Modified molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sewage treatment, and particularly discloses a modified molecular sieve as well as a preparation method and application thereof. According to the preparation method, a modified molecular sieve is prepared through a zirconium-doped silicon-aluminum molecular sieve and multi-group grafting, and the ion exchange capacity of a silicon-aluminum zeolite framework to heavy metals such as Pb and Cd is synergistically enhanced through zirconium doping and pore channel construction of the modified molecular sieve. Meanwhile, sulfydryl and amino are introduced through grafting modification, so that the adsorption capacity of the material to Hg and As is improved; besides, a titanium oxide group is introduced through grafting modification, the group can generate hydroxyl free radicals and superoxide anions under the illumination condition, adsorbed organic pollutants are decomposed through photocatalysis, the self-cleaning effect is achieved, pore channel blockage is avoided, and therefore the service cycle of the material is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and specifically discloses a modified molecular sieve, a preparation method and an application thereof. Background Art

[0002] Desulfurization wastewater, rich in heavy metal ions such as Pb, Cd, Hg, and As, as well as suspended solids, poses a serious threat to the ecological environment and human health if discharged directly without effective treatment. Traditional desulfurization wastewater treatment technologies, which often rely on chemical precipitation or ion exchange, suffer from low treatment efficiency, high reagent consumption, and the potential for secondary pollution. Consequently, optimizing desulfurization wastewater treatment technologies has become a hot research topic in wastewater treatment technology.

[0003] In the prior art, molecular sieves are often used to adsorb heavy metal ions and suspended solids. For example, prior art reports have reported the application of molecular sieves in desulfurization wastewater treatment systems to initially remove heavy metal ions and suspended solids from desulfurization wastewater. However, these prior art molecular sieves are poorly effective at removing heavy metal ions and suspended solids and are prone to clogging. Therefore, developing a molecular sieve that effectively removes heavy metal ions and suspended solids and is resistant to clogging is of great practical significance for wastewater treatment. Summary of the Invention

[0004] In order to solve the problem that molecular sieves in the prior art have poor removal effects on heavy metal ions and suspended solids and are prone to clogging, the present invention provides a modified molecular sieve, its preparation method, and application. The present invention prepares a porous molecular sieve by synthesizing a Zr-doped aluminosilicate molecular sieve and grafting functional groups on the molecular sieve surface. This porous molecular sieve synergistically enhances the ion exchange capacity of the aluminosilicate zeolite framework for heavy metals such as Pb and Cd through zirconium doping and pore construction; at the same time, the present invention introduces thiol and amino groups through grafting modification to increase the material's adsorption capacity for Hg and As; in addition, the present invention introduces titanium oxide groups through grafting modification. This group can generate hydroxyl radicals and superoxide anions under light conditions, decomposing adsorbed organic pollutants through photocatalysis, achieving a self-cleaning effect, avoiding pore clogging, and thus extending the material's service life.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing a modified molecular sieve, comprising the following steps:

[0007] S1. Mixing ethyl orthosilicate, aluminum isopropoxide, anhydrous ethanol and water to obtain a silica-alumina sol;

[0008] S2, mixing zirconium oxychloride with water, and adding the mixture to the silica-alumina sol to obtain a mixed sol;

[0009] S3, mixing the mixed sol with a tetrapropylammonium hydroxide aqueous solution, adjusting the pH to 9-11, performing a crystallization reaction at 120° C.-180° C., and calcining to remove the template to obtain a primary molecular sieve;

[0010] S4, mixing the primary molecular sieve, anhydrous ethanol, 3-mercaptopropyltrimethoxysilane and aminopropyltriethoxysilane, and performing a grafting reaction to obtain a primary grafted modified molecular sieve;

[0011] S5. Mixing the primary grafted modified molecular sieve, anhydrous ethanol, tetrabutyl titanate and aminopropyltriethoxysilane, and performing a grafting reaction to obtain a modified molecular sieve.

