CN108586660A - The preparation method of TNT magnetic molecularly imprinted polymer microballoons - Google Patents

Abstract

The invention discloses a preparation method of TNT magnetic molecule imprinted polymer microspheres. The method first uses 3-aminopropyltriethoxysilane to carry out amination modification on the surface of Fe ₃ O ₄ nanoparticles, then disperses the aminated Fe ₃ O ₄ nanoparticles in acetonitrile, and adds template molecule TNT and functional Monomer acrylamide, after pre-polymerization, add cross-linking agent ethylene glycol dimethacrylate and initiator azobisisobutyronitrile to prepare magnetically imprinted polymer microspheres, and finally elute the microspheres to obtain TNT Magnetic Molecularly Imprinted Polymer Microspheres. The present invention combines molecular imprinting and magnetic separation technology, and the prepared polymer particles are uniform in shape and size, which increases the specific surface area of TNT molecular imprinting polymer microspheres, has good adsorption and separation performance, and the adsorption capacity is about the same as that of traditional embedding methods. 2.6 times that of the embedding method, and the separation time is about 1/5 of that of the embedding method, which can realize the specific adsorption of TNT.

Description

Preparation method of TNT magnetic molecularly imprinted polymer microspheres

technical field

The invention belongs to the technical field of nitro explosive detection, and relates to a preparation method of TNT magnetic molecularly imprinted polymer microspheres.

Background technique

Trinitrotoluene (TNT) is a commonly used elemental explosive, which has stable physical and chemical properties, high explosive power, and low cost, and is widely used in military industry. TNT is highly toxic and difficult to degrade. The residual TNT in production and use places poses a huge threat to personnel health and environmental safety. It is very difficult to treat TNT that enters the soil and wastewater. Currently commonly used detection methods include activated carbon adsorption and degradation methods, etc., but these methods have low adsorption efficiency and the adsorbent is difficult to regenerate.

Molecularly Imprinted Polymer (MIP) refers to a polymer material prepared by molecular imprinting technology that can selectively recognize a specific target molecule. It is simple to prepare, stable in structure, and reusable. At present, TNT molecularly imprinted polymers prepared by traditional embedding methods have disadvantages such as too deep embedding of binding sites, uneven binding sites, difficult elution of template molecules, and difficulty in recombination.

Surface imprinting technology refers to distributing the binding sites of polymers on the easily accessible carrier surface as much as possible, so as to facilitate the elution and recombination of template molecules. Surface molecular imprinting is mainly to carry out graft polymerization on the surface of silica gel, organic polymer carrier, and capillary surface, and introduce molecular imprinting technology to prepare molecularly imprinted polymers on the surface of the carrier. This technology can effectively solve the problem of polymer particle binding sites in traditional polymerization methods. Uneven point distribution, poor accessibility, slow recognition, etc., and can effectively control the size of the target molecular imprinted hole on the polymer surface, improving the selectivity of the polymer.

Contents of the invention

The purpose of the present invention is to provide a preparation method of TNT magnetic molecularly imprinted polymer microspheres.

Technical scheme of the present invention is as follows:

The preparation method of TNT magnetic molecularly imprinted polymer microspheres, the specific steps are as follows:

Step 1, ultrasonically disperse Fe ₃ O ₄ nanoparticles in an ethanol solution with a pH of 3.5 to 4, add 3-aminopropyltriethoxysilane (KH550) dropwise under stirring, and blow nitrogen to remove oxygen, 50 to 80 Stir the reaction in a water bath at ℃. After the reaction, collect the Fe ₃ O ₄ nanoparticles with a magnet, wash with water until the pH of the eluate is neutral, and dry in vacuum to obtain aminated Fe ₃ O ₄ nanoparticles;

Step 2, disperse the aminated Fe ₃ O ₄ nanoparticles in acetonitrile, add template molecule TNT and functional monomer acrylamide, ultrasonically disperse evenly, carry out pre-polymerization, add ethylene glycol dimethacrylate (EGDMA), couple Nitroisobutyronitrile (AIBN) and acetonitrile are mixed uniformly in an ice-water bath by ultrasonic, nitrogen deoxygenation, under water bath conditions, reaction at 50±5°C for 6-8 hours, polymerization at 60±5°C for 24-36 hours, aging at 85±5°C 6~8h, after the reaction is over, use a magnet to separate the product, wash with acetonitrile and methanol several times to remove unreacted reagents on the surface of the polymer, and place it in a mixture of methanol/acetic acid for elution until it cannot be detected in the eluate The template molecules were washed with methanol to remove excess acetic acid, and dried in vacuum to obtain magnetic molecularly imprinted polymers (MMIPs).

