Composite carbon aerogel material and preparation method and application thereof

Abstract

The present application belongs to the technical field of adsorbing material, and particularly relates to a composite carbon aerogel material, a preparation method and application thereof. The composite carbon aerogel material comprises a carbon aerogel matrix and magnesium oxide loaded on the surface and pore structure of the carbon aerogel matrix. The composite carbon aerogel material has a pore structure, a pore diameter of 13.7-19.2 nm, a pore volume of 0.307-0.396 cm 3 / g, and a specific surface area of 47.8-71.6 m 2 / g. The pore structure of the composite carbon aerogel material enhances the diffusion capacity of wastewater, thereby improving the adsorption rate of phosphate. The magnesium oxide is uniformly dispersed on the surface and pore structure of the carbon aerogel, and can efficiently adsorb phosphate in wastewater. The adsorption capacity of the composite carbon aerogel material for phosphorus in wastewater is 364.2-392.5 mg / g, and the removal rate can reach 99.9% within 15 min.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adsorption materials, and particularly relates to a composite carbon aerogel material and a preparation method and application thereof. BACKGROUND

[0002] Phosphorus is one of the basic substances involved in the biochemical cycle of the earth and is an essential nutrient element for the growth of most plants, and plays an extremely important role in industry and agriculture; however, in the actual application process, the effective treatment of phosphorus-containing water bodies has become a big problem, and some are even discharged into lakes and rivers without treatment, stimulating the growth of algae, causing eutrophication and producing algal blooms, which seriously endanger the water body ecosystem. In order to prevent water eutrophication, it is necessary to treat the phosphates in the water body. At present, the methods for removing phosphorus from phosphorus-containing wastewater generally include chemical precipitation, biological method, membrane separation and adsorption method. Compared with other phosphorus removal technologies, the adsorption method has the advantages of simplicity, non-toxicity, low cost of adsorbent, high efficiency, etc., and is widely used in the recovery of low-concentration phosphorus solution and large-scale wastewater treatment. Traditional phosphorus removal adsorbents mainly include metal oxides / hydroxides, activated carbon, natural minerals, etc. These traditional adsorbents have the problems of poor adsorption capacity and slow adsorption rate. SUMMARY

[0003] Therefore, the present application provides a composite carbon aerogel material and a preparation method and application thereof. The composite carbon aerogel material provided by the present application has high adsorption rate and adsorption capacity for phosphates in wastewater, and can efficiently remove phosphates in wastewater.

[0004] In order to solve the above technical problems, the present application provides a composite carbon aerogel material, which comprises a carbon aerogel matrix and magnesium oxide loaded on the surface and pore structure of the carbon aerogel matrix.

[0005] The pore size of the composite carbon aerogel material is 13.7-19.2 nm, the specific surface area of the composite carbon aerogel material is 47.8-71.6 m 2 / g, and the pore volume of the composite carbon aerogel material is 0.307-0.396 cm 3 / g.

[0006] Preferably, the mass percentage of magnesium oxide in the composite carbon aerogel material is 10-90%.

[0007] The present application also provides a preparation method of the composite carbon aerogel material described in the above technical solution, which comprises the following steps:

[0008] subjecting biomass raw materials to hydrothermal carbonization to obtain a hydrogel of biochar;

[0009] subjecting the hydrogel of biochar to vacuum freeze-drying to obtain a carbon aerogel.

[0010] After the carbon aerogel is immersed in the impregnation solution, the carbon aerogel is calcined to obtain the composite carbon aerogel material; the impregnation solution is a mixed solution of a soluble magnesium salt, urea and ethanol.

[0011] Preferably, the soluble magnesium salt comprises magnesium nitrate or magnesium acetate.

[0012] The molar concentration of the soluble magnesium salt in the impregnation solution is 1-1.8 mol / L.

[0013] The molar concentration of urea in the impregnation solution is 0.05-0.25 mol / L.