[0012] The present invention improves the ion exchange capacity of the modified molecular sieve for heavy metals such as Pb and Cd through zirconium doping and pore construction. Zirconium doping optimizes the charge distribution of the molecular sieve framework, enhancing its electrostatic interaction with heavy metal ions, while the pore structure provides a pathway for ion diffusion, thereby improving the ion exchange capacity of the modified molecular sieve for heavy metals such as Pb and Cd. Furthermore, the preparation method provided by the present invention introduces thiol and amino groups through grafting modification, which serve as specific adsorption sites and can form stable chelate bonds with Hg and As, thereby increasing the adsorption capacity of the modified molecular sieve for Hg and As.

[0013] In addition, the preparation method provided by the present invention introduces titanium oxide groups through grafting modification, which can be excited to produce hydroxyl radicals and superoxide anions under light conditions, and can decompose organic pollutants adsorbed on the surface of the molecular sieve through photocatalysis, thereby avoiding the blockage problem caused by the deposition of organic matter in the pores, maintaining the patency of the material's pore structure, and enabling the molecular sieve to maintain stable adsorption performance during continuous wastewater treatment, thereby extending the service life of the molecular sieve.

[0014] In addition, the present invention can avoid crystal defects caused by sudden temperature rise by limiting the heating rate, temperature and time during the crystallization process, promote uniform polycondensation of aluminosilicate, and generate molecular sieve crystals with uniform particle size.

[0015] Preferably, in S1, the ratio of the tetraethyl orthosilicate, aluminum isopropoxide, anhydrous ethanol and water is (1-3) g: (0.5-1.5) g: (10-15) mL: (5-10) mL.

[0016] The present invention ensures uniform construction of the silicon-aluminum skeleton by limiting the usage of tetraethyl orthosilicate and aluminum isopropoxide, avoids a decrease in skeleton stability due to an excessively high aluminum content, and also avoids an impact on ion exchange capacity due to an excessively low aluminum content. Anhydrous ethanol is used as a solvent to form a mixed system with water, which promotes uniform hydrolysis of tetraethyl orthosilicate and aluminum isopropoxide, while controlling the viscosity of the sol and preventing excessively rapid gel formation.

[0017] Preferably, in S2, the ratio of zirconium oxychloride to water is (0.5-1.5) g: (2-8) mL.

[0018] Preferably, in S2, the volume ratio of water to silica-alumina sol is 1:20-25.

[0019] The present invention avoids the agglomeration of zirconium ions by controlling the dosage of zirconium oxychloride, silica-alumina sol and water, ensuring their uniform dispersion in the silica-alumina sol. At the same time, it can also avoid excessive dilution of the sol and maintain the viscosity of the system, thereby ensuring the diffusion efficiency of zirconium ions and preventing molecular sieve framework defects caused by component imbalance during crystallization.

[0020] Preferably, in S3, the volume ratio of the mixed sol to the tetrapropylammonium hydroxide aqueous solution is (8-11) mL:1 mL.

[0021] Preferably, in S3, the crystallization reaction temperature rise rate is 5°C / min-10°C / min, and the time is 24h-72h.

[0022] Preferably, in S3, the mass fraction of the tetrapropylammonium hydroxide aqueous solution is 20%-30%.

[0023] Further preferably, in S3, the crystallization reaction is carried out in a stainless steel reactor with a polytetrafluoroethylene lining.

[0024] Further preferably, in S3, the calcination to remove the template comprises the following steps:

[0025] The crystallized product is washed to neutrality, dried at 100-120° C. for 6-12 hours, and then calcined at 500-600° C. for 4-8 hours to obtain a primary molecular sieve.

[0026] The present invention can precisely control the concentration of the template in the system by limiting the volume ratio of the mixed sol and the tetrapropylammonium hydroxide solution, ensuring that the template fully occupies the pore position during the crystallization process and guiding the silicon-aluminum skeleton to form a regular mesoporous structure. The above-mentioned limitation avoids incomplete crystallization caused by too low a concentration of tetrapropylammonium hydroxide and prevents side reactions caused by too high a concentration, thereby improving the crystallinity of the molecular sieve.

[0027] The present invention also limits various parameters in the calcination process to ensure that the calcination process will not damage the molecular sieve skeleton structure.

[0028] Preferably, in S4, the usage ratio of the primary molecular sieve, anhydrous ethanol, 3-mercaptopropyltrimethoxysilane and aminopropyltriethoxysilane is (0.5-1.5) g: (5-15) mL: (0.01-0.05) mL: (0.01-0.05) mL.

