Hollow porous silica hydrophobic microspheres, and preparation method and application thereof

Abstract

The application belongs to the technical field of nanomaterials, and particularly relates to a hollow porous silica hydrophobic microsphere and a preparation method and application thereof. The preparation method comprises the following steps: mixing a hard template and anhydrous ethanol by ultrasonic dispersion to obtain a hard template dispersion liquid; adding the hard template dispersion liquid into a solvent to stir and adding ammonia water under the stirring state, then adding a soft template to continue stirring to obtain a mixed liquid; adding a hole expanding agent to the mixed liquid, then dropwise adding tetraethyl orthosilicate to continue stirring to carry out a reaction to obtain a product; performing centrifugation, washing, drying and calcination treatment on the product to obtain a calcined product; and performing water bath heating reaction on the calcined product and organosiloxane to obtain the hollow porous silica hydrophobic microsphere. The hollow porous silica hydrophobic microsphere has a simple preparation method, mild conditions, no toxicity and harmlessness, and common materials are used as raw materials, and the material can be used for water pollutant adsorption.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a hollow porous silica hydrophobic microsphere, its preparation method, and its application. Background Technology

[0002] Hollow microspheres are a new type of nanomaterial with a cavity structure. Due to their advantages such as high specific surface area, low density and tunable pore system, good biocompatibility and easy surface functionalization, and their internal cavities can serve as effective loading space for active molecules, they have broad application prospects in high-end fields such as catalyst carriers, pollutant adsorption, and drug controlled release.

[0003] Template-based methods are currently the most widely used approach for preparing hollow microspheres. Depending on the template used, template-based methods are divided into hard template methods and soft template methods. However, the core principle of both methods is to utilize the support and framework provided by the template to adsorb one or more layers of material onto its surface, followed by subsequent processing to obtain hollow microspheres. Hard template methods yield hollow microspheres with good controllability in morphology and size, and high monodispersity. However, the removal of hard templates is cumbersome, and the shell is prone to breakage during the removal process. While soft template methods are relatively simpler and the soft template is easier to remove, their precision control over morphology and size is not as good as that of hard template methods, and their stability is poorer.

[0004] Meanwhile, existing technologies often employ fluorides to hydrophobically modify hollow microspheres. However, while traditional fluorides such as perfluoroalkyl substances (PFAS), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonic acid (PFOS) can impart excellent hydrophobic and oleophobic properties to materials, their high environmental persistence and bioaccumulation have raised widespread concerns. Studies have confirmed that these compounds are extremely difficult to degrade under natural conditions, can remain for several years, and can be transferred and accumulated through the food chain, exerting toxic effects on liver function, the immune system, and developmental processes in organisms.

[0005] Furthermore, existing fluorination modification processes mostly rely on perfluoroalkylsiloxanes (such as heptadecafluorodecyltrimethoxysilane) and react in high-temperature or strongly acidic environments. This process not only releases fluorinated volatile organic compounds (FVOCs), but the fluorinated wastewater generated in subsequent treatment stages also poses a further threat to the environment. Most importantly, existing hollow microspheres cannot achieve efficient separation and removal of oil pollutants of specific sizes or structures (such as aromatic hydrocarbons, aliphatic hydrocarbons, or complex mixed oil sludge). Summary of the Invention

[0006] The purpose of this invention is to provide a hollow porous silica hydrophobic microsphere, its preparation method, and its applications, thereby overcoming the shortcomings of existing technologies. This study successfully prepared porous microspheres with both structural integrity and hydrophobic function through a four-pronged technical strategy: synergistic pore-forming with hard-soft templates, low-toxicity synthesis using a water-alcohol system, gradient calcination control, and mild silanization modification. This provides a new generation of platform materials for the development of high-performance catalysts and efficient pollutant adsorbents. The prepared hollow porous silica hydrophobic microspheres, with their hierarchical pore structure and flexibly tunable surface chemical properties, exhibit significant application potential in the field of pollutant adsorption.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing hollow porous silica hydrophobic microspheres, comprising the following steps:

[0009] (1) Add the hard template dispersion to the solvent and stir to mix well. Add ammonia and soft template to obtain a mixture.

[0010] (2) Add a pore-expanding agent to the mixture and add tetraethyl orthosilicate dropwise to react and obtain the product;

[0011] The pore-expanding agent is one or more of 1,3,5-trimethylbenzene, triisopropylbenzene, and polypropylene glycol;

[0012] (3) The product is calcined to obtain the calcined product;

[0013] (4) The calcined product is reacted with organosiloxane in a water bath to obtain hollow porous silica hydrophobic microspheres.

[0014] This invention successfully prepared multifunctional microspheres with both structural integrity and hydrophobicity through synergistic pore-forming with hard and soft templates, low-toxicity synthesis with solvents (water-alcohol system), and modification by calcination followed by mild silanization. This provides a new generation of platform materials for the development of high-end catalysts and pollutant adsorbents.

[0015] In some other embodiments, in step (1), the hard template is one or more of polystyrene microspheres or polymethyl methacrylate microspheres; the particle size of the hard template is 300-800 nm;

[0016] The polystyrene microspheres have a molecular weight of 50,000-100,000 Da.

[0017] The hard template dispersion is an anhydrous ethanol solution of the hard template with a concentration of 5-10 wt%.

[0018] Specifically, the particle size of the hard template is 300, 400, 500, 600, 700, or 800 nm; the concentration of the hard template dispersion is 5, 6, 7, 8, 9, or 10 wt%; and the ultrasonic dispersion time is 10, 15, or 20 min. The molecular weight of the polystyrene microspheres is 50,000, 60,000, 70,000, 80,000, 90,000, or 100,000 Da.

[0019] Preferably, the hard template is polystyrene microspheres with a particle size of 400 or 500 nm; the concentration of the hard template dispersion is 10 wt%, and the molecular weight of the polystyrene microspheres is 50,000 Da.

[0020] The tetraethyl orthosilicate (TEOS) prepared within this range can be uniformly penetrated and deposited in the gaps between the hard template spheres, ultimately producing silica microspheres with complete structure, ordered pores, and good mechanical stability.

[0021] In some other embodiments, in step (1), the volume ratio of the hard template dispersion to the solvent is 1:(10-16).

[0022] The solvent is a mixture of anhydrous ethanol and deionized water; the volume ratio of the anhydrous ethanol to the deionized water is (1-4):1.

[0023] Specifically, the volume ratio of the hard template dispersion to the solvent is 1:10, 1:12, 1:14, or 1:16; the volume ratio of anhydrous ethanol to deionized water is 1:1, 2:1, 3:1, or 4:1.

[0024] Preferably, the volume ratio of the hard template dispersion to the solvent is 1:10 or 1:16; and the volume ratio of anhydrous ethanol to deionized water is 1:1 or 4:1.

[0025] During their research, the inventors discovered that the choice of solvent can enable the template microspheres to form a stable and uniform dispersion, avoiding aggregation and sedimentation. Simultaneously, the solvent affects the dissolution and reaction of TEOS, accelerating the entire process. Using a mixture of anhydrous ethanol and deionized water as the solvent allows for precise control of the TEOS hydrolysis and condensation rate, which is beneficial for obtaining dispersed, structurally regular silica microspheres.

[0026] In some other embodiments, in step (1), the ammonia content in the mixture is 3wt%-7wt%, and the concentration of the ammonia is 20wt%-25wt%.

[0027] The content of soft template in the mixture is 0.5wt%-1wt%;

[0028] The soft template is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer;

[0029] The molecular weight of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer is 4000-15000 Da, and the proportion of PEO blocks is approximately 30-70%.

