Disclosure of Invention
The invention aims to provide a composite polyvinyl alcohol gel ball with a slow-release carbon source function and a preparation method thereof, so as to solve the technical problems in the prior art.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
The composite polyvinyl alcohol gel ball with the slow-release carbon source function is prepared from 10-20% of polyvinyl alcohol solution, 0.5-1% of initiator, 0.05-0.5% of cross-linking agent, 1% of boric acid solution and 0.1-1% of Fe3O4 nano powder, 1% of corn powder and 0.1-1% of polyvinyl alcohol solution mass fraction equivalent.
Further, the functional monomer comprises a monomer containing carboxyl or amino or other monomers capable of undergoing free radical polymerization.
Further, the functional monomer comprises one of 4-carboxybenzaldehyde, acrylamide and 3, 4-ethylenedioxythiophene.
Further, the functional monomer is acrylamide.
Further, the initiator is one of potassium persulfate, azobisisobutyronitrile and dimethyl azobisisobutyrate.
Further, the initiator is potassium persulfate.
Further, the cross-linking agent is N, N' -methylene acrylamide.
A preparation method of a composite polyvinyl alcohol gel ball with a slow-release carbon source function comprises the following steps:
S1, preparing a polyvinyl alcohol aqueous solution, namely weighing polyvinyl alcohol with molecular weight of 10000-20000 and hydrolysis degree of 80-98%, adding the polyvinyl alcohol into deionized water, heating to 95 ℃ under the stirring condition of 150-250rpm, and stirring for 12 hours to obtain the polyvinyl alcohol aqueous solution with mass fraction of 10%;
S2, preparing a pre-polymerization solution, namely adding functional monomers into a polyvinyl alcohol aqueous solution according to the amount, stirring until the functional monomers are uniformly mixed, sequentially adding an initiator and a cross-linking agent, and continuously stirring the mixture uniformly to obtain the pre-polymerization solution;
s3, preparing a composite hydrogel ball, namely pouring the pre-polymerized solution into a spherical mold, transferring the spherical mold into a reaction tank, and performing irradiation polymerization for 3 hours under ultraviolet rays with the wavelength of 365nm and the intensity of 250W to obtain the hydrogel ball;
S4, drying and re-swelling, namely completely drying the hydrogel spheres at 50 ℃, and soaking the hydrogel spheres in water for 2 hours after the drying is finished so as to re-swell the hydrogel spheres to obtain the acrylamide-polyvinyl alcohol double-network high-strength gel spheres;
S5, loading, namely adding the obtained acrylamide-polyvinyl alcohol dual-network high-strength gel ball into an iodine-containing volumetric flask filled with deionized water, stirring and slowly adding boric acid solution under the protection of inert gas atmosphere, and preparing the composite polyvinyl alcohol high-strength gel ball with the function of slowly releasing carbon sources by adopting an in-situ immersed precipitation phase inversion method.
The method for preparing the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function by the in-situ immersed precipitation phase conversion method comprises the steps of taking Fe3O4 nanometer powder and corn powder, performing ultrasonic dispersion in deionized water to obtain mixed powder suspension, slowly adding the mixed powder suspension into an iodometric bottle filled with the acrylamide-polyvinyl alcohol double-network high-strength gel ball, heating in a water bath under the protection of inert atmosphere for stirring reaction after the dripping is finished, and taking out and naturally drying after the reaction is finished to obtain the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function.
Further, the heating temperature in the water bath is 60-80 ℃ and the reaction time is 6-24h.
The function and principle of each raw material of the invention are as follows:
Polyvinyl alcohol solution, the main framework, provides a high strength and super hydrophilic surface.
The functional monomer is copolymerized to generate a chemical crosslinking network, and the chemical crosslinking network and the polyvinyl alcohol physical network form a double-network structure, so that the strength of the gel ball is further improved, and meanwhile, the integral structure is stabilized through covalent bonds.
Initiating free radical polymerization to promote the chemical cross-linking of the functional monomer and polyvinyl alcohol.
