A composite aerogel modified with an iron-polyphenol coating, its preparation method and application

Abstract

This invention relates to an iron-polyphenol-coated composite aerogel, its preparation method, and its application, belonging to the field of adsorbent preparation and application technology. The invention involves first immersing a porous aerogel in a polyphenol aqueous solution, then adding ferrous salt to the solution for liquid-phase deposition, washing with ultrapure water, crosslinking with glutaraldehyde aqueous solution, thoroughly washing with ethanol and ultrapure water, and finally drying to obtain an iron-polyphenol-coated composite aerogel. The raw materials used in this method are green and safe, the preparation process is simple, and it can be produced on a large scale. The resulting iron-polyphenol-coated composite aerogel exhibits high adsorption capacity, high selectivity, and high reduction rate for gold ions in aqueous solution, and also possesses excellent adsorption-desorption cycle stability, making it suitable for the efficient separation and recovery of gold from electronic wastewater.

Description

Technical Field

[0001] This invention belongs to the field of adsorbent preparation technology, specifically relating to an iron-polyphenol coating-modified composite aerogel, its preparation method, and its application. Background Technology

[0002] With the rapid development of science and technology, electronic products are iterating at an increasingly faster pace, resulting in a large number of electronic products being discarded each year, creating e-waste. Currently, the vast majority of e-waste can only be disposed of through simple landfill or incineration. On the one hand, this causes serious harm to the environment; on the other hand, due to the high gold content in e-waste, it loses much of its recyclability. Therefore, recovering gold from e-waste has significant environmental and economic benefits. In recent years, adsorption has become one of the most valuable methods for gold recovery due to its advantages such as being environmentally friendly, widely applicable, simple to operate, and easy to recycle.

[0003] The core of adsorption methods is the adsorbent. Generally, powdered adsorbents have a large specific surface area and numerous adsorption sites, exhibiting excellent gold ion recovery performance. However, the preparation process of most powdered adsorbent materials is cumbersome, the recovery process is difficult, and recovery losses are significant. In recent years, aerogel materials have emerged as a novel adsorbent material due to their highly open three-dimensional porous structure, low density, high porosity, and large specific surface area, which also provide numerous adsorption sites. Furthermore, aerogels are bulk materials, making them easier to recover than powdered adsorbents.

[0004] Polyphenols are widely found in plants and are a class of natural organic molecules with abundant phenolic hydroxyl groups. These hydroxyl groups can effectively adsorb gold ions and simultaneously donate electrons to reduce gold ions to elemental gold. Furthermore, the catechol structure in polyphenols exhibits abundant covalent / non-covalent interactions (including hydrogen bonds, coordination bonds, and π-π interactions) with the surface of the matrix material, enabling polyphenols to adhere to the surface of most materials. However, simply immersing the material in a polyphenol solution cannot effectively, uniformly, and stably allow polyphenols to adhere to the material surface; even after multiple immersion cycles, the number of polyphenol molecules effectively adhering to the material surface is very limited. Metal-polyphenol coatings are supramolecular cross-linked network structures obtained by co-deposition of metal ions and polyphenol ligands. By introducing metal ions and polyphenol co-deposition, a large amount of polyphenols can be rapidly deposited and adhered to the surface of aerogel materials in a short time, forming a composite aerogel modified with a metal-polyphenol coating. This effectively increases the phenolic hydroxyl content on the aerogel surface, providing more sites for the adsorption-reduction of gold ions and significantly improving the adsorption-reduction efficiency and selectivity of the composite aerogel for gold ions in solution. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an iron-polyphenol coating modified composite aerogel, its preparation method and application.

[0006] A method for preparing an iron-polyphenol coating-modified composite aerogel involves immersing a porous aerogel in a polyphenol aqueous solution, adding an aqueous solution of ferrous salt for liquid-phase deposition, washing with ultrapure water, crosslinking with glutaraldehyde aqueous solution, thoroughly washing with ethanol and ultrapure water, and finally drying thoroughly to obtain the aerogel.

[0007] Furthermore, the porous aerogel of the present invention is at least one of reduced graphene oxide / multi-walled carbon nanotube aerogel, reduced graphene oxide aerogel, sodium alginate aerogel, cellulose aerogel and polyimide aerogel.

[0008] Furthermore, the polyphenols of the present invention are one or more of tannic acid, gallic acid, pyrogallol, epigallocatechin gallate ester.

