Method for purifying waste polyester textile regeneration DMT

Abstract

The application discloses a new route for purifying regenerated DMT, and the application is characterized in that layered double hydroxide and porous dopamine are used as adsorbents, tannic acid is used as a binder, and the adsorbents are loaded on a cellulose membrane to prepare a filter membrane with a dye adsorption function; meanwhile, an industrial filter membrane is combined to form a multi-layer series filter system, and regenerated DMT is subjected to primary purification; then, the melt crystallization and rectification coupling technology is adopted to perform secondary purification on the regenerated DMT, so that high-purity and high-quality regenerated DMT is formed, the application field of the regenerated DMT is expanded, and a foundation is laid for high-value utilization of downstream regenerated DMT. The application effectively solves the technical problem of the difficulty in purifying the regenerated DMT, and will strongly promote the application and development of the regenerated DMT.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of regenerating DMT, and particularly relates to a purification method of regenerating DMT from the product of glycol alcoholysis-methanol transesterification of waste polyester textiles. TECHNICAL BACKGROUND

[0002] In recent years, with the increase of polyester fiber production and the continuous expansion of application fields, the stockpiling amount of waste polyester textiles in China has been growing continuously, but the comprehensive recycling rate is less than 15%, and a large amount of waste textiles are still treated in the traditional landfill and incineration way, which not only causes great resource waste, but also brings great burden to the environment. At present, waste textiles are mainly recovered by physical and chemical methods. Compared with physical recovery, chemical recovery can realize high-value closed-loop recycling of waste textiles, and the glycol alcoholysis-methanol transesterification method has great application prospect in the field of recycling and utilization of waste polyester textiles due to its mild reaction conditions, low equipment requirements and convenient monomer recovery. However, there are impurities such as BHET, DMT isomers, dyes, and oil agents in the process of preparing regenerated DMT by glycol alcoholysis-methanol transesterification, which causes low purity of regenerated DMT and seriously hinders the development and high-value utilization of downstream regenerated products. Therefore, it is urgent to develop an efficient purification method for regenerated DMT.

[0003] Layered double hydroxides (LDH), commonly known as hydrotalcite, refers to a special class of layered materials. This layered material is composed of several layers of positively charged layers and interlayer balancing charges of anions. The interlayer anions and the interlayer interaction are weak, and anion exchange can be carried out. Due to the special layered structure, large specific surface area and flexibility of LDH, it has attracted widespread attention in the field of dye adsorption. Secondly, the surface of LDH has hydroxyl groups and positive charges, which can combine with other polymer molecules to form LDH-based nanocomposites, enhancing the dye adsorption capacity. Porous polydopamine (PDA) is a porous material with rich functional groups. Due to its special porous structure and rich functional groups, it can interact with metal ions, synthetic dyes and other pollutants through electrostatic and hydrogen bonding interactions to become effective active binding sites. Therefore, the combination of LDH and porous polydopamine has good effect on dye adsorption.

[0004] Melt crystallization is a new type of chemical separation method, which can separate impurities lower than the melting point of the product, and has the following advantages compared with conventional chemical separation methods: it can effectively separate high-purity products; it is generally operated at normal pressure and low temperature, and is simple and safe to operate, and has no high requirements for equipment; it is environmentally friendly, and compared with recrystallization, it does not require other solvents, and reduces production cost. However, due to the complex source of waste textiles, the impurity composition of regenerated DMT is relatively high, and single melt crystallization cannot obtain high-purity DMT, therefore, the present application designs a melt crystallization and rectification coupling technology for preparing DMT from waste textiles, compared with the known route for preparing high-purity DMT from waste textiles, the number of rectification is reduced, the production energy consumption and cost are reduced, and high-purity DMT can be prepared, which promotes the development of high-value downstream DMT products.

[0005] Therefore, in view of the complex composition and difficult separation of impurities in the regenerated DMT product of ethylene glycol alcoholysis-ester exchange, a multi-layer series filtration technology, melt crystallization and rectification coupling technology are used to realize efficient purification of regenerated DMT, which has important value for the development of high-quality regenerated polyester downstream. SUMMARY

[0006] The present application provides a high-efficiency DMT purification route for the problems of more impurities, complex composition and difficult DMT purification in the ethylene glycol-methanol ester exchange process of waste textiles. Figure One For the dye molecules in DMT, the layered double hydroxide, dopamine and cellulose are innovatively combined to prepare a cellulose membrane with dye adsorption function; based on the modified fiber membrane and the general filter screen, a multi-layer series filtration technology is used to preliminarily purify the DMT solution; a melt crystallization and rectification coupling purification technology is used to further purify the DMT, and a high-purity DMT product is obtained.

