Degradable bioflocculating precipitants and methods for their production

Abstract

The application relates to the field of water treatment, and particularly discloses a degradable biological flocculation precipitator and a preparation method thereof. The degradable biological flocculation precipitator comprises a degradable capsule wall material and a capsule core biological flocculation agent wrapped in the capsule wall material, the degradable capsule wall material comprises modified chitosan, sodium octenyl succinate starch, sucrose ester and calcium carbonate, and the modified chitosan is prepared by modifying chitosan with polyethylene glycol. The preparation method comprises the following steps: configuring an aqueous phase containing the capsule wall material; dispersing the biological flocculation agent in the aqueous phase containing the capsule wall material to prepare an emulsion; and performing low-temperature vacuum spray drying on the emulsion to form microcapsules, so that the degradable biological flocculation precipitator is obtained. The composition disclosed by the application can be used for sewage treatment, water purification treatment and the like, and has the advantages of good stability and good flocculation effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water treatment, more particularly, it relates to a degradable biological flocculation precipitant and a preparation method thereof. BACKGROUND

[0002] The degradable biological flocculation precipitant is a new type of environmental protection agent widely used in the field of water treatment. It produces metabolites with flocculation activity through microbial technology, which can effectively precipitate suspended solids, colloids and other impurities in water to form flocculation, thereby improving water quality. Compared with traditional flocculants, the degradable biological flocculation precipitant has the advantages of degradability, environmental protection, etc., and meets people's requirements for environmental protection and health. Therefore, it has broad application prospects in the fields of drinking water treatment, industrial wastewater treatment, municipal sewage treatment, etc.

[0003] In the preparation process of the degradable biological flocculation precipitant, microbial fermentation or enzymatic reaction methods are usually used, which can produce biological macromolecules with flocculation activity. However, these biological macromolecules are often susceptible to external environmental factors such as temperature, pH value, ionic strength, etc., resulting in poor stability of the prepared flocculant. In addition, the interaction between biological macromolecules can also lead to a decrease in their stability, and these metabolites are prone to decomposition or inactivation during storage and use, thereby affecting the stability and flocculation effect of the flocculant.

[0004] Therefore, how to improve the stability of the degradable biological flocculation precipitant is a problem to be solved at present. SUMMARY

[0005] In order to improve the stability of the degradable biological flocculation precipitant, the present application provides a degradable biological flocculation precipitant and a preparation method thereof.

[0006] In the first aspect, the present application provides a degradable biological flocculation precipitant, which adopts the following technical solution:

[0007] The degradable biological flocculation precipitant comprises a degradable capsule wall material and a capsule core biological flocculant wrapped therein, the degradable capsule wall material comprises modified chitosan, octenyl succinate sodium starch, sucrose ester and calcium carbonate, and the modified chitosan is prepared by modifying chitosan with polyethylene glycol.

[0008] By adopting the above technical solution, the biological flocculant is prone to decomposition and inactivation during storage and transportation, and has poor stability. The biological flocculant is wrapped with a degradable capsule wall material to form a microcapsule, which forms a protective layer to prevent the external environment from damaging the flocculant, thereby improving the stability of the biological flocculant. The capsule wall material is made of a hydrophilic material that is easily soluble in water, and when the biological flocculation precipitant is put into water for water treatment, the hydrophilic material quickly dissolves to release the biological flocculant for flocculation and precipitation.

[0009] The chitosan modified by polyethylene glycol has good affinity for water, can be quickly dissolved in water, release the bioflocculants, improve the stability of the bioflocculants, and the large molecular weight and good water solubility of the polyethylene glycol can help to stabilize the structure of the bioflocculants, maintain the activity of the flocculating and precipitating agent, make it more effectively combined with impurity ions, and the hydroxyl and ether bond on the polyethylene glycol can form stable coordination bonds with heavy metal ions, help to precipitate and remove the heavy metal ions.

[0010] Optionally, the degradable capsule wall material comprises 2-5 parts of modified chitosan, 1-3 parts of sodium octenyl succinate starch, 0.5-1 part of sucrose ester, and 1-2 parts of calcium carbonate.

