Preparation process of surface-modified porous titanium dioxide and application thereof

Abstract

The application relates to the technical field of titanium dioxide, and discloses a preparation process of surface-modified porous titanium dioxide and application thereof. The porous titanium dioxide has a large number of pore structures, a large specific surface area, and many adsorption sites, and is grafted with a hydroxyl-containing histidine-based polyamide containing a salicylaldehyde Schiff base structure, an imidazole structure and a polyamide structure, can have a strong coordination with Pb 2+ , Hg 2+ , and thus has excellent adsorption performance. 3,3'-diamino-benzidine is used as a polymerization monomer, the benzidine structure has heat resistance, the benzidine structure is introduced into the main chain of the polyamide after polymerization, the polyamide has excellent high-temperature resistance, the polyamide molecular chain does not pyrolyze at high temperature, the surface-modified porous titanium dioxide adsorbent still has high adsorption efficiency, and the surface-modified porous titanium dioxide adsorbent can meet the actual application of the adsorbent in the treatment of wastewater in a complex system such as high temperature.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide technology, specifically to a preparation process and application of surface-modified porous titanium dioxide. Background Technology

[0002] Nano-titanium dioxide is prepared by various methods, has a wide range of sources, and is green and pollution-free. It can be used as a photocatalyst, adsorbent, and antibacterial material, and has wide applications in wastewater treatment, photocatalytic degradation, and electrochemical energy. Porous nano-titanium dioxide has a large number of pores, a higher specific surface area, and good adsorption performance, showing broad application prospects in wastewater treatment. Patent CN102838162B prepared porous hollow titanium dioxide spheres, which have excellent adsorption performance for chromium ions. However, the adsorption capacity of titanium dioxide alone for metal ions such as lead and mercury is very limited. Introducing functional organic matter or polymers onto the surface of titanium dioxide can exert a synergistic adsorption effect. Patent CN111701575B discloses the preparation of mesoporous titanium dioxide coated with amino-modified natural polysaccharides using tetrabutyl titanate, natural polysaccharides, epichlorohydrin, etc., as raw materials, which can be used as a bilirubin adsorbent. However, traditional polymer-based adsorbents have poor high-temperature resistance and are prone to decomposition at high temperatures, which is not conducive to practical applications in high-temperature wastewater treatment. Summary of the Invention

[0003] Technical problem solved: A preparation process and application of surface-modified porous titanium dioxide are provided, which solves the problem of low removal rate of metal ions in wastewater by single nano-titanium dioxide.

[0004] Technical solution:

[0005] A process for preparing surface-modified porous titanium dioxide includes the following steps:

[0006] Step S1: Add histidine diacid monomer and 3,3'-diaminobenzidine to the reactor, introduce nitrogen gas, first heat to 200-210℃, control the pressure inside the reactor at 0.2-0.35MPa, and react for 2-3 hours; then heat to 225-250℃, control the pressure inside the reactor at 0.1-0.15MPa, and react for 2-3 hours. Cool and discharge the product, add it to molten pyridine hydrochloride to carry out the demethylation reaction, cool, add boiling water to precipitate, filter, wash with boiling water and ethanol to obtain hydroxyl-histidine-containing polyamide;

[0007] The reaction mechanism is as follows:

[0008]

[0009] Step S2: Surface modification of porous titanium dioxide is carried out using toluene diisocyanate to obtain isocyanate-modified porous titanium dioxide, which is then dispersed in N,N-dimethylformamide, and hydroxyhistidine-containing polyamide is added. Grafting reaction is carried out in a nitrogen atmosphere, filtered, washed with water and ethanol, and dried to obtain surface-modified porous titanium dioxide.

[0010] Furthermore, in step S1, the ratio of histidine dicarboxylic acid monomer to 3,3'-diaminobenzidine is (1.5-1.8) mol: 1 mol.

[0011] Furthermore, the temperature of the demethylation reaction in step S1 is 210-220℃, and the reaction time is 12-24h.

[0012] Furthermore, in step S2, the ratio of isocyanate-modified porous titanium dioxide to hydroxyhistidine-containing polyamide is 1g:(0.5-10)g.

[0013] Furthermore, in step S2, the grafting reaction temperature is 70-90℃ and the reaction time is 6-12h.

