CN116618033A - A kind of preparation method of organically modified sodium-based montmorillonite - Google Patents

Abstract

The invention discloses a method for preparing organically modified sodium-based montmorillonite. Firstly, sulfuric acid is used to completely dissolve thymine; After preservation; the sodium-based montmorillonite is modified with thymine by solution stirring method, which avoids the problems of high energy consumption and complicated steps of hydrothermal method and microwave heating method, and the synthesized new organic montmorillonite has a large adsorption capacity for Hg2+ , the removal rate is high, and will not cause secondary pollution to the environment. The modified T-MMT not only increases the interlayer spacing, but also changes the charge properties and hydrophobicity of the surface of the montmorillonite, making it easier for the montmorillonite to absorb the pollutants in the wastewater. Mercury ions.

Description

A kind of preparation method of organically modified sodium-based montmorillonite

technical field

The invention belongs to the technical field of environmental restoration and fixation, and in particular relates to a preparation method of organically modified sodium-based montmorillonite.

Background technique

In recent years, clay minerals have been widely studied for immobilizing pollutants due to their important roles in the field of environment and toxic waste management. Among clay minerals, montmorillonite is a potentially good adsorption material due to its low cost, high abundance, large surface area, high ion exchange capacity, strong chemical and mechanical stability, and layered structure. Montmorillonite is a natural nanomaterial known as "universal clay". Its unit cell is composed of two layers of silicon-oxygen tetrahedron sandwiching a layer of aluminum-oxygen octahedron, which is a typical 2:1 layered structure. Silicate minerals. The montmorillonite layer is negatively charged, which is beneficial for cations to enter the montmorillonite layer, making the montmorillonite layer change from hydrophilic to lipophilic.

Due to the hydrophilic and oleophobic nature of the surface of montmorillonite, the affinity for organic pollutants is not high, the adsorption selectivity to heavy metal ions is poor, and the adsorption capacity is low, resulting in the large-scale application of montmorillonite in actual sewage treatment. Modification treatment makes the surface hydrophobic, which can significantly improve its ability to remove pollutants in aqueous solution. Organically modified montmorillonite shows excellent effects in the effective prevention and control of pollution and can adapt to more complex waters The market application potential is huge. The organic modification methods of montmorillonite mainly include microwave heating method, solution stirring method and hydrothermal method. adsorption of pollutants. Modification by microwave heating method requires a special reaction device. The modification effect is affected by the reaction time and needs to be carried out in a solvent, so it also has certain limitations. The hydrothermal method is to mix montmorillonite with an organic modifier. It is carried out in a hydrothermal reactor and requires high energy. Therefore, this experiment chooses simple and efficient solution stirring method to prepare organic montmorillonite; secondly, the organic modifiers in the prior art mainly include surfactants and coupling agents. Surfactants and coupling agents are likely to cause secondary pollution and are toxic to the environment when used in large quantities.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing organically modified sodium-based montmorillonite to solve the problem of high energy consumption and cumbersome production steps of the prior art hydrothermal method and microwave heating method, and the organic modifier is toxic and easily Lead to technical problems such as secondary pollution.

Technical scheme of the present invention is:

A method for preparing organically modified sodium-based montmorillonite comprises the following steps: firstly, sulfuric acid is used to completely dissolve thymine; secondly, the thymine solution and sodium-based montmorillonite are blended and stirred; finally, the blended solution is washed and dried for storage.

The mass ratio of thymine to sodium montmorillonite is 7:100.

The method for completely dissolving thymine with sulfuric acid is: weigh thymine and dissolve it in 1.5 mol/L sulfuric acid solution according to the mass ratio of thymine to sodium montmorillonite, stir in a water bath at 50°C for 120 minutes to completely dissolve thymine.

The blending and stirring time was 10 hours.

The method of washing and drying the blend is as follows: cool the blend to room temperature, wash 3 times with ultrapure water and centrifuge for 5 minutes on a centrifuge at 4500r/min, pour the supernatant, and then place the sample in an electric blast drying box Dry at 55°C for 6h.

Pass the dried T-MMT through a 100-mesh nylon sieve, and finally put the finished thymidine montmorillonite into a sealed bag for storage.

