Method for preparing cured tannic acid by radiation initiation method

Abstract

The invention relates to a method for preparing cured tannic acid through a radiation initiation method, and belongs to the technical field of functional materials. The preparation method comprises the following steps: preparing spherical cellulose by utilizing a soft template method, forming a water-in-oil (W / O) system by hydrophobic organic solvent paraffin and cellulose, adding span80 to avoid layering and agglomeration of water-phase liquid drops in an oil phase so as to form the spherical cellulose, and adding ultrasonic energy to promote the cellulose to form a porous spheroid; cellulose is radiated to obtain cellulose containing a carbon center free radical, when the free radical is in contact with GMA (glycidyl methacrylate), the carbon center free radical is in contact with C on the GMA to generate bridging reaction, the GMA can be connected to the cellulose only through one step, and the GMA has double effects of bridging and epoxy activation, so that the GMA can be used for preparing a high-temperature-resistant epoxy resin material for the high-temperature-resistant epoxy resin material for the high-temperature-resistant epoxy resin material for the high-temperature-resistant epoxy resin material. And the tannic acid can be connected without other reagents to prepare the cured tannic acid. The method is simple, the grafting rate is high, the tannic acid content in the formed cured tannic acid can reach 20 wt.%, and the adsorption equilibrium amount of the cured tannic acid to germanium can still reach 9.97 mg / g after the cured tannic acid is circulated for 10 times.

Description

Technical Field

[0001] This invention relates to a method for preparing cured tannic acid by radiation initiation, belonging to the field of functional materials technology. Background Technology

[0002] Germanium is a key metal supporting the development of industries such as infrared optics, fiber optic communication, and photovoltaic cells. With a content of only ~1.5 ppm in the Earth's crust, efficient enrichment of germanium has always been a major challenge hindering industry development. The most common current method for germanium enrichment is tannic acid precipitation. Tannic acid can form stable complex precipitates with germanium, almost unaffected by common impurity ions. However, this method suffers from the problem of high tannic acid consumption (30 times the amount required), a significant reason being the easy hydrolysis of tannic acid, necessitating its solidification.

[0003] Currently, the main method for curing tannic acid involves crosslinking it onto macromolecular substrates such as chitosan, cellulose, and styrene. Patent CN201510647695.7 reports a method for preparing a cured tannic acid adsorbent resin. This involves first obtaining a tannic acid-based phenolic resin through phenolic condensation, and then crosslinking carboxymethyl cellulose with tannic acid using epichlorohydrin as a crosslinking agent. However, the phenolic condensation grafting rate is not high. Patent CN200910065915.X reports a method for preparing a tannic acid-cured chitosan adsorbent. This method involves adding chitosan particles to tannic acid and then adding epichlorohydrin for crosslinking. Although the use of epichlorohydrin improves the grafting rate, it cannot completely activate the substrate and tannic acid, leaving some groups ungrafted. Patent CN200810103131.7 discloses a method for preparing a cured tannic acid macroporous adsorption resin, which uses the Mannich reaction to fix plant tannic acid onto a styrene-divinylbenzene copolymer. However, the reaction process requires the addition of formaldehyde and amines, resulting in a low grafting rate and a lengthy process. In summary, the curing of tannic acid onto organic macromolecules such as cellulose, chitosan, and styrene suffers from drawbacks such as low grafting rates and lengthy processes. Summary of the Invention

[0004] To address the problems of low grafting rates and lengthy processes in existing methods for solidifying tannic acid in organic macromolecules such as cellulose, chitosan, and styrene, this invention proposes a radiation-initiated method for preparing solidified tannic acid. Spherical cellulose is prepared using a soft-template method, followed by ultrasonication to obtain porous spherical cellulose. Subsequently, high-energy irradiation is used to obtain cellulose containing carbon-centered free radicals, which can then be bridged with GMA. The resulting GMA-porous cellulose can directly bridge tannic acid to solidified tannic acid. The final solidified tannic acid can contain up to 20 wt.% tannic acid, and after 10 cycles, the adsorption equilibrium of germanium in the solidified tannic acid still reaches 9.97 mg / g.

