All-silicon molecular sieve and preparation method thereof

Abstract

The invention discloses an all-silicon molecular sieve and a preparation method thereof. The all-silicon molecular sieve is a hollow spherical particle material, the average particle size is 153-167 nm, the thickness of a hollow shell layer is 4-15 nm, the specific surface area is 430-603 m < 2 > / g, the average pore size is 6.27-8.89 nm, and the pore volume is 0.45-0.94 cm < 3 > / g. The invention also discloses a preparation method of the all-silicon molecular sieve. The all-silicon molecular sieve disclosed by the invention has relatively high specific surface area, relatively large pore volume, relatively low density, excellent chemical stability and surface permeability, relatively high biocompatibility and the like, and the all-silicon molecular sieve material is used for adsorbing and removing trace-level non-metal boron impurities through a chelation effect, so that the trace-level non-metal boron impurities can be adsorbed and removed. The removal efficiency of impurities is 90.6-98.9%, and the adsorbent is superior to existing adsorbents such as industrial activated carbon and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to an all-silica molecular sieve and a preparation method thereof. Background Art

[0002] Hollow spherical all-silica molecular sieves have attracted much attention due to their large inner core and interpenetrating mesoporous channel structure. Compared with traditional silicon-based microspheres, they have the structural advantages of lower density, thermal expansion coefficient, and refractive index, larger specific surface area, and a controllable outer mesoporous pore wall, and have broad application prospects. The hard template method is currently the main method for preparing hollow materials. A hard template is used to guide the formation of a hollow inner cavity, and then a mesoporous structure directing agent is used to induce the co-assembly of the coating material to form a mesoporous shell through intermolecular forces such as electrostatic interaction and hydrogen bonding. According to the types of templates used, it can be divided into polymer microspheres (such as polystyrene microspheres, phenolic resin spheres, etc.), metal spheres (such as Fe2O3), and inorganic microspheres (such as hydroxyapatite, calcium carbonate, etc.). However, these template methods generally have difficulty in obtaining a hollow structure at the nanoscale, and the cost is relatively high, and some are not easy to obtain.

[0003] Hollow spherical all-silica molecular sieves have been proven to be a non-toxic material with good biocompatibility and good mechanical stability, so they can be widely used in the fields of catalysis, adsorption, drug storage and release, nano-reactors, sensors, etc.

[0004] For example, patent application CN201911155003.1 reported a simple preparation method of a graphene oxide / organic hollow silica composite material, and for the first time, the present invention used the graphene oxide / organic hollow silica composite material for adsorbing methylene blue, and its adsorption effect was significantly improved compared with that of pure organic hollow silica and GO / organic silica.

[0005] For example, patent application CN201911185323.1 reported a preparation method of a nano-level fuel catalytic oxidation adsorption desulfurization catalyst. This material can efficiently reduce the dibenzothiophene sulfides that are difficult to remove in fuel, greatly reduce the amount of catalyst used, does not require an extraction process, and has good cycle stability. It realizes the coupling of catalytic oxidation adsorption desulfurization in one step, improves the desulfurization efficiency of the catalyst, simplifies the desulfurization process flow, and greatly reduces the industrial application cost, and has good application prospects in fuel catalytic oxidation desulfurization.

[0006] For example, patent application CN202110275809.5 reported a preparation method of hollow mesoporous silica dual-drug sustained-release microspheres for osteoporosis treatment. This patent uses surface-activated hollow mesoporous silica microspheres as drug carriers, which have the advantages of controllable drug release rate, good biocompatibility, high drug loading rate and encapsulation rate, and long-term drug sustained release. The combined application of two drugs can effectively inhibit the activity and function of osteoclasts while promoting bone formation, and can avoid the development of drug resistance in the body and improve the treatment effect.

[0007] Currently, the methods for removing boron impurities in water mainly include chemical precipitation method, adsorption method, ion exchange resin method, membrane separation technology and extraction method, etc. These methods have their own advantages and disadvantages and are applicable to different water qualities and treatment requirements. Among them, the adsorption method mainly uses adsorbents such as kaolin, montmorillonite, goethite, coal ash, cellulose derivatives, activated carbon, etc. These adsorbents can effectively adsorb boron impurities, but the regeneration process takes a long time, and long-term use will lead to a decrease in adsorption capacity, affecting the final effect.

[0008] Therefore, there is an urgent need to develop an adsorption material with good boron impurity adsorption performance that can simultaneously remove trace amounts of boron impurities. Summary of the Invention

[0009] The first technical problem to be solved by the present invention is to provide a pure silica molecular sieve; when this pure silica molecular sieve is used in the process of removing ppb-level impurity concentration in an aqueous system, the removal efficiency for boron impurities is 90.6 - 98.9%, which is superior to existing industrial adsorbents such as activated carbon.

