System and method for biologically separating blended fabric

Abstract

The invention provides a method for treating PET (Polyethylene Terephthalate) and cotton blended fabric waste. The method comprises an ultrasonic pretreatment step and an enzyme hydrolysis step, according to the method, PET and cotton in the fabric waste are separated from each other. The invention further provides a system for implementing the method.

Description

Technical Field

[0001] This disclosure relates to a method and system for treating textile waste, and more specifically, to a biological method and system for using ultrasonic pretreatment and enzymatic hydrolysis of blended textile materials of polyethylene terephthalate (PET) and cotton, said method separating the PET and cotton phases in the textile waste. Background Technology

[0002] Textile waste has become one of the most pressing concerns for most countries, evolving into an environmental crisis. It is estimated that 92 million tons of textile waste are sent to landfills globally each year, and this number continues to rise. In fact, textile materials take a very long time to decompose in landfills. During decomposition, the waste produces greenhouse gases and toxic substances. These toxic substances are released into groundwater and surrounding soil. Polyesters such as polyethylene terephthalate (PET) and cotton are very common textile materials. Over 75% of the world's fabrics are made from PET, cotton, and PET / cotton blends. Therefore, textile recycling technologies have been developed to address the increasing volume of textile waste, especially PET and cotton.

[0003] Hydrothermal treatment is a common chemical method for separating PET / cotton blended textile materials into PET and cellulose powder. The PET and cellulose powder recovered from hydrothermal treatment are reusable, achieving the goal of "end-to-end recycling," which transforms post-consumer textiles into raw materials for the production cycle. However, with the increasing volume of textile waste, it is crucial to explore multiple solutions for collecting and recycling PET and cotton.

[0004] A biological approach utilizing enzymatic hydrolysis has been developed in a HKRITA-supported project. Experimental results are promising and positive; however, a pre-industrial-scale system is needed to develop an industrial-scale biological treatment process. Summary of the Invention

[0005] To address the problems existing in the prior art, this disclosure provides a biological method for the enzymatic hydrolysis and recycling of textile waste materials using ultrasonic pretreatment, and a system for implementing this biological method (more suitable for pre-industrial scale). In this biological method, cotton in blended textiles is hydrolyzed and converted into glucose, and PET is collected and recycled.

[0006] According to one aspect, this disclosure provides a method for treating PET and cotton blended fabric waste, the method comprising:

[0007] (1) Ultrasonic pretreatment steps; and

[0008] (2) Enzymatic hydrolysis step;

[0009] The method separates the PET and cotton phases in textile waste.

[0010] According to some embodiments, in the method for treating textile waste, the enzymes used in the enzymatic hydrolysis step include, but are not limited to, cellulase and glucosidase, such as neutral polishing enzyme.

[0011] According to some embodiments, in the method for treating textile waste, the pH value of the reaction solution in the enzymatic hydrolysis step is 3 to 7 (preferably 4-6).

[0012] According to some embodiments, in the method for treating textile waste, in the enzymatic hydrolysis step, the reaction temperature is between 20°C and 70°C, preferably between 30°C and 60°C; the reaction time is between 8 hours and 72 hours, preferably 12-24 hours; and / or the enzyme content in the reaction solution is 0.1-20 wt% (preferably 1-10 wt%).

[0013] According to some embodiments, in the method for treating textile waste, the buffer solution added in the enzymatic hydrolysis step is a citrate-sodium citrate buffer solution with a concentration of 0.001M-0.1M.

[0014] According to some embodiments, the method for treating textile waste further includes:

[0015] (3) First filtration step to remove PET from the reaction solution to obtain a cellulose-glucose mixture.

[0016] According to some embodiments, the method for treating textile waste further includes:

[0017] (4) The second filtration step separates the cellulose powder and glucose solution in the cellulose-glucose mixture and filters out the glucose solution.

[0018] According to some embodiments, the method for treating textile waste further includes:

[0019] (5) Decolorization and ion exchange steps, so that the filtered glucose solution is treated with decolorization and ion exchange (weak anion exchange resin and strong acid cation exchange resin) to decolorize the solution and remove enzymes and other soluble impurities.

[0020] According to some embodiments, the method for treating textile waste further includes:

[0021] (6) Concentration step: The glucose solution obtained in step (5) is concentrated to obtain glucose syrup with a glucose concentration of 10 g / L to 100 g / L.

