Sulfydryl modified mesoporous silica and preparation method and application thereof

Abstract

The invention relates to the technical field of ion adsorption, in particular to sulfydryl modified mesoporous silica and a preparation method and application thereof.The preparation method comprises the following steps that a surfactant serves as a template, tetraethyl silicate serves as a silicon source, and mesoporous silica is prepared through hydrolytic condensation under the alkaline condition; (3-mercaptopropyl) trimethoxysilane is adopted to carry out sulfydryl modification on the prepared mesoporous silicon dioxide, and the sulfydryl modified mesoporous silicon dioxide is obtained. The novel mesoporous silica nanoparticles prepared by the method have the advantages of higher specific surface area, safer used solvent and lower synthesis cost, the adsorption capacity on Hg < 2 + > in wastewater can be increased by utilizing sulfydryl modified mesoporous silica, and the material has high selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of ion adsorption, and in particular to a mercapto-modified mesoporous silica and a preparation method and application thereof. Background Art

[0002] Mercury (Hg) is persistent, long-range mobile and bioaccumulative, and is one of the most toxic heavy metal pollutants in the ecosystem. Long-term exposure to mercury can lead to serious health problems. Mercury pollution includes natural and anthropogenic sources. Compared with mercury emitted from natural activities, human activities have a greater impact on the mercury content in the environment. Currently, mercury and its compounds are still used in the production of telescopes, fluorescent lamps, batteries and other equipment. Many industries such as thermal power plants, cement kilns, chlor-alkali plants and non-ferrous metal industries also generate large amounts of mercury-containing waste.

[0003] Due to Hg 2+ It cannot be decomposed and destroyed. The treatment of mercury-containing wastewater can only be carried out through the phase transfer of mercury ions or the change of physical and chemical state. At present, the treatment methods of mercury-containing wastewater mainly include chemical precipitation, ion exchange, membrane separation and adsorption. Among them, the adsorption method has been widely used due to its flexibility, high efficiency and economy. Various conventional adsorbents (activated carbon, zeolite, etc.) and unconventional adsorbents (MOF, COF, nanoparticles, etc.) have been studied for the treatment of mercury-containing wastewater. Mesoporous silica can be used as a good adsorption material after modification due to its advantages such as stable skeleton, orderly pores, adjustable pore size and large specific surface area. According to the theory of hard and soft acids and bases, sulfur is highly selective for mercury. Introducing sulfur-containing active groups into mesoporous silica can increase its active sites and effectively improve surface properties and pore structure. However, the preparation process of mesoporous silica in the existing technology is cumbersome, time-consuming and costly. A large amount of toxic and harmful reagents are used in the process, which limits the large-scale production of materials. In addition, when unmodified mesoporous silica is used to treat mercury-containing wastewater, it is sensitive to Hg. 2+ The adsorption capacity is poor. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a mercapto-modified mesoporous silica and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] In one aspect, a method for preparing mercapto-modified mesoporous silica is provided, comprising the following steps:

[0007] Mesoporous silica was prepared by hydrolysis and condensation under alkaline conditions using surfactant as template and tetraethyl silicate as silicon source.

[0008] (3-mercaptopropyl)trimethoxysilane is used to modify the prepared mesoporous silica with mercapto groups to obtain mercapto-modified mesoporous silica.

[0009] Furthermore, the preparation method of mesoporous silica specifically includes the following sub-steps:

[0010] (1) 200-300 mL of deionized water and 0.5-1.0 g of triethanolamine are uniformly mixed, and 3-5 g of hexadecyltrimethylammonium bromide are added, and the mixture is heated and stirred to completely dissolve the surfactant in the organic amine aqueous solution;

[0011] (2) Weigh 30 g of tetraethyl silicate and quickly add it to the solution of (1), heating and stirring;

[0012] (3) After the obtained product is centrifuged or filtered, it is repeatedly washed with ethanol and deionized water until it becomes neutral, thereby obtaining mesoporous silica with a template;

[0013] (4) removing the template agent hexadecyltrimethylammonium bromide from the obtained product;

[0014] (5) Wash with deionized water and ethanol until neutral, and vacuum dry to obtain a mesoporous silica product.

[0015] Furthermore, in step (1), the mixture is placed in an oil bath at 80.0-90.0° C. and stirred for 1-2 hours under a magnetic stirrer to completely dissolve the surfactant in the organic amine aqueous solution.

[0016] Furthermore, in step (2), the oil bath is set at 80.0-90.0° C., the magnetic stirrer is set at a speed of 1000-2000 rpm and stirred for 2-3 hours.

[0017] Furthermore, the method of step (4) is specifically as follows: adding a 1M hydrochloric acid and ethanol 1:1 mixed solution to the obtained product, condensing and refluxing for 6 to 8 hours, filtering or centrifuging, repeating the operation multiple times to remove the template, and performing centrifugation or filtering.