[0010] The second technical problem to be solved by the present invention is to provide a preparation method for the above-mentioned pure silica molecular sieve.

[0011] To solve the above first technical problem, the technical solution adopted by the present invention is as follows:

[0012] A pure silica molecular sieve, which is a hollow spherical particulate material with an average particle size of 153 - 167 nm, a hollow shell thickness of 4 - 15 nm, a specific surface area of 430 - 603 m 2 / g, an average pore diameter of 6.27 - 8.89 nm, and a pore volume of 0.45 - 0.94 cm 3 / g.

[0013] To solve the above second technical problem, the technical solution adopted by the present invention is as follows:

[0014] A preparation method for a pure silica molecular sieve, comprising the following steps:

[0015] 1) Grind and screen the hard template agent solid, add it to a solvent, and disperse it by ultrasonic wave to form a well-dispersed template agent dispersion;

[0016] 2) Add a surfactant to the template agent dispersion to prepare an aqueous solution, heat it, and then add the silicon source solution, mix evenly to obtain suspension B.

[0017] 3) Add an acid to deionized water to prepare a dilute acid solution, denoted as feed solution C, and uniformly add feed solution C to suspension B.

[0018] 4) Adjust the pH of the reaction solution after mixing suspension B and feed solution C, age for a period of time, filter, wash, and dry to obtain a white precipitate; calcine the white precipitate in a muffle furnace to obtain a white powdery all-silica molecular sieve adsorbent; or treat the white precipitate by chemical means to remove the template agent, and then wash, filter, and dry with deionized water to obtain a white powdery all-silica molecular sieve adsorbent.

[0019] Preferably, in step 1), the template agent is one or more of PS microspheres, SiO2 microspheres, calcium hydroxide, calcium carbonate, and iron trioxide.

[0020] Preferably, in step 1), the solvent is one of deionized water, methanol, and ethanol.

[0021] Preferably, in step 1), the mass fraction of the template agent in the template agent dispersion is 5%-15%.

[0022] Preferably, in step 1), the mesh number of the screening is 200-400 meshes.

[0023] Preferably, in step 2), the surfactant is one or more of cetyltrimethylammonium bromide (C 19 H 42 BrN), dodecyltrimethylammonium chloride (C 15 H 34 ClN), cetyl alcohol polyoxyethylene (CH3(CH2) 15 (OC2H4) 10 OH, Brij-56), and sodium dodecyl sulfate (C 12 H 25 SO4Na).

[0024] Preferably, in step 2), the mass fraction of the surfactant is 0.1-0.5%.

[0025] Preferably, in step 2), the mass ratio of the effective component SiO2 in the silicon source solution to the template agent is 0.1-0.4.

[0026] Preferably, in step 2), the mass fraction of the silicon source solution is 2-10%.

[0027] Preferably, in step 2), the silicon source is sodium metasilicate nonahydrate (Na2SiO3·9H2O), sodium silicate, tetraethyl orthosilicate (C8H 20 O4Si, TEOS), tetramethyl orthosilicate (C4H 12 O4Si, TMOS), silica sol (SiO2·nH2O), or one or more of them.

[0028] Preferably, in step 3), the acid is one or more of hydrochloric acid, nitric acid, acetic acid, and sulfuric acid.

[0029] Preferably, in step 3), the molar ratio of the acid to the silicon source in step 2) is 1.6 - 2.4.

[0030] Preferably, in step 4), the pH = 8 - 10.

[0031] Preferably, in step 4), the aging temperature is 50 - 100 °C; the aging time is 20 - 240 min.

[0032] Preferably, in step 4), the drying temperature is 110 - 150 °C.

[0033] Preferably, in step 4), the mesh number of the filtration is 200 - 300 meshes.

[0034] Preferably, in step 4), the calcination temperature is 500 - 700 °C, and the time is 4 - 6 h.

[0035] Preferably, in step 4), the chemical means include one or two of solvent corrosion and solvent extraction.

[0036] Preferably, in step 4), the drying temperature is 60 - 80 °C.

[0037] Any range described in the present invention includes the end values and any numerical value between the end values, as well as any sub-range constituted by any numerical value between the end values or the end values.

[0038] Unless otherwise specified, each raw material in the present invention can be obtained by commercial purchase, and the equipment used in the present invention can be conventional equipment in the field or can be referred to the existing technology in the field.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] When the molecular sieve of the present invention is used in the process of removing boron impurities in the water system, the removal efficiency of boron impurities is 90.6 - 98.9%, which is superior to the existing industrial adsorbents such as activated carbon.

