Multifunctional nano composite aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sewage treatment, and particularly discloses multifunctional nano composite aerogel and a preparation method and application thereof in sewage treatment.The multifunctional nano composite aerogel is prepared through the following steps that a silicon source is hydrolyzed in a solvent, and uniform sol is generated; adding rare earth doped modified TiO2 into the sol, and coating modified Fe3O4; and adjusting the pH value of the sol into which the functional nanoparticles are introduced to 6-9, carrying out gelation, then carrying out aging, after the aging is finished, carrying out cleaning with deionized water, then carrying out replacement with ethanol for 2-5 times, and carrying out drying so as to obtain the multifunctional nano composite aerogel. According to the invention, the aerogel is subjected to composite modification by adopting rare earth doped TiO2 and coated modified Fe3O4, so that the problems of narrow photoresponse and easy oxidation of traditional particles are solved; through functional group design (amino and sulfydryl) and light response regulation and control, targeted removal of specific pollutants such as Hg2, Cr6 and rhodamine B is realized, and the blank of'broad-spectrum treatment but low efficiency 'in the prior art is filled.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to the development of wastewater treatment materials, specifically to a multifunctional nanocomposite aerogel, its preparation method, and its application in wastewater treatment. Background Technology

[0002] With the acceleration of global industrialization, water pollution has become increasingly severe, especially the discharge of heavy metal ions, organic dyes, and oil pollutants, which seriously threaten water resource security and the sustainability of the ecological environment. Common wastewater treatment methods include ion exchange, adsorption, chemical precipitation, membrane treatment, and electrochemical methods. Among these, traditional wastewater treatment methods, such as chemical precipitation, activated carbon adsorption, and membrane separation, while effective to some extent, suffer from low treatment efficiency, high cost, and secondary pollution. Adsorption is widely used due to its advantages of readily available materials, low cost, and simple operation. Adsorption mainly relies on the physicochemical interaction between the adsorbent and pollutants to remove pollutants from water bodies. Therefore, the key to this method lies in the selection of adsorbent materials. Considering both economy and effectiveness, montmorillonite, kaolin, biochar, and silicate minerals are currently widely used adsorbent materials. However, the adsorption effect of these materials is limited by factors such as adsorption capacity, specific surface area, and pore number. Therefore, new adsorbents with good adsorption performance, high stability, and easy recovery and regeneration are needed.

[0003] In recent years, aerogels, as porous materials with ultra-high specific surface area, low density, and high tunability, have been considered promising adsorbent materials. Their excellent pore structure and large specific surface area ensure good adsorption capacity. However, wastewater from different sources varies significantly in composition, and single aerogel adsorbents suffer from limited adsorption capacity and poor regeneration performance. To address these issues, researchers have made many attempts at aerogel composite modification; however, the following problems still exist: First, the introduced nanoparticles have weak bonding with the aerogel matrix and cannot be recycled. Second, it has a single function and cannot handle heavy metal ions, oils, and organic dyes. Third, composite aerogels lack specificity in treating pollutants and cannot target highly hazardous specific ions in wastewater (such as Hg). 2 ⁺、Cr 6 The inability to efficiently target and remove recalcitrant organic pollutants (such as Rhodamine B) limits its practical application scenarios.

[0004] Therefore, developing a reusable aerogel material suitable for practical applications, possessing multiple directional processing functions, can solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a multifunctional nanocomposite aerogel. This invention introduces rare-earth-doped TiO2 and coated modified Fe3O4 into the aerogel material, resulting in a composite material that achieves Hg... 2 ⁺、Cr 6 It can target and remove specific pollutants such as ⁺ and Rhodamine B, and still has a high adsorption retention rate after being reused 100 times.

