A functionally modified bentonite adsorbing material, and a preparation method and application thereof

Abstract

The application discloses a kind of functionally modified bentonite adsorption materials and its preparation method and application.The method is through gradient acid etching induced biomimetic mineralization process and microwave assisted pillar supporting treatment synergistic effect, selective dissolution of aluminum element in bentonite interlayer, construct similar diatomite Multistage pore structure;Subsequently, titanium-silicon composite pillar supporting agent is embedded in interlayer and pore under the action of microwave field, expand the interlayer spacing, while, construct nanoscale active site in pore inner surface, form the double adsorption channel of " micron through + nanometer enrichment ".The specific surface area of modified bentonite is increased to 230-280 m 2 / g, the interlayer spacing is expanded to 1.8-2.2 nm, and efficient adsorption performance is exhibited in gas adsorption (such as CO2, NH3) and liquid pollutant treatment (such as dye, heavy metal).

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental functional materials, and particularly relates to a functionalized modified bentonite adsorption material and a preparation method and application thereof. BACKGROUND

[0002] Bentonite is a layered silicate clay mineral with montmorillonite as the main component. Its unique sandwich structure (two layers of silicon oxygen tetrahedron sandwiching one layer of aluminum oxygen octahedron) endows it with good ion exchange property and water absorption performance. However, the interlayer domain of natural bentonite is mainly nanoscale microporous, and gas molecules are difficult to diffuse into it effectively. Its effective specific surface area is mainly concentrated on the inner surface, and the adsorption efficiency of gas pollutants is low. Diatomite is a biogenic siliceous sedimentary rock, and its main component is amorphous silicon dioxide (SiO2·nH2O). It naturally has a unique porous framework structure, including a large number of macropores (> 50 nm) and mesopores (2-50 nm), forming a developed pore system that is interconnected, providing a rapid diffusion channel for gas and liquid, and having excellent physical adsorption performance.

[0003] At present, the modification methods of bentonite mainly include acid modification, thermal activation and organic intercalation. These methods can improve the pore structure and adsorption performance of bentonite to some extent, but often have limitations: acid modification may damage the crystal structure, resulting in limited increase in specific surface area; thermal activation is easy to cause layer sintering and block the pore channel; although organic intercalation can expand the interlayer spacing, the introduction of organic matter may reduce the thermal stability and chemical stability of the material, and the selectivity of gas adsorption is limited. SUMMARY

[0004] In view of the above problems, the present application provides a functionalized modified bentonite adsorption material and a preparation method and application thereof. Through directional acid etching and pillar supporting modification, a micro-nano multi-level pore structure is constructed, so that it has a developed multi-level pore channel like diatomite and a high-activity inner surface of bentonite itself, realizing the synergistic and efficient adsorption of gas and liquid.

[0005] Specifically, the method comprises the following steps:

[0006] (1) Pre-treating the bentonite, crushing and removing impurities;

[0007] (2) gradient acid etching biomimetic mineralization treatment is performed on the pretreated bentonite to obtain a biomimetic mineralization intermediate; the gradient acid etching biomimetic mineralization treatment is: first, the pretreated bentonite is reacted with 0.5-1.5 mol / L low-concentration inorganic acid at 60-80 ℃ for 2-4 hours, then the acid concentration of the system is increased to 3-5 mol / L, and the reaction is continued at 80-95 ℃ for 4-8 hours; the gradient acid etching can selectively dissolve aluminum elements in the octahedral aluminum-oxygen octahedron in the layered structure of the bentonite, rather than completely corroding in disorder, and meanwhile, the silicon-oxygen tetrahedral framework is partially reserved, so that a porous and through framework structure similar to diatomite is reconstructed on the micron scale.

[0008] The present application realizes the selective dissolution of aluminum elements in the interlayer of the bentonite through the "gradient acid etching" process, which is mild at the beginning and gradually strengthened. This process successfully reconstructs the dense bentonite layered structure into a diatomite-like framework with a large number of micron-level through macropores and mesopores. This provides a "highway" for the rapid transmission of gas and liquid molecules, and solves the core problem of large diffusion resistance of natural bentonite.

[0009] (3) a titanium-silicon composite pillaring agent is prepared; the titanium-silicon composite pillaring agent is a titanium-silicon composite sol formed by hydrolysis of a titanium source and a silicon source under acidic conditions; specifically, a titanium source (such as tetrabutyl titanate or titanium tetrachloride) and a silicon source (such as tetraethyl orthosilicate or silica sol) are dissolved in an alcohol-water mixed solvent at a Ti:Si molar ratio of (1:4) to (1:1), and a clear and stable titanium-silicon composite sol is formed by hydrolysis and aging at room temperature under the action of an acidic catalyst such as nitric acid or hydrochloric acid, serving as a pillaring agent precursor.