[0022] According to another aspect, this disclosure provides a system for implementing the above-described method for treating textile waste, the system comprising:

[0023] (1) An ultrasonic generator for generating mechanical sound waves with a frequency ≥20kHz;

[0024] (2) A reactor for carrying out an enzymatic hydrolysis reaction, the reactor comprising a stirrer, preferably having paddle blades or turbine blades, more preferably large paddle blades.

[0025] According to some implementations, the system further includes:

[0026] (3) A first filtration device to remove PET from the reaction solution, yielding a cellulose-glucose mixture; and

[0027] (4) A second filtration device to separate the cellulose and glucose solution in the cellulose-glucose mixture and filter out the glucose solution;

[0028] According to some implementations, the system further includes:

[0029] (5) A decolorizing agent container to decolorize the filtered glucose solution; and / or

[0030] (6) Ion exchange column to remove enzymes and other impurities from glucose solution;

[0031] According to some implementations, the system further includes:

[0032] (7) Glucose solution storage and evaporation tank, used to collect and concentrate filtered glucose solution.

[0033] According to some embodiments, in the system, the second filtration device is, for example, a Nutsche filter and a scraper filter, with a pore size ranging from 1 to 200 micrometers, preferably from 50 to 100 micrometers.

[0034] According to some implementation methods, the pore size of the first filter (PET filter) must be larger than that of the second filter.

[0035] The system disclosed herein is a hardware system for separating cotton and PET, mainly comprising two reactors, with a maximum operating pressure of 10 bar, a maximum temperature of 180°C, and a reaction solution pH of approximately 2-6. Therefore, the system requires the operation of the textile waste treatment process disclosed herein within this environment. Ultrasonic equipment can be installed within the reactors. The system includes two filtration devices. The first filtration device removes PET, yielding a cellulose-glucose mixture. In the second filtration device, cellulose powder in the cellulose-glucose mixture is retained, while the glucose solution is filtered out. The filter can be, for example, a Nutsche filter or a scraper filter, or a centrifuge. The glucose solution is then transferred to a decolorization tank and an ion exchange column to decolorize the solution and remove enzymes. A weak anion exchange resin and a strong acid cation exchange resin are used to remove enzymes and impurities from the glucose solution, respectively.

[0036] The purified glucose solution was further concentrated to obtain glucose syrup in a glucose storage and evaporation tank.

[0037] The method for treating textile waste disclosed herein can also be applied to garment dyeing / washing containers.

[0038] According to certain embodiments of this disclosure, a system for recovering textile raw materials using enzymatic hydrolysis is provided, comprising (1) an ultrasonic generator for generating mechanical acoustic waves with a frequency ≥20 kHz; and (2) a reactor for biological treatment. The reactor includes a stirrer (with paddle or turbine blades) for mixing and agitating the textile waste material. A large number of microbubbles are formed in the solution within the reactor, and the collapse of these bubbles causes microjets to move at high speed toward the solid surface.

[0039] According to some embodiments, the system also includes a container for storing a decolorizing agent such as activated carbon, and the decolorizing agent such as activated carbon.

[0040] According to some embodiments, the system also includes an ion exchange column for storing ion exchange resin to remove enzymes from the glucose solution.

[0041] According to some embodiments, the system further includes a cellulose storage tank for collecting cellulose obtained after filtration by a second filtration device.

[0042] According to some embodiments, the system further includes a wash water storage tank and a wash water circulation pump for storing wash water and conveying wash water to a filtration device. According to a further aspect of this disclosure, the system also includes (1) a PET and cellulose conveying pump for conveying liquids of PET and cellulose materials; and (2) a PET and cellulose filtration device.

[0043] According to a further embodiment of this disclosure, the system further includes (1) a glucose solution buffer tank for temporary storage of glucose solution; (2) a glucose solution delivery pump for delivering glucose liquid; and (3) a glucose solution storage and evaporation tank for collecting and concentrating filtered glucose solution.

[0044] According to a further technical approach of this disclosure, the system further includes (1) a washing water delivery pump for delivering liquid containing cellulose particles; (2) a cellulose filtration device for retaining cellulose material; and (3) a cellulose storage tank for collecting the cellulose powder obtained after filtration.

[0045] According to a further aspect of this disclosure, the system also includes (1) a washing tank for collecting washing water and (2) a washing water circulation pump for conveying water from the washing water tank to a filtration device.

[0046] The textile waste disclosed herein includes, but is not limited to, fabrics, textiles and fibers.

[0047] According to some embodiments, the system further includes (1) a cold trap and a vacuum pump for condensing all vapors except permanent gases; (2) a CIP (clean in situ) system for recirculating the cleaning solution to rinse and wash the equipment or container with water or solution; (3) a heat source device, such as a heat transfer oil system, for providing heat transfer oil to heat the reactor and other containers when necessary; and (4) an upper inlet and a lower outlet for feeding and discharging materials.

