CN1480251A - Ferromagnetic porous silica gel microspheres and preparation method thereof - Google Patents

Abstract

The invention discloses a ferromagnetic porous silica gel microsphere and a preparation method thereof. The microspheres are microspheres with a specific surface area of 100-450m ² /g, a pore diameter of 5-15nm, a particle diameter of 0.5-20μm, and silicon dioxide as the base material. Composed of paramagnetic ferric oxide nanoparticles. The preparation process includes the preparation of iron oxide sol, the preparation of iron oxide/silicon dioxide mixed sol, the preparation of organic/inorganic composite microspheres, and the preparation of magnetic porous silica gel. The advantages and effects of the present invention are: the prepared microspheres have large specific surface area, uniform particle size, rich hydroxyl groups on the surface, can enhance adsorption selectivity through surface chemical modification, and are suitable as a chromatographic stationary phase or a carrier for catalytic reactions. The preparation process is simple, the conditions are easy to control, and the industrialization is easy to realize, and has potential application prospects in the magnetic field-controlled transfer process and separation method.

Description

Ferromagnetic porous silica gel microspheres and preparation method thereof

technical field

The invention relates to a method for preparing ferromagnetic porous silica gel microspheres, which belongs to the preparation technology of magnetic porous silica microspheres.

Background technique

Magnetic field-controlled delivery and separation systems have many applications in the fields of medicine, biology, and chemistry, and thus have been rapidly developed in recent years. In these systems, an external magnetic field is usually used to control the directional movement of magnetically responsive particles, so it can be used to release specific therapeutic drugs to a certain part of the body, selectively separate cancer cells from bone marrow cells, Extraction of target molecules from complex biological samples and other fields. The fluidized bed technology controlled by magnetic field has become a powerful tool in biotechnology. In the preparation and separation, the magnetic support medium can be immobilized relatively quickly, so as to facilitate the recovery of target molecules. In recent years, the construction of magnetic microfluidic devices has also attracted people's attention, because these devices can be used to facilitate the transfer of microspheres between storage, reaction, detection and other micro-cells, thus playing a role in the miniaturization and automation of analytical instruments. important role.

The success of the above-mentioned magnetic field-controlled delivery and separation systems depends largely on the availability of magnetic microspheres with special properties. Magnetic microspheres can be prepared by various methods, which can be roughly divided into three categories. In the first type of method, the colloid of magnetic iron oxide is directly deposited in the porous structure of cross-linked polystyrene microspheres or controlled pore glass microspheres, and then a layer of polymer is coated on the outer surface of the microspheres to prevent Iron oxide nanoparticles are lost during use. The second type of method is to attach a layer of magnetic nanoparticles to non-porous microspheres and wrap them with polymers to form magnetic microspheres with a core-shell structure. The third type of method is based on the dispersion polymerization of monomers in the presence of magnetic colloids, a one-step method to prepare magnetic microspheres.

All of the above-mentioned microspheres are commercially available, and there are also reports in the literature that nanometer-scale microspheres are prepared by mixing ferric salt and tetraethoxysilane (TEOS), and magnetic iron oxide-silicon dioxide composite microspheres are obtained after calcination. . The disadvantage is that these magnetic microspheres have a non-porous structure and a small specific surface area, so they are not suitable for application in chemical fields such as chromatographic separation and catalytic reaction.

Contents of the invention

The object of the present invention is to provide a ferromagnetic porous silica gel microsphere and its preparation method, the specific surface area of the microsphere is 100-450m ² /g, the pore diameter is 5-15nm, and the particle diameter is 0.5-20μm. The preparation method has simple process and easy control conditions.

The present invention is achieved through the following scheme, adopting superparamagnetic iron particles and using urea-formaldehyde resin as a template to prepare ferromagnetic porous silica gel microspheres, which are characterized in that the microspheres have a specific surface area of 100-450m ² /g, the pore size is 5-15nm, the particle size is 0.5-20μm, the silicon dioxide is the microsphere of the substrate, and the superparamagnetic ferric oxide nanoparticles are uniformly dispersed in the substrate.