[0041] The preparation method of the all-silica molecular sieve provided by the present invention has a relatively low production cost, the raw materials are relatively easy to obtain, and the synthesis conditions are less affected by environmental changes, making it suitable for industrial use. Moreover, relying on the large specific surface area and pore diameter of the hollow all-silica molecular sieve, it has a wide range of applications in adsorption, catalysis, drug carriers and release, etc. It has good adsorption performance, especially has a relatively high adsorption efficiency for boron impurities in water systems. In addition, the all-silica molecular sieve material itself is environmentally friendly, non-toxic and harmless, and only contains two elements, silicon and oxygen, and will not cause pollution to the system. Description of the Drawings

[0042] The following further elaborates in detail the specific embodiments of the present invention in conjunction with the drawings.

[0043] Figure 1 X-ray diffraction pattern of the all-silica molecular sieve prepared in Example 1

[0044] Figure 2 Scanning electron microscope photograph of the all-silica molecular sieve prepared in Example 1;

[0045] Figure 3 Nitrogen adsorption isotherm and pore size distribution diagram of the all-silica molecular sieve prepared in Example 1;

[0046] Figure 4 Transmission electron microscope photograph of the all-silica molecular sieve prepared in Example 1;

[0047] Figure 5 Adsorption experiment device diagram used to detect the adsorption performance of the adsorbents prepared in Examples 1-6 and Comparative Examples 1-5 of the present invention. This device is mainly composed of a three-neck glass flask, a glass adapter, a rubber syringe and a rubber stopper, etc. Specific Embodiments

[0048] To illustrate the present invention more clearly, the following further describes the present invention in conjunction with preferred embodiments. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0049] As one aspect of the present invention, an all-silica molecular sieve of the present invention, the all-silica molecular sieve is a hollow spherical particle material, with an average particle size of 153-167 nm, a hollow shell layer thickness of 4-15 nm, a specific surface area of 430-603 m 2 / g, an average pore diameter of 6.27-8.89 nm, and a pore volume of 0.45-0.94 cm 3 / g.

[0050] As another aspect of the present invention, a preparation method of an all-silica molecular sieve of the present invention includes the following steps:

[0051] 1) Grind the hard template solid powder, sieve it, add it to a solvent, and disperse it ultrasonically to form a well-dispersed templating agent dispersion.

[0052] 2) Add a surfactant to the templating agent dispersion to prepare an aqueous solution, heat it, and then add a silicon source solution and mix evenly to obtain suspension B.

[0053] 3) Add an acid to deionized water to prepare a dilute acid solution, denoted as feed solution C, and uniformly add feed solution C to suspension B.

[0054] 4) Adjust the pH of the reaction solution after mixing suspension B and feed solution C, age for a period of time, filter, wash, and dry to obtain a white precipitate; calcine the white precipitate in a muffle furnace to obtain a white powdery all-silica molecular sieve adsorbent; or treat the white precipitate by chemical means to remove the templating agent, then wash, filter, and dry with deionized water to obtain a white powdery all-silica molecular sieve.

[0055] According to some embodiments of the present invention, in step 1), the templating agent is one or more of PS microspheres, SiO2 microspheres, calcium hydroxide, calcium carbonate, and iron(III) oxide. According to some embodiments of the present invention, in step 1), the solvent is one of deionized water, methanol, and ethanol.

[0056] According to some embodiments of the present invention, in step 1), the mass fraction of the templating agent in the templating agent dispersion is 5%-15%.

[0057] According to some embodiments of the present invention, in step 1), the mesh number of the sieving is 200-400 meshes. According to some embodiments of the present invention, in step 2), the surfactant is one or more of cetyltrimethylammonium bromide (C 19 H 42 BrN), dodecyltrimethylammonium chloride (C 15 H 34 ClN), cetyl alcohol polyoxyethylene (CH3(CH2) 15 (OC2H4) 10 OH, Brij-56), and sodium dodecyl sulfate (C 12 H 25 SO4Na).

[0058] According to some embodiments of the present invention, in step 2), the mass fraction of the surfactant is 0.1-0.5%.