Beneficial effects of the present invention:

The invention adopts a novel, environment-friendly modifier thymine to modify the sodium-based montmorillonite so as to improve the mercury adsorption capacity of the sodium-based montmorillonite without polluting the environment. In the presence of Hg ²⁺ , thymine specifically binds to Hg ²⁺ , forming a thymine-Hg ²⁺ -thymine mismatch (T-Hg ²⁺ -T), and this residue of thymine in the system can be used as The mercury ion sensor has a good recognition group and can specifically recognize mercury ions. Combined with the specificity of Hg ²⁺ and thymine, the sodium-based montmorillonite was modified with thymine by the solution stirring method, which avoided the problems of high energy consumption and cumbersome steps of the hydrothermal method and microwave heating method, and the synthetic new organic Montmorillonite has a large adsorption capacity for Hg ²⁺ , high removal rate, and will not cause secondary pollution to the environment. The modified T-MMT not only increases the layer spacing, but also changes the charge properties and hydrophobicity of the montmorillonite surface. , making it easier for montmorillonite to absorb mercury ions in wastewater.

The invention designs and synthesizes thymine as an organic modifier, adopts a simple and fast solution stirring method to modify sodium-based montmorillonite, and solves the technical problems of high energy consumption in hydrothermal method and microwave heating method. The adsorption capacity of montmorillonite itself is limited, and organic modification can increase the adsorption performance of montmorillonite, but most of the organic modifiers are highly toxic. This patent synthesizes a new green and pollution-free organic montmorillonite through the thymine modifier. The hydrophilicity of the surface of montmorillonite becomes hydrophobic, which increases its interlayer distance, thereby improving its ability to remove Hg ²⁺ from aqueous solution.

The invention designs and synthesizes organic montmorillonite with thymine as an intercalation agent. Thymine is an important component of genetic material. The synthesized thymine montmorillonite will not pollute the environment and can be used for fixing soil pollutants.

Description of drawings

Fig. 1 is the specific embodiment of the present invention T, T-MMT, Na-MMT infrared spectrogram;

Fig. 2 is the FT-IR spectrogram of montmorillonite and organomontmorillonite of the specific embodiment of the present invention;

Fig. 3 is the XPS spectrogram before montmorillonite modification of the specific embodiment of the present invention;

Fig. 4 is the XPS spectrogram after montmorillonite modification of the specific embodiment of the present invention;

Fig. 5 is a graph showing the interaction between thymine and Hg ²⁺ in a specific embodiment of the present invention.

Detailed ways

The technical solution of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

A preparation method of organically modified sodium-based montmorillonite, which mainly includes: firstly, thymine is completely dissolved with sulfuric acid (thymine in this experiment is insoluble in water and hot water), and secondly, the thymine solution is mixed with sodium-based montmorillonite Blend and stir under certain conditions, and finally wash, dry and store the samples,

The mass ratio of thymine and sodium montmorillonite in the present invention is 7:100, so that before modification, the weight percentages of sodium montmorillonite elements are: O: 59.61%, Si: 23.65%, Al: 6.57%, C: 5.96%, Na: 2.17% and Mg: 2.04%; after modification, the raw material composition weight percentage of organically modified montmorillonite is: O: 58.75%, Si: 21.30%, Al: 6.15%, C: 10.44 %, N: 2.26 and Mg: 1.10%.

After modification, the interlayer Na ion of organically modified montmorillonite changed from 2.04% to 0%, the content of C element increased from 5.96% to 10.44%, and the content of N element increased from 0% to ^2.26 %. The -NH functional group is specifically combined, and the increase in the content of C and N elements is mainly the result of thymine intercalation, which means that organic modification can improve the adsorption capacity of sodium-based montmorillonite and improve the removal of Hg in water by sodium-based montmorillonite Efficiency and Hg fixation capacity in soil.

The method for completely dissolving thymine with sulfuric acid is:

Weigh thymine according to the mass ratio of thymine to sodium montmorillonite and dissolve it in 1.5mol/L sulfuric acid solution, stir in a water bath at 50°C for 120 minutes to completely dissolve thymine; the principle of taking sulfuric acid solution is to ensure that thymine Completely dissolved shall prevail.

The blending and stirring time is 10 hours to ensure that thymine has been inserted into the surface of the Na-montmorillonite, and part of it enters the Na-montmorillonite layer. If the time is too short, the thymine intercalation will be incomplete, and if the time is too long, resources will be wasted.

