Method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis

Abstract

The application discloses a method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis, and belongs to the technical field of textile waste treatment and resource recycling. The method utilizes the special physical and chemical properties of subcritical water and the synergistic effect of organic acid and Lewis acid catalyst, achieves efficient and accurate separation of polyester and cotton in the waste polyester-cotton blended fabric, separates polyester fibers, and decomposes cotton fibers into cellulose powder and glucose. The separated polyester fibers maintain good mechanical properties, the recovered cellulose powder has consistent structure performance with commercial microcrystalline cellulose, and then the acidolysis solution containing glucose is dehydrated and carbonized to prepare carbon microspheres. In the dehydration and carbonization process, the temperature of dehydration and carbonization is reduced due to the presence of organic acid in the acidolysis solution, and the growth of carbon microspheres is controlled, so that carbon microspheres with excellent morphology and structure are finally obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of textile waste treatment and resource recycling, and particularly relates to a method for separating waste polyester-cotton blended fabric through subcritical water catalytic acidolysis. BACKGROUND

[0002] As an important part of the global economic system, the textile industry not only meets people's clothing needs and promotes the development of the fashion industry, but also generates a large amount of waste textiles. Waste polyester-cotton blended fabric, as one of the main categories, faces many challenges in its treatment and recycling.

[0003] Traditionally, the treatment of waste polyester-cotton blended fabric is relatively extensive. Although some existing methods attempt to recycle waste polyester-cotton blended fabric, there are still obvious deficiencies. Physical separation methods, such as mechanical crushing and screening, are difficult to achieve precise separation of polyester and cotton, often resulting in low product purity and failing to meet the high-quality recycling requirements. While some chemical recycling methods can decompose or separate polyester and cotton to some extent, they require special equipment that is resistant to corrosion and high temperature, thereby increasing equipment investment costs. At the same time, key substances such as catalysts and solvents used in these methods are difficult to recycle and reuse, resulting in high overall recycling costs, poor economic benefits, and limiting their large-scale industrial application.

[0004] Therefore, how to effectively separate waste polyester-cotton blended fabric, achieve efficient recycling and recycling of resources, and reduce negative environmental impact has become a key problem to be solved in the current textile waste treatment field. SUMMARY

[0005] To solve the above technical problems, the application provides a method for separating waste polyester-cotton blended fabric through subcritical water catalytic acidolysis.

[0006] To achieve the above purpose, the application provides the following technical solutions:

[0007] The application provides a method for separating waste polyester-cotton blended fabric through subcritical water catalytic acidolysis, comprising the following steps:

[0008] (1) Pretreating the waste polyester-cotton blended fabric to obtain pretreated waste polyester-cotton fabric fragments;

[0009] (2) Placing the pretreated waste polyester-cotton fabric fragments obtained in step (1) and a composite catalyst aqueous solution into a reaction kettle, sealing the reaction kettle, and then performing subcritical water catalytic acidolysis, and after centrifugation and filtration, obtaining polyester fibers, cellulose powder, and a first sugar-containing acidolysis solution, respectively; the composite catalyst aqueous solution is a mixed aqueous solution of an organic acid and a Lewis acid catalyst;

[0010] (3) taking the first sugar-containing acidolysis solution obtained in step (2) as a catalyst for subcritical water catalytic acidolysis, repeating steps (1)-(2) to obtain a second sugar-containing acidolysis solution;

[0011] (4) subjecting the second sugar-containing acidolysis solution obtained in step (3) to dehydration carbonization to obtain carbon microspheres; the dehydration carbonization temperature is 150-180℃.