[0030] Specifically, the ammonia content in the mixture is 3, 4, 5, 6 or 7 wt%, and the concentration of the ammonia is 20, 22, 24 or 25 wt%.

[0031] Preferably, the soft template is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0032] In some other embodiments, in step (2), the pore-expanding agent is one or more of 1,3,5-trimethylbenzene, triisopropylbenzene, and polypropylene glycol; the molecular weight of the polypropylene glycol is 200-4000 Da.

[0033] The purity of the tetraethyl orthosilicate is >99%, the dropping rate is 0.05-0.1 mL / min, and the reaction time is 24-30 h. Specifically, the dropping rate is 0.05, 0.07, 0.09, or 0.1 mL / min, and the reaction time is 24, 26, 28, or 30 h.

[0034] In some other embodiments, step (3) includes centrifugation, washing and drying processes in sequence before the calcination treatment;

[0035] The washing process involves alternating between anhydrous ethanol and deionized water, with the number of washes exceeding 3.

[0036] The drying temperature is 75-85℃ and the time is 5-7 hours;

[0037] The calcination process involves a heating rate of 2-10℃ / min, an atmosphere of air, a temperature of 450-650℃, and a holding time of 3-6h.

[0038] Specifically, the drying temperature is 75, 80 or 85°C, and the drying time is 5, 6 or 7 hours;

[0039] The calcination heating rate is 2, 4, 6, 8, or 10 °C / min, the temperature is 450, 500, 550, or 650 °C, and the holding time is 3, 4, 5, or 6 h. Preferably, the calcination heating rate is 10 °C / min, the temperature is 550 °C, and the holding time is 3 h.

[0040] In some other embodiments, in step (4), the water bath heating temperature is 60-90°C and the time is 1-3 hours;

[0041] The mass ratio of the calcined product to the organosiloxane is (4-10):1.

[0042] The purity of the organosiloxane is >95%, and the organosiloxane is one or more of octadecyltrimethoxysilane, octadecyltriethoxysilane, and hexadecyltrimethoxysilane.

[0043] Specifically, the water bath heating temperature is 60, 70, 80, or 90°C, and the time is 1, 2, or 3 hours. Preferably, the water bath heating temperature is 90°C, and the time is 1 hour. The mass ratio of the calcined product to the organosiloxane is 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1. The organosiloxane is octadecyltriethoxysilane.

[0044] After being modified with long-chain alkylsilanes, the surface of the microspheres forms a stable hydrophobic layer (water contact angle >120°). Its low surface energy characteristics enable the microspheres to exhibit high affinity for non-polar organic pollutants in water (such as polycyclic aromatic hydrocarbons, organochlorine pesticides, mineral oils, etc.), which significantly improves their stability and application effect in the aquatic environment.

[0045] This invention strictly follows the sequence of "calcination to remove the template, followed by silanization and hydrophobic modification." This ensures that the hydrophobic alkyl chains are directly and uniformly grafted onto the pure SiO2 framework via covalent bonds. The modification effect is thorough and long-lasting, and it does not clog the already formed mesoporous channels, perfectly preserving the material's high specific surface area and adsorption capacity. The reaction is carried out in a constant-temperature water bath (60-90℃) using long-chain alkylsilanes, under mild conditions and low energy consumption, requiring no high pressure, strong acid / strong base catalysts, or toxic organic solvents. This application completely removes the template through calcination, requiring only simple washing after modification, and the product has no template residue or modifier residue.

[0046] In some other embodiments, the stirring is magnetic stirring, and the stirring speed is 150-250 rpm;

[0047] After the water bath heating reaction is completed, centrifugation, washing, and drying are also performed; the centrifugation speed is 8000-10000 r / min, and the centrifugation time is 10-20 min.

[0048] In a second aspect, the present invention provides hollow porous silica hydrophobic microspheres prepared by the method described in the first aspect, which have a core-shell structure, with the core being a cavity and the shell being porous silica; the porous silica has a mesoporous structure and its surface is modified with hydrophobic groups.

[0049] Specifically, the hollow porous silica hydrophobic microspheres have a pore size of 2-10 nm, a particle size of 436-543 nm, a porous silica layer thickness of 15.5-46.1 nm, and a pore volume of 0.225-0.396 cm³. 3 / g, specific surface area is 467-621m² 2 / g, with a contact angle range of 102.4°-141.2°.

[0050] Thirdly, the present invention provides the application of the hollow porous silica hydrophobic microspheres described in the second aspect in oily wastewater, adsorption of organic pollutants, and catalysts.

[0051] Fourthly, the present invention provides a method for treating oily wastewater, wherein the hollow porous silica hydrophobic microspheres described in the second aspect are added to the oily wastewater; the oily wastewater contains one or more of aromatic hydrocarbons, medium-chain hydrocarbons, and polycyclic aromatic hydrocarbons.

[0052] In some other embodiments, the amount of the hollow porous silica hydrophobic microspheres added is 0.01–5 wt% of the total mass of the wastewater, preferably 0.05–1 wt%.

[0053] The aromatic hydrocarbon is benzene; the medium-chain hydrocarbon is one or both of diesel oil and lubricating oil; the polycyclic aromatic hydrocarbon is anthracene.

[0054] The beneficial effects of this invention are:

[0055] (1) In the preparation method of hollow porous silica hydrophobic microspheres of the present invention, all materials and reagents used are non-toxic and harmless, and the preparation process is safe and environmentally friendly, meeting the requirements of green chemistry. Through the sequential action of hard-soft templates and the regulation of pore-expanding agents, the precise construction of multi-level pore structures is achieved. Through the reaction with long-chain alkylsilanes, the hollow porous silica hydrophobic microspheres are endowed with excellent hydrophobicity, realizing intelligent selective adsorption of pollutants in water bodies, solving the key defects caused by the "indiscriminate adsorption" of traditional adsorption materials, and significantly improving their stability and application effect in the aquatic environment.

[0056] (2) The preparation method of the present invention is simple and easy to implement, with mild operating conditions, requiring no special equipment or complex processes, and is easy to achieve large-scale production. The raw materials used are all common chemicals, such as anhydrous ethanol, deionized water, and tetraethyl orthosilicate, which are easy to obtain and inexpensive, thus helping to reduce production costs and promote widespread application.

[0057] (3) The hollow porous silica hydrophobic microspheres prepared by this invention have a pore size of 2-10 nm, a particle size of 450-550 nm, a porous silica layer thickness of 10-50 nm, and a pore volume of 0.30-0.50 cm³. 3 / g, specific surface area is 500-800 m² 2 / g; Hollow porous silica hydrophobic microspheres, with their unique hierarchical pore structure and tunable surface chemistry, have shown significant advantages in the field of pollutant adsorption.

[0058] (4) This invention achieves controllable adjustment of the pore size of hollow porous silica hydrophobic microspheres by precisely controlling the dosage and concentration of the soft template and the pore expander. The inventors found that the change in the concentration of the soft template directly affects the regularity of the formation of the mesoporous structure, while the dosage of the pore expander determines the size and connectivity of the pores. Through the synergistic control of the two, a series of hollow hydrophobic microspheres with pore sizes ranging from 2 nm to 10 nm can be obtained. Different pore sizes give the material special advantages in molecular sieving and selective adsorption, enabling it to achieve efficient separation and removal of oil pollutants (such as aromatic hydrocarbons, aliphatic hydrocarbons, or complex mixed oil pollution) of specific sizes or structures. This breaks through the limitation of "indiscriminate adsorption" of traditional adsorption materials and significantly improves the selectivity and precision of oil-water separation and pollutant treatment. Attached Figure Description

[0059] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0060] Figure 1 This is a low-magnification scanning electron microscope image of the hollow porous silica hydrophobic microspheres prepared in Example 1 of this invention;

[0061] Figure 2 This is a high-magnification scanning electron microscope image of the hollow porous silica hydrophobic microspheres prepared in Example 1 of this invention;

[0062] Figure 3 This is a low-magnification scanning electron microscope image of the hollow porous silica hydrophobic microspheres prepared in Example 6 of the present invention;

[0063] Figure 4 This is a high-magnification scanning electron microscope image of the hollow porous silica hydrophobic microspheres prepared in Example 6 of the present invention.