[0006] This invention is achieved through the following technical solution: A method for preparing a multifunctional nanocomposite aerogel includes the following steps: (1) Preparation of sol: The silicon source is hydrolyzed in a solvent, and a uniform sol is generated under the action of hydrochloric acid or ammonia. (2) Introduction of functional nanoparticles: Rare earth doped modified TiO2 nanoparticles and coated modified Fe3O4 nanoparticles were added to the above sol and ultrasonically treated. (3) Gel formation, aging and drying: The pH of the sol with introduced functional nanoparticles is adjusted to 6-9, and after gel formation, it is aged and cleaned. Solvent replacement is used, and finally supercritical CO2 drying or freeze drying is used to obtain multifunctional nanocomposite aerogel.

[0007] A further improvement to the present invention is as follows: In step (1), the concentration of hydrochloric acid is 0.5-1 mol / L, and the concentration of ammonia is 1-2 mol / L; Furthermore, the silicon source is selected from tetramethoxysilane or tetraethoxysilane, and the concentration of the silicon source in the solvent is 1-5 mol / L; The solvent is selected from anhydrous ethanol, methanol, or isopropanol. Furthermore, the hydrolysis temperature is 25℃-60℃, and the time is 1-5h.

[0008] Furthermore, in step (2), the amount of rare earth-doped modified TiO2 nanoparticles is 1-5% of the mass of the silicon source; the amount of coated modified Fe3O4 nanoparticles is 1-5% of the mass of the silicon source. Furthermore, during the ultrasonic treatment, the ultrasonic power is 500-800W, the time is 2-3 hours, and the temperature is 60-70℃.

[0009] Further, in step (2), the rare earth-doped modified TiO2 nanoparticles are prepared by the following steps: weighing TiO2 nanoparticles with a particle size of 20-200 nm and ultrasonically dispersing them in an ethanol-water mixed solution to form a suspension; adding rare earth nitrates to the above suspension, stirring evenly, adjusting the pH to 7-8 with ammonia water, and stirring at a constant temperature of 60-80℃ for 3-5 h to obtain a doped TiO2 precursor; centrifuging the precursor, washing it with deionized water, and vacuum drying to obtain rare earth-doped modified TiO2 nanoparticles.

[0010] Furthermore, in the above-mentioned preparation of rare earth-doped modified TiO2 nanoparticles, the concentration of TiO2 nanoparticles in the suspension is 10-20 g / L; Furthermore, the rare earth nitrate is La(NO3)3・6H2O or Nd(NO3)3・6H2O, and the molar ratio of TiO2 to rare earth nitrate is 100:(1-5) based on the molar ratio of Ti to rare earth ions.

[0011] Further, in step (2), the coated modified Fe3O4 nanoparticles are prepared by the following steps: Fe3O4 nanoparticles with a particle size of 20-200 nm are ultrasonically dispersed in an ethanol-water mixture, and ammonia is added to adjust the pH to 9-10 to form a suspension; tetraethyl orthosilicate is added dropwise to the above suspension and stirred, and after the addition is completed, the reaction is carried out at 25-35℃ for 1-3 hours to form a SiO2 coating layer; the modifier is added, the temperature is raised to 40-60℃ and stirred for 2-4 hours to make the modifier grafted onto the SiO2 surface; after the reaction is completed, the nanoparticles are centrifuged, washed with ethanol, and vacuum dried to obtain the coated modified Fe3O4 nanoparticles.

[0012] Furthermore, in the preparation of the coated modified Fe3O4 nanoparticles described above, the concentration of Fe3O4 nanoparticles in the suspension is 30-50 g / L; Furthermore, the mass ratio of Fe3O4 nanoparticles to tetraethyl orthosilicate is 1:0.5-2; the volume ratio of tetraethyl orthosilicate to modifier is 10:1-3.

[0013] Furthermore, the modifier is 3-aminopropyltriethoxysilane or 3-mercaptopropyltriethoxysilane or a mixture of the two.

[0014] Furthermore, in step (3), the temperature for forming the gel is 25-60°C, and the time is 6-12 hours; Furthermore, the aging temperature is between 40-70℃, and the time is 12-48 hours; Furthermore, the supercritical CO2 drying process involves a pressure of 8-12 MPa, a temperature of 30-60°C, and a time of 6-24 h. Furthermore, the freeze-drying temperature is -40~-60℃, the pressure is 0.1-0.5mbar, and the time is 12-48h.