[0007] A purification method of regenerated DMT from waste polyester textiles, characterized in that it comprises the following steps:

[0008] (1) Preparation of dye adsorbent

[0009] A mixed solution containing soluble divalent metal salt and trivalent metal salt and an alkaline solution are prepared respectively, then the alkaline solution is added to the mixed solution, and the mixed solution is subjected to hydrothermal treatment and vacuum drying to obtain layered double hydroxide sheet.

[0010] (2) Preparation of modified fiber membrane

[0011] The layered double hydroxide, porous dopamine and tannic acid are added into a buffer solution to obtain a suspension, then a cellulose solution and a coagulant are added, and the mixture is stirred to obtain a modified cellulose casting solution, the casting solution is poured into a mold to form a film, and the film is removed, vacuum cooled and dried to obtain a cellulose modified film with dye adsorption function.

[0012] (3) Multi-layer series filtration technology

[0013] The industrial filtration membrane and the modified fiber membrane are sequentially assembled from top to bottom in a filtration device, and methanol solution is used as the mobile phase to form a multi-layer series filtration from top to bottom, and the dye molecules in the DMT solution are preliminarily filtered.

[0014] (4) Melting crystallization and rectification coupling technology

[0015] The filtered DMT solution is sent into a melting crystallizer, and the crystallization process includes crystallization, sweating and melting, then the DMT melt is sent into a rectification tower, and after rectification, the DMT is cooled, crystallized and dried to obtain high-purity DMT.

[0016] Preferably, the cation in the solution containing soluble divalent and trivalent metal salt in step (1) is one or two of Cu 2+ , Zn 2+ , Ni 2+ , Mg 2+ , Fe 2+ , Al 3+ ; the anion of the soluble divalent metal salt and the soluble trivalent metal salt is one or two of Cl - , NO 3- , SO4 2- , CO3 2- ; the alkaline solution is urea, ammonia or sodium hydroxide.

[0017] The total concentration of the soluble divalent metal salt and the soluble trivalent metal salt in step (1) is 0.05-0.5 mol / L, and the molar mass ratio of the total amount of the soluble divalent metal salt and the soluble trivalent metal salt to the alkaline substance is 1:1-10.

[0018] The temperature of the hydrothermal reaction in step (1) is 95-110℃, and the time is 6-24h.

[0019] The mass ratio of LDH, dopamine, tannic acid, cellulose and coagulant in step (2) is 1:1-3:1-3:5:0.5, the buffer is one of Tris buffer, phosphate buffer, borate buffer and bicarbonate buffer; the coagulant is one of calcium chloride aqueous solution, hydrochloric acid aqueous solution or acetic acid aqueous solution, the rotation speed is 200 r / min, the stirring time is 10-20 h, the vacuum cooling temperature is-50℃, and the cooling time is 20 h.

[0020] The filtering temperature in step (3) is 25-30℃.

[0021] The crystallization temperature in step (4) is 126-135℃, the crystallization time is 1.5-2 h, the sweating temperature is 136-140℃, the sweating time is 2-4 h, the melting temperature is 141-145℃, and the time is 1-2 h.

[0022] The rectification temperature in step (4) is 280-300℃, and the rectification time is 2-5 h.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1. The present application realizes the adsorption of dyes by utilizing the layered structure of LDH and the porous structure of polydopamine, and realizes the stable loading of LDH and polydopamine by utilizing the good interfacial bonding performance between LDH, polydopamine and cellulose membrane.

[0025] 2. The multi-layer series filtering technology is adopted to effectively filter the insoluble substances in the regenerated DMT solution and simultaneously effectively adsorb the dye molecules in the regenerated DMT, so as to realize the preliminary filtration of the regenerated DMT.

[0026] 3. Compared with the traditional purification method of regenerated DMT, the present application adopts the coupling technology of melting crystallization and rectification, reduces the production cost and energy consumption, optimizes the process conditions, and realizes the efficient purification of regenerated DMT. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The regenerated DMT purification process flowchart of the present application;

[0028] Figure 2 The gas chromatogram of the regenerated DMT of Example 9;

[0029] Figure 3 The infrared analysis spectrum diagram of the regenerated DMT of Example 9;

[0030] 1. Alcoholysis-ester exchange product storage tank; 2. Multi-layer filter; 3. Melting crystallizer; 4. Collection tank; 5. Heat exchanger; 6. Rectification tower; 7. Condenser; 8. Reflux tank; 9. Pump; Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1:

[0033] (1) Based on 100 parts by mass of a divalent metal salt, CuSO4 (100 parts by mass), Al2(SO4)3 (30 parts by mass), MgSO4 (70 parts by mass), and urea (70 parts by mass) were added to 5000 parts by mass of distilled water. The hydrothermal reaction was carried out at 100°C for 10 h. After the reaction was completed, the product was filtered and washed with a large amount of distilled water. Finally, the product was dried under vacuum for 12 h to obtain a layered bimetallic hydroxide.

