operation followed by high-pressure operation, which can reduce wastewater generation and is environmentally friendly. This is mainly because the impurities in the dye system include both high-valent and low-valent salts. Low-valent salts easily pass through the membrane and are thus removed from the dye system, while high-valent salts, such as divalent and higher-valent ions, especially sulfate ions, are both divalent and anions. When using a negatively charged ultrafiltration membrane device for desalination and purification, they are more difficult to remove from the dye system. Therefore, this process selects low-pressure operation first. In low-pressure operation mode, low-valent salts can pass through the membrane and be removed from the dye system in a low-pressure, low-energy-consumption mode, and high-valent salts can also be partially removed. After a large amount of low-valent salts have been removed, the process switches to high-pressure operation mode for further removal of high-valent salts. This process setup can greatly improve desalination efficiency, thereby reducing wastewater generation. Furthermore, dye loss is also lower in low-pressure mode, thus reducing dye waste. Furthermore, using high pressure for desalination in the initial stage can easily form a high-concentration boundary layer on the membrane surface, increasing fluid resistance and local osmotic pressure, thereby reducing desalination efficiency and affecting the service life of the ultrafiltration membrane. Therefore, low-pressure desalination is adopted first. This is mainly to help the fluid form a tangential flow, preventing the active dye containing a large number of impurities from rushing into the ultrafiltration membrane under high pressure and passing through the membrane perpendicularly, causing particle accumulation on the membrane surface. Because the pore size of the ultrafiltration membrane is relatively large and the particle size of the dye is relatively small, too low a pressure will also result in ineffective desalination. Therefore, within the above-mentioned pressure range, the fluid can form a tangential flow while ensuring desalination efficiency.

[0010] A further proposed solution is to set the operating time at low pressure to 1 to 4 hours during the ultrafiltration desalination process, and to continue operating at high pressure for 0.5 to 2 hours.

[0011] As can be seen from the above scheme, the above time setting allows the various impurity ions such as anions, cations, high-valence salts, and low-valence salts in the reactive dye paste to achieve the best desalination effect.

[0012] A further approach is to detect the concentration of sulfate ions during the concentration process, with a first preset value between 400 ppm and 700 ppm. This preset value represents the concentration of the dye after it has been converted into dry powder.

[0013] As can be seen from the above scheme, since sulfate ions are the most difficult to remove from the system in actual desalination and purification processes, they are generally chosen as the ions to enter the concentration process. After multiple process verifications, an optimal desalination effect can be obtained when the sulfate content is between 400 ppm and 700 ppm, especially between 500 ppm and 600 ppm, during the dehydration and replenishment of reactive dye pastes, followed by concentration treatment. Furthermore, the reason for expressing concentration values ​​as dry powder is that the concentration of the dye may change slightly during the desalination process after the dye paste is prepared. Therefore, it is more accurate to convert the concentration of the dye paste to a dry powder state after taking a sample for measurement. For this reason, all experimental data of ions detected in the desalination and purification process of this application are converted to dry powder state concentration values.

[0014] A further option is to make the concentration of the reactive dye paste that has not undergone the concentration process 40% to 60% of the concentration of the reactive dye paste that has undergone the concentration process.

[0015] Specifically, the concentration of reactive dye paste is determined by spectral analysis, optionally using spectrophotometry, which utilizes the principle that the absorbance of a dye at a specific wavelength is proportional to its concentration to determine the dye concentration.

[0016] As can be seen from the above scheme, when ultrafiltration desalination reaches a certain point, the concentration of high-valent salts in reactive dye paste is already low. Therefore, the rate of decrease of high-valent salts is extremely slow. Thus, concentration treatment can accelerate the rate of decrease of high-valent salts, thereby achieving an optimal desalination and purification effect.

[0017] A further approach is to source the aqueous solution in the water replenishment operation from ultrafiltration wastewater generated during the concentration process. This ultrafiltration wastewater is collected by an ultrafiltration wastewater collection device and connected to the ultrafiltration membrane device for reuse.

[0018] A further option is to source the aqueous solution from an external water source during the water replenishment operation.