[0014] Preferably, the mass and volume ratio of the carbon aerogel to the impregnation solution is 1g:8-12 mL.

[0015] Preferably, the temperature of the impregnation is 15-30℃; and the time of the impregnation is 12-16 h.

[0016] Preferably, the biomass raw material comprises fruit peel.

[0017] The temperature of the hydrothermal carbonization is 170-190℃, and the time of the hydrothermal carbonization is 10-14 h.

[0018] Preferably, the vacuum degree of the vacuum freeze drying is 5-15 Pa; the temperature of the vacuum freeze drying is -60--40℃; and the time of the vacuum freeze drying is 24-72 h.

[0019] Preferably, the temperature of the calcination is 300-600℃, the temperature rising rate for rising to the temperature required for the calcination is 1-6℃ / min; and the holding time of the calcination is 1.5-2.5 h.

[0020] The application further provides an application of the composite carbon aerogel material in the above technical solution or the composite carbon aerogel material prepared by the preparation method in the above technical solution as a phosphorus removal adsorbent.

[0021] The application provides a composite carbon aerogel material, which comprises a carbon aerogel matrix and magnesium oxide loaded on the surface and pore structure of the carbon aerogel matrix; the composite carbon aerogel material has a pore structure, the pore diameter of the composite carbon aerogel material is 13.7-19.2 nm, the specific surface area of the composite carbon aerogel material is 47.8-71.6 m 2 / g, and the pore volume of the composite carbon aerogel material is 0.307-0.396 cm 3 / g. In the present application, the composite carbon aerogel material has abundant pore structure, which enhances the diffusion capacity between phosphate ions and the material, thereby improving the adsorption rate of phosphate; the magnesium oxide is uniformly dispersed on the surface and pore structure of the carbon aerogel, which can efficiently adsorb the phosphate in wastewater, and the magnesium oxide in the carbon aerogel combines with the entering phosphate ions to form a precipitate. According to the results of the examples, the adsorption capacity of the composite carbon aerogel material provided by the present application for phosphorus in wastewater is 364.2-392.5 mg / g, and the removal rate of 99.9% can be reached within 15 min. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD pattern of the composite carbon aerogel material prepared in Examples 1-2;

[0023] Figure 2 Scanning electron microscope pattern of the composite carbon aerogel material prepared in Example 1;

[0024] Figure 3 Transmission electron microscope pattern of the composite carbon aerogel material prepared in Example 1;

[0025] Figure 4 Columnar comparison chart of the phosphate adsorption capacity of the adsorption materials prepared in Examples 1-2 and Comparative Examples 1-3;

[0026] Figure 5 Dot-line chart of the adsorption capacity of the adsorption materials prepared in Example 1 and Comparative Example 3 at different adsorption times;

[0027] Figure 6 Dot-line chart of the phosphorus removal rate of the composite carbon aerogel material prepared in Example 1 at different adsorption times. DETAILED DESCRIPTION

[0028] The present application provides a composite carbon aerogel material, which comprises a carbon aerogel matrix and magnesium oxide loaded on the surface and pore structure of the carbon aerogel matrix;

[0029] The pore diameter of the composite carbon aerogel material is 13.7-19.2 nm, and can be 18.5-19.2 nm; the specific surface area of the composite carbon aerogel material is 47.8-71.6 m 2 / g, and can be 47.8-62.5 m 2 / g; the pore volume of the composite carbon aerogel material is 0.307-0.396 cm 3 / g. In the present application, the composite carbon aerogel material has a three-dimensional porous network structure.

[0030] As a specific embodiment of the present application, the mass percentage of magnesium oxide in the composite carbon aerogel material can be 10-90%, can also be 20-80%, and can further be 40-60%.

