BHET monomer decolorizing adsorption gel and preparation method thereof

Abstract

The invention provides decolorizing adsorption gel and a preparation method thereof. The method comprises the following steps: preparing a nanocellulose aqueous solution with the concentration of 2-10wt%, an anionic polyacrylamide aqueous solution with the concentration of 0.2-10wt%, a polyaluminum chloride aqueous solution with the concentration of 0.2-5wt% and an initiator aqueous solution with the concentration of 0.1-1wt%; the polyaluminum chloride aqueous solution also contains 0.1-1wt% of an accelerant; the preparation method comprises the following steps: mixing a nano cellulose aqueous solution, an anionic polyacrylamide aqueous solution, a polyaluminum chloride aqueous solution and an initiator aqueous solution according to a mass ratio of (1-10): (0.5-1): (0.5-1): (1-2), ultrasonically dispersing uniformly, and reacting at 90 + / -10 DEG C; and pouring the obtained gel stock solution into a mold for molding, and then performing freeze drying and ethylene glycol immersion cleaning to obtain the gel. The gel has a strong removal effect on ionic dyes and multi-size disperse dyes, and the whiteness of a BHET monomer can be remarkably improved.

Description

Technical Field

[0001] This application relates to the technical field of polymer chemical materials, and particularly relates to a BHET monomer decolorizing adsorption gel and a preparation method thereof. Background Art

[0002] Polyester fabrics are usually dyed with disperse dyes and ionic dyes. During the recycling process of polyester materials, polyester will first generate bis(2-hydroxyethyl) terephthalate (BHET) monomers through alcoholysis reaction, and then the BHET monomers need to be decolorized so that the BHET monomers can be further processed through polymerization, dyeing, etc. to form new products, realizing the recycling and reuse of polyester.

[0003] Among them, disperse dyes play a major role in the dyeing of polyester fabrics. During dyeing, these dyes are uniformly dispersed in the dye liquor in the form of fine particles and penetrate into the interior of polyester fibers under high temperature and high pressure conditions to combine with fiber molecules to form a firm color. However, during the recycling process of polyester materials, disperse dyes will be redispersed in the alcoholysis system of polyester, and thus it is difficult to effectively remove them when decolorizing BHET monomers.

[0004] Furthermore, at present, during the polyester recycling process, the decolorization methods of BHET monomers are divided into activated carbon adsorption method and filtration separation method after recrystallization, but these methods all have certain drawbacks.

[0005] For example, for the activated carbon adsorption method, on the one hand, the adsorption effect on disperse dyes is weak; on the other hand, the activated carbon needs to be frequently replaced, increasing the material cost; on the third hand, waste activated carbon needs to be regenerated, and the operation complexity is high.

[0006] For another example, for the filtration separation method after recrystallization, on the one hand, there is a strong physical embedding or chemical bonding between disperse dyes and polyester molecules, and the molecular structures of some disperse dyes are similar to those of alcoholysis products, so they are likely to remain in the crystals or solutions; on the other hand, the filtration media are mostly sintered metal and non-metal powders, with an average pore diameter of about 0.2 - 1 μm, but the particle sizes of most disperse dyes are below 0.2 μm, and it is difficult for these filtration media to achieve a good decolorization effect.

[0007] Therefore, neither activated carbon nor the filtration media in the filtration separation method can achieve a good effect on the decolorization of BHET monomers, affecting the recycling and reuse of polyester materials. Summary of the Invention

[0008] Aiming at the above technical status quo, the purpose of this application is to provide a BHET monomer decolorizing adsorption gel and a preparation method thereof, which can prepare a new copolymer by chemical method, with low side reactions during the reaction, high purity of the final product, and good performance.

