Tea polyphenol modified polyferric flocculant as well as preparation method and application thereof

Abstract

The invention discloses a tea polyphenol modified polyferric flocculant as well as a preparation method and application thereof, and belongs to the field of anaerobic fermentation biogas slurry dehydration. Polyferric sulfate is used as a chain main body, tea polyphenol is used as a cross-linking agent, the tea polyphenol and iron ions in the polyferric sulfate form chelating coordination bonds under an alkaline condition, and the polyferric sulfate modified polyferric flocculant is prepared. Meanwhile, hydrophilic ether oxygen bonds in polyethylene oxide are combined with phenolic hydroxyl groups to form hydrogen bonds, so that a three-component polymer network is formed. Compared with the conventional flocculant, the modified polyferric flocculant prepared by the invention has the advantages that the electrical neutralization capability is enhanced, the adsorption bridging capability and the net repair sweeping capability of the flocculant are improved through coordinate bonds and hydrogen bonds, the floc forming rate is higher, the floc is larger and higher in strength, the sedimentation rate is higher, and the turbidity and the organic matter removal rate are high.

Description

Technical Field

[0001] The invention belongs to the field of anaerobic fermentation biogas slurry dehydration, and specifically relates to a tea polyphenol modified poly-iron flocculant and a preparation method and application thereof. Background Art

[0002] With the rapid development of my country's economy and the improvement of people's living standards, the output of restaurant kitchen waste has increased year by year. It is usually a state of coexistence of solid and liquid. The composition is highly correlated with the eating habits of different places, but generally has the characteristics of high water content. Restaurant kitchen waste has brought huge challenges to the management and resource utilization of domestic waste due to its large volume, high water content and easy decay. Therefore, it has always occupied the main market of domestic waste treatment.

[0003] At present, the main methods for treating food waste at home and abroad include landfill, incineration and resource utilization (aerobic composting, anaerobic fermentation, feed, insect bioconversion) and other treatment technologies. The landfill of food waste is to bury it together with ordinary domestic waste in a landfill after classification, crushing and compaction. The landfill method is not only low-cost, has a large processing capacity, but also has a wide range of applications. However, the most significant problem with landfill treatment is that it will produce a foul odor, which will affect the lives of surrounding residents. In addition, the landfilled garbage will produce leachate containing carcinogens under the dual effects of microorganisms and high pressure. Once these leachates leak, they will cause secondary pollution to the water body; incineration uses high temperature (about 850-1000℃) to oxidize and decompose the organic matter in the garbage to achieve garbage reduction. The residue after incineration Only about 20% of the slag remains, and the volume is only about 10% of the original volume. The heat released during the incineration process can be used for power generation, heating and other purposes. However, toxic and harmful substances such as dioxins will be produced in the process, and the operation and maintenance costs are high, the energy consumption is large, and the technical requirements are high; aerobic composting is the oxidation decomposition and biosynthesis of aerobic microorganisms to convert organic matter into stable humus; food waste, feces, crop straw, etc. can be treated by aerobic composting, and the fertilizer obtained can improve the physical and chemical properties and microbial structure of the soil, but composting treatment cannot fully recover the rich nutrients in food waste, and there are poor quality and possible secondary pollution. The high moisture content, high oil content and high salt content of food waste will have an adverse effect on the activity of microorganisms, thus affecting the application of compost products on large-scale land. Feed processing can be carried out by biological and physical methods. The biological method is to use microbial cells to treat food waste. Through the growth, reproduction and metabolism of microorganisms, useful cells, enzymes and intermediate metabolites are accumulated, and protein feed can be made after drying. The physical method refers to dehydrating the food waste, using high temperature treatment to kill viruses, and then crushing and processing it into feed. Although high temperature treatment can effectively kill some viruses, it cannot It is guaranteed that all viruses are completely eliminated. If this kind of feed is used to feed animals, there may be a risk of spreading diseases. Therefore, the issue of biosafety limits the application and development of food waste feed. Insect bioconversion technology is to use the synergistic metabolism of specific organisms such as maggots, black soldier flies, mealworms, earthworms and environmental microorganisms under artificially controllable conditions to ultimately produce specific organisms such as maggots or black soldier flies. This technology is easy to operate, has low energy consumption, reduces processing costs, and brings economic, environmental and social benefits. However, due to the low degree of automation of its production equipment, high environmental control costs, and product sales problems, it is difficult to achieve large-scale production.