[0059] According to certain embodiments of the present invention, in step 2), the mass ratio of the active ingredient SiO2 in the silicon source solution to the template agent is 0.1 - 0.4. According to certain embodiments of the present invention, in step 2), the mass fraction of the silicon source solution is 2 - 10%. According to certain embodiments of the present invention, in step 2), the silicon source is one or more of sodium metasilicate nonahydrate (Na2SiO3·9H2O), sodium silicate, tetraethyl orthosilicate (C8H 20 O4Si, TEOS), tetramethyl orthosilicate (C4H 12 O4Si, TMOS), silica sol (SiO2·nH2O). According to certain embodiments of the present invention, in step 3), the acid is one or more of hydrochloric acid, nitric acid, acetic acid, and sulfuric acid.

[0060] According to certain embodiments of the present invention, in step 3), the molar ratio of the acid to the silicon source in step 2) is 1.6 - 2.4.

[0061] According to certain embodiments of the present invention, in step 4), the pH = 8 - 10. According to certain embodiments of the present invention, in step 4), the aging temperature is 50 - 100 °C; the aging time is 20 - 240 min.

[0062] According to certain embodiments of the present invention, in step 4), the drying temperature is 110 - 150 °C. According to certain embodiments of the present invention, in step 4), the mesh number of the filtration is 200 - 300 mesh. According to certain embodiments of the present invention, in step 4), the calcination temperature is 500 - 700 °C, and the time is 4 - 6 h.

[0063] According to certain embodiments of the present invention, in step 4), the chemical means includes one or two of solvent corrosion and solvent extraction.

[0064] According to certain embodiments of the present invention, in step 4), the drying temperature is 60 - 80 °C.

[0065] Example 1

[0066] A method for preparing an all-silica molecular sieve, comprising the following steps:

[0067] 1) Weigh 20 g of polystyrene solid, grind it, and pass it through a 200 - 400 mesh sieve to obtain fine powder; weigh 10 g of the polystyrene fine powder into deionized water and disperse it by ultrasonic wave to form a 7% polystyrene suspension 1;

[0068] 2) Weigh 0.3 g of cetyltrimethylammonium bromide and dissolve it in Polystyrene Suspension 1; then dissolve 13.889 g of tetraethyl orthosilicate in 181 ml of deionized water, add it to Suspension 1, and heat to 60 °C. This suspension is denoted as Feed Liquid B;

[0069] 3) According to Hydrochloric Acid: Silicon Source = 1.8 (molar ratio), weigh 11.64 g of 37% concentrated hydrochloric acid and uniformly add it to Feed Liquid B; then according to SiO2 / Polystyrene = 40% (mass ratio), uniformly add a silicon source solution with a certain SiO2 concentration;

[0070] 4) Adjust the pH of the mixed reaction solution to 9, age at 60 °C for 60 min, filter, wash, and dry at 110 °C to obtain a white precipitate; after screening the dried product, calcine it in a muffle furnace at 600 °C for 6 h to obtain a white powdery all-silica molecular sieve (hollow microsphere adsorbent material).

[0071] The all-silica molecular sieve (hollow sphere adsorbent material) was characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and transmission electron microscopy instruments. The average particle size of the all-silica molecular sieve (hollow microsphere adsorbent material) was found to be 160 nm, the shell thickness was 11.5 nm, the specific surface area was 603 m 2 / g, pore volume: 0.94 cm 3 / g, average pore diameter: 8.89 nm.

[0072] Figure 1 This is the scanning electron microscopy photograph of the all-silica molecular sieve prepared in Example 1;

[0073] Figure 2 This is the X-ray diffraction pattern of the all-silica molecular sieve prepared in Example 1;

[0074] Figure 3 This is the nitrogen adsorption isotherm and pore size distribution diagram of the all-silica molecular sieve prepared in Example 1;

[0075] Figure 4 This is the transmission electron microscopy photograph of the all-silica molecular sieve prepared in Example 1.

[0076] The results of the impurity removal efficiency of the all-silica molecular sieve prepared in this example applied to the removal of boron impurities in the water system are shown in Table 1 below.

[0077] Example 2

[0078] A method for preparing an all-silica molecular sieve, comprising the following steps:

[0079] 1) Weigh 20 g of polystyrene solid, grind it, and sieve it through a 200 - 400 mesh sieve. Weigh 10 g of polystyrene fine powder into deionized water and disperse it ultrasonically to form a 7% Polystyrene Suspension 1;

[0080] 2) Weigh 0.3 g of dodecyltrimethylammonium chloride and dissolve it in Polystyrene Suspension 1. Then dissolve 10.128 g of methyl orthosilicate in 181 ml of deionized water, add it to Suspension 1, and heat to 60 °C. This suspension is denoted as Feed Liquid B;

[0081] 3) According to hydrochloric acid: silicon source = 1.8 (molar ratio), weigh 11.64 g of 37% concentrated hydrochloric acid and uniformly add it to Feed Liquid B; then according to SiO2 / Polystyrene = 40% (mass ratio), uniformly add a silicon source solution with a certain SiO2 concentration;

[0082] 4) Adjust the pH of the mixed reaction solution to 9, age it at 70 °C for 60 min, filter, wash, and dry at 110 °C to obtain a white precipitate. After screening the dried product, calcine it in a muffle furnace at 600 °C for 6 h to obtain a white powder of all-silica molecular sieve hollow microsphere adsorbent material.