[0010] (4) the biomimetic mineralization intermediate and the titanium-silicon composite pillaring agent are uniformly mixed, and then a pillaring reaction is performed under microwave conditions; after the reaction, solid-liquid separation, drying and calcination are performed to obtain the functionalized modified bentonite adsorbent material.

[0011] Further, the pretreatment method is: the natural bentonite ore is crushed and sieved to obtain bentonite powder, and then purification treatment is performed;

[0012] Generally, the purification treatment is: a wet purification process is used, the bentonite powder is configured into a suspension, a dispersing agent (such as sodium pyrophosphate) is added, and then the suspension is subjected to ultrasonic dispersion and natural sedimentation or centrifugal separation to remove impurity particles with a larger density such as quartz.

[0013] Further, the biomimetic mineralization intermediate is washed to neutral.

[0014] Further, the inorganic acid is one or more of hydrochloric acid, sulfuric acid and nitric acid.

[0015] Further, the molar ratio of the titanium source and the silicon source in step (3) is (1:4)~(1:1); the titanium source is tetrabutyl titanate or titanium tetrachloride, and the silicon source is tetraethyl orthosilicate or silica sol.

[0016] Further, the pillar supporting reaction condition in step (4) is that the microwave power is 300~600W, the reaction temperature is 80~100℃, and the reaction time is 1~3 hours. The unique heating effect (bulk heating, rapid and uniform) of the microwave field promotes the titanium-silicon composite pillar supporting agent (such as TiO 2- SiO 2- Nanocluster) to be efficiently and uniformly embedded into the surface of the interlayer domain and the new pore channel which have been expanded. This not only further expands the interlayer spacing to 1.8-2.2 nm, providing more nanospace, but more importantly, in-situ constructs nanoscale active sites composed of titanium and silicon oxides on the inner surface of the pore channel. These sites greatly enhance the chemical interaction of the material with specific pollutant molecules (such as adsorbing CO2, NH3 through Lewis acid-base interaction, or adsorbing heavy metals through coordination).

[0017] Further, the mass ratio of the titanium-silicon composite pillar supporting agent and the biomimetic mineralization intermediate in step (4) is (0.1:1)~(0.3:1).

[0018] Further, the calcination condition in step (4) is that the calcination is carried out in an air atmosphere at 350~450℃ for 2~4 hours.

[0019] The application also provides the functionalized modified bentonite adsorption material prepared by the above method.

[0020] The application also provides the application of the functionalized modified bentonite adsorption material in adsorbing gaseous pollutants or liquid pollutants.

[0021] The application has the advantages that the application organically combines “framework directional reconstruction” and “pore functionalized modification”, and creates unique “micron through + nanometer enrichment” dual adsorption channels. The micrometer-sized macroporous framework is responsible for the rapid transport of molecules, and the nanometer-sized expanded interlayer domain and active sites are responsible for the efficient capture and enrichment of molecules. The two are coordinated to realize the perfect combination of physical adsorption and chemical adsorption.

[0022] The specific surface area of the bentonite modified by the method of the application is greatly increased to 230-280 m 2 / g, and the interlayer spacing is expanded to 1.8-2.2 nm. The material shows significantly higher adsorption capacity and adsorption rate than natural bentonite and traditional modified bentonite for gaseous pollutants (such as CO2, NH3) and liquid pollutants (such as methyl orange, methylene blue and other dyes, Pb 2+ , Cd 2+ and other heavy metal ions). Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the functionalized bentonite adsorbent material of this application.

[0024] Figure 2 XRD patterns of natural bentonite and Example 1. Detailed Implementation

[0025] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0026] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0027] The embodiments of the present invention will be further described below with reference to several examples.

[0028] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0029] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0030] Example 1

[0031] 1. Pretreatment: The natural bentonite ore is crushed and sieved to obtain bentonite powder, which is then purified to remove impurities such as quartz.

[0032] 2. Gradient acid etching for biomimetic mineralization:

[0033] (1) The pretreated bentonite powder was mixed with 0.5 mol / L hydrochloric acid solution at a mass-volume ratio of 1 g: 30 mL and stirred at low speed at 80 °C for 2 hours.

[0034] (2) Subsequently, hydrochloric acid solution was added to increase the acid concentration of the system stepwise to 3 mol / L, and the reaction was intensified at 80°C for 4 hours.

[0035] (3) After the reaction is complete, cool, centrifuge, wash until neutral, and dry to obtain biomimetic mineralization intermediate.