Preferably, in step 1, the mass volume ratio of the Fe ₃ O ₄ nanoparticles to KH550 is 1:1.5˜2.5.

Preferably, in step 2, the prepolymerization time is 4 to 6 hours, the molar ratio of TNT to acrylamide is 1:4 to 5, and the molar ratio of TNT to ethylene glycol dimethacrylate is 1:10 ～20, the mass volume ratio of azobisisobutyronitrile to acetonitrile is 6～11:11, and the volume ratio of methanol to acetic acid is 8:2.

Compared with the prior art, the present invention has the following advantages:

The present invention combines molecular imprinting and magnetic separation technology, KH550 modified Fe ₃ O ₄ has strong magnetism, amino groups are easy to detect, and the prepared polymer particles are uniform in shape and size, increasing the specific surface area of TNT molecular imprinting polymer microspheres, and having Good adsorption and separation performance, the adsorption capacity is about 2.6 times that of the traditional embedding method, and the separation time is about 1/5 of the embedding method, which can realize the specific adsorption of TNT.

Description of drawings

FIG. 1 is a transmission electron micrograph of the magnetic molecularly imprinted polymer prepared in Example 1.

Fig. 2 is the infrared absorption spectrum of (a) Fe ₃ O ₄ , (b) modified Fe ₃ O ₄ , (c) MMIPs, and (d) eluted MMIPs prepared in Example 1.

FIG. 3 is the thermogravimetric spectrum of the magnetic molecularly imprinted polymer prepared in Example 1. FIG.

Fig. 4 is the XRD pattern of (a) Fe ₃ O ₄ , (b) modified Fe ₃ O ₄ , (c) MMIPs prepared in Example 1.

Detailed ways

The present invention will be described in further detail below in conjunction with specific embodiments and accompanying drawings.

Example 1

1. Amino modified ferric oxide

First, prepare 150ml of ethanol: deionized water = 1:1 mixed solution, and place the solution in a 250ml three-neck round bottom flask. Use acetic acid to adjust the pH value of the appealing solution to 4, accurately weigh 0.4g of Fe ₃ O ₄ nanoparticles into the above mixed solution, and ultrasonically disperse and mix evenly. After the mixing is completed, place the flask in a water bath, stir rapidly with a stirring paddle, and add 0.5ml KH550 dropwise while stirring, deoxygenate the system with nitrogen for 10 minutes, and seal it with vacuum silicone grease. At 60°C, the reaction was stirred for 3h. After the reaction was completed, the nanoparticles were collected using a magnet, and the product was washed with deionized water several times until the pH of the eluate was neutral, and the product was vacuum-dried and collected for use.

2. Synthesis of molecularly imprinted polymers on magnetic surfaces

Weigh 100mg of aminated Fe ₃ O ₄ nanoparticles prepared above and disperse them in 30ml of acetonitrile solution, then add 0.5mmol TNT, 2mmol AM, and ultrasonically disperse and mix evenly, and pre-polymerize the mixed solution so that the template molecules and functional monomers fully interact . Subsequently, the solution was transferred to a three-necked round-bottomed flask, and 10 mmol EGDMA, 70 mg AIBN, and 80 ml of acetonitrile were added thereto, and the mixture was sonicated in an ice-water bath for 10 min, and mixed uniformly. Then, under the condition of an ice-water bath, nitrogen was passed through the mixture to remove oxygen for 15 minutes, sealed with vacuum silicone grease, mechanically stirred, and heated in a water bath. The reaction system was first reacted at 50°C for 6h, polymerized at 60°C for 24h, and aged at 85°C for 6h. After the reaction is completed, use a magnet to separate the product, and use acetonitrile and methanol to wash repeatedly to remove unreacted reagents on the polymer surface. The product was placed in a mixture of methanol/acetic acid (8:2), and the template molecule TNT in the polymer was eluted until no template molecule was detected in the eluate, and the eluted polymer was washed with methanol to remove excess acetic acid, After vacuum drying, the template-removed MMIPs can be obtained.