[0034] (2) Based on 100 parts by weight of LDH, add polydopamine (100 parts by weight), tannic acid (100 parts by weight), phosphate (30 parts by weight), cellulose (500 parts by weight), and coagulant (50 parts by weight) to 1000 parts by weight of distilled water and stir thoroughly for 12 hours. After molding, demold and vacuum cool and dry for 20 hours at a temperature of -50°C to prepare a modified cellulose membrane.

[0035] (3) Assemble one layer of ordinary filter membrane and one layer of modified fiber membrane. The filtration temperature is 25℃. DMT is initially purified and regenerated.

[0036] (4) Melting and crystallization: the crystallization temperature is 126℃, the crystallization time is 1.5h, the sweating temperature is 136℃, the sweating time is 2h, the melting temperature is 141℃, the melting time is 1h, and then the distillation is carried out at a temperature of 280℃ for 2h. High-purity regenerated DMT is collected at the top of the column.

[0037] Example 2:

[0038] (1) Based on 100 parts by mass of a divalent metal salt, CuSO4 (150 parts by mass), MgSO4 (70 parts by mass), and urea (70 parts by mass) were added to 5000 parts by mass of distilled water. The hydrothermal reaction was carried out at 110°C for 10 h. After the reaction was completed, the product was filtered and washed with a large amount of distilled water. Finally, the product was dried under vacuum for 12 h to obtain a layered bimetallic hydroxide.

[0039] (2) Based on 100 parts by weight of LDH, add polydopamine (120 parts by weight), tannic acid (120 parts by weight), phosphate (60 parts by weight), cellulose (500 parts by weight), and coagulant (50 parts by weight) to 1000 parts by weight of distilled water and stir thoroughly for 12 hours. After molding, demold and vacuum cool and dry for 20 hours at a temperature of -50°C to prepare a modified cellulose membrane.

[0040] (3) 1 layer of general filter membrane and 2 layers of modified fiber membrane were assembled, and the filtration temperature was 25℃, and the regenerated DMT was preliminarily purified.

[0041] (4) The melt crystallization temperature was 129℃, the crystallization time was 1.5h, the sweating temperature was 136℃, the sweating time was 2h, the melting temperature was 141℃, the melting time was 2h, and then the rectification purification was carried out, the rectification temperature was 285℃, the time was 3h, and high-purity regenerated DMT was collected at the top of the tower.

[0042] Example 3:

[0043] (1) Based on 100 parts by mass of divalent metal salt, ZnCl2 (100 parts by mass), FeCl3 (30 parts by mass), ammonia (500 parts by mass) were added in 5000 parts by mass of distilled water. Hydrothermal reaction was carried out at 110℃ for 6h, and the product was obtained after filtration, and washed with a large amount of distilled water, and finally obtained by vacuum drying for 12h to obtain layered double hydroxide.

[0044] (2) Based on 100 parts by mass of LDH, polydopamine (150 parts by mass), tannic acid (150 parts by mass), borate (20 parts by mass), cellulose (500 parts by mass), coagulant (50 parts by mass) were added in 1000 parts by mass of distilled water, and stirred for 14h, then poured into a mold, demolded, vacuum cooled and dried for 20h, and the cooling temperature was-50℃, to prepare a modified cellulose membrane.

[0045] (3) 1 layer of general filter membrane and 3 layers of modified fiber membrane were assembled, and the filtration temperature was 25℃, and the regenerated DMT was preliminarily purified.

[0046] (4) The melt crystallization temperature was 131℃, the crystallization time was 2h, the sweating temperature was 137℃, the sweating time was 2.5h, the melting temperature was 142℃, the melting time was 1h, and then the rectification purification was carried out, the rectification temperature was 290℃, the time was 3h, and high-purity regenerated DMT was collected at the top of the tower.