[0009] To achieve the above-mentioned invention object, an embodiment of the present application provides a preparation method of a decolorizing adsorption gel. The preparation method includes:

[0010] Material preparation step: Prepare an aqueous solution of nanocellulose with a concentration of 2-10 wt%, an aqueous solution of anionic polyacrylamide with a concentration of 0.2-10 wt%, an aqueous solution of polyaluminum chloride with a concentration of 0.2-5 wt%, and an aqueous solution of an initiator with a concentration of 0.1-1 wt% respectively, and keep them at a temperature of 90±10°C for standby; wherein, the aqueous solution of polyaluminum chloride also contains 0.1-1 wt% of a promoter;

[0011] Reaction step: Mix the aqueous solution of nanocellulose, the aqueous solution of anionic polyacrylamide, the aqueous solution of polyaluminum chloride, and the aqueous solution of the initiator according to a mass ratio of (1-10):(0.5-1):(0.5-1):(1-2), and disperse them evenly by ultrasonic treatment. React under the conditions of maintaining a temperature of 90±10°C and a vacuum degree below 5 kPa or a protective atmosphere to obtain a gel stock solution;

[0012] Molding step: Pour the gel stock solution obtained in the reaction step into a mold for molding, and then perform freeze-drying and ethylene glycol immersion washing to obtain the decolorizing adsorption gel.

[0013] As a further improvement of an embodiment, in the material preparation step, the prepared aqueous solution of nanocellulose, the aqueous solution of anionic polyacrylamide, the aqueous solution of polyaluminum chloride, and the aqueous solution of the initiator are kept for standby in a protective atmosphere.

[0014] As a further improvement of an embodiment, in the material preparation step and / or the reaction step, the protective atmosphere is a nitrogen atmosphere.

[0015] As a further improvement of an embodiment, the material preparation step includes:

[0016] Mix the cellulose nanofibrils and water evenly and / or disperse them evenly by ultrasonic treatment to obtain an aqueous solution of nanocellulose, then introduce nitrogen to make the aqueous solution of nanocellulose in a nitrogen atmosphere, and then preheat it to 90±10°C for standby;

[0017] Mix the anionic polyacrylamide and water evenly and / or disperse them evenly by ultrasonic treatment to obtain an aqueous solution of anionic polyacrylamide, then introduce nitrogen to make the aqueous solution of anionic polyacrylamide in a nitrogen atmosphere, and then preheat it to 90±10°C for standby;

[0018] Stir the polyaluminum chloride, the promoter and water evenly at a temperature of 90±10°C to obtain an aqueous solution of polyaluminum chloride, then introduce nitrogen to make the aqueous solution of polyaluminum chloride in a nitrogen atmosphere, and keep it at 90±10°C for standby;

[0019] Mix the initiator with water at 90 ± 10 °C until evenly mixed to obtain an initiator aqueous solution. Then, introduce nitrogen gas so that the initiator aqueous solution is in a nitrogen atmosphere and maintain it at 90 ± 10 °C for standby.

[0020] As a further improvement of an embodiment, in the shaping step:

[0021] Perform pre-freezing and vacuum freeze-drying at a temperature of -18 ± 3 °C. After completion, wash the gel twice with ethylene glycol to obtain the decolorizing adsorption gel.

[0022] After completing the ethylene glycol washing, soak the obtained decolorizing adsorption gel in ethylene glycol for storage.

[0023] As a further improvement of an embodiment, the initiator is one or a combination of several of potassium persulfate, sodium bisulfite, benzoyl peroxide, and ammonium persulfate.

[0024] As a further improvement of an embodiment, the accelerator is one or a combination of several of sodium aluminate, calcium aluminate, calcium fluoroaluminate, and silicate.

[0025] As a further improvement of an embodiment, in the material preparation step:

[0026] The diameter of the nanocellulose used in the nanocellulose aqueous solution is 50 - 100 nm, and the aspect ratio is (100 - 1000):1.

[0027] To achieve the above invention purpose, an embodiment of the present application provides a decolorizing adsorption gel. The decolorizing adsorption gel contains [(Cell-O) y Al(APAM’) 3-y z , (Cell-O) x Al (3-x)+ any one or two of them;

[0028] Among them, the structural formula of the structural unit of [(Cell-O) y Al(APAM’) 3-y z is:

[0029]

[0030] The structural formula of the Cell-O· group is:

[0031]

[0032] The structural formula of the APAM’ group is:

[0033] ​​

[0034] As a further improvement of an embodiment, the decolorizing adsorption gel has a porous structure, and its porosity is 80-90% and the pore diameter is 0.05-0.2 μm.

[0035] Compared with the prior art, one or more technical solutions provided by the present application have at least the following technical effects or advantages:

[0036] (1) Based on the self-chemical structure of the chemical components in the decolorizing adsorption gel, strong adsorption of ionic dyes can be achieved.