[0005] A method for preparing cured tannic acid by radiation initiation, the specific steps of which are as follows: (1) Cellulose is ball-milled to obtain cellulose powder, which is then added to an alkaline solution and mixed evenly. The mixture is then frozen and microwaved to obtain cellulose liquid. (2) The cellulose liquid, liquid paraffin and surfactant are mixed evenly, and ultrasonically emulsified to obtain an emulsion. The emulsion is spray-dried and washed with ethanol to obtain porous cellulose. (3) Porous cellulose is treated with electron radiation to obtain free radical-porous cellulose; glycidyl methacrylate (GMA) is heated in vacuum to form GMA vapor; under vacuum conditions, GMA vapor is passed into free radical-porous cellulose to react and obtain GMA-porous cellulose. (4) Tannic acid is dissolved in industrial water to obtain tannic acid solution. Under a protective gas atmosphere, GMA-porous cellulose is added to the tannic acid solution to react. The solid and liquid are separated, and the solid is washed with deionized water and dried at low temperature to obtain cured tannic acid.

[0006] Preferably, in step (1), the particle size of the cellulose powder is 75~185um, the alkali solution is NaOH solution or KOH solution, the mass concentration of the alkali solution is 8~25%, and the liquid-solid ratio of the alkali solution to the cellulose powder is 5:1~15:1 mL:g.

[0007] Preferably, in step (1), the freezing temperature is -20~0℃, the freezing time is 1~3h, and the microwave thawing power is 60~80kW / m 3 .

[0008] Preferably, the surfactant in step (2) is a Span80-Tween80 composite surfactant, the mass ratio of Span80 to Tween80 is 1:1 to 4:1, the amount of Span80-Tween80 composite surfactant added is 0.5% to 3% of the volume of liquid paraffin, and the volume ratio of liquid paraffin to cellulose liquid is 5:1 to 10:1.

[0009] Preferably, the ultrasonic emulsification intensity in step (2) is 0.25~0.45 W / cm. 2 The emulsification time is 5~15min, the emulsification temperature is 20~40℃; the spray drying inlet temperature is 120~160℃, the outlet temperature is 60~80℃, the feed rate is 5~15mL / min, and the atomization pressure is 0.2~0.5MPa.

[0010] Preferably, the electron radiation treatment in step (3) uses a high-frequency high-voltage electron accelerator with an energy of 1.5~3MeV, a beam current of 1~5mA, and an radiation time of 10~30s; the vacuum heating temperature is 120~140℃, the vacuum degree is 0.01~0.05MPa, the GMA vapor is 0.1~0.5% of the porous cellulose mass, the reaction temperature is 40~60℃, and the reaction time is 2~6h.

[0011] Preferably, in step (4), the concentration of tannic acid solution is 5~20 wt.%, the mass ratio of tannic acid to GMA-porous cellulose is 5.5~20.5%, and the protective gas is nitrogen or an inert gas.

[0012] Preferably, the reaction temperature in step (4) is 50~65℃, the reaction time is 3~6h, the protective gas introduction rate is 1~5mL / min, and the low-temperature drying temperature is 40~60℃.

[0013] Preferably, the tannic acid content in the solidified tannic acid in step (4) is 5~20wt.%; after 10 cycles of solidified tannic acid, the adsorption equilibrium amount of solidified tannic acid for germanium can still reach 2.49~9.97mg / g.