[0012] Technical principle: by utilizing the special physical and chemical properties of subcritical water and the synergistic effect of organic acid and Lewis acid catalyst, through the solubilization and diffusion promotion effect of subcritical water on the reactants under certain temperature and pressure, and the acid environment provided by the organic acid in the composite catalyst aqueous solution to promote the chemical bond rupture of cotton fibers and the principle of the Lewis acid catalyst to reduce the reaction activation energy, the efficient and accurate separation of polyester and cotton in the waste polyester-cotton blended fabric is achieved, the polyester fibers are separated, and the cotton fibers are decomposed into cellulose powder and glucose, the cellulose powder is recycled for reuse, and the glucose and the composite catalyst aqueous solution form a sugar-containing acidolysis solution, which can be reused for subcritical water catalytic acidolysis of waste polyester-cotton blended fabric; and the recycled sugar-containing acidolysis solution can be used to prepare carbon microspheres through dehydration carbonization, and in the dehydration carbonization process, the hydrogen ions are ionized from the organic acid in the solution, the hydroxyl groups of the glucose molecules are protonated, and the dehydration is accelerated; at the same time, the organic acid can act as a catalyst to form an intermediate complex with the reactants, change the reaction path, reduce the activation energy, promote the hydrolysis and polycondensation reaction, make the glucose convert into active intermediate products faster, and accelerate the formation of carbonaceous structure, thereby reducing the dehydration carbonization temperature. At the initial stage of carbonization, the organic acid combines with the dehydration product of glucose to control the uniform and orderly nucleation of carbon microspheres; in the growth process, by adjusting the growth rate, the carbon microspheres grow stably and moderately, the irregular morphology and uneven particle size are avoided, the structure is stabilized, agglomeration is prevented, surface defects are reduced, the viscosity and surface tension of the reaction system are adjusted, mass transfer is optimized, and finally the carbon microspheres with excellent morphology and structure are obtained.

[0013] The present application uses a mixed aqueous solution of organic acid and Lewis acid catalyst to catalyze the acidolysis of waste polyester-cotton blended fabric, the organic acid can make the chemical bonds such as glycosidic bonds of cotton fibers more easily broken in the environment of subcritical water, and the Lewis acid catalyst further reduces the energy barrier of the reaction, and the two synergistically improve the degradation rate and selectivity of cotton fibers, thereby efficiently separating cotton fibers from polyester fibers, and the separated polyester fibers maintain good mechanical properties and other qualities, and can be directly reused in the textile industry.

[0014] Preferably, in step (1), the pretreatment comprises the following steps: cutting the waste polyester-cotton blended fabric into pieces, and then sequentially immersing in a sodium carbonate solution and a hydrogen peroxide solution.

[0015] Preferably, the mass concentration of the sodium carbonate solution is 0.3-1.2%; the temperature for soaking with the sodium carbonate solution is 45-55℃, and the time is 25-50min.

[0016] Preferably, the mass concentration of the hydrogen peroxide solution is 1.5-2.5%; the temperature for soaking with the hydrogen peroxide solution is 55-65℃, and the time is 15-35min.

[0017] Preferably, in step (2), the mass concentration of the organic acid in the composite catalyst aqueous solution is 4-10%, and the mass concentration of the Lewis acid catalyst is 0.15-0.8%.

[0018] Preferably, in step (2), the solid-liquid ratio of the pretreated waste polyester-cotton fabric pieces and the composite catalyst aqueous solution is 1:(35-90).

[0019] Preferably, in step (2), the organic acid is selected from one or more of oxalic acid, acetic acid, tartaric acid and malic acid.

[0020] Preferably, in step (2), the Lewis acid catalyst is selected from one or more of copper sulfate, zinc sulfate and manganese acetate.

[0021] Preferably, in step (2), the subcritical water catalytic acidolysis adopts staged heating; the staged heating is specifically as follows: first, heating to 125-135℃ at a heating rate of 1.2-2.8℃ / min, and keeping the temperature for 8-18min; then, heating to 155-170℃ at a heating rate of 3.5-5.5℃ / min, and keeping the temperature for 0.5-2.0h.

[0022] Preferably, in step (3), the number of times of repeating steps (1)-(2) is 0-6.

[0023] Preferably, in step (4), the temperature for dehydration and carbonization is 150-160℃, and the time is 1.0-3.0h.

