Plant source composite polymeric flocculant as well as preparation method and application thereof

Abstract

The invention provides a plant source composite polymeric flocculant as well as a preparation method and application thereof, and belongs to the field of water treatment. The flocculating agent is prepared from aloe powder, citrus peel powder and banana peel powder according to the mass ratio of (4.5-5.5): 1: 3. The preparation method comprises the following steps: mixing the three powders, sequentially carrying out supercritical CO2 fluid extraction, high-voltage pulsed electric field treatment and alcohol precipitation treatment, centrifuging, drying, crushing and sieving to obtain the product. The preparation method has the advantages of high extraction efficiency, no damage to the polysaccharide structure and the like. The raw materials are wide in source, low in cost, green and environment-friendly in preparation process, free of chemical reagent residues and secondary pollution risks, easy to biodegrade, safe and harmless. When being applied to the technical field of wastewater and sewage treatment, the water turbidity can be effectively reduced after stirring and standing.

Description

Technical Field

[0001] The present invention belongs to the field of water treatment and relates to a plant-derived composite polymer flocculant, a preparation method thereof, and an application thereof. Background Art

[0002] In the process of water treatment, flocculants play a key role. They can cause suspended solids, colloids and other substances in water to aggregate into larger particles, thus facilitating subsequent precipitation, filtration and other treatment steps. Although traditional chemical flocculants, such as aluminum salts, iron salts, etc., show excellent flocculation effects, they also have a series of problems that cannot be ignored. On the one hand, these chemical flocculants may cause secondary pollution during use, posing a potential threat to the environment and human health. For example, the residue of aluminum salt flocculants in water may increase the risk of diseases such as Alzheimer's disease. On the other hand, the production cost of chemical flocculants is relatively high, and their production processes are often accompanied by high energy consumption and environmental pollution.

[0003] With the increasing attention to environmental protection and sustainable development, plant flocculants, as a kind of natural, non-toxic and biodegradable flocculants, have gradually received extensive attention. They are environmentally friendly and do not cause secondary pollution. Secondly, plant flocculants have a wide range of sources, and many plant materials can be used as extraction raw materials, which makes it possible for their large-scale production. In addition, the production cost of plant flocculants is relatively low, and their production processes have low energy consumption, which conforms to the concept of sustainable development. However, there are still some deficiencies in the current extraction methods of plant flocculants. The existing extraction methods of plant flocculants have problems such as high extraction cost, low extraction efficiency, and may cause certain damage to the structure of polysaccharides, thus affecting the performance of plant flocculants.

[0004] For example, CN108128869A discloses a preparation method of a hybrid fruit peel-microbial integrated coagulant using banana peel and orange peel as raw materials. It uses an alkali extraction-thermal immersion-microbial compounding process to prepare the coagulant. Although it realizes the resource utilization of raw materials, the two thermal immersion processes (40 - 55°C for 0.5 - 2 hours) are prone to cause the breakage of polysaccharide chains, resulting in uneven molecular weight distribution. And CN106044984A discloses a preparation method of a plant-derived natural polymer flocculant. By etherifying and microwave-modifying the composite system of aloe vera gel and konjac starch, although a flocculant with an increased cationic degree is obtained, the processes involved such as cation exchange, microbial modification, and etherifying microwave modification significantly increase the production cost.

[0005] Therefore, in order to solve the deficiencies of the existing extraction methods of plant flocculants, a more efficient and environmentally friendly extraction technology is needed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is the problem that in the existing preparation methods of plant flocculants, the extraction cost is high, the extraction efficiency is low, and the polysaccharide structure is damaged, thus affecting the flocculation effect.

[0007] To achieve the above application purpose, the technical solution adopted in this application is as follows:

[0008] In the first aspect, the present invention provides a plant-derived composite polymer flocculant. The preparation raw materials of the flocculant include aloe powder, citrus peel powder, and banana peel powder, and the mass ratio of the three is 4.5 - 5.5:1:3.

