Method for decolorizing waste cotton-polyester blended fabric through cooperation of low-temperature plasma and chemical oxidation

Abstract

The invention relates to a method for decolorizing waste cotton-polyester blended fabric through low-temperature plasma synergistic chemical oxidation. Through the synergistic effect of low-temperature plasma and an acidic chemical oxidant (composed of inorganic acid, hydrogen peroxide, a penetrant and a hydrogen peroxide stabilizer), color development and auxochrome groups of dye on the waste polyester-cotton blended fabric are effectively destroyed, and efficient decolorization of the waste polyester-cotton blended fabric is achieved. According to the technical scheme, the decolorizing efficiency is improved, the original performance of polyester and cotton fibers can be reserved, the secondary utilization performance of the recycled waste polyester-cotton mixed textile fabric is guaranteed, and an effective means is provided for resource utilization of the waste polyester-cotton mixed textile fabric. Compared with a traditional chemical oxidation technology, the method has the advantages that the required acid amount and treatment time are remarkably reduced, the temperature required by the reaction is greatly reduced, the environmental protection performance is remarkably improved, the energy consumption is reduced, and an economic and green new way is provided for recycling the waste polyester-cotton mixed textiles.

Description

Technical Field

[0001] This invention relates to the field of decolorization technology for waste polyester-cotton blended textiles, and more specifically to a method for decolorizing waste polyester-cotton blended textiles using low-temperature plasma-assisted chemical oxidation. Background Technology

[0002] my country's textile industry is large-scale, with a complete industrial chain and abundant resources and technological advantages, playing a vital supporting role in the country's economic development and employment. However, with the continuous increase in textile consumption, the amount of waste textiles is also growing, leading to increasingly serious environmental pollution and resource waste. Polyester and cotton components are the most abundant in waste textiles, accounting for approximately 90.9% of the total fiber content. Since various dyes are often added during the production and use of waste textiles, this significantly impacts the performance of recycling and recycled products. Therefore, decolorization treatment of waste polyester-cotton blended textiles is of great importance.

[0003] Currently, various methods have been proposed for the decolorization of waste polyester-cotton blended textiles, such as ozone decolorization, alkaline high-temperature decolorization, and high-temperature swelling decolorization. However, each method has its limitations. Some decolorization methods use strong alkalis or other chemical reagents, which may lead to equipment corrosion and environmental pollution. For example, although sodium hydroxide (NaOH) is an easily recyclable alkali, its use still requires caution to avoid secondary pollution. During the decolorization process, some methods may cause changes in the properties of cellulose or polyester. For example, after treatment with alkaline high-temperature decolorization and high-temperature swelling decolorization, the chemical structure of polyester fibers is significantly damaged and the mechanical properties are significantly reduced, indicating that an inappropriate decolorization process may affect the final application of recycled materials. At the same time, the implementation of any decolorization technology is accompanied by energy consumption and potential cost issues, especially those methods that require high temperature, high pressure, or specific chemical reagents, which may lead to higher operating costs and energy consumption. With the increasing global emphasis on environmental protection and sustainable development, developing simpler, more efficient, environmentally friendly, and sustainable decolorization technologies for waste polyester-cotton blended textiles is a key direction for the development of green textiles. Summary of the Invention

[0004] Low-temperature plasma, as a green, economical, simple, and efficient technology, has been widely used in industrial production and environmental remediation. The purpose of this invention is to develop a method for efficient decolorization of waste polyester-cotton blended textiles based on low-temperature plasma synergistic chemical oxidation. This method aims to achieve efficient decolorization of waste polyester-cotton blended textiles through simple operation using low-energy-consumption, pollution-free low-temperature plasma technology, while ensuring the preservation of the fabric's original structure and properties during the decolorization process, thus facilitating direct reuse of the fabric.

[0005] To achieve the above objectives, this invention provides a method for decolorizing waste polyester-cotton blended fabrics using low-temperature plasma-assisted chemical oxidation, comprising the following steps:

[0006] The pretreated waste polyester-cotton blended textiles are placed in a low-temperature plasma device containing an acidic chemical oxidant, which includes inorganic acid, hydrogen peroxide, penetrant (fatty alcohol polyoxyethylene ether, abbreviated as JFC) and hydrogen peroxide stabilizer. After the low-temperature plasma device is turned on for decolorization treatment, the reacted polyester-cotton blended textiles are obtained.

[0007] The reacted polyester-cotton blend fabric is then ultrasonically cleaned.

[0008] Waste polyester-cotton blended textiles are recycled after drying.