[0024] Compared with the prior art, the present application has the following advantages and technical effects:

[0025] The method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis provided by the application can efficiently separate cotton fibers from polyester fibers, and the polyester fibers obtained after separation can still maintain good mechanical properties and can be directly reused in the textile industry; the cellulose powder obtained after separation has basically the same structure and performance as commercial microcrystalline cellulose MCC and can be directly used in the paint, food and other industries; the sugar-containing acidolysis liquid is reused for subcritical water catalytic acidolysis of waste polyester-cotton blended fabric, and after the recycling is completed, carbon microspheres are prepared through dehydration and carbonization, the cotton fiber degradation products and the catalyst used in the acidolysis reaction process are fully utilized, efficient recycling and recycling of resources are realized, the production cost is greatly reduced, waste discharge is reduced, and the negative impact on the environment is reduced.

[0026] The method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis provided by the application has less damage to polyester fibers, can maximize the mechanical properties of the original polyester fibers, and the separated polyester fibers can be directly reused in the textile industry.

[0027] The method provided by the application can also reduce the temperature of dehydration and carbonization, reduce energy consumption, and obtain carbon microspheres with a higher specific surface area, which can be used in the field of water treatment. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0029] In order to make the above-mentioned purposes, characteristics and advantages of the application more obvious and easy to understand, the application will be further described in detail below in combination with specific embodiments.

[0030] The embodiments of the application provide a method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis, comprising the following steps:

[0031] (1) pretreating the waste polyester-cotton blended fabric to obtain pretreated waste polyester-cotton fabric fragments;

[0032] (2) placing the pretreated waste polyester-cotton fabric fragments obtained in step (1) and a composite catalyst aqueous solution into a reaction kettle, sealing the reaction kettle, and then performing subcritical water catalytic acidolysis, to obtain polyester fibers, cellulose powder and a first sugar-containing acidolysis liquid through centrifugation and filtration; the composite catalyst aqueous solution is a mixed aqueous solution of an organic acid and a Lewis acid catalyst;

[0033] (3) taking the first sugar-containing acidolysis solution obtained in step (2) as a catalyst for catalytic acidolysis of subcritical water, repeating steps (1)-(2) to obtain a second sugar-containing acidolysis solution;

[0034] (4) performing dehydration carbonization on the second sugar-containing acidolysis solution obtained in step (3) to obtain carbon microspheres; the dehydration carbonization temperature is 150-180 DEG C.

[0035] In a preferred embodiment, in step (1), the polyester-cotton blended fabric has a polyester-cotton blending ratio of (60:40)-(70:30).

[0036] In a preferred embodiment, in step (1), the pretreatment comprises the following steps: cutting the waste polyester-cotton blended fabric into pieces, and then sequentially immersing the pieces in a sodium carbonate solution and a hydrogen peroxide solution. The waste polyester-cotton blended fabric is immersed in the sodium carbonate solution and the hydrogen peroxide solution to remove grease, residual dyes and impurities on the surface of the fabric, thereby providing a good foundation for the subsequent subcritical water catalytic acidolysis reaction and improving the overall recycling effect.

[0037] In a preferred embodiment, the cutting is performed by cutting the waste polyester-cotton blended fabric into pieces with an edge length of 3-7 cm.

[0038] In a preferred embodiment, the sodium carbonate solution has a mass concentration of 0.3-1.2%, the immersion temperature is 45-55 DEG C, the immersion time is 25-50 min, and the solid-liquid ratio is 1:(5-20). The concentration, immersion temperature and immersion time of the sodium carbonate solution are controlled within the above ranges, which not only improves the surface quality of the fabric but also avoids damage to the polyester fibers.

[0039] In a preferred embodiment, after the immersion in the sodium carbonate solution, the fabric is rinsed with clean water for 4-6 times until the pH value of the rinsing water is close to neutral.

[0040] In a preferred embodiment, the hydrogen peroxide solution has a mass concentration of 1.5-2.5%, the immersion temperature is 55-65 DEG C, the immersion time is 15-35 min, and the solid-liquid ratio is 1:(4-30). The concentration, immersion temperature and immersion time of the hydrogen peroxide solution are controlled within the above ranges, which can effectively remove grease, impurities and residual dyes on the surface of the fabric, improve the surface quality of the fabric, and thus improve the overall recycling effect.

[0041] In a preferred embodiment, after the immersion in the hydrogen peroxide solution, the fabric is rinsed with clean water for 4-6 times.