The method of washing and drying the blend is as follows:

The blend was cooled to room temperature, washed 3 times with ultrapure water and centrifuged for 5 minutes on a centrifuge at 4500r/min. After pouring the supernatant, the sample was dried at 55°C for 6 hours in an electric blast drying oven. The cooling method is used in the present invention. The purpose of cooling to room temperature is to allow the crystallization of thymine not combined with Na-montmorillonite for easy washing, and the purpose of washing with ultrapure water is to remove excess thymine.

Pass the dried thymine montmorillonite (T-MMT) through a 100-mesh nylon sieve to make the organic montmorillonite particles uniform in size and ensure the accuracy of the adsorption experiment. Finally, put the finished thymine montmorillonite into a sealed bag save in .

The following example further elaborates on the scheme of the present invention:

Step 1. Weigh 0.7g thymine and dissolve it in 1.5mol/L 100ml sulfuric acid solution, stir in a water bath at 50°C for 120min to completely dissolve thymine;

Step 2, slowly add 10 g of Na-montmorillonite, and stir in a water bath for 10 h;

Step 3. After the solution is cooled to room temperature, wash it 3 times with ultrapure water and centrifuge it in a centrifuge at 4500r/min for 5min. After pouring off the supernatant, dry the sample in an electric blast drying oven at 55°C for 6h;

Step 4, passing the obtained T-MMT through a 100-mesh nylon sieve, and finally putting the obtained thymidine montmorillonite finished product into a sealed bag for storage.

The present invention has synthesized the organic montmorillonite modified with thymine and sodium montmorillonite as raw materials, through Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron energy (XPS) Characterization of the structure of montmorillonite before and after modification shows that thymine has been inserted into the surface of Na-montmorillonite, and part of it has entered the interlayer of Na-montmorillonite. The intercalation of thymine did not change the structure of Na-based montmorillonite, and no collapse occurred between layers, indicating that the modification was successful.

The aqueous solution used in the experimental synthesis process is ultrapure water made in the laboratory.

The thymine montmorillonite of the invention has potential applications in fields such as fixing soil pollutants and removing heavy metals in water. In this experiment, T-MMT was applied to the mercury-contaminated soil in the greenhouse to grow pakchoi and garlic. Compared with the mercury-contaminated soil without T-MMT, the mercury flux decreased, and the roots, stems and leaves of pakchoi and garlic all decreased to varying degrees. It shows that T-MMT can fix active mercury in soil. Adsorption experiment: the initial concentration of mercury is 200mg/L, the adsorption time is 2h, and the conditions are pH=5. The adsorption capacity of the original montmorillonite (Na-MMT) was 8.64mg/g, the adsorption capacity of the modified T-MMT was 44.72 mg/g, and the adsorption capacity of T-MMT was 5.18 times that of Na-MMT. Desorption experiment: the initial concentration of mercury is 200mg/L, the desorption agent is 0.01mol/L NaNO ₃ , the desorption rate of Na-MMT is 94.22%, and that of T-MMT is 14.32%. T-MMT can significantly reduce the mercury leaching, and adsorb and fix Hg ² on the interlayer and surface of montmorillonite. The above experiments show that since montmorillonite itself is a component in the soil, T-MMT can be directly applied to mercury-contaminated soil to reduce the total mercury concentration in plants, and T-MMT can be used in mercury sewage to achieve the removal of mercury in water. purpose of mercury.

Structural Characterization of Thymine Montmorillonite

The formation of thymine montmorillonite (T-MMT) was investigated by Fourier transform infrared spectroscopy, and the thymine and montmorillonite before and after modification were characterized by infrared spectroscopy. As shown in Figure 1, Na-MMT and T-MMT The infrared spectrum of MMT has characteristic peaks of different intensities at similar wavelengths. The wave numbers of 3453 and 3600cm ^-1 belong to the stretching vibration peaks of Al-OH and Si-OH in the montmorillonite structure, and the absorption band at 1617cm ^-1 corresponds to the OH stretching band of H ₂ O. The absorption bands at 1062 and 1016cm ^-1 are Si-O stretching vibration peaks, and the absorption bands at 400-600cm ^-1 are Si-O and Al-O bending vibration peaks. The infrared spectrum of T-MMT shows the stretching vibration of C=O at 1695cm ^-1 through the change of infrared spectrum, and the absorption band of 3396cm ^-1 is the stretching vibration peak of -OH and NH. 1205cm ^-1 may be the bending vibration of NH, and the stretching vibration peak of -OH of montmorillonite after modification obviously shifts to the right, from 3453cm ^-1 to 3396cm ^-1 . It shows that the modification has been successful, and thymine may remain on the surface of montmorillonite.