[0083] The all-silica molecular sieve hollow spherical material prepared in this example was characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and transmission electron microscopy instruments. It was found that the average particle size of the all-silica molecular sieve hollow microsphere adsorbent material was 154 nm, the shell thickness was 6 nm, the specific surface area was 416 m 2 / g, the pore volume: 0.59 cm 3 / g, and the average pore diameter: 7.29 nm.

[0084] The results of the impurity removal efficiency of the all-silica molecular sieve hollow spherical material prepared in this example for the removal of boron impurities in the water system are shown in Table 1 below.

[0085] Example 3

[0086] A preparation method of all-silica molecular sieve, comprising the following steps:

[0087] 1) Weigh 20 g of polystyrene solid, grind it, and sieve it through a 200 - 400 mesh sieve. Weigh 10 g of polystyrene fine powder into deionized water and ultrasonically disperse it to form a 7% Polystyrene Suspension 1;

[0088] 2) Weigh 0.3 g of dodecyltrimethylammonium chloride and dissolve it in Polystyrene Suspension 1. Then dissolve 10 g of silica sol (40%) in 181 ml of deionized water, add it to Suspension 1, and heat to 60 °C. This suspension is denoted as Feed Liquid B;

[0089] 3) According to hydrochloric acid: silicon source = 1.8 (molar ratio), weigh 11.64 g of 37% concentrated hydrochloric acid and uniformly add it to Feed Liquid B. Then according to SiO2 / Polystyrene = 40% (mass ratio), uniformly add a silicon source solution with a certain SiO2 concentration;

[0090] 4) The pH of the mixed reaction solution was adjusted to 9, aged at 60 °C for 60 min, filtered, washed, and dried at 110 °C to obtain a white precipitate. After screening the dried product, it was calcined in a muffle furnace at 600 °C for 6 h to obtain a white powder of the all-silica molecular sieve hollow microsphere adsorbent material.

[0091] The all-silica molecular sieve hollow spherical material was characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and transmission electron microscopy. It was found that the average particle size of the all-silica molecular sieve hollow microsphere adsorbent material was 153 nm, the shell thickness was 4.79 nm, the specific surface area was 524 m 2 / g, pore volume: 0.72 cm 3 / g, average pore diameter: 8.20 nm.

[0092] The impurity removal efficiency results of the all-silica molecular sieve hollow spherical material prepared in this example for the removal of boron impurities in the water system are shown in Table 1 below.

[0093] Example 4

[0094] A preparation method of an all-silica molecular sieve includes the following steps:

[0095] 1) Weigh 20 g of polystyrene solid, grind it, and sieve it through a 200 - 400 mesh sieve. Weigh 10 g of polystyrene fine powder into deionized water, and disperse it ultrasonically to form a 7% polystyrene suspension 1;

[0096] 2) Weigh 0.3 g of dodecyltrimethylammonium chloride and dissolve it in polystyrene suspension 1. Then dissolve 8.126 g of sodium silicate in 181 ml of deionized water, add it to suspension 1, and heat it to 60 °C. This suspension is denoted as feed liquid B;

[0097] 3) According to hydrochloric acid: silicon source = 1.8 (molar ratio), weigh 11.64 g of 37% concentrated hydrochloric acid and add it uniformly to feed liquid B. Then, according to SiO2 / polystyrene = 40% (mass ratio), uniformly add a silicon source solution with a certain SiO2 concentration;

[0098] 4) The pH of the mixed reaction solution was adjusted to 9, aged at 60 °C for 30 min, filtered, washed, and dried at 110 °C to obtain a white precipitate. After screening the dried product, it was calcined in a muffle furnace at 500 °C for 6 h to obtain a white powder of the all-silica molecular sieve hollow microsphere adsorbent material.

[0099] The all-silica molecular sieve hollow spherical material was characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and transmission electron microscopy. It was found that the average particle size of the all-silica molecular sieve hollow microsphere adsorbent material was 161 nm, the shell thickness was 12.2 nm, the specific surface area was 531 m2 / g, pore volume: 0.60 cm 3 / g, average pore diameter: 6.70 nm.