[0009] Furthermore, the ferrous salt of the present invention is one or more of ferrous chloride tetrahydrate, anhydrous ferrous chloride, ferrous sulfate, ferrous bromide, and ferrous sulfide.

[0010] Furthermore, the concentration of the polyphenol aqueous solution of the present invention is 8-80 mg / ml, the concentration of the ferrous salt aqueous solution is 0.98-19.2 mg / ml, and the concentration of the glutaraldehyde aqueous solution is 5-50 wt%.

[0011] Furthermore, the soaking time of the present invention is 1-30 minutes.

[0012] Furthermore, the co-deposition time of the present invention is 10-480 min, and the co-deposition temperature is 10-40℃.

[0013] Furthermore, the crosslinking time of the present invention is 1-24h, and the crosslinking temperature is 15-35℃.

[0014] Furthermore, the present invention has a drying time of 24-96 hours and a drying temperature of -20 to 0°C.

[0015] The iron-polyphenol coating-modified composite aerogel obtained by the preparation method of the present invention, and the application of the composite aerogel in the adsorption-reduction process of gold ions.

[0016] The beneficial effects of this invention are:

[0017] (1) The raw materials used in this invention are safe, green and easy to obtain, and the entire reaction process is carried out in an aqueous solution, which is in line with green chemistry.

[0018] (2) The composite aerogel modified with iron-polyphenol coating described in this invention has a large adsorption capacity, high reduction rate and strong selectivity for gold ions.

[0019] (3) The composite aerogel modified with iron-polyphenol coating of the present invention has stable adsorption performance, can be recycled, and can realize the recycling of precious metal resources while protecting the environment. Attached Figure Description

[0020] Figure 1 Photograph of the composite aerogel modified with iron-polyphenol coating;

[0021] Figure 2 Scanning electron microscope image of iron-polyphenol coating-modified composite aerogel;

[0022] Figure 3 Scanning electron microscope image of iron-polyphenol coated composite aerogel after adsorption-reduction of gold ions; Detailed Implementation

[0023] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that the specific embodiments described herein are for explaining the invention only and are not intended to limit the invention.

[0024] This invention provides a method for preparing an iron-polyphenol coating-modified composite aerogel, comprising: immersing a porous aerogel in a polyphenol aqueous solution, adding an aqueous solution of ferrous salt for co-deposition, washing with ultrapure water, crosslinking with glutaraldehyde aqueous solution, thoroughly washing with ethanol and ultrapure water, and finally drying thoroughly to obtain the aerogel.

[0025] The porous aerogel is one of reduced graphene oxide / multi-walled carbon nanotube aerogel, reduced graphene oxide aerogel, sodium alginate aerogel, cellulose aerogel, and polyimide aerogel, preferably reduced graphene oxide / multi-walled carbon nanotube aerogel. All porous aerogels are obtained by pre-vacuum drying.

[0026] The polyphenol is one or more of tannic acid, gallic acid, pyrogallol, and epigallocatechin gallate, with tannic acid being preferred. The polyphenol aqueous solution is obtained by dissolving the polyphenol in ultrapure water.

[0027] The ferrous salt is one or more of ferrous chloride tetrahydrate, anhydrous ferrous chloride, ferrous sulfate, ferrous bromide, and ferrous sulfide, preferably ferrous chloride tetrahydrate. The aqueous solution of the ferrous salt is obtained by dissolving the ferrous salt in ultrapure water. The aqueous solution of glutaraldehyde is obtained by dissolving glutaraldehyde in ultrapure water.

[0028] The concentration of the polyphenol aqueous solution is 8-80 mg / ml, preferably 40 mg / L.

[0029] The concentration of the ferrous salt aqueous solution is 0.98-19.2 mg / ml, preferably 9.8 mg / ml.

[0030] The concentration of the glutaraldehyde aqueous solution is 5-50 wt%, preferably 30 wt%.

[0031] The soaking time is 1-30 minutes, preferably 20 minutes.

[0032] The co-deposition time is 10-480 min, preferably 120 min; the co-deposition temperature is 10-40℃, preferably 25℃.

[0033] The crosslinking time is 1-24h, preferably 6h; the crosslinking temperature is 15-35℃, preferably 25℃.

[0034] The drying time is 24-96 hours, preferably 72 hours; the drying temperature is -20 to 0°C, preferably -8°C.

