Method for removing heavy metals in water body by using supramolecular hydrogel

Abstract

The invention belongs to the technical field of water body remediation, and particularly relates to a method for removing heavy metals in a water body by using supramolecular hydrogel. The supramolecular hydrogel adopted by the invention is supramolecular hydrogel of amino clay and carboxymethyl beta-cyclodextrin. The supermolecule hydrogel adhesive tape adopted by the invention has charges, has a porous structure, adsorbs heavy metal ions, realizes removal of the heavy metal ions in the water body, is high in environmental restoration efficiency and short in restoration period, and has the removal rate of the heavy metal ions in the water body of 99% or above in 14 days. The supramolecular hydrogel adopted by the invention is based on a porous structure and orthogonal non-covalent interaction-electrostatic interaction, and has excellent performance of efficiently capturing chemical pollutants, so that the supramolecular hydrogel can become an efficient platform for sustainable water body environment restoration.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental remediation, and particularly relates to a method for removing heavy metals in water by using a supramolecular hydrogel. Background Art

[0002] With the development of industry, heavy metal pollution such as cadmium (Cd) in the water environment has become increasingly serious. Phytoremediation, as a form of bioremediation, has received extensive attention due to its advantages such as environmental protection, sustainability, low cost, long-lasting effect, and easy implementation.

[0003] However, phytoremediation has limitations in the remediation of heavy metal pollution, such as long remediation cycle and low efficiency, which restricts its practical application. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for removing heavy metals in water by using a supramolecular hydrogel. The method provided by the present invention has a short remediation cycle and high remediation efficiency, and the removal rate of heavy metal ions in water is more than 99% at 14 days.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for removing heavy metals in soil or water by using a supramolecular hydrogel, comprising the following steps: adding a supramolecular hydrogel to the water to be remediated for adsorption;

[0007] The building unit of the supramolecular hydrogel comprises carboxymethyl-β-cyclodextrin and amino clay that interacts with the carboxymethyl-β-cyclodextrin by electrostatic force.

[0008] Preferably, the adsorption time is more than 1 day.

[0009] Preferably, the mass ratio of the supramolecular hydrogel to the heavy metal in the water to be remediated is 6-75:1.

[0010] Preferably, the adsorption temperature is 20-30 °C.

[0011] Preferably, the mass ratio of the carboxymethyl-β-cyclodextrin to the amino clay is 30-40:19-32.

[0012] Preferably, the preparation method of the supramolecular hydrogel comprises the following steps: mixing carboxymethyl-β-cyclodextrin and the first water to obtain a stock solution; mixing the stock solution, amino clay and the second water for gelation to obtain the supramolecular hydrogel.

[0013] Preferably, after gelation, the resulting product is left standing and then freeze-dried; the freeze-drying includes a pre-cooling stage and a drying stage in sequence.

[0014] Preferably, the temperature in the pre-cooling stage is not higher than -40°C, and the pre-cooling time with heat preservation is 1 - 1.5 h.

[0015] Preferably, the temperature in the drying stage is -70 to -50°C, and the drying time with heat preservation is 48 - 72 h.

[0016] Preferably, the standing time is 4 - 32 h.

[0017] The present invention provides a method for removing heavy metals in water by using a supramolecular hydrogel. The supramolecular hydrogel used in the present invention is an amino clay (AC) and carboxymethyl-β-cyclodextrin (CM-β-CD) supramolecular hydrogel, and its structure is represented as CM-β-CD@AC. The supramolecular hydrogel used in the present invention is charged and has a porous structure, which adsorbs heavy metal ions to achieve the removal of heavy metal ions in water. It has a high environmental remediation efficiency and a short remediation cycle. The removal rate of heavy metal ions in water is over 99% at 14 days.

[0018] The supramolecular hydrogel used in the present invention is based on a porous structure and orthogonal non-covalent interactions - electrostatic interactions, and has excellent performance in efficiently capturing chemical pollutants, making it have the potential for sustainable water environment remediation. Detailed implementation mode

[0019] The present invention provides a method for removing heavy metals in water by using a supramolecular hydrogel, comprising the following steps:

[0020] Adding a supramolecular hydrogel to the water body to be remediated for adsorption;

[0021] The building units of the supramolecular hydrogel include carboxymethyl-β-cyclodextrin and amino clay that interacts with the carboxymethyl-β-cyclodextrin by electrostatic force.