[0004] Kitchen waste is rich in organic matter, and its biogas production performance is about 15 times that of livestock and poultry manure. It is very suitable as an anaerobic fermentation substrate. Anaerobic fermentation of kitchen waste can reduce the impact on the environment and produce biogas. Biogas is a clean renewable energy source used for fuel and power generation. The generated biogas slurry and biogas residue can be used as organic fertilizer. Kitchen waste is placed in a closed fermentation tank to prevent the spread of odor. Therefore, anaerobic fermentation has become the mainstream technology for resource processing of kitchen waste due to its great energy recovery potential. However, due to the high water content of kitchen waste, a large amount of biogas residue and liquid is produced after anaerobic fermentation. It is an important link to achieve low-cost and efficient separation of biogas slurry and biogas residue.

[0005] The anaerobic fermentation liquid produced by food waste has a relatively high level of suspended solids, which are negatively charged and very stable, and the dehydration effect has always been poor. The main biogas slurry dehydration agent on the market is PAC, but the addition of PAC can easily lead to scaling and blockage of pipes, while affecting the efficiency of centrifuges, seriously affecting production operations; in addition, the addition of PAC is solid dissolution, which requires a large workload, produces a lot of solid waste, and has an overall high cost; at the same time, the clear liquid produced after the separation of biogas residue and biogas slurry also contains high COD and ammonia nitrogen concentrations, which do not meet the emission requirements. Therefore, further treatment is required to meet the emission indicators. Summary of the invention

[0006] The present invention provides a tea polyphenol modified polyferric flocculant and a preparation method and application thereof, which can enhance the electrical neutralization ability of the flocculant. The prepared flocculant has a relatively large network structure, thereby enhancing its net-catching ability, and the formed flocs are relatively strong and not easily destroyed by water flow compression, thereby achieving better flocculation performance with a relatively small flocculant dosage.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A method for preparing a tea polyphenol modified polyferric flocculant comprises the following steps:

[0009] Dissolve polyethylene oxide in deionized water, and stir for 30 to 60 minutes after the liquid becomes clear to obtain solution A;

[0010] Add tea polyphenols to solution A and stir at a certain temperature for 20 to 30 minutes to perform hydrogen bond formation reaction;

[0011] Polyferric sulfate is dissolved in water to obtain solution B, solution B is added into solution A after the reaction, pH value of the mixed solution is adjusted with NaOH solution, the mixed solution is stirred at a specific temperature, and then allowed to stand and mature to obtain a novel composite polyferric flocculant.

[0012] In the above steps, the stirring time after the polyethylene oxide is dissolved in water is 30 to 60 minutes, preferably 60 minutes;

[0013] The molar ratio of tea polyphenol to polyethylene oxide is (20-30):(30-40), preferably 25:30; after tea polyphenol is added to solution A, the stirring temperature is 20-30°C, preferably 25°C;

[0014] The molar ratio of the polyferric sulfate to tea polyphenols is (5-15):(20-40), preferably 8:25; the pH is adjusted to 7-10 with a NaOH solution; and the stirring temperature after the pH is adjusted is 20-30°C, preferably 25°C.

[0015] The tea polyphenol modified poly-iron flocculant prepared above has a large network structure and a large number of hydrogen bonds and coordination bonds; the specific structure is as follows:

[0016]

[0017] Beneficial effects: The present invention provides a tea polyphenol modified polyferric flocculant and a preparation method and application thereof, which has the following advantages over the prior art:

[0018] (1) Tea polyphenols have more phenolic hydroxyl groups, which can form chelate coordination bonds with iron ions in polyferric sulfate under alkaline conditions. At the same time, the main functional groups in polyethylene oxide are hydrophilic ether oxygen bonds, which are easier to combine with phenolic hydroxyl groups to form hydrogen bonds. Therefore, tea polyphenols can act as a crosslinking agent in the coagulation process of polyethylene oxide and polyferric sulfate, combining them to form a three-component polymer network with a large number of hydrogen bonds and coordination bonds, which makes the floccules have sufficient crosslinking degree and flocculation strength;

[0019] (2) Compared with conventional flocculants, the modified polyferric flocculant prepared by the present invention has electrical neutralization ability, and its adsorption bridging and net filling and sweeping abilities are greatly improved, the floc formation rate is faster, and the flocs are larger and stronger, the sedimentation rate is faster, the turbidity and organic matter removal rate are high, and the coagulation performance is better than conventional flocculants on the market;

[0020] (3) The preparation process of the present invention is simple to operate, requires fewer types of raw materials and is inexpensive, does not require the addition of a coagulant during the coagulation process, and no monomeric iron, tea polyphenols, and polyethylene oxide remain in the treated water, thereby reducing the preparation cost while ensuring the safety of the effluent water quality and no secondary pollution;

[0021] (4) Due to the introduction of tea polyphenols and polyethylene oxide, the network structure of the polyiron molecule is increased, the flocculation ability of the flocculant is greatly improved, and the amount of flocculant used is less, and the processing cost is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a reaction mechanism diagram of the preparation method in an embodiment of the present invention;

[0023] Figure 2 This is a comparison diagram between the biogas slurry raw water in the embodiment of the present invention and the experimental process. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0025] like Figure 1 As shown, there are hydrophilic ether oxygen bonds in polyethylene oxide, which can easily combine with the phenolic hydroxyl groups in tea polyphenols to form hydrogen bonds in the environment, thereby obtaining hydrogen bond combination products. Subsequently, polyferric sulfate is added under alkaline or slightly alkaline conditions. The polyferric sulfate contains trivalent iron ions, which can combine with the phenolic hydroxyl groups under alkaline conditions to form coordination bonds. This coordination bond is very stable, and finally a three-component polymer with tea polyphenols as a cross-linking agent is obtained.

[0026] Example 1

[0027] A method for preparing a novel poly-iron flocculant modified by tea polyphenols comprises the following steps:

[0028] 40 parts of polyethylene oxide are dissolved in deionized water by mole fraction, and then stirred for 50 minutes after the liquid becomes clear to obtain a polyethylene oxide solution; 30 parts of tea polyphenols are added to the polyethylene oxide solution, and magnetic stirring is performed at 25°C to first perform a hydrogen bond formation reaction; 10 parts of polyferric sulfate are dissolved in water to obtain a polyferric solution, and the polyferric solution is added to the polyethylene oxide solution after the reaction to obtain a mixed solution, and the pH of the mixed solution is adjusted to 10 with a NaOH solution, and the mixed solution is stirred at 20°C, and then allowed to stand and mature to obtain a new composite polyferric flocculant.

[0029] Example 2

[0030] A method for preparing a novel poly-iron flocculant modified by tea polyphenols comprises the following steps:

[0031] 30 parts of polyethylene oxide are dissolved in deionized water by mole fraction, and then stirred for 60 minutes after the liquid becomes clear to obtain a polyethylene oxide solution; 25 parts of tea polyphenols are added to the polyethylene oxide solution, and magnetic stirring is performed at 25°C to first perform a hydrogen bond formation reaction; 8 parts of polyferric sulfate are dissolved in water to obtain a polyferric solution, and the polyferric solution is added to the polyethylene oxide solution after the reaction to obtain a mixed solution, and the pH of the mixed solution is adjusted to 8.0 with a NaOH solution, and the mixed solution is stirred at 25°C, and then allowed to stand and mature to obtain a new composite polyferric flocculant.