[0035] Figure 1 This is a composite aerogel modified with an iron-polyphenol coating obtained using the preparation method of the present invention. Figure 2 This is a scanning electron microscope image of the composite aerogel modified with an iron-polyphenol coating according to the present invention.

[0036] The iron-polyphenol coating-modified composite aerogel obtained by the preparation method of the present invention can be used for adsorption-reduction of gold ions. Figure 3 This is a scanning electron microscope image of gold ions after adsorption and reduction.

[0037] I. The iron-polyphenol coating-modified composite aerogel prepared in this invention is used for adsorption-reduction of gold ions. Adsorption capacity and reduction rate are the main parameters for evaluating adsorption and reduction performance.

[0038] The parameters were selected by using the prepared iron-polyphenol coated composite aerogel as the adsorbent in an aqueous solution containing only gold ions for adsorption experiments. The adsorption conditions were: adsorbent dosage 0.003 g, Au 3+ The concentration is 1200 mg / L, Au 3+ The solution volume was 10 ml, pH = 4, and the temperature was 25℃. After 48 h of adsorption, samples were taken, and the concentration of gold ions in the solution was determined by ICP-OES. The adsorption capacity and reduction rate of the composite aerogel for gold ions were calculated using the following formula:

[0039] The adsorption capacity is defined as follows:

[0040]

[0041] In the formula, q e (mg / g) represents the total adsorption capacity; C o (mg / L) and C e(mg / L) represents the initial and equilibrium concentrations of the gold ion solution; V(L) represents the volume of the gold ion solution; and m(g) represents the mass of the iron-polyphenol coating-modified composite aerogel.

[0042] The reduction rate is defined as:

[0043]

[0044] In the formula, γ(%) is the reduction rate; q γ (mg / g) is the adsorbed Au 3+ Au 3+ Restore to Au 0 The capacity (calculated from XPS peak splitting); q e (mg / g) is the adsorbed Au 3+ Total adsorption capacity.

[0045] Example 1

[0046] A method for preparing an iron-polyphenol coating-modified composite aerogel includes the following steps:

[0047] Step (1) Dissolve 1.2g of tannic acid in 30ml of ultrapure water to obtain a polyphenol aqueous solution with a concentration of 40mg / ml; dissolve 0.294g of ferrous chloride tetrahydrate in 30ml of ultrapure water to obtain a ferrous salt solution with a concentration of 9.8mg / ml. At this time, the molar ratio of tannic acid solution to ferrous chloride tetrahydrate solution is recorded as 1:2.

[0048] Step (2) Immerse the reduced graphene oxide / multi-walled carbon nanotube aerogel substrate in the above-mentioned polyphenol aqueous solution for 5 min.

[0049] Step (3) Transfer the ferrous salt aqueous solution from step (1) to the solution from step (2), and transfer the reaction vessel containing the two solutions into a water bath constant temperature shaker. Shake and deposit for 120 min at 25°C.

[0050] Step (4) Transfer the reaction vessel containing the above solution from the water bath constant temperature shaker into the oven and react at 45°C for 10 minutes. Then take out the polyphenol-iron composite aerogel and wash it with ultrapure water.

[0051] Step (5) Place the cleaned polyphenol-iron composite aerogel in 5 ml of 30 wt% glutaraldehyde solution for crosslinking for 6 h, wash thoroughly with ethanol and ultrapure water, and then dry thoroughly for 72 h to obtain the final iron-polyphenol coating modified composite aerogel.

[0052] Examples 2-5

[0053] Adjust the aerogel substrate in step (2) of Example 1 (as shown in Table 1), and keep the other conditions the same as in Example 1 to obtain the corresponding iron-polyphenol coating modified composite aerogel.

[0054] Test Example 1

[0055] The iron-polyphenol coating-modified composite aerogels prepared in Examples 1-5 were tested, and the results are shown in Table 1.

[0056] Table 1. Adsorption capacity and reduction rate of gold ions for the iron-polyphenol coated composite aerogels prepared in Examples 1-5

[0057]

[0058] As shown in Table 1, the composite aerogels modified with iron-polyphenol coatings prepared using different aerogel substrates all exhibit excellent adsorption capacity and reduction rate. Due to the strong electron-donating synergistic effect between reduced graphene oxide / multi-walled carbon nanotubes and the iron-polyphenol coating, the composite aerogel modified with iron-polyphenol coatings prepared using reduced graphene oxide / multi-walled carbon nanotube aerogel as the substrate exhibits the best performance.