[0014] Furthermore, the preparation process of histidine diacid monomer includes the following steps: D,L-histidine and 2,5-dimethoxy-1,4-benzenedialdehyde are added to any one of the reaction solvents: ethanol, isopropanol, 1,4-dioxane, or tetrahydrofuran. Glacial acetic acid is added dropwise to initiate the reaction. During the reaction, the mixture is refluxed, concentrated to remove the solvent, and ethyl acetate and water are added. The mixture is shaken and allowed to stand for layering. The ethyl acetate organic layer is extracted and separated. The solvent is concentrated, and the product is recrystallized in ethanol to obtain the histidine diacid monomer. The reaction route is as follows:

[0015]

[0016] Furthermore, the ratio of D,L-histidine to 2,5-dimethoxy-1,4-benzaldehyde is (1.9-2.2) mol: 1 mol.

[0017] Furthermore, the reaction temperature is 65-100℃, and the reaction time is 3-8 hours.

[0018] Furthermore, the application of surface-modified porous titanium dioxide in water pollution control.

[0019] The technical effects are as follows: This invention utilizes D,L-histidine and 2,5-dimethoxy-1,4-benzaldehyde to react and obtain a histidine diacid monomer. Using 3,3'-diaminobenzidine as a tetraamino monomer, an amidation crosslinking polymerization reaction is carried out, followed by a demethylation reaction to obtain a hydroxyl-histidine-containing polyamide. This polyamide has a spatial crosslinking network structure, a larger specific surface area, more adsorption sites, and better adsorption performance. Finally, some of the hydroxyl groups in the hydroxyl-histidine-containing polyamide react with the isocyanate groups on the surface of isocyanate-modified nano-titanium dioxide to obtain surface-modified porous titanium dioxide.

[0020] The porous titanium dioxide of this invention has a large number of pores, a large specific surface area, and many adsorption sites. Simultaneously, the grafted hydroxyhistidine-containing polyamide contains salicylaldehyde Schiff base, imidazole, and polyamide structures, which can bind with Pb. 2+ Hg 2 + It exhibits strong coordination, thus demonstrating excellent adsorption performance.

[0021] This invention uses 3,3'-diaminobenzidine as the polymerization monomer, which contains a heat-resistant biphenyl structure. After polymerization, the biphenyl structure is introduced into the main chain of the polyamide, reflecting the excellent high-temperature resistance of the polyamide. At high temperatures, the polyamide molecular chain does not undergo pyrolysis, allowing the surface-modified porous titanium dioxide adsorbent to maintain high adsorption efficiency and metal ion removal effect. This can meet the practical application requirements of adsorbents in wastewater treatment in complex systems such as high-temperature environments. Attached Figure Description

[0022] Figure 1 It is Pb 2+ Removal rate curve.

[0023] Figure 2 It is Hg 2+ Removal rate curve.

[0024] Figure 3 Pb at high temperature 2+ Removal rate curve. Detailed Implementation

[0025] The present invention will be further described below with reference to the embodiments. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] 2 mL of tetrabutyl titanate was added dropwise to 10 mL of ethanol and dispersed evenly. The solution was then added dropwise to 50 mL of distilled water and stirred for 30 min to hydrolyze the mixture. The hydrolysis product was washed with ethanol and then transferred to a hydrothermal reactor. 70 mL of ethanol and 1 g of ammonium bicarbonate were added, and the mixture was heated to 180 °C and reacted for 48 h. After cooling, the mixture was filtered and washed with water and ethanol to obtain nanoporous titanium dioxide.

[0027] 0.5 g of nanoporous titanium dioxide was dispersed in toluene, and 1.8 g of toluene diisocyanate was added. The mixture was reacted at 90 °C for 12 h, filtered, washed with acetone, and dried to obtain isocyanate-modified nano titanium dioxide.

[0028] Example 1

[0029] Add 57 mmol of histidine and 30 mmol of 2,5-dimethoxy-1,4-benzaldehyde to 200 mL of isopropanol solvent, add 0.6 mL of glacial acetic acid dropwise, heat to 82 °C, and react for 8 h. During the reaction, reflux the solution and concentrate to remove the solvent. Add ethyl acetate and water, shake and allow to stand to separate the layers. Extract and separate the ethyl acetate organic layer, concentrate the solvent, and recrystallize the product in ethanol to obtain histidine diacid monomer.

[0030] 82 mmol of histidine diacid monomer and 50 mmol of 3,3'-diaminobenzidine were added to a reaction vessel, nitrogen gas was introduced, the temperature was first raised to 200℃, the pressure inside the reaction vessel was controlled at 0.3 MPa, and the reaction was carried out for 3 h; then the temperature was raised to 250℃, the pressure inside the reaction vessel was controlled at 0.15 MPa, and the reaction was carried out for 2 h. After cooling, the product was added to molten pyridine hydrochloride, the temperature was raised to 210℃, and the demethylation reaction was carried out for 24 h. After cooling, boiling water was added to precipitate, filtered, and washed with boiling water and ethanol to obtain hydroxyhistidine-containing polyamide.