[0022] In the present invention, the heavy metals in the water body to be remediated may include one or more of lead, copper, and cadmium.

[0023] In the present invention, the concentration of heavy metals in the water body to be remediated may not be higher than 17.8 mmol / L, and specifically may be 0.5 mmol / L, 1 mmol / L, 5 mmol / L, 10 mmol / L, or 15 mmol / L.

[0024] In the present invention, the building units of the supramolecular hydrogel include carboxymethyl-β-cyclodextrin; the structure of the carboxymethyl-β-cyclodextrin is as shown in Formula A:

[0025]

[0026] In the present invention, the building unit of the supramolecular hydrogel includes amino clay that interacts with carboxymethyl-β-cyclodextrin by electrostatic force; the mass ratio of carboxymethyl-β-cyclodextrin to amino clay can be 30-40:19-32, specifically 30:19, 30:25, 30:32, 40:19, 40:25 or 40:32.

[0027] In the present invention, the preparation method of the supramolecular hydrogel may include the following steps: mixing carboxymethyl-β-cyclodextrin and the first water to obtain a stock solution; mixing the stock solution, amino clay and the second water for gelation to obtain the supramolecular hydrogel.

[0028] In the present invention, carboxymethyl-β-cyclodextrin and the first water are mixed to obtain a stock solution. In the present invention, the first water is preferably deionized water.

[0029] In the present invention, the molar volume ratio of carboxymethyl-β-cyclodextrin to the first water is preferably 10 mmol:(9-12) mL, specifically 10 mmol:9 mL, 10 mmol:10 mL, 10 mmol:11 mL or 10 mmol:12 mL.

[0030] After obtaining the stock solution, in the present invention, the stock solution, amino clay and the second water are mixed (denoted as the first mixing) for gelation to obtain the supramolecular hydrogel. In the present invention, the preparation method of the amino clay (AC) preferably refers to Chinese Patent CN112011098A.

[0031] In the present invention, the second water is preferably deionized water.

[0032] In the present invention, the first mixing is preferably: stirring and mixing amino clay and water (denoted as stirring A) until the solution is clear to obtain an aqueous amino clay solution, and then continuously stirring and mixing the stock solution and the aqueous amino clay solution (denoted as stirring B).

[0033] In the present invention, the mass-volume ratio of amino clay to the stock solution is preferably (0.3-0.4) g:(0.15-0.25) mL, specifically 0.3 g:0.15 mL, 0.35 g:0.15 mL, 0.4 g:0.15 mL, 0.3 g:0.2 mL, 0.35 g:0.2 mL, 0.4 g:0.2 mL, 0.3 g:0.25 mL, 0.35 g:0.25 mL or 0.4 g:0.25 mL.

[0034] In the present invention, the volume ratio of the stock solution to the second water is preferably 0.15-0.25:1, specifically 0.15:1, 0.17:1, 0.19:1, 0.21:1, 0.23:1 or 0.25:1.

[0035] In the present invention, the molar concentration of the stock solution is preferably 0.8 - 1.1 mol / L, and specifically can be 0.8 mol / L, 0.9 mol / L, 1 mol / L or 1.1 mol / L.

[0036] In the present invention, the rotation speed of stirring A is preferably 480 - 960 rpm, and specifically can be 480 rpm, 600 rpm, 720 rpm, 840 rpm or 960 rpm; the stirring time is preferably 20 - 40 min, and specifically can be 25 min, 30 min or 35 min.

[0037] In the present invention, the rotation speed of stirring B is preferably 480 - 960 rpm, and specifically can be 480 rpm, 600 rpm, 720 rpm, 840 rpm or 960 rpm; the stirring time is preferably 10 - 15 min, and specifically can be 11 min or 12 min.

[0038] In the present invention, the coagulation temperature is preferably 15 - 40 °C, and specifically can be 20 °C or 25 °C.