[0059] Examples 6-10

[0060] Adjust the tannic acid concentration in step (1) of Example 1 (as shown in Table 2), and keep the other conditions the same as in Example 1 to obtain the corresponding iron-polyphenol coating modified composite aerogel.

[0061] Test Example 2

[0062] The iron-polyphenol coating-modified composite aerogels prepared in Examples 6-10 were tested, and the results are shown in Table 2.

[0063] Table 2 shows the adsorption capacity and reduction rate of gold ions for the iron-polyphenol coated composite aerogels prepared in Examples 6-10.

[0064]

[0065]

[0066] As shown in Table 2, the adsorption capacity of the iron-polyphenol coating-modified composite aerogels prepared with different tannic acid concentrations for gold ions exhibits a trend of first increasing and then decreasing. This is because when the tannic acid concentration is low, there are fewer functional groups on the composite aerogel that can effectively adsorb gold ions, resulting in a low adsorption capacity. Conversely, when the tannic acid concentration is high, the iron-polyphenol coating formed on the aerogel substrate is unstable and cannot adsorb a large number of gold ions. Furthermore, the reduction rate of gold ions for each composite aerogel remains at an excellent level.

[0067] Examples 11-15

[0068] Adjust the concentration of ferrous chloride tetrahydrate in step (1) of Example 1 (as shown in Table 3), and keep the other conditions the same as in Example 1 to obtain the corresponding iron-polyphenol coating modified composite aerogel.

[0069] Test Example 3

[0070] The iron-polyphenol coating-modified composite aerogels prepared in Examples 11-15 were tested, and the results are shown in Table 3.

[0071] Table 3. Adsorption capacity and reduction rate of gold ions for the iron-polyphenol coated composite aerogels prepared in Examples 11-15

[0072]

[0073] As shown in Table 3, when the concentration of tannic acid, which plays a key role in the adsorption and reduction of gold ions, is the same, the composite aerogels modified with iron-polyphenol coatings prepared with different concentrations of ferrous chloride tetrahydrate have little effect on the adsorption capacity and reduction rate of gold ions, and both the adsorption capacity and reduction rate remain at an excellent level.

[0074] Examples 16-21

[0075] Adjust the deposition time in step (3) of Example 1 (as shown in Table 4), and keep the other conditions the same as in Example 1 to obtain the corresponding iron-polyphenol coating modified composite aerogel.

[0076] Test Example 4

[0077] The iron-polyphenol coating-modified composite aerogels prepared in Examples 16-21 were tested, and the results are shown in Table 4.

[0078] Table 4. Adsorption capacity and reduction rate of gold ions for the iron-polyphenol coated composite aerogels prepared in Examples 16-21

[0079] Example Deposition time (min) Adsorption capacity (mg / g) Reduction rate (%) 1 120 2760 85 16 20 2208 81 17 40 2429 82 18 60 2511 82 19 240 2744 83 20 360 2749 85 21 480 2721 85

[0080] As shown in Table 4, the adsorption capacity of the composite aerogel for gold ions first increases with increasing deposition time, and then remains stable. This is because as deposition time increases, the amount of iron-polyphenol coating deposited on the aerogel substrate increases, thereby increasing the adsorption capacity for gold ions; after a certain time, the coating is completely deposited, and therefore the adsorption capacity for gold ions remains stable. Furthermore, the reduction rate of gold ions by each composite aerogel remains at an excellent level.

[0081] Examples 22-27

[0082] Adjust the deposition temperature in step (3) of Example 1 (as shown in Table 5), and keep the other conditions the same as in Example 1 to obtain the corresponding iron-polyphenol coating modified composite aerogel.

[0083] Test Example 5

[0084] The iron-polyphenol coating-modified composite aerogels prepared in Examples 22-27 were tested, and the results are shown in Table 5.

[0085] Table 5. Adsorption capacity and reduction rate of gold ions for the iron-polyphenol coated composite aerogels prepared in Examples 22-27

[0086]

[0087]

[0088] As shown in Table 5, the adsorption capacity of the composite aerogels for gold ions initially increases and then decreases with increasing deposition temperature. Initially, with higher deposition temperatures, iron-polyphenols are more easily assembled into a coating and deposited onto the aerogel substrate, thus increasing the adsorption capacity for gold ions. However, with further increases in deposition temperature, the high temperature destabilizes the iron-polyphenols, making them prone to detaching from the aerogel substrate, thereby decreasing the adsorption capacity for gold ions. Furthermore, the reduction rate of gold ions by each composite aerogel remains at an excellent level.