[0009] Furthermore, the above plant-derived composite polymer flocculant is in powder form, and its powder particle size is less than 80 mesh.

[0010] In the second aspect, the present invention provides a preparation method of the above plant-derived composite polymer flocculant. Mix aloe powder, citrus peel powder, and banana peel powder according to the mass ratio of 4.5 - 5.5:1:3 to obtain a plant composite powder; perform supercritical CO2 fluid extraction, high-voltage pulsed electric field treatment, and alcohol precipitation treatment on the plant composite powder, and after centrifugation, take the precipitate and dry it to obtain the plant-derived composite polymer flocculant.

[0011] Furthermore, the particle size of the above aloe powder is less than 80 mesh, and it is prepared by washing fresh aloe, removing thorns, drying at 55 - 65 °C, pulverizing, and then sieving.

[0012] Furthermore, the particle size of the above citrus peel powder is less than 80 mesh, and it is prepared by washing citrus peel, drying at 55 - 65 °C, pulverizing, and then sieving.

[0013] Furthermore, the particle size of the above banana peel powder is less than 80 mesh, and it is prepared by washing banana peel, drying at 55 - 65 °C, pulverizing, and then sieving.

[0014] In the above preparation method, during supercritical CO2 fluid extraction, static extraction is first performed, and the static extraction time is 1 h; then an ethanol solution is pumped into the system by an entrainer pump for dynamic extraction, and the dynamic extraction time is 10 - 50 min.

[0015] Furthermore, the conditions for the above supercritical CO2 fluid extraction are: the CO2 purity is 99.99%; the extraction kettle pressure is 20 - 30 MPa, the temperature is 25 - 40 °C, and the analytical pressure is 4 MPa; the entrainer is anhydrous ethanol, and the entrainer dosage is 1.5 - 3.5 ml / g.

[0016] In the above preparation method, the conditions for high-voltage pulsed electric field treatment are: the extraction time is 30 - 60 min, the electric field strength is 10 - 30 kV / cm, and the number of pulses is 2 - 10.

[0017] In the above preparation method, the alcohol precipitation treatment is as follows: anhydrous ethanol is added to the product treated by high-voltage pulsed electric field, and after mixing evenly, an alcohol precipitation solution is obtained, and then it is left standing at 4°C for 2 h; the volume concentration of ethanol in the alcohol precipitation solution is greater than 85%.

[0018] In the above preparation method, after the alcohol precipitation treatment is completed, the product is centrifuged at a speed of 5000 r / min for 20 min at room temperature, the precipitate is taken, dried at 60°C and then pulverized, and passed through an 80-mesh sieve to obtain the plant-derived composite polymer flocculant.

[0019] In the third aspect, the present invention provides the application of the above plant-derived composite polymer flocculant, or the plant-derived composite polymer flocculant prepared by the above preparation method, in the technical field of wastewater and sewage treatment. The specific application method is as follows: the plant-derived composite polymer flocculant is added into the water body to be treated at a dosage of 10-25 mg / L, first rapidly stirred at a speed of 200 r / min for 1 min, then moderately stirred at a speed of 60 r / min for 10 min, and finally slowly stirred at a speed of 40 r / min for 5 min. After the stirring is completed, it is left standing for sedimentation for 15 min, and that's it.

[0020] The beneficial effects of the present invention: Through the multi-source composite ratio design of aloe vera, citrus peel and banana peel, the present invention constructs a polymer flocculation system. And adopting the technical route of supercritical CO2 fluid extraction coupled with high-voltage pulsed electric field treatment to break through the bottleneck of traditional processes, which is specifically reflected in the following advantages:

[0021] (1) The present invention uses the method of supercritical coupling high-voltage pulsed electric field to extract polysaccharides. The strong permeability of supercritical CO2 and the cell wall breaking effect of high-voltage pulsed electric field form a double strengthening mechanism, realizing the efficient release of polysaccharide substances in plant cell walls under low-temperature conditions, with high extraction efficiency and capable of obtaining a high polysaccharide extraction rate in a relatively short time.