[0031] 0.5 g of isocyanate-modified porous titanium dioxide was dispersed in 30 mL of N,N-dimethylformamide, and 0.25 g of hydroxyhistidine-containing polyamide was added. The mixture was heated to 70 °C under nitrogen atmosphere and subjected to a grafting reaction for 6 h. After filtration, the mixture was washed with water and ethanol and dried to obtain surface-modified porous titanium dioxide.

[0032] Example 2

[0033] Add 66 mmol of histidine and 30 mmol of 2,5-dimethoxy-1,4-benzaldehyde to 300 mL of ethanol solvent, add 0.5 mL of glacial acetic acid dropwise, heat to 75 °C, and react for 4 h. During the reaction, reflux the solution, concentrate to remove the solvent, add ethyl acetate and water, shake and allow to stand to separate the layers, extract and separate the ethyl acetate organic layer, concentrate the solvent, and recrystallize the product in ethanol to obtain histidine diacid monomer.

[0034] 75 mmol of histidine diacid monomer and 50 mmol of 3,3'-diaminobenzidine were added to a reactor, nitrogen gas was introduced, the temperature was first raised to 200℃, the pressure inside the reactor was controlled at 0.35 MPa, and the reaction was carried out for 2 h; then the temperature was raised to 250℃, the pressure inside the reactor was controlled at 0.1 MPa, and the reaction was carried out for 2 h. After cooling, the product was discharged and added to molten pyridine hydrochloride. The temperature was raised to 220℃ and a demethylation reaction was carried out for 18 h. After cooling, boiling water was added to precipitate the product, which was then filtered and washed with boiling water and ethanol to obtain a hydroxyhistidine-containing polyamide.

[0035] 0.5 g of isocyanate-modified porous titanium dioxide was dispersed in 80 mL of N,N-dimethylformamide, and 3 g of hydroxyhistidine-containing polyamide was added. The mixture was heated to 90 °C under nitrogen atmosphere and subjected to a grafting reaction for 12 h. The mixture was then filtered, washed with water and ethanol, and dried to obtain surface-modified porous titanium dioxide.

[0036] Example 3

[0037] Add 66 mmol of histidine and 30 mmol of 2,5-dimethoxy-1,4-benzaldehyde to 300 mL of 1,4-dioxane solvent, add 0.8 mL of glacial acetic acid dropwise, heat to 100 °C, and react for 3 h. During the reaction, reflux the solution and concentrate to remove the solvent. Add ethyl acetate and water, shake and allow to stand to separate the layers. Extract and separate the ethyl acetate organic layer, concentrate the solvent, and recrystallize the product in ethanol to obtain the histidine diacid monomer.

[0038] 90 mmol of histidine diacid monomer and 50 mmol of 3,3'-diaminobenzidine were added to a reaction vessel, nitrogen gas was introduced, the temperature was first raised to 210 °C, the pressure inside the reaction vessel was controlled at 0.2 MPa, and the reaction was carried out for 3 h; then the temperature was raised to 225 °C, the pressure inside the reaction vessel was controlled at 0.15 MPa, and the reaction was carried out for 3 h. After cooling, the product was discharged, and the product was added to molten pyridine hydrochloride, the temperature was raised to 220 °C, and the demethylation reaction was carried out for 12 h. After cooling, boiling water was added to precipitate, filtered, and washed with boiling water and ethanol to obtain hydroxyhistidine-containing polyamide.

[0039] 0.5 g of isocyanate-modified porous titanium dioxide was dispersed in 100 mL of N,N-dimethylformamide, and 5 g of hydroxyhistidine-containing polyamide was added. The grafting reaction was carried out at 90 °C for 12 h under nitrogen atmosphere. The mixture was filtered, washed with water and ethanol, and dried to obtain surface-modified porous titanium dioxide.

[0040] Comparative Example 1 is nanoporous titanium dioxide.

[0041] Comparative Example 2

[0042] 82 mmol of histidine diacid monomer and 50 mmol of ethylenediamine were added to a reactor, nitrogen gas was introduced, the temperature was first raised to 200°C, the pressure inside the reactor was controlled at 0.3 MPa, and the reaction was carried out for 3 h; then the temperature was raised to 250°C, the pressure inside the reactor was controlled at 0.15 MPa, and the reaction was carried out for 2 h. The product was cooled and discharged, and added to molten pyridine hydrochloride. The temperature was raised to 210°C and a demethylation reaction was carried out for 24 h. After cooling, boiling water was added to precipitate, filtered, and washed with boiling water and ethanol to obtain hydroxyhistidine-containing polyamide.