Fig. 2 is the X-ray diffraction pattern of Na-MMT and T-MMT. Through the comparison of the first peak positions in the figure, it is found that the first peak positions of Na-MMT and T-MMT are 2θ=7.13° and 6.25° respectively. The above results show that the diffraction peaks generally shift to lower angles after modification. . According to the Bragg equation: 2dsinθ=λ (θ is the half-diffraction angle, λ is the incident X-ray wavelength, λ=0.154nm). The analysis shows that the interplanar distances of Na-MMT and T-MMT montmorillonites are 1.24 and 1.41nm respectively, and the interplanar distances increase by 0.17nm. The results of the data show that the ions between thymine and montmorillonite layers undergo ion exchange, which expands the distance between montmorillonite layers, indicating that thymine enters between montmorillonite layers.

In order to clarify the composition of montmorillonite before and after modification, X-ray photoelectron spectroscopy (XPS) was used to characterize the two materials. Figure 3 and Figure 4 are the XPS diagrams before and after modification of montmorillonite. From the full spectrum before and after modification and element composition analysis, it can be seen that the Na ⁺ between the layers of montmorillonite is replaced by T, and the content of N elements ranges from 0% to 2.26 %, the content of C element after modification increased from 5.96% to 10.44%, which is due to the contribution of thymine, indicating that the composite material was successful. The XPS fine spectrum of C1s in Figure 4 shows that the spectrum shows three peaks at 284.8eV, 286.6eV, and 289.0eV, which are CC, CO, and C=ON, respectively. The binding energy at 531.13eV in the O1S spectrum in Figure 4 is Si-O, and the binding energy at 532.4eV and 534.7eV are C=O and COC, respectively. The peak at 286.8 eV is CN. The fine XPS spectrum of N at 289.07eV shows that the binding energy of N s1 corresponds to NH and O=C-NH at 400.6eV and 402.0eV, respectively. The fine spectra of Si(2p) in Figure 3 and Figure 4 are basically the same, indicating that the structure of the modified montmorillonite has not been destroyed. The binding energies of 102.94eV and 105.13eV are Si-O- and SiO ₂ , respectively. It shows that thymine is successfully retained on the surface of montmorillonite.

Claims (6)

1. A preparation method of organic modified sodium montmorillonite is characterized in that: firstly, completely dissolving thymine by sulfuric acid, secondly, blending and stirring the thymine solution and sodium montmorillonite, and finally, washing and drying the blending solution and preserving the blending solution.

2. The method for preparing the organically modified sodium montmorillonite according to claim 1, which is characterized in that: the mass ratio of thymine to sodium montmorillonite is 7:100.

3. the method for preparing the organically modified sodium montmorillonite according to claim 1, which is characterized in that: the method for completely dissolving thymine by sulfuric acid comprises the following steps: thymine is weighed according to the mass ratio of thymine to sodium montmorillonite, dissolved in sulfuric acid solution of 1.5mol/L, and stirred for 120min at 50 ℃ in water bath to completely dissolve the thymine.

4. The method for preparing the organically modified sodium montmorillonite according to claim 1, which is characterized in that: the blending time was 10 hours.

5. The method for preparing the organically modified sodium montmorillonite according to claim 1, which is characterized in that: the method for washing and drying the blending liquid comprises the following steps: the blend was cooled to room temperature, washed 3 times with ultrapure water and centrifuged on a 4500r/min centrifuge for 5min, after which the supernatant was poured off and the sample dried in an electrothermal forced air drying oven at 55 ℃ for 6h.

6. The method for preparing the organically modified sodium montmorillonite according to claim 1, which is characterized in that: the preservation method comprises the following steps: and (3) sieving the dried T-MMT with a 100-mesh nylon sieve, and finally, placing the obtained thymine montmorillonite finished product into a sealed bag for storage.