[0015] A further improvement of the present invention is as follows: This invention protects the multifunctional nanocomposite aerogel prepared by the above preparation method.

[0016] A further improvement to the present invention is as follows: Application of the multifunctional nanocomposite aerogel prepared by the above method in wastewater treatment.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention extends the photoresponse range of TiO2 from ultraviolet light (λ<387nm) to visible light (λ<550nm) by forming lattice defects through rare earth ion doping; it also directionally degrades azo dyes such as Rhodamine B and methyl orange through the visible light response characteristics of rare earth-doped TiO2; and it directionally retains antibiotics (such as tetracycline) through the multi-level porous structure of aerogel (microporous adsorption + mesoporous diffusion).

[0018] In this invention, the SiO2 coating layer can prevent Fe3O4 oxidation, and the amino group (-NH2) introduced by 3-aminopropyltriethoxysilane (APTES) can react with Hg. 2 ⁺ Forms coordinate bonds with Cr 6 ⁺ Electrostatic interactions are formed, enabling directional adsorption. The thiol groups introduced by 3-mercaptopropyltriethoxysilane (MPTS) directionally bind to Pb. 2 ⁺.

[0019] The modified Fe3O4 of this invention not only has magnetic separation function, but can also synergistically generate Fenton-like reaction with H2O2 under acidic conditions (pH 3-5) to generate hydroxyl radicals (・OH), which help degrade recalcitrant organic pollutants (such as persistent organophosphorus pesticides).

[0020] The present invention introduces rare earth doped TiO2, which can adjust the surface hydrophilicity and hydrophobicity through light irradiation to achieve directional separation of oil-water mixed wastewater (preferentially adsorbing the oil phase).

[0021] In summary, this invention proposes for the first time a composite modification scheme of rare earth-doped TiO2 and coated Fe3O4, solving the problems of narrow photoresponse and easy oxidation of traditional particles; it explores the Fenton-like catalytic function of Fe3O4 and the hydrophilicity-hydrophobicity regulation function of TiO2 to achieve a triple synergy of "adsorption-catalysis-separation"; and through functional group design (amino, thiol) and photoresponse regulation, it achieves the control of Hg 2 ⁺、Cr 6 The targeted removal of specific pollutants such as ⁺ and Rhodamine B fills the gap in existing technologies that offer "broad-spectrum treatment but low efficiency". Attached Figure Description

[0022] Figure 1 The image shows the microstructure of rare earth-doped modified TiO2 nanoparticles (La-TiO2) in Example 1. Figure 2 The image shows the microstructure of the Fe3O4 nanoparticles (Fe3O4@SiO2-APTES) coated in Example 1. Figure 3 The image shows the microstructure of the multifunctional nanocomposite aerogel prepared in Example 1. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments.

[0024] Example 1 (1) Preparation of silicon source sol 450g of tetramethoxysilane was dissolved in 1000mL of anhydrous ethanol, and the pH was adjusted to 3.5 with 0.6mol / L hydrochloric acid. The mixture was reacted at 45℃ for 2.5h to form a sol.

[0025] (2) Rare earth doped modified TiO2 nanoparticles 15g of TiO2 nanoparticles with a particle size of 100nm were weighed and placed in 1000mL of ethanol-water mixed solution (ethanol to water volume ratio of 1:1). The mixture was ultrasonically dispersed at 500W for 30min to form a suspension. 0.45g of La(NO3)3・6H2O was added to the suspension, and the mixture was stirred at 300r / min for 1h. The pH was adjusted to 7-8 with 1.5 mol / L ammonia water, and the mixture was stirred at 60-80℃ for 4h to obtain a doped TiO2 precursor. The precursor was centrifuged at 8000r / min for 10min, washed three times with deionized water, and vacuum dried at 60℃ for 12h to obtain rare earth-doped modified TiO2 nanoparticles, denoted as La-TiO2.