[0042] In the preferred embodiment, in step (2), the mass concentration of the organic acid in the composite catalyst aqueous solution is 4-10%; the mass concentration of the Lewis acid catalyst is 0.15-0.8%. If the concentration of the organic acid is too low, it is difficult to create a sufficient acidic environment and provide sufficient active sites, resulting in poor separation of the waste polyester-cotton blended fabric, reduced recovery rate of polyester and cellulose powder, and decreased strength of polyester affected by impurities, and the performance of the carbon microspheres prepared therefrom is also poor due to the presence of too many impurities; if the concentration of the organic acid is too high, it can cause excessive reaction, damage the polyester and cotton fibers, reduce the recovery rate and strength of the polyester, and cause problems such as uneven particle size and increased surface defects of the carbon microspheres due to residual impurities during the preparation of the carbon microspheres; if the concentration of the Lewis acid catalyst is too low, the effect of the Lewis acid catalyst on the separation of the waste polyester-cotton blended fabric is not obvious, the separation efficiency is low, the separation time is long, and the separation degree is not ideal; if the concentration of the Lewis acid catalyst is too high, it can easily cause side reactions, damage the polyester fibers, reduce the separation efficiency, the recovery rate of the cellulose powder, and the recovery rate and strength of the polyester, and also interfere with the preparation process of the carbon microspheres, resulting in unstable performance of the carbon microspheres.

[0043] In the preferred embodiment, in step (2), the solid-liquid ratio of the pretreated waste polyester-cotton fabric fragments and the composite catalyst aqueous solution is 1:(35-90). If the solid-liquid ratio of the pretreated waste polyester-cotton fabric fragments and the composite catalyst aqueous solution is too small, the catalyst cannot fully contact the fabric to exert its effect, resulting in incomplete separation of the polyester and cotton, and cotton fibers remaining on the polyester, which affects subsequent processing; if the solid-liquid ratio is too large, the reaction system is excessively diluted, the effective concentration of the catalyst is reduced, the reaction rate is slowed down, the separation effect is poor, the time is prolonged, and it is difficult to achieve ideal separation degree.

[0044] In the preferred embodiment, in step (2), the organic acid is selected from one or more of oxalic acid, acetic acid, tartaric acid, and malic acid. The organic acid in the present application can make the chemical bonds such as glycosidic bonds of cotton fibers more easily broken in the subcritical water environment, and can synergistically act with the Lewis acid catalyst to significantly improve the degradation rate and selectivity of cotton fibers, thereby efficiently separating the cotton fibers from the polyester fibers; at the same time, the use of the organic acid also reduces the temperature of subsequent dehydration and carbonization, improves the particle size and particle size distribution, specific surface area, pore structure, and surface chemical stability of the carbon microspheres.

[0045] In the preferred embodiment, in step (2), the Lewis acid catalyst is selected from one or more of copper sulfate, zinc sulfate, and manganese acetate. The Lewis acid catalyst in the present application can reduce the energy barrier of the subcritical water catalytic acidolysis reaction, and can synergistically act with the organic acid to significantly improve the degradation rate and selectivity of cotton fibers, thereby efficiently separating the cotton fibers from the polyester fibers, and at the same time, the separated polyester fibers can maintain good mechanical properties and other qualities.

[0046] In the preferred embodiment, in step (2), the subcritical water catalytic acidolysis adopts staged heating; the staged heating is specifically: first, heating to 125-135℃ at a heating rate of 1.2-2.8℃ / min, and keeping the temperature for 8-18min, then heating to 155-170℃ at a heating rate of 3.5-5.5℃ / min, and keeping the temperature for 0.5-2.0h. The staged heating strategy adopted in the subcritical water catalytic acidolysis process of the present application not only guarantees the full reaction, but also avoids the damage of excessive reaction to the fibers.

[0047] In the preferred embodiment, in step (2), the pressure of the subcritical water catalytic acidolysis is 0.5-5MPa.

[0048] In the preferred embodiment, in step (2), the centrifugal speed is 5000-12000rpm, and the time is 20-30min.