[0047] Example 4:

[0048] (1) Based on 100 parts by mass of divalent metal salt, Mg(NO3)2 (200 parts by mass), Fe(NO3)3 (80 parts by mass), ammonia (500 parts by mass) were added in 5000 parts by mass of distilled water. Hydrothermal reaction was carried out at 110℃ for 6h, and the product was obtained after filtration, and washed with a large amount of distilled water, and finally obtained by vacuum drying for 12h to obtain layered double hydroxide.

[0049] (2) Based on 100 parts by mass of LDH, 180 parts by mass of polydopamine, 180 parts by mass of tannic acid, 20 parts by mass of bicarbonate, 500 parts by mass of cellulose, and 50 parts by mass of coagulant were added to 1000 parts by mass of distilled water, and stirred for 15 hours. The mixture was poured into a mold, demolded, vacuum-cooled and dried for 20 hours at a cooling temperature of -50°C to obtain a modified cellulose membrane.

[0050] (3) One layer of a general filter membrane and four layers of a modified fiber membrane were assembled, and the filtration temperature was 25°C to preliminarily purify the regenerated DMT.

[0051] (4) The melting crystallization temperature was 133°C, the crystallization time was 2 hours, the sweating temperature was 137°C, the sweating time was 2.5 hours, the melting temperature was 142°C, the melting time was 2 hours, and then the rectification purification was performed at a rectification temperature of 292°C for 4 hours, and high-purity regenerated DMT was collected at the top of the tower.

[0052] Example 5:

[0053] (1) Based on 100 parts by mass of divalent metal salt, 50 parts by mass of CuSO4, 30 parts by mass of Fe2(SO4)3, and 70 parts by mass of urea were added to 5000 parts by mass of distilled water, and a hydrothermal reaction was performed at 100°C for 18 hours. After the reaction, the product was filtered and washed with a large amount of distilled water, and then vacuum-dried for 12 hours to obtain a layered double hydroxide.

[0054] (2) Based on 100 parts by mass of LDH, 200 parts by mass of polydopamine, 200 parts by mass of tannic acid, 100 parts by mass of tris-hydroxymethyl aminomethane, 500 parts by mass of cellulose, and 50 parts by mass of coagulant were added to 1000 parts by mass of distilled water, and stirred for 16 hours. The mixture was poured into a mold, demolded, vacuum-cooled and dried for 20 hours at a cooling temperature of -50°C to obtain a modified cellulose membrane.

[0055] (3) One layer of a general filter membrane and five layers of a modified fiber membrane were assembled, and the filtration temperature was 25°C to preliminarily purify the regenerated DMT.

[0056] (4) The melting crystallization temperature was 134°C, the crystallization time was 2.5 hours, the sweating temperature was 138°C, the sweating time was 2.5 hours, the melting temperature was 143°C, the melting time was 1 hour, and then the rectification purification was performed at a rectification temperature of 294°C for 2 hours, and high-purity regenerated DMT was collected at the top of the tower.

[0057] Example 6:

[0058] (1) 100 parts by mass of divalent metal salt as a basis, 5000 parts by mass of distilled water, NiSO4(40 parts by mass), Cr2(SO4)3(10 parts by mass), sodium hydroxide (180 parts by mass) were added. Hydrothermal reaction was carried out at 95°C for 18h, and the product was obtained after filtration, and washed with a large amount of distilled water, and finally dried by vacuum drying for 12h to obtain layered double hydroxide.

[0059] (2) 100 parts by mass of LDH as a basis, 1000 parts by mass of distilled water, polydopamine (220 parts by mass), tannic acid (220 parts by mass), tris (100 parts by mass), cellulose (500 parts by mass), coagulant (50 parts by mass) were added, and stirred for 20h, then poured into a mold, demolded, vacuum cooled and dried for 20h, and the cooling temperature was -50°C. Modified cellulose membrane was prepared.

[0060] (3) Assemble 2 layers of general filter membrane and 2 layers of modified fiber membrane, and filter at 25°C to preliminarily purify the regenerated DMT.

[0061] (4) The melting crystallization temperature is 134°C, the crystallization time is 3h, the sweating temperature is 138°C, the sweating time is 3h, the melting temperature is 143°C, and the melting time is 2h, and then the rectification purification is carried out, the rectification temperature is 295°C, and the time is 3h. High-purity regenerated DMT is collected at the top of the tower.

[0062] Example 7:

[0063] (1) 100 parts by mass of divalent metal salt as a basis, 5000 parts by mass of distilled water, MgSO4(50 parts by mass), Al2(SO4)3(25 parts by mass), sodium hydroxide (180 parts by mass) were added. Hydrothermal reaction was carried out at 100°C for 18h, and the product was obtained after filtration, and washed with a large amount of distilled water, and finally dried by vacuum drying for 12h to obtain layered double hydroxide.