Figure 1 is a transmission electron microscope image of the MMIPs prepared in this example. The TNT magnetic molecularly imprinted polymer prepared in this example has regular morphology and uniform particle size.

Fig. 2 is the infrared absorption spectrum of (a) Fe ₃ O ₄ , (b) modified Fe ₃ O ₄ , (c) MMIPs, and (d) eluted MMIPs prepared in this example. Among them, the absorption peaks at ~2978cm ^-1 and ~2895cm ^-1 of curve 2b are hydrocarbon stretching vibration peaks, and the stretching vibration peak of Si _- O _- Si appears at ~1064cm ^-1 Successfully modified with KH-550. The strong absorption peak at 1730cm ^-1 in curve c is the stretching vibration peak of C=O on EGDMA, and the absorption peak at 1540cm ^-1 is the characteristic absorption peak of TNT, which is caused by the vibration of the benzene ring skeleton in the TNT molecule. It can be seen that successfully Molecularly imprinted polymers of TNT synthesized on the surface of ferric oxide. After elution with methanol/acetic acid (8:2), the characteristic absorption peak of TNT in curve d weakened significantly and almost completely disappeared, indicating that most of the template molecule TNT imprinted in MIP can be eluted, so that in the polymer A hole that matches the shape and size of TNT and has an active site is left in the TNT, so as to realize the specific adsorption of the template molecule TNT.

Fig. 3 is the thermal gravimetric spectrum of the magnetic molecularly imprinted polymer prepared in this example. The two lines in the figure are the TG curve and the pyrolysis weight loss differential curve respectively. The weight loss at 0-100 °C in the TG curve is a small amount of water adsorbed on the surface of the polymer, and the weight loss rate in this temperature range is about 0.9%, indicating that the overall dryness of the sample is better. MMIPs polymer microspheres have almost no weight loss in the range of 100-300 °C, and the polymerization has good thermal stability in this temperature range. After 300°C, the Fe ₃ O ₄ core surface coated polymer shell began to decompose, and when the temperature rose to 520°C, the polymer microspheres lost 85% of their weight within this temperature range. When the temperature is higher than 520°C, as the temperature rises, the weight of the remaining 13.4% components is stable and hardly decomposes. This part of the components is Fe ₃ O ₄ cores, indicating that the mass percentage of Fe ₃ O ₄ cores in MMIPs is about was 13.4%.

Fig. 4 is the XRD pattern of (a) Fe ₃ O ₄ , (b) modified Fe ₃ O ₄ , (c) MMIPs prepared in this example. It can be seen from the figure that in the range of 2θ from 10° to 80°, the typical diffraction peaks of Fe ₃ O ₄ appeared in all three samples, and the peak positions did not change, respectively 2θ=30.2°, 35.5°, 43.1° , 53.5°, 56.9°, 62.7°, the diffraction peaks at these positions correspond to the diffraction crystal planes (220), (311), (400), (422), (511), (440) respectively, which is consistent with the JCPDS card The standard XRD data of Fe ₃ O ₄ in . The XRD pattern shows that the Fe ₃ O ₄ particles are highly crystalline materials with a spinel structure, and the crystal form of the Fe ₃ O ₄ particles does not change during the process of amino modification and surface synthesis of polymers. The intensity of the diffraction peaks of MMIPs particles decreased significantly, and the difference in the peak width of the particles reflected the change of the average particle size. With the increase of the particle size, narrower peak widths appeared in the XRD spectrum. Therefore, the process of preparing the imprinted polymer on the surface does not change the crystal form of Fe ₃ O ₄ nanoparticles, but the size of the particles changes to a certain extent.

Polymer adsorption performance research:

Weigh 15mg of MMIPs into a 10ml centrifuge tube, add 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0mg/ml TNT in acetonitrile solution 5ml. The centrifuge tube was sealed and placed in a shaker, and shaken at room temperature for 12 h. Centrifuge the adsorbed solution in a high-speed centrifuge, dilute an appropriate amount of centrifugate, and filter with a 0.22 μm membrane. The concentration of TNT in the adsorption solution was measured at 245 nm by high performance liquid chromatography, and each sample was measured three times to obtain the average value. According to the change of TNT content in the solution before and after adsorption, the equilibrium binding amount Q of the polymer to TNT was calculated using the following formula.