[0036] 3. Preparation of titanium-silicon composite pillaring agent: Dissolve titanium source tetrabutyl titanate and silicon source tetraethyl orthosilicate in an alcohol-water mixed solvent mixed by volume ratio of 4:1 of anhydrous ethanol (or isopropanol) and deionized water, with Ti:Si molar ratio of 1:4, and add nitric acid to pH = 2-3, stir for 2 hours at room temperature, and then stand for aging for 12 hours to form a clear and stable titanium-silicon composite sol as a pillaring agent precursor.

[0037] 4. Microwave-assisted pillaring and channel modification:

[0038] (1) Disperse the biomimetic mineralization intermediate obtained in step 2 in deionized water to form a uniform suspension.

[0039] (2) Slowly add the titanium-silicon composite pillaring agent prepared in step 3 to the suspension under vigorous stirring, so that the mass ratio of the pillaring agent to the intermediate is 0.1:1.

[0040] (3) Transfer the mixed system to a microwave reactor and react at a microwave power of 300 W and a temperature of 100°C for 3 hours.

[0041] (4) After the reaction is completed, the product is filtered, washed, dried, and finally calcined at 450°C for 2 hours to obtain the final biomimetic mineralization and channel-modified bentonite adsorbent material.

[0042] The specific surface area of the obtained functionalized and modified bentonite adsorbent material is increased to 240 m 2 / g, and the interlayer spacing is expanded to 2 nm. As shown in Figure 2 , the characteristic peak of the (001) crystal plane of the functionalized and modified bentonite adsorbent material of this embodiment shifts to the left, which is because the crystal plane spacing is larger, and according to the Bragg equation 2dsinθ = λ, θ is correspondingly reduced, indicating that the interlayer spacing of the bentonite is larger.

[0043] Example 2

[0044] 1. Pretreatment: Crush and sieve the natural bentonite ore to obtain bentonite powder, and perform purification treatment to remove impurities such as quartz.

[0045] 2. Gradient acid etching biomimetic mineralization:

[0046] (1) Mix the pretreated bentonite powder with 1 mol / L sulfuric acid solution at a mass to volume ratio of 1 g: 10 mL, and stir at a low speed at 60°C for 4 hours.

[0047] (2) Then, add high-concentration inorganic acid to increase the acid concentration of the system in steps to 4 mol / L, and intensively stir at 95°C for 4 hours.

[0048] (3) After the reaction is completed, cool, centrifuge, wash to neutral, dry, to obtain the biomimetic mineralization intermediate.

[0049] In this step, gradient acid etching can selectively dissolve aluminum elements in the octahedral aluminum-oxygen octahedron in the layered structure of bentonite, while partially retaining the silicon-oxygen tetrahedral framework, thereby reconstructing a porous and through framework structure similar to diatomite on a micron scale.

[0050] 3. Preparation of titanium-silicon composite pillaring agent: Dissolve titanium source titanium tetrachloride and silicon source silica sol in alcohol-water mixed solvent with Ti: Si molar ratio of 1: 1, hydrolyze and age under the action of acidic catalyst hydrochloric acid at room temperature, form clear and stable titanium-silicon composite sol as a pillaring agent precursor.

[0051] 4. Microwave-assisted pillaring and pore modification:

[0052] (1) Disperse the biomimetic mineralization intermediate obtained in step 2 in deionized water to form a uniform suspension.

[0053] (2) Under vigorous stirring, slowly add the titanium-silicon composite pillaring agent prepared in step 3 to the suspension, so that the mass ratio of the pillaring agent to the intermediate is 0.3:1.

[0054] (3) Transfer the mixed system to a microwave reactor and react at a microwave power of 600 W and a temperature of 80°C for 1 hour.

[0055] (4) After the reaction is completed, the product is filtered, washed, dried, and finally calcined at 350°C for 2 hours to obtain the final biomimetic mineralization and pore-modified bentonite adsorbent material.

[0056] The obtained functionalized and modified bentonite adsorbent material has a specific surface area of 280 m 2 / g and an interlayer spacing of 2.2 nm.

[0057] Example 3

[0058] 1. Pretreatment: Crush and sieve the natural bentonite ore to obtain bentonite powder, and perform purification treatment to remove impurities such as quartz.

[0059] 2. Gradient acid etching biomimetic mineralization:

[0060] (1) Mix the pretreated bentonite powder with 1.5 mol / L nitric acid solution with a mass-volume ratio of 1g:10mL, and react at 60°C under low-speed stirring for 4 hours.