[0037] (2) Based on the porous properties of the decolorizing adsorption gel itself, and characteristics such as small (below 0.2 μm) and controllable pore diameter, it can perfectly fit various sizes of disperse dyes and has a strong blocking effect on disperse dyes.

[0038] (3) Based on the above two points, it can have a strong removal effect on both ionic dyes and disperse dyes of various sizes. When applied in the process of recycling colored polyester materials, it can specifically and efficiently decolorize BHET monomers, improve the whiteness of BHET monomers, and thus increase the market competitiveness of the recycled polyester materials.

[0039] (4) Moreover, it can also eliminate the disadvantages of high material cost, high production cost, and high environmental protection cost caused by decolorization in the recycling of polyester materials, and has extremely strong economic value and environmental protection value. Description of the Drawings

[0040] Figure 1 is a flowchart of the preparation method of the decolorizing adsorption gel according to an embodiment of the present application;

[0041] Figure 2 is a physical photograph of the decolorizing adsorption gel in Example 1 of the present application;

[0042] Figure 3 is a microscopic enlarged view of the decolorizing adsorption gel in Example 1 of the present application;

[0043] Figure 4a is a physical photograph of the BHET monomer in the colored polyester recycling before decolorization;

[0044] Figure 4b is Figure 4a the physical picture of the BHET monomer in

[0045] Figure 4c is Figure 4a the physical photograph of the BHET monomer in Specific Embodiments

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] An embodiment of the present application provides a decolorizing adsorption gel and a preparation method thereof. When applied to the decolorization treatment of bis(2-hydroxyethyl) terephthalate (BHET) monomers, especially during the recycling process of colored polyester materials, after the polyester generates BHET monomers through alcoholysis reaction, for the decolorization treatment of such BHET monomers, the present application has outstanding advantages compared with activated carbon or filtration media in the prior art, and has excellent removal effects on both disperse dyes and ionic dyes.

[0048] Refer Figure 1 , in one embodiment of the present application, the preparation method includes the following three steps.

[0049] Stock preparation step: Prepare an aqueous solution of nanocellulose with a concentration of 2-10 wt%, an aqueous solution of anionic polyacrylamide with a concentration of 0.2-10 wt%, an aqueous solution of polyaluminum chloride with a concentration of 0.2-5 wt%, and an aqueous solution of initiator with a concentration of 0.1-1 wt% respectively, and keep them at a temperature of 90±10°C for standby; wherein, the aqueous solution of polyaluminum chloride also contains 0.1-1 wt% of accelerator;

[0050] Reaction step: Mix the aqueous solution of nanocellulose, the aqueous solution of anionic polyacrylamide, the aqueous solution of polyaluminum chloride, and the aqueous solution of initiator according to a mass ratio of (1-10):(0.5-1):(0.5-1):(1-2), and disperse them evenly by ultrasonic treatment, and carry out the reaction under the conditions of maintaining a temperature of 90±10°C, a vacuum degree below 5 kPa or a protective atmosphere to obtain a gel stock solution;

[0051] Molding step: Pour the gel stock solution obtained in the reaction step into a mold for molding, and then carry out freeze-drying and ethylene glycol immersion washing to obtain the decolorizing adsorption gel.

[0052] Thus, by reacting nanocellulose, anionic polyacrylamide, and polyaluminum chloride, a decolorizing adsorption gel is formed. In the decolorization treatment of BHET monomers, not only can strong adsorption of ionic dyes be achieved based on the chemical structure of the chemical components in the decolorizing adsorption gel, but also the pore size of the decolorizing adsorption gel is small (below 0.2 μm) and controllable, which can perfectly adapt to various sizes of disperse dyes and has a strong blocking effect on disperse dyes. Furthermore, targeted and efficient decolorization during the recycling process of colored polyester materials can be achieved, the whiteness of BHET monomers can be improved, and thus the market competitiveness of recycled polyester materials can be increased. Moreover, this application can also eliminate the disadvantages of high material costs, high production costs, and high environmental protection costs caused by decolorization during the recycling of polyester materials, and has extremely high economic value and environmental protection value.

[0053] The following is a detailed introduction to each step in sequence.