[0048] The biological methods and systems disclosed herein have at least the following advantages: high recovery rate and high purity of raw materials, for example, PET has a purity and recovery rate of nearly 100%. Furthermore, they consume little energy and save energy. Attached Figure Description

[0049] Figure 1 The process flow of the method for treating textile waste disclosed herein is shown.

[0050] Figure 2 An example diagram of the system disclosed herein is shown.

[0051] Figure 2 In this reactor, which is a jacketed heating reactor, a stirring device with large impeller blades is installed.

[0052] Figure Labels

[0053] Reactors 11 and 21

[0054] 12, 22 Upper import

[0055] 13, 23 Lower Exits

[0056] 14, 24 heating valves

[0057] 15, 25 Inlet Valves

[0058] 16, 26 stirring blades

[0059] 17, 18, 27, 28 Ultrasonic generators

[0060] 32, 34 PET Filter Devices (First Filter Device)

[0061] 33 and 35 transfer pumps

[0062] 36. Cellulose filtration device (second filtration device)

[0063] 41 Water supply pipeline

[0064] 42 Heat source equipment

[0065] 43, 44 Ventilation ducts

[0066] 45 Thermal oil pump

[0067] 46 Heat Exchanger Invention Details

[0069] The accompanying drawings, wherein similar reference numerals refer to the same or functionally similar units or components, include drawings of certain embodiments to further illustrate and clarify various aspects, advantages, and features of the methods and systems for separating textile materials disclosed herein. It is understood that these drawings and figures depict only certain embodiments of the invention and are not intended to limit its scope. The bioseparation methods and systems disclosed herein will be described and explained in a specific and detailed manner using the accompanying drawings, wherein:

[0070] The system disclosed herein is hardware for separating cotton and PET, primarily comprising a reactor, which may be two reactors operating nearly simultaneously or in series. An ultrasonic device can be directly installed in the reactor for pretreatment or to assist in the separation of textile materials, wherein the treated fabrics may be clothing, textiles, and fibers. The pretreatment step is implemented by generating mechanosonic waves with a frequency ≥20 kHz using an ultrasonic generator. The ultrasonic waves generated by the ultrasonic generator consist of mechanosonic waves in the frequency range of 20 kHz to 500 MHz. These waves cause the formation of numerous microbubbles in the liquid medium. The collapse of these bubbles generates microjets that move at high speed toward the solid surface, creating localized hot spots with increased temperature, thereby promoting mass transfer and chemical reactions. Due to the formation of microjets, the ultrasonic waves erode the internal structure of the textile waste. The high energy intensity can break down particulate matter, thereby reducing particle size. In subsequent enzymatic hydrolysis, the textile material is more readily absorbed by enzymes, enabling cotton in blended textiles to be broken down into cellulose and glucose, while PET can be separated.

[0071] The reaction conditions in the reactor are no lower than 20°C and no higher than 70°C, preferably between 30-60°C. Enzymes used in the reaction include cellulase and glucosidase, with an enzyme content in the reaction solution ranging from 0.1-20%, preferably 1-10%. The pH range is 3-7, preferably 4-6, and a 0.001M-0.1M citrate-sodium citrate buffer solution is used to maintain the pH during the reaction. The reaction time ranges from 8 hours to 72 hours, preferably 12-24 hours. A paddle or turbine blade agitator, preferably a large paddle agitator, is installed on the bioreactor to ensure uniform reaction in the bioseparation process and prevent the formation of unreacted textile mixtures. The reactor uses a jacket to heat the reaction mixture using a heating medium and is equipped with the agitator, ultrasonic generator, circulation device, and filtration system listed in this invention. Furthermore, the bioreactor can also be used in garment dyeing / washing containers. After the bioprocess, two filtration devices can be performed. The first filtration device separates PET from the cellulose-glucose mixture. The cellulose powder and glucose solution are separated in a second filtration device (such as a Nutsche filter or a scraper filter). The pore size of the Nutsche filter and scraper filter ranges from 1 to 200 micrometers, preferably 50 to 100 micrometers, to separate the glucose solution from the cellulose. The glucose solution is then transferred to a decolorization tank and ion exchange column to decolorize the solution and remove enzymes. The purified glucose solution is further concentrated to obtain glucose syrup in a glucose storage and evaporation tank. After decolorization, the solution undergoes an ion exchange process to remove enzymes and other soluble impurities. Weak anion exchange resins and strong acidic cation exchange resins are used to remove enzymes and impurities from the glucose solution, respectively. The glucose solution treated by the decolorization tank and ion exchange column is then concentrated in a glucose storage and evaporation tank to produce a glucose syrup with a glucose concentration ranging from 10 g / L to 100 g / L.

