CN111875006A - Preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode - Google Patents

Abstract

The preparation method of biomass source N and P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode is based on cheap natural biomass with natural plant fiber sponge structure, such as agricultural processing waste grapefruit peel and bagasse. The raw materials are prepared by pre-carbonization and high-temperature carbonization to prepare N, P co-doped carbon aerogel with developed mesoporous structure, and further use N, P co-doped carbon aerogel and chitosan to composite to prepare an electro-adsorption film The electrode is used for the separation of uranium in uranium-containing wastewater by electrosorption, thereby reducing the production cost and improving the material performance. The prepared biomass source N, P co-doped carbon aerogel/chitosan composite membrane electrode has a high specific surface area , Good electrical conductivity and chemical stability, when used for the separation of uranium in uranium-containing wastewater by electrosorption, it has high uranium recovery rate and adsorption capacity, and can meet the needs of industrial production.

Description

Preparation method of biomass-derived N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode

technical field

The invention relates to the technical field of preparation of functional materials, in particular to a preparation method of a biomass source N and P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode.

Background technique

Due to the scarcity of uranium resources in my country, and the low grade of terrestrial uranium ores, most of which are depleted uranium ores, it is difficult to meet my country's future nuclear fuel supply needs. Efficient separation of uranium from uranium-containing waste liquid can not only effectively recover uranium resources, but also help reduce environmental pollution. The separation and enrichment of low-concentration uranium by traditional separation methods such as solvent extraction and membrane separation has poor technical and economic feasibility; while electro-adsorption is an effective method for uranium separation from uranium-containing wastewater, with low energy consumption and low pollution. , cost-effective advantages. The adsorption capacity of conventional adsorbents for U(VI) is mostly in the tens of mg/g, and the U(VI) adsorption capacity can be doubled by using electrosorption; Desorption, thereby avoiding the use of a large amount of acidic desorption solution; the use of electrosorption can also remove anions (such as NO ₃ -) in the solution while separating U(VI), and capture both in the counter electrode porous medium at the same time, This is also superior to conventional adsorbents.

The key to the separation of uranium in wastewater by electrosorption is the development of new and efficient electrode materials. Carbon materials have good corrosion resistance and stability, and are commonly used electrode materials for electrosorption. Carbon aerogels have the advantages of well-developed pore structure, good chemical stability, high specific surface area, and large adsorption capacity, so they are good electrode materials for electrosorption. Using chemicals such as polyols and acids as raw materials to prepare carbon aerogels, but the production cost is high; the template-oriented method can also be used to prepare carbon aerogels, but the process is complicated and depends on the fine structure and size of the template, making it difficult to mass-produce . Therefore, how to prepare high-performance electrode materials at low cost is the key to the separation of uranium from uranium-containing wastewater by electrosorption.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is to provide a preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, so as to solve the above-mentioned problems in the background technology.

The technical problem solved by the present invention adopts the following technical solutions to realize:

The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, the specific steps are as follows:

(1) Preparation of biomass-derived N and P co-doped carbon aerogels

Remove the outer epidermis of the waste biomass (grapefruit peel, sugarcane hawthorn, etc.), cut it into a suitable size, wash it, and then fully absorb the washed biomass, and then mix it with deionized water and N and P as a co-doping source. Add them to a hydrothermal kettle, and conduct a hydrothermal reaction at a temperature of 250 °C to obtain a pre-carbonized N, P co-doped carbon hydrogel, and further remove the solubility in the pre-carbonized N, P co-doped carbon hydrogel impurities;

Finally, the pre-carbonized N and P co-doped carbon hydrogel with the soluble impurities removed was cut into small squares, freeze-dried at -60 °C to form it, and then carbonized by introducing protective gas at 700 °C for 4 h to obtain N , P co-doped carbon aerogel;

(2) Preparation of N, P co-doped carbon aerogel/chitosan composite membrane electrode

Add a quantitative amount of chitosan to acetic acid, stir until completely dissolved to obtain a chitosan solution, and then add the N, P co-doped carbon aerogel obtained in step (1) to the chitosan solution according to the mass ratio to mix, And add a quantitative cross-linking agent and conductive carbon black, fully stir to obtain a viscous mixture, and finally spread the viscous mixture evenly on the titanium dioxide plate, and dry it at 120 ℃ to obtain biomass sources N and P. Co-doped carbon aerogel/crosslinked chitosan composite membrane electrode.

In the present invention, in step (1), the N, P co-doping source is aminomethylphosphonic acid.

In the present invention, in step (1), 30 g of biomass, 80 ml of deionized water and 3 g of N and P co-doping sources are added to the hydrothermal kettle.