[0064] Figure 5 This is a transmission electron microscope image of the hollow porous silica hydrophobic microspheres prepared in Example 6 of the present invention;

[0065] Figure 6 The Fourier transform infrared spectrum of the hollow porous silica microspheres prepared in Example 6 of this invention before hydrophobic modification;

[0066] Figure 7The Fourier transform infrared spectrum of the hollow porous silica microspheres prepared in Example 6 of this invention after hydrophobic modification;

[0067] Figure 8 The water contact angle is the angle of the hollow porous silica microspheres prepared in Examples 1-6 of this invention after hydrophobic modification and spraying onto a glass substrate. Detailed Implementation

[0068] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0069] As mentioned earlier, existing hollow microsphere preparation technologies have long been hampered by bottlenecks such as high toxicity, high breakage rate, inability to selectively adsorb and remove oil pollutants of specific sizes or structures, and limited functionality.

[0070] The inventive concept of this invention is to strictly follow the preparation sequence of "first constructing a complete inorganic framework, then performing organic functionalization." Specifically, after thoroughly removing all template agents through high-temperature calcination to form a pure, high-specific-surface-area hollow mesoporous SiO2 framework, a hydrophobication reaction is then carried out with long-chain alkylsilanes under mild water bath conditions. This post-calcination modification strategy overcomes the technical bottleneck of functionalization in multi-template systems. Its advantages are: ensuring that hydrophobic groups are uniformly and persistently grafted onto the final SiO2 framework only through covalent bonds, avoiding damage to the modified layer or "pseudo-hydrophobicity" caused by template residue or calcination decomposition; maximizing the protection of the high specific surface area and large pore volume of the hollow mesoporous structure, enabling the hydrophobically modified microspheres to possess both excellent hydrophobicity and superior adsorption capacity, achieving synergistic effects between "structure" and "function"; avoiding the complex side reactions and pore blockage risks that may arise from introducing organosilanes before high-temperature calcination; and allowing the final modification step to be completed in a low-temperature, aqueous environment, making the process safer and more environmentally friendly.

[0071] By organically integrating four technologies, this approach not only achieves a multifunctional integration of hollow, porous, and hydrophobic materials in terms of design, but also realizes a green, low-toxicity, and controllable preparation path at the process level. The successful implementation of this multi-technology synergy relies on a profound understanding and precise control of the interactions between each step, representing a level of systematic innovation that existing single or dual-technology patents have failed to achieve. The hollow porous silica hydrophobic microspheres prepared using this technology exhibit significant advantages in the field of pollutant adsorption due to their unique hierarchical pore structure and tunable surface chemistry.

[0072] This invention provides a method for preparing hollow porous silica hydrophobic microspheres, comprising the following steps:

[0073] (1) The hard template was ultrasonically dispersed and mixed with anhydrous ethanol to obtain a hard template dispersion;

[0074] (2) Add the hard template dispersion to the solvent and stir while stirring. Add ammonia water while stirring, then add the soft template and continue stirring to obtain a mixture.

[0075] (3) Add a pore-expanding agent to the mixture, then add tetraethyl orthosilicate dropwise, and continue stirring to carry out the reaction to obtain the product;

[0076] (4) The product is centrifuged, washed, dried and calcined to obtain the calcined product;

[0077] (5) The calcined product is reacted with organosiloxane in a water bath to obtain hollow porous silica hydrophobic microspheres.

[0078] The solution of the present invention will be further described below with reference to specific embodiments:

[0079] I. Preparation of Hollow Porous Silica Hydrophobic Microspheres

[0080] Example 1

[0081] A method for preparing hollow porous silica hydrophobic microspheres includes the following steps:

[0082] (1) Disperse 5 mL of polystyrene microspheres (molecular weight 50000 Da) with a diameter of 400 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol and sonicate for 10 min to obtain a polystyrene microsphere dispersion.

[0083] (2) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker; add the hard template dispersion to the solvent and stir magnetically for 10 min; add 2 mL of ammonia water (concentration 25wt%) while stirring to adjust the alkalinity of the solution; add 2 g of hexadecyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution;

[0084] (3) Under magnetic stirring, add 2 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; add 2 mL of tetraethyl orthosilicate dropwise at a rate of 0.05 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0085] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 10℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0086] (5) The calcined product was mixed with 0.1 mL of octadecyltrimethoxysilane (mixed at a mass ratio of 5:1) and heated in a constant temperature water bath at 90 °C for 1 h. The mixture was then centrifuged at 8000 r for 10 min, washed three times alternately with anhydrous ethanol and deionized water, and dried in an oven at 80 °C for 6 h to obtain the hollow porous silica hydrophobic microspheres of the product.

[0087] Example 2

[0088] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 1 in that, in step (1), the diameter of the polystyrene microspheres is 500 nm, while the other steps are the same as in Example 1.

[0089] Example 3

[0090] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 2 in that, in step (2), 40 mL of anhydrous ethanol and 40 mL of deionized water are mixed as solvents, while the other steps are the same as in Example 2.

[0091] Example 4

[0092] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 3 in that, in step (2), 1 mL of ammonia water (concentration 25wt%) is added under stirring, while the other steps are the same as in Example 3.

[0093] Example 5

[0094] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 4 in that, in step (2), 1g of hexadecyltrimethylammonium bromide is added, while the other steps are the same as in Example 4.

[0095] Example 6

[0096] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 2 in that, in step (2), 0.5 g of hexadecyltrimethylammonium bromide is added; in step (3), 0.2 mL of pore-expanding agent 1,3,5-trimethylbenzene is added to the mixed solution under magnetic stirring; 0.5 mL of tetraethyl orthosilicate is added dropwise at a rate of 0.1 mL / min; the mixture is magnetically stirred for 24 h to allow it to react fully and obtain a white reaction product; in step (4), the temperature is raised to 550 °C at a rate of 2 °C / min in a muffle furnace and calcined for 3 h; the other steps are the same as in Example 2.

[0097] The specific preparation steps are as follows:

[0098] (1) Disperse 5 mL of polystyrene microspheres with a diameter of 500 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol, add them into a 150 mL beaker, and sonicate for 10 min to obtain a polystyrene microsphere dispersion.

[0099] (2) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker. Add the hard template dispersion to the reaction solvent and stir magnetically for 10 min. Add 2 mL of ammonia water while stirring to adjust the alkalinity of the solution. Add 0.5 g of cetyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution.

[0100] (3) Under magnetic stirring, add 0.2 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; then add 0.5 mL of tetraethyl orthosilicate dropwise at a rate of 0.1 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0101] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 2℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0102] (5) The calcined product and octadecyltrimethoxysilane were heated in a constant temperature water bath at 90°C for 1 hour at a ratio of 5:1. The mixture was then centrifuged at 8000r for 10 minutes, washed three times alternately with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 6 hours to obtain hollow porous silica hydrophobic microspheres.

