Composite carrier material for biological fluidized bed and preparation method thereof
Technical Field
The invention relates to a water treatment carrier material, in particular to a composite carrier material for a biological fluidized bed and a preparation method thereof.
Background
The wastewater treatment is generally performed by an adsorption method, a flocculation precipitation method, a biodegradation method, and the like, and the results have been obtained in the past research. However, as society continues to grow, treatment methods and agents also need to be updated. In the early 19 th century, biological contact oxidation ponds have emerged, which treat domestic sewage with crushed stones, slag, etc. as biological fillers. For the anaerobic filter, the requirement on the density of the carrier is strict because the anaerobic section cannot perform aeration stirring, and the suspension is difficult if the density of the carrier is too high, and the fluidization of the carrier is not facilitated if the density of the carrier is too low; meanwhile, the particle size, porosity and the like of the carrier are considered, and the proper carrier is selected to have great influence on the fixation growth of organisms under the anaerobic condition.
Microorganism immobilization carriers are classified into inorganic carrier materials, natural polymers, organic polymers, and the like, and the corresponding immobilization methods are different and include an adsorption method, an embedding method, and a crosslinking method. Along with the development of social science and technology and social progress, the single microorganism immobilization carrier can not meet social requirements, the composite carrier material is formed by combining inorganic and organic carriers, the overall performance of immobilized microorganisms can be improved, the microbial activity of the immobilized microorganisms can be ensured under the condition of obtaining higher immobilization strength, the problems of weak binding strength and low adsorption performance of the single carrier are solved, the comprehensive effect is better, the composite carrier material can be used for treating various types of wastewater, but the pertinence is relatively poor; and when carrier materials with different properties are used in a composite way, the carrier materials are easily influenced by the volume of a fluidized bed, the fluidization speed and the like.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a composite carrier material which has moderate carrier density and is suitable for a biological fluidized bed.
In order to achieve the purpose, the invention provides the following technical scheme:
a preparation method of a composite carrier material for a biological fluidized bed comprises the following steps:
1) placing diatomite in a sodium hydroxide solution, soaking for 1h at 40 ℃, taking out, washing with water until the surface is neutral, and then calcining for 2h at 450 ℃; cooling to room temperature, adding into hydrochloric acid solution, soaking at 40 deg.C for 1h, taking out, washing with water until the surface is neutral, calcining at 450 deg.C for 1h, washing with water, and drying to obtain purified diatomite;
2) adding the purified diatomite and a silane coupling agent into anhydrous toluene together, performing ultrasonic treatment to uniformly disperse the purified diatomite and the silane coupling agent, heating and refluxing for 4-5h, naturally cooling, centrifuging, collecting solids, washing the solids with ethanol, drying, and grinding to obtain modified diatomite powder;
3) adding ethanol and water with a certain volume into a reaction bottle, adding the modified diatomite powder into the reaction bottle under the protection of nitrogen, stirring to uniformly disperse the modified diatomite powder, then continuously adding acrylamide and polyethylene glycol methacrylate into the reaction bottle, heating to 70 ℃, dropwise adding an aqueous solution of ammonium persulfate while stirring, continuously stirring for reaction for 4 hours after the dropwise addition is finished, and filtering and drying after the reaction is finished to obtain polymer grafted modified diatomite powder;
4) dispersing the polymer graft modified diatomite powder in ethanol according to the mass fraction of 20 wt%, adding activated carbon, performing ultrasonic treatment to uniformly disperse the polymer graft modified diatomite powder, then performing spray drying, collecting dried microspheres, and drying in a drying box to obtain the composite carrier material for the biological fluidized bed.
Further, the concentration of the sodium hydroxide solution and the hydrochloric acid solution in the step 1) is 1 mol/L.
Further, the mass ratio of the purified diatomite to the silane coupling agent in the step 2) is 1: 1.5-2.5.
Further, in the step 3), the volume ratio of the ethanol to the water is 1:1, the mass volume ratio of the modified diatomite powder to the ethanol is 1/20g/ml, the mass of the acrylamide and the polyethylene glycol methacrylate is 1-10% and 0.5-1% of that of the modified diatomite powder, and the mass of the ammonium persulfate is 1.0-2.0% of that of the acrylamide.
Further, the mass ratio of the activated carbon to the polymer grafted modified diatomite powder in the step 4) is 0.5-1: 1.
Further, the silane coupling agent is one selected from the group consisting of KH560, KH570, KH540, KH792 and a 171.
Further, the silane coupling agent is KH 570.
Furthermore, the activated carbon is activated by taking peanut shells, coconut shells, sawdust or straws as raw materials and potassium hydroxide as an activating agent.
The scheme provides a composite carrier material for a biological fluidized bed prepared by the preparation method.