[0029] Preferably, in S4, the grafting reaction temperature is 60° C.-80° C., the rotation speed is 200 r / min-600 r / min, and the time is 6 h-12 h.

[0030] The present invention ensures that the 3-mercaptopropyltrimethoxysilane and aminopropyltriethoxysilane are fully dispersed in the mixed solution and avoids local agglomeration by limiting the amounts of the primary molecular sieve, anhydrous ethanol, 3-mercaptopropyltrimethoxysilane, and aminopropyltriethoxysilane. The present invention also ensures that the mercapto groups and amino groups are uniformly grafted onto the surface of the molecular sieve by limiting the parameters of the grafting reaction.

[0031] Preferably, in S5, the usage ratio of the primary molecular sieve, anhydrous ethanol, tetrabutyl titanate and aminopropyltriethoxysilane is (0.5-1.5) g: (5-15) mL: (0.03-0.07) mL: (0.01-0.05) mL.

[0032] Preferably, in S5, the grafting reaction temperature is 50° C.-70° C., the rotation speed is 200 r / min-600 r / min, and the time is 4 h-8 h.

[0033] In the present invention, hydrolysis of tetrabutyl titanate can introduce titanium oxide groups through grafting modification. The present invention can avoid agglomeration of titanium oxide groups by limiting the amounts of primary grafting modified molecular sieve, anhydrous ethanol, tetrabutyl titanate and aminopropyltriethoxysilane.

[0034] The second aspect of the present invention provides a modified molecular sieve prepared by the preparation method of the modified molecular sieve described in the above scheme.

[0035] The third aspect of the present invention provides a device for desulfurization of wastewater, comprising a container and the modified molecular sieve described in the aforementioned scheme, wherein the modified molecular sieve is filled into the container in the order of coarse particles, medium particles and fine particles from the water inlet to the water outlet.

[0036] Preferably, the particle size of the coarse particles is 50 μm-100 μm, the particle size of the medium particles is 25 μm-40 μm, and the particle size of the fine particles is 5 μm-20 μm.

[0037] The present invention forms a gradient interception system by constructing a multi-stage filtration structure. Coarse particles preferentially intercept large-particle suspended matter and flocs in the desulfurization wastewater, reducing the risk of clogging of the fine particle layer; medium particles further intercept medium-sized impurities to balance the water flow resistance; fine particles capture tiny heavy metal ions and organic pollutants through dense pores. This desulfurization wastewater device achieves efficient layered removal of pollutants and alleviates the front-end clogging problem of traditional single-pore materials through the pore gradient, so that the device can maintain high filtration accuracy while improving the water flow rate and extending the service life. It does not require frequent backwashing, and significantly reduces operating costs.

[0038] In summary, the preparation method of the modified molecular sieve provided by the present invention synergistically enhances the ion exchange capacity of the silica-alumina zeolite framework for heavy metals such as Pb and Cd through zirconium doping and pore construction; at the same time, the present invention introduces thiol and amino groups through grafting modification, so that the adsorption capacity of the modified molecular sieve for Hg and As is improved; in addition, the present invention introduces titanium oxide groups through grafting modification, which can generate hydroxyl radicals and superoxide anions under light conditions, and decompose the adsorbed organic pollutants through photocatalysis, achieving a self-cleaning effect, avoiding pore blockage, and thus extending the material life cycle. In addition, the device for desulfurization wastewater provided by the present invention forms a layered interception system by using coarse particles, medium particles and fine particles for gradient filling. The coarse particles preferentially intercept large-particle suspended solids, the medium particles intercept medium impurities, and the fine particles capture heavy metal ions and organic pollutants, avoiding the efficiency attenuation of single-aperture materials due to front-end blockage, and ensuring that the device maintains high filtration accuracy and water flow rate during operation. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiment is only one embodiment of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides a modified molecular sieve and its preparation method and application, which specifically include the following contents:

[0042] The preparation method of the modified molecular sieve comprises the following steps:

[0043] S1. Mix 100 g of ethyl orthosilicate, 50 g of aluminum isopropoxide, and 1000 mL of anhydrous ethanol, and slowly add 500 mL of deionized water dropwise under stirring to obtain a silica-alumina sol.