[0054] <Stock preparation step>

[0055] Based on Figure 1 It can be seen that this step is to prepare an aqueous solution of nanocellulose, an aqueous solution of anionic polyacrylamide, an aqueous solution of polyaluminum chloride, and an aqueous solution of initiator for use in subsequent reaction steps.

[0056] Among them, the "aqueous solution of nanocellulose with a concentration of 2 - 10 wt%" means that in the aqueous solution of nanocellulose, the mass percentage of nanocellulose is 2 - 10 wt%.

[0057] Correspondingly, in the aqueous solution of anionic polyacrylamide, the mass percentage of anionic polyacrylamide is 0.2 - 10 wt%; in the aqueous solution of polyaluminum chloride, the mass percentage of polyaluminum chloride is 0.2 - 5 wt%, and the mass percentage of the promoter is 0.1 - 1 wt%; in the aqueous solution of initiator, the mass percentage of initiator is 0.1 - 1 wt%.

[0058] Preferably, the prepared aqueous solution of nanocellulose, aqueous solution of anionic polyacrylamide, aqueous solution of polyaluminum chloride, and aqueous solution of initiator, when stored for later use, in addition to meeting the temperature condition of 90 ± 10 °C, can also be stored in a protective atmosphere. In this way, the oxygen in the air can be prevented from affecting the chemical reactions in the subsequent reaction steps, the occurrence of side reactions can be avoided, the purity of the reaction products can be improved, and thus the use effect in the decolorization of BHET monomers can be enhanced.

[0059] The protective atmosphere can be selected as a nitrogen atmosphere, which can not only achieve the protection effect but also has the advantage of low cost. Of course, other feasible protective atmospheres can also be chosen.

[0060] In an optional embodiment, the stock preparation step may specifically include:

[0061] Mix the cellulose nanofibrils evenly with water and / or disperse them evenly by ultrasonic treatment to obtain an aqueous solution of nanocellulose. Then, introduce nitrogen gas so that the aqueous solution of nanocellulose is in a nitrogen atmosphere, and preheat it to 90 ± 10 °C for standby.

[0062] Here, a specific preparation process of the aqueous solution of nanocellulose is introduced in detail. Among them: the duration of ultrasonic dispersion treatment can be more than 15 min, such as 15 - 45 min, preferably about 30 min; the duration of nitrogen gas introduction can be more than 10 min, such as 10 - 20 min, preferably about 15 min.

[0063] In an alternative embodiment, the material preparation step may specifically include:

[0064] Mix the anionic polyacrylamide evenly with water and / or disperse it evenly by ultrasonic treatment to obtain an aqueous solution of anionic polyacrylamide. Then, introduce nitrogen gas so that the aqueous solution of anionic polyacrylamide is in a nitrogen atmosphere, and preheat it to 90 ± 10 °C for standby.

[0065] Here, a specific preparation process of the aqueous solution of anionic polyacrylamide is introduced in detail. Among them: the duration of ultrasonic dispersion treatment can be more than 10 min, such as 10 - 20 min, preferably about 15 min; the duration of nitrogen gas introduction can be more than 10 min, such as 10 - 20 min, preferably about 15 min.

[0066] In an alternative embodiment, the material preparation step may specifically include:

[0067] Stir the polyaluminum chloride and the promoter evenly with water at a temperature of 90 ± 10 °C to obtain an aqueous solution of polyaluminum chloride. Then, introduce nitrogen gas so that the aqueous solution of polyaluminum chloride is in a nitrogen atmosphere, and maintain it at 90 ± 10 °C for standby.

[0068] Here, a specific preparation process of the aqueous solution of polyaluminum chloride is introduced in detail. Among them: the duration of stirring can be more than 5 min, such as 5 - 10 min. After mixing evenly, from the appearance, the solution is transparent and has no solid suspended particles; the duration of nitrogen gas introduction can be more than 10 min, such as 10 - 20 min, preferably about 15 min.

[0069] In an alternative embodiment, the material preparation step may further specifically include:

[0070] Mix the initiator evenly with water at 90 ± 10 °C to obtain an aqueous solution of the initiator. Then, introduce nitrogen gas so that the aqueous solution of the initiator is in a nitrogen atmosphere, and maintain it at 90 ± 10 °C for standby.