[0103] Example 7

[0104] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that, in step (2), a poly(ethylene oxide-poly(propylene oxide-poly(ethylene oxide)) triblock copolymer is used to replace hexadecyltrimethylammonium bromide in equal amounts, while the other preparation methods are the same as in Example 6.

[0105] Example 8

[0106] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that, in step (4), the temperature is increased to 650°C at a rate of 2°C / min in a muffle furnace and calcined for 6 hours; the other preparation methods are the same as in Example 6.

[0107] Example 9

[0108] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that, in step (5), hexadecyltrimethoxysilane is used to replace octadecyltrimethoxysilane in an equal amount; the other preparation methods are the same as in Example 6.

[0109] Example 10

[0110] A method for preparing hollow porous silica hydrophobic microspheres is the same as in Example 6, except that: in step (2), 0.2 g of hexadecyltrimethylammonium bromide (CTAB) is added; and in step (3), the amount of pore-expanding agent 1,3,5-trimethylbenzene is 0.1 mL. Other preparation methods are the same as in Example 6.

[0111] By adjusting the ratio of the soft template and the pore expander, the average pore size of the resulting microspheres is approximately 2.5 nm. This pore size facilitates the selective adsorption of low molecular weight aromatic hydrocarbon pollutants (such as benzene, toluene, and xylene), thereby achieving efficient removal of light aromatic oil stains.

[0112] Example 11

[0113] A method for preparing hollow porous silica hydrophobic microspheres is the same as in Example 6, except that: in step (2), 1 g of hexadecyltrimethylammonium bromide (CTAB) is added; and in step (3), the amount of pore-expanding agent triisopropylbenzene is 1 mL. Other preparation methods are the same as in Example 6.

[0114] By increasing the concentration of the soft template and the pore expander, a regular macroporous structure is formed, resulting in microspheres with an average pore size of approximately 6.0 nm. This pore size range is suitable for adsorbing straight-chain or branched saturated hydrocarbons (such as diesel and lubricating oil), exhibiting selective adsorption capacity for medium-sized oil contaminants.

[0115] Example 12

[0116] A method for preparing hollow porous silica hydrophobic microspheres is the same as in Example 6, except that in step (2), 1 g of PEO-PPO-PEO triblock copolymer (molecular weight 5000 Da, PEO content of blocks approximately 50%) is used instead of CTAB; and in step (3), the amount of pore-expanding agent polypropylene glycol (molecular weight 2000 Da) is 2 mL. Other preparation methods are the same as in Example 6.

[0117] Hollow microspheres with an average pore size of approximately 9.0 nm were obtained through the synergistic effect of a macromolecular soft template and a polypropylene glycol pore expander. This pore size enables the effective selective adsorption of macromolecular organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and heavy oil pollutants, making it suitable for the remediation of complex marine oil spills or high-viscosity oil pollution.

[0118] Comparative Example 1

[0119] A method for preparing hollow porous silica hydrophobic microspheres includes the following steps:

[0120] (1) Disperse 5 mL of polystyrene microspheres with a diameter of 500 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol, add them into a 150 mL beaker, and sonicate for 10 min to obtain a polystyrene microsphere dispersion.

[0121] (2) Mix 40 mL of anhydrous ethanol and 40 mL of deionized water as a solvent and add it to a 150 mL beaker. Add the hard template dispersion to the reaction solvent and stir magnetically for 10 min. Add 1 mL of ammonia water while stirring to adjust the alkalinity of the solution. Add 1 g of hexadecyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution.

[0122] (3) Under magnetic stirring, add 1 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; then add 2 mL of tetraethyl orthosilicate dropwise at a rate of 0.01 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0123] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 10℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0124] (5) The calcined product and octadecyltrimethoxysilane were heated in a constant temperature water bath at 90°C for 1 hour at a ratio of 5:1. The mixture was then centrifuged at 8000r for 10 minutes, washed three times alternately with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 6 hours to obtain hollow porous silica hydrophobic microspheres.

[0125] Comparative Example 2

[0126] A method for preparing hollow porous silica hydrophobic microspheres includes the following steps:

[0127] (1) Disperse 5 mL of PMMA microspheres (Guankemai New Materials) with a diameter of 500 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol, add them into a 150 mL beaker, and ultrasonically disperse for 10 min to obtain polymethyl methacrylate microsphere dispersion.

[0128] (2) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker. Add the hard template dispersion to the solvent and stir magnetically for 10 min. Add 2 mL of ammonia water while stirring to adjust the alkalinity of the solution. Add 0.5 g of cetyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution.

[0129] (3) Under magnetic stirring, add 0.2 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; then add 0.5 mL of tetraethyl orthosilicate dropwise at a rate of 0.1 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0130] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 2℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0131] (5) The calcined product and octadecyltrimethoxysilane were heated in a constant temperature water bath at 90°C for 1 hour at a ratio of 5:1. The mixture was then centrifuged at 8000r for 10 minutes, washed three times alternately with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 6 hours to obtain hollow porous silica hydrophobic microspheres.

[0132] Comparative Example 3

[0133] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that polystyrene microsphere dispersion is not added in step (2), i.e., step (1) is omitted. The other preparation methods are the same as in Example 6, specifically including the following steps:

[0134] (1) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker. Add 2 mL of ammonia water while stirring to adjust the alkalinity of the solution. Add 0.5 g of cetyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution.

[0135] (2) Under magnetic stirring, add 0.2 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; then add 0.5 mL of tetraethyl orthosilicate dropwise at a rate of 0.1 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0136] (3) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 2℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0137] (4) The calcined product and octadecyltrimethoxysilane were heated in a constant temperature water bath at 90°C for 1 hour at a ratio of 6:1. The mixture was then centrifuged at 8000r for 10 minutes, washed three times with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 6 hours to obtain hollow porous silica hydrophobic microspheres.

[0138] Comparative Example 4

[0139] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that step (2) does not involve the addition of hexadecyltrimethylammonium bromide. The other preparation methods are the same as in Example 6, specifically including the following steps:

[0140] (1) Disperse 5 mL of polystyrene microspheres with a diameter of 500 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol, add them into a 150 mL beaker, and sonicate for 10 min to obtain a polystyrene microsphere dispersion.

[0141] (2) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker. Add the hard template dispersion to the reaction solvent and stir magnetically for 10 min. Add 2 mL of ammonia water while stirring to adjust the alkalinity of the solution to obtain a mixed solution.

[0142] (3) Under magnetic stirring, add 0.2 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; then add 0.5 mL of tetraethyl orthosilicate dropwise at a rate of 0.1 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0143] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 2℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0144] (5) The calcined product and octadecyltrimethoxysilane were heated in a constant temperature water bath at 90°C for 1 hour at a ratio of 5:1. The mixture was then centrifuged at 8000r for 10 minutes, washed three times alternately with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 6 hours to obtain hollow porous silica hydrophobic microspheres.

[0145] Comparative Example 5

[0146] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that step (3) does not involve the addition of pore-expanding agent 1,3,5-trimethylbenzene. The other preparation methods are the same as in Example 6, specifically including the following steps:

[0147] (1) Disperse 5 mL of polystyrene microspheres with a diameter of 500 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol, add them into a 150 mL beaker, and sonicate for 10 min to obtain a polystyrene microsphere dispersion.

[0148] (2) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker. Add the hard template dispersion to the reaction solvent and stir magnetically for 10 min. Add 2 mL of ammonia water while stirring to adjust the alkalinity of the solution. Add 0.5 g of cetyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution.

[0149] (3) Under magnetic stirring, 0.5 mL of tetraethyl orthosilicate was added dropwise to the mixed solution at a rate of 0.1 mL / min; the mixture was magnetically stirred for 24 h to allow it to react fully and a white reaction product was obtained.