[0009] Waste polyester-cotton blended textiles, after pretreatment steps such as washing and drying, are mixed with an acidic chemical oxidant solution of a certain concentration containing a combination of inorganic acid, hydrogen peroxide, penetrant and hydrogen peroxide stabilizer. The mixture is then placed in a plasma generator container at room temperature and pressure, and the decolorization reaction is carried out after aeration and the plasma power supply is turned on.

[0010] The decolorization technology for waste polyester-cotton blended fabrics based on low-temperature plasma synergistic chemical oxidation exhibits significant advantages in environmental friendliness, energy consumption control, and fiber protection. Firstly, compared to traditional chemical decolorization technologies, low-temperature plasma technology can be performed at room temperature or slightly above room temperature. Its energy input is significantly lower than traditional hot alkali reduction or high-temperature oxidation bleaching, and the reaction time is measured in minutes, making it far more efficient than biological enzymes or room-temperature oxidation systems. Secondly, the high-energy electrons, active species, and ultraviolet photons generated in situ by plasma act only on the fiber surface, synergistically destroying dye chromophores through physical etching and chemical oxidation. This thoroughly removes color while avoiding significant damage to the intrinsic strength of polyester and cotton, facilitating the rapid removal of dye molecules from the fabric surface by chemical agents, achieving highly efficient decolorization. Since pretreatment processes such as desizing, scouring, and multiple rinsing are eliminated, the process flow is greatly simplified, and the equipment footprint and chemical reagent consumption are simultaneously reduced. Meanwhile, plasma treatment introduces polar groups such as carboxyl and hydroxyl groups onto the fiber surface during the decolorization process, increasing the fabric's hydrophilicity. This results in better dye adsorption and color fastness during subsequent re-dyeing compared to untreated old fabric, creating conditions for the high-value reuse of waste textiles. In summary, low-temperature plasma decolorization, due to its comprehensive advantages of low consumption, low emissions, low loss, and functional enhancement, is a cutting-edge solution to replace the high-pollution, high-energy-consumption traditional decolorization methods. After the reaction is complete, the waste polyester-cotton blended textiles are removed from the mixed solution to terminate the reaction. Next, the waste polyester-cotton blended textiles are mixed with a certain amount of water and placed in an ultrasonic cleaning device for deep cleaning, and then dried in an oven.

[0011] Preferably, in the acidic chemical oxidant, the concentration, by mass, is: inorganic acid 0.1-10 g / L, hydrogen peroxide 1-20 g / L, penetrant (JFC) 1-5 g / L, hydrogen peroxide stabilizer 0.1-5 g / L, and the balance is deionized water. At this concentration, the inorganic acid... + At extremely low concentrations, it no longer possesses the ability to hydrolyze cotton fibers independently. Its function is to provide an acidic microenvironment in synergy with plasma: acidic conditions can significantly increase the oxidation potential of hydrogen peroxide, while simultaneously stabilizing the active species (such as ·OH) generated by the plasma, extending their lifetime and effective range. Meanwhile, low concentrations of H₂... + The inorganic acid can selectively protonate polar groups (such as -SO3H, -NH2) in dye molecules, weakening the binding force between the dye and the fiber, or making the dye molecules more susceptible to attack by subsequent oxide species. Therefore, this is actually an "activation" rather than a "fiber degradation" effect. Such a low concentration of inorganic acid greatly limits the diffusion of the acidic oxidation system into the fiber interior. The reaction is effectively controlled on the fiber surface and shallow layers. Combined with the directional penetration of the penetrant JFC (1-5g / L), the decolorization reaction occurs precisely on the fiber surface where dye molecules are concentrated, achieving a "precise attack" on the chromophores at the surface level without damaging the fiber's crystalline region or bulk structure. Furthermore, the corrosiveness of the inorganic acid at a concentration of 0.1-10g / L has been reduced to an extremely low level, significantly reducing the material requirements for the reaction equipment, extending equipment life, and completely eliminating the risk of acid-catalyzed side reactions in the fiber under high-temperature, strong acid conditions, ensuring the whiteness, hand feel, and mechanical properties of the decolorized fabric. Furthermore, hydrogen peroxide at a concentration of 1-20 g / L serves as the primary oxidant, which is efficiently activated under plasma and acidic conditions, generating a large number of highly reactive ·OH free radicals that specifically attack the chromophores of the dye. A 1-5 g / L concentration of penetrant JFC ensures that it effectively reduces the surface tension of the reaction solution, promoting uniform spreading and penetration of the agent on the fabric surface, without generating excessive foam due to excessive dosage, thus avoiding interference with uniform plasma discharge. A 0.1-5 g / L stabilizer effectively complexes heavy metal ions, preventing ineffective decomposition of H2O2 and ensuring that oxidation occurs stably and continuously at the locations where decolorization is most needed.

