A positively charged magnetic filler and its preparation method

Abstract

The present invention discloses a positively charged magnetic filler and a preparation method thereof, belonging to the technical field of biotechnology. The technical solution is as follows: a biochar filler PSt-DMC-BA@Fe3O4@BC coated with positively charged magnetic nanoparticles, and the preparation includes the following steps: 1) preparation of nanoparticles DTAB@Fe3O4; 2) preparation of positively charged nanoparticles PDMC@Fe3O4; 3) preparation of positively charged magnetic filler PSt-BA@PDMC@Fe3O4@BC. The present invention uses distiller's grains biogas residue biochar as a raw material and adopts the nanoparticle adsorption-film coating method to coat a large number of positively charged groups, quaternary ammonium (-NC3 + ) modified magnetic nanoparticles Fe3O4 on the surface of the biogas residue biochar by film coating to obtain a positively charged magnetic biochar material with biochar as the core and -NC3 + &Fe3O4 coated on the surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of biological fillers, and particularly relates to a positively charged magnetic filler and a preparation method thereof. Background Art

[0002] Methane is the second largest greenhouse gas globally, and its warming potential is about 20-30 times that of carbon dioxide of the same mass. Its aggravating effect on climate change cannot be ignored. The methane biofilter mediated by aerobic methanotrophs is an efficient, safe, economical, and environmentally friendly method for removing low-concentration methane, with advantages such as mild operating conditions, high safety, high removal rate, low cost, and few by-products. However, in actual operation, it often faces adverse factors such as slow cell growth, difficult cultivation, low activity, and poor stability, resulting in the problems that the operating performance of the biofilter and the methane removal efficiency cannot be maintained highly efficient and stable for a long time.

[0003] To improve the growth intensity, metabolic activity, and cell stability of methanotrophs in filters, a porous filler with a relatively low cost can be used for the attachment and immobilization of bacteria. The abundant pores of the filler can provide a large number of attachment sites for methanotrophs, forming a biofilm covering the surface of the filler. Compared with free microbial cells, the immobilized biofilm has a higher cell density and stronger metabolic activity. At the same time, the pores have a sheltering effect, avoiding cell loss and damage caused by external forces, and the microorganisms have stronger stability and tolerance. Chinese invention patent CN115106071A, a novel magnetic material for sewage treatment and its application, discloses a novel magnetic material for sewage treatment. In this invention, food waste banana peel is used to functionalize magnetic nanoparticles. Since it is rich in lignin, hemicellulose, and cellulose, and its molecular formula contains a large number of hydroxyl functional groups, modifying the magnetic nanoparticles can effectively increase their adsorption of metal ions in sewage. At the same time, the magnetic particles modified with oleic acid have good sedimentation stability and can effectively avoid agglomeration. Chinese invention patent CN110745965A, a magnetic filler for sewage treatment and its preparation method, first acid-modifies biochar, then adsorbs iron ions and heavy metal ions to obtain biochar adsorbed with heavy metals, and reacts it in a strong base solution to obtain a magnetic filler for sewage treatment; the preparation process of the magnetic filler is simple and convenient to operate, and the prepared magnetic filler based on biochar for treating heavy metal wastewater has a good biofilm formation effect. Chinese invention patent CN103641233B, a method for preparing a magnetic filler using waste plastic bottles, includes cutting the plastic bottles, low-temperature plasma modification, and spraying fine ferrite powder. The specific preparation process is as follows: first, cut the waste plastic bottles into thin plastic strips, then use a dielectric barrier discharge plasma generator to generate low-temperature plasma to modify the thin plastic strips, and finally use an air stream to spray fine ferrite powder on the surface of the thin plastic strips to form a plastic magnetic filler. The raw materials of the magnetic filler are waste plastic bottles and magnetic ferrite, the product of heavy metal ion wastewater treatment, with low cost, realizing the resource utilization of solid waste; the surface of the magnetic filler has high biological affinity, is easy to form a biofilm, and has high efficiency in treating sewage. Chinese invention patent CN114181429B, a modified polyurethane sponge filler, its preparation method and use, uses a polyurethane sponge with a relatively large porosity and specific surface area as the main body. First, soak and corrode it in a potassium permanganate sulfuric acid solution to significantly increase the surface roughness of the filler; then load powdered activated carbon onto the surface of the filler to increase the specific surface area and have a certain adsorption capacity for pollutants; then soak it in a ferric chloride chitosan solution to make the surface of the filler positively charged, and the modified polyurethane sponge and bacteria with opposite charges are attracted by electrostatic interaction, promoting microbial attachment and biofilm formation; after washing and drying, a modified polyurethane sponge filler is obtained.The modified polyurethane sponge filler prepared by the present invention has strong adsorption properties for both waste gas and bacteria. While ensuring the treatment efficiency, it solves the problems of low mass transfer rate and long biofilm formation time in the existing biological treatment of waste gas, and improves the waste gas treatment effect. The raw materials and their mass fractions used in a kind of electrophilic biological carrier and its preparation method of Chinese invention patent CN103420490B are 100 - 250 parts of polymer base material, 2 - 15 parts of electrophilic functional material, and 2 - 20 parts, 2 - 20 parts, and 1 - 10 parts of auxiliary materials 1, 2, and 3 respectively. The above raw materials are formed into pellets through mixing, granulation, screw extrusion, and cooling and cutting. The biological carrier provided by the present invention is convenient to prepare, and its density is 0.91 - 0.97 g / cm³. 3 Controllable; according to the characteristic that microorganisms are negatively charged in water, a positively charged functional material is mixed in the carrier to make the surface of the carrier carry a positive charge, so as to enhance the affinity between microorganisms and the carrier. Such biological carriers are conducive to the attachment and growth of microorganisms, easy biofilm formation, and short cycle; large biomass, high ammonia nitrogen removal efficiency, and good effluent quality; good sludge sedimentation performance, and no sludge blockage phenomenon in the operation of the equipment; long service life of the biological carrier, and no need for manual replacement and maintenance. However, the current packing modification technology still has the following problems: First, the microbial attachment efficiency and growth and metabolism activity of the existing modified packing need to be further improved; second, there are few packing modification technologies suitable for improving the immobilization efficiency of methanotrophs and enhancing the removal efficiency of methane biofilters; third, most of the current magnetic modified packings are simple physical adsorption of magnetic nanoparticles by porous materials, and the interaction force between the two is weak and unstable, resulting in the difficulty of maintaining stable performance of the formed composite packing in actual use for a long time. Summary of the Invention