And the cross-linking agent is used for connecting polymer chains to form a three-dimensional chemical cross-linked network, so that the stability and durability of the gel are ensured.
Boric acid solution is dynamically and reversibly crosslinked with hydroxyl groups of polyvinyl alcohol to form boric acid ester bonds, and the initial gel strength is enhanced in an auxiliary way.
The Fe3O4 nano powder endows the gel ball with magnetism, is convenient to quickly recover and recycle through an external magnetic field, simultaneously releases iron ions to promote the metabolic activity of denitrifying bacteria, accelerates the sewage denitrification process, can also regulate the surface charge, and enhances the adhesion capability of microorganisms on the surface of the filter ball.
Corn flour is used as a solid carbon source, and simultaneously provides a growth substrate for microorganisms, so that the film forming starting time is shortened.
In the preparation method of the invention, the principle of each step is as follows:
S1, combining hydroxyl groups of polyvinyl alcohol molecular chains with water through hydrogen bonds to form a homogeneous solution, providing a matrix for subsequent reaction, and simultaneously exposing active sites so as to facilitate subsequent polymerization and crosslinking.
S2, under the action of an initiator, the functional monomer and the hydroxyl groups of the polyvinyl alcohol chain form a chemical crosslinking network through a crosslinking agent, so that the functional monomer has the flexibility of the polyvinyl alcohol and the strength of the functional monomer, the mechanical strength is enhanced, and meanwhile, the initiator excites the activity of the functional monomer, so that conditions are provided for subsequent ultraviolet polymerization.
And S3, an ultraviolet ray activated initiator is decomposed to generate active free radicals, and the chain growth and crosslinking of the functional monomer and PVA are triggered to form a primary gel network.
S4, drying to dehydrate polyvinyl alcohol molecular chains, condensing hydroxyl groups to form microcrystals, wherein a physical cross-linked network formed by the microcrystals coexists with a chemical cross-linked network to form a double-network structure, so that the mechanical strength is greatly improved, swelling is carried out after drying, open pores are reconstructed in gel, the specific surface area is improved, microorganism film formation is facilitated to be intercepted, and meanwhile, the pore structure provides space for subsequent loading of Fe3O4 nanometer powder and corn powder.
S5, loading mixed powder suspension composed of Fe3O4 nano powder and corn powder into gel, embedding the Fe3O4 nano powder into gel holes through Van der Waals force and hydrogen bond, endowing a biomembrane adhesion guiding function, promoting enrichment of denitrifying bacteria, physically embedding organic particles of corn powder, slowly releasing the corn powder in holes to form a slow-release carbon source, avoiding oxidation of Fe3O4 under inert conditions, and maintaining stable magnetic performance. Meanwhile, the residual hydroxyl and the hydrophilic property of the surface of Fe3O4 synergistically improve the hydrophilicity of the gel.
Compared with the prior art, the invention has the beneficial effects that:
1. The invention adopts a mode of copolymerizing functional group monomers to construct a chemical crosslinking network, and then induces the formation of polyvinyl alcohol microcrystals by a drying-re-swelling method to construct a physical crosslinking network, and the physical polyvinyl alcohol crystallization network and the covalent chemical crosslinking network form the physical-chemical double-network polyvinyl alcohol hydrogel ball of the high-strength high-elasticity double-network gel ball, so that the stability of long-term operation is ensured, the service life is prolonged, and simultaneously, the specific surface area of the filter ball can be increased by micro gaps in the crosslinking network, thereby being beneficial to intercepting microorganism hanging films and facilitating subsequent loading.