[0022] (2) The extraction method of the present invention is a non-thermal processing technology, avoiding the risk of thermal degradation, not damaging the structure and biological activity of polysaccharides, ensuring the integrity of the molecular weight of active ingredients and the stability of the spatial conformation, and the polysaccharides extracted have high purity and activity.

[0023] (3) The present invention establishes a high-value utilization path for agricultural waste by optimizing the component ratio. Using aloe vera, citrus peel and banana peel as raw materials to prepare plant flocculants, the raw materials are widely sourced and low-cost; the preparation process is green and environmentally friendly. By the synergistic action of non-thermal physical fields to replace the traditional acid-base leaching process, the risk of chemical reagent residues is eliminated and no secondary pollution will be generated; at the same time, the plant-derived composite polymer flocculant of the present invention is easily biodegradable and will not cause harm to the environment and human body. Detailed implementation manners

[0024] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following further elaborates on this application in combination with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those of ordinary skill in the art.

[0025] The preparation principle of the plant-derived composite polymer flocculant described in the present invention is based on the following synergistic action mechanism:

[0026] Supercritical CO2 fluid combines the high diffusivity of gas and the strong dissolving power of liquid, and can effectively penetrate into the interior of plant cells, destroy the cell wall structure, and accelerate the dissolution of polysaccharides by dissolving the lipid layer of the cell wall. The high-voltage pulsed electric field technology utilizes the electropermeabilization effect of the high-voltage pulsed electric field on the cell membrane to further destroy the cell structure and promote the release and diffusion of polysaccharides. The synergistic action of the two physical field technologies realizes the efficient extraction of active components such as plant polysaccharides under non-thermal conditions, with the advantages of short extraction time, high extraction efficiency, and little damage to the polysaccharide structure. This process replaces chemical extraction with physical cell wall breaking, while ensuring a high polysaccharide extraction rate, avoiding the risk of organic solvent residues, and the obtained flocculant has both high flocculation activity and environmental sustainability.

[0027] Specific embodiments will be listed below to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0028] Embodiment

[0029] I. Raw material preparation

[0030] The fresh aloe vera is washed with tap water, de-spined, dried at 60 °C, pulverized, and sieved through an 80-mesh sieve to obtain aloe vera powder.

[0031] The discarded citrus peels are washed with tap water, dried at 60 °C, pulverized, and sieved through an 80-mesh sieve to obtain citrus peel powder.

[0032] The discarded banana peels are washed with tap water, dried at 60 °C, pulverized, and sieved through an 80-mesh sieve to obtain banana peel powder.

[0033] II. Preparation and performance testing of the plant-derived composite polymer flocculant

[0034] 1. Preparation of the plant-derived composite polymer flocculant, the specific steps are as follows:

[0035] (1) Mix aloe powder, citrus peel powder, and banana peel powder in a mass ratio of 4.5 - 5.5:1:3 to obtain a plant composite powder. The specific raw material ratios are shown in Table 1.

[0036] Table 1 Raw Material Ratios (Aloe Powder: Citrus Peel Powder: Banana Peel Powder)

[0037] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Mass ratio 4.5:1:3 4.9:1:3 5.5:1:3 4.8:1:3 5.0:1:3 4.9:1:3

[0038] (2) According to the process parameters described in Table 2, use supercritical CO2 fluid to extract the plant composite powder. First, perform static extraction for 1 h; then use an entrainer pump to pump the ethanol solution into the system and perform dynamic extraction for 10 - 50 min. The specific parameters are as follows: CO2 purity is 99.99%; the extraction kettle pressure is 20 - 30 MPa, the extraction kettle temperature is 25 - 40 °C, the analytical pressure is 4 MPa, the entrainer is anhydrous ethanol, and the entrainer dosage is 1.5 - 3.5 ml / g.

[0039] (3) Feed the product processed in step (2) into the high - voltage pulsed electric field treatment chamber and perform treatment in the high - voltage pulsed electric field according to the process parameters shown in Table 2 to obtain an extract. The specific parameters are as follows: extraction time is 30 - 60 min, electric field strength is 10 - 30 kV / cm, and the number of pulses is 2 - 10.