[0072] In one specific embodiment of this disclosure, the system of this disclosure is as follows: Figure 2As shown, it includes a reactor 11 (21) equipped with ultrasonic generators 17, 18 (27, 28) and stirring blades 16 (26). Textile waste can enter the reactor through the upper inlet 12 (22), and deionized water can enter the reactor through the water supply line 41. After ultrasonic pretreatment, the enzyme hydrolysis reaction is carried out. Then, the enzyme hydrolysis reaction product enters the first filter device 32 (34) through the lower outlet 13 (23) to obtain solid PET. The filtrate is sent to the second filter device 36 through the transfer pump 33 (35) to separate the cellulose and glucose solution. Then, the filtered glucose solution is transferred to a decolorizing tank (not shown) and an ion exchange column (not shown) to decolorize the solution and remove the enzyme. The glucose solution is then introduced into a storage tank (not shown). If it is necessary to concentrate the glucose solution, it is introduced into an evaporator (not shown) to obtain glucose syrup.

[0073] Figure 2 The illustrated system includes two reactors and two corresponding post-processing units for the enzymatic hydrolysis products. In another embodiment, the system of this disclosure includes only one reactor and one corresponding post-processing unit for the enzymatic hydrolysis products. In other embodiments, the system of this disclosure may include two or more reactors and corresponding post-processing units for the enzymatic hydrolysis products. Detailed Implementation

[0074] The biological methods disclosed herein are illustrated below with reference to specific embodiments, but this application is not limited to the embodiments described.

[0075] Example 1

[0076] 20 kg of 55% cotton / 45% PET blended textile waste was mixed with 291 L of deionized water and pretreated with ultrasound at room temperature. The pretreatment was performed at 30% amplitude for 2 hours. After pretreatment, the 20 kg of 55% cotton / 45% PET blended textile waste was reacted in 300 L of a solution containing 3% Novozymes NS59104 enzyme and 0.01 M citrate-sodium citrate buffer for 24 hours at 50 ± 1 °C and pH 5. An average of 2.8% ± 0.2% of insoluble matter was retained in the PET fibers. This means that the obtained PET purity was 97.2%. The average molecular weight (Mw) of the collected cellulose powder after treatment was 264,596. The toughness of the treated PET fibers was 31.5 ± 0.28 cN / tex, and the initial toughness was 35.8 ± 0.24 cN / tex. The PET fibers are then spun into yarns with an average toughness ≥2g / den (17.7cN / tex) and an elongation ≥10%.

[0077] Example 2

[0078] 20 kg of 55% cotton / 45% PET blended textile waste was mixed with 291 L of deionized water and subjected to ultrasonic pretreatment at room temperature. Pretreatment was carried out at 60% amplitude for 4 hours. After pretreatment, the 20 kg of 55% cotton / 45% PET blended textile waste was reacted in 300 L of a solution containing 3% Novozymes NS29058 enzyme and 0.01 M citrate-sodium citrate buffer at 50 ± 1 °C and pH 5 for 48 hours. On average, 1.6% of insoluble matter remained in the PET fibers. This means that the obtained PET purity was 98.4%.

[0079] Example 3

[0080] 20 kg of 55% cotton / 45% PET blended yellow, blue, and green woven fabric waste was mixed with 291 L of deionized water and subjected to ultrasonic pretreatment at room temperature. Pretreatment was carried out at 30% amplitude for 2 hours. After pretreatment, the 20 kg of 55% cotton / 45% PET blended yellow, blue, and green woven fabric waste was reacted in 300 L of solution containing 3% Novozymes NS29058 enzyme and 0.01 M citrate-sodium citrate buffer for 24 hours at 50 ± 1 °C and pH 5. An average of 2.4% ± 0.2% of insoluble matter was retained in the PET fibers. This means that the purity of the obtained PET was 97.6%. The average molecular weight (Mw) of the collected cellulose powder after treatment was 292,684.