[0011] By adopting the above technical solution, the storage stability and water solubility of the capsule wall material components are good, and the capsule wall material can be quickly dissolved when contacted with water. The calcium carbonate and sucrose ester have good synergistic effect. The addition of sucrose ester improves the emulsifying property of the capsule wall material, wraps the bioflocculants, and increases the storage stability of the microcapsules. The calcium carbonate introduces divalent calcium ions into the capsule wall material, forms a network structure with negatively charged molecules, causes crosslinking, and helps the molding and solidification of the capsule wall material.

[0012] The specific ratio of the modified chitosan, sodium octenyl succinate starch, and sucrose ester makes the capsule wall material have better stability and durability, thereby ensuring the stability of the bioflocculating and precipitating agent under various environmental conditions.

[0013] Optionally, the modified chitosan comprises 10-12 parts of polyethylene glycol, 1-3 parts of p-nitrochloroformic acid phenyl ester, 0.5-0.8 parts of triethylamine, and 10-12 parts of water-soluble chitosan.

[0014] By adopting the above technical solution, the triethylamine acts as a catalyst in the activated polyethylene glycol, promotes the activation reaction of the p-nitrochloroformic acid phenyl ester on the polyethylene glycol, the nitro group and chloroformic acid group on the benzene ring of the p-nitrochloroformic acid phenyl ester react with the hydroxyl group of the polyethylene glycol to form ester bonds and amide bonds, thereby activating the polyethylene glycol. The activated polyethylene glycol has higher reactivity and stability, can react with the water-soluble chitosan, and generates the modified chitosan.

[0015] Optionally, the preparation steps of the modified chitosan are as follows:

[0016] (1) Activating the polyethylene glycol: dissolve the polyethylene glycol and triethylamine in acetonitrile to obtain a mixed solution, dissolve the p-nitrochloroformic acid phenyl ester in acetonitrile and add it dropwise into the foregoing mixed solution, use an ice-salt bath to keep the temperature at 4-6℃ during the reaction, stir for 24-26h after the dropwise addition is completed, freeze the product for 12-14h after the reaction is completed, remove impurities, precipitate, and dry to obtain the activated polyethylene glycol;

[0017] (2) Take water-soluble chitosan and stir it in deionized water until it is evenly distributed, then place it in an oil bath and stir it while heating until it dissolves, then cool it to room temperature and add the activated polyethylene glycol, stir at room temperature, dialysis, and impurity removal to obtain the modified chitosan.

[0018] By using the above technical solution, the polyethylene glycol is first activated to improve the activity of the polyethylene glycol, so that it can better react with chitosan. The activated polyethylene glycol is reacted with chitosan to form modified chitosan, and polyethylene glycol segments are introduced to improve the biocompatibility and degradability of chitosan.

[0019] Optionally, the weight ratio of the biologic flocculant to the modified chitosan in the degradable capsule wall material is 1:1-2.

[0020] By using the above technical solution, the biologic flocculant and the modified chitosan in the degradable capsule wall material are mixed in a certain proportion to obtain a more stable microcapsule product, so that the microcapsule material can better wrap the biologic flocculant and improve the stability of the prepared biologic flocculant.

[0021] Optionally, the capsule core material biologic flocculant further comprises 1-2 parts of aluminum chloride.

[0022] By using the above technical solution, the biologic flocculant and aluminum chloride are combined to form a more effective flocculant combination, improve the purification efficiency of the biologic flocculant, and aluminum chloride can be used as a stabilizer for the biologic flocculant to form a stable complex, further improve the stability of the biologic flocculant, and keep it active for a long time.

[0023] Optionally, the degradable capsule wall material further comprises 2-4 parts of crown ether.

[0024] By using the above technical solution, crown ether has a special molecular structure and has a good coordination effect on metal ions. The addition of crown ether and chitosan in the capsule wall material forms a double structure, increases the molecular weight, and thus enhances the ability to adsorb metal ions, thereby improving the flocculation and precipitation effect of the biologic flocculant.