[0044] S2. Dissolve 20 g of zirconium oxychloride in 80 mL of deionized water, and then add the solution to 1600 mL of silica-alumina sol to obtain a mixed sol.

[0045] S3. Add 125 mL of 20% tetrapropylammonium hydroxide solution to 1000 mL of the mixed sol, adjust the pH value to 9 with 1 mol / L sodium hydroxide solution, and then transfer the mixed solution to a stainless steel reactor lined with polytetrafluoroethylene. Heat it to 120°C at a heating rate of 5°C / min and crystallize it for 24 hours. Then cool it naturally to room temperature. Filter the reaction product with deionized water and wash it until the washing liquid is neutral. After drying it at 100°C for 6 hours, calcinate it at 500°C for 4 hours to obtain a primary molecular sieve.

[0046] S4. Add 100 g of primary molecular sieve to 1000 mL of anhydrous ethanol, and then add 2 mL of 3-mercaptopropyltrimethoxysilane and 2 mL of aminopropyltriethoxysilane in sequence to obtain a suspension. Under nitrogen protection, heat the suspension to 60°C, keep it warm at 200 r / min for 6 hours, filter, wash, and dry the product to obtain a primary grafted modified molecular sieve.

[0047] S5. Mix 6 mL of tetrabutyl titanate and 2 mL of aminopropyltriethoxysilane, and slowly add the mixture dropwise to 1000 mL of anhydrous ethanol containing 100 g of the primary grafted modified molecular sieve. Keep the mixture at 50°C and 200 r / min for 4 h, filter, wash, and dry to obtain the modified molecular sieve.

[0048] The device for desulfurizing wastewater comprises a container and a modified molecular sieve.

[0049] The modified molecular sieve prepared above was ground and sieved to obtain coarse particles with a particle size of 50 μm, medium particles with a particle size of 25 μm, and fine particles with a particle size of 5 μm.

[0050] The coarse particles, medium particles and fine particles are sequentially filled into the container in the direction from the water inlet to the water outlet.

[0051] Example 2

[0052] This embodiment provides a modified molecular sieve and its preparation method and application, which specifically include the following contents:

[0053] The preparation method of the modified molecular sieve comprises the following steps:

[0054] S1. Mix 300 g of ethyl orthosilicate, 150 g of aluminum isopropoxide, and 1500 mL of anhydrous ethanol, and slowly add 1000 mL of deionized water dropwise under stirring to obtain a silica-alumina sol.

[0055] S2. Dissolve 6 g of zirconium oxychloride in 32 mL of deionized water, and then add the solution to 800 mL of silica-alumina sol to obtain a mixed sol.

[0056] S3. Add 12.5 mL of 20% tetrapropylammonium hydroxide solution to 137.5 mL of the mixed sol, adjust the pH value to 9 with 1 mol / L sodium hydroxide solution, and then transfer the mixed solution to a stainless steel reactor with a polytetrafluoroethylene liner. Heat it to 180°C at a heating rate of 10°C / min and crystallize it for 72 hours. Then cool it naturally to room temperature. Filter the reaction product with deionized water and wash it until the washing liquid is neutral. After drying it at 120°C for 12 hours, calcinate it at 600°C for 8 hours to obtain a primary molecular sieve.

[0057] S4. Add 150 g of primary molecular sieve to 1500 mL of anhydrous ethanol, and then add 5 mL of 3-mercaptopropyltrimethoxysilane and 5 mL of aminopropyltriethoxysilane in sequence to obtain a suspension. Under nitrogen protection, heat the suspension to 80°C, keep it warm at 600 r / min for 12 hours, filter the product, wash it, and dry it to obtain a primary grafted modified molecular sieve.

[0058] S5. After mixing 7 mL of tetrabutyl titanate and 5 mL of aminopropyltriethoxysilane, slowly add the mixture dropwise to 1500 mL of anhydrous ethanol containing 150 g of the primary grafted modified molecular sieve. After keeping the mixture at 70°C and 600 r / min for 8 h, filter, wash, and dry to obtain the modified molecular sieve.

[0059] The device for desulfurizing wastewater comprises a container and a modified molecular sieve.