[0031] The present application also provides a preparation method of the composite carbon aerogel material according to the above technical solution, comprising the following steps:

[0032] The biomass raw material is subjected to hydrothermal carbonization to obtain a hydrogel of biochar;

[0033] The hydrogel of biochar is subjected to vacuum freeze-drying to obtain a carbon aerogel;

[0034] The carbon aerogel is immersed in an impregnation liquid and then calcined to obtain the composite carbon aerogel material; the impregnation liquid is a mixed solution of soluble magnesium salt, urea and ethanol.

[0035] The present application obtains a hydrogel of biochar by hydrothermal carbonization of a biomass raw material. As a specific embodiment of the present application, the biomass raw material can include fruit peels, which can be watermelon peels, grapefruit peels or cantaloupe peels. As a specific embodiment of the present application, the hydrothermal carbonization preferably further comprises cleaning the biomass raw material before the hydrothermal carbonization. The present application removes sludge and other impurities attached to the surface of the biomass raw material through cleaning.

[0036] As a specific embodiment of the present application, the temperature of the hydrothermal carbonization can be 170-190℃, and can also be 175-180℃; the time of the hydrothermal carbonization can be 10-14h, and can also be 12-13h. As a specific embodiment of the present application, the hydrothermal carbonization can be carried out in a polytetrafluoroethylene reaction kettle.

[0037] As a specific embodiment of the present application, the hydrothermal carbonization can further comprise soaking the system after the hydrothermal carbonization in an ethanol aqueous solution to remove impurities. As a specific embodiment of the present application, the volume concentration of the ethanol aqueous solution can be 40-80%, and can also be 50-60%. The present application removes organic impurities such as sugars generated in the hydrothermal carbonization process through soaking. The present application does not have special requirements for the amount of the ethanol aqueous solution, the soaking time and the soaking times, as long as the impurities in the system after the hydrothermal carbonization can be removed. As a specific embodiment of the present application, the soaking can further comprise subjecting the soaked system to solid-liquid separation to obtain a hydrogel of biochar. As a specific embodiment of the present application, the solid-liquid separation can be filtration, and the present application does not have special requirements for the filtration, which can be performed in a conventional manner in the art.

[0038] After obtaining the biochar hydrogel, the biochar hydrogel is vacuum freeze-dried to obtain carbon aerogel. As an embodiment of the present application, the vacuum degree of the vacuum freeze-drying can be 5-15 Pa, and can also be 5-10 Pa; the temperature of the vacuum freeze-drying can be -60 to -40℃, and can also be -45 to -55℃; the time of the vacuum freeze-drying can be 24-72 h, and can also be 36-48 h. The vacuum freeze-drying method used in the present application can avoid the collapse of the carbon aerogel structure. In the present application, the carbon aerogel is brown.

[0039] After obtaining the carbon aerogel, the carbon aerogel is immersed in an impregnation liquid and then calcined to obtain the composite carbon aerogel material. In the present application, the impregnation liquid is a mixed solution of soluble magnesium salt, urea and ethanol. As an embodiment of the present application, the soluble magnesium salt can include magnesium nitrate or magnesium acetate, and the magnesium nitrate can be magnesium nitrate hexahydrate; the molar concentration of the soluble magnesium salt in the impregnation liquid can be 1-1.8 mol / L, and can also be 1.2-1.6 mol / L, and can further be 1.4-1.5 mol / L; the molar concentration of urea in the impregnation liquid can be 0.05-0.25 mol / L, and can also be 0.1-0.2 mol / L; the mass and volume ratio of the carbon aerogel to the impregnation liquid can be 1 g:8-12 mL, and can also be 1 g:9-10 mL. In the present application, ethanol is used as a solvent for urea and soluble magnesium salt, which can be more quickly absorbed by the carbon aerogel. The addition of urea in the impregnation liquid in the present application can form a pore structure during calcination, which is beneficial to the rapid entry of phosphate ions into the composite carbon aerogel material, and accelerates the adsorption rate. The soluble magnesium salt can be converted into magnesium oxide during calcination, forming a porous structure on the carbon aerogel. By adjusting the amount of urea, the size of the pore structure in the composite carbon aerogel material can be adjusted.