[0026] (3) Coated modified Fe3O4 nanoparticles 40g of Fe3O4 nanoparticles with a particle size of 100nm were weighed and dispersed in 1000mL of ethanol-water mixture (ethanol to water volume ratio of 4:1). After ultrasonic dispersion at 800W power for 1h, 3mol / L ammonia water was added to adjust the pH to 9-10 to form a suspension. 60g of tetraethyl orthosilicate (64mL) was added dropwise to the above suspension with stirring. After the addition was completed, the mixture was stirred at 30℃ for 2h to form a SiO2 coating layer, denoted as Fe3O4@SiO2. 6.5mL of 3-aminopropyltriethoxysilane was added, and the mixture was heated to 50℃ and stirred for 3h to graft the modifier onto the SiO2 surface. After the reaction was completed, the mixture was centrifuged at 10000r / min for 15min, washed three times with ethanol, and vacuum dried at 50℃ for 8h to obtain the coated modified Fe3O4 nanoparticles, denoted as Fe3O4@SiO2-APTS.

[0027] (4) Introduction of functional nanoparticles Add 13.5g of rare earth-doped modified TiO2 nanoparticles obtained in step (2) and 13.5g of coated modified Fe3O4 nanoparticles obtained in step (3) to the sol obtained in step (1), and ultrasonically treat it at 800W power and 70℃ for 2.5h.

[0028] (5) Gel formation, aging and drying The pH of the sol containing the introduced functional nanoparticles was adjusted to 6-9, and gelation was carried out at 45°C for 10 h, followed by aging at 65°C for 36 h. After aging, the sol was first washed with deionized water, then replaced with ethanol 4 times (3 h each time), and dried with supercritical CO2 (pressure 10 MPa, temperature 40°C, drying time 12 h) to obtain the final material, a multifunctional nanocomposite aerogel.

[0029] Example 2 In this embodiment, Nd(NO3)3·6H2O is used to replace La(NO3)3·6H2O in Example 1 for TiO2 nanoparticle doping modification; 3-mercaptopropyltriethoxysilane is used to replace 3-aminopropyltriethoxysilane in step (3); tetraethoxysilane is used to replace tetramethoxysilane in step (1); other operations are roughly the same as in Example 1, and will not be repeated here.

[0030] Example 3 In this embodiment, freeze drying (temperature -40℃, pressure 0.2mbar, drying time 24h) is used instead of supercritical CO2 drying in Example 1. Other operations are roughly the same as in Example 1, and will not be described again here.

[0031] Comparative Example 1 In this comparative example, conventional unmodified 100nm TiO2 nanoparticles and conventional unmodified 100nm Fe3O4 nanoparticles were used to replace the rare earth-doped modified TiO2 nanoparticles and coated modified Fe3O4 nanoparticles in Example 1. Other operations were largely the same as in Example 1, and will not be repeated here.

[0032] Comparative Example 2 In this comparative example, only rare earth-doped modified TiO2 nanoparticles were introduced into the sol, without adding coated modified Fe3O4 nanoparticles. Other operations were largely the same as in Example 1, and will not be repeated here.

[0033] Comparative Example 3 In this comparative example, only the coated modified Fe3O4 nanoparticles were introduced into the sol, without adding rare earth doped modified TiO2 nanoparticles. Other operations were largely the same as in Example 1, and will not be repeated here.

[0034] Comparative Example 4 In this comparative example, the TiO2 nanoparticles used have a particle size of 300 nm, and the Fe3O4 nanoparticles have a particle size of 500 nm. Other operations are roughly the same as in Example 1, and will not be repeated here.

[0035] Performance testing: Aerogels prepared using the examples and comparative examples were used to treat composite wastewater containing Hg. 2 ⁺ (1000 mg / L), Cr 6 ⁺ (1000 mg / L), Pb 2 ⁺ (1000 mg / L), Rhodamine B (1000 mg / L), Methyl parathion (10 mg / L), Diesel (10 wt%), Tetracycline (1000 mg / L); When investigating the degradation of Rhodamine B, the light conditions were visible light; When investigating the degradation of methyl parathion, 0.1 mol / L H₂O₂ was added, with the addition amount being 2% of the weight of the composite wastewater. The concentration or separation results of the pollutants after treatment are shown in the table below.