[0004] The present invention provides a positively charged magnetic packing and its preparation method. Using distiller's grains biogas residue biochar as the raw material, by the method of nanoparticle adsorption - film - forming coating, a large number of positively charged groups - NC 3 + modified magnetic nanoparticles Fe 3 O 4 are film - formed and coated on the surface of biogas residue biochar to obtain a positively charged magnetic biochar material with biochar as the core and - NC 3 + and Fe 3 O 4 coated on the surface.

[0005] The technical solution of the present invention is as follows:

[0006] In the first aspect, a preparation method of a positively charged magnetic packing is disclosed, including the following steps:

[0007] 1) Nanoparticles DTAB@Fe 3 O 4Preparation: Under a nitrogen atmosphere and constant-speed stirring, add distilled water, ferrous chloride, and ferric chloride to the reactor in sequence. Stir until the ferrous chloride and ferric chloride are dissolved, then raise the temperature to 80 - 90 °C, and add ammonia water to adjust the pH to 9 - 12. When the solution color turns black, add dodecyl trimethyl ammonium bromide, and react at a constant temperature of 80 - 90 °C for 0.5 - 1 h to prepare a stably dispersed DTAB@Fe 3 O 4 nanoparticle dispersion liquid, and wash to obtain DTAB@Fe 3 O 4 nanoparticles;

[0008] 2) Preparation of positively charged nanoparticles PDMC@Fe 3 O 4 : Disperse the DTAB@Fe 3 O 4 nanoparticles prepared in step 1) in distilled water. Under constant-speed stirring, add styrene, methacryloyloxyethyl trimethyl ammonium chloride, and butyl acrylate in sequence, stir until dissolved, raise the temperature to 70 - 90 °C, and dropwise add an initiator to initiate the polymerization reaction. Continue the reaction for 2 - 4 h to obtain positively charged PDMC@Fe 3 O 4 nanoparticles. Collect the prepared PDMC@Fe 3 O 4 with a strong magnet, wash, and dry;