[0019] As can be seen from the above scheme, due to the initial desalination and purification, the low-valent salts are basically carried away with the wastewater, leaving mainly the high-valent salts that are difficult to remove. Furthermore, the salt ion concentration in the pigment paste system is relatively low at this stage. Therefore, when the system reaches the concentration stage, the main components of the ultrafiltration wastewater are a large amount of water and a small amount of dye. Recycling this ultrafiltration wastewater for use as a source of water in the makeup water operation of the desalination and purification process will, on the one hand, help maximize the resource utilization of water resources in the desalination process and reduce environmental pollution; on the other hand, it can also recover the dye from the ultrafiltration wastewater, achieving the recycling and reuse of dye resources. While ensuring desalination and purification efficiency, the dual recycling and reuse of water and dye resources promotes the sustainability of the process and also meets environmental protection requirements.

[0020] A further approach is to continue the concentration process of the reactive dye paste in the ultrafiltration membrane device when the content of each ion does not meet the desalination standard during the content detection process, until the content of each ion meets the desalination standard, at which point the concentration process ends.

[0021] A further option is to include an activated carbon adsorption device in the pretreatment process of the pigment paste.

[0022] As can be seen from the above scheme, the oily substances in the pigment paste are removed by activated carbon adsorption treatment, which increases the surface tension of the pigment paste and helps with subsequent desalination.

[0023] A further approach is to include a cation removal process after the pigment paste pretreatment process; the cation removal process involves passing the reactive dye pigment paste through an ion exchange device to remove cations.

[0024] As can be seen from the above scheme, cation exchange resin can remove hard ions such as calcium and magnesium ions, which is more conducive to the subsequent removal of anions. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the purification process of the reactive dyes of the present invention.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0027] See Figure 1 The purification process for reactive dyes provided by this invention includes the following steps:

[0028] (1) Color paste pretreatment process: The reactive dye is prepared into reactive dye color paste, and the reactive dye color paste is passed through a pretreatment device. The pretreatment process includes at least oil removal treatment, and the pretreatment device may include an activated carbon adsorption device.

[0029] (2) Ultrafiltration desalination process: The pretreated reactive dye paste is desalinated through an ultrafiltration membrane device. The ultrafiltration membrane in the ultrafiltration membrane device is negatively charged. Water replenishment is carried out simultaneously during the desalination process of the ultrafiltration membrane device. The ultrafiltration membrane device is first operated at a low pressure of 0.8MPa to 1MPa for a set time of 1h to 4h, and then adjusted to a high pressure of 1.5MPa to 1.7MPa for a further operation time of 0.5h to 2h.

[0030] (3) Concentration process: The concentration of ions in the reactive dye paste is detected. When the concentration of ions reaches the first preset value, the water replenishment operation is stopped, so that the reactive dye paste enters the concentration process.

[0031] The detected ion concentration is the sulfate ion concentration, with a first preset value between 500 ppm and 600 ppm. This preset value represents the concentration of the dye after conversion to dry powder. Because the dye concentration may change during the desalination process after the color paste is prepared, it is generally converted to the dry powder concentration value after measuring the color paste sample. The concentration of the reactive dye color paste without concentration treatment is 40% to 60% of the concentration of the reactive dye color paste after concentration treatment.

[0032] Specifically, the concentration of reactive dye paste is determined by spectral analysis, optionally using spectrophotometry, which utilizes the principle that the absorbance of a dye at a specific wavelength is proportional to its concentration to determine the dye concentration.

[0033] The sources of the aqueous solution in the water replenishment operation include ultrafiltration wastewater generated during the concentration process and / or external water sources. The ultrafiltration wastewater is collected by an ultrafiltration wastewater collection device and connected to the ultrafiltration membrane device for reuse. The flow rate of the water replenishment should be set to ensure that the concentration of the active pigment paste remains constant. After the dye is dissolved and prepared into a pigment paste, the concentration of the dye in the pigment paste is between 8% and 20%, and the concentration variation during the ultrafiltration desalination process does not exceed 3%.

[0034] (4) Content detection process: The content of each ion in the reactive dye paste is detected. When the content of each ion reaches the desalination standard, the desalination process ends and the purified dye is obtained. When the content of each ion does not reach the desalination standard, the reactive dye paste continues to be concentrated in the ultrafiltration membrane device until the content of each ion reaches the desalination standard, and then the concentration process ends. The specific desalination standard is the industry general standard, and the specific desalination standard is shown in Table 1 below.