[0040] As an embodiment of the present application, the temperature of the impregnation can be 15-30℃, and can also be 20-25℃; the time of the impregnation can be 12-16 h, and can also be 13-15 h.

[0041] As an embodiment of the present application, the impregnation can further include: volatilizing the solvent in the system after impregnation, and calcining the solid obtained after volatilization of the solvent. The present application does not have special requirements for the volatilization of the solvent, and the conventional volatilization method in the art can be used, such as natural volatilization.

[0042] As a specific embodiment of the present application, the calcination temperature can be 300-600℃, and can be specifically 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃; the temperature rising rate for rising to the temperature required for calcination can be 1-6℃ / min, and can be specifically 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or 6℃ / min; the holding time for the calcination can be 1.5-2.5h, and can be specifically 1.5h, 1.8h, 2h, 2.3h or 2.5h. As a specific embodiment of the present application, the calcination can be carried out under a protective atmosphere, and the protective atmosphere can be a nitrogen atmosphere or an argon atmosphere.

[0043] The present application uses waste biomass as a raw material to prepare carbon aerogel, and forms a porous phosphorus removal adsorbent material through co-pyrolysis of magnesium salt, urea and carbon aerogel. The preparation method provided by the present application uses materials that are abundant in source and cheap and easy to obtain, and the synthesis method is simple and green; the composite carbon aerogel material prepared has an extremely fast phosphorus removal rate. The composite carbon aerogel material prepared by the present application has a good application prospect in water purification.

[0044] The present application also provides the use of the composite carbon aerogel material in the above technical solution or the composite carbon aerogel material prepared by the preparation method in the above technical solution as a phosphorus removal adsorbent. As a specific embodiment of the present application, a method for removing phosphorus from wastewater by using the composite carbon aerogel material as a phosphorus removal adsorbent can include the following steps:

[0045] The composite carbon aerogel material is placed in phosphorus-containing wastewater for adsorption and phosphorus removal.

[0046] As a specific embodiment of the present application, the concentration of phosphorus in the phosphorus-containing wastewater can be 1-50mg / L, and can also be 5-30mg / L; the mass of the composite carbon aerogel material to the volume of the phosphorus-containing wastewater can be 100-500mg:1L, and can also be 200-400mg:1L; the time for adsorption and phosphorus removal can be 3-24h, and can also be 10-12h.

[0047] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0048] Example 1

[0049] After the surface of the waste watermelon peel is cleaned, it is placed in a polytetrafluoroethylene reaction kettle, and after hydrothermal carbonization at 180℃ for 12h, it is immersed in an ethanol aqueous solution with a volume concentration of 50% to remove impurities, and after filtration, a biochar hydrogel is obtained;

[0050] The biochar hydrogel is vacuum freeze-dried under the condition of 10 Pa vacuum degree and -50 DEG C temperature for 48 h to obtain a carbon aerogel material;

[0051] 1 g of the carbon aerogel material is immersed in 10 mL of a mixed solution of magnesium nitrate hexahydrate, urea and ethanol (the molar concentration of magnesium nitrate is 1.4 mol / L and the molar concentration of urea is 0.1 mol / L) at 25 DEG C for 12 h, and then the solution is naturally volatilized; the solid obtained after volatilization of the solution is heated to 450 DEG C at a heating rate of 2 DEG C / min in a tube furnace under a nitrogen atmosphere and calcined for 2 h to obtain a composite carbon aerogel material.

[0052] Example 2

[0053] The composite carbon aerogel material is prepared according to the method of Example 1, except that the molar concentration of urea in the mixed solution of magnesium nitrate hexahydrate, urea and ethanol is adjusted to 0.2 mol / L.

[0054] Comparative Example 1

[0055] 1.4 mol of magnesium nitrate hexahydrate and 0.1 mol of urea are mixed and heated to 450 DEG C at a heating rate of 2 DEG C / min in a tube furnace under a nitrogen atmosphere and calcined for 2 h to obtain an adsorption material without carbon aerogel.