[0018] Furthermore, the method for preparing mercapto-modified mesoporous silica from mesoporous silica specifically comprises the following steps:

[0019] Mesoporous silica is uniformly dispersed in an appropriate amount of ethanol solution, the pH is adjusted to 8-10, (3-mercaptopropyl)trimethoxysilane is dropped into the above mixture in a ratio of 1:1 in volume / mass to mesoporous silica and stirred continuously to prepare mercapto-modified mesoporous silica.

[0020] Furthermore, (3-mercaptopropyl)trimethoxysilane and mesoporous silica are mixed and stirred continuously, blown into vacuum with nitrogen, vigorously stirred at room temperature under nitrogen atmosphere, collected by centrifugation or filtration, repeatedly washed with ethanol and deionized water until neutral, and vacuum dried to obtain mercapto-modified mesoporous silica.

[0021] On the other hand, a thiol-modified mesoporous silica is provided for Hg removal in wastewater. 2+ Application in adsorption.

[0022] The beneficial effects of the present invention are:

[0023] (1) The preparation process of the present invention is simple, time-saving, low-cost, and safe to use solvents. The prepared material is nanoscale and has a high specific surface area (700m 2 / g);

[0024] (2) After thiol modification, Hg in wastewater 2+ The adsorption capacity is large and the adsorption efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the method of the present invention;

[0026] Figure 2 This is an electron microscope image of the mesoporous silica prepared in the example;

[0027] Figure 3 This is an electron micrograph of the mercapto-modified mesoporous silica prepared in the example;

[0028] Figure 4 Schematic diagram of the effect of adsorbent dosage on adsorption capacity in Experimental Example 1;

[0029] Figure 5 is the adsorption kinetic curve in Experimental Example 2;

[0030] Figure 6 Schematic diagram of adsorption selectivity in Experimental Example 3. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0032] Example

[0033] (1) Add 200 mL of deionized water to a flask, weigh 0.694 g of triethanolamine (TEA) and add it to the flask. After shaking by hand, add 4.37 g of hexadecyltrimethylammonium bromide (CTAB). Incubate in an oil bath at 80.0°C and stir under a magnetic stirrer for 1 h to completely dissolve the surfactant in the organic amine water.

[0034] (2) Weigh 29.16 g of tetraethyl silicate (TEOS) and quickly add it to the surfactant solution. The mixture is stirred in a magnetic stirrer oil bath at 80.0° C. and 1200 rpm for 2 h.

[0035] (3) placing the obtained product into a centrifuge tube, centrifuging it, and washing it with deionized water and ethanol until it becomes neutral, thereby obtaining a product with a template (CTAB-SiO2);

[0036] (4) CTAB-SiO2 contains a template. A 1M hydrochloric acid and ethanol 1:1 mixed solution was added to the product. After condensation and reflux for 6 h, centrifugation was performed at 10000 rpm / min. The operation was repeated twice.

[0037] (5) washing with deionized water and ethanol until neutral, and drying in vacuum at 60° C. to obtain the product mesoporous silica;

[0038] (6) 1.00 g of mesoporous silica nanospheres were uniformly dispersed in a mixture containing NH3·H2O (5.5 mL) and ethanol (50 mL). After ultrasonic treatment for 30 min, (3-mercaptopropyl)trimethoxysilane (1 mL) was dropped into the above mixture and stirred continuously, and then purged with nitrogen for 10 min. After vigorous stirring at room temperature under nitrogen atmosphere for 24 h, the product was collected by centrifugation and repeatedly washed with ultrapure water and ethanol. Finally, it was dried in a vacuum oven at 50 ° C for 12 hours to obtain mercapto-modified mesoporous silica (SiO2-SH).

[0039] like Figure 2-3 As shown, the particle size of the mesoporous silica particles prepared in this example is about 50-100 nm, nearly spherical, and relatively dispersed. The particle size of the mercapto-modified mesoporous silica particles is about 50-100 nm, nearly spherical, and the particles are denser than the unmodified mesoporous silica.

[0040] Test Example 1: Effect of adsorbent dosage on adsorption capacity

[0041] Preparation of 250mg / L Hg 2+ solution, take 10 mL of the solution and add it into a centrifuge tube, add 3, 5, 10, 15, 20, 25 and 30 mg of SiO2 and SiO2-SH material prepared in the example to the solution, shake at 180 r / min for 12 h, and then measure the adsorption capacity.

[0042] The experimental results are as follows Figure 4 As shown in Figure 2, with the increase of adsorbent dosage, the mesoporous silica and mercapto-modified mesoporous silica have a significant effect on the adsorption of Hg 2+ The adsorption capacity of Hg decreased gradually. When the addition amount of mesoporous silica and mercapto-modified mesoporous silica was 5 mg, the adsorption capacity was the largest. 2+ The adsorption capacity of mercapto-modified mesoporous silica for Hg 2+ The adsorption capacity can reach 180mg / g.

[0043] Test Example 2: Adsorption kinetics experiment

[0044] Preparation of 100 mg / L Hg 2+ solution, take 50 mL of the solution and add it into a conical flask, add 10 mg of SiO2 and the SiO2-SH material prepared in the example to the solution, oscillate at 180 r / min, take samples at 5 min, 10 min, 20 min, 30 min, 60 min, 120 min, 240 min, 360 min and 480 min, determine the adsorption capacity, and draw the adsorption kinetics curve.