The composite carrier material can integrate the advantages of different carrier materials, but the advantages of the materials are difficult to be utilized to the maximum only by a simple physical mixing mode, and the defects of the materials exist in a system and are not eliminated or weakened, so that the final use effect of the materials can be influenced. According to the scheme, firstly, diatomite is purified in a mode of alkali etching-calcining-acid etching-calcining to form a better small-hole structure; and then, carrying out graft modification on the purified diatomite by using a silane coupling agent, wherein the silane coupling agent can be used as a bridge for connecting between an inorganic phase and an organic phase, the methoxysilane and the diatomite surface molecules act to form a covalent bond, and active functional groups at the tail end, such as double bonds, amino groups and the like, can react with an organic polymer. The diatomite and the organic polymer are combined in a chemical bond mode, so that the adhesive force of microorganisms on the carrier material can be ensured, and the strength of the carrier material and the resistance to temperature, pH and other influencing factors can also be ensured.
In the scheme, KH570 and diatomite are preferably selected for grafting modification, methacryloxy is introduced to the tail end of the diatomite, and the diatomite, acrylamide and polyethylene glycol methacrylate are subjected to free radical polymerization to form a random copolymer, wherein the diatomite exists in a polymer branched chain. Compared with the method that the diatomite is coated in the polymer, the diatomite exposed outside the polymer chain can utilize the porous structure of the diatomite to the maximum extent to improve the adsorption capacity of the composite carrier material, and the introduction of the hydrophilic polymer chain increases the hydrophilicity of the composite carrier material, thereby greatly improving the biofilm formation efficiency.
The activated carbon can be prepared by sintering and activating biomass materials such as straw, sawdust and coconut shell, is easy to obtain raw materials and low in cost, has rich porous structures in the activated carbon material structure, is high in stability, and can adsorb microorganisms through the pore structures. However, if the amount of the activated carbon is too large, the activated carbon particles are easily overlapped to influence the number of surface adsorption sites, thereby reducing the adsorption effect of microorganisms. According to the scheme, the activated carbon and the polymer grafted and modified diatomite powder are jointly dispersed in the ethanol, the activated carbon is uniformly dispersed on the surface of the polymer grafted and modified diatomite powder by utilizing the characteristic of easy association between hydrophobic substances, the composite carrier microspheres are formed by spray drying, and various types of carrier materials are combined together through a certain chemical bond and intermolecular association, so that the composite carrier microspheres with uniform size and moderate density are obtained.
The invention has the beneficial effects that: the composite carrier material is formed by compounding the inorganic carrier and the organic carrier, optimizes the characteristics of the composite carrier material, simultaneously weakens the defects of each type of carrier material, obtains carrier microspheres with uniform size and moderate density, and jointly plays the characteristics of the material as a whole, thereby enhancing the adhesive force with microorganisms, being beneficial to the growth of the microorganisms in biofilm formation, having short biofilm formation time and improving the water treatment efficiency; the influence of the water environment is small, the density is moderate, and the fluidization is easy; the carrier material can be used as a place for the attachment growth of microorganisms, has certain adsorption and flocculation capacity, can effectively adsorb metal ions and organic pollutants in wastewater, and can be degraded by microorganisms to ensure that the water body is treated more thoroughly.
Drawings
FIG. 1 is a scanning electron microscope image of the composite carrier material of example 1 of the present application.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
A preparation method of a composite carrier material for a biological fluidized bed comprises the following steps:
1) weighing kieselguhr, placing the kieselguhr into 1mol/L sodium hydroxide solution, soaking for 1h at 40 ℃, taking out the kieselguhr, washing with water until the surface is neutral, and then calcining for 2h at 450 ℃; cooling to room temperature, adding the solution into 1mol/L hydrochloric acid solution, soaking at 40 ℃ for 1h, taking out the solution, washing with water until the surface is neutral, calcining at 450 ℃ for 1h, washing with water and drying to obtain purified diatomite;
2) adding purified diatomite and KH570 into anhydrous toluene together according to the mass ratio of 1:2, performing ultrasonic treatment to uniformly disperse the diatomite and the KH570, heating and refluxing for 4-5h, naturally cooling, centrifuging, collecting solids, washing the solids with ethanol, drying, and grinding to obtain modified diatomite powder;
3) respectively adding ethanol and water with the same volume into a reaction bottle, adding modified diatomite powder into the reaction bottle under the protection of nitrogen, stirring to uniformly disperse the modified diatomite powder, then continuously adding acrylamide and polyethylene glycol methacrylate (Mn is 400g/mol), heating to 70 ℃, dropwise adding an aqueous solution of ammonium persulfate while stirring, continuously stirring for reacting for 4 hours after the dropwise adding is finished, and filtering and drying after the reaction is finished to obtain polymer grafted modified diatomite powder; wherein, the mass of the acrylamide and the polyethylene glycol methacrylate is 5 percent and 0.5 percent of the modified diatomite powder, and the mass of the ammonium persulfate is 1.0 percent of the mass of the acrylamide.