[0056] Comparative Example 2

[0057] The adsorption material is prepared according to the method of Example 1, except that the mixed solution of magnesium nitrate hexahydrate, urea and ethanol is replaced by an ethanol solution of urea with a molar concentration of 0.1 mol / L to obtain an adsorption material without magnesium element.

[0058] Comparative Example 3

[0059] The adsorption material is prepared according to the method of Example 1, except that the mixed solution of magnesium nitrate hexahydrate, urea and ethanol is replaced by an ethanol solution of magnesium nitrate with a molar concentration of 1.4 mol / L to obtain an adsorption material without urea.

[0060] The composite carbon aerogel material prepared in Examples 1 and 2 is subjected to X-ray diffraction detection to obtain an XRD spectrum as shown in Figure 1 It can be seen from Figure 1 that the composite carbon aerogel material provided by the application contains MgO.

[0061] The composite carbon aerogel material prepared in Example 1 is subjected to scanning electron microscope detection to obtain an SEM image as shown in Figure 2 The adsorption material prepared in Example 1 is subjected to transmission electron microscope detection to obtain a TEM image as shown in Figure 3 It can be seen fromFigure 2 , 3 It can be seen that the composite carbon aerogel material provided by the present invention has a three-dimensional porous network structure.

[0062] The adsorbent materials prepared in Examples 1-2 and Comparative Examples 1-3 were subjected to nitrogen physical adsorption-desorption detection, and the pore data are listed in Table 1.

[0063] Table 1 Pore data of different adsorbent materials

[0064] Example BET specific surface area (m 2 / g) Pore diameter (nm) Pore volume (cm 3 / g) Comparative Example 1 5.9 24.1 0.034 Comparative Example 2 86.4 21.0 0.071 Comparative Example 3 71.6 13.7 0.351 Example 1 62.5 18.5 0.396 Example 2 47.8 19.2 0.307

[0065] Five mg of the adsorbent materials prepared in Examples 1-2 and Comparative Examples 1-3 were placed in 100 mL beakers, and 50 mL of a phosphorus-containing aqueous solution (KH2PO4 solution) with a phosphorus concentration of 50 mg / L (based on the P content in KH2PO4) was added to each beaker. After mixing, the solutions were adsorbed for 12 h, and the concentration of P in the solution was measured. The adsorption capacity of the adsorbent materials for phosphorus (based on phosphorus content) was calculated. The results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the adsorption material provided by the present invention has excellent adsorption performance for phosphorus.

[0066] The adsorbent materials prepared in Example 1 and Comparative Example 3 were immersed in a KH2PO4 standard solution with a phosphorus concentration of 50 mg / L at a dosage of 0.1 g / L and adsorbed at room temperature (25 °C). Samples were taken for detection at the following adsorption times: 5 min, 10 min, 15 min, 25 min, 40 min, 55 min, 85 min, 115 min, 145 min, and 205 min. The phosphorus concentration was determined by molybdenum blue spectrophotometry (Chinese standard GB 11893-89). The test results (as P) are listed in Table 2.

[0067] Table 2 Adsorption capacity of adsorbent materials at different adsorption times

[0068]

[0069] Based on Table 2, plot the adsorption capacity of the adsorbent materials prepared in Example 1 and Comparative Example 3 at different adsorption times using dot-line graphs. Figure 5 As shown. (Combined with Table 2 and...) Figure 5 It can be seen that the adsorption material provided by the present invention has a rapid phosphorus removal rate.

[0070] The composite carbon aerogel material prepared in Example 1 was soaked in natural water body with P concentration of 3.3 mg / L at a dosage of 0.5 g / L at room temperature (25℃) for adsorption, and samples were taken at the following adsorption times: 1 min, 3 min, 5 min, 7 min, 10 min, 15 min, the concentration of phosphorus was determined by molybdenum blue spectrophotometry (Chinese standard GB 11893-89), and the test results (in terms of P) are shown in Table 3.