2. According to the invention, nano ferroferric oxide and corn meal are loaded in gel sphere pores by an in-situ immersion precipitation phase inversion method, and Fe3O4 nano powder endows surface charge, so that magnetism is obtained, the microbial propagation and growth are stimulated, and the immobilized slow-release carbon source function is realized. The gel ball has high hydrophilicity and biocompatibility, has the function of slowly releasing carbon source when being used as a water treatment material, does not actively fall off, does not produce secondary pollution, does not need to additionally add liquid carbon source in actual sewage treatment, reduces the treatment cost and improves the treatment efficiency.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below by referring to the accompanying drawings and by illustrating preferred embodiments. It should be noted, however, that many of the details set forth in the description are merely provided to provide a thorough understanding of one or more aspects of the invention, and that these aspects of the invention may be practiced without these specific details.
The composite polyvinyl alcohol gel ball with the slow-release carbon source function is characterized by comprising 10% -20% of polyvinyl alcohol solution, 0.5% -1% of initiator, 0.05% -0.5% of cross-linking agent, 0.2% -1% of polyvinyl alcohol solution mass equivalent, fe3O4 nano powder, 1% of polyvinyl alcohol solution mass equivalent, 1% of corn powder and 0.1% -1% of polyvinyl alcohol solution mass equivalent.
The functional monomer comprises carboxyl or amino or other monomers capable of undergoing free radical polymerization.
The functional monomer comprises one of 4-carboxybenzaldehyde, acrylamide and 3, 4-ethylenedioxythiophene.
The functional monomer is acrylamide.
The initiator is one of potassium persulfate, azodiisobutyronitrile and dimethyl azodiisobutyrate.
The initiator is potassium persulfate.
The cross-linking agent is N, N' -methylene acrylamide.
A composite polyvinyl alcohol gel ball with a slow-release carbon source function comprises the following steps:
S1, preparing a polyvinyl alcohol aqueous solution, namely weighing polyvinyl alcohol with molecular weight of 10000-20000 and hydrolysis degree of 80-98%, adding the polyvinyl alcohol into deionized water, heating to 95 ℃ under the stirring condition of 150-250rpm, and stirring for 12 hours to obtain the polyvinyl alcohol aqueous solution with mass fraction of 10%;
S2, preparing a pre-polymerization solution, namely adding functional monomers into a polyvinyl alcohol aqueous solution according to the amount, stirring until the functional monomers are uniformly mixed, sequentially adding an initiator and a cross-linking agent, and continuously stirring the mixture uniformly to obtain the pre-polymerization solution;
s3, preparing a composite hydrogel ball, namely pouring the pre-polymerized solution into a spherical mold, transferring the spherical mold into a reaction tank, and performing irradiation polymerization for 3 hours under ultraviolet rays with the wavelength of 365nm and the intensity of 250W to obtain the hydrogel ball;
S4, drying and re-swelling, namely completely drying the hydrogel spheres at 50 ℃, and soaking the hydrogel spheres in water for 2 hours after the drying is finished so as to re-swell the hydrogel spheres to obtain the acrylamide-polyvinyl alcohol double-network high-strength gel spheres;
S5, loading, namely adding the obtained acrylamide-polyvinyl alcohol dual-network high-strength gel ball into an iodine-containing volumetric flask filled with deionized water, stirring and slowly adding boric acid under the protection of inert gas atmosphere, and preparing the composite polyvinyl alcohol high-strength gel ball with the function of slowly releasing carbon sources by adopting an in-situ immersed precipitation phase inversion method.
The method for preparing the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function by the in-situ immersed precipitation phase conversion method comprises the steps of taking Fe3O4 nanometer powder and corn powder, performing ultrasonic dispersion in deionized water to obtain mixed powder suspension, slowly adding the mixed powder suspension into an iodometric bottle filled with the acrylamide-polyvinyl alcohol double-network high-strength gel ball, heating and stirring in a water bath at 60-80 ℃ for reaction for 6-24 hours under the protection of inert atmosphere after the dripping is finished, taking out and naturally drying after stirring is finished, and obtaining the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function.
The following is a more detailed example.