[0012] Preferably, the inorganic acid is one of sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, nitric acid, and carbonic acid, and the hydrogen peroxide stabilizer is one of sodium silicate, sodium ethylenediaminetetraacetate (EDTA), and magnesium silicate. This choice of inorganic acid allows for flexible selection of the most suitable acid based on factors such as cost, equipment corrosion resistance, and wastewater treatment requirements during actual production, greatly enhancing the industrial adaptability and scalability of the process. Sodium silicate, EDTA, and magnesium silicate are preferred as hydrogen peroxide stabilizers because hydrogen peroxide is prone to ineffective decomposition in the high-energy environment of low-temperature plasma. Introducing these stabilizers effectively complexes metal ions and inhibits the chain reaction of free radicals, ensuring a stable and continuous release of active oxygen during plasma treatment, thereby guaranteeing the uniformity and repeatability of the decolorization effect. This preferred combination of acid and stabilizer, together with the penetrant JFC and hydrogen peroxide, constitutes a highly synergistic "mild oxidation bath." Whether strong acids (sulfuric acid, hydrochloric acid) or weak acids (boric acid, carbonic acid), at ultra-low concentrations of 0.1-10 g / L, the plasma reaction can precisely provide the necessary acidic microenvironment to activate dye molecules without damaging the fiber itself. The presence of stabilizers prevents localized peroxidation, further ensuring that the decolorization process only acts on the fiber surface, achieving the excellent effect of "decolorization without damaging the fiber".

[0013] Preferably, the operating voltage of the low-temperature plasma device is 20kV, and the introduced gas is one or two of argon, carbon dioxide, nitrogen, oxygen, and air. Preferably, the introduced gas in the low-temperature plasma system is argon and oxygen. At this voltage, the plasma discharge intensity and uniformity achieve an ideal balance, generating sufficient high-energy electrons and active particles to efficiently destroy dye chromophores while avoiding arc discharge or excessive etching of the fiber body that may result from excessively high voltage, thus balancing decolorization efficiency and fiber protection. The different choices of the introduced gas are mainly based on flexibly switching the decolorization mechanism for waste fabrics of different colors and compositions. Inert gases (such as argon) dominate physical bombardment, while active gases (such as oxygen) dominate chemical oxidation; any combination of the two provides a diverse range of process options for treating fabrics with different colorfastness. The combination of argon and oxygen introduced into the plasma system is effective because argon, as an inert gas, allows its metastable atoms to efficiently transfer energy to oxygen molecules, promoting oxygen dissociation and generating more and more active oxygen-reactive species (such as oxygen atoms, ozone, and hydroxyl radicals). This synergistic mechanism of "argon physical activation + oxygen chemical oxidation" achieves a 1+1>2 effect, significantly improving decolorization efficiency and treatment uniformity, while shortening treatment time, reducing energy consumption, and ensuring the integrity and excellent whiteness of the treated fabric.

[0014] Preferably, the processing time of the low-temperature plasma device is 1-5 hours. By precisely controlling parameters such as decolorization time, the decolorization effect is improved, energy consumption and cost are reduced, and over-processing that could damage the fibers is avoided. Within the aforementioned time frame, an optimal balance between efficiency and protection is achieved, efficiently destroying dye chromophores while preserving the original structure and properties of the fabric, thus balancing treatment effectiveness with energy consumption control.

[0015] Preferably, the ultrasonic cleaning temperature is 50-70℃, and the time is 10-30 minutes. Before ultrasonic cleaning, hot water at 100℃ is added to the mixture after the reaction to terminate the degradation reaction. By optimizing the temperature and time of ultrasonic cleaning, dirt and grease on the fiber surface can be effectively removed while avoiding thermal damage to the fibers caused by excessively high temperatures, further improving the decolorization effect. Setting the time to 10-30 minutes can prevent over-cleaning from affecting the fiber structure and feel.

[0016] Preferably, the cotton fiber content in the waste polyester-cotton blended fabric is 1-99 wt%. This invention covers almost all common polyester-cotton blend ratios, demonstrating the wide adaptability of the method to raw materials. Regardless of the cotton fiber content, efficient decolorization and complete preservation of the fiber structure can be achieved under a low-temperature plasma-assisted chemical oxidation system, avoiding the limitations of traditional methods that require process adjustments based on different cotton contents.

[0017] Preferably, the drying process includes the following steps: placing the ultrasonically cleaned polyester-cotton blended fabric in a constant-temperature forced-air drying oven at 105°C for 4 hours. In these embodiments, drying at 105°C for 4 hours ensures that the fabric is thoroughly dried to a constant weight, facilitating accurate subsequent weighing and performance testing. This temperature balances drying efficiency with fiber protection, avoiding excessively high temperatures that could lead to fiber thermal degradation or yellowing, and ensuring the structural integrity and whiteness stability of the fabric after decolorization.