[0061] (2) Then, add high-concentration inorganic acid to increase the acid concentration of the system in steps to 5 mol / L, and intensively stir at 95°C for 4 hours.

[0062] (3) After the reaction, cool, centrifuge, wash to neutral, dry, get biomimetic mineralization intermediate.

[0063] In this step, gradient acid etching can selectively dissolve aluminum elements in the octahedral aluminum-oxygen octahedron in the layered structure of bentonite, while partially retaining the silicon-oxygen tetrahedral framework, thereby reconstructing a porous and through framework structure similar to diatomite on a micron scale.

[0064] 3. Preparation of titanium-silicon composite pillaring agent: Dissolve titanium source titanium tetrachloride and silicon source silica sol in alcohol-water mixed solvent with Ti:Si molar ratio of 1:1, hydrolyze and age under the action of acidic catalyst hydrochloric acid at room temperature, form clear and stable titanium-silicon composite sol as a pillaring agent precursor.

[0065] 4. Microwave-assisted pillaring and pore modification:

[0066] (1) Disperse the biomimetic mineralization intermediate obtained in step 2 in deionized water to form a uniform suspension.

[0067] (2) Under vigorous stirring, slowly add the titanium-silicon composite pillaring agent prepared in step 3 to the suspension, so that the mass ratio of pillaring agent to intermediate is 0.3:1.

[0068] (3) Transfer the mixed system to a microwave reactor and react at a microwave power of 500 W and a temperature of 80°C for 2 hours.

[0069] (4) After the reaction, the product is filtered, washed, dried, and finally calcined at 400°C for 4 hours to obtain the final biomimetic mineralization and pore-modified bentonite adsorbent material.

[0070] The specific surface area of the functionalized and modified bentonite adsorbent material is increased to 230 m 2 / g, and the interlayer spacing is expanded to 1.8 nm.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that 3 mol / L hydrochloric acid is directly used for acid etching in step 2.

[0073] Comparative Example 2

[0074] The difference from Example 1 is that no titanium-silicon composite pillaring agent is added.

[0075] Table 1: Comparison of bentonite properties before and after modification

[0076]

[0077] The above embodiments illustrate the structure, features and effects of the present application, and the above description is only the preferred embodiments of the present application. Any changes made in accordance with the concept of the present application, or equivalent embodiments with equivalent changes, shall be within the scope of the present application.

Claims

1. A method for preparing a functionalized bentonite adsorbent material, characterized in that, Includes the following steps: (1) Pretreatment of bentonite: crushing and removing impurities; (2) The pretreated bentonite is subjected to gradient acid etching biomimetic mineralization treatment to obtain a biomimetic mineralization intermediate; the gradient acid etching biomimetic mineralization treatment is as follows: the pretreated bentonite is reacted with a low concentration of inorganic acid of 0.5~1.5 mol / L at 60~80℃ for 2~4 hours, and then the acid concentration of the system is increased to 3~5 mol / L, and the reaction is continued at 80~95℃ for 4~8 hours; (3) Preparation of titanium-silicon composite pillaring agent; the titanium-silicon composite pillaring agent is a titanium-silicon composite sol formed by hydrolysis of titanium source and silicon source under acidic conditions; (4) After the biomimetic mineralization intermediate and the titanium-silicon composite pillaring agent are mixed evenly, the pillaring reaction is carried out under microwave conditions. After the reaction, the solid-liquid separation, drying and calcination are performed to obtain the functionalized bentonite adsorbent material. The conditions for the pillaring reaction are microwave power of 300~600W, reaction temperature of 80~100℃, and reaction time of 1~3 hours. The mass ratio of titanium-silicon composite pillaring agent to biomimetic mineralization intermediate is (0.1:1)~(0.3:1).

2. The method according to claim 1, characterized in that, The pretreatment method is as follows: crush and sieve the natural bentonite ore to obtain bentonite powder, and then purify it.

3. The method according to claim 1, characterized in that, The biomimetic mineralization intermediate was washed until neutral.

4. The method according to claim 1, characterized in that, The inorganic acid is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

5. The method according to claim 1, characterized in that, In step (3), the molar ratio of titanium source to silicon source is (1:4) to (1:1); the titanium source is tetrabutyl titanate or titanium tetrachloride, and the silicon source is tetraethyl orthosilicate or silica sol.

6. The method according to claim 1, characterized in that, The calcination conditions in step (4) are: calcination at 350~450℃ for 2~4 hours in an air atmosphere.

7. A functionalized bentonite adsorbent material prepared by the method of claim 1.

8. The application of a functionalized bentonite adsorbent material as described in claim 7 in the adsorption of gaseous or liquid pollutants.

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