[0089] Examples 28-33

[0090] Adjust the crosslinking time in step (5) of Example 1 (as shown in Table 6), and keep the other conditions the same as in Example 1 to obtain the corresponding iron-polyphenol coating modified composite aerogel.

[0091] Test Example 6

[0092] The iron-polyphenol coating-modified composite aerogels prepared in Examples 28-33 were tested, and the results are shown in Table 6.

[0093] Table 6. Adsorption capacity and reduction rate of gold ions for the iron-polyphenol coated composite aerogels prepared in Examples 28-33

[0094] Example Crosslinking time (h) Adsorption capacity (mg / g) Reduction rate (%) 1 6 2760 85 28 2 2189 86 29 10 2729 85 30 16 2387 84 31 24 1966 83 32 36 1849 81 33 48 1987 84

[0095] As shown in Table 6, the adsorption capacity of the composite aerogels for gold ions initially increases and then decreases with prolonged cross-linking time. Initially, with extended cross-linking time, iron-polyphenols cross-link into a stable structure on the aerogel substrate, thus increasing the adsorption capacity for gold ions. However, with further extension of cross-linking time, the degree of cross-linking of iron-polyphenols increases, reducing the content of polyphenols that can effectively adsorb and reduce gold ions, thereby decreasing the adsorption capacity for gold ions. Furthermore, the reduction rate of gold ions by each composite aerogel remains at an excellent level.

[0096] II. The iron-polyphenol coating-modified composite aerogel prepared in this invention is used for highly selective adsorption-reduction of gold ions. The adsorption rate, reduction rate and selectivity coefficient are the main parameters for evaluating selectivity.

[0097] The parameters were selected by using the prepared iron-polyphenol coated composite aerogel as the adsorbent in an electronic waste water solution. The adsorption conditions were: adsorbent dosage 0.003 g, and the concentrations of various metal ions in the electronic waste water solution were: Au 3+ 12.7 mg / L, Pt 2+ 10.0 mg / L, Pd 2+ 8.4 mg / L, Cu 2+ 10.5 mg / L, Ca 2+ 9.6 mg / L, Mn 2+ 9.4 mg / L, Na + 10.5 mg / L, Mg 2+ 11.9 mg / L, Ni 2+ 9.3 mg / L, Co 2+ 8.6 mg / L, Zn 2+ 18.1 mg / L, Hg 2+ A 10 ml aqueous solution of 11.8 mg / L electronic waste was prepared at pH 1 and 25°C. After 24 hours of adsorption, a sample was taken, and the concentrations of each metal ion in the solution were determined by ICP-OES. The adsorption rate was calculated using the following formula:

[0098] The adsorption rate is defined as follows:

[0099]

[0100] In the formula, ρ (%) is the adsorption rate; C o (mg / L) and C e (mg / L) represents the initial and equilibrium concentrations of each metal ion in the electronic waste aqueous solution.

[0101] The reduction rate is defined by formula (2).

[0102] The selectivity coefficient is defined as follows:

[0103]

[0104] In the formula, θ (ml / g) is the selectivity coefficient; C o (mg / L) and C e (mg / L) represents the initial and equilibrium concentrations of each metal ion in the electronic wastewater solution; V (ml) represents the volume of the electronic wastewater solution; and m (g) represents the mass of the adsorbent.

[0105] Example 34

[0106] Iron-polyphenol-coated composite aerogels were prepared according to the method in Example 1.

[0107] Test Example 7

[0108] The selectivity of the iron-polyphenol coating-modified composite aerogel prepared in Example 34 was tested, and the results are shown in Table 7.

[0109] Table 7 shows the adsorption rate, reduction rate, and selectivity coefficient of various metal ions in electronic waste water for the iron-polyphenol coated composite aerogel prepared in Example 34.

[0110]

[0111] As shown in Table 7, the iron-polyphenol coated composite aerogel exhibits a high selectivity of 97.1% for gold ions in electronic wastewater solutions, a reduction rate of 100%, and virtually no adsorption or reduction of other competing metal ions; the selectivity factor for gold ions is as high as 1.27*10. 6 The selectivity for gold ions is much higher than that for other metal ions. Table 7 shows that the composite aerogel modified with iron-polyphenol coating has good selectivity for gold ions.