[0071] Here, a specific preparation process of the initiator aqueous solution is introduced in detail. Among them: the mixing process of the initiator and water can be carried out for more than 5 minutes, such as 5 - 10 minutes, preferably about 7 minutes; furthermore, the duration of nitrogen passing can be more than 10 minutes, such as 10 - 20 minutes, preferably about 15 minutes.

[0072] The above introduction to the specific preparation processes of the nano - cellulose aqueous solution, anionic polyacrylamide aqueous solution, polyaluminum chloride aqueous solution, and initiator aqueous solution gives some preferable timings for passing nitrogen or adjusting the temperature to the standby temperature (i.e., 90 ± 10 °C). However, it can be understood that the sequence can be adjusted when feasible in the art, as long as the requirements of the protective atmosphere and temperature are met in the final standby state.

[0073] Preferably, the diameter of the nano - cellulose used in the nano - cellulose aqueous solution is 50 - 100 nm, and the aspect ratio is (100 - 1000):1. In this way, the pore size of the finally prepared decolorizing adsorption gel can be appropriate, which not only meets the removal of disperse dyes but also avoids failure due to too small pore size.

[0074] When preparing the nano - cellulose aqueous solution using cellulose nanofibrils, that is, the diameter of the cellulose nanofibrils is 50 - 100 nm, and the aspect ratio is (100 - 1000):1.

[0075] Optionally, the initiator is one or a combination of several of potassium persulfate, sodium bisulfite, benzoyl peroxide, and ammonium persulfate.

[0076] Optionally, the accelerator is one or a combination of several of sodium aluminate, calcium aluminate, calcium fluoroaluminate, and silicate.

[0077] <Reaction step>

[0078] Based on Figure 1 It can be seen that in this step, the nano - cellulose aqueous solution, anionic polyacrylamide aqueous solution, polyaluminum chloride aqueous solution, and initiator aqueous solution prepared in the previous material preparation step are mixed according to the mass ratio of (1 - 10):(0.5 - 1):(0.5 - 1):(1 - 2), and ultrasonically dispersed evenly, and the reaction is carried out under the conditions of maintaining the temperature at 90 ± 10 °C, the vacuum degree below 5 kPa, or a protective atmosphere to obtain the gel stock solution.

[0079] Next, from the principle aspect, the chemical reactions involved in this step are introduced.

[0080] Cellulose is ionized under the action of the initiator to generate cellulose free radicals (i.e., Cell - O·), and the reaction is as follows in Equation ①.

[0081] CELL-OH+initiator→Cell-O·Formula ①

[0082] The cellulose free radicals generated in formula ① can react with polyaluminium chloride (PAC) ionized cations (such as Al 3+ ) undergoes coordination reaction as shown in formula ②; where x is between 1 and 3.

[0083] Cell-O·+Al 3+ →(Cell-O) x Al (3-x)+ Formula ②

[0084] In addition, more importantly, the cellulose free radicals generated in formula ① react with cations (such as Al 3+ ) and anions in anionic polyacrylamide (APAM) (e.g., removal of Na + The anion APAM formed later - ) to form a network cross-linked product, as shown in the following formula ③; wherein y is between 1 and 3.

[0085] Cell-O·+Al 3+ +APAM→[(Cell-O) y Al(APAM') 3-y ] z Formula ③

[0086] Based on this, it can be seen that in this step, the obtained gel stock solution contains [(Cell-O) y Al(APAM') 3-y ] z 、(Cell-O) x Al (3-x)+ Any one or two of the following. Among them, [(Cell-O) y Al(APAM') 3-y ] z Main network structure.

[0087] Furthermore, the decolorizing adsorption gel provided in one embodiment of the present application also contains [(Cell-O) y Al(APAM') 3-y ] z 、(Cell-O) x Al (3-x)+ Any one or two of the following. Among them, [(Cell-O) y Al(APAM') 3-y ] z Main network structure.