[0043] 0.5 g of isocyanate-modified porous titanium dioxide was dispersed in 30 mL of N,N-dimethylformamide, and 0.25 g of hydroxyhistidine-containing polyamide was added. The mixture was heated to 70 °C under nitrogen atmosphere and subjected to a grafting reaction for 6 h. After filtration, the mixture was washed with water and ethanol and dried to obtain surface-modified porous titanium dioxide.

[0044] Comparative Example 3 is a hydroxyhistidine-containing polyamide (prepared using the same process as in Example 1).

[0045] The surface-modified porous titanium dioxide prepared in Examples 1-3, the nanoporous titanium dioxide of Comparative Example 1, the surface-modified porous titanium dioxide of Comparative Example 2, and the hydroxyhistidine-containing polyamide of Comparative Example 3 were used as adsorbents to conduct water pollution treatment and metal ion adsorption simulation experiments.

[0046] Metal ion adsorption simulation experiment: Prepare 200 mL of Pb with a concentration of 50 mg / L. 2+ A standard aqueous solution was prepared with 200 mg of adsorbent, and adsorption was carried out by stirring at 25 °C. The supernatant was collected every 30 minutes, and Pb was determined by atomic absorption spectrophotometry. 2+ Concentration, calculate the removal rate Q, Q = (C0 - C1) / C0 × 100%. C0 is Pb. 2+ The initial concentration of the standard aqueous solution, C1 is the Pb after adsorption. 2+ Concentration of standard aqueous solution.

[0047] Prepare 200 mL of Hg solution with a concentration of 50 mg / L. 2+ A standard aqueous solution was prepared, and 300 mg of adsorbent was added. Adsorption was carried out by stirring at 25 °C. Every 30 min, the supernatant was collected, and Hg was determined by atomic absorption spectrophotometry. 2+ Concentration, calculate the removal rate Q, Q = (C0 - C1) / C0 × 100%. C0 is Pb. 2+ The initial concentration of the standard aqueous solution, C1 is the Hg after adsorption. 2+ Concentration of standard aqueous solution.

[0048] Instruction manual attached Figure 1 and Figure 2The results show that the surface-modified porous titanium dioxide in Examples 1-3, at 25°C and with an adsorption time of 180 min, effectively adsorbs Pb. 2+ The removal rate reached 86.3-99.4%, and the removal rate of Hg was achieved at an adsorption time of 210 min. 2+ The removal rate reached 84.2-97.8%, demonstrating excellent adsorption performance. This is because porous titanium dioxide has a large number of pores, a large specific surface area, and many adsorption sites. Simultaneously, the grafted hydroxyhistidine-containing polyamide contains salicylaldehyde Schiff base, imidazole, and polyamide structures, which can bind with Pb. 2+ Hg 2+ It exhibits strong coordination, and the hydroxyhistidine-containing polyamide is formed by the cross-linking polymerization reaction of histidine diacid monomer and 3,3'-diaminobenzidine tetraamino monomer, generating a spatial cross-linked network structure with a larger specific surface area and more adsorption sites, thus showing excellent adsorption performance and promising application prospects in the treatment of wastewater containing heavy metals.

[0049] Comparative Example 1 consisted solely of nanoporous titanium dioxide, without grafting of hydroxyhistidine-containing polyamide, and was similar to Pb. 2+ Hg 2+ The coordination is poor, resulting in low adsorption performance. At an adsorption time of 180 min, the adsorption of Pb... 2+ The removal rate was only 41.4%, and the adsorption time was 210 min for Hg. 2+ The removal rate was only 38.7%.

[0050] Comparative Example 2 used ethylenediamine as the diamine monomer to replace the 3,3'-diaminobenzidine tetraamino monomer and histidine diacid monomer in the polymerization reaction. Linear polymerization could occur between them, but spatial cross-linking was not possible, resulting in a low specific surface area, few adsorption sites, and poor adsorption performance for Pb. 2+ The removal rate was only 73.1%, and for Hg... 2+ The removal rate was only 66.0%.

[0051] Comparative Example 3 was a hydroxyhistidine-containing polyamide that did not undergo a grafting reaction with nanoporous titanium dioxide, thus failing to leverage the adsorption advantages of porous titanium dioxide for Pb. 2+ The removal rate was only 70.2%, and for Hg 2+ The removal rate was only 62.1%.