[0071] Table 3 Removal rate of phosphorus in natural water body by the composite carbon aerogel material prepared in Example 1

[0072] Adsorption time (min) 1 3 5 7 10 15 Removal rate (%) 83.1 94.8 96.5 97.3 98.3 99.9

[0073] According to Table 3, a point-line graph of the phosphorus removal rate of the composite carbon aerogel material prepared in Example 1 at different adsorption times was drawn, as shown in Figure 6

[0074] According to Table 3 and Figure 6 It can be seen that the composite carbon aerogel material provided by the present application has a rapid phosphorus removal rate and can achieve a removal rate of 99.9% within 15 min.

[0075] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.​

Claims

1. A composite carbon aerogel material, characterized in that, Includes a carbon aerogel matrix and magnesium oxide supported on the surface and in the pore structure of the carbon aerogel matrix; The composite carbon aerogel material has a pore size of 13.7–19.2 nm and a specific surface area of ​​47.8–71.6 m². 2 / g, the pore volume of the composite carbon aerogel material is 0.307~0.396cm. 3 / g; The preparation method of the composite carbon aerogel material includes the following steps: Biomass raw materials are subjected to hydrothermal carbonization to obtain biochar hydrogels; the biomass raw materials include fruit peels. The biochar hydrogel was subjected to vacuum freeze-drying to obtain carbon aerogel; The carbon aerogel is impregnated in an impregnation solution and then calcined to obtain the composite carbon aerogel material; the impregnation solution is a mixed solution of soluble magnesium salt, urea and ethanol; the molar concentration of soluble magnesium salt in the impregnation solution is 1 to 1.8 mol / L; the molar concentration of urea in the impregnation solution is 0.05 to 0.25 mol / L.

2. The composite carbon aerogel material according to claim 1, characterized in that, The composite carbon aerogel material contains 10-90% magnesium oxide by mass.

3. The method for preparing the composite carbon aerogel material according to claim 1 or 2, characterized in that, Includes the following steps: Biomass raw materials are subjected to hydrothermal carbonization to obtain biochar hydrogels; the biomass raw materials include fruit peels. The biochar hydrogel was subjected to vacuum freeze-drying to obtain carbon aerogel; The carbon aerogel is impregnated in an impregnation solution and then calcined to obtain the composite carbon aerogel material; the impregnation solution is a mixed solution of soluble magnesium salt, urea and ethanol; the molar concentration of soluble magnesium salt in the impregnation solution is 1 to 1.8 mol / L; the molar concentration of urea in the impregnation solution is 0.05 to 0.25 mol / L.

4. The preparation method according to claim 3, characterized in that, The soluble magnesium salts include magnesium nitrate or magnesium acetate.

5. The preparation method according to claim 3 or 4, characterized in that, The mass ratio of the carbon aerogel to the volume ratio of the impregnation solution is 1g:8-12mL.

6. The preparation method according to claim 3, characterized in that, The immersion temperature is 15–30°C; the immersion time is 12–16 hours.

7. The preparation method according to claim 3, characterized in that, The hydrothermal carbonization temperature is 170–190℃, and the time is 10–14 hours.

8. The preparation method according to claim 3, characterized in that, The vacuum degree of the vacuum freeze-drying is 5 to 15 Pa; the temperature of the vacuum freeze-drying is -60 to -40°C; and the time of the vacuum freeze-drying is 24 to 72 hours.

9. The preparation method according to claim 3, characterized in that, The calcination temperature is 300–600°C, and the heating rate to the required calcination temperature is 1–6°C / min; the holding time for calcination is 1.5–2.5 h.

10. The application of the composite carbon aerogel material according to claim 1 or 2 or the composite carbon aerogel material prepared by the preparation method according to any one of claims 3 to 9 as a phosphorus removal adsorbent.

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