[0035] The pretreatment process of pigment paste may also include a cation removal process; the cation removal process is as follows: the reactive dye pigment paste is passed through an ion exchange device to remove cations.

[0036] The present invention will be further described below with reference to embodiments and comparative examples.

[0037] Example 1

[0038] The purification process for reactive dyes provided in this embodiment includes the following steps:

[0039] (1) Color paste pretreatment process: The reactive dye color paste is passed through an activated carbon adsorption device to remove oil from the color paste and increase the surface tension of the color paste.

[0040] (2) Cation removal process: The reactive dye paste continues to pass through the ion exchange device, where cations such as calcium ions and magnesium ions are removed by the cation exchange resin;

[0041] (3) Ultrafiltration desalination process: The pretreated reactive dye paste is desalted through an ultrafiltration membrane device. At this time, the concentration of sulfate is 6187.422 ppm. The ultrafiltration membrane in the ultrafiltration membrane device is negatively charged. Water replenishment is carried out at the same time as the desalination process in the ultrafiltration membrane device. The ultrafiltration membrane device is first run at a low pressure of 0.8MPa to 1MPa for a set time of 1h to 2h, and then adjusted to a high pressure of 1.5MPa to 1.7MPa to continue running for 0.5h to 1.5h.

[0042] (4) Concentration process: The concentration of ions in the reactive dye paste, including the concentration of sulfate ions, is detected. When the concentration of ions reaches 500ppm to 550ppm, the water replenishment operation is stopped, allowing the reactive dye paste to enter the concentration process. The sources of the aqueous solution in the water replenishment operation include ultrafiltration wastewater generated during the concentration process and external water sources. The ultrafiltration wastewater is collected by an ultrafiltration wastewater collection device and connected to the ultrafiltration membrane device for reuse.

[0043] (5) Content detection process: When the concentration of the reactive dye paste that has not undergone the concentration process is 45% to 55% of the concentration of the reactive dye paste that has undergone the concentration process, the content of each ion in the reactive dye paste is detected. When the content of each ion reaches the desalination standard, the desalination process is ended and the purified dye is obtained. At this time, the content of sulfate ions in the dye is only 88.816 ppm.

[0044] Example 2

[0045] The steps are the same as in Example 1, except that the initial sulfate ion concentration is 186415.014 ppm.

[0046] The ultrafiltration membrane device is first operated at a low pressure of 0.8MPa to 1MPa for a set time of 2h to 4h, and then adjusted to a high pressure of 1.5MPa to 1.7MPa to continue operating for 1h to 2h.

[0047] The ultrafiltration desalination process includes a concentration process, which involves detecting the concentration of sulfate ions and stopping the water replenishment operation when the concentration of ions reaches 600 ppm to 650 ppm.

[0048] When the desalination process is completed, the purified dye is obtained. At this point, the sulfate ion content in the dye is only 91.027 ppm.

[0049] Comparative Example 1

[0050] The purification process for reactive dyes provided in this comparative example includes the following steps:

[0051] (1) Color paste pretreatment process: The reactive dye color paste is passed through an activated carbon adsorption device to remove oil from the color paste and increase the surface tension of the color paste.

[0052] (2) Cation removal process: The reactive dye paste continues to pass through the ion exchange device, where cations such as calcium ions and magnesium ions are removed by the cation exchange resin;

[0053] (3) Ultrafiltration desalination process: The pretreated reactive dye paste is desalted through an ultrafiltration membrane device. At this time, the concentration of sulfate is 6187.422 ppm. The ultrafiltration membrane in the ultrafiltration membrane device is negatively charged. Water replenishment is carried out at the same time as the desalination process in the ultrafiltration membrane device. The ultrafiltration membrane device is first run at a low pressure of 0.8MPa to 1MPa for a set time of 1h to 2h, and then adjusted to a high pressure of 1.5MPa to 1.7MPa to continue running for 0.5h to 1.5h.

[0054] (4) Content detection process: After the ultrafiltration membrane device operates at a high pressure of 1.5MPa to 1.7MPa for 0.5h to 1.5h, the content of each ion in the reactive dye paste is detected. When the content of most ions reaches the desalination standard and the content of sulfate ions is difficult to continue to decrease, the desalination process is ended and the purified dye is obtained. At this time, the content of sulfate ions in the dye is 317.362ppm.