[0100] The results of the impurity removal efficiency of the all-silica molecular sieve hollow spherical material prepared in this example for the removal of boron impurities in the water system are shown in Table 1 below.

[0101] Example 5

[0102] A preparation method of an all-silica molecular sieve includes the following steps:

[0103] 1) Weigh 20 g of polystyrene solid, grind it, and pass it through a 200 - 400 mesh sieve. Weigh 20 g of polystyrene fine powder into deionized water, and disperse it ultrasonically to form a 7% polystyrene suspension 1;

[0104] 2) Weigh 0.3 g of cetyltrimethylammonium bromide and dissolve it in polystyrene suspension 1. Then dissolve 13.889 g of tetraethyl orthosilicate in 181 ml of deionized water, add it to suspension 1, and heat it to 60 °C. This suspension is denoted as feed liquid B;

[0105] 3) According to hydrochloric acid: silicon source = 2.2 (molar ratio), weigh 11.64 g of 37% concentrated hydrochloric acid and add it evenly to feed liquid B. Then, according to SiO2 / polystyrene = 20% (mass ratio), evenly add a silicon source solution with a certain SiO2 concentration;

[0106] 4) Adjust the pH of the mixed reaction solution to 9, age it at 60 °C for 60 min, filter, wash, and dry it at 110 °C to obtain a white precipitate. After screening the dried product, calcine it in a muffle furnace at 600 °C for 6 h to obtain a white powdery all-silica molecular sieve hollow microsphere adsorption material.

[0107] The all-silica molecular sieve hollow spherical material was characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and transmission electron microscopy instruments. It was found that the average particle size of the all-silica molecular sieve hollow microsphere adsorption material was 156 nm, the shell thickness was 6.1 nm, and the specific surface area was 430 m 2 / g, pore volume: 0.79 cm 3 / g, average pore diameter: 8.10 nm.

[0108] The results of the impurity removal efficiency of the all-silica molecular sieve hollow spherical material prepared in this example for the removal of boron impurities in the water system are shown in Table 1 below.

[0109] Example 6

[0110] A preparation method of an all-silica molecular sieve adsorbent includes the following steps:

[0111] 1) Weigh 20 g of polystyrene solid, grind it, and sieve it through a 200 - 400 mesh sieve. Weigh 20 g of the polystyrene fine powder into deionized water, and disperse it ultrasonically to form a 7% polystyrene suspension 1;

[0112] 2) Weigh 0.3 g of cetyltrimethylammonium bromide and dissolve it in the polystyrene suspension 1. Then dissolve 13.889 g of tetraethyl orthosilicate in 181 ml of deionized water, add it to the suspension 1, and heat it to 60 °C. This suspension is denoted as feed liquid B;

[0113] 3) According to hydrochloric acid: silicon source = 1.8 (molar ratio), weigh 11.64 g of 37% concentrated hydrochloric acid, and add it evenly to the feed liquid B. Then, according to SiO₂ / polystyrene = 20% (mass ratio), evenly add a silicon source solution with a certain SiO₂ concentration;

[0114] 4) Adjust the pH of the mixed reaction solution to 10, age it at 60 °C for 60 min, filter, wash, and dry it at 110 °C to obtain a white precipitate. After screening the dried product, calcine it in a muffle furnace at 600 °C for 6 h to obtain a white powdered all - silica molecular sieve hollow microsphere adsorbent material.

[0115] The all - silica molecular sieve hollow spherical material is characterized by X - ray diffraction, scanning electron microscopy, nitrogen adsorption, and transmission electron microscopy. It is found that the average particle size of the all - silica molecular sieve hollow microsphere adsorbent material is 158 nm, the shell thickness is 9.1 nm, the specific surface area is 536 m 2 / g, the pore volume: 0.92 cm 3 / g, and the average pore diameter: 8.40 nm.

[0116] The results of the removal efficiency of the all - silica molecular sieve prepared in this example applied to the removal of boron impurities in the water system are shown in Table 1 below.

[0117] Application Example 7

[0118] By preparing a standard solution of boric acid (H₃BO₃) with a certain concentration, configuring a crude impurity system solution containing a certain amount of boron impurities (from 100 to 1100 ppb), quantitatively detecting the boron impurity concentration therein by ICP - MS, and using the static adsorption method to detect the adsorption performance of the all - silica molecular sieves prepared in Examples 1 - 6 and Comparative Examples 1 - 5 of this patent. The adsorption experimental device is shown in Figure 5 This device is mainly composed of a three - neck glass flask, a glass adapter, a rubber syringe, a rubber stopper, etc. The specific operation process of the adsorption experiment is as follows:

[0119] ① Put the all - silica molecular sieve adsorbent dried and dehydrated at 150 °C into the three - neck flask, and seal the bottle mouth with a single - pass valve and a rubber stopper with a turned - up mouth;

[0120] ②Open the one-way valve, use a vacuum pump to evacuate the flask, and close the one-way valve after 2 - 3 minutes.