[0014] The beneficial effects of this invention are: (1) In this invention, spherical cellulose is prepared by a soft template method. The hydrophobic organic solvent paraffin forms a "water-in-oil (W / O)" system with cellulose. The addition of Span80 prevents the aqueous phase droplets from easily separating and agglomerating in the oil phase, thereby forming spherical cellulose. The addition of ultrasound can promote the formation of porous spherical bodies of cellulose. (2) The present invention directly irradiates cellulose to form cellulose containing carbon center free radicals. When the free radicals come into contact with GMA, the carbon center free radicals come into contact with the C on GMA and a bridging reaction occurs. GMA can be bridged to cellulose in only one step, and the steps are simple. (3) The GMA of the present invention has the dual functions of bridging and epoxy activation. It can connect tannic acid to prepare solidified tannic acid without the need for other reagents. The tannic acid content in the final solidified tannic acid is as high as 20wt.%. After 10 cycles, the adsorption equilibrium amount of germanium by the solidified tannic acid can still reach 9.97mg / g. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the present invention; Figure 2 Here is a SEM image of the porous cellulose from Example 1; Figure 3 Here are actual images and pore size distribution diagrams of GMA-porous cellulose from Example 1; Figure 4 This is a photograph of the cured tannic acid from Example 1. Figure 5 This is a TEM-MAPPING image of germanium precipitated from cured tannic acid in Example 2. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0017] Example 1: A method for preparing cured tannic acid by radiation initiation (see Figure 1 The specific steps are as follows: (1) Cellulose was ball-milled to obtain cellulose powder with an average particle size of 185 μm. The cellulose powder was added to an alkaline solution (8% KOH solution) and mixed evenly (mixing time 20 min). The mixture was then frozen at 0 °C for 1 h and then thawed by microwave (microwave power 60 kW / m). 3 A cellulose solution was obtained; the liquid-to-solid ratio of the alkaline solution (KOH solution) to the cellulose powder was 5:1 (mL:g). (2) The cellulose solution, liquid paraffin, and surfactant (Span80-Tween80 composite surfactant, with a mass ratio of Span80 to Tween80 of 1:1) were mixed evenly and ultrasonically emulsified at room temperature for 5 minutes (ultrasonic intensity of 0.25 W / cm). 2 The emulsion was obtained by spray drying (inlet temperature 120℃, outlet temperature 60℃, feed rate 15mL / min, atomization pressure 0.2MPa), and porous cellulose was obtained by washing with ethanol; the amount of Span80-Tween80 composite activator added was 0.5% of the volume of liquid paraffin, and the volume ratio of liquid paraffin to cellulose liquid was 5:1. The SEM image of the porous cellulose in this embodiment is shown below. Figure 2 ,from Figure 2 It can be seen that porous cellulose exhibits a stacked microporous structure, with individual cellulose particles being approximately 8 μm in size. (3) Porous cellulose is treated with electron radiation to obtain free radical-porous cellulose; the electron radiation treatment adopts a high frequency high voltage electron accelerator with an energy of 1.5 MeV, a beam current of 1 mA, and a radiation time of 10 s; Glycidyl methacrylate (GMA) is heated under vacuum (120°C, 0.01 MPa) to produce GMA vapor. Under vacuum conditions (0.01 MPa), GMA vapor was introduced into free radical-porous cellulose and reacted at 40°C for 2 hours to obtain GMA-porous cellulose; the GMA vapor accounted for 0.1% of the mass of the porous cellulose. The physical image and pore size distribution diagram of GMA-porous cellulose in this embodiment are shown below. Figure 3 ,from Figure 3 It can be seen that GMA-porous cellulose exhibits a porous structure with pore diameters mostly around 3-10 nm, and is mainly a mesoporous structure; (4) Tannic acid was dissolved in industrial water to obtain a tannic acid solution with a concentration of 5 wt.%. Under a protective gas atmosphere (nitrogen gas introduced at a rate of 1 mL / min), GMA-porous cellulose was added to the tannic acid solution and reacted at 50°C for 3 h. The solid and liquid were separated, and the solid was washed with deionized water and dried at a low temperature of 40°C to obtain cured tannic acid. The mass ratio of tannic acid to GMA-porous cellulose was 5.5%. The actual image of the cured tannic acid in this embodiment can be found here. Figure 4 ,from Figure 4 As can be seen, the solidified tannic acid mainly exhibits a granular structure; In this embodiment, the tannic acid content in the cured tannic acid is 5 wt.%, and after 10 cycles, the adsorption equilibrium of the cured tannic acid for germanium can still reach 2.49 mg / g.