Q＝(C ₀ -C)×V/m

Where Q is the equilibrium adsorption amount (mg/g) of imprinted and non-imprinted polymers to the template molecule TNT; _C0 is the initial concentration of TNT in the adsorbed solution (mg/ml); C is the concentration of TNT in the solution at adsorption equilibrium (mg/ml); V is the volume (ml) of the adsorption solution; m is the mass (mg) of the added polymer.

The results showed that with the increase of the initial concentration of TNT, the adsorption capacity of MMIPs on the substrate showed an upward trend. The greater the concentration of TNT in the solution, the greater the concentration difference between the surface of the adsorbent and the TNT in the solution, and the greater the adsorption kinetics. The greater the adsorption capacity. The maximum equilibrium adsorption capacity of 13.8mg/g was reached in the solution of 1.0mg/ml.

Comparative example 1

This comparative example is basically the same as in Example 1, and non-imprinted adsorbents, ie MNIPs, are prepared. The amounts of the reagents used refer to those used in the preparation of the MMIPs in the examples, except that the template molecule TNT is not added. The elution mode and adsorption performance research are also the same as in Example 1.

The results showed that initially, with the increase of the initial concentration of TNT, the adsorption amount of MNIPs to the substrate showed an upward trend. The greater the concentration of TNT in the solution, the greater the concentration difference between the surface of the adsorbent and the TNT in the solution, and the greater the adsorption kinetics. The greater the amount of adsorption exhibited. But when the concentration reaches 0.4mg/ml, the adsorption capacity of MNIPs tends to be saturated, and the maximum equilibrium adsorption capacity is 2.9mg/g.

Comparative example 2

This comparative example is basically the same as Example 1. To prepare TNT molecularly imprinted polymer comparative sample 1, the amount of reagents used refers to the amount used in the preparation of MMIPs in Example 1. Fe ₃ O ₄ and KH550 were added at a mass volume ratio of 1:4. The elution mode and adsorption performance research are also the same as in Example 1.

The results showed that when excessive KH550 coated on the surface of Fe ₃ O ₄ , the particle size of the magnetic particles became larger, and the inter-particle dispersion became worse, forming massive agglomerates, and it was difficult to form magnetic molecularly imprinted polymers.

Comparative example 3

This comparative example is basically the same as that of Example 1. The TNT molecularly imprinted polymer comparative sample 2 was prepared. The amount of reagents used was referred to the amount used in the preparation of MMIPs in Example 1, and the amount of acetonitrile solvent was reduced to 70ml. The elution mode and adsorption performance research are also the same as in Example 1.

The results show that the concentration of the functional monomer increases with the decrease of the solvent, and the particles of the control sample 2 stick together, unable to form a regular spherical shape. When the concentration reaches 0.7 mg/ml, the adsorption capacity of the control sample tends to be saturated, and the maximum equilibrium adsorption capacity is 9.6 mg/ml. g.

Example 2

1. Amino modified ferric oxide

First, prepare 150ml of ethanol: deionized water = 1:1 mixed solution, and place the solution in a 250ml three-neck round bottom flask. Use acetic acid to adjust the pH value of the appealing solution to 3.7, accurately weigh 0.42g of Fe ₃ O ₄ nanoparticles into the above mixed solution, and ultrasonically disperse and mix evenly. After the mixing is completed, place the flask in a water bath, stir rapidly with a stirring paddle, and add 0.8ml KH550 dropwise while stirring, deoxygenate the system with nitrogen for 10 minutes, and seal it with vacuum silicone grease. At 60°C, the reaction was stirred for 4h. After the reaction was completed, the nanoparticles were collected using a magnet, and the product was washed with deionized water several times until the pH of the eluate was neutral, and the product was vacuum-dried and collected for use.