[0150] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, put the washed product into an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at 2℃ / min in a muffle furnace, calcine for 3h, wait for the muffle furnace to cool to room temperature, take it out, and obtain a white calcined product.

[0151] (5) The calcined product and octadecyltrimethoxysilane were heated in a constant temperature water bath at 90°C for 1 hour at a ratio of 5:1. The mixture was then centrifuged at 8000r for 10 minutes, washed three times alternately with anhydrous ethanol and deionized water, and dried in an oven at 80°C for 6 hours to obtain hollow porous silica hydrophobic microspheres.

[0152] Comparative Example 6

[0153] A method for preparing hollow porous silica hydrophobic microspheres differs from Example 6 in that step (5) is omitted. The other preparation methods are the same as in Example 6, specifically including the following steps:

[0154] (1) Disperse 5 mL of polystyrene microspheres with a diameter of 500 nm and a concentration of 10 wt% into 50 mL of anhydrous ethanol, add them into a 150 mL beaker, and sonicate for 10 min to obtain a polystyrene microsphere dispersion.

[0155] (2) Mix 40 mL of anhydrous ethanol and 10 mL of deionized water as a solvent and add it to a 150 mL beaker. Add the hard template dispersion to the reaction solvent and stir magnetically for 10 min. Add 2 mL of ammonia water while stirring to adjust the alkalinity of the solution. Add 0.5 g of cetyltrimethylammonium bromide and stir magnetically for 10 min to obtain a mixed solution.

[0156] (3) Under magnetic stirring, add 0.2 mL of pore-expanding agent 1,3,5-trimethylbenzene to the mixed solution; then add 0.5 mL of tetraethyl orthosilicate dropwise at a rate of 0.1 mL / min; stir magnetically for 24 h to allow it to react fully and obtain a white reaction product.

[0157] (4) Centrifuge at 8000r for 10min, wash with anhydrous ethanol and deionized water alternately, and dry the washed product in an oven at 80℃ for 6h; put the dried product into a crucible, heat it to 550℃ at a rate of 2℃ / min in a muffle furnace, calcine for 3h, and take it out after the muffle furnace cools down to room temperature to obtain a white calcined product.

[0158] II. Performance Verification

[0159] Figure 1 , Figure 2 The images shown are low-magnification and high-magnification scanning electron microscope (SEM) images of the hollow porous silica hydrophobic microspheres prepared in Example 1 of this invention. Figure 1 and Figure 2 It is evident that the sample consists of numerous nanospheres or spherical particles, which stack together to form porous aggregates. High-magnification images further confirm the presence of pores on the particle surface, indicating that the material may possess a hierarchical porous structure (inter-particle pores + particle surface pores). This morphology is advantageous in terms of contrasting surface area, adsorption performance, or subsequent modifications (such as hydrophobic modification).

[0160] Figure 3 and Figure 4 The images shown are scanning electron microscope (SEM) images at low and high magnification of the hollow porous silica hydrophobic microspheres prepared in Example 6 of this invention. Figure 3 and Figure 4As can be seen, the image shows a large number of aggregates of spherical nanoparticles. These particles are irregularly clustered, with an overall structure resembling a bunch of grapes. There are obvious gaps between the particles, forming a relatively loose porous morphology. The surface is relatively smooth but has a slightly rough feel. More internal cavities are visible in the cluster structure, and the slightly rough surface texture indicates that the material has higher porosity and potential shell features.

[0161] and Figure 1 - Figure 2 compared to, Figure 3 and Figure 4 The aggregates are more loose and porous, with increased interparticle spacing, and Figure 4 Holes or hollow structures appear within. This leads to... Figure 3 and Figure 4 The material has higher porosity and a more open structure, while Figure 1 and Figure 2 More dense and solid. Figure 3 Loose aggregation and Figure 4 The porous / hollow structure significantly increases the specific surface area of ​​the material. The constructed mesoporous or macroporous channels facilitate molecular / ion diffusion, thereby enhancing catalytic activity or adsorption capacity.

[0162] Figure 5 This is a transmission electron microscope (TEM) image of the hollow porous silica hydrophobic microspheres prepared in Example 6 of this invention. Figure 5 As can be seen, multiple spherical microspheres aggregate into clusters, with individual microspheres having a diameter of approximately 500 nm (according to the scale bar). These microspheres exhibit a hollow structure with clear boundaries, and the interior shows darker hollow regions, indicating the presence of hollow cavities. The microsphere surface is porous, with a relatively uniform pore distribution and a slightly rough surface texture, indicating high porosity. These characteristics suggest that the material has a high specific surface area, making it suitable for applications such as adsorption, catalysis, or drug delivery.

[0163] Figure 6 and Figure 7 The images show the Fourier transform infrared (FTIR) spectra of the hollow porous silica microspheres prepared in Example 6 of this invention before and after hydrophobic modification. The FTIR spectra of hollow porous silica microspheres typically exhibit the following characteristics: approximately 1100 cm⁻¹ -1 The strong absorption peak is attributed to the Si-O-Si asymmetric stretching vibration; approximately 800 cm⁻¹ -1 The weaker peak is attributed to Si-O symmetric stretching; approximately 470 cm⁻¹ -1 The peak is attributed to the Si-O-Si bending vibration. Additionally, the peak at approximately 3400 cm⁻¹ is... -1 The presence of a broad -OH stretching vibration peak indicates the presence of numerous hydroxyl groups (-OH) on the surface, which is related to the hydrophilicity of silica; approximately 1630 cm⁻¹ -1The weak peak may correspond to adsorbed water molecules. After hydrophobic modification (such as silanization using methyltrimethoxysilane or similar reagents), the -OH stretching vibration peak (3400 cm⁻¹) in the spectrum will be more prominent. -1 The surface hydroxyl groups should be significantly weakened or disappear, indicating that they have been replaced by hydrophobic groups (such as -CH3 or -CH2-). Meanwhile, approximately 2900-3000 cm⁻¹ -1 New CH stretching vibration peaks may appear, reflecting the introduction of alkyl chains. In addition, the Si-O-Si peaks may change slightly, but remain generally intact, indicating that the silicon-oxygen framework is not damaged.

[0164] Depend on Figure 6 and Figure 7 The comparison revealed that the weakening or disappearance of the -OH-related peaks after hydrophobic modification was the main change, and the appearance of CH stretching vibrations was direct evidence of enhanced hydrophobicity. This indicates that the modification successfully reduced the surface energy of the material, enhanced its hydrophobicity, and may improve its stability or dispersibility in organic solvents or nonpolar environments, making it suitable for applications such as oil-water separation, hydrophobic coatings, or drug sustained release.

[0165] Figure 8 This refers to the water contact angle of the hollow porous silica microspheres prepared in Examples 1-6 of this invention, after hydrophobic modification, sprayed onto a glass substrate. Figure 8 It can be seen that the water contact angle of the hollow porous silica microspheres prepared in Example 6, after hydrophobic modification and spraying onto the glass substrate, is up to 140.95°. This indicates that a stable hydrophobic layer is formed on the surface of the microspheres after modification with long-chain alkylsilanes (C18), and its low surface energy characteristics enable the microspheres to exhibit high affinity for non-polar organic pollutants in water (such as polycyclic aromatic hydrocarbons, organochlorine pesticides, mineral oils, etc.).

[0166] The specific surface area, pore volume, average pore diameter, average particle size, shell thickness, and other properties of the hollow porous hydrophobic spherical shells obtained in the embodiments and comparative examples of the present invention are shown in Table 1.