[0040] Table 2 Process Parameters

[0041]

[0042] (4) Transfer the extract to an Erlenmeyer flask, add anhydrous ethanol to obtain an alcohol precipitation solution, and then let it stand at 4 °C for 2 h. The volume concentration of ethanol in the alcohol precipitation solution is greater than 85%.

[0043] (5) Use a centrifuge to centrifuge the product processed in step (4) at a speed of 5000 r / min for 20 min, collect the lower - layer white solid, put it in an oven to dry at 60 °C and then crush it, and pass it through an 80 - mesh sieve to obtain a powdery plant - derived composite polymer flocculant.

[0044] (6) The yields of polysaccharides extracted in Examples 1 - 6 were detected to be 37.54%, 45.75%, 41.34%, 50.79%, 56.23%, and 60.34% respectively.

[0045] 2. Application examples and application effects are as follows:

[0046] 18 mg of the plant-derived composite polymer flocculants prepared in Examples 1-6 were respectively added to 1 L of kaolin suspension (configured turbidity: 200 NTU). First, it was rapidly stirred at a speed of 200 r / min for 1 min, then moderately stirred at a speed of 60 r / min for 10 min, and finally slowly stirred at a speed of 40 r / min for 5 min. After the stirring ended, it was allowed to stand and settle for 15 min. After that, the turbidity reduction rates of the application examples of Examples 1-6 were detected to be 85.5%, 95.6%, 87.1%, 96.4%, 97.5%, and 98.3% respectively.

[0047] III. Comparative Tests between Different Plant Flocculants and Plant-Derived Composite Polymer Flocculants

[0048] Taking the preparation method and the obtained plant-derived composite polymer flocculant of Example 6 as a reference, comparative tests were carried out on flocculants with different preparation raw materials and different preparation processes.

[0049] 1. Prepare the flocculant according to the preparation method of Example 6 above. The differences between each comparative example and Example 6 are as follows, and the rest of the preparation processes and parameters are the same as those of Example 6.

[0050] Comparative Example 1: In step (1), the plant composite powder was replaced with aloe powder in equal amounts.

[0051] Comparative Example 2: In step (1), the plant composite powder was replaced with citrus peel powder in equal amounts.

[0052] Comparative Example 3: In step (1), the plant composite powder was replaced with banana powder in equal amounts.

[0053] Comparative Example 4: In step (1), the plant composite powder was replaced with a mixture of aloe powder and citrus peel powder in a mass ratio of 4.9:1.

[0054] Comparative Example 5: In step (1), the plant composite powder was replaced with a mixture of aloe powder and banana peel powder in a mass ratio of 4.9:3.

[0055] Comparative Example 6: In step (1), the plant composite powder was replaced with a mixture of citrus peel powder and banana peel powder in a mass ratio of 1:3.

[0056] Comparative Example 7: The high-voltage pulsed electric field treatment in step (3) was not carried out, and after the supercritical CO2 fluid extraction in step (2), it entered step (4) for alcohol precipitation treatment.

[0057] Comparative Example 8: The supercritical CO2 fluid extraction in step (2) was not carried out, and the plant composite powder was directly sent to step (3) for high-voltage pulsed electric field treatment.

[0058] 2. The polysaccharide yields of different preparation processes were detected, and the results are shown in Table 3. 18 mg of the flocculants prepared in Example 6 and Comparative Examples 1-8 were respectively added to 1 L of kaolin suspension (configured with a turbidity of 200 NTU). First, it was rapidly stirred at a speed of 200 r / min for 1 min, then moderately stirred at a speed of 60 r / min for 10 min, and finally slowly stirred at a speed of 40 r / min for 5 min. After the stirring was completed, it was allowed to stand and settle for 15 min, and then the turbidity removal rates of the application examples of Comparative Examples 1-8 and the zeta potentials before and after the treatment of the kaolin suspension were detected. The results are shown in Table 3.