[0009] 3) Preparation of positively charged magnetic filler PSt - BA@PDMC@Fe 3 O 4 @BC: Disperse the PDMC@Fe 3 O 4 prepared in step 2) in distilled water, add biogas residue biochar to it, and adsorb fully under constant-speed stirring for 1 - 2 h. Then add styrene and butyl acrylate in sequence, stir until dissolved, raise the temperature to 80 - 90 °C, and dropwise add an initiator to initiate the copolymerization reaction of styrene and butyl acrylate. Continue the reaction for 2 - 4 h, stop the reaction, filter, take the solid filter residue, dry it at 100 - 105 °C for 24 - 48 h, take it out, and cool it at room temperature. Finally, obtain the biochar filler PSt - BA@PDMC@Fe 3 O 4 @BC coated with positively charged magnetic nanoparticles.

[0010] Preferably, the stirring speed in both step 1) and step 2) is 300 - 400 rpm.

[0011] Preferably, the total mass of ferrous chloride, ferric chloride and dodecyl trimethyl ammonium bromide added in step 1) is 15%-20% of the mass of distilled water, the mass ratio of ferrous chloride to ferric chloride is 1:2-3, and the addition amount of dodecyl trimethyl ammonium bromide is 20%-30% of the total mass of ferrous chloride and ferric chloride.

[0012] Preferably, the addition amount of methacryloyloxyethyl trimethyl ammonium chloride in step 2) is 20-40% of the dry weight of the prepared DTAB@Fe 3 O 4 nanoparticles.

[0013] Preferably, the initiator in step 2) is potassium persulfate or ammonium persulfate, and the addition amount of the initiator is 5%-15% of the mass of methacryloyloxyethyl trimethyl ammonium chloride.

[0014] Preferably, the addition amounts of styrene and butyl acrylate in step 3) need to be calculated by a formula to make the glass transition temperature of their copolymer between 70-80 °C. The formula calculation is as follows: In the formula, T g is the glass transition temperature (K) of the copolymer, (T g ) A , (T g ) B are the glass transition temperatures (K) of the homopolymers styrene and butyl acrylate respectively, and W A , W B are the weight fractions of the homopolymers styrene and butyl acrylate in the copolymer respectively.

[0015] Preferably, the initiator in step 3) is potassium persulfate or ammonium persulfate, and the addition amount of the initiator is 5%-15% of the total mass of styrene and butyl acrylate.

[0016] Second, a positively charged magnetic nanoparticle-coated biochar filler PSt-BA@PDMC@Fe 3 O 4 @BC prepared by the preparation method described above is disclosed.

[0017] Preparation principle: First, the surfactant dodecyl trimethyl ammonium bromide (DTAB) is added to the coprecipitation reaction of Fe 3 O 4 magnetic nanoparticles to prepare well-dispersed magnetic nanoparticles DTAB@Fe 3 O 4 ; then, DTAB@Fe 3 O 4 is dispersed into the soap-free emulsion polymerization process of methacryloyloxyethyl trimethyl ammonium chloride (DMC), so that the macromolecular chain PDMC formed by polymerization wraps around DTAB@Fe 3O 4 On the surface of the magnetic nanoparticles, a positively charged group - NC is formed 3 + The magnetic nanoparticles PDMC@Fe enclosed 3 O 4 ; Next, add the negatively charged porous material biochar particles to PDMC@Fe 3 O 4 dispersion, mix well and stir for a period of time. Due to the effect of electrostatic adsorption, the positively charged PDMC@Fe 3 O 4 particles are adsorbed onto the surface of the negatively charged biochar. After sufficient adsorption, styrene (St) and butyl acrylate (BA) are added successively. During the copolymerization reaction of St and BA, the copolymer PSt - BA is coated on the surface of the biochar. Take out the adsorbed biochar particles, place them in an oven at 105°C to make the copolymer PSt - BA fully melt into a highly elastic state and adhere to the surface of the biochar, and then let it cool to room temperature to make the copolymer film transform into a hard glassy state, so that the nanoparticles are firmly wrapped on the surface of the biochar, and finally obtain the biochar filler coated with positively charged magnetic nanoparticles