[0039] In the present invention, after coagulation, it preferably further includes allowing the obtained product to stand and then freeze-drying.

[0040] In the present invention, the standing time is preferably 4 - 32 h, and specifically can be 12 h or 24 h.

[0041] In the present invention, the freeze-drying preferably includes successively performing a precooling stage and a drying stage; the temperature of the precooling stage is preferably not higher than -40 °C, and specifically can be -40 °C, -45 °C, -50 °C, -55 °C or -60 °C, and the precooling holding time is preferably 1 - 1.5 h, and specifically can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h.

[0042] In the present invention, the temperature of the drying stage is preferably -70 - -50 °C, and specifically can be -70 °C, -65 °C, -60 °C, -55 °C or -50 °C, and the drying holding time is preferably 48 - 72 h, and specifically can be 48 h, 54 h, 60 h, 66 h or 72 h; the equipment for freeze-drying is preferably a freeze dryer.

[0043] In the present invention, the mass ratio of the supramolecular hydrogel to the heavy metal in the water body to be repaired can be 6 - 75:1, and specifically can be 6:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 54:1, 60:1, 70:1 or 75:1. By adding the supramolecular hydrogel in the above amount in the present invention, it helps to improve the adsorption effect of heavy metals.

[0044] In the present invention, the adsorption time can be more than 1 day, specifically 1 day, 2 days, 5 days, 10 days, 15 days, 20 days, 30 days, 40 days or 50 days.

[0045] In the present invention, the adsorption temperature can be 20 - 30 °C, specifically 20 °C, 22 °C, 24 °C, 26 °C, 28 °C or 30 °C.

[0046] To further illustrate the present invention, the following describes the solution of the present invention in detail with reference to embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0047] Example 1

[0048] In this example, a supramolecular hydrogel was prepared, and the preparation method included the following steps:

[0049] (1) Preparation of amino clay, the synthesis route refers to Chinese Patent CN112011098A: Weigh 10.08 g of magnesium chloride hexahydrate and 3-aminopropyltriethoxysilane, dissolve them in 240 mL of absolute ethanol, slowly stir for 24 h, centrifuge at 4000 r / min for 8 min to collect the white precipitate, wash it 3 times with ethanol, and vacuum dry at 40 °C for 48 h, then grind it to obtain amino clay, which is a light yellow powder.

[0050] (2) Preparation of the stock solution: Add carboxymethyl-β-cyclodextrin to deionized water and stir to dissolve it, sonicate for 1 h to make it dissolve thoroughly. The addition ratio of carboxymethyl-β-cyclodextrin to deionized water is 10 mmol:9 mL to obtain a stock solution with a concentration of 1.1 mol / L.

[0051] (3) Take 0.4 g of the amino clay prepared in step (1) and add it to deionized water, stir at 900 r / min for 20 min until the solution becomes clear. Then add the stock solution prepared in step (2) to the above solution and continue to stir for 15 min. The addition ratio of amino clay, stock solution and deionized water is 0.4 g:0.15 mL:1 mL. Let it stand for 12 h and freeze-dry at -60 °C for 72 h to obtain a powdery supramolecular hydrogel.

[0052] Application Example 1

[0053] In this application example, the supramolecular hydrogel prepared in Example 1 was used to remove cadmium from the water body to be repaired. The specific steps are as follows:

[0054] Add 0.7354 g of the supramolecular hydrogel to 150 mL of the water body to be repaired. The Cd concentration in the water body before repair is 67.25 ± 2.47 mg / L. After adsorption for 14 d, measure the cadmium concentration in the water body and calculate the removal rate of cadmium. To ensure the repeatability and reliability of the results, repeat 3 times and take the average value. The results are shown in Table 1.

[0055] Table 1 Cd removal in Application Example 1

[0056] Cd concentration in water before adsorption (mg / L) Cd concentration in water after adsorption (mg / L) 67.25±2.47 0.55±0.15

[0057] As can be seen from Table 1, the supramolecular hydrogel provided by the present invention effectively removes cadmium ions in water, and the removal rate reaches 99.2%.