[0060] The modified molecular sieve prepared above was ground and sieved to obtain coarse particles with a particle size of 100 μm, medium particles with a particle size of 40 μm, and fine particles with a particle size of 20 μm.

[0061] The coarse particles, medium particles and fine particles are sequentially filled into the container in the direction from the water inlet to the water outlet.

[0062] Example 3

[0063] This embodiment provides a modified molecular sieve and its preparation method and application, which specifically include the following contents:

[0064] The preparation method of the modified molecular sieve comprises the following steps:

[0065] S1. Mix 200 g of ethyl orthosilicate, 100 g of aluminum isopropoxide, and 1250 mL of anhydrous ethanol, and slowly add 750 mL of deionized water dropwise under stirring to obtain a silica-alumina sol.

[0066] S2. Dissolve 40 g of zirconium oxychloride in 200 mL of deionized water, and then add the solution to 1400 mL of silica-alumina sol to obtain a mixed sol.

[0067] S3. Add 100 mL of 25% tetrapropylammonium hydroxide solution to 1000 mL of the mixed sol, adjust the pH value to 10 with 1 mol / L sodium hydroxide solution, and then transfer the mixed solution to a stainless steel reactor lined with polytetrafluoroethylene. Heat it to 150°C at a heating rate of 7°C / min and crystallize it for 48 hours. Then cool it naturally to room temperature. Filter the reaction product with deionized water and wash it until the washing liquid is neutral. After drying it at 110°C for 8 hours, calcinate it at 550°C for 6 hours to obtain a primary molecular sieve.

[0068] S4. Add 100 g of primary molecular sieve to 1000 mL of anhydrous ethanol, and then add 3 mL of 3-mercaptopropyltrimethoxysilane and 3 mL of aminopropyltriethoxysilane in sequence to obtain a suspension. Under nitrogen protection, heat the suspension to 70°C, keep it warm at 400 r / min for 8 hours, filter, wash, and dry the product to obtain a primary grafted modified molecular sieve.

[0069] S5. After mixing 5 mL of tetrabutyl titanate and 3 mL of aminopropyltriethoxysilane, slowly add the mixture dropwise to 1000 mL of anhydrous ethanol containing 100 g of the primary grafted modified molecular sieve. After keeping the mixture at 60° C. and 400 rpm for 6 h, filter, wash, and dry to obtain the modified molecular sieve.

[0070] The device for desulfurizing wastewater comprises a container and a modified molecular sieve.

[0071] The modified molecular sieve prepared above was ground and sieved to obtain coarse particles with a particle size of 75 μm, medium particles with a particle size of 30 μm, and fine particles with a particle size of 15 μm.

[0072] The coarse particles, medium particles and fine particles are sequentially filled into the container in the direction from the water inlet to the water outlet.

[0073] Comparative Example 1

[0074] This comparative example provides a filtering device, which specifically includes the following contents:

[0075] The filtering device comprises a container and a molecular sieve, wherein the molecular sieve is filled in the container; the molecular sieve is a silicon-aluminum molecular sieve; and the particle size of the molecular sieve is 30 μm.

[0076] The preparation method of the molecular sieve comprises the following steps:

[0077] 200 g of ethyl orthosilicate, 100 g of aluminum isopropoxide and 1250 mL of anhydrous ethanol were mixed, and 750 mL of deionized water was slowly added dropwise under stirring to obtain a silica-alumina sol, which was then filtered, washed and dried to obtain the molecular sieve.

[0078] Comparative Example 2

[0079] This comparative example provides a filtering device, which specifically includes the following contents:

[0080] The preparation method of the modified molecular sieve comprises the following steps:

[0081] S1. Mix 200 g of ethyl orthosilicate, 100 g of aluminum isopropoxide, and 1250 mL of anhydrous ethanol, and slowly add 750 mL of deionized water dropwise under stirring to obtain a silica-alumina sol.

[0082] S2. Dissolve 40 g of zirconium oxychloride in 200 mL of deionized water, and then add the solution to 1400 mL of silica-alumina sol to obtain a mixed sol.