[0018] Preferably, the amount of acidic chemical oxidant added is 0.1-9 mL / g fabric. This range of addition can take into account the treatment requirements of different colors and components. The low amount ensures sufficient wetting reaction, while the high amount meets the decolorization requirements of dark fabrics, thus minimizing the consumption of reagents and waste liquid discharge while ensuring the decolorization effect.

[0019] Unlike existing technologies, the above-mentioned technical solution introduces low-temperature plasma as the core processing method. It utilizes high-energy active particles to physically etch and chemically oxidize dye molecules on the fiber surface, rather than attacking the glycosidic bonds or macromolecular chains of the fiber itself. The penetrant JFC works synergistically with the plasma. The plasma is responsible for surface activation and dye degradation, while JFC promotes the action of low-concentration acidic oxidants (inorganic acid + hydrogen peroxide) on dyes and impurities only on the fiber surface, rather than penetrating into the fiber interior for destruction. Through the synergistic effect of low-temperature plasma and the acidic system composed of inorganic acid, hydrogen peroxide, penetrant JFC, and hydrogen peroxide stabilizer, the chromophores and auxochromes of dyes on waste polyester-cotton blended fabrics are effectively destroyed. This ensures that the bulk structure and degree of polymerization of both polyester and cotton fibers are fully preserved. The decolorized fabric retains its original mechanical strength and textile feel, laying the foundation for direct reweaving or high-value utilization. The above-mentioned technical solution improves decolorization efficiency, helps preserve the original properties of polyester and cotton fibers, and ensures the secondary utilization performance of recycled waste polyester-cotton blended textiles, providing an effective means for the resource utilization of waste polyester-cotton blended textiles. This invention not only significantly reduces the amount of acid and processing time required, but also greatly lowers the reaction temperature. Relying on the high-energy activity of plasma, the entire decolorization process can be carried out at room temperature and pressure, eliminating dependence on high-temperature and high-pressure equipment, significantly reducing energy consumption and operating costs, greatly improving the safety of the production process, significantly enhancing environmental performance, and reducing energy consumption, providing an economical and green new approach for the recycling and reuse of waste polyester-cotton blended textiles. Attached Figure Description

[0020] Figure 1 The images show a comparison of waste polyester-cotton blended textiles with different polyester-cotton contents and colors before and after decolorization following the reaction method of this invention.

[0021] Figure 2 This is a comparison chart of the whiteness of waste polyester-cotton blended textiles with different polyester-cotton contents and colors before and after decolorization following the reaction method of this invention.

[0022] Figure 3 This is a comparison chart of Fourier transform infrared (FTIR) spectra of waste polyester-cotton blended textiles with different polyester-cotton contents and colors before and after decolorization following the reaction method of this invention.

[0023] Figure 4 The image shows a comparison of X-ray diffraction (XRD) analysis of waste polyester-cotton blended textiles with different polyester-cotton contents and colors before and after decolorization following the reaction method of this invention.

[0024] Figure 5A comparison image of waste polyester-cotton blended fabrics obtained without low-temperature plasma-assisted decolorization and waste polyester-cotton blended fabrics obtained with low-temperature plasma-assisted decolorization. Detailed Implementation

[0025] To explain in detail the technical content, structural features, objectives, and effects of the technical solution, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0026] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0027] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0028] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0029] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0030] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0031] Similar to the interpretation in the Patent Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also interpreted in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0032] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0033] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0034] The various instruments, equipment, raw materials, or reagents used in the specific embodiments of this invention are not limited in their source; they are all conventional products that can be purchased through legitimate commercial channels and can be prepared according to conventional methods well known to those skilled in the art. The waste polyester-cotton blended raw materials used in the following embodiments are waste fabrics recycled from factories. Unless otherwise specified, the chemical reagents used in the following embodiments are commercially available and of analytical grade. Unless otherwise specified, the operations or instruments used in the following embodiments are common operations or instruments in the art. Unless otherwise specified, the proportions, ratios, contents, etc., mentioned in the following embodiments are weight ratios. The decolorization rate refers to the ratio of the difference between the K / S value of the fabric before decolorization and the K / S value of the fabric after decolorization to the K / S value of the fabric before decolorization.

[0035] The whiteness test was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers" using an FFiber-Whiteness whiteness meter. The whiteness of the samples was measured at four different locations for each sample. The experiment was repeated three times, and the average value of every three samples was taken.

[0036] Furthermore, the method of the present invention does not require high reaction temperatures or large amounts of expensive solvents, but mainly uses gas as the reaction medium, which helps to reduce decolorization costs, improve production efficiency, and realize the recycling and reuse of truly "green and environmentally friendly" polyester-cotton blended textiles.