In the present invention, in step (1), the hydrothermal reaction is 14-18 h.

In the present invention, in step (1), the process of removing the soluble impurities in the pre-carbonized N, P co-doped carbon hydrogel is as follows: soaking the pre-carbonized N, P co-doped carbon hydrogel in water and ethanol in the mixture for several days.

In the present invention, in step (2), the acetic acid concentration is 1 wt%.

In the present invention, in step (2), the mass ratio of the chitosan and the N, P co-doped carbon aerogel is 1:0.1-0.3.

In the present invention, in step (2), the optimal mass ratio of the chitosan and N, P co-doped carbon aerogel is 1:0.2.

In the present invention, in step (2), the conductive carbon black is 1.0 g.

In the present invention, in step (2), the crosslinking agent is epichlorohydrin, and the amount of epichlorohydrin is 1.5 mL.

In the present invention, in step (2), the protective gas is N ₂ .

Beneficial effects:

(1) The present invention uses agricultural processing wastes such as pomelo peels, bagasse and other cheap natural biomasses that have natural plant fiber sponge structures as raw materials to prepare N and P co-doped carbon aerogels with developed pore structures, and further utilizes N, P co-doped carbon aerogel and chitosan were composited to prepare N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, which was used for the electrosorption separation of uranium in uranium-containing wastewater. This reduces production costs and improves material properties;

(2) In the preparation of bio-carbon aerogel, aminomethylphosphonic acid is used as co-doping N and P source, and hybrid N and P atoms are introduced into the carbon aerogel, which has the hybridization of lone pair electrons. N and P atoms can be used as Lewis bases to effectively complex uranyl ions, thereby improving the adsorption capacity of uranium separation by electrosorption;

(3) The present invention utilizes N, P co-doped biomass carbon aerogel and chitosan composite to make N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, chitosan can be Improve the hydrophilicity of carbon aerogel and introduce new adsorption sites, which is beneficial to improve the effect of electro-adsorption separation of uranium;

(4) The biomass source N, P co-doped carbon aerogel/chitosan composite membrane electrode prepared by the present invention has high specific surface area, good electrical conductivity and chemical stability, and is used for electrosorption separation of uranium-containing wastewater It has high uranium recovery rate and adsorption capacity, and can meet the needs of industrial production.

Description of drawings

FIG. 1 is a schematic diagram of the preparation process of the preferred embodiment of the present invention.

Detailed ways

In order to make the technical means, creative features, achievement goals and effects realized by the present invention easy to understand and clearly, the present invention will be further described below with reference to specific embodiments.

Example 1 (implemented according to the mass ratio of chitosan and N, P co-doped carbon aerogel as 1:0.1)

The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, the specific steps are as follows:

(1) Preparation of biomass-derived N and P co-doped carbon aerogels

Remove the outer epidermis of the discarded biomass (citron peel, bagasse), cut it into a suitable size, wash it, and then fully absorb 30g of biomass, then mix it with 80ml of deionized water, 3g of aminomethylphosphonic acid (N, P co-doping source) was added to the hydrothermal kettle, and the hydrothermal reaction was carried out at a temperature of 250 ° C for 16 h to obtain a pre-carbonized N and P co-doped carbon hydrogel, and then the pre-carbonized N and P co-doped carbon hydrogel was obtained. The carbon hydrogel was soaked in a mixture of water and ethanol for several days to remove soluble impurities in the pre-carbonized N, P co-doped carbon hydrogel;

Finally, the pre-carbonized N, P co-doped carbon hydrogel with the soluble impurities removed was cut into small squares, freeze-dried at -60 °C to form it, and then carbonized by introducing _N2 protective gas at 700 °C for 4 h. N, P co-doped carbon aerogels were obtained;

(2) Preparation of N, P co-doped carbon aerogel/chitosan composite membrane electrode

Add 10.0g of chitosan to 1wt% acetic acid, stir until completely dissolved to obtain a chitosan solution, and then add 1.0g of N, P co-doped carbon aerogel obtained in step (1) to the chitosan solution and mix , and add 1.5 mL of epichlorohydrin cross-linking agent and 1.0 g of conductive carbon black, fully stir to obtain a viscous mixture, and finally spread the viscous mixture evenly on the titanium dioxide plate, at a temperature of 120 ℃ Dry to make biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode (membrane thickness is controlled by graded coating);

The electrosorption device includes an electrosorption cell, a pH meter, a conductivity meter and a DC power supply. The working electrode is a N, P co-doped carbon aerogel/chitosan composite membrane electrode (10×10mm membrane) bonded to a titanium dioxide plate. The N, P co-doped carbon aerogel/chitosan composite membrane electrode prepared above was used as the working electrode, the conductive carbon membrane of the same size was used as the counter electrode, the potential of the working electrode was controlled to -0.9V, and the uranium tailings wastewater (U (VI) concentration of 7.5mg/L) as water sample, controlled feed flow rate of 1L/h, continuous electrosorption for 50h, the results showed that the U(VI) extraction rate was 78%, and the uranium adsorption capacity was 292.5mg/g.