4) Dispersing the polymer grafted modified diatomite powder in ethanol according to the mass fraction of 20 wt%, adding activated carbon, performing ultrasonic treatment to uniformly disperse the polymer grafted modified diatomite powder, then performing spray drying, collecting dried microspheres, and drying in a drying box to obtain a composite carrier material for the biological fluidized bed; the mass ratio of the activated carbon to the polymer graft modified diatomite powder is 1: 2.
As shown in fig. 1, the micro-morphology of the composite carrier material shows a spherical shape with uniform size and a rough spherical surface, which indicates that the activated carbon is dispersed on the surface of the polymer graft modified diatomite powder.
Example 2:
1) weighing kieselguhr, placing the kieselguhr into 1mol/L sodium hydroxide solution, soaking for 1h at 40 ℃, taking out the kieselguhr, washing with water until the surface is neutral, and then calcining for 2h at 450 ℃; cooling to room temperature, adding the solution into 1mol/L hydrochloric acid solution, soaking at 40 ℃ for 1h, taking out the solution, washing with water until the surface is neutral, calcining at 450 ℃ for 1h, washing with water and drying to obtain purified diatomite;
2) adding purified diatomite and KH570 into 50ml of anhydrous toluene together according to the mass ratio of 1:2, performing ultrasonic treatment to uniformly disperse the diatomite, heating and refluxing for 4-5h, naturally cooling, centrifuging, collecting solids, washing the solids with ethanol, drying, and grinding to obtain modified diatomite powder;
3) respectively adding ethanol and water with the same volume into a reaction bottle, adding modified diatomite powder into the reaction bottle under the protection of nitrogen, stirring to uniformly disperse the modified diatomite powder, then continuously adding acrylamide and polyethylene glycol methacrylate (Mn is 400g/mol), heating to 70 ℃, dropwise adding an aqueous solution of ammonium persulfate while stirring, continuously stirring for reacting for 4 hours after the dropwise adding is finished, and filtering and drying after the reaction is finished to obtain polymer grafted modified diatomite powder; wherein, the mass of the acrylamide and the polyethylene glycol methacrylate is 10 percent and 1 percent of the modified diatomite powder, and the mass of the ammonium persulfate is 1.0 percent of the acrylamide.
4) Dispersing the polymer grafted modified diatomite powder in ethanol according to the mass fraction of 20 wt%, adding activated carbon, performing ultrasonic treatment to uniformly disperse the polymer grafted modified diatomite powder, then performing spray drying, collecting dried microspheres, and drying in a drying box to obtain a composite carrier material for the biological fluidized bed; the mass ratio of the activated carbon to the polymer graft modified diatomite powder is 1:1.
Example 3:
the difference from embodiment 2 is that KH570 is replaced with KH 560.
Example 4:
the difference from example 2 is that KH570 was replaced with KH560 and step 4) was to mix the polymer graft modified diatomaceous earth powder directly with activated carbon.
In the embodiment, the activated carbon is activated by taking peanut shells, coconut shells, sawdust or straws as raw materials and potassium hydroxide as an activating agent; the activation method is the prior art in the field, and the scheme is not limited.
The mechanical properties are determined according to whether the carrier material is dissolved out or broken after continuous mechanical stirring.
TABLE 1
|
Particle size nm
|
Density g/cm3 |
Mechanical Properties
|
Example 1
|
200
|
0.952
|
Is not dissolved out and broken
|
Example 2
|
190
|
0.961
|
Is not dissolved out and broken
|
Example 3
|
1000
|
1.13
|
Dissolution and non-cracking
|
Example 4
|
2000
|
1.25
|
Dissolution and rupture |
The composite carrier materials of the above examples 1-4 were added to a bioreactor, and the biofilm formation time of example 1 was 5 days, the biofilm formation time of example 2 was 5 days, the biofilm formation time of example 3 was 8 days, and the biofilm formation time of example 4 was 12 days. By combining the table 1, the composite carrier material of the scheme has moderate density, easy fluidization, good mechanical property and high stability; is favorable for the attached growth of microorganisms and has short biofilm formation time. Example 3 connecting diatomaceous earth, acrylamide and polyethylene glycol methacrylate with KH560 silane coupling agent; the diatomite is wrapped in the polymer, so that the association with the activated carbon is weakened, the mechanical property is reduced, and the film hanging time is prolonged. Example 4 composite carrier materials were prepared by physical mixing only, and the materials were poorly miscible and therefore mechanically inferior and the film formation time was also longer.
While embodiments of the invention have been disclosed above, it is not limited to the applications listed in the description and the embodiments, which are fully applicable in all kinds of fields of application of the invention, and further modifications may readily be effected by those skilled in the art, so that the invention is not limited to the specific details and examples shown and described herein, without departing from the general concept defined by the claims and their equivalents.