[0025] In a second aspect, the application provides a preparation method of a degradable biologic flocculant, which uses the following technical solution:

[0026] A preparation method of a degradable biologic flocculant, comprising the following preparation steps:

[0027] (1) Prepare an aqueous phase containing a capsule wall material;

[0028] (2) Disperse the biologic flocculant in the aqueous phase containing the capsule wall material by emulsification homogenization to prepare an emulsion;

[0029] (3) by low temperature vacuum spray drying, the emulsion is made into microcapsules, to obtain the degradable biological flocculation precipitator.

[0030] By adopting the technical scheme, the polysaccharide, sodium octenyl succinate starch and sucrose ester are used as the wall material, and the low-temperature vacuum spray drying is adopted, and the material is subjected to negative pressure under the low-temperature condition, so that the temperature required for drying is significantly reduced, and the microcapsules have a porous structure, the ratio of the surface area to the volume is effectively improved, and the dissolution speed of the microcapsule biological flocculation precipitator prepared by the method is further improved.

[0031] In summary, the present application has the following beneficial effects:

[0032] 1. The biological flocculation agent is wrapped by the degradable capsule wall material, so that the biological flocculation agent can be in a relatively stable environment, is not disturbed or damaged by the external environment, maintains the activity of the biological flocculation agent for a long time, and obtains the biological flocculation precipitator with good stability.

[0033] 2. In the present application, the chitosan is modified by polyethylene glycol, and the chitosan modified by the polyethylene glycol has good hydrophilicity, can be quickly dissolved in water, releases the biological flocculation agent, and ensures the release performance of the biological flocculation precipitator.

[0034] 3. The method of the present application prepares the degradable biological flocculation precipitator by the low-temperature vacuum freeze-drying method, ensures that the biological flocculation agent is completely wrapped by the capsule wall material, makes the prepared microcapsules have a porous structure, effectively improves the ratio of the surface area to the volume, and further improves the dissolution speed of the microcapsule biological flocculation precipitator prepared by the method. DETAILED DESCRIPTION

[0035] The present application is further described below in combination with examples.

[0036] The specific conditions not specified in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are conventional products that can be purchased on the market.

[0037] The biological flocculation agent is a flocculant MBFA9 produced by silicate bacillus; the polyethylene glycol is PEG-200; the water-soluble chitosan is purchased from Shaanxi Jinhanshi Biological Technology Co., Ltd., and the CAS number is 9012-76-4.

[0038] Preparation examples of raw materials and / or intermediates

[0039] Preparation Example 1

[0040] A modified chitosan, the preparation comprising the following steps:

[0041] (1) Activating polyethylene glycol: 100 g of polyethylene glycol and 8 g of triethylamine were dissolved in 100 ml of acetonitrile to obtain a mixed solution, 20 g of p-nitrochloroformic acid phenyl ester was dissolved in 20 ml of acetonitrile and added dropwise to the above mixed solution at a rate of 1 drop per second, an ice-salt bath was used to maintain the temperature at 5°C during the reaction, after the dropwise addition was completed, the ice-salt bath was removed, and the reaction was stirred for 24 h, after the reaction was completed, the product was frozen at 0°C for 12 h, the triethylamine salt was removed using a sand core funnel, the obtained filtrate was rotary evaporated to 30 ml, and then slowly dropped into 200 ml of frozen ether for precipitation, and the product was placed in a vacuum oven for drying, to obtain activated polyethylene glycol;

[0042] (2) 120 g of water-soluble chitosan was placed in 1200 ml of deionized water and stirred uniformly, then placed in an oil bath and heated and stirred to dissolve, then cooled to room temperature and added with the above activated polyethylene glycol, stirred at room temperature for 1 d, dialyzed for 2 d with deionized water as the medium, the medium was replaced every 12 h, after dialysis was completed, anhydrous ethanol was added, the solvent was rotary evaporated, and the modified chitosan was treated in a freeze dryer for 3 d.