[0037] Example 1

[0038] A certain amount of waste polyester-cotton blended fabric raw material with a cotton content between 50% and 99% was thoroughly washed with water, cut into pieces of approximately 8cm × 8cm, dried thoroughly in an oven, and then dried to constant weight in a desiccator to obtain the pretreated waste polyester-cotton blended fabric. 2.5mL of an acidic chemical oxidant—a decolorizing agent—comprising 2g / L sulfuric acid, 10g / L hydrogen peroxide, 1.2g / L sodium silicate, and 2g / L penetrant (JFC) was added to the fabric. The mixture was then placed in a low-temperature plasma reactor, through which 0.001% argon gas and 99.999% oxygen gas were introduced. The reaction time was 2 hours, during which the decolorization reaction of the waste polyester-cotton blended fabric was completed.

[0039] Example 2

[0040] The difference from Example 1 is that the waste polyester-cotton blended fabric raw material used has a cotton content between 1% and 50%, and the amount of acidic chemical oxidant decolorizing agent added is 4 mL. Other operating steps and parameters are the same as in Example 1.

[0041] Example 3

[0042] The difference from Example 1 is that the oxygen concentration introduced is 20%. All other operating steps and parameters are the same as in Example 1.

[0043] Example 4

[0044] The difference from Example 1 is that the oxygen concentration introduced is 40%. All other operating steps and parameters are the same as in Example 1.

[0045] Example 5

[0046] The difference from Example 1 is that the oxygen concentration introduced is 60%. All other operating steps and parameters are the same as in Example 1.

[0047] Example 6

[0048] The difference from Example 1 is that the oxygen concentration introduced is 80%. All other operating steps and parameters are the same as in Example 1.

[0049] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization, as used in Examples 1, 3-6. The decolorization rate was used as the evaluation index, with an oxygen concentration of 99.999% showing the best decolorization effect, resulting in a decolorization rate of over 30.6% for the decolorized waste polyester-cotton fabric. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers," using an FFiber-Whiteness whiteness meter to measure the whiteness of the samples. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average whiteness of every three samples was taken. The average whiteness was above 8.35, indicating that the whiteness of the decolorized waste polyester-cotton fabric was more than 1.1 times that of the original waste polyester-cotton fabric.

[0050] Example 7

[0051] The difference from Example 1 is that the amount of acidic decolorizing agent added is 1.0 mL. All other operating steps and parameters are the same as in Example 1.

[0052] Example 8

[0053] The difference from Example 1 is that the amount of acidic decolorizing agent added is 1.5 mL. All other operating steps and parameters are the same as in Example 1.

[0054] Example 9

[0055] The difference from Example 1 is that the amount of acidic decolorizing agent added is 2.0 mL. All other operating steps and parameters are the same as in Example 1.

[0056] Example 10

[0057] The difference from Example 1 is that the amount of acidic decolorizing agent added is 3.0 mL. All other operating steps and parameters are the same as in Example 1.

[0058] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization. This ratio was used to evaluate the decolorization rate of waste polyester-cotton fabrics obtained in Examples 1, 7-10. The optimal decolorization effect was achieved with 2.5 mL of acidic decolorizing agent, resulting in a decolorization rate of over 38.7% for the waste polyester-cotton fabrics. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers" using an FFiber-Whiteness whiteness meter. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average whiteness of three samples was taken. The average whiteness was above 10.55, indicating that the whiteness of the decolorized waste polyester-cotton fabric was more than 1.5 times that of the original waste polyester-cotton fabric.

[0059] Example 11

[0060] The difference from Example 1 is that the low-temperature plasma treatment time is 1 hour. All other operating steps and parameters are the same as in Example 1.

[0061] Example 12

[0062] The difference from Example 1 is that the low-temperature plasma treatment time is 3 hours. All other operating steps and parameters are the same as in Example 1.

[0063] Example 13

[0064] The difference from Example 1 is that the low-temperature plasma treatment time is 4 hours. All other operating steps and parameters are the same as in Example 1.

[0065] Example 14

[0066] The difference from Example 1 is that the low-temperature plasma treatment time is 5 hours. All other operating steps and parameters are the same as in Example 1.

[0067] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization. This ratio was used to evaluate the decolorization rate of waste polyester-cotton fabrics obtained in Examples 1, 11-14. The optimal decolorization effect was achieved with a low-temperature plasma treatment time of 2 hours, resulting in a decolorization rate of over 45.3% for the waste polyester-cotton fabrics. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers" using an FFiber-Whiteness whiteness meter. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average whiteness of three samples was taken. The average whiteness was above 12.35, indicating that the whiteness of the decolorized waste polyester-cotton fabric was more than 2.1 times that of the original waste polyester-cotton fabric.