[0018] Example 2: A method for preparing cured tannic acid by radiation initiation (see Example 2) Figure 1 The specific steps are as follows: (1) Cellulose was ball-milled to obtain cellulose powder with an average particle size of 150 μm. The cellulose powder was added to an alkaline solution (15% NaOH solution) and mixed evenly (mixing time was 30 min). The mixture was then frozen at -10℃ for 2 h and then thawed by microwave (microwave power was 70 kW / m). 3 A cellulose solution was obtained; the liquid-to-solid ratio of the alkaline solution (NaOH solution) to the cellulose powder was 10:1 (mL:g). (2) The cellulose solution, liquid paraffin, and surfactant (Span80-Tween80 composite surfactant, with a mass ratio of Span80 to Tween80 of 2:1) were mixed evenly and ultrasonically emulsified at room temperature for 10 minutes (ultrasonic intensity of 1.34 W / cm). 2 The emulsion was obtained by spray drying (inlet temperature 140℃, outlet temperature 70℃, feed rate 10mL / min, atomization pressure 0.35MPa), and porous cellulose was obtained by washing with ethanol; the amount of Span80-Tween80 composite activator added was 1.5% of the volume of liquid paraffin, and the volume ratio of liquid paraffin to cellulose liquid was 8:1. (3) Porous cellulose is treated with electron radiation to obtain free radical-porous cellulose; the electron radiation treatment adopts a high frequency high voltage electron accelerator with an energy of 2MeV, a beam current of 2mA, and an radiation time of 20s; Glycidyl methacrylate (GMA) is heated under vacuum (130°C, 0.03 MPa) to produce GMA vapor. Under vacuum conditions (0.03 MPa), GMA vapor was introduced into free radical-porous cellulose and reacted at 50°C for 4 hours to obtain GMA-porous cellulose; the GMA vapor accounted for 0.2% of the mass of the porous cellulose. (4) Tannic acid was dissolved in industrial water to obtain a tannic acid solution with a concentration of 10 wt.%. Under a protective gas atmosphere (argon gas with a flow rate of 3 mL / min), GMA-porous cellulose was added to the tannic acid solution and reacted at 55°C for 4 h. The solid and liquid were separated, and the solid was washed with deionized water and dried at a low temperature of 50°C to obtain cured tannic acid. The mass ratio of tannic acid to GMA-porous cellulose was 15.5%. In this embodiment, the TEM-MAPPING after curing tannic acid adsorbing germanium is as follows: Figure 5 As shown, from Figure 5 As can be seen, the distribution of Ge is basically the same as that of C and O, and the Ge content is approximately 3.51%. In this embodiment, the tannic acid content in the cured tannic acid is 15 wt.%, and after 10 cycles, the adsorption equilibrium of the cured tannic acid for germanium can still reach 7.47 mg / g.

[0019] Example 3: A method for preparing cured tannic acid by radiation initiation (see Example 4) Figure 1 The specific steps are as follows: (1) Cellulose was ball-milled to obtain cellulose powder with an average particle size of 75 μm. The cellulose powder was added to an alkaline solution (25% NaOH solution) and mixed evenly (mixing time was 40 min). The mixture was then frozen at -20℃ for 3 h and then thawed by microwave (microwave power was 80 kW / m²). 3 A cellulose solution was obtained; the liquid-to-solid ratio of the alkaline solution (NaOH solution) to the cellulose powder was 15:1 (mL:g). (2) The cellulose solution, liquid paraffin, and surfactant (Span80-Tween80 composite surfactant, with a mass ratio of Span80 to Tween80 of 4:1) were mixed evenly and ultrasonically emulsified at room temperature for 15 minutes (ultrasonic intensity of 0.45 W / cm). 2 The emulsion was obtained by spray drying (inlet temperature 160℃, outlet temperature 80℃, feed rate 15mL / min, atomization pressure 0.5MPa), and porous cellulose was obtained by washing with ethanol; the amount of Span80-Tween80 composite activator added was 3% of the volume of liquid paraffin, and the volume ratio of liquid paraffin to cellulose liquid was 10:1. (3) Porous cellulose is treated with electron radiation to obtain free radical-porous cellulose; the electron radiation treatment adopts a high frequency high voltage electron accelerator with an energy of 3MeV, a beam current of 5mA, and a radiation time of 30s; Glycidyl methacrylate (GMA) is heated under vacuum (140°C, 0.05 MPa) to produce GMA vapor. Under vacuum conditions (0.05 MPa), GMA vapor was introduced into free radical-porous cellulose and reacted at 60°C for 6 hours to obtain GMA-porous cellulose; the GMA vapor accounted for 0.5% of the mass of the porous cellulose. (4) Tannic acid was dissolved in industrial water to obtain a tannic acid solution with a concentration of 20 wt.%. Under a protective gas atmosphere (nitrogen gas with a flow rate of 5 mL / min), GMA-porous cellulose was added to the tannic acid solution and reacted at 65°C for 6 h. The solid and liquid were separated, and the solid was washed with deionized water and dried at a low temperature of 60°C to obtain cured tannic acid. The mass ratio of tannic acid to GMA-porous cellulose was 20.5%. In this embodiment, the tannic acid content in the cured tannic acid is 20 wt.%, and after 10 cycles, the adsorption equilibrium of the cured tannic acid for germanium can still reach 9.97 mg / g.