[0043] Preparation Example 2

[0044] A modified chitosan, the preparation comprising the following steps:

[0045] (1) Activating polyethylene glycol: 120 g of polyethylene glycol and 6 g of triethylamine were dissolved in 100 ml of acetonitrile to obtain a mixed solution, 10 g of p-nitrochloroformic acid phenyl ester was dissolved in 20 ml of acetonitrile and added dropwise to the above mixed solution at a rate of 1 drop per second, an ice-salt bath was used to maintain the temperature at 4°C during the reaction, after the dropwise addition was completed, the ice-salt bath was removed, and the reaction was stirred for 25 h, after the reaction was completed, the product was frozen at 0°C for 14 h, the triethylamine salt was removed using a sand core funnel, the obtained filtrate was rotary evaporated to 30 ml, and then slowly dropped into 200 ml of frozen ether for precipitation, and the product was placed in a vacuum oven for drying, to obtain activated polyethylene glycol;

[0046] (2) 120 g of water-soluble chitosan was placed in 1200 ml of deionized water and stirred uniformly, then placed in an oil bath and heated and stirred to dissolve, then cooled to room temperature and added with the above activated polyethylene glycol, stirred at room temperature for 1 d, dialyzed for 2 d with deionized water as the medium, the medium was replaced every 12 h, after dialysis was completed, anhydrous ethanol was added, the solvent was rotary evaporated, and the modified chitosan was treated in a freeze dryer for 3 d.

[0047] Preparation Example 3

[0048] A modified chitosan, the preparation comprising the following steps:

[0049] (1) Activating polyethylene glycol: 110 g of polyethylene glycol and 5 g of triethylamine were dissolved in 100 ml of acetonitrile to obtain a mixed solution, 30 g of p-nitrochloroformic acid phenyl ester was dissolved in 20 ml of acetonitrile and added dropwise to the above mixed solution at a rate of 1 drop per second, an ice salt bath was used to maintain the temperature at 6°C during the reaction, and after the dropwise addition was completed, the ice salt bath was removed, and the reaction was stirred for 26 h. After the reaction was completed, the product was frozen at 0°C for 13 h, the triethylamine salt was removed using a sand core funnel, and the obtained filtrate was rotary evaporated to 30 ml, and then slowly dropped into 200 ml of frozen ether for precipitation. The product was placed in a vacuum oven for drying to obtain activated polyethylene glycol;

[0050] (2) 100 g of water-soluble chitosan was dissolved in 1200 ml of deionized water and stirred uniformly, then placed in an oil bath and heated and stirred to dissolve, and then cooled to room temperature and added with the above activated polyethylene glycol. Stirring at room temperature for 1 day, dialysis for 2 days with deionized water as the medium, and the medium was replaced every 12 h. After dialysis, anhydrous ethanol was added, the solvent was removed by rotary evaporation, and the modified chitosan was treated in a freeze dryer for 3 days.

[0051] Example

[0052] Example 1

[0053] A degradable biological flocculation and precipitation agent, the preparation comprising the following steps:

[0054] (1) Configuring a water phase material containing a capsule wall material: 20 g of modified chitosan, 30 g of octenyl succinate sodium starch, 10 g of sucrose ester, and 10 g of calcium carbonate were dissolved in 120 g of water and stirred to form a water phase material;

[0055] (2) Blending 20 g of a biological flocculating agent with the water phase material prepared in step (1), and stirring and mixing uniformly to obtain an emulsion; (3) Low-temperature vacuum spray drying the above emulsion, with an inlet air temperature of 40°C, an outlet air temperature of 30°C, and a vacuum degree of -0.09 MPa, to form microcapsules, thereby obtaining the degradable biological flocculation and precipitation agent; The modified chitosan used in this example is prepared in Preparation Example 1.