Example 1
A composite polyvinyl alcohol gel ball with a slow-release carbon source function is characterized by comprising the following raw materials of a polyvinyl alcohol solution and an acrylamide functional monomer, wherein the dosage of the functional monomer is 20% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the potassium persulfate initiator is 0.5% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the N, N' -methylene acrylamide cross-linking agent is 0.05% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the boric acid solution is 0.2% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the nano powder is Fe3O4, the dosage of the nano powder is 1% of the mass fraction equivalent of the polyvinyl alcohol solution, and the dosage of the nano powder is 1% of the mass fraction equivalent of the polyvinyl alcohol solution.
A composite polyvinyl alcohol gel ball with a slow-release carbon source function comprises the following steps:
S1, preparing a polyvinyl alcohol aqueous solution, namely weighing polyvinyl alcohol, adding the polyvinyl alcohol into deionized water, heating to 95 ℃ under the stirring condition of 250rpm, and stirring for 12 hours to obtain a 10% polyvinyl alcohol aqueous solution;
s2, preparing a pre-polymerization solution, namely taking 100g of polyvinyl alcohol aqueous solution, adding functional monomers according to the dosage, stirring until the functional monomers are uniformly mixed, sequentially adding an initiator and a cross-linking agent, and continuously stirring the mixture uniformly to obtain the pre-polymerization solution;
S3, preparing a composite hydrogel ball, namely pouring the pre-polymerized solution into a spherical mold, transferring the spherical mold into a reaction tank, and performing irradiation polymerization for 3 hours under ultraviolet rays to obtain the hydrogel ball;
S4, drying and re-swelling, namely completely drying the hydrogel spheres at 50 ℃, and soaking the hydrogel spheres in water for 2 hours after the drying is finished so as to re-swell the hydrogel spheres to obtain the acrylamide-polyvinyl alcohol double-network high-strength gel spheres;
S5, loading, namely adding the obtained acrylamide-polyvinyl alcohol dual-network high-strength gel ball into an iodine-containing volumetric flask filled with deionized water, stirring and slowly adding boric acid solution under the protection of inert gas atmosphere, and preparing the composite polyvinyl alcohol high-strength gel ball with the function of slowly releasing carbon sources by adopting an in-situ immersed precipitation phase inversion method.
The method for preparing the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function by the in-situ immersed precipitation phase conversion method comprises the steps of taking Fe3O4 nanometer powder and corn powder, performing ultrasonic dispersion in deionized water to obtain mixed powder suspension, slowly adding the mixed powder suspension into an iodometric bottle filled with the acrylamide-polyvinyl alcohol double-network high-strength gel ball, heating and stirring in a water bath at 60 ℃ under the protection of inert atmosphere for 16 hours after the dripping is finished, taking out and naturally drying after stirring is finished, and obtaining the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function.
Example 2
A composite polyvinyl alcohol gel ball with a slow-release carbon source function is characterized by comprising the following raw materials of a polyvinyl alcohol solution and a 3, 4-ethylenedioxythiophene functional monomer, wherein the dosage of the functional monomer is 15% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the azodiisobutyronitrile initiator is 1% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the N, N' -methylene acrylamide cross-linking agent is 0.1% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the boric acid solution is 0.5% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the nano powder is Fe3O4%, the dosage of the nano powder is 1% of the mass fraction equivalent of the polyvinyl alcohol solution, and the dosage of the nano powder is 0.5% of the mass fraction equivalent of the polyvinyl alcohol solution.