[0083] S3. Add 100 mL of 25% tetrapropylammonium hydroxide solution to 1000 mL of the mixed sol, adjust the pH value to 10 with 1 mol / L sodium hydroxide solution, and then transfer the mixed solution to a stainless steel reactor lined with polytetrafluoroethylene. Heat it to 150°C at a heating rate of 7°C / min and crystallize it for 48 hours. Then cool it naturally to room temperature. Filter the reaction product with deionized water and wash it until the washing liquid is neutral. After drying it at 110°C for 8 hours, calcinate it at 550°C for 6 hours to obtain a primary molecular sieve.

[0084] S4. Add 100 g of primary molecular sieve to 1000 mL of anhydrous ethanol, and then add 3 mL of 3-mercaptopropyltrimethoxysilane and 3 mL of aminopropyltriethoxysilane in sequence to obtain a suspension. Under nitrogen protection, heat the suspension to 70°C, keep it warm at 400 r / min for 8 hours, filter, wash, and dry the product to obtain a primary grafted modified molecular sieve.

[0085] S5. After mixing 5 mL of tetrabutyl titanate and 3 mL of aminopropyltriethoxysilane, slowly add the mixture dropwise to 1000 mL of anhydrous ethanol containing 100 g of the primary grafted modified molecular sieve. After keeping the mixture at 60° C. and 400 rpm for 6 h, filter, wash, and dry to obtain the modified molecular sieve.

[0086] The filtering device comprises a container and a modified molecular sieve, wherein the modified molecular sieve is filled in the container; the particle size of the modified molecular sieve is 30 μm.

[0087] The desulfurization wastewater device in Example 1-3 and the filtering device in Comparative Example 1-2 were tested for adsorption effect. Specifically, 5 portions of 1000 mL of desulfurization wastewater were taken at room temperature, and the desulfurization wastewater device in Example 1-3 and the filtering device in Comparative Example 1-2 were added to the desulfurization wastewater, respectively. The pH value was adjusted to 4 with acetic acid, and the desulfurization wastewater was filtered for 24 hours under stirring. The filtrate was then poured out and the filtrate was subjected to inductively coupled plasma mass spectrometry analysis and water quality analyzer detection. The results are shown in Table 1. The lead concentration in the desulfurization wastewater was 30 μg / L, the chromium concentration was 20 μg / L, the mercury concentration was 10 μg / L, the cadmium concentration was 20 μg / L, the aromatic hydrocarbon organic matter concentration was 45 μg / L, and the pH was 7.2.

[0088] Table 1 Adsorption effect test table

[0089] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Pb removal rate / % 98.9 99.8 99.7 49.5 42.7 Cd removal rate / % 99.1 99.9 99.6 50.2 50.2 Hg removal rate / % 99.0 99.7 99.4 49.7 50.4 As removal rate / % 98.7 99.2 98.9 55.2 52.7 Aromatic hydrocarbon organic matter removal rate / % 97.7 97.2 97.5 30.8 44.7

[0090] As can be seen from Table 1, the desulfurization wastewater treatment devices provided in Examples 1-3 of the present invention exhibit excellent adsorption performance, with heavy metal ion removal rates reaching 98.7% and aromatic hydrocarbon organic matter removal rates reaching 97.2%. In contrast, the filtration devices in Comparative Examples 1-2 exhibit poor adsorption performance. Therefore, the desulfurization wastewater treatment devices provided by the present invention exhibit excellent adsorption performance.

[0091] The desulfurization wastewater device in Example 1-3 and the filter device in Comparative Example 1-2 were tested for adsorption service life. Specifically, 5 portions of 1000 mL of desulfurization wastewater were taken at room temperature, and the desulfurization wastewater device in Example 1-3 and the filter device in Comparative Example 1-2 were added to the desulfurization wastewater, respectively. The pH value was adjusted to 4 with acetic acid, and the desulfurization wastewater was filtered under stirring. The desulfurization wastewater was updated every 24 hours, and the filtrate was poured out every 7 days. The filtrate was subjected to inductively coupled plasma mass spectrometry analysis. The test was stopped when the adsorption effect significantly decreased. The results are shown in Table 2. The lead concentration in the desulfurization wastewater was 30 μg / L, the chromium concentration was 20 μg / L, the mercury concentration was 10 μg / L, the cadmium concentration was 20 μg / L, the aromatic hydrocarbon organic matter concentration was 45 μg / L, and the pH was 7.2.