Example 2 (implemented according to the mass ratio of chitosan and N, P co-doped carbon aerogel as 1:0.2)

The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, the specific steps are as follows:

(1) Preparation of biomass-derived N and P co-doped carbon aerogels

Remove the outer epidermis of the discarded biomass (citron peel, bagasse), cut it into a suitable size, wash it, and then fully absorb 30g of biomass, then mix it with 80ml of deionized water, 3g of aminomethylphosphonic acid (N, P co-doping source) was added to the hydrothermal kettle, and the hydrothermal reaction was carried out at a temperature of 250 ° C for 16 h to obtain a pre-carbonized N and P co-doped carbon hydrogel, and then the pre-carbonized N and P co-doped carbon hydrogel was obtained. The carbon hydrogel was soaked in a mixture of water and ethanol for several days to remove soluble impurities in the pre-carbonized N, P co-doped carbon hydrogel;

Finally, the pre-carbonized N, P co-doped carbon hydrogel with the soluble impurities removed was cut into small squares, freeze-dried at -60 °C to form it, and then carbonized by introducing _N2 protective gas at 700 °C for 4 h. N, P co-doped carbon aerogels were obtained;

(2) Preparation of N, P co-doped carbon aerogel/chitosan composite membrane electrode

Add 10.0g of chitosan to 1wt% acetic acid, stir until completely dissolved to obtain a chitosan solution, and then add 2.0g of N, P co-doped carbon aerogel obtained in step (1) to the chitosan solution and mix , and add 1.5mL epichlorohydrin cross-linking agent and 1.0g conductive carbon black, fully stir to obtain a viscous mixture, and finally spread the viscous mixture evenly on the titanium dioxide plate, and dry at 120 ℃ Biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode (membrane thickness is controlled by graded coating);

The electrosorption device includes an electrosorption cell, a pH meter, a conductivity meter and a DC power supply. The working electrode is a N, P co-doped carbon aerogel/chitosan composite membrane electrode (10×10mm membrane) bonded to a titanium dioxide plate. The N, P co-doped carbon aerogel/chitosan composite membrane electrode prepared above was used as the working electrode, and the conductive carbon membrane of the same size was used as the counter electrode. The tailings wastewater (U(VI) concentration 7.5mg/L) was taken as the water sample, the feed flow rate was controlled to 1L/h, and the continuous electrosorption was performed for 50h. The results showed that the U(VI) extraction rate was 98%, and the uranium adsorption capacity reached 367.5mg /g.

Example 3 (implemented according to the mass ratio of chitosan and N, P co-doped carbon aerogel as 1:0.3)

The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, the specific steps are as follows:

(1) Preparation of biomass-derived N and P co-doped carbon aerogels

Remove the outer epidermis of the discarded biomass (citron peel, bagasse), cut it into a suitable size, wash it, and then fully absorb 30g of biomass, then mix it with 80ml of deionized water, 3g of aminomethylphosphonic acid (N, P co-doping source) was added to the hydrothermal kettle, and the hydrothermal reaction was carried out at a temperature of 250 ° C for 16 h to obtain a pre-carbonized N and P co-doped carbon hydrogel, and then the pre-carbonized N and P co-doped carbon hydrogel was obtained. The carbon hydrogel was soaked in a mixture of water and ethanol for several days to remove soluble impurities in the pre-carbonized N, P co-doped carbon hydrogel;

Finally, the pre-carbonized N, P co-doped carbon hydrogel with the soluble impurities removed was cut into small squares, freeze-dried at -60 °C to form it, and then carbonized by introducing _N2 protective gas at 700 °C for 4 h. N, P co-doped carbon aerogels were obtained;

(2) Preparation of N, P co-doped carbon aerogel/chitosan composite membrane electrode

Add 10.0 g of chitosan to 1wt% acetic acid, stir until completely dissolved to obtain a chitosan solution, and then add 3.0 g of N, P co-doped carbon aerogel obtained in step (1) to the chitosan solution and mix , and add 1.5mL epichlorohydrin cross-linking agent and 1.0g conductive carbon black, fully stir to obtain a viscous mixture, and finally spread the viscous mixture evenly on the titanium dioxide plate, and dry at 120 ℃ Biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode (membrane thickness is controlled by graded coating);