[0081] Example 4

[0082] 20 kg of 55% cotton / 45% PET blended knitted textile waste was mixed with 291 L of deionized water and subjected to ultrasonic pretreatment at room temperature. Pretreatment was carried out at 60% amplitude for 4 hours. After pretreatment, the 20 kg of 55% cotton / 45% PET blended knitted textile waste was reacted in 300 L of solution containing 3% Novozymes CCN03174 enzyme and 0.01 M citrate-sodium citrate buffer for 24 hours at 50 ± 1 °C and pH 5. An average of 2.9% ± 0.4% of insoluble matter remained in the PET fibers. This means that the obtained PET purity was 97.1%. The average molecular weight (Mw) of the collected cellulose powder after treatment was 289,836.

Claims

1. A method for treating waste fabrics made from blended PET and cotton, characterized in that, The method includes: (1) Ultrasonic pretreatment steps; and (2) Enzymatic hydrolysis step; The method separates the PET and cotton phases in textile waste.

2. The method according to claim 1, characterized in that, The enzymes used in the enzymatic hydrolysis step are selected from cellulase and / or glucosidase.

3. The method according to claim 1 or 2, characterized in that, The pH value of the reaction solution in the enzymatic hydrolysis step is 3 to 7.

4. The method according to any one of claims 1-3, characterized in that, In the enzymatic hydrolysis step, the reaction temperature is between 20°C and 70°C; the reaction time is between 8 hours and 72 hours; and / or the enzyme content in the reaction solution is 0.1-20 wt%.

5. The method according to any one of claims 1-4, characterized in that, In the enzymatic hydrolysis step, the added buffer is a citrate-sodium citrate buffer solution with a concentration range of 0.001M-0.1M.

6. The method according to any one of claims 1-5, characterized in that, The method further includes: (3) First filtration step to remove PET from the reaction solution to obtain a cellulose-glucose mixture.

7. The method according to any one of claims 1-6, characterized in that, The method further includes: (4) The second filtration step separates the cellulose and glucose solution in the cellulose-glucose mixture and filters out the glucose solution.

8. The method according to any one of claims 1-7, characterized in that, The method further includes: (5) Decolorization and ion exchange steps, so that the filtered glucose solution is decolorized and ion exchanged to remove enzymes and other soluble impurities.

9. The method according to any one of claims 1-8, characterized in that, The method further includes: (6) Concentration step: The glucose solution obtained in step (5) is concentrated to obtain glucose syrup with a glucose concentration of 10 g / L to 100 g / L.

10. A system for treating waste from blended PET and cotton fabrics, characterized in that, The system includes: An ultrasonic generator is used for ultrasonic treatment of waste materials made from blended PET and cotton fabrics; and An enzyme hydrolysis reactor is used to perform an enzymatic hydrolysis reaction on ultrasonically treated textile waste. The system separates PET and cotton from each other in blended textile waste.

11. The system according to claim 10, characterized in that, The enzyme hydrolysis reactor is equipped with a stirrer.

12. The system according to claim 10 or 11, characterized in that, The system also includes: A first filtration device is used to remove PET from the reaction solution, yielding a cellulose-glucose mixture; and A second filtration device is used to separate the cellulose and glucose solution and filter out the glucose solution.

13. The system according to claim 12, characterized in that, The system further includes: A decolorizing agent container for decolorizing the filtered glucose solution; and / or An ion exchange column is used to remove enzymes from the filtered glucose solution.

14. The system according to claim 12, characterized in that, The second filter in the system is a Nutsche filter, a scraper filter, or a centrifuge.

15. The system according to claim 13, characterized in that, The system further includes: A glucose solution storage and evaporation tank for collecting and concentrating glucose solutions after decolorization and / or ion exchange column treatment.

16. The system according to claim 12, characterized in that, The system also includes a cellulose storage tank for collecting the cellulose obtained after filtration by the second filtration device.

17. The system according to claim 12, characterized in that, The system also includes PET storage tanks for collecting the obtained PET.

18. The system according to claim 12, characterized in that, The system also includes a wash water storage tank and a wash water circulation pump for storing wash water and conveying wash water to the filtration device.

19. The system according to any one of claims 10-18, characterized in that, The second filter in the system has a pore size of 1 to 200 micrometers, preferably 50 to 100 micrometers.

20. The system according to any one of claims 10-19, characterized in that, The system includes a reactor 11, which is equipped with at least one ultrasonic generator 17 and a stirring blade 16. Textile waste can enter the reactor through the upper inlet 12, and water can enter the reactor through the water supply line 41. After ultrasonic pretreatment, the reactor undergoes an enzymatic hydrolysis reaction. The enzymatic hydrolysis product then enters the first filter device 32 through the lower outlet 13, thereby obtaining solid PET. The filtrate is sent to the second filter device 36 by the transfer pump 33 (35), thereby separating the cellulose and glucose solution.

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