The process of the preparation method of the above microspheres includes the preparation of iron oxide sol, the preparation of iron oxide/silicon dioxide mixed sol, the preparation of organic/inorganic composite microspheres, and the preparation of magnetic porous silica gel.

The present invention is achieved through the following specific reaction steps:

1. Mix FeCl ₃ .6H ₂ O and NaHCO ₃ with a molar ratio of 1-3.0, add water and stir to fully dissolve them.

2. Take an appropriate amount of silica sol, adjust the pH to 2.0-2.5 with an acid including concentrated nitric acid, and mix the iron oxide sol and silica sol according to the molar _ratio of _Fe2O3 to _SiO2 of 0.01-1.0.

3. Add urea and formaldehyde reaction monomers to the iron oxide/silicon dioxide mixed sol, the molar ratio is 1-1.5, and the percentage of inorganic components is controlled to 60%, at pH 1-4, at 5-50°C After reacting for 1-24 hours, the composite microspheres were collected by filtration.

4. The composite microspheres prepared by the above method are dried and calcined at 300-350°C, 600-650°C and 900-950°C for 2-5 hours respectively. Iron oxide phase changes to ferromagnetic porous silica microspheres at high temperature.

The preferred molar ratio of the aforementioned Fe ₂ O ₃ to SiO ₂ is 0.3-0.5.

The ferromagnetic porous silica gel microspheres prepared by the above method are surface-modified with a chlorooctyl silane reagent, and the ferromagnetic porous silica gel microspheres obtained by bonding hydrophobic chemical functional groups can be used as a reversed-phase magnetic chromatographic stationary phase.

The calcination step is extremely important in the above-mentioned preparation method process. The stepwise high-temperature calcination of the organic/inorganic composite microspheres prepared by the polymerization reaction can play three roles: removing the polymer template, inducing the iron oxide phase transition and enhancing the mechanical strength of the porous microspheres. First, burn the composite microspheres at 300-350°C to carbonize the urea-formaldehyde resin. Then the temperature is raised to 600-650°C for further calcination, and the organic components are completely volatilized to remove. Finally, increasing the heat treatment temperature to 900–950 °C not only enhances the mechanical strength of the porous inorganic oxide microspheres, but also promotes the phase transition of iron oxide from non-magnetic, amorphous iron oxide to magnetic iron oxide. Oxide microspheres calcined at high temperature can be attracted by permanent magnets, thus exhibiting macroscopic magnetic responsiveness.

Because the surface of the magnetic porous silica gel microsphere of the present invention contains a large amount of silicon hydroxyl groups and iron hydroxyl groups, it can not only be used as a reversed-phase magnetic chromatography stationary phase, but also can be directly used as a support for normal phase chromatography separation stationary phase or catalytic reaction; Silane reagents are used to modify the surface of silica gel microspheres and couple them with alkyl groups, amino groups, carboxyl groups or other selective interaction ligands to prepare magnetic high-performance liquid chromatography fillers that can be used in different separation modes.

Advantage and effect of the present invention are:

Provided is a magnetic silica gel microsphere with large specific surface area, high porosity, and rich hydroxyl groups on the surface, which can enhance adsorption selectivity through surface chemical modification, and is suitable as a chromatographic stationary phase or a carrier for catalytic reactions. The preparation method has the advantages of simple process, easy control of conditions, and easy realization of industrialization, and has potential application prospects in the magnetic field-controlled transfer process and separation method.