The electrosorption device includes an electrosorption cell, a pH meter, a conductivity meter and a DC power supply. The working electrode is a N, P co-doped carbon aerogel/chitosan composite membrane electrode (10×10mm membrane) bonded to a titanium dioxide plate. The N, P co-doped carbon aerogel/chitosan composite membrane electrode prepared above was used as the working electrode, and the conductive carbon membrane of the same size was used as the counter electrode. The tailings wastewater (U(VI) concentration 7.5mg/L) was taken as the water sample, the feed flow rate was controlled to 1L/h, and the continuous electrosorption was performed for 50h. The results showed that the U(VI) extraction rate was 84%, and the uranium adsorption capacity reached 315mg/L. g.

According to the test results of the N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrodes prepared in Examples 1 to 3 for the electro-adsorption separation of uranium in wastewater, it can be known that: chitosan is co-doped with N and P. When the mass ratio of heterocarbon aerogel is 1:0.2, the prepared N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode has the best separation effect of uranium in wastewater; When preparing the heterocarbon aerogel/cross-linked chitosan composite membrane electrode, appropriately increasing the amount of chitosan is beneficial to improve the effect of electro-adsorption separation of uranium (for example, compared with Example 2 and Example 3, the effect of Example 2 is better), Because chitosan can improve the hydrophilicity of carbon aerogels and introduce amino adsorption sites; but if the amount of chitosan is too high, it will block the pores of carbon materials, which is not conducive to the adsorption of uranium into the pores, thus affecting the electrosorption. The performance of separating uranium makes the uranium adsorption capacity decrease instead (for example, comparing Example 1 with Example 2, the effect of Example 1 becomes worse).

Claims (10)

1. the preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode, is characterized in that, concrete steps are as follows: (1) Preparation of biomass-derived N and P co-doped carbon aerogels Remove the outer skin of the waste biomass, cut it into a suitable size and wash it, and then fully absorb the washed biomass, and then add it to the hydrothermal kettle together with deionized water and N and P co-doping sources. , performing a hydrothermal reaction at a temperature of 250 °C to obtain a pre-carbonized N, P co-doped carbon hydrogel, and further remove the soluble impurities in the pre-carbonized N, P co-doped carbon hydrogel; Finally, the pre-carbonized N and P co-doped carbon hydrogel with the soluble impurities removed was cut into small squares, freeze-dried at -60 °C to form it, and then carbonized by introducing protective gas at 700 °C for 4 h to obtain N , P co-doped carbon aerogel; (2) Preparation of N, P co-doped carbon aerogel/chitosan composite membrane electrode Add a quantitative amount of chitosan to acetic acid, stir until completely dissolved to obtain a chitosan solution, and then add the N, P co-doped carbon aerogel obtained in step (1) to the chitosan solution according to the mass ratio and mix , and add a certain amount of cross-linking agent and conductive carbon black, fully stir to obtain a viscous mixture, and finally spread the viscous mixture evenly on the titanium dioxide plate, and dry it at 120 ℃ to obtain biomass source N, P co-doped carbon aerogel/crosslinked chitosan composite membrane electrode. 2 . The preparation method of biomass source N and P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1 , wherein in step (1), the N and P The co-doping source was aminomethylphosphonic acid. 3. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, characterized in that, in step (1), the hydrothermal kettle 30g of biomass, 80ml of deionized water and 3g of N, P co-doping sources were added to the medium. 4. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, characterized in that, in step (1), the removal of pre-carbonization The process of soluble impurities in the N, P co-doped carbon hydrogel is as follows: the pre-carbonized N, P co-doped carbon hydrogel is soaked in a mixture of water and ethanol for several days. 5. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, wherein in step (2), the acetic acid concentration is 1 wt%. 6. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, wherein in step (2), the chitosan The mass ratio of co-doped carbon aerogel with N and P is 1:0.1-0.3. 7. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 6, wherein in step (2), the chitosan The optimal mass ratio of co-doped carbon aerogel with N and P is 1:0.2. 8. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, wherein in step (2), the conductive carbon black is 1.0g. 9 . The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, wherein in step (2), the cross-linking agent For epichlorohydrin, the epichlorohydrin was 1.5 mL. 10. The preparation method of biomass source N, P co-doped carbon aerogel/cross-linked chitosan composite membrane electrode according to claim 1, wherein in step (2), the protective gas is N ₂ .

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