[0112] III. The iron-polyphenol coating-modified composite aerogel prepared in this invention is used for adsorption-desorption of gold ions. The adsorption rate and desorption rate are the main parameters for evaluating the stability of the adsorption-desorption cycle.

[0113] The parameters were selected by using the prepared iron-polyphenol coated composite aerogel as the adsorbent in an aqueous solution containing only gold ions for adsorption experiments. The adsorption conditions were: adsorbent dosage 0.01 g, Au 3+ The concentration is 100 mg / L, Au 3+ The solution volume was 20 ml, pH = 4, and temperature was 25 °C. After 24 h of adsorption, a sample was taken, and the concentration of gold ions in the solution was determined by ICP-OES. The adsorption rate was calculated according to formula (3). Subsequently, the composite aerogel in the gold ion aqueous solution was removed and washed with ultrapure water. Then, the composite aerogel was placed in a desorption solution consisting of 10 ml of 1 mol / L thiourea solution + 10 ml of 1 mol / L hydrochloric acid solution to desorb the gold ions on the composite aerogel. After 24 h of desorption, a sample was taken, and the concentration of gold ions in the desorption solution was determined by ICP-OES.

[0114] The desorption rate is defined as follows:

[0115]

[0116] In the formula, δ(%) is the desorption rate; C e (mg / L) is the equilibrium concentration of gold ions in the desorption solution; C o(mg / L) is the initial concentration of the gold ion solution before adsorption; ρ (%) is the adsorption rate of gold ions during the adsorption process (refer to formula (3)).

[0117] Example 35

[0118] Iron-polyphenol-coated composite aerogels were prepared according to the method in Example 1.

[0119] Test Example 8

[0120] The selective test was performed on the iron-polyphenol coating-modified composite aerogel prepared in Example 35, and the results are shown in Table 8.

[0121] Table 8. Adsorption and desorption rates of gold ions for the iron-polyphenol coated composite aerogel prepared in Example 35.

[0122] Loop count Adsorption rate (%) Desorption rate (%) 1 100 90.9 2 98.3 96.0 3 98.8 90.2 4 99.4 85.4 5 99.2 85.8

[0123] As shown in Table 8, the adsorption rate of the iron-polyphenol coating-modified composite aerogel was higher than 98% and the desorption rate was higher than 85% in all 5 cycles. Table 8 indicates that the iron-polyphenol coating-modified composite aerogel has good adsorption-desorption cycle stability.

[0124] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an iron-polyphenol coating-modified composite aerogel, characterized in that, The porous aerogel was immersed in a polyphenol aqueous solution, followed by liquid-phase deposition with the addition of a ferrous salt aqueous solution. After washing with ultrapure water, it was cross-linked with glutaraldehyde aqueous solution, then thoroughly washed with ethanol and ultrapure water, and finally thoroughly dried to obtain the final product. The porous aerogel is a reduced graphene oxide / multi-walled carbon nanotube aerogel. The polyphenol is tannic acid. The liquid-phase deposition time is 10-480 min, and the liquid-phase deposition temperature is 10-40 ℃.

2. The method for preparing the iron-polyphenol coating-modified composite aerogel according to claim 1, characterized in that, The ferrous salt is one or more of ferrous chloride tetrahydrate, anhydrous ferrous chloride, ferrous sulfate, ferrous bromide, and ferrous sulfide.

3. The method for preparing the iron-polyphenol coating-modified composite aerogel according to claim 1, characterized in that, The concentration of polyphenol aqueous solution is 8-80 mg / ml, the concentration of ferrous salt aqueous solution is 0.98-19.2 mg / ml, and the concentration of glutaraldehyde aqueous solution is 5-50 wt%.

4. The method for preparing the iron-polyphenol coating-modified composite aerogel according to claim 1, characterized in that, The soaking time is 1-30 minutes.

5. The method for preparing the iron-polyphenol coating-modified composite aerogel according to claim 1, characterized in that, The crosslinking time is 1-24 h, and the crosslinking temperature is 15-35 ℃.

6. The method for preparing the iron-polyphenol coating-modified composite aerogel according to claim 1, characterized in that, The drying time is 24-96 hours, and the drying temperature is -20 to 0℃.

7. The iron-polyphenol coating-modified composite aerogel obtained by the preparation method according to claim 1.

8. The application of a composite aerogel modified with an iron-polyphenol coating obtained by the preparation method of claim 1 in the process of adsorbing and reducing gold ions.

Images