[0088] The above is the structural formula of cellulose free radical Cell-O·, or [(Cell-O)y Al(APAM’) 3-y z and (Cell-O) x Al (3-x)+ The structural formula of the Cell-O· group in is as follows:

[0089]

[0090] Furthermore, [(Cell-O) y Al(APAM’) 3-y z The APAM’ group in, and the anionic APAM - both have the structural formula:

[0091]

[0092] Correspondingly, the structural formula of the structural unit of [(Cell-O) y Al(APAM’) 3-y z is:

[0093]

[0094] Thus, due to the influence of its chemical composition, the decolorizing adsorption gel has a super strong adsorption capacity for ionic dyes, and can effectively improve the whiteness of BHET monomers during the recycling process of colored polyester materials.

[0095] In an alternative embodiment, in this step, after the aqueous solution of nanocellulose, the aqueous solution of anionic polyacrylamide, the aqueous solution of polyaluminum chloride, and the aqueous solution of initiator are mixed, when ultrasonic dispersion is carried out, in addition to achieving the effect of uniform ultrasonic dispersion, the gas in the mixed solution can also be discharged by means of ultrasonic dispersion.

[0096] Preferably, the duration of ultrasonic dispersion can be 5 minutes or more, for example, 5 - 15 minutes.

[0097] In addition, the reaction vessel where the mixed solution is located can maintain a temperature of 90 ± 10 °C for the reaction. Maintaining the temperature can facilitate the efficient progress of the reaction and avoid side reactions.

[0098] In addition, while maintaining the temperature, the reaction vessel where the mixed solution is located can also maintain a vacuum degree of 5 kPa or less, for example, 1 - 5 kPa, and of course, it can also be 1 kPa or less, or maintain a protective atmosphere, such as a nitrogen atmosphere. In this way, by evacuating or introducing nitrogen to displace the air therein, the adverse effects of the gas in the environment (especially oxygen) on the reaction can be avoided, and side reactions can be avoided.

[0099] ​​​Optionally, in this step, the reaction duration can be controlled to be more than 2 h to ensure a full and complete reaction. For example, it can be 2 - 3 h, but not limited to this.

[0100] <Forming step>

[0101] See Figure 1 As shown, in this step, the gel stock solution obtained from the reaction step is poured into a mold for forming, and then freeze-dried and washed with ethylene glycol to obtain the decolorizing and adsorbing gel.

[0102] Based on the foregoing introduction, it can be known that this decolorizing and adsorbing gel contains [(Cell-O) y Al(APAM’) 3-y z 、(Cell-O) x Al (3-x)+ Either one or both of them. Thus, due to the influence of its chemical composition, it has a super strong adsorption capacity for ionic dyes, and can effectively improve the whiteness of BHET monomers during the recycling process of colored polyester materials.

[0103] At the same time, this decolorizing and adsorbing gel is formed based on nanocellulose, making it a porous structure with small pore size (below 0.2 μm) and controllable pore size, which can perfectly adapt to various sizes of disperse dyes and has a strong barrier effect on disperse dyes.

[0104] In summary, in one embodiment of the present application, the decolorizing and adsorbing gel can have a strong removal effect on both ionic dyes and disperse dyes of various sizes. When applied in the recycling process of colored polyester materials, it can decolorize specifically and efficiently, improve the whiteness of BHET monomers, and increase the market competitiveness of the recycled polyester materials; moreover, the present application can also eliminate the disadvantages of high material cost, high production cost, and high environmental protection cost caused by decolorization in the polyester material recycling, and has extremely high economic value and environmental protection value.

[0105] In one embodiment, the porosity of the decolorizing and adsorbing gel is 80 - 90% and the pore size is 0.05 - 0.2 μm. In this way, the barrier effect on disperse dyes can be further ensured to achieve efficient decolorization.

[0106] Preferably, in the forming step: pre-freezing and vacuum freeze-drying can be carried out at a temperature of -18 ± 3°C.

[0107] ​The pre-freezing temperature is -18 ± 3°C for a duration of 2 to 4 hours; the temperature for vacuum freeze-drying is -18 ± 3°C, and the vacuum degree is -0.085 to -0.095 Mpa. The specific processing duration can be more than 1 hour, for example, 1 to 1.5 hours. Of course, it is also possible to judge whether the vacuum freeze-drying is completed according to the weight change of the freeze-drying chamber. For example, when the change rate or change amount per unit time of the freeze-drying chamber is lower than a preset value, it can be considered that the vacuum freeze-drying is completed. These methods for judging the completion of vacuum freeze-drying are well-known to those skilled in the art and will not be elaborated in this application.