Description of drawings

Figure 1 is a scanning electron micrograph of porous _Fe2O3 / _SiO2 microspheres prepared in Example 1 of the present invention _;

Figure 2 is a hysteresis loop diagram of the _Fe2O3 / _SiO2 microspheres shown in Figure 1 at room _temperature ;

Fig. 3 is the chromatographic separation spectrogram of the standard sample mixture of the _Fe2O3 / _SiO2 porous microspheres prepared by Example 4 of the present invention after the _{C8 bonded} microspheres are fillers, and peak 1 is uracil ; Peak 2 is acetone; Peak 3 is 4-chloronitrobenzene; Peak 4 is naphthalene, chromatographic conditions: chromatographic column: 150 × 4.6mm; Mobile phase: 80% (v/v) methanol-water solution; Flow rate: 1ml/ min; UV detection: 254nm.

Detailed ways

Example 1: Synthesis of Magnetic Porous Microspheres

In a beaker containing 150ml of distilled water, add 21.5g FeCl ₃ .6H ₂ O and 15g NaHCO ₃ , stir to obtain a clear red iron sol with a pH of 2-2.5. In another beaker, add 225ml of silica sol (30%) and 16g of urea respectively, after stirring and dissolving, add concentrated HNO ₃ to adjust the pH to 1.5. Mix iron sol and silica sol while stirring, readjust the pH to 1.5, add 22ml of formaldehyde (37%) solution rapidly under stirring, stop stirring after mixing evenly, and let stand at room temperature overnight for reaction. The composite microspheres generated by the reaction were collected by centrifugation, washed with water, water-methanol (1:1), methanol and acetone in sequence. Drying under vacuum at 60°C overnight gave 31 g of free-flowing yellow microspheres. The composite microspheres are heat-treated and calcined at 300-350° C., 600-650° C. and 900-950° C. for 2 hours respectively. After the non-magnetic silica gel particles were removed by magnetic separation, 15 g of free-flowing brown-red magnetic microspheres were obtained. Calculated by weight percent of the oxide content in the mixed sol, the yield of the magnetic microspheres is 21%.

The characterization of the magnetic porous microspheres shows that the average particle size of the microspheres is 4 μm, the specific surface area is 150 m ² /g, the average pore size is 10 nm, and the weight percentage of iron oxide is 19%. The saturation calculated based on the normalization of iron oxide The magnetic susceptibility is 31.6emu/g.

Example 2: Synthesis of Magnetic Porous Microspheres

In a beaker containing 110ml of distilled water, respectively add 5.7g FeCl ₃ .6H ₂ O and 4.0g NaHCO ₃ , stir to obtain a clear red iron sol with a pH of 2-2.5. In another beaker, add 90ml of silica sol (30%) and 6.4g of urea respectively, after stirring and dissolving, add concentrated _HNO3 to adjust the pH to 1.5. Mix iron sol and silica sol while stirring, readjust the pH to 1.5, add 8.8ml formaldehyde (37%) solution quickly under stirring, stop stirring after mixing evenly, and let stand at room temperature overnight for reaction. The composite microspheres generated by the reaction were collected by centrifugation, washed with water, water-methanol (1:1), methanol and acetone in sequence. Drying under vacuum overnight at 60°C yielded 11.6 g of yellow microspheres. The composite microspheres are heat treated and calcined at 250-300° C., 500-550° C. and 850-900° C. for 1-2 hours respectively. After the non-magnetic silica gel particles were removed by magnetic separation, brown-red magnetic microspheres with an average particle diameter of 5 μm were obtained.

Example 3: Synthesis of Magnetic Porous Microspheres

In a beaker containing 110ml of distilled water, add 8.6g FeCl ₃ .6H ₂ O and 6.0g NaHCO ₃ , stir to obtain a clear red iron sol with a pH of 2-2.5. In another beaker, add 90ml of silica sol (30%) and 6.4g of urea respectively, after stirring and dissolving, add concentrated _HNO3 to adjust the pH to 1.5. Mix iron sol and silica sol while stirring, readjust the pH to 1.5, add 8.8ml formaldehyde (37%) solution quickly under stirring, stop stirring after mixing evenly, and let stand at room temperature overnight for reaction. The composite microspheres generated by the reaction were collected by centrifugation, washed with water, water-methanol (1:1), methanol and acetone in sequence. Drying under vacuum overnight at 60°C yielded 11.6 g of yellow microspheres. The composite microspheres are heat treated and calcined at 250-300° C., 500-550° C. and 850-900° C. for 1-2 hours respectively. After the non-magnetic silica gel particles were removed by magnetic separation, 5.7 g of free-flowing brown-red magnetic microspheres were obtained. Calculated by weight percentage of oxide content in the mixed sol, the yield of magnetic microspheres reaches 20%.