[0068] Example 15

[0069] The difference from Example 2 is that the oxygen concentration introduced is 20%. All other operating steps and parameters are the same as in Example 2.

[0070] Example 16

[0071] The difference from Example 2 is that the oxygen concentration introduced is 40%. All other operating steps and parameters are the same as in Example 2.

[0072] Example 17

[0073] The difference from Example 2 is that the oxygen concentration introduced is 60%. All other operating steps and parameters are the same as in Example 2.

[0074] Example 18

[0075] The difference from Example 2 is that the oxygen concentration introduced is 80%. All other operating steps and parameters are the same as in Example 2.

[0076] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization, as used in Examples 2, 15-18. The decolorization rate was used as the evaluation index, with an oxygen concentration of 99.999% showing the best decolorization effect, resulting in a decolorization rate of over 29.6% for the decolorized waste polyester-cotton fabric. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers," using an FFiber-Whiteness whiteness meter to measure the whiteness of the samples. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average whiteness of every three samples was taken. The average whiteness was above 18.27, indicating that the whiteness of the decolorized waste polyester-cotton fabric was more than 1.1 times that of the original waste polyester-cotton fabric.

[0077] Example 19

[0078] The difference from Example 2 is that the amount of acidic decolorizing agent added is 2 mL. All other operating steps and parameters are the same as in Example 2.

[0079] Example 20

[0080] The difference from Example 2 is that the amount of acidic decolorizing agent added is 3 mL. All other operating steps and parameters are the same as in Example 2.

[0081] Example 21

[0082] The difference from Example 2 is that the amount of acidic decolorizing agent added is 5 mL. All other operating steps and parameters are the same as in Example 2.

[0083] Example 22

[0084] The difference from Example 2 is that the amount of acidic decolorizing agent added is 6 mL. All other operating steps and parameters are the same as in Example 2.

[0085] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization, as used in Examples 2, 19-22. The decolorization rate was used as the evaluation index, with 4 mL of acidic decolorizing agent showing the best decolorization effect, resulting in a decolorization rate of over 48.7% for the decolorized waste polyester-cotton fabric. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers," using an FFiber-Whiteness whiteness meter to measure the whiteness of the samples. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average whiteness of three samples was taken. The average whiteness was 30.1, indicating that the whiteness of the decolorized waste polyester-cotton fabric was more than 1.1 times that of the original waste polyester-cotton fabric.

[0086] Example 23

[0087] The difference from Example 2 is that the low-temperature plasma treatment time is 1 hour. All other operating steps and parameters are the same as in Example 2.

[0088] Example 24

[0089] The difference from Example 2 is that the low-temperature plasma treatment time is 3 hours. All other operating steps and parameters are the same as in Example 2.

[0090] Example 25

[0091] The difference from Example 2 is that the low-temperature plasma treatment time is 4 hours. All other operating steps and parameters are the same as in Example 2.

[0092] Example 26

[0093] The difference from Example 2 is that the low-temperature plasma treatment time is 5 hours. All other operating steps and parameters are the same as in Example 2.

[0094] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization, as used in Examples 2, 23-26. The decolorization rate was used as the evaluation index, with the optimal decolorization effect achieved by a 2-hour low-temperature plasma treatment, resulting in a decolorization rate of over 51.7% for the decolorized waste polyester-cotton fabric. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers," using an FFiber-Whiteness whiteness meter. Measurements were taken at four different locations for each sample. The experiment was repeated three times, with the average whiteness of three samples taken. The average whiteness was above 31.99, indicating that the whiteness of the decolorized waste polyester-cotton fabric was more than 1.4 times that of the original waste polyester-cotton fabric.

[0095] The test results of the average decolorization rate and average whiteness of the waste polyester-cotton fabrics in Examples 1-26 are shown in Table 1.

[0096] Table 1. Test results of average decolorization rate and average whiteness of waste polyester-cotton fabrics in Examples 1-26.

[0097]

[0098] Example 27

[0099] The difference from Example 1 is that sulfuric acid is replaced with hydrochloric acid. All other operating steps and parameters are the same as in Example 1.

[0100] Example 28

[0101] The difference from Example 2 is that sulfuric acid is replaced with hydrochloric acid. All other operating steps and parameters are the same as in Example 2.

[0102] Example 29

[0103] The difference from Example 1 is that sulfuric acid is replaced with phosphoric acid. All other operating steps and parameters are the same as in Example 1.

[0104] Example 30

[0105] The difference from Example 2 is that sulfuric acid is replaced with phosphoric acid. All other operating steps and parameters are the same as in Example 2.

[0106] Example 31

[0107] The difference from Example 1 is that sulfuric acid is replaced with boric acid. All other operating steps and parameters are the same as in Example 1.