[0059] Table 3 Comparison of the treatment effects of flocculants

[0060]

[0061]

Claims

1. A plant-derived composite polymer flocculant, characterized in that: The raw materials for preparing the flocculant include aloe powder, citrus peel powder, and banana peel powder, and the mass ratio of the three is 4.5 - 5.5:1:

3.

2. The plant-derived composite polymer flocculant according to claim 1, wherein: The flocculant is in powder form, and the particle size of the powder is less than 80 mesh.

3. Preparation method of a plant-derived composite polymer flocculant, characterized in that: Mix aloe powder, citrus peel powder, and banana peel powder according to a mass ratio of 4.5 - 5.5:1:3 to obtain a plant composite powder; Perform supercritical CO2 fluid extraction, high-voltage pulsed electric field treatment, and alcohol precipitation treatment on the plant composite powder, centrifuge, and take the precipitate to be dried to obtain a plant-derived composite polymer flocculant.

4. The preparation method of the plant-derived composite polymer flocculant according to claim 3, characterized in that: The particle size of the aloe powder is less than 80 mesh, and it is obtained by washing fresh aloe, removing thorns, drying at 55 - 65 °C, pulverizing, and then sieving; The particle size of the citrus peel powder is less than 80 mesh, and it is obtained by washing citrus peel, drying at 55 - 65 °C, pulverizing, and then sieving; The particle size of the banana peel powder is less than 80 mesh, and it is obtained by washing banana peel, drying at 55 - 65 °C, pulverizing, and then sieving.

5. The preparation method of the plant-derived composite polymer flocculant according to claim 3, characterized in that: During the supercritical CO2 fluid extraction, first perform static extraction, and the static extraction time is 1 h; then use an entrainer pump to pump an ethanol solution into the system for dynamic extraction, and the dynamic extraction time is 10 - 50 min.

6. The preparation method of the plant-derived composite polymer flocculant according to claim 5, characterized in that: The conditions for the supercritical CO2 fluid extraction are: the purity of CO2 is 99.99%; the pressure in the extraction kettle is 20 - 30 MPa, the temperature is 25 - 40 °C, and the analytical pressure is 4 MPa; the entrainer is anhydrous ethanol, and the amount of the entrainer is 1.5 - 3.5 ml / g.

7. The preparation method of the plant-derived composite polymer flocculant according to claim 3, characterized in that: The conditions for the high-voltage pulsed electric field treatment are: the extraction time is 30 - 60 min, the electric field strength is 10 - 30 kV / cm, and the number of pulses is 2 - 10.

8. The preparation method of the plant-derived composite polymer flocculant according to claim 3, characterized in that: The alcohol precipitation treatment is: add anhydrous ethanol to the product treated by the high-voltage pulsed electric field, mix evenly to obtain an alcohol precipitation solution, and then let it stand at 4 °C for 2 h; the volume concentration of ethanol in the alcohol precipitation solution is greater than 85%.

9. The preparation method of the plant-derived composite polymer flocculant according to claim 3, characterized in that: After the alcohol precipitation treatment, centrifuge the product at a speed of 5000 r / min at room temperature for 20 min, take the precipitate, dry it at 60 °C, pulverize it, and sieve it through 80 mesh to obtain a plant-derived composite polymer flocculant.

10. Use of the plant-derived composite polymer flocculant according to any one of claims 1 to 2, or the plant-derived composite polymer flocculant prepared by the preparation method according to any one of claims 3 to 9, in the technical field of wastewater and sewage treatment, characterized in that: The specific application method is to add the plant-derived composite polymer flocculant into the water to be treated at a dosage of 10 - 25 mg / L, first stir at a speed of 160 - 200 r / min for 1 - 3 min, then stir at a speed of 40 - 60 r / min for 10 - 15 min, and finally stir at a speed of 30 - 40 r / min for 5 - 10 min. After the stirring ends, let it stand for sedimentation for 15 - 30 min.

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