[0049] In the preferred embodiment, in step (2), the mesh number of the screen used for filtering is 80-180.

[0050] In the preferred embodiment, in step (2), before filtering, the obtained solid product is subjected to multiple water washing, and then dried in an oven at 60-80℃ for 3-9h.

[0051] In the preferred embodiment, in step (3), the number of repeating steps (1)-(2) is 0-6, i.e. the recycling number of the sugar-containing acidolysis liquid is 0-6. By recycling the sugar-containing acidolysis liquid, the present application not only significantly improves the utilization efficiency of the acidolysis reaction liquid, effectively reduces the production cost, but also with the increase of the recycling number, the sugar content of the acidolysis liquid gradually increases, which promotes the increase of the carbon microsphere yield, and brings double gains of economic benefits and production benefits.

[0052] In a preferred embodiment, in step (4), the temperature of the dehydration carbonization is 150-180°C, further preferably 150-160°C; the time of the dehydration carbonization is 1.0-3.0h, further preferably 1.0-2.0h. During the dehydration carbonization, the sugars in the sugar-containing acid hydrolysate are dehydrated and polycondensed after being heated, and grow uniformly around the center under the action of the catalyst, isotropically forming a carbon skeleton. The organic acids in the dehydration carbonization process can stabilize and perfect the structure of the carbon microspheres, and the volatile substances are discharged, so that the carbon microspheres are densified, and the transformation from the sugar-containing acid hydrolysate to the carbon microspheres is completed. The organic acids in the acid hydrolysate and the dehydration carbonization product form a firm chemical chain, and the Lewis acid catalyst interacts with the sugar substances, its electron pair is combined with the sugar functional groups to change its coordination environment or generate new active species, so as to improve the graphitization degree of the carbon microspheres, increase the specific surface area, and improve the stability, so that the carbon microspheres are improved in terms of conductivity, mechanical properties, adsorption and catalytic activity, chemical and thermal stability, and the like.

[0053] Unless otherwise specified, the raw materials in the embodiments of the present application are obtained by commercial channels.

[0054] Example 1

[0055] A method for separating waste polyester-cotton blended fabric by subcritical water catalytic acid hydrolysis, the specific steps are as follows:

[0056] (1) Take 100 grams of waste polyester-cotton blended fabric with a blending ratio of 65:35, cut into fragments with a side length of 3 centimeters, and according to a solid-liquid ratio of 1:5, put into a sodium carbonate solution with a mass concentration of 0.3%, soak at 45°C for 50 minutes, then rinse with water for 6 times until the pH value of the rinsing water is close to neutral; then put the fabric fragments into a hydrogen peroxide solution with a mass concentration of 1.5% according to a solid-liquid ratio of 1:4, soak at 55°C for 35 minutes, and then rinse with water for 6 times to obtain pretreated waste polyester-cotton fabric fragments.

[0057] (2) Put the pretreated waste polyester-cotton fabric pieces obtained in step (1) into a high-pressure reaction kettle, and add a composite catalyst aqueous solution composed of acetic acid and copper sulfate, wherein the mass concentration of acetic acid is 4%, the mass concentration of copper sulfate is 0.15%, and the solid-liquid ratio of the pretreated waste polyester-cotton fabric pieces to the composite catalyst aqueous solution is set to 1:35; after sealing the reaction kettle, first increase the temperature to 125℃ at a heating rate of 1.2℃ / min, keep the temperature for 18min, and then increase the temperature to 155℃ at a heating rate of 3.5℃ / min, the reaction pressure is 0.5MPa, and the reaction time is 0.5h; after the reaction is completed, centrifuge the reaction liquid at a speed of 5000rpm for 30min to obtain solid precipitate and a first sugar-containing acid hydrolysate; the obtained solid precipitate is washed with water for several times, dried in an oven at 62℃ for 9h, and then sieved with an 80-mesh sieve to obtain reusable polyester fibers and cellulose powder raw materials, respectively.