[0108] Example 32

[0109] The difference from Example 2 is that sulfuric acid is replaced with boric acid. All other operating steps and parameters are the same as in Example 2.

[0110] Example 33

[0111] The difference from Example 1 is that sulfuric acid is replaced with nitric acid. All other operating steps and parameters are the same as in Example 1.

[0112] Example 34

[0113] The difference from Example 2 is that sulfuric acid is replaced with nitric acid. All other operating steps and parameters are the same as in Example 2.

[0114] Example 35

[0115] The difference from Example 1 is that sulfuric acid is replaced with carbonic acid. All other operating steps and parameters are the same as in Example 1.

[0116] Example 36

[0117] The difference from Example 2 is that sulfuric acid is replaced with carbonic acid. All other operating steps and parameters are the same as in Example 2.

[0118] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization, as used in Examples 1, 2, and 27-36. The decolorization rate was used as the evaluation index, with sulfuric acid showing the best decolorization effect, achieving a decolorization rate of over 84.3% for the waste polyester-cotton fabric. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers," using an FFiber-Whiteness whiteness meter to measure the whiteness of the samples. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average value was taken for every three samples. The whiteness of the decolorized waste polyester-cotton fabric was more than 1.4 times that of the undecolorized waste polyester-cotton fabric.

[0119] Example 37

[0120] The difference from Example 1 is that sodium silicate is replaced with sodium ethylenediaminetetraacetate (EDTA). All other operating steps and parameters are the same as in Example 1.

[0121] Example 38

[0122] The difference from Example 2 is that sulfuric acid was replaced with sodium ethylenediaminetetraacetate (EDTA). All other operating steps and parameters were performed in accordance with Example 2.

[0123] Example 39

[0124] The difference from Example 1 is that sulfuric acid is replaced with magnesium silicate. All other operating steps and parameters are the same as in Example 1.

[0125] Example 40

[0126] The difference from Example 2 is that sulfuric acid is replaced with magnesium silicate. All other operating steps and parameters are the same as in Example 2.

[0127] The decolorization rate was calculated based on the ratio of the difference between the K / S value of the fabric before and after decolorization to the K / S value of the fabric before decolorization, as used in Examples 1, 2, 37-40. The decolorization rate was used as the evaluation index, with sodium silicate showing the best decolorization effect, achieving a decolorization rate of over 86.4% for the decolorized waste polyester-cotton fabric. Whiteness testing was conducted according to GB / T 17644-2008 "Test Methods for Whiteness and Color of Textile Fibers," using an FFiber-Whiteness whiteness meter to measure the whiteness of the samples. Measurements were taken at four different locations for each sample. The experiment was repeated three times, and the average value of three samples was taken. The whiteness of the decolorized waste polyester-cotton fabric was more than 1.3 times that of the undecolorized waste polyester-cotton fabric.

[0128] Comparative Example 1

[0129] A certain amount of waste polyester-cotton blended fabric raw material with a cotton content between 50% and 99% was thoroughly washed with water, cut into pieces approximately 8cm × 8cm in size, dried thoroughly in an oven, and then dried to constant weight in a desiccator to obtain the pretreated waste polyester-cotton blended fabric. 2.5mL of an acidic decolorizing agent consisting of 2g / L sulfuric acid, 10g / L hydrogen peroxide, 1.2g / L sodium silicate, and 2g / L penetrant (JFC) was added to the fabric. The reaction time was 2 hours to complete the decolorization reaction of the waste polyester-cotton blended fabric, and the decolorization process was observed. Please refer to... Figure 5 A comparison chart of waste polyester-cotton blended fabrics obtained without low-temperature plasma-assisted decolorization and waste polyester-cotton blended fabrics obtained with low-temperature plasma-assisted decolorization shows that, compared with Example 1, the fabric treated with Comparative Example 1 has a decolorization efficiency of almost 0% without low-temperature plasma assistance. This indicates that the decolorization of waste polyester-cotton blended textiles based on low-temperature plasma assistance and synergistic chemical oxidation of the present invention is quite effective.

[0130] As can be seen from the above embodiments, the preferred process for decolorizing waste polyester-cotton blended textiles based on an acidic system under low-temperature plasma assistance is as follows: (1) For polyester-cotton blended textiles with a cotton content higher than 50%, a composite acidic solution composed of 2 g / L sulfuric acid, 10 g / L hydrogen peroxide, 1.2 g / L sodium silicate and 2 g / L penetrant (JFC) is used to decolorize the waste polyester-cotton blended textiles. The amount of decolorizing agent solution added is 2.5 mL, the oxygen concentration is 99.999%, and the reaction time is preferably 2 h; (2) For polyester-cotton blended textiles with a cotton content lower than 50%, a composite acidic solution composed of 2 g / L sulfuric acid, 10 g / L hydrogen peroxide, 1.2 g / L sodium silicate and 2 g / L penetrant (JFC) is used to decolorize the waste polyester-cotton blended textiles. The amount of decolorizing agent solution added is 4 mL, the oxygen concentration is 99.999%, and the reaction time is preferably 2 h. The waste polyester-cotton textiles processed by this invention have a cotton fiber content of 1%-99%, which means they are applicable to most polyester-cotton blended textiles.