[0056] Example 2

[0057] A degradable biological flocculation and precipitation agent, the preparation comprising the following steps:

[0058] (1) Configuring a water phase material containing a capsule wall material: 40 g of modified chitosan, 20 g of octenyl succinate sodium starch, 7.5 g of sucrose ester, and 15 g of calcium carbonate were dissolved in 120 g of water and stirred to form a water phase material;

[0059] (2) 20g of the bioflocculant was mixed with the water phase material prepared in step (1) to obtain an emulsion; (3) the emulsion was low-temperature vacuum spray dried to form microcapsules, and the degradable bioflocculating precipitant was obtained; the modified chitosan used in this example was prepared in Preparation Example 1.

[0060] Example 3

[0061] A degradable bioflocculating precipitant, the preparation comprising the following steps:

[0062] (1) a water phase material containing a capsule wall material was prepared: 30g of modified chitosan, 10g of octenyl succinate sodium starch, 5g of sucrose ester, and 20g of calcium carbonate were dissolved in 120g of water to form a water phase material;

[0063] (2) 20g of the bioflocculant was mixed with the water phase material prepared in step (1) to obtain an emulsion; (3) the emulsion was low-temperature vacuum spray dried to form microcapsules, and the degradable bioflocculating precipitant was obtained; the modified chitosan used in this example was prepared in Preparation Example 1.

[0064] Example 4

[0065] A degradable bioflocculating precipitant, which is different from Example 1 in that the modified chitosan used in this example is prepared in Preparation Example 2.

[0066] Example 5

[0067] A degradable bioflocculating precipitant, which is different from Example 1 in that the modified chitosan used in this example is prepared in Preparation Example 3.

[0068] Example 6

[0069] A degradable bioflocculating precipitant, which is different from Example 1 in that 10g of modified chitosan is added in this example.

[0070] Example 7

[0071] A degradable bioflocculating precipitant, which is different from Example 1 in that 60g of modified chitosan is added in this example.

[0072] Example 8

[0073] A degradable bioflocculating precipitant, which is different from Example 1 in that 10g of aluminum chloride is added to the bioflocculant in this example, and the preparation steps are as follows:

[0074] A degradable bioflocculation precipitant, the preparation comprising the following steps:

[0075] (1) configuring a water phase material containing capsule wall material: 20 g of modified chitosan, 30 g of sodium octenyl succinate starch, 10 g of sucrose ester and 10 g of calcium carbonate were dissolved into 120 g of water to form a water phase material by stirring and mixing;

[0076] (2) 12 g of bioflocculant and 10 g of aluminum chloride were added to 30 g of deionized water and stirred uniformly, and then pre-mixed, and then blended with the water phase material prepared in step (1), and stirred and mixed uniformly to obtain an emulsion;

[0077] (3) The above emulsion was low-temperature vacuum spray dried, with an inlet air temperature of 40°C, an outlet air temperature of 30°C, and a vacuum degree of -0.09 MPa, to form microcapsules, thereby obtaining the degradable bioflocculation precipitant; the modified chitosan used in this example was prepared in Preparation Example 1.

[0078] Example 9

[0079] A degradable bioflocculation precipitant, which is different from Example 1 in that 20 g of crown ether is added to the capsule wall material in this example, and the preparation steps are as follows:

[0080] (1) configuring a water phase material containing capsule wall material: 20 g of modified chitosan, 30 g of sodium octenyl succinate starch, 10 g of sucrose ester, 10 g of calcium carbonate and 20 g of crown ether were dissolved into 120 g of water to form a water phase material by stirring and mixing;

[0081] (2) 12 g of bioflocculant and 10 g of aluminum chloride were added to 30 g of deionized water and stirred uniformly, and then pre-mixed, and then blended with the water phase material prepared in step (1), and stirred and mixed uniformly to obtain an emulsion;

[0082] Comparative Example

[0083] Comparative Example 1

[0084] A degradable bioflocculation precipitant, which is different from Example 1 in that the chitosan used in the capsule wall material in this comparative example is not modified.

[0085] Comparative Example 2

[0086] A degradable bioflocculation precipitant, which is different from Example 1 in that sodium octenyl succinate starch is not added to the capsule wall material in this comparative example.

[0087] Comparative Example 3

[0088] A degradable bioflocculation precipitant is a flocculant MBFA9 produced by silicate bacillus.