[0121] ③Connect the one-way valve to nitrogen, slowly open the valve, and close the valve after the nitrogen fills up.

[0122] ④Repeat steps 2 and 3 twice (the purpose is to exhaust the water vapor in the flask).

[0123] ⑤Use a syringe to suck a certain amount of the crude impurity system solution and inject it into the glass flask, gently shake the flask to completely immerse the all-silica molecular sieve in the solution.

[0124] ⑥After the adsorption is completed, use a syringe to extract a certain amount of the supernatant, filter it through an organic filter membrane, analyze the boron impurity content by ICP-MS, and finally calculate the adsorption efficiency of the all-silica molecular sieve adsorbent.

[0125] Comparative Example 1

[0126] Repeat Example 1, the difference is only that cetyltrimethylammonium bromide (CTAB) surfactant is not added.

[0127] After detection, the average particle size of the all-silica molecular sieve hollow microsphere adsorption material is 167 nm, the shell thickness is 11 nm, the specific surface area is 478 m 2 / g, the pore volume: 0.67 cm 3 / g, the average pore diameter: 8.14 nm, and the adsorption rate for boron impurities decreases from 98.90% to 87.24%.

[0128] It can be seen that due to the lack of surfactant, the specific surface area, pore volume, and average pore diameter will decrease, resulting in a worse adsorption effect (the detection of the adsorption effect is carried out according to Application Example 7). The results of the impurity removal efficiency of the all-silica molecular sieve adsorbent in this comparative example for the removal of boron impurities in the water system are shown in Table 1 below.

[0129] Comparative Example 2

[0130] Repeat Example 2, the difference is only that the solid content of the template agent suspension is 4%.

[0131] After detection, the average particle size of the all-silica molecular sieve hollow microsphere adsorption material is 154 nm, the shell thickness is 4 nm, the specific surface area is 534 m 2 / g, the pore volume: 0.78 cm 3 / g, the average pore diameter: 7.79 nm, and the adsorption rate for boron impurities decreases from 97.92% to 86.71%.

[0132] It can be seen that due to the change in the solid content of the template agent suspension, the specific surface area, pore volume, and average pore diameter will decrease, resulting in a deterioration of the adsorption effect (the detection of the adsorption effect is carried out according to Application Example 7). The results of the impurity removal efficiency of the all-silica molecular sieve adsorbent specifically applied to the removal of boron impurities in the water system are shown in Table 1 below.

[0133] Comparative Example 3

[0134] Repeat Example 3, with the only difference being that hydrochloric acid: silicon source = 1.5 (molar ratio).

[0135] After detection, the average particle diameter of the all-silica molecular sieve hollow microsphere adsorption material is 163 nm, the shell thickness is 13 nm, the specific surface area is 499 m 2 / g, pore volume: 0.81 cm 3 / g, average pore diameter: 8.01 nm, and the adsorption rate for boron impurities decreases from 96.24% to 85.14%.

[0136] It can be seen that due to the change in hydrochloric acid: silicon source (molar ratio), the specific surface area, pore volume, and average pore diameter will decrease, resulting in a deterioration of the adsorption effect (the detection of the adsorption effect is carried out according to Application Example 7). The results of the impurity removal efficiency of the all-silica molecular sieve adsorbent specifically applied to the removal of boron impurities in the water system are shown in Table 1 below.

[0137] Comparative Example 4

[0138] Repeat Example 4, with the only difference being that SiO2 / polystyrene = 50% (mass ratio).

[0139] After detection, the average particle diameter of the all-silica molecular sieve hollow microsphere adsorption material is 155 nm, the shell thickness is 5 nm, the specific surface area is 213 m 2 / g, pore volume: 0.45 cm 3 / g, average pore diameter: 3.27 nm, the product is basically solid particles and not formed, and the adsorption rate for boron impurities decreases from 94.25% to 82.28%.

[0140] It can be seen that due to the change, the product cannot be formed, resulting in a deterioration of the adsorption effect (the detection of the adsorption effect is carried out according to Application Example 7). The results of the impurity removal efficiency of the all-silica molecular sieve adsorbent specifically applied to the removal of boron impurities in the water system are shown in Table 1 below.