[0032] The above embodiment and the traditional PAC and PFS flocculants were used for the dehydration test of anaerobic fermentation of kitchen waste. The mass ratio of the applied reagent stock solution to the original mud was 50000ppm. The water content of the anaerobic fermentation of kitchen waste was 97%, the pH was 8.0, the initial COD was 8338mg / L, the initial ammonia nitrogen was 3013.1mg / L, the initial TN was 3384.3mg / L, and the initial SS was 7895.5mg / L. The comparison results are as follows (in mg / L):

[0033] Table 1 Comparison of the results of the flocculants of the examples and the PAC flocculants used for the anaerobic fermentation of kitchen waste and the dehydration of biogas slurry

[0034] Sample name Outlet COD Ammonia nitrogen in effluent Outlet TN Outlet SS Example 1 4654 1863 2318 557 Example 2 4372 1677 2015 473 PAC 5191.8 2122.3 2611.8 3175

[0035] Table 2 Removal rates of various indicators of biogas slurry from anaerobic fermentation of kitchen waste by flocculants and PAC flocculants in the examples

[0036] Sample name COD removal rate Ammonia nitrogen removal rate TN removal rate SS removal rate Example 1 44.2％ 38.2％ 31.5％ 92.9％ Example 2 47.6％ 44.3％ 40.5％ 94％ PAC 37.7％ 29.6％ 22.8％ 60％

[0037] From the comparison results of Table 1 and Table 2 above, it can be found that the new polyiron flocculants prepared in Examples 1 and 2 have absolute advantages over traditional PAC in the dehydration effect of anaerobic fermentation sludge of food waste. At the same time, the flocculant prepared in Example 2 is better than that in Example 1, indicating that the preparation method of Example 2 is the best. This is because the ratio of polyethylene oxide and tea polyphenols selected in the production process of Example 2 and the stirring time for generating hydrogen bonds are better than those in Example 1, when the pH is adjusted with NaOH solution. Example 2 is adjusted to the optimal 8.0, which allows more coordination bonds to be generated subsequently, thereby forming a larger polymer network structure and a more stable flocculation structure. And as Figure 2 In the test process shown, the alum flocs are large and dense, and the flocs settle in layers with a fast settling speed.

[0038] The above are only preferred embodiments of the present invention, which are helpful for those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those skilled in the art, several modifications and improvements made without departing from the concept of the present invention are all protected by the present invention.

Claims

1. A tea polyphenol modified polyiron flocculant, characterized in that: The flocculant is a polymer network structure bonded by hydrogen bonds and coordination bonds.

2. The tea polyphenol modified polyiron flocculant according to claim 1, characterized in that: The structure of the flocculant is:

3. A method for preparing a tea polyphenol modified polyferric flocculant, characterized in that: The following steps are involved: Dissolve polyethylene oxide in deionized water, and stir until the liquid becomes clear to obtain solution A; Add tea polyphenols into solution A and stir to form hydrogen bonds; Polyferric sulfate is dissolved in water to obtain solution B, and solution B is added to solution A after hydrogen bond formation reaction, and the solution is stirred after adjusting pH, and then allowed to stand and mature to obtain a modified polyferric flocculant.

4. The method for preparing the tea polyphenol modified polyferric flocculant according to claim 3, characterized in that: The stirring time after the polyethylene oxide is dissolved in water is 30 to 60 minutes.

5. The method for preparing the tea polyphenol modified polyferric flocculant according to claim 3, characterized in that: The molar ratio of tea polyphenols to polyethylene oxide is (20-30):(30-40).

6. The method for preparing the tea polyphenol modified polyferric flocculant according to claim 3 or 5, characterized in that: After the tea polyphenols are added into solution A, the stirring temperature is 20-30°C.

7. The method for preparing the tea polyphenol modified polyferric flocculant according to claim 3, characterized in that: The molar ratio of the polymerized ferric sulfate to tea polyphenols is (5-15):(20-40).

8. The method for preparing the tea polyphenol modified polyferric flocculant according to claim 3, characterized in that: Adjust pH to 7-10.

9. The method for preparing the tea polyphenol modified polyferric flocculant according to claim 3 or 8, characterized in that: The stirring temperature after pH adjustment is 20 to 30°C.

10. The use of the tea polyphenol modified polyferric flocculant according to any one of claims 1 to 2, characterized in that: The flocculant is used for dehydrating biogas slurry from anaerobic fermentation of kitchen waste.

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