A composite polyvinyl alcohol gel ball with a slow-release carbon source function comprises the following steps:
s1, preparing a polyvinyl alcohol aqueous solution, namely weighing polyvinyl alcohol, adding the polyvinyl alcohol into deionized water, heating to 80 ℃ under the stirring condition of 150rpm, and stirring for 24 hours to obtain the 10% polyvinyl alcohol aqueous solution;
s2, preparing a pre-polymerization solution, namely taking 100g of polyvinyl alcohol aqueous solution, adding functional monomers according to the dosage, stirring until the functional monomers are uniformly mixed, sequentially adding an initiator and a cross-linking agent, and continuously stirring the mixture uniformly to obtain the pre-polymerization solution;
S3, preparing a composite hydrogel ball, namely pouring the pre-polymerized solution into a spherical mold, transferring the spherical mold into a reaction tank, and performing irradiation polymerization for 5 hours under ultraviolet rays to obtain the hydrogel ball;
S4, drying and re-swelling, namely completely drying the hydrogel spheres at 40 ℃, and soaking the hydrogel spheres in water for 3 hours after the drying is finished so as to re-swell the hydrogel spheres to obtain the acrylamide-polyvinyl alcohol double-network high-strength gel spheres;
S5, loading, namely adding the obtained acrylamide-polyvinyl alcohol dual-network high-strength gel ball into an iodine-containing volumetric flask filled with deionized water, stirring and slowly adding boric acid solution under the protection of inert gas atmosphere, and preparing the composite polyvinyl alcohol high-strength gel ball with the function of slowly releasing carbon sources by adopting an in-situ immersed precipitation phase inversion method.
The method for preparing the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function by the in-situ immersed precipitation phase conversion method comprises the steps of taking Fe3O4 nanometer powder and corn powder, performing ultrasonic dispersion in deionized water to obtain mixed powder suspension, slowly adding the mixed powder suspension into an iodometric bottle filled with the acrylamide-polyvinyl alcohol double-network high-strength gel ball, heating and stirring in a water bath at 70 ℃ under the protection of inert atmosphere for 24 hours after the dripping is finished, taking out and naturally drying after stirring is finished, and obtaining the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function.
Example 3
A composite polyvinyl alcohol gel ball with a slow-release carbon source function is characterized by comprising the following raw materials of a polyvinyl alcohol solution and a 4-carboxybenzaldehyde functional monomer, wherein the dosage of the functional monomer is 10% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the initiator is 0.8% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the cross-linking agent is 0.08% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the cross-linking agent is 1% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the nano powder is Fe3O4, the dosage of the nano powder is 1% of the mass fraction equivalent of the polyvinyl alcohol solution, the dosage of the nano powder is 0.1% of the mass fraction equivalent of the polyvinyl alcohol solution.
A composite polyvinyl alcohol gel ball with a slow-release carbon source function comprises the following steps:
S1, preparing a polyvinyl alcohol aqueous solution, namely weighing polyvinyl alcohol, adding the polyvinyl alcohol into deionized water, heating to 100 ℃ under the stirring condition of 200rpm, and stirring for 18 hours to obtain the 10% polyvinyl alcohol aqueous solution;
s2, preparing a pre-polymerization solution, namely taking 100g of polyvinyl alcohol aqueous solution, adding functional monomers according to the dosage, stirring until the functional monomers are uniformly mixed, sequentially adding an initiator and a cross-linking agent, and continuously stirring the mixture uniformly to obtain the pre-polymerization solution;
S3, preparing a composite hydrogel ball, namely pouring the pre-polymerized solution into a spherical mold, transferring the spherical mold into a reaction tank, and performing irradiation polymerization for 1h under ultraviolet rays to obtain the hydrogel ball;
S4, drying and re-swelling, namely completely drying the hydrogel spheres at 60 ℃, and soaking the hydrogel spheres in water for 4 hours after the drying is finished so as to re-swell the hydrogel spheres to obtain the acrylamide-polyvinyl alcohol double-network high-strength gel spheres;
S5, loading, namely adding the obtained acrylamide-polyvinyl alcohol dual-network high-strength gel ball into an iodine-containing volumetric flask filled with deionized water, stirring and slowly adding boric acid solution under the protection of inert gas atmosphere, and preparing the composite polyvinyl alcohol high-strength gel ball with the function of slowly releasing carbon sources by adopting an in-situ immersed precipitation phase inversion method.
The method for preparing the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function by the in-situ immersed precipitation phase conversion method comprises the steps of taking Fe3O4 nanometer powder and corn powder, performing ultrasonic dispersion in deionized water to obtain mixed powder suspension, slowly adding the mixed powder suspension into an iodometric bottle filled with the acrylamide-polyvinyl alcohol double-network high-strength gel ball, heating and stirring in a water bath at 80 ℃ under the protection of inert atmosphere for reaction for 6 hours after the dripping is finished, taking out and naturally drying after stirring is finished, and obtaining the composite polyvinyl alcohol high-strength gel ball with the slow-release carbon source function.