[0045] The experimental results are as follows Figure 5 As shown, the mercapto-modified mesoporous silica has a 2+ It has a fast adsorption capacity and can reach adsorption equilibrium within 50 minutes, while mesoporous silica has a slow adsorption of mercury and poor adsorption capacity.

[0046] Test Example 3: Selective Experiment

[0047] Formulated to contain Hg 2+ 、Cd 2+ , Cu 2+ , Pb 2+ For each 10 mg / L mixed solution, take 8 mL of the solution and add it into a centrifuge tube. Add 5 mg of the SiO2-SH material prepared in the example into the solution and shake it at 180 r / min. After 6 h, measure the concentration of each ion in the solution and calculate the adsorption capacity.

[0048] The experimental results are as follows Figure 6 As shown, mesoporous silica in Hg 2+ 、Cd 2+ , Cu 2+ and Pb 2+ Under the coexistence conditions, Hg 2+ It has strong selectivity and exhibits specific adsorption properties.

[0049] The key to the present invention is to use hexadecyltrimethylammonium bromide surfactant as a template, synthesize mesoporous silica by hydrolysis of TEOS, and use a mixed solution of hydrochloric acid and ethanol to condense and reflux the template for multiple times. The prepared mesoporous silica is nano-scale, has a high specific surface area, and the solvent used in the preparation process is relatively safe. The present invention uses (3-mercaptopropyl)trimethoxysilane under mild conditions to mercaptolate the surface of mesoporous silica, and Hg in mercury-containing wastewater is removed. 2+ The adsorption capacity can reach 250 mg / g, with good selectivity.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0051] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing mercapto-modified mesoporous silica, characterized in that: The following steps are involved: Mesoporous silica was prepared by hydrolysis and condensation under alkaline conditions using surfactant as template and tetraethyl silicate as silicon source. (3-mercaptopropyl)trimethoxysilane is used to modify the prepared mesoporous silica with mercapto groups to obtain mercapto-modified mesoporous silica.

2. The method for preparing mercapto-modified mesoporous silica according to claim 1, characterized in that: The preparation method of mesoporous silica specifically includes the following sub-steps: (1) 200-300 mL of deionized water and 0.5-1.0 g of triethanolamine are uniformly mixed, and 3-5 g of hexadecyltrimethylammonium bromide are added, and the mixture is heated and stirred to completely dissolve the surfactant in the organic amine aqueous solution; (2) Weigh 30 g of tetraethyl silicate and quickly add it to the solution of (1), heating and stirring; (3) After the obtained product is centrifuged or filtered, it is repeatedly washed with ethanol and deionized water until it becomes neutral, thereby obtaining mesoporous silica with a template; (4) removing the template agent hexadecyltrimethylammonium bromide from the obtained product; (5) Wash with deionized water and ethanol until neutral, and vacuum dry to obtain a mesoporous silica product.

3. The method for preparing mercapto-modified mesoporous silica according to claim 2, characterized in that: In step (1), the oil bath is placed at 80.0-90.0° C. and stirred for 1-2 hours under a magnetic stirrer to completely dissolve the surfactant in the organic amine aqueous solution.

4. The method for preparing mercapto-modified mesoporous silica according to claim 2, characterized in that: In step (2), the mixture is placed in an oil bath at 80.0-90.0° C. and the magnetic stirrer is set at a speed of 1000-2000 rpm for stirring for 2-3 hours.

5. The method for preparing mercapto-modified mesoporous silica according to claim 2, characterized in that: The method of step (4) is specifically as follows: adding a 1M hydrochloric acid and ethanol 1:1 mixed solution to the obtained product, condensing and refluxing for 6 to 8 hours, filtering or centrifuging, repeating the operation multiple times to remove the template, and performing centrifugation or filtering.

6. The method for preparing mercapto-modified mesoporous silica according to claim 1, characterized in that: The method for preparing mercapto-modified mesoporous silica from mesoporous silica specifically comprises the following steps: Mesoporous silica is uniformly dispersed in an appropriate amount of ethanol solution, the pH is adjusted to 8-10, (3-mercaptopropyl)trimethoxysilane is dropped into the above mixture in a ratio of 1:1 in volume / mass to mesoporous silica and stirred continuously to prepare mercapto-modified mesoporous silica.

7. The method for preparing mercapto-modified mesoporous silica according to claim 6, characterized in that: After (3-mercaptopropyl)trimethoxysilane and mesoporous silica are mixed, they are continuously stirred, blown into vacuum with nitrogen, stirred vigorously at room temperature under nitrogen atmosphere, and the product is collected by centrifugation or filtration, repeatedly washed with ethanol and deionized water until neutral, and vacuum dried to obtain mercapto-modified mesoporous silica.

8. Mercapto-modified mesoporous silica prepared by the method according to any one of claims 1 to 7.

9. The mercapto-modified mesoporous silica according to claim 8 is used for Hg removal in wastewater 2+ Application in adsorption.

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