[0055] It should be emphasized that the total process run time of Comparative Example 1 is consistent with that of Example 1.

[0056] The contents of each ion in the dyes before and after purification in Examples 1, 2 and Comparative Example 1 were detected. The cations were detected by atomic absorption spectrometry and the anions were detected by anion chromatography. The results are shown in Table 1 below.

[0057] Table 1

[0058]

[0059]

[0060]

[0061] It should be noted that in chromatographic test reports, "ND" usually stands for "Not Detected," meaning that the content of the indicator in the sample is below the minimum detection limit of the detection method. All ion concentration values ​​in the embodiments and comparative examples of this invention are concentration values ​​converted from reactive dye paste concentrations to dry powder concentrations.

[0062] As can be seen from Examples 1 and 2 in Table 1, the reactive dye purification process of the present invention achieves good desalination effect. Comparative Example 1, which did not undergo a concentration process during ultrafiltration desalination, still had a high concentration of sulfate ions in the final dye, failing to meet industry standards. The reactive dye purification process of the present invention, through a low-pressure followed by a high-pressure process flow and specific node concentration treatments, ensures a dynamic balance between the accumulation of solute on the membrane surface and its removal rate from the boundary layer. This stabilizes the thickness and concentration distribution of the boundary layer, resulting in a faster rate of decrease in high-valence salts after concentration, achieving optimal desalination. This solves the problems of slow decrease in high-valence salts and poor desalination effect due to prolonged continuous desalination, as well as excessive dye loss. Furthermore, the concentration treatment is achieved by stopping the water replenishment operation, simplifying the process and enhancing efficiency. Additionally, the ultrafiltration wastewater is recovered and used as an aqueous solution for the water replenishment operation, achieving resource recycling and being environmentally friendly.

[0063] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A purification process for reactive dyes, characterized in that, The purification process includes the following steps: (1) Color paste pretreatment process: The reactive dye is prepared into a reactive dye color paste, and the reactive dye color paste is passed through a pretreatment device. The pretreatment process includes at least an oil removal process. (2) Ultrafiltration desalination process: The pretreated reactive dye paste is desalinated through an ultrafiltration membrane device. The ultrafiltration membrane in the ultrafiltration membrane device is negatively charged. Water replenishment is performed simultaneously during the desalination process of the ultrafiltration membrane device. The ultrafiltration membrane device is first operated at a low pressure of 0.8MPa~1MPa for a set time, and then adjusted to a high pressure of 1.5MPa~1.7MPa to continue operating. The set time for operation at low pressure is 1h~4h; the time for operation at high pressure is 0.5h~2h. (3) Concentration process: The concentration of ions in the reactive dye paste is detected. When the concentration of the ions reaches the first preset value, the water replenishment operation is stopped, so that the reactive dye paste enters the concentration process. The concentration of the detected ions is the concentration of sulfate ions. The first preset value is between 400ppm and 700ppm. (4) Content detection process: The content of each ion in the reactive dye paste is detected. When the content of each ion reaches the desalination standard, the desalination process is ended and the purified dye is obtained.

2. The purification process for reactive dyes as described in claim 1, characterized in that: The concentration of reactive dye paste that has not undergone the concentration process is 40% to 60% of the concentration of reactive dye paste that has undergone the concentration process.

3. The purification process for reactive dyes as described in claim 1, characterized in that: The source of the aqueous solution in the water replenishment operation includes the ultrafiltration wastewater generated during the concentration process.

4. The purification process for reactive dyes as described in claim 1, characterized in that: The source of the aqueous solution in the water replenishment operation includes an external water source.

5. The purification process for reactive dyes as described in any one of claims 1 to 4, characterized in that: During the content detection process, if the content of each ion does not meet the desalination standard, the reactive dye paste continues to undergo the concentration process in the ultrafiltration membrane device until the content of each ion meets the desalination standard, at which point the concentration process ends.

6. The purification process for a reactive dye as described in any one of claims 1 to 4, characterized in that: In the pigment pretreatment process, the pretreatment device includes an activated carbon adsorption device.

7. The purification process for a reactive dye as described in any one of claims 1 to 4, characterized in that: The pigment pretreatment process also includes a cation removal process; The cation removal process is as follows: the reactive dye paste is passed through an ion exchange device to remove cations.

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