[0108] More preferably, in the shaping step: after the vacuum freeze-drying is completed, the gel is washed with ethylene glycol two or more times to obtain the decolorizing and adsorbing gel.

[0109] By washing with ethylene glycol, the chemicals remaining inside the gel, such as initiators, accelerators, etc., can be removed.

[0110] In addition, in the shaping step: after the ethylene glycol washing is completed, the obtained decolorizing and adsorbing gel can be immersed in ethylene glycol for storage. On the one hand, it can ensure that the properties of the gel do not deteriorate, and on the other hand, it can also prevent the gel from being contaminated.

[0111] In summary, the reticular decolorizing and adsorbing gel provided by an embodiment of this application, and the preparation method of this decolorizing and adsorbing gel, have the following beneficial effects compared with the prior art:

[0112] (1) Based on the self-chemical structure of the chemical components in the decolorizing and adsorbing gel, it can achieve a strong adsorption of ionic dyes;

[0113] (2) Based on the porous properties of the decolorizing and adsorbing gel itself, as well as the characteristics of small pore size (below 0.2 μm) and controllable pore size, it can perfectly adapt to various sizes of disperse dyes and has a strong blocking effect on disperse dyes;

[0114] (3) Based on the above two points, it can have a strong removal effect on both ionic dyes and disperse dyes of various sizes. When applied in the process of recycling colored polyester materials, it can specifically and efficiently decolorize BHET monomers, improve the whiteness of BHET monomers, and thus increase the market competitiveness of the recycled polyester materials;

[0115] (4) Moreover, it can also eliminate the disadvantages of high material cost, high production cost, and high environmental protection cost caused by decolorization in the recycling of polyester materials, and has extremely strong economic value and environmental protection value.

[0116] Next, some specific embodiments are combined to further illustrate the technical solutions and effects of this application.

[0117] Example 1

[0118] Example 1 prepared a decolorizing adsorption gel, which is as follows:

[0119] (1) Prepare an aqueous solution of nanocellulose with a concentration of 10 wt%, an aqueous solution of anionic polyacrylamide with a concentration of 10 wt%, an aqueous solution of polyaluminum chloride with a concentration of 5 wt% (containing 1 wt% calcium aluminate), and an aqueous solution of potassium persulfate with a concentration of 1 wt%, and keep it at a temperature of 90 ± 10 °C for standby;

[0120] (2) Take 100 g of the aqueous nanocellulose solution, 7.5 g of the aqueous anionic polyacrylamide solution, 10 g of the aqueous polyaluminum chloride solution, and 10 g of the aqueous potassium persulfate solution, add them into a 2 L reaction kettle for mixing, and disperse them evenly by ultrasonic wave. Keep the temperature at 90 °C and the vacuum degree below 5 kPa for reaction. After 2 h, the reaction is terminated to obtain the gel stock solution;

[0121] (3) Pour the gel stock solution into a circular mold for molding, and then freeze-dry it together with the mold and wash it twice with ethylene glycol to obtain a block, which is the decolorizing adsorption gel.

[0122] Refer Figure 2 , which shows a physical picture of the decolorizing adsorption gel prepared in this example.

[0123] Furthermore, refer Figure 3 , the decolorizing adsorption gel is a porous structure. Sampled and tested according to GB21650.2-2008, its porosity is 80%, and the pore size is in the range of 0.05 - 0.2 μm.

[0124] In addition, in the recycling of colored polyester, the alcoholysis product BHET monomer is decolorized with the decolorizing adsorption gel of this example. The physical picture of the BHET monomer before decolorization is as Figure 4a shown, the physical picture after decolorization by activated carbon filtration is as 4b, and the physical picture after decolorization by the adsorption gel is as Figure 4c shown. It can be seen that the whiteness of the BHET monomer is significantly improved, and the decolorization effect is remarkable.