2. Synthesis of molecularly imprinted polymers on magnetic surfaces

Weigh 100mg of aminated Fe ₃ O ₄ nanoparticles prepared above and disperse them in 40ml of acetonitrile solution, then add 0.6mmol TNT, 3mmolAM, and ultrasonically disperse and mix evenly, and let the mixture stand for 5 hours to fully interact with the template molecules and functional monomers Perform pre-polymerization. Subsequently, the solution was transferred to a three-necked round-bottomed flask, and 20 mmol EGDMA, 60 mg AIBN, and 60 ml of acetonitrile were added thereto, and the ice-water bath was sonicated for 15 min to mix well. Then, under the condition of an ice-water bath, nitrogen was passed through the mixture to remove oxygen for 20 minutes, sealed with vacuum silicone grease, mechanically stirred, and heated in a water bath. The reaction system was first reacted at 50°C for 6h, polymerized at 60°C for 24h, and aged at 85°C for 6h. After the reaction is completed, use a magnet to separate the product, and use acetonitrile and methanol to wash repeatedly to remove unreacted reagents on the polymer surface. The product was placed in a mixture of methanol/acetic acid (8:2), and the template molecule TNT in the polymer was eluted until no template molecule was detected in the eluate, and the eluted polymer was washed with methanol to remove excess acetic acid, After vacuum drying, the template-removed MMIPs can be obtained.

The equilibrium adsorption performance research is the same as in Example 1. Then carry out adsorption selectivity analysis, take 5ml of acetonitrile solution of the same concentration of TNT, RDX, 2,4-DNT, add 10mg MMIPs, shake at room temperature for 4h, magnetically separate, and use high performance liquid chromatography to measure the bottom of the adsorption solution after the adsorption is completed. substance concentration.

The results showed that MMIPs had good adsorption to TNT molecules, and the maximum equilibrium adsorption capacity was 13.5 mg/g. In the adsorption selectivity analysis experiment, the adsorption capacity of MMIPs imprinted polymers on TNT was 8.6 mg/g, which was 2.3 times that of DNT and 2.9 times that of RDX, and the adsorption capacity of imprinted polymers for TNT was far superior to other Structural analogues indicate that MMIPs have good selectivity for TNT and can achieve specific adsorption for TNT.

Claims (7)

1. The preparation method of 1.TNT magnetic molecularly imprinted polymer microballoons, which is characterized in that be as follows：

   Step 1, by Fe₃O₄Nano-particle ultrasonic disperse is in the ethanol solution that pH is 3.5~4, and under stirring, 3- aminopropyls are added dropwise Triethoxysilane leads to nitrogen deoxygenation, is stirred to react under 50~80 DEG C of water-baths, and after reaction, magnet collects Fe₃O₄Nanoparticle Son is washed to eluate pH and is in neutrality, and vacuum drying obtains amination Fe₃O₄Nano-particle；

   Step 2, by amination Fe₃O₄Nano-particle is scattered in acetonitrile, and template molecule TNT and function monomer acrylamide is added, Ultrasonic disperse is uniform, carries out prepolymerization, and ethylene glycol dimethacrylate, azodiisobutyronitrile and acetonitrile is added, and ice-water bath is super Sound is uniformly mixed, and leads to nitrogen deoxygenation, under water bath condition, reacts 6~8h at 50 ± 5 DEG C, 60 ± 5 DEG C of polymerization 24~36h, and 85 ± 5 DEG C curing 6~8h product is detached using magnet after reaction, with acetonitrile, methanol repeatedly wash removing polymer surfaces not The reagent of reaction is placed in methanol/acetic acid mixture and is eluted, until can't detect template molecule in eluate, methanol is washed Extra acetic acid is removed, is dried in vacuo to get magnetic molecularly imprinted polymer.
2. 2. preparation method according to claim 1, which is characterized in that in step 1, the Fe₃O₄Nano-particle with The mass volume ratio of KH550 is 1:1.5~2.5.
3. 3. preparation method according to claim 1, which is characterized in that in step 2, the prepolymerized time be 4~ 6h。
4. 4. preparation method according to claim 1, which is characterized in that in step 2, the TNT and acrylamide rub You are than being 1:4~5.
5. 5. preparation method according to claim 1, which is characterized in that in step 2, the TNT and ethylene glycol dimethyl The molar ratio of acrylate is 1:10~20.
6. 6. preparation method according to claim 1, which is characterized in that in step 2, the azodiisobutyronitrile and acetonitrile Mass volume ratio be 6~11:11.
7. 7. preparation method according to claim 1, which is characterized in that in step 2, the volume ratio of the methanol and acetic acid It is 8:2.