[0058] Application Example 2

[0059] This application example is the same as that of Application Example 1, except that: the addition amount of the supramolecular hydrogel is 0.2770 g, and the results are shown in Table 2.

[0060] Table 2 Cd removal in Application Example 2

[0061] Cd concentration in water before adsorption (mg / L) Cd concentration in water after adsorption (mg / L) 67.25±2.47 0.28±0.01

[0062] As can be seen from Table 2, the supramolecular hydrogel effectively removes cadmium ions in water, and the removal rate reaches 99.6%.

[0063] Application Example 3

[0064] This application example is the same as that of Application Example 2, except that: the addition amount of the supramolecular hydrogel is 0.3677 g, and the results are shown in Table 3.

[0065] Table 3 Cd removal in Application Example 3

[0066] Cd concentration in water before adsorption (mg / L) Cd concentration in water after adsorption (mg / L) 67.25±2.47 0.40±0.01

[0067] As can be seen from Table 3, the supramolecular hydrogel effectively removes cadmium ions in water, and the removal rate reaches 99.4%.

[0068] Application Example 4

[0069] This application example is the same as that of Application Example 1, except that: the addition amount of the supramolecular hydrogel is 0.7078 g, and the results are shown in Table 4.

[0070] Table 4 Cd removal in Application Example 4

[0071] Cd concentration in water before adsorption (mg / L) Cd concentration in water after adsorption (mg / L) 67.25±2.47 0.27±0.03

[0072] As can be seen from Table 4, the supramolecular hydrogel effectively removes cadmium ions in water, and the removal rate reaches 99.6%.

[0073] Application Example 5

[0074] This application example is the same as that of Application Example 1, except that: the addition amount of the supramolecular hydrogel is 0.2666 g, and the results are shown in Table 5.

[0075] Table 5 Cd removal in Application Example 5

[0076] Cd concentration in water before adsorption (mg / L) Cd concentration in water after adsorption (mg / L) 67.25±2.47 0.43±0.02

[0077] As can be seen from Table 5, the supramolecular hydrogel effectively removed cadmium ions in the water body, and the removal rate reached 99.36%.

[0078] From the above embodiments, it can be seen that the method provided by the present invention can effectively remove heavy metal ions in the water body. The removal rate is above 99% at 14 days, quickly and effectively repairing the polluted water body, which is of great significance for water resource utilization.

[0079] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. Other embodiments can be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for removing heavy metals from water using supramolecular hydrogel, characterized in that: The following steps are involved: Adding supramolecular hydrogel to the water body to be repaired for adsorption; The building blocks of the supramolecular hydrogel include carboxymethyl beta-cyclodextrin and amino clay that interacts with the carboxymethyl beta-cyclodextrin through electrostatic force.

2. The method according to claim 1, characterized in that The adsorption time is more than 1 day.

3. The method according to claim 1, characterized in that The mass ratio of the supramolecular hydrogel to the heavy metals in the water body to be repaired is 6 to 75:

1.

4. The method according to claim 1 or 2, characterized in that: The adsorption temperature is 20-30°C.

5. The method according to claim 1, characterized in that The mass ratio of the carboxymethyl β-cyclodextrin to the amino clay is 30-40:19-32.

6. The method according to claim 1, characterized in that The preparation method of the supramolecular hydrogel comprises the following steps: mixing carboxymethyl-β-cyclodextrin and first water to obtain a stock solution; and mixing the stock solution, amino clay and second water to form a coagulation to obtain the supramolecular hydrogel.

7. The method according to claim 6, characterized in that After the coagulation, the method further includes allowing the obtained product to stand for freeze drying; the freeze drying includes sequentially performing a precooling stage and a drying stage.

8. The method according to claim 7, characterized in that The temperature in the precooling stage is not higher than -40°C, and the precooling time is 1 to 1.5 hours.

9. The method according to claim 7 or 8, characterized in that: The temperature in the drying stage is -70 to -50°C, and the heat preservation and drying time is 48 to 72 hours.

10. The method according to claim 7, characterized in that The standing time is 4 to 32 hours.

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