Embodiment 4: the preparation of magnetic chromatographic filler

Add 5 g of magnetic porous silica gel to 100 ml of dry toluene, and obtain a homogenate after ultrasonic dispersion. The homogenate was heated to around 100°C to reflux the toluene. Distill off about 40ml of toluene, add 6 drops of triethylamine and 4ml of octyltrichlorosilane, and heat to reflux for 18h in a nitrogen atmosphere. After cooling, the silanized magnetic microspheres were recovered by filtration, and washed successively with 50 ml of toluene, dichloromethane, ethanol and acetone. Vacuum dried at 60°C for 9h.

Weigh 3 g of silanized magnetic microspheres, disperse them in 40 ml of isopropanol to make a homogenate, and put them into a 150×4.6 mm empty stainless steel column under a high pressure of 8000 psi. Baseline separation was obtained for a standard mixture containing uracil, acetone, 4-chloronitrobenzene and naphthalene using 80% (v/v) methanol-water solution as the mobile phase.

Claims (4)

1. ferromagnetism Bio-sil microballoon, this microballoon adopts the iron particle of super paramagnetic, is that template is prepared from the Lauxite, and it is characterized in that: this microballoon is to be 100-450m with the specific area ²/ g, the aperture is at 5-15nm, and particle diameter is at 0.5-20 μ m, and silicon dioxide is the microballoon of base material, and the di-iron trioxide particulate of the nano level superparamagnetism that evenly is scattered here and there in this base material constitutes.

2. method for preparing by the described ferromagnetism Bio-sil of claim 1 microballoon, its process comprises the preparation of iron oxide colloidal sol, the preparation of iron oxide/silicon dioxide mixed sols, the preparation of organic/inorganic complex microsphere, the preparation of magnetic porous silica gel, it is characterized in that comprising following concrete steps:

1). be that 1-3.0 is with FeCl in molar ratio ₃.6H ₂O and NaHCO ₃Mixing and water adding stirs and makes it abundant dissolving;

2). get an amount of silicon dioxide gel, to 2.0-2.5, press Fe with the acid for adjusting pH that comprises red fuming nitric acid (RFNA) ₂O ₃With SiO ₂Mol ratio is that 0.01-1.0 mixes iron oxide colloidal sol with silicon dioxide gel;

3). add urea, formolite reaction monomer in iron oxide/silicon dioxide mixed sols, its mol ratio is 1-1.5, and the percentage of control inorganic constituents is 60%, is 1-4 at pH, at 5-50 ℃ of following reaction 1-24h, filters and collects complex microsphere;

4). respectively at 300-350 ℃, 600-650 ℃ and 900-950 ℃ of each heating and calcining 2-5h, iron oxide at high temperature undergoes phase transition and obtains ferromagnetism Bio-sil microballoon the complex microsphere that method for preparing obtains after drying.

3. by the preparation method of the described ferromagnetism Bio-sil of claim 2 microballoon, it is characterized in that: Fe ₂O ₃With SiO ₂Preferred molar ratio be 0.3-0.5.

4. press the purposes of claim 1 or the described ferromagnetism Bio-sil of claim 2 microballoon, it is characterized in that containing chloro octyl group silane reagent by the surface employing to microballoon carries out finishing, the ferromagnetism Bio-sil microballoon that hydrophobic chemical functional group obtains on the bonding can be used as anti-phase magnetic chromatographic stationary phase.