Comparative example 1
The procedure was substantially as in example 1, except that in step S5, 1g of corn flour was not added, but only 2g of Fe3O4 nano powder was added, to obtain a magnetic composite type polyvinyl alcohol high-strength gel pellet.
Comparative example 2
Substantially the same as in example 1, except that in the preparation method, step S4 was not performed, an acrylamide-polyvinyl alcohol dual-network high-strength gel sphere was obtained.
1. Water treatment experiment
The gel beads obtained in example 1 and comparative example 1 were applied to a biological aerated filter to test their treatment effect on contaminants.
The test method is as follows:
s1, paving the obtained polyvinyl alcohol gel balls in a biological filter;
S2, placing the polyvinyl alcohol gel balls into a 10L glass container for static film forming experiments, mixing inoculated activated sludge and sewage, pumping the mixture into a reactor by a pump, standing the mixture for 6 to 8 hours, enabling the sludge to be in contact with a carrier to play a role of inoculating microorganisms, discharging all the mixture, continuously feeding sewage without the sludge, and gradually increasing water inflow until film forming is completed.
The inoculated sludge is obtained from aerobic aeration Chi Huiliu sludge of a sewage treatment plant, the sludge is emptied after the inoculated sludge is soaked in a filter material for 8 hours, then the prepared sewage is introduced and replaced every 12 hours, the water temperature is about 20 ℃, the dissolved oxygen is controlled to be 2-4mg/L, and the carbon-nitrogen ratio is controlled to be 1:3;
And S3, after the film formation start is finished, when a biological film appears on the surface of the filter material, in order to compare and analyze the pollutant removal efficiency of the aeration biological filter using the modified filter material, the test tests the total nitrogen and pollutant removal effect of different filter materials under the same water inlet condition of the filter, as shown in figures 1-2.
As can be seen in figure 1 of the drawings,
In example 1, the initial TN concentration was about 15mg/L, rapidly decreased within 0 to 15 days, approached 0mg/L after 15 days, and remained stable thereafter. The removal effect of example 1 on total nitrogen was shown to be extremely remarkable, not only at a fast rate of decrease, but also at a complete final removal.
In comparative example 1, the initial TN concentration was about 15mg/L, gradually decreased with time, and stabilized at 5 to 10mg/L after 20 days. This demonstrates that the filter material has some removal of total nitrogen, but has a slower rate of decrease and a higher final residual concentration, indicating that example 2, while continuing to remove total nitrogen, has insufficient efficiency and thoroughness, and is less effective than example 1.
In comparative example 2, the initial TN concentration was about 20mg/L, and after a certain decrease in the early stage, it was fluctuated between 10 and 15 mg/L. Surface comparative example 2, although having some removal of total nitrogen, was significantly weaker than example 1.
As can be seen from fig. 2:
In example 1, the initial removal rate was about 60%, followed by a rapid rise to approximately 100% on the order of 5 days, after which stability was maintained. This shows that the removal rate of example 1 is rapidly improved, the effect is remarkable and stable, and finally the pollutant in the sewage can be almost completely removed, and the extremely strong sewage treatment capability is exhibited.
In comparative example 1, the initial removal rate was about 55%, the overall tendency was upward, but there was some fluctuation in the process, and the final removal rate reached 80% or more. This illustrates that comparative example 1 has some removal capacity for contaminants, but the removal efficiency and stability are not as good as example 1.
In comparative example 2, the initial removal rate was about 45%, the initial removal rate was increased to a certain extent in the early stage, but the fluctuation range was large, and the initial removal rate was increased to 70% more in the later stage, but the overall removal rate was slow and the stability was poor, unlike example 1, the removal effect was weak.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.