[0058] (3) Take the first sugar-containing acid hydrolysate obtained in step (2) as the catalyst for subcritical water catalytic acid hydrolysis, repeat steps (1)-(2) once to obtain a second sugar-containing acid hydrolysate;

[0059] (4) Put the second sugar-containing acid hydrolysate obtained in step (3) into a reaction kettle, set the temperature of the reaction kettle to 150℃, and perform dehydration and carbonization, and after 1h, obtain carbon microspheres.

[0060] Example 2

[0061] A method for separating waste polyester-cotton blended fabric by subcritical water catalytic acid hydrolysis, the specific steps are as follows:

[0062] (1) Take 100 grams of waste polyester-cotton blended fabric with a blending ratio of 70:30, cut it into pieces with a side length of 5cm, and immerse it in a sodium carbonate solution with a mass concentration of 0.8% according to a solid-liquid ratio of 1:6 at 50℃ for 35min, and then wash it with clean water for 5 times until the pH value of the washing water approaches neutral; then immerse the fabric pieces in a hydrogen peroxide solution with a mass concentration of 2% according to a solid-liquid ratio of 1:5 at 60℃ for 25min, and then wash them with clean water for 5 times to obtain pretreated waste polyester-cotton fabric pieces.

[0063] (2) Put the pretreated waste polyester-cotton fabric fragments obtained in step (1) into a high-pressure reaction kettle, and add a composite catalyst aqueous solution composed of tartaric acid and zinc sulfate, wherein the mass concentration of tartaric acid is 7%, the mass concentration of zinc sulfate is 0.5%, and the solid-liquid ratio of the pretreated waste polyester-cotton fabric fragments to the composite catalyst aqueous solution is set to 1:60. After sealing the reaction kettle, first increase the temperature to 130°C at a rate of 2°C / min, and then increase the temperature to 160°C at a rate of 4.5°C / min. The reaction pressure is 0.8 MPa, and the reaction time is 2 h. After the reaction is completed, centrifuge the reaction liquid at a speed of 8000 rpm for 20 min to obtain solid precipitate and a first sugar-containing acid hydrolysate. The obtained solid precipitate is washed with water for multiple times, dried in a 70°C oven for 6 h, and then sieved with a 130-mesh sieve to obtain reusable polyester fibers and cellulose powder raw materials, respectively.

[0064] (3) Take the first sugar-containing acid hydrolysate obtained in step (2) as the catalyst for subcritical water catalytic acid hydrolysis, and repeat steps (1) and (2) twice to obtain a second sugar-containing acid hydrolysate.

[0065] (4) Add the second sugar-containing acid hydrolysate obtained in step (3) to the reaction kettle, set the temperature of the reaction kettle to 160°C, and perform dehydration and carbonization. After 1.5 h, carbon microspheres are obtained.

[0066] Example 3

[0067] A method for separating waste polyester-cotton blended fabric by subcritical water catalytic acid hydrolysis, the specific steps are as follows:

[0068] (1) Take 100 grams of waste polyester-cotton blended fabric with a blending ratio of 60:40, cut it into fragments with a side length of 7 centimeters, and immerse it in a sodium carbonate solution with a mass concentration of 1.2% at a solid-liquid ratio of 1:7 at 55°C for 25 min. Then wash it with clean water for 4 times until the pH value of the washing water approaches neutral. Next, immerse the fabric fragments in a hydrogen peroxide solution with a mass concentration of 2.5% at a solid-liquid ratio of 1:6 at 65°C for 15 min, and then wash it with clean water for 4 times to obtain pretreated waste polyester-cotton fabric fragments.

[0069] (2) Put the pretreated waste polyester-cotton fabric pieces obtained in step (1) into a high-pressure reaction kettle, and add a composite catalyst aqueous solution composed of oxalic acid and manganese acetate, wherein the mass concentration of oxalic acid is 10%, the mass concentration of manganese acetate is 0.8%, and the solid-liquid ratio of the pretreated waste polyester-cotton fabric pieces to the composite catalyst aqueous solution is set to 1:90; after sealing the reaction kettle, first increase the temperature to 135°C at a temperature increasing rate of 2.8°C / min, maintain for 8 min, and then increase the temperature to 170°C at a temperature increasing rate of 5.5°C / min, the reaction pressure is 1.2 MPa, and the reaction is carried out for 1.2 h; after the reaction is completed, centrifuge the reaction liquid at a speed of 6000 rpm for 25 min to obtain solid precipitate and a first sugar-containing acid hydrolysate; the obtained solid precipitate is washed with water for multiple times, dried in a 78°C oven for 3 h, and then sieved with a 180-mesh screen to obtain reusable polyester fibers and cellulose powder raw materials, respectively.