[0141] Comparative Example 5

[0142] Repeat Example 5, with the only difference being that the aging temperature is 25 °C.

[0143] After detection, the average particle size of the all-silica molecular sieve hollow microsphere adsorbent is 165 nm, the shell thickness is 15 nm, the specific surface area is 481 m 2 / g, the pore volume: 0.71 cm 3 / g, the average pore diameter: 8.40 nm, and the adsorption rate for boron impurities decreases from 93.51% to 81.94%.

[0144] Thus, due to the change in the aging temperature, the specific surface area, pore volume, and average pore diameter will decrease, which in turn leads to a deterioration of the adsorption effect (the detection of the adsorption effect is carried out according to Application Example 7). The results of the impurity removal efficiency of the all-silica molecular sieve adsorbent specifically applied to the removal of boron impurities in the water system are shown in Table 1 below.

[0145] Table 1

[0146]

[0147] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. An all-silicon molecular sieve, characterized in that: The all-silicon molecular sieve is a hollow spherical particle material with an average particle size of 153-167nm, a hollow shell thickness of 4-15nm, and a specific surface area of ​​430-603m 2 / g, average pore diameter of 6.27-8.89nm, pore volume of 0.45-0.94cm 3 / g.

2. The method for preparing the all-silicon molecular sieve according to claim 1, characterized in that: The steps include: 1) grinding and sieving the hard template solid, adding it to a solvent, and ultrasonically dispersing it to form a well-dispersed template dispersion; 2) Add the surfactant to the template dispersion to prepare an aqueous solution, heat it, then add the silicon source solution, mix well, and obtain a suspension B. 3) Add the acid into deionized water to prepare a dilute acid solution, referred to as feed solution C, and evenly add feed solution C into suspension B. 4) adjusting the pH of the reaction solution after the suspension B and the feed solution C are mixed, aging for a period of time, filtering, washing, and drying to obtain a white precipitate; calcining the white precipitate in a muffle furnace to obtain a white powdery all-silicon molecular sieve adsorbent; or treating the white precipitate by chemical means to remove the template agent, and then washing with deionized water, filtering, and drying to obtain a white powdery all-silicon molecular sieve.

3. The preparation method according to claim 2, characterized in that: In step 1), the template is one or more of PS microspheres, SiO2 microspheres, calcium hydroxide, calcium carbonate, and ferrous oxide; Preferably, in step 1), the solvent is one of deionized water, methanol and ethanol.

4. The preparation method according to claim 2, characterized in that: In step 1), the mass fraction of the template in the template dispersion is 5%-15%; Preferably, in step 1), the mesh size of the sieving is 200-400 meshes.

5. The preparation method according to claim 2, characterized in that: In step 2), the surfactant is hexadecyltrimethylammonium bromide (C 19 H 42 BrN), dodecyltrimethylammonium chloride (C 15 H 34 ClN), cetyl alcohol polyoxyethylene (CH3(CH2) 15 (OC2H4) 10 OH, Brij-56), sodium lauryl sulfate (C 12 H 25 SO4Na) or more.

6. The preparation method according to claim 2, characterized in that: In step 2), the mass fraction of the surfactant is 0.1-0.5%.

7. The preparation method according to claim 2, characterized in that: In step 2), the mass ratio of the active ingredient SiO2 in the silicon source solution to the template is 0.1-0.

4.

8. The preparation method according to claim 2, characterized in that: In step 2), the mass fraction of the silicon source solution is 2-10%; Preferably, in step 2), the silicon source is sodium metasilicate nonahydrate (Na2SiO3.9H2O), sodium silicate, ethyl orthosilicate (C8H 20 O4Si, TEOS), methyl orthosilicate (C4H 12 O4Si, TMOS), silica sol (SiO2.nH2O) or one or more thereof.

9. The preparation method according to claim 2, characterized in that: In step 3), the acid is one or more of hydrochloric acid, nitric acid, acetic acid, and sulfuric acid; Preferably, in step 3), the molar ratio of the acid to the silicon source in step 2) is 1.6-2.

4.

10. The preparation method according to claim 2, characterized in that: In step 4), the pH is 8-10; Preferably, in step 4), the aging temperature is 50-100° C. and the aging time is 20-240 min; Preferably, in step 4), the drying temperature is 110-150°C; Preferably, in step 4), the mesh size of the filtration is 200-300 mesh; Preferably, in step 4), the calcination temperature is 500-700°C and the time is 4-6h; Preferably, in step 4), the chemical means comprises one or both of solvent corrosion and solvent extraction; Preferably, in step 4), the drying temperature is 60-80°C.

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