[0036] <![CDATA[Hg 2 ⁺(mg / L)]]> <![CDATA[Cr 6 ⁺(mg / L)]]> <![CDATA[Pb 2 ⁺(mg / L)]]> Rhodamine B (mg / L) Methyl parathion (mg / L) Tetracycline (mg / L) Oil-water separation efficiency (%) Can it be magnetically separated? Magnetic separation time (s) Adsorption retention rate (%) after 100 treatments Example 1 0.8 0.4 0.3 0.9 0.4 0.5 98.7 yes 25 92.5 Example 2 0.6 0.2 0.3 0.7 0.6 0.4 99.1 yes 29 94.3 Example 3 0.7 0.2 0.2 1.1 0.3 0.4 97.9 yes 27 95.6 Comparative Example 1 12.2 21.6 16.7 13.1 18.4 27.1 82.1 yes 45 76.3 Comparative Example 2 14.8 19.8 17.9 12.6 17.6 25.3 81.3 no / 75.3 Comparative Example 3 15.6 17.9 18.6 14.8 17.2 26.4 83.6 yes 78 72.6 Comparative Example 4 13.2 20.6 19.8 13.2 19.1 25.8 83.2 yes 66 75.4 As can be seen from the data in Examples 1-3, the multifunctional nanocomposite aerogel provided by the present invention has a photocatalytic degradation efficiency of over 99.8% for Rhodamine B under visible light; and a tetracycline rejection rate of over 99.9%.

[0037] By comparing the data from Comparative Example 1 and Example 1, it can be seen that the SiO2 coating layer can prevent Fe3O4 oxidation (the magnetic retention rate increased from 76.3% to 92.5% after 100 cycles of use), and the amino group (-NH2) introduced by 3-aminopropyltriethoxysilane (APTES) can react with Hg. 2 ⁺ Forms coordinate bonds with Cr6 ⁺ Electrostatic interaction is formed, achieving directional adsorption (Hg) 2 (⁺Removal rate increased from 98.5% to over 99.9%), and the mercapto groups introduced by 3-mercaptopropyltriethoxysilane (MPTS) directionally bind Pb. 2 ⁺.

[0038] Comparing the test results of Comparative Examples 1-2 with those of Examples 1-3, it can be seen that the modified Fe3O4 introduced into the composite aerogel of this invention not only possesses magnetic separation capabilities but also, under acidic conditions (pH 3-5), synergistically generates a Fenton-like reaction with H2O2 to produce hydroxyl radicals (・OH), thus assisting in the degradation of recalcitrant organic pollutants (such as persistent organophosphorus pesticides). The rare-earth-doped modified TiO2 introduced in this invention can have its surface hydrophilicity / hydrophobicity adjusted by light irradiation (the contact angle decreases from 85° to 30° after ultraviolet irradiation and recovers to 75° after visible light irradiation), achieving directional separation of oil-water mixed wastewater (preferentially adsorbing the oil phase).

[0039] Comparing the test results of Comparative Example 4 with those of Example 1, it can be seen that when the particle size of the SiO2 nanoparticles and Fe3O4 nanoparticles used increases, all the performances decrease significantly. This is because the particle size is too large, which reduces the number of reactive sites.