[0064] (2) 100 parts by mass of LDH as a basis, 1000 parts by mass of distilled water, polydopamine (250 parts by mass), tannic acid (250 parts by mass), tris (100 parts by mass), cellulose (500 parts by mass), coagulant (50 parts by mass) were added, and stirred for 20h, then poured into a mold, demolded, vacuum cooled and dried for 20h, and the cooling temperature was -50°C. Modified cellulose membrane was prepared.

[0065] (3) Assemble 2 layers of general filter membrane and 3 layers of modified fiber membrane, and filter at 25°C to preliminarily purify the regenerated DMT.

[0066] (4) The melt crystallization temperature is 135℃, the crystallization time is 1.5h, the sweating temperature is 139℃, the sweating time is 2h, the melting temperature is 144℃, the melting time is 1h, and then the rectification purification is carried out, the rectification temperature is 295℃, the time is 5h, and the high-purity regenerated DMT is collected at the top of the tower.

[0067] Example 8:

[0068] (1) Based on 100 parts by mass of the divalent metal salt, ZnSO4 (25 parts by mass), MgSO4 (70 parts by mass), Fe2(SO4)3 (40 parts by mass), and sodium hydroxide (180 parts by mass) were added to 5000 parts by mass of distilled water. The hydrothermal reaction was carried out at 100℃ for 18h, and after the reaction was completed, the product was filtered and washed with a large amount of distilled water, and finally layered double hydroxide was obtained by vacuum drying for 12h.

[0069] (2) Based on 100 parts by mass of the LDH, polydopamine (280 parts by mass), tannic acid (280 parts by mass), tris-hydroxymethyl aminomethane (100 parts by mass), cellulose (500 parts by mass), and coagulant (50 parts by mass) were added to 1000 parts by mass of distilled water, and stirred for 20h. After pouring into a mold and demolding, vacuum cooling and drying were carried out for 20h at a cooling temperature of -50℃, and a modified cellulose membrane was prepared.

[0070] (3) Two layers of general filter membranes and four layers of modified fiber membranes were assembled, and the filtration temperature was 25℃ to preliminarily purify the regenerated DMT.

[0071] (4) The melt crystallization temperature is 135℃, the crystallization time is 2h, the sweating temperature is 139℃, the sweating time is 4h, the melting temperature is 144℃, the melting time is 2h, and then the rectification purification is carried out, the rectification temperature is 297℃, the time is 4h, and the high-purity regenerated DMT is collected at the top of the tower.

[0072] Example 9:

[0073] (1) Based on 100 parts by mass of the divalent metal salt, FeSO4 (110 parts by mass), Fe2(SO4)3 (40 parts by mass), and sodium hydroxide (180 parts by mass) were added to 5000 parts by mass of distilled water. The hydrothermal reaction was carried out at 100℃ for 18h, and after the reaction was completed, the product was filtered and washed with a large amount of distilled water, and finally layered double hydroxide was obtained by vacuum drying for 12h.

[0074] (2) Based on 100 parts by mass of LDH, 300 parts by mass of polydopamine, 300 parts by mass of tannic acid, 100 parts by mass of tris (hydroxymethyl) aminomethane, 500 parts by mass of cellulose, and 50 parts by mass of coagulant were added to 1000 parts by mass of distilled water, and stirred for 20 h. The mixture was poured into a mold, demolded, and vacuum cooled and dried for 20 h at a cooling temperature of -50°C to obtain a modified cellulose membrane.

[0075] (3) Two layers of general filter membranes and five layers of modified fiber membranes were assembled, and the filtration temperature was 25°C. The DMT was preliminarily purified.

[0076] (4) The melting crystallization temperature was 135°C, the crystallization time was 3 h, the sweating temperature was 140°C, the sweating time was 4 h, the melting temperature was 145°C, the melting time was 2 h, and then the rectification purification was performed at a rectification temperature of 300°C for 5 h. The high-purity regenerated DMT was collected at the top of the tower.

[0077] Comparative Example 1: The method of Example 1 was followed, except that the multi-layer series filtration method was not used.

[0078] Comparative Example 2: The method of Example 1 was followed, except that the melting crystallization and rectification coupling technology was not used.