Claims

1. A method for preparing a decolorizing adsorption gel, characterized in that: The preparation method comprises: Preparation step: preparing a nanocellulose aqueous solution with a concentration of 2 to 10 wt%, an anionic polyacrylamide aqueous solution with a concentration of 0.2 to 10 wt%, a polyaluminium chloride aqueous solution with a concentration of 0.2 to 5 wt%, and an initiator aqueous solution with a concentration of 0.1 to 1 wt%, respectively, and maintaining the temperature at 90±10° C. for standby use; wherein the polyaluminium chloride aqueous solution also contains 0.1 to 1 wt% of an accelerator; Reaction step: mixing the nanocellulose aqueous solution, the anionic polyacrylamide aqueous solution, the polyaluminium chloride aqueous solution and the initiator aqueous solution in a mass ratio of (1-10):(0.5-1):(0.5-1):(1-2), and uniformly dispersing by ultrasonication, and reacting under the conditions of maintaining a temperature of 90±10°C and a vacuum degree of less than 5 kPa or a protective atmosphere to obtain a gel stock solution; Forming step: pouring the gel stock solution obtained in the reaction step into a mold for forming, followed by freeze drying and ethylene glycol soaking to obtain the decolorized adsorption gel.

2. The method for preparing the decolorizing adsorption gel according to claim 1, characterized in that: In the material preparation step, the prepared nanocellulose aqueous solution, anionic polyacrylamide aqueous solution, polyaluminium chloride aqueous solution and initiator aqueous solution are placed in a protective atmosphere for use.

3. The method for preparing the decolorizing adsorption gel according to claim 2, characterized in that: In the material preparation step and / or the reaction step, the protective atmosphere is a nitrogen atmosphere.

4. The method for preparing the decolorizing adsorption gel according to any one of claims 1 to 3, characterized in that: The material preparation step comprises: The cellulose nanofibrils are uniformly mixed with water and / or ultrasonically dispersed to obtain a nanocellulose aqueous solution, and then nitrogen is introduced to make the nanocellulose aqueous solution in a nitrogen atmosphere, and then preheated to 90±10° C. for use; The anionic polyacrylamide and water are uniformly mixed and / or ultrasonically dispersed to obtain an anionic polyacrylamide aqueous solution, and then nitrogen is introduced to make the anionic polyacrylamide aqueous solution in a nitrogen atmosphere, and then preheated to 90±10° C. for use; The polyaluminium chloride, accelerator and water are stirred uniformly at a temperature of 90±10° C. to obtain a polyaluminium chloride aqueous solution, and then nitrogen is introduced to make the polyaluminium chloride aqueous solution in a nitrogen atmosphere, and the temperature is maintained at 90±10° C. for standby use; The initiator was mixed evenly with water at 90±10°C to obtain an initiator aqueous solution, and then nitrogen was introduced to make the initiator aqueous solution be in a nitrogen atmosphere, and maintained at 90±10°C for use.

5. The method for preparing the decolorizing adsorption gel according to claim 1, characterized in that: In the forming step: Pre-freezing and vacuum freeze drying are performed at a temperature of -18±3°C, and after completion, the gel is rinsed with ethylene glycol twice to obtain the decolorized adsorption gel; After the ethylene glycol leaching is completed, the obtained decolorized adsorption gel is immersed in ethylene glycol for storage.

6. The method for preparing the decolorizing adsorption gel according to claim 1, characterized in that: The initiator is one or a combination of potassium persulfate, sodium bisulfite, benzoyl peroxide, and ammonium persulfate.

7. The method for preparing the decolorizing adsorption gel according to claim 1, characterized in that: The promoter is one or a combination of sodium aluminate, calcium aluminate, calcium fluoroaluminate and silicate.

8. The method for preparing the decolorizing adsorption gel according to claim 1, characterized in that: In the material preparation step: The diameter of the nanocellulose used in the nanocellulose aqueous solution is 50-100 nm, and the aspect ratio is (100-1000):

1.

9. A decolorizing adsorption gel, characterized in that: The decolorizing adsorption gel contains [(Cell-O) y Al(APAM') 3-y ] z 、(Cell-O) x Al (3-x)+ Either or both of the following: Among them, [(Cell-O) y Al(APAM') 3-y ] z The structural formula of the structural unit is: The structural formula of Cell-O· group is: The structural formula of the APAM' group is:

10. The decolorizing adsorption gel according to claim 9, characterized in that: The decolorizing adsorption gel is a porous structure, and its porosity is 80-90% and its pore size is 0.05-0.2 μm.

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