[0092] Table 2 Service life test table

[0093]

[0094]

[0095] It can be seen from Table 2 that the desulfurization wastewater device provided by Examples 1-3 of the present invention maintains a high Pb removal rate within 42 days, and the Pb removal rate drops significantly after 48 days, indicating that the service life of Examples 1-3 of the present invention is 42 days, while the Pb removal rate of Comparative Example 1-2 drops significantly after 7 days, indicating that the service life of the filter device in Comparative Example 1-2 is 7 days.

[0096] The above are all preferred embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a modified molecular sieve, characterized in that: The steps include: S1. Mixing ethyl orthosilicate, aluminum isopropoxide, anhydrous ethanol and water to obtain a silica-alumina sol; S2. Mixing zirconium oxychloride with water and adding the mixture to the silica-alumina sol to obtain a mixed sol; S3, mixing the mixed sol with a tetrapropylammonium hydroxide aqueous solution, adjusting the pH to 9-11, performing a crystallization reaction at 120° C.-180° C., and calcining to remove the template to obtain a primary molecular sieve; S4, mixing the primary molecular sieve, anhydrous ethanol, 3-mercaptopropyltrimethoxysilane and aminopropyltriethoxysilane, and performing a grafting reaction to obtain a primary grafted modified molecular sieve; S5. Mixing the primary graft-modified molecular sieve, anhydrous ethanol, tetrabutyl titanate and aminopropyltriethoxysilane, and performing a grafting reaction to obtain a modified molecular sieve.

2. The method for preparing the modified molecular sieve according to claim 1, wherein In S1, the ratio of the tetraethyl orthosilicate, aluminum isopropoxide, anhydrous ethanol and water is (1-3) g: (0.5-1.5) g: (10-15) mL: (5-10) mL.

3. The method for preparing the modified molecular sieve according to claim 1, wherein In S2, the ratio of zirconium oxychloride to water is (0.5-1.5) g: (2-8) mL; and / or In S2, the volume ratio of water to silica-alumina sol is 1:20-25.

4. The method for preparing the modified molecular sieve according to claim 1, wherein In S3, the volume ratio of the mixed sol to the tetrapropylammonium hydroxide aqueous solution is (8-11) mL:1 mL, wherein the mass fraction of the tetrapropylammonium hydroxide aqueous solution is 20%-30%; and / or In S3, the crystallization reaction temperature rise rate is 5°C / min-10°C / min, and the time is 24h-72h.

5. The method for preparing the modified molecular sieve according to claim 1, wherein In S4, the ratio of the primary molecular sieve, anhydrous ethanol, 3-mercaptopropyltrimethoxysilane and aminopropyltriethoxysilane is (0.5-1.5) g: (5-15) mL: (0.01-0.05) mL: (0.01-0.05) mL; and / or In S5, the usage ratio of the primary grafted modified molecular sieve, anhydrous ethanol, tetrabutyl titanate and aminopropyltriethoxysilane is (0.5-1.5) g: (5-15) mL: (0.03-0.07) mL: (0.01-0.05) mL.

6. The method for preparing the modified molecular sieve according to claim 1, wherein In S4, the grafting reaction temperature is 60° C.-80° C., the rotation speed is 200 r / min-600 r / min, and the time is 6 h-12 h.

7. The method for preparing the modified molecular sieve according to claim 1, wherein In S5, the grafting reaction temperature is 50° C.-70° C., the rotation speed is 200 r / min-600 r / min, and the time is 4 h-8 h.

8. A modified molecular sieve, characterized in that: The modified molecular sieve is prepared by the preparation method according to any one of claims 1 to 7.

9. A device for desulfurization wastewater, characterized in that: The modified molecular sieve comprises a container and the modified molecular sieve according to claim 8, wherein the modified molecular sieve is filled into the container by sequentially filling coarse particles, medium particles and fine particles in the direction from the water inlet to the water outlet.

10. The device for desulfurization wastewater according to claim 9, characterized in that: The particle size of the coarse particles is 50 μm-100 μm, the particle size of the medium particles is 25 μm-40 μm, and the particle size of the fine particles is 5 μm-20 μm.

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