[0070] (3) Take the first sugar-containing acid hydrolysate obtained in step (2) as the catalyst for subcritical water catalytic acid hydrolysis, repeat steps (1)-(2) for 3 times to obtain a second sugar-containing acid hydrolysate;

[0071] (4) Put the second sugar-containing acid hydrolysate obtained in step (3) into a reaction kettle, set the temperature of the reaction kettle to 170°C, and carry out dehydration and carbonization, and after 2 h, obtain carbon microspheres.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that in step (2), only acetic acid is added, that is, the composite catalyst aqueous solution is replaced with an equal volume of acetic acid, and the mass concentration of acetic acid is 4%, and the others are the same as in Example 1.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that in step (2), only copper sulfate is added, that is, the composite catalyst aqueous solution is replaced with an equal volume of copper sulfate aqueous solution, and the mass concentration of copper sulfate is 0.15%, and the others are the same as in Example 1.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that in step (2), after sealing the reaction kettle, the temperature is increased to 155°C at a temperature increasing rate of 3.5°C / min, the reaction pressure is 0.5 MPa, and the reaction is carried out for 0.5 h, and the others are the same as in Example 1.

[0078] Comparative Example 4

[0079] (1) Take 100 grams of waste polyester-cotton blended fabric with a blending ratio of 65:35, cut into pieces with a side length of 3 cm, and place the fabric pieces in a 0.3% mass concentration sodium carbonate solution at a solid-liquid ratio of 1:5, soak at 45°C for 50 min, then rinse with clean water for 6 times until the pH value of the rinsing water approaches neutral, to obtain pretreated waste polyester-cotton fabric pieces;

[0080] Steps (2)-(3) are the same as in Example 1.

[0081] Comparative Example 5

[0082] (1) Take 100 grams of waste polyester-cotton blended fabric with a blending ratio of 65:35, cut into pieces with a side length of 3 cm, and place the fabric pieces in a 1.5% mass concentration hydrogen peroxide solution at a solid-liquid ratio of 1:4, soak at 55°C for 35 min, then rinse with clean water for 6 times, to obtain pretreated waste polyester-cotton fabric pieces;

[0083] Steps (2)-(3) are the same as in Example 1.

[0084] Comparative Example 6

[0085] (1) Take 100 grams of waste polyester-cotton blended fabric with a blending ratio of 65:35, cut into pieces with a side length of 3 cm, and rinse with clean water for 6 times, to obtain pretreated waste polyester-cotton fabric pieces;

[0086] Steps (2)-(3) are the same as in Example 1.

[0087] The breaking strength of the recyclable polyester fibers obtained in steps (2) of Examples 1-3 and Comparative Examples 1-6 was tested by single fiber tensile method, and the specific surface area of the carbon microspheres obtained in Examples 1-3 and Comparative Examples 1-6 was tested by mercury intrusion method, and the results are shown in Table 1.

[0088] Table 1: Polyester fiber recovery rate and product performance of Examples 1-3 and Comparative Examples 1-6

[0089]