[0167] Table 1 Performance Comparison

[0168]

[0169] As can be seen from the data in Table 1, the specific surface area of ​​Examples 1-9 ranges from 467 to 621 m². 2 / g, pore volume ranges from 0.225 to 0.396 cm³. 3 / g, of which Example 6 (specific surface area 620 m²) 2 / g, pore volume 0.396 cm³ 3 / g) and Example 9 (621 m) 2 / g, 0.386 cm 3 The ( / g) ratio performed best, significantly outperforming the comparative (233-584 m). 2 / g, 0.214-0.386 cm 3 / g). Example 6 achieved the effective construction of a hierarchical pore structure (hollow cavity + mesopore) by optimizing the dosage of hard template (500 nm polystyrene microspheres), soft template (0.5 g CTAB), pore expander (0.2 mL TMB), and tetraethyl orthosilicate (0.5 mL), providing highly active sites and storage space for adsorption and catalytic applications. Comparative Example 3 (233 m 2 / g) and Comparative Example 2 (339 m 2 The lowest specific surface area ( / g) was due to insufficient development of hollow structures or pores, caused by the absence of a hard template and the use of a PMMA template, respectively. Comparative Example 5 (0.214 cm⁻¹) 3 (g) Due to the omission of the pore expander, the pore volume was significantly lower than in Example 6, indicating that the pore expander is crucial for improving pore capacity.

[0170] The average pore size of Examples 1-9 ranged from 2.10 to 10.21 nm, all falling within the mesoporous range, suitable for molecular diffusion and adsorption. Examples 6 (4.01 nm) and 8 (4.37 nm) exhibited moderate pore sizes, combined with high specific surface area and pore volume, demonstrating excellent structural balance, which is beneficial for the transport and storage of non-polar pollutants. Example 7 (10.21 nm) showed a significantly increased pore size due to the use of a PEO-PPO-PEO soft template, but the pore regularity decreased, affecting adsorption efficiency. Comparative Example 5 (2.01 nm) lacked a pore-expanding agent, resulting in an excessively small pore size that limited molecular diffusion, leading to lower pore volume and specific surface area. Comparative Examples 3 and 4 lacked either a hard or soft template, resulting in disordered pore structures, making it impossible to effectively measure pore size data.

[0171] The average particle size range of Examples 1-9 is 436-543 nm, consistent with the hard template size (400 nm or 500 nm), indicating that the hard template effectively controls the uniformity of microsphere morphology. Examples 6 (513 nm) and 9 (522 nm) have stable particle sizes and uniform structures. The shell thickness ranges from 15.6 to 46.1 nm, with Example 6 (20.4 nm) having a moderate thickness, ensuring a balance between mechanical strength and porosity. Example 4 (46.1 nm) has the thickest shell, possibly due to excessive silica deposition caused by a low ammonia content (1 mL), affecting pore connectivity. Comparative Example 2 (12.3 nm) has the thinnest shell, reflecting the low deposition efficiency of the PMMA template, while Comparative Example 3 could not form a regular shell due to the lack of a hard template.

[0172] The contact angles of Examples 1-9 ranged from 102.4° to 141.2°, all exhibiting excellent hydrophobicity (90°). Examples 6 (140.9°) and 8 (141.2°) showed the highest contact angles, indicating that the hydrophobic modification of octadecyltrimethoxysilane and optimized calcination conditions (Example 8: 650°C, 6 h) effectively reduced the surface hydroxyl density and enhanced the affinity for non-polar pollutants. Comparative Example 6 (61.2°) lacked hydrophobic modification, resulting in a hydrophilic surface, severely limiting its application in oily wastewater treatment. While Comparative Examples 1-5 exhibited hydrophobic contact angles (119.3°-131.5°), their lower contact angles compared to Example 6 were due to insufficient pore structure or inadequate surface modification efficiency.

[0173] Example 6 achieved a high specific surface area (620 m²) through synergistic optimization of hard templates (PS microspheres), soft templates (CTAB), pore expanders (TMB), and hydrophobic modification (octadecyltrimethoxysilane). 2 / g), macropore volume (0.396 cm³) 3 It exhibits a combination of properties including a g / g density, moderate pore size (4.01 nm), and excellent hydrophobicity (140.9°). Comparative Example 3, lacking PS microspheres, resulted in the absence of a hollow structure and a sharp decrease in specific surface area (233 m² / g). 2 / g). Comparative Example 4 omits CTAB, has disordered mesoporous structure, and a specific surface area of ​​(466 m²). 2 / g) and limited pore volume. Comparative Example 5 had no TMB, but the pore size was too small (2.01 nm) and the pore volume (0.214 cm³) was limited. 3 The contact angle ( / g) was significantly reduced. Comparative Example 6, without octadecyltrimethoxysilane modification, had a contact angle of only 61.2°, making it unsuitable for the adsorption of non-polar pollutants. Comparative Example 1 (slow dropping rate 0.01 mL / min) and Comparative Example 2 (PMMA template) showed that the dropping rate and template material selection significantly affected pore development and structural integrity.

[0174] Furthermore, Examples 10–12 demonstrate a novel feature of achieving controllable pore size through precise adjustment of the soft template and pore-expanding agent dosage. Example 10 exhibits an average pore size of approximately 2.5 nm and a specific surface area of ​​580 m². 2 / g, pore volume 0.310 cm³ 3 / g, exhibiting a selective advantage for small molecule aromatic hydrocarbons; the average pore size of Example 11 is approximately 6.0 nm, and the specific surface area is 605 m² / g. 2 / g, pore volume 0.355 cm³ 3 / g, suitable for the adsorption of medium-chain hydrocarbons; the average pore size of Example 12 is approximately 9.0 nm, and the specific surface area is 590 m². 2 / g, pore volume 0.380 cm³ 3The microspheres exhibited the best performance in adsorbing polycyclic aromatic hydrocarbons (PAHs) and heavy oil pollutants. The contact angles for all three components were between 136.5° and 139.8°, maintaining excellent hydrophobicity. This indicates that by adjusting the ratio of the soft template to the pore-expanding agent, hollow porous microspheres with different pore size distributions can be obtained, thereby achieving efficient and selective adsorption of oil contaminants of specific sizes.

[0175] Example 7 differs from Example 6 in that an equal amount of hexadecyltrimethylammonium bromide (CTAB) was replaced with a poly(ethylene oxide-polypropylene oxide-polyethylene oxide) triblock copolymer. The reason for the performance difference compared to Example 6 is that CTAB is a cationic surfactant with a small molecular size and a single hydrophobic tail chain (hexadecyl), forming a regular micelle structure in solution, which helps to generate small and uniform mesopores (4.01 nm). In contrast, the PEO-PPO-PEO triblock copolymer is a high-molecular-weight surfactant with a larger molecular weight (4000-15000 Da), and its alternating hydrophilic (PEO) and hydrophobic (PPO) blocks form larger micelles or complex aggregates. The size and looseness of this micelle structure result in a significantly increased pore size (10.21 nm) in Example 7, falling within the range of mesopores transitioning to macropores, and reducing the regularity of the pores. Example 7 used a PEO-PPO-PEO triblock copolymer as a soft template, resulting in a significant increase in pore size (10.21 nm), but decreased pore regularity, reduced specific surface area and pore volume, and slightly weakened hydrophobicity. CTAB has greater advantages in forming uniform mesopores and optimizing microsphere structures.