[0040] The above description of the embodiments is only for illustrating the technical concept and features of the present invention. Its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. Those skilled in the art can obviously easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the above embodiments should not be used to limit the scope of protection of the present invention. All improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional nanocomposite aerogel, characterized in that, Includes the following steps: (1) Preparation of sol: The silicon source is hydrolyzed in a solvent, and a uniform sol is generated under the action of hydrochloric acid or ammonia. (2) Introduction of functional nanoparticles: Rare earth doped modified TiO2 nanoparticles and coated modified Fe3O4 nanoparticles were added to the above sol and ultrasonically treated. (3) Gel formation, aging and drying: The pH of the sol with introduced functional nanoparticles is adjusted to 6-9, and after gel formation, it is aged and cleaned. Solvent replacement is used, and finally supercritical CO2 drying or freeze drying is used to obtain multifunctional nanocomposite aerogel.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of hydrochloric acid is 0.5-1 mol / L, and the concentration of ammonia is 1-2 mol / L; And / or, the silicon source is selected from tetramethoxysilane or tetraethoxysilane, and the concentration of the silicon source in the solvent is 1-5 mol / L; and / or, the solvent is selected from anhydrous ethanol, methanol or isopropanol; And / or, the hydrolysis temperature is 25℃-60℃, and the time is 1-5h.

3. The preparation method according to claim 1, characterized in that: In step (2), the amount of rare earth-doped modified TiO2 nanoparticles is 1-5% of the mass of the silicon source; the amount of coated modified Fe3O4 nanoparticles is 1-5% of the mass of the silicon source. And / or, during the ultrasonic treatment, the ultrasonic power is 500-800W, the time is 2-3h, and the temperature is 60-70℃.

4. The preparation method according to claim 1, characterized in that: In step (2), the rare earth-doped modified TiO2 nanoparticles are prepared by the following steps: weighing TiO2 nanoparticles with a particle size of 20-200 nm and ultrasonically dispersing them in an ethanol-water mixed solution to form a suspension; adding rare earth nitrates to the above suspension, stirring evenly, adjusting the pH to 7-8 with ammonia water, and stirring at a constant temperature of 60-80℃ for 3-5 h to obtain the doped TiO2 precursor; centrifuging the precursor, washing it with deionized water, and vacuum drying to obtain rare earth-doped modified TiO2 nanoparticles.

5. The preparation method according to claim 4, characterized in that: The concentration of TiO2 nanoparticles in the suspension is 10-20 g / L; And / or, the rare earth nitrate is La(NO3)3・6H2O or Nd(NO3)3・6H2O, and the molar ratio of TiO2 to rare earth nitrate is 100:(1-5) based on the molar ratio of Ti to rare earth ions.

6. The preparation method according to claim 1, characterized in that: In step (2), the coated modified Fe3O4 nanoparticles are prepared by the following steps: Fe3O4 nanoparticles with a particle size of 20-200 nm are ultrasonically dispersed in an ethanol-water mixture, and ammonia is added to adjust the pH to 9-10 to form a suspension; tetraethyl orthosilicate is added dropwise to the above suspension and stirred, and after the addition is completed, the reaction is carried out at 25-35℃ for 1-3 hours to form a SiO2 coating layer; the modifier is added, the temperature is raised to 40-60℃ and stirred for 2-4 hours to graft the modifier onto the SiO2 surface; after the reaction is completed, the nanoparticles are centrifuged, washed with ethanol, and vacuum dried to obtain the coated modified Fe3O4 nanoparticles.

7. The preparation method according to claim 6, characterized in that: The concentration of Fe3O4 nanoparticles in the suspension is 30-50 g / L; And / or, the mass ratio of the Fe3O4 nanoparticles to tetraethyl orthosilicate is 1:0.5-2; the volume ratio of the tetraethyl orthosilicate to the modifier is 10:1-3; And / or, the modifier is 3-aminopropyltriethoxysilane or 3-mercaptopropyltriethoxysilane or a mixture thereof.

8. The preparation method according to claim 1, characterized in that: The gel is formed at a temperature of 25-60℃ for 6-12 hours. And / or, the aging temperature is between 40-70°C and the time is 12-48 hours; And / or, the supercritical CO2 drying is performed at a pressure of 8-12 MPa, a temperature of 30-60°C, and a time of 6-24 h; And / or, the freeze-drying temperature is -40~-60℃, the pressure is 0.1-0.5mbar, and the time is 12-48h.

9. The multifunctional nanocomposite aerogel prepared by the preparation method according to any one of claims 1-8.

10. The application of the multifunctional nanocomposite aerogel as described in claim 9 in wastewater treatment.

Images