[0052] High-temperature metal ion adsorption simulation experiment: Prepare 200 mL of Pb with a concentration of 50 mg / L. 2+ A standard aqueous solution was prepared with 200 mg of adsorbent, and adsorption was carried out by stirring at 80 °C. The supernatant was collected every 30 minutes, and Pb was determined by atomic absorption spectrophotometry. 2+Concentration, calculate the removal rate Q, Q = (C0 - C1) / C0 × 100%. C0 is Pb. 2+ The initial concentration of the standard aqueous solution, C1 is the Pb after adsorption. 2+ Concentration of standard aqueous solution.

[0053] manual Figure 3 The results show that the surface-modified porous titanium dioxide in Examples 1-3, when adsorbed at 80°C for 180 min, effectively adsorbed Pb. 2+ The removal rate still reaches 85.1-98.6%. This is because 3,3'-diaminobenzidine is used as the polymerization monomer, which contains a heat-resistant biphenyl structure. After polymerization, the biphenyl structure is introduced into the main chain of the polyamide, reflecting the excellent high-temperature resistance of the polyamide. At high temperatures, the polyamide molecular chain will not undergo pyrolysis, allowing the surface-modified porous titanium dioxide adsorbent to maintain a high adsorption efficiency and metal ion removal effect. This can meet the practical application requirements of adsorbents in wastewater treatment in complex systems such as high-temperature environments.

[0054] Comparative Example 2 used ethylenediamine as the diamine monomer to replace 3,3'-diaminobenzidine in the polymerization reaction with histidine diacid monomer. The polyamide lacked the heat-resistant biphenyl structure, resulting in poor high-temperature resistance. At high temperatures, the polyamide molecular chains were prone to pyrolysis, leading to a significant decrease in the adsorption performance of the adsorbent, particularly for Pb. 2+ The removal rate was only 43.1%.

[0055] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing surface-modified porous titanium dioxide, characterized in that, The preparation method includes the following steps: Step S1: Add histidine diacid monomer and 3,3'-diaminobenzidine to the reactor, introduce nitrogen gas, first heat to 200-210℃, control the pressure inside the reactor at 0.2-0.35MPa, and react for 2-3 hours; then heat to 225-250℃, control the pressure inside the reactor at 0.1-0.15MPa, and react for 2-3 hours. Cool and discharge the product, add it to molten pyridine hydrochloride to carry out the demethylation reaction, cool, add boiling water to precipitate, filter, wash with boiling water and ethanol to obtain hydroxyl-histidine-containing polyamide; The structural formula of the histidine diacid monomer is: ; Step S2: Surface modification of porous titanium dioxide is carried out using toluene diisocyanate to obtain isocyanate-modified porous titanium dioxide, which is then dispersed in N,N-dimethylformamide, and hydroxyhistidine-containing polyamide is added. Grafting reaction is carried out in nitrogen atmosphere, filtered, washed with water and ethanol, and dried to obtain surface-modified porous titanium dioxide. The preparation method of the histidine diacid monomer includes the following steps: adding D,L-histidine and 2,5-dimethoxy-1,4-benzaldehyde to the reaction solvent, adding glacial acetic acid dropwise, reacting, concentrating to remove the solvent, adding ethyl acetate and water, shaking and allowing to stand to separate the layers, extracting and separating the ethyl acetate organic layer, concentrating the solvent, recrystallizing the product in ethanol to obtain the histidine diacid monomer.

2. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, In step S1, the ratio of histidine dicarboxylic acid monomer to 3,3'-diaminobenzidine is (1.5-1.8) mol: 1 mol.

3. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, The demethylation reaction in step S1 is carried out at a temperature of 210-220℃ for 12-24 hours.

4. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, In step S2, the ratio of isocyanate-modified porous titanium dioxide to hydroxyhistidine-containing polyamide is 1g:(0.5-10)g.

5. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, The grafting reaction in step S2 is carried out at a temperature of 70-90℃ for 6-12 hours.

6. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, When preparing histidine diacid monomers, the reaction solvents include ethanol, isopropanol, 1,4-dioxane, and tetrahydrofuran.

7. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, The ratio of D,L-histidine to 2,5-dimethoxy-1,4-benzaldehyde is (1.9-2.2) mol:1 mol.

8. The method for preparing surface-modified porous titanium dioxide according to claim 1, characterized in that, When preparing histidine dicarboxylic acid monomer, the reaction temperature is 65-100℃ and the reaction time is 3-8h.

9. The application of surface-modified porous titanium dioxide prepared by the preparation method according to any one of claims 1-8 in water pollution control.

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