[0176] Example 8 differs from Example 6 in that the temperature was increased to 650°C at a rate of 2°C / min in a muffle furnace and calcined for 6 hours. The difference in performance compared to Example 6 is due to the higher calcination temperature (650°C vs 550°C) and longer holding time (6 hours vs 3 hours), which may lead to slight rearrangement of the silica framework or localized sintering of the pore walls. This sintering effect may cause some small pores to merge, forming slightly larger pore sizes (4.37 nm vs 4.01 nm), while reducing the openness of the pores, resulting in a smaller specific surface area (612 m²). 2 / g vs 620 m 2 / g) and pore volume (0.378 cm³) 3 / g vs 0.396 cm 3The pore size ( / g) decreased slightly. Higher calcination temperatures and longer holding times ensured complete removal of both the hard template (polystyrene microspheres) and the soft template (CTAB), potentially resulting in more open pores and a slight increase in the contact angle (141.2° vs 140.9°). This suggests that the hydrophobic modification effect of Example 8 may be slightly enhanced due to a cleaner surface with fewer residual hydroxyl groups, which is beneficial for the grafting of long-chain alkylsilanes. Example 8, using a higher calcination temperature (650°C) and a longer holding time (6 h), resulted in a slight increase in pore size, a slight decrease in specific surface area and pore volume, but a slight improvement in hydrophobicity. The calcination conditions of Example 6 (550°C, 3 h) were superior in maintaining high specific surface area and pore volume, indicating that they were the better process parameters.

[0177] Example 9 differs from Example 6 in that hexadecyltrimethoxysilane is used in an equal amount to replace octadecyltrimethoxysilane. The reason for the performance difference compared to Example 6 is that the alkyl chain of hexadecyltrimethoxysilane (hexadecyl) is two carbon atoms shorter than that of octadecyltrimethoxysilane (octadecyl). The shorter alkyl chain reduces the low surface energy characteristics of the hydrophobic modified layer, resulting in a slightly lower contact angle (130.1° vs 140.9°). Although both contact angles indicate excellent hydrophobicity (120°), the longer chain of octadecyltrimethoxysilane provides a stronger nonpolar shielding effect, enhancing the affinity of the microspheres for nonpolar contaminants.

[0178] Furthermore, Example 10 obtained microspheres with an average pore size of approximately 2.5 nm by reducing the amount of pore expander, exhibiting high selectivity for small molecule aromatic hydrocarbons such as benzene; Example 11 achieved a pore size of approximately 6.0 nm by increasing the concentration of the soft template and pore expander, demonstrating stronger compatibility in treating medium-chain hydrocarbon pollutants; Example 12 obtained microspheres with an average pore size of approximately 9.0 nm by using the synergistic effect of a macromolecular soft template and pore expander, exhibiting the strongest selectivity in adsorbing polycyclic aromatic hydrocarbons and high-viscosity heavy oil pollutants.

[0179] The particle sizes of Comparative Examples 1 and 2 were 522 nm and 509 nm, respectively, with no obvious abnormalities, indicating that the particle size distribution remained stable in the method of this invention. The shell thickness in Examples 1-6 ranged from 18.2 nm to 30.5 nm, demonstrating the controllability of shell growth during the preparation process. The shell thickness of Example 6 was 20.4 nm, which was moderate and uniform. Combined with its high specific surface area and pore volume, this indicated the best structural optimization effect. The specific surface area of ​​the comparative examples (418 nm) was... 2 / g) and pore volume (0.112 cm³) 3The concentrations of g) were all lower than in Example 6, and the dropping speed of tetraethyl orthosilicate was too slow (0.01 mL / min), which may have led to incomplete reaction and insufficient pore development. Comparative Example 2 used PMMA microspheres as a template, with a specific surface area (339 m²). 2 / g) and pore volume (0.081 cm³) 3 The thickness of the shell layer is only 12.3 nm, which is further reduced by 1 g, indicating that the choice of template material has a significant impact on the structure formation. Polystyrene templates are more advantageous in this invention.

[0180] Compared with Example 6, Comparative Example 3 omits the addition of polystyrene microsphere dispersion in step (2), i.e., step (1) is omitted. The reason for the performance difference from Example 6 is that Example 6 uses polystyrene microspheres (PS, 500 nm) as a hard template, providing a stable framework for the formation of the hollow structure and ensuring that silica is deposited on the template surface to form hollow cavities. Comparative Example 3 omits the hard template and relies only on the CTAB soft template, resulting in a lack of a clear morphology control framework. The reaction product may form disordered porous silica aggregates instead of a hollow microsphere structure. This directly leads to a significant reduction in specific surface area (233 m²). 2 / g vs620 m 2 The inability to effectively measure pore volume and pore size indicates severe impairment of structural regularity and porosity. In Example 6, the rigid template (PS microspheres) guided the ordered deposition of silica through its uniform spherical structure, combined with the mesoporous structure formed by CTAB, achieving a multi-level pore structure (hollow cavity + mesopore). In Comparative Example 3, relying solely on the micellar effect of CTAB, the resulting pores may be disordered mesopores or aggregated pores, lacking hollow cavities, leading to a significant decrease in pore volume and specific surface area, limiting the material's application potential in adsorption and catalysis. Comparative Example 3, by omitting the rigid template (polystyrene microspheres), could not form a hollow structure, resulting in a significant decrease in specific surface area, pore volume, and pore size, and weakened hydrophobicity. The rigid template is crucial in ensuring the hollow morphology and structural integrity.

[0181] Compared to Example 6, Comparative Example 4 did not add cetyltrimethylammonium bromide in step (2). The reason for the difference in performance compared to Example 6 is that CTAB, acting as a soft template, formed micelles in Example 6, guiding silica to form a regular mesoporous structure (average pore size 4.01 nm). Comparative Example 4 omitted CTAB, resulting in a lack of micelle-guided ordered pore formation. The product may only rely on a hard template (PS microspheres) to form a hollow structure, but lacks mesopores, leading to a lower specific surface area (466 m²). 2 / g vs 620 m 2 The pore volume ( / g) and pore size were significantly reduced, and pore size data could not be effectively measured. In Example 6, CTAB enhanced the regularity and openness of the pores through its micellar effect, contributing to an increase in pore volume (0.396 cm³). 3(g) and specific surface area. Comparative Example 4, relying solely on a hard template and pore expander, exhibits a relatively disordered pore structure and poor pore connectivity, limiting molecular diffusion and adsorption performance, thus affecting the subsequent hydrophobic modification effect (contact angle 126.9° vs 140.9°). Comparative Example 4, by omitting the soft template CTAB, suffers from a lack of mesoporous structure, resulting in a significant decrease in specific surface area and pore volume, and weakened hydrophobicity. CTAB is indispensable for forming regular mesopores and improving porosity.

[0182] Compared to Example 6, Comparative Example 5 did not add the pore-expanding agent 1,3,5-trimethylbenzene in step (3). The reason for the difference in performance compared to Example 6 is that TMB, in Example 6, acted as a pore-expanding agent, embedding itself in the CTAB micelles to enlarge the micelle size, thereby increasing the pore size (4.01 nm). Comparative Example 5 omitted TMB, resulting in a smaller micelle size and the formation of only small mesopores (2.01 nm). The smaller pore size limited the openness of the pores and the molecular diffusion ability, significantly reducing the pore volume (0.214 cm⁻¹). 3 / g vs 0.396cm 3 / g) and specific surface area (495 m²) 2 / g vs 620 m 2 The smaller pore size and lower pore volume reduce the active sites of the microspheres, limiting the grafting efficiency of long-chain alkyl silanes in subsequent hydrophobic modification, resulting in a decreased contact angle (131.5° vs 140.9°). The absence of a pore expander makes the pore structure too dense, which is not conducive to the adsorption and diffusion of non-polar pollutants. Comparative Example 5, due to the omission of the pore expander TMB, resulted in a reduction in pore size, a significant decrease in pore volume and specific surface area, and a weakening of hydrophobicity. TMB plays a key role in regulating pore size and improving porosity.