[0020] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for the preparation of a cured tannin by a radiation-induced process, characterized in that, The specific steps are as follows: (1) cellulose powder is obtained by ball milling of cellulose spheres, the cellulose powder is added into alkali liquor and uniformly mixed, then frozen and thawed by microwave to obtain cellulose liquid; (2) the cellulose liquid, liquid paraffin and surfactant are uniformly mixed, ultrasonic emulsification is performed to obtain emulsion, the emulsion is spray dried, and then washed with ethanol to obtain porous cellulose; (3) the porous cellulose is treated by electron irradiation to obtain free radical-porous cellulose; glycidyl methacrylate (GMA) is heated under vacuum to obtain GMA vapor; the GMA vapor is introduced into the free radical-porous cellulose under vacuum to obtain GMA-porous cellulose; (4) tannic acid is dissolved in industrial water to obtain tannic acid liquid, the GMA-porous cellulose is added into the tannic acid liquid under a protective gas atmosphere to react, solid-liquid separation is performed, the solid is washed with deionized water, and low-temperature drying is performed to obtain solidified tannic acid.

2. The method of claim 1, wherein the method of preparing the cured tannin is characterized by: In step (1), the particle size of the cellulose powder is 75-185 um, the alkali liquor is NaOH solution or KOH solution, the mass concentration of the alkali liquor is 8-25%, and the liquid-solid ratio (mL:g) of the alkali liquor to the cellulose powder is 5:1-15:

1.

3. The method of claim 1, wherein the method of preparing the cured tannin is characterized by: Step (1) freezing temperature is -20~0℃, freezing time is 1~3h, microwave thawing power is 60~80kW / m 3 .

4. The method of claim 1, wherein the method of preparing the cured tannin is characterized by: In step (2), the surfactant is Span80-Tween80 composite active agent, the mass ratio of Span80 to Tween80 is 1:1-4:1, the addition amount of the Span80-Tween80 composite active agent is 0.5%-3% of the volume of the liquid paraffin, and the volume ratio of the liquid paraffin to the cellulose liquid is 5:1-10:

1.

5. The method of claim 1, wherein the method of preparing the cured tannin is characterized by: Step (2) ultrasonic emulsification intensity is 0.25~0.45W / cm 2 , emulsification time is 5~15min, emulsification temperature is 20~40℃; spray drying inlet temperature 120~160℃, outlet temperature 60~80℃, feed rate 5~15mL / min, atomization pressure 0.2~0.5MPa.

6. The method of claim 1, wherein the tannin is prepared by the radiation-induced method. In step (3), the electron irradiation treatment is performed by using a high-frequency high-voltage electron accelerator, the energy is 1.5-3 MeV, the beam current is 1-5 mA, and the irradiation time is 10-30 s; the vacuum heating temperature is 120-140℃, the vacuum degree is 0.01-0.05 MPa, the GMA vapor is 0.1-0.5% of the mass of the porous cellulose, the reaction temperature is 40-60℃, and the reaction time is 2-6 h.

7. The method of claim 1, wherein the tannin is prepared by the radiation-induced method, characterized in that: In step (4), the concentration of the tannic acid liquid is 5-20 wt.%, the mass ratio of the tannic acid to the GMA-porous cellulose is 5.5-20.5%, and the protective gas is nitrogen or inert gas.

8. The method of claim 1, wherein the tannin is prepared by the radiation-induced method, characterized by: In step (4), the reaction temperature is 50-65℃, the reaction time is 3-6 h, the protective gas is introduced at a rate of 1-5 mL / min, and the low-temperature drying temperature is 40-60℃.

9. The method of claim 1, wherein the tannin is prepared by the radiation-induced method, and is characterized by: In step (4), the content of tannic acid in the solidified tannic acid is 5-20 wt.%.

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