[0079] Comprehensive Description:

[0080] (1) Decolorization rate

[0081] The DMT solution after filtration was dissolved, diluted, and filtered, and then detected by a UV-Vis spectrophotometer to calculate the concentration of the dye molecules.

[0082] (2) DMT purity

[0083] The content of dimethyl terephthalate was determined by an internal standard curve method, dipropyl phthalate was selected as the internal standard substance, chloroform was used as the solvent, the peak area was quantified, and the purity of DMT was calculated.

[0084] As can be seen from Table 1, the performance evaluation of Examples 1-9 shows that the adsorption performance of the dye is significantly enhanced with the increase of the loading amount of LDH and dopamine and the stirring treatment time. The performance difference between Comparative Examples 1-2 is that the components of the regenerated DMT from the glycolysis-ester exchange product of waste textiles are complex, and a single purification method cannot obtain high-purity and high-quality regenerated DMT. Therefore, a combined purification method is required to obtain high-purity regenerated DMT.

[0085] From Figure Two , ThreeIt can be seen that, by using the multi-layer series filtration technology and the melting crystallization coupled rectification technology, the high-purity regenerated DMT can be obtained. The analysis by the high-efficiency gas chromatograph shows that the purity of the regenerated DMT is 99.80%. The analysis by the Fourier infrared analysis spectrometer shows that the purified regenerated DMT has similar characteristic peaks to the pure DMT. Table 1:

[0086]

Claims

1. A method for purifying waste polyester textile regeneration DMT, characterized by, It comprises the following steps: (1) Preparation of dye adsorbent A mixed solution containing soluble divalent metal salt and trivalent metal salt and a basic solution are prepared respectively, then the basic solution is added into the mixed solution, and the mixed solution is treated by hydrothermal reaction and vacuum drying to obtain layered double hydroxide flake; the cation in the soluble divalent metal salt is one or two of Cu 2+ , Zn 2+ , Ni 2+ , Mg 2+ , Fe 2+ ion, and the cation in the soluble trivalent metal salt is Al 3+ ion; the anion in the soluble divalent metal salt and the soluble trivalent metal salt is one or two of Cl - , NO3 - or SO4 2- ; the basic solution is urea, ammonia or sodium hydroxide; the temperature of the hydrothermal reaction is 95-110℃, and the time is 6-24h; (2) Preparation of modified fiber membrane The layered double hydroxide, porous dopamine and tannic acid are added into a buffer solution to obtain a suspension, and then a cellulose solution and a coagulant are added, and the mixture is stirred uniformly to obtain a modified cellulose casting solution. The casting solution is poured into a mold to form a film, and then the film is removed, vacuum cooled and dried to obtain a cellulose modified membrane with dye adsorption function. The mass ratio of the layered double hydrooxide, porous dopamine, tannic acid, cellulose and coagulant is 1:1-3:1-3:5:0.5, the buffer solution is one of Tris buffer, phosphate buffer, borate buffer and bicarbonate buffer, the coagulant is one of calcium chloride aqueous solution, hydrochloric acid aqueous solution or acetic acid aqueous solution, the stirring speed is 200 r / min, the stirring time is 10-20 h, the vacuum cooling temperature is-50℃, and the cooling time is 20 h. (3) Multi-layer series filtration technology Industrial filtration membranes and modified fiber membranes are assembled in a filter device in order from top to bottom, and methanol solution is used as the mobile phase to form a multi-layer series filtration from top to bottom to adsorb dye molecules in the DMT solution; the industrial filtration membranes are assembled in 1-2 layers, and the modified fiber membranes are assembled in 1-5 layers; the DMT solution is derived from the regenerated DMT of the glycol alcoholysis-methanol ester exchange product of waste polyester textiles. (4) Melting crystallization and rectification coupling technology The filtered DMT solution is sent into a melting crystallizer, and the crystallization process includes crystallization, sweating and melting. Then the DMT melt is sent into a rectification column, and high-purity DMT is obtained after cooling crystallization and drying of the DMT after rectification.

2. The purification method of waste polyester textile regeneration DMT according to claim 1, characterized in that, The porous dopamine in step (2) is commercially available.

3. The purification method of waste polyester textile regeneration DMT according to claim 1, characterized in that, In step (4), the crystallization temperature is 126-135℃, the crystallization time is 1.5-2h, the sweating temperature is 136-140℃, the sweating time is 2-4h, the melting temperature is 141-145℃, and the time is 1-2h.

4. The purification method of waste polyester textile regeneration DMT according to claim 1, characterized in that, In step (4), the rectification temperature is 280-300℃, and the rectification time is 2-5h.

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