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention can effectively change the negative charge on the surface of biochar to positive charge, which is beneficial to the attachment of negatively charged methane - oxidizing bacteria cells, and is beneficial to the biofilm formation on the surface of the porous filler and the growth of the microbial biomass; at the same time, the biochar surface has paramagnetism, which is beneficial to improving the intracellular metabolic intensity of methane - oxidizing bacteria, increasing the absorption and conversion efficiency of methane molecules by the bacteria, and significantly improving the methane removal efficiency of the biofilter. In addition, compared with traditional acid - base modification, the reaction conditions are mild and will not damage the pore structure of the biochar itself. At the same time, due to the strong and firm film - forming effect of butyl acrylate, the magnetic nanoparticles are not easy to fall off, with stable performance and long service life Brief Description of the Drawings

[0020] Figure 1 is the preparation flow chart of the positively charged magnetic nanoparticles PSt - BA@PDMC@Fe 3 O 4 @BC in Example 1 of the present invention

[0021] Figure 2 is the schematic diagram of the preparation principle of the positively charged magnetic nanoparticles PSt - BA@PDMC@Fe 3 O 4 @BC in Example 1 of the present invention

[0022] Figure 3It is the scanning electron microscope comparison diagram of the biogas residue biochar (A) in Example 1 of the present invention and the positively charged nanoparticle-coated biochar filler PSt-BA@PDMC@Fe prepared in Example 1 3 O 4 @BC (B). Detailed implementation mode

[0023] Example 1

[0024] (1) Preparation of nanoparticles DTAB@Fe 3 O 4 : 4.05 g of FeCl 2 and 10.92 g of FeCl 3 were successively added to 100 mL of distilled water, dissolved under stirring at 300 rpm, the temperature was raised to 90 °C under nitrogen protection, and 20 mL of ammonia water was added to adjust the pH to 10. When the solution color turned black, 3 mL of dodecyltrimethylammonium bromide (DTAB) solution was added. After half an hour, a stably dispersed DTAB@Fe 3 O 4 nanoparticle dispersion was obtained. The prepared DTAB@Fe 3 O 4 magnetic nanoparticles were collected under a magnetic field and washed;

[0025] (2) Preparation of positively charged nanoparticles PDMC@Fe 3 O 4 : The DTAB@Fe 3 O 4 prepared in the above step was dispersed in 100 mL of distilled water. Under 300 rpm, 4 g of methacryloyloxyethyltrimethylammonium chloride (DMC) was added and stirred until dissolved. After the temperature was raised to 75 °C, 5 mL of potassium persulfate solution (50 g·L -1 ) was added dropwise to initiate the reaction. After 2 h of polymerization reaction, positively charged PDMC@Fe coated with a macromolecular chain PDMC 3 O 4 nanoparticles were obtained. The prepared PDMC@Fe 3 O 4 nanoparticles were collected with a strong magnet and washed and dried;

[0026] (3) Preparation of positively charged magnetic filler PSt-BA@PDMC@Fe 3 O 4 @BC: The PDMC@Fe 3 O 4 prepared in the above step was dispersed in 100 mL of water, 10 g of biogas residue biochar was added, and adsorption was carried out under stirring at 300 rpm. Since the surface of the biochar is negatively charged, under the action of electrostatic attraction, the positively charged PDMC@Fe3 O 4 The nanoparticles are fully adsorbed on the surface of the biochar and stirred thoroughly for 2 h. Then, 5.2 g of styrene (St) and 3 g of butyl acrylate (BA) are successively added to the flask. The glass transition temperature of the PSt-BA copolymer is set at 70 °C, and the addition amounts of styrene (St) and butyl acrylate (BA) are calculated. The temperature is raised to 80 °C, and 5 mL of potassium persulfate solution (150 g·L -1 ) is added dropwise to initiate the copolymerization reaction of styrene and butyl acrylate. After 4 h, the reaction stops. The mixture is filtered, and the solid residue is taken. At a temperature higher than the glass transition temperature (70 °C) of the PSt-BA copolymer, it is dried at 105 °C for 24 h. While drying the moisture, the PSt-BA copolymer is fully transformed into a highly elastic state, tightly wrapping and adhering to the surface of the filler, forming a flexible highly elastic coating film. It is taken out and cooled at room temperature, so that the coating film of the PSt-BA copolymer is transformed back into a hard vitrified state, firmly fixing the positively charged magnetic particles PDMC@Fe 3 O 4 on the surface of the filler. Finally, the biochar filler PSt-BA@PDMC@Fe 3 O 4 @BC coated with positively charged magnetic nanoparticles is obtained.