[0090] As can be seen from Table 1, the recovery rate of the polyester fibers in Examples 1-3 of the present application is above 92%, the recovery rate of the cellulose powder is above 88%, the breaking strength of the recovered polyester fibers is above 3.0 N / tex, and the specific surface area of the obtained carbon microspheres is above 150 cm 2 / g. Compared with Example 1, Comparative Example 1 only uses acetic acid, the recovery rate of the polyester fibers decreases by 23%, the recovery rate of the cellulose powder decreases by 20%, the breaking strength of the recovered polyester fibers decreases by 1.0 N / tex, and the specific surface area of the obtained carbon microspheres decreases by 81 cm 2 / g; the comparative example 2 only used copper sulfate, the recovery rate of polyester fiber decreased by 25%, the recovery rate of cellulose powder decreased by 26%, the breaking strength of the recovered polyester fiber decreased by 1.2N / tex, and the specific surface area of the obtained carbon microspheres decreased by 94cm 2 / g; the comparative example 3 changed the temperature rising strategy in the subcritical water catalytic acidolysis process, the recovery rate of polyester fiber decreased by 18%, the recovery rate of cellulose powder decreased by 13%, the breaking strength of the recovered polyester fiber decreased by 0.9N / tex, and the specific surface area of the obtained carbon microspheres decreased by 8cm 2 / g; the comparative example 4~6 changed the pretreatment method of the waste polyester-cotton blended fabric, the recovery rate of polyester fiber decreased by 13%, 17%, 28% respectively, the recovery rate of cellulose powder decreased by 8%, 20%, 23% respectively, the breaking strength of the recovered polyester fiber decreased by 0.6N / tex, 0.8N / tex, 1.1N / tex respectively, and the specific surface area of the obtained carbon microspheres decreased by 19cm 2 / g, 21cm 2 / g, 65cm 2 / g.

[0091] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any change or replacement easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis, characterized in that, The method comprises the following steps: (1) pretreating the waste polyester-cotton blended fabric to obtain pretreated waste polyester-cotton blended fabric pieces; The pretreatment comprises the following steps: cutting the waste polyester-cotton blended fabric into pieces, and then sequentially immersing the pieces in a sodium carbonate solution and a hydrogen peroxide solution; The sodium carbonate solution has a mass concentration of 0.3-1.2%, and the immersion in the sodium carbonate solution is performed at a temperature of 45-55°C for 25-50 min; the hydrogen peroxide solution has a mass concentration of 1.5-2.5%, and the immersion in the hydrogen peroxide solution is performed at a temperature of 55-65°C for 15-35 min; (2) placing the pretreated waste polyester-cotton blended fabric pieces obtained in step (1) and a composite catalyst aqueous solution in a reaction kettle, sealing the reaction kettle, and then performing subcritical water catalytic acidolysis, and obtaining polyester fibers, cellulose powder and a first sugar-containing acidolysis liquid by centrifugation and filtration, respectively; the composite catalyst aqueous solution is a mixed aqueous solution of an organic acid and a Lewis acid catalyst; the mass concentration of the organic acid in the composite catalyst aqueous solution is 4-10%, and the mass concentration of the Lewis acid catalyst is 0.15-0.8%; the subcritical water catalytic acidolysis is performed by staged heating; the staged heating is specifically as follows: first, heating to 125-135°C at a heating rate of 1.2-2.8°C / min, and then maintaining the temperature for 8-18 min, and then heating to 155-170°C at a heating rate of 3.5-5.5°C / min, and then maintaining the temperature for 0.5-2.0 h; (3) using the first sugar-containing acidolysis liquid obtained in step (2) as a catalyst for subcritical water catalytic acidolysis, repeating steps (1) and (2) to obtain a second sugar-containing acidolysis liquid; (4) performing dehydration carbonization on the second sugar-containing acidolysis liquid obtained in step (3) to obtain carbon microspheres; the dehydration carbonization is performed at a temperature of 150-180°C.

2. The method according to claim 1, wherein the subcritical water catalytic acidolysis separation of waste polyester-cotton blended fabric is characterized in that, In step (2), the solid-liquid ratio of the pretreated waste polyester-cotton blended fabric pieces to the composite catalyst aqueous solution is 1:(35-90).

3. The method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis according to claim 1, characterized in that, In step (2), the organic acid is selected from one or more of oxalic acid, acetic acid, tartaric acid and malic acid.

4. The method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis according to claim 1, characterized in that, In step (2), the Lewis acid catalyst is selected from one or two of copper sulfate, zinc sulfate and manganese acetate.

5. The method for separating waste polyester-cotton blended fabric by subcritical water catalytic acidolysis according to claim 1, characterized in that, In step (3), the dehydration carbonization is performed at a temperature of 150-160°C for 1.0-3.0 h.

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