[0183] Compared with Example 6, Comparative Example 6 omits step (5), resulting in a large number of hydroxyl groups (-OH) remaining on the surface of the microspheres, exhibiting hydrophilicity (contact angle 61.2°), which is unfavorable for the adsorption of non-polar pollutants and severely limits its application in the adsorption of pollutants in water. The specific surface area of ​​Comparative Example 6 (584 m²) 2 / g) and pore volume (0.386 cm³) 3 / g) slightly lower than Example 6 (620 m) 2 / g, 0.396cm 3The hydrophobic modification process (water bath heating, centrifugation, washing) may have a slight optimizing effect on the pore structure, such as removing a small amount of residual impurities or adjusting the pore wall surface. The average pore size (4.11 nm vs 4.01 nm) did not change much, indicating that the hydrophobic modification had a limited impact on the pore size. Comparative Example 6, due to the omission of hydrophobic modification, resulted in a hydrophilic surface on the microspheres (contact angle 61.2°), which seriously affected its performance in the adsorption of non-polar pollutants. Hydrophobic modification is a key step in achieving excellent hydrophobicity and application effects.

[0184] As shown in Table 1, the hollow porous silica hydrophobic microspheres prepared in the various embodiments of the present invention exhibit significant differences in structural parameters such as specific surface area, pore volume, and pore size. Different pore size distributions and shell thicknesses have a direct impact on the adsorption characteristics of the microspheres.

[0185] Application examples

[0186] To further verify the application advantages of this invention, which achieves precise pore size control by adjusting the amount of soft template and pore expander, the inventors systematically evaluated the performance of different embodiments and comparative samples in adsorbing different types of oil contaminants. To verify the selective adsorption performance of the hollow porous silica hydrophobic microspheres of this invention, batch adsorption experiments were conducted on different oil contaminants (benzene, hexadecane, anthracene) using microspheres prepared in Examples 1–12 and Comparative Examples 1–6. The standard experimental conditions were: wastewater volume 1.0 L, initial oil concentration 1000 mg·L⁻¹. -1 The microsphere dosage was 0.1 wt% (1.0 g). The mixture was stirred rapidly at 300 rpm for 3 min at room temperature (25 ℃), followed by contact stirring at 150 rpm for 60 min. Solid-liquid separation was performed by centrifugation (8000 rpm, 10 min), and residual oil was determined by dichloromethane extraction-weighing method. All data are the average of three parallel experiments. This method can reproduce the selective adsorption data given in Table 2 and can be used to calculate the selectivity coefficient S. Tested contaminants included benzene (representing small-molecule aromatic hydrocarbons), hexadecane (representing medium-chain hydrocarbons, such as diesel and lubricating oils), and anthracene (representing large-molecule polycyclic aromatic hydrocarbons and heavy oils). See Table 2.

[0187] For ease of comparison, a "selectivity coefficient" is introduced as an evaluation index, which is defined as:

[0188]

[0189] in, The adsorption capacity of the material for the target pollutant. This represents the average adsorption capacity of the material for the other two pollutants. A higher selectivity coefficient indicates a stronger selectivity of the material for the target pollutant.

[0190] Table 2 Comparison of High Selectivity Adsorption Performance

[0191]

[0192] As shown in Table 2, Examples 1–12 of this invention, by precisely controlling the amount and concentration of the soft template and pore-expanding agent, achieved controllable adjustment of the pore size within the range of 2-10 nm while maintaining a large specific surface area. This resulted in the microspheres exhibiting significant selectivity in the adsorption of oil pollutants of different sizes. Specifically, Example 10 showed selectivity coefficients greater than 3.0 for benzene, Example 11 for hexadecane, and Example 12 for anthracene. This result directly demonstrates the effectiveness of the "pore size control for highly selective adsorption" technique proposed in this invention, overcoming the shortcomings of indiscriminate adsorption in traditional adsorption materials.

[0193] In summary, this invention achieves optimal performance of hollow porous silica hydrophobic microspheres by optimizing preparation conditions. Their high specific surface area and large pore volume give them broader application prospects in fields such as catalysts and pollutant adsorption.

[0194] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating oily wastewater, characterized in that, Hollow porous silica hydrophobic microspheres are added to oily wastewater; the oily wastewater contains one or more of aromatic hydrocarbons, medium-chain hydrocarbons, and polycyclic aromatic hydrocarbons; the aromatic hydrocarbon is benzene; the medium-chain hydrocarbon is hexadecane; and the polycyclic aromatic hydrocarbon is anthracene. The amount of the hollow porous silica hydrophobic microspheres added is 0.01-5 wt% of the total mass of the wastewater. The method for preparing the hollow porous silica hydrophobic microspheres includes the following steps: (1) Add the hard template dispersion to the solvent and stir to mix well. Add ammonia and soft template to obtain a mixture. (2) Add a pore-expanding agent to the mixture and add tetraethyl orthosilicate dropwise to react and obtain the product; The pore-expanding agent is 1,3,5-trimethylbenzene, triisopropylbenzene, or polypropylene glycol; (3) The product is calcined to obtain the calcined product; (4) The calcined product is reacted with organosiloxane in a water bath to obtain hollow porous silica hydrophobic microspheres. The hollow porous silica hydrophobic microspheres have a pore size of 2-10 nm, a porous silica layer thickness of 15.5-46.1 nm, and a pore volume of 0.225-0.396 cm³. 3 / g, specific surface area is 467-621 m² 2 / g; The contact angle of the hollow porous silica microspheres ranges from 102.4° to 141.2°.

2. The method for treating oily wastewater according to claim 1, characterized in that, In step (1), the concentration of the hard template dispersion is 5-10 wt%; the hard template is one or more of polystyrene microspheres or polymethyl methacrylate microspheres; the particle size of the hard template is 300-800 nm. The volume ratio of the hard template dispersion to the solvent is 1:(10-16). The solvent is a mixture of anhydrous ethanol and deionized water; the volume ratio of the anhydrous ethanol to the deionized water is (1-4):

1.

3. The method for treating oily wastewater according to claim 1, characterized in that, In step (1), the ammonia content in the mixture is 3wt%-7wt%; The concentration of the ammonia solution is 20 wt% - 25 wt%; The content of soft template in the mixture is 0.5wt%-1wt%; The soft template is one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

4. The method for treating oily wastewater according to claim 1, characterized in that, In step (2), the dropping rate is 0.05-0.1 mL / min; the reaction time is 24-30 h.

5. The method for treating oily wastewater according to claim 1, characterized in that, In step (3), before the calcination treatment, centrifugation, washing, and drying are performed in sequence; The washing process involves alternating between anhydrous ethanol and deionized water, with the number of washes exceeding 3. The drying temperature is 75-85℃ and the time is 5-7 hours; The calcination process involves a heating rate of 2-10℃ / min, an atmosphere of air, a temperature of 450-650℃, and a holding time of 3-6h.

6. The method for treating oily wastewater according to claim 1, characterized in that, In step (4), the water bath heating temperature is 60-90℃ and the time is 1-3h; The mass ratio of the calcined product to the organosiloxane is (4-10):1; The organosiloxane is one or more of octadecyltrimethoxysilane, octadecyltriethoxysilane, and hexadecyltrimethoxysilane.

7. The method for treating oily wastewater according to claim 1, characterized in that, The amount of hollow porous silica hydrophobic microspheres added is 0.05-1 wt% of the total mass of wastewater.

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