[0131] Waste polyester-cotton textiles obtained after decolorization in Examples 1 and 2 were subjected to Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) tests. Please refer to [link to relevant documentation]. Figure 1 Images showing the color-changing effects of waste polyester-cotton textiles with different component contents. Figure 2 Comparison of whiteness of waste polyester-cotton textiles before and after bleaching with three different component contents. Figure 3 Comparison of Fourier Transform Infrared (FTIR) spectra of waste polyester-cotton textiles with three different component contents before and after bleaching. Figure 4 Comparison of X-ray diffraction (XRD) images of three fabrics with different component contents before and after decolorization shows that the treated waste polyester-cotton textiles were effectively decolorized, and the fabrics remained intact. Figure 1 ), and the whiteness is significantly improved ( Figure 2 ).

[0132] Please see Figure 3 The Fourier transform infrared (FTIR) spectra of waste polyester-cotton textiles before and after the reaction are shown in the comparison. It can be seen that no new peaks appeared and no old peaks disappeared in the infrared curves before and after decolorization, indicating that the structure of the waste polyester-cotton textiles after decolorization was basically unchanged compared with that before decolorization. Figure 3 ).

[0133] Please see Figure 4 The X-ray diffraction (XRD) comparison diagrams of waste polyester-cotton textiles before and after the reaction show that no new peaks appeared and no old peaks disappeared in the X-ray diffraction peaks before and after decolorization, indicating that the structure of the waste polyester-cotton textiles after decolorization has not changed compared with that before decolorization. Figure 4 ).

[0134] Therefore, the chemical structure of waste polyester-cotton fabrics after low-temperature plasma-assisted treatment is consistent with that of the fabrics before treatment.

[0135] In summary, the component decolorization method for waste polyester-cotton blended textiles of the present invention is simple, efficient, low-cost, and environmentally friendly. The decolorization rate of waste polyester-cotton blended textiles reaches over 80.1%, and the whiteness is increased by more than 2.1 times. It is an ideal and highly efficient decolorization method for waste polyester-cotton blended textiles.

[0136] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, any changes and modifications made to the embodiments described herein based on the innovative concept of the present invention, or equivalent structural or procedural transformations made using the content of the present invention's specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included within the scope of patent protection of the present invention.

Claims

1. A method for decolorizing waste polyester-cotton blended fabrics using low-temperature plasma-assisted chemical oxidation, characterized in that, Includes the following steps: The pretreated waste polyester-cotton blended textile is placed in a low-temperature plasma device containing an acidic chemical oxidant, which includes an inorganic acid, hydrogen peroxide, a penetrant JFC, and a hydrogen peroxide stabilizer. After the low-temperature plasma device is turned on for decolorization treatment, the reacted polyester-cotton blended fabric is obtained. The reacted polyester-cotton blended fabric is then ultrasonically cleaned. Waste polyester-cotton blended fabrics are recycled after drying.

2. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, In the acidic chemical oxidant, the concentration of inorganic acid is 0.1-10 g / L, the concentration of hydrogen peroxide is 1-20 g / L, the concentration of penetrant is 1-5 g / L, and the concentration of hydrogen peroxide stabilizer is 0.1-5 g / L, by mass concentration.

3. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The inorganic acid is one of sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, nitric acid, and carbonic acid, and the hydrogen peroxide stabilizer is one of sodium silicate, sodium ethylenediaminetetraacetate (EDTA), and magnesium silicate.

4. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The operating voltage of the cryogenic plasma device is 20kV, and the gas introduced is one or two of the following: argon, carbon dioxide, nitrogen, oxygen, and air.

5. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The processing time of the low-temperature plasma device is 1-5 hours.

6. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The ultrasonic cleaning temperature is 50-70℃ and the time is 10-30 minutes.

7. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The cotton fiber content in the waste polyester-cotton blended fabric is 1-99 wt%.

8. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The drying temperature is 105℃ and the time is 4 hours.

9. The method for decolorizing waste polyester-cotton blended fabrics according to claim 1, characterized in that, The amount of acidic chemical oxidant added is 0.1-9 mL / g of the pretreated waste polyester-cotton blended textile.

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