[0027] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and all such modifications or substitutions should fall within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A preparation method of a positively charged magnetic filler, characterized in that, it comprises the following steps: 1) Preparation of nanoparticles DTAB@Fe 3 O 4 : Under a nitrogen atmosphere and constant-speed stirring, successively add distilled water, ferrous chloride, and ferric chloride to the reactor, stir until the ferrous chloride and ferric chloride dissolve, heat up to 80 - 90 °C, then add ammonia water to adjust the pH to 9 - 12. When the solution color turns black, add dodecyl trimethyl ammonium bromide, and react at a constant temperature of 80 - 90 °C for 0.5 - 1 h to prepare a stably dispersed DTAB@Fe 3 O 4 nanoparticle dispersion, and wash to obtain DTAB@Fe 3 O 4 nanoparticles; 2) Preparation of positively charged nanoparticles PDMC@Fe 3 O 4 : Disperse the DTAB@Fe 3 O 4 nanoparticles prepared in step 1) in distilled water. Under constant stirring, add methacryloyloxyethyl trimethyl ammonium chloride and stir until dissolved. Heat up to 70 - 90 °C and dropwise add an initiator to initiate the polymerization reaction. Continue the reaction for 2 - 4 h to obtain positively charged PDMC@Fe 3 O 4 nanoparticles. Collect the obtained PDMC@Fe 3 O 4 using a strong magnet, wash and dry. 3) Positively charged magnetic filler PSt-BA@PDMC@Fe 3 O 4 @BC preparation: Disperse the PDMC@Fe 3 O 4 prepared in step 2) in distilled water, add biogas residue biochar to it, fully adsorb for 1-2 h under constant speed stirring, then successively add styrene and butyl acrylate, stir until dissolved, heat up to 80-90 °C, dropwise add initiator to initiate the copolymerization reaction of styrene and butyl acrylate, continue the reaction for 2-4 h, stop the reaction, filter, take the solid filter residue, dry it at 100-105 °C for 24-48 h, take it out, cool it at room temperature, and finally obtain the biochar filler PSt-BA@PDMC@Fe 3 O 4 @BC coated with positively charged magnetic nanoparticles.

2. The preparation method of the positively charged magnetic filler according to claim 1, characterized in that, the stirring speed in step 1), step 2) and step 3) is 300 - 400 rpm.

3. The preparation method of the positively charged magnetic filler according to claim 1, characterized in that, in step 1), the total added mass of ferrous chloride, ferric chloride and dodecyl trimethyl ammonium bromide is 15% - 20% of the mass of distilled water, the mass ratio of ferrous chloride to ferric chloride is 1:2 - 3, and the added amount of dodecyl trimethyl ammonium bromide is 20% - 30% of the total mass of ferrous chloride and ferric chloride.

4. The preparation method of the positively charged magnetic filler according to claim 1, characterized in that, The addition amount of methacryloyloxyethyl trimethyl ammonium chloride in step 2) is 20-40% of the dry weight of the prepared DTAB@Fe 3 O 4 nanoparticles.

5. The preparation method of the positively charged magnetic filler according to claim 1, characterized in that, in step 2), the initiator is potassium persulfate or ammonium persulfate, and the added amount of the initiator is 5% - 15% of the mass of methacryloyloxyethyl trimethyl ammonium chloride.

6. The preparation method of the positively charged magnetic filler according to claim 1, characterized in that, In step 3), the addition amounts of styrene and butyl acrylate need to be calculated by a formula to make the glass transition temperature of their copolymer between 70 - 80 °C. The formula calculation is as follows: Wherein, T g is the glass transition temperature (K) of the copolymer, (T g ) A , (T g ) B are the glass transition temperatures (K) of the homopolymers polystyrene and butyl acrylate respectively, and W A , W B are the weight fractions of the homopolymers polystyrene and butyl acrylate in the copolymer respectively.

7. The preparation method of the positively charged magnetic filler according to claim 1, characterized in that, in step 3), the initiator is potassium persulfate or ammonium persulfate, and the added amount of the initiator is 5% - 15% of the total mass of styrene and butyl acrylate.

8. The positively charged magnetic nanoparticle-coated biochar filler PSt-BA@PDMC@Fe prepared by the preparation method according to any one of claims 1-7 3 O 4 @BC.

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