[0089] Performance detection test

[0090] Detection method / test method

[0091] Heavy metal wastewater flocculation experiment: standard solution of lead ions and copper ions is configured, a mother liquor containing copper ions and lead ions with a mass concentration of 5 g / L is prepared, the pH is adjusted to 7 for standby; the above prepared mother liquor is diluted with distilled water to a mass concentration of 100 mg / L, then 40 g of the prepared bioflocculation precipitant is added, stirred and dissolved at room temperature, and fully reacted for 2 h, centrifuged using a centrifuge, the supernatant is collected, and the mass concentration of heavy metal ions in the supernatant is tested by inductively coupled plasma emission spectroscopy, and the removal rate of metal ions is calculated;

[0092] Storage stability detection: after the prepared bioflocculation precipitant is stored at room temperature for one month, the above experiment is performed, and the removal rate of metal ions at this time is recorded.

[0093] Table 1 test detection results

[0094]

[0095]

[0096] In combination with Examples 1-3 and Comparative Example 1 and in combination with Table 1, it can be seen that the test data of Examples 1-3 are all better than those of Comparative Example 1, indicating that the modified chitosan can improve the stability of the bioflocculation precipitant, improve the dissolution speed of the capsule wall material in water, and improve the flocculation and precipitation effect of the bioflocculation precipitant.

[0097] In combination with Examples 1-3 and Comparative Example 2 and in combination with Table 1, it can be seen that the test data of Examples 1-3 are all better than those of Comparative Example 2, indicating that the sodium octenyl succinate starch can be combined with the capsule wall material to form a more stable capsule wall structure, thereby helping to improve the stability of the bioflocculation precipitant.

[0098] In combination with Examples 1-3 and Comparative Example 3 and in combination with Table 1, it can be seen that the test data of Examples 1-3 are all better than those of Comparative Example 3, indicating that the bioflocculation precipitant not subjected to microcapsule treatment is easily deactivated by the environment, resulting in poor treatment effect, and the bioflocculation precipitant prepared by the present application well maintains the activity of the bioflocculation precipitant.

[0099] In combination with Examples 1-5 and in combination with Table 1, it can be seen that the bioflocculation precipitant prepared by using the formulation ratio provided by the present application has good ability to remove heavy metal ions in wastewater.

[0100] As can be seen from the combination of Example 1 and Example 6-7 and Table 1, when the ratio of the amount of bioflocculant added to the amount of modified chitosan added in the capsule wall material is 1:0.5, the bioflocculant is excessive, resulting in that the capsule wall material cannot be completely wrapped with the bioflocculant, resulting in that the stability of the prepared bioflocculating precipitator is poor. The bioflocculating precipitator has good flocculating and precipitating ability in time, but when it is detected after being stored for one month, its metal ion binding performance is greatly reduced, and its stability is greatly affected. When the amount added is small, the amount of capsule wall material is large, and the treatment capacity of the bioflocculating precipitator for sewage is slightly reduced, and the possible reason is that the flocculating and precipitating time of the experimental sample is short. After being stored for one month, the treatment capacity is basically not affected.

[0101] As can be seen from the combination of Example 1 and Example 8 and Table 1, the test data of Example 8 is better than that of Example 1, which shows that the addition of aluminum chloride in the bioflocculant can be combined with the bioflocculant to form a more effective flocculant combination, enhance the purification efficiency of the bioflocculating precipitator, and improve the stability, so that it can maintain good activity for a long time. After being placed for one month, its flocculating and precipitating ability is almost unchanged.

[0102] As can be seen from the combination of Example 1 and Example 9 and Table 1, the test data of Example 9 is better than that of Example 1, which shows that the addition of crown ether in the capsule wall material further improves the ability of the bioflocculating precipitator to adsorb metal ions, and improves the flocculating and precipitating ability of the bioflocculating precipitator.

[0103] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A degradable bio-flocculating coagulant, characterized in that, The biologic flocculants in the capsule core material include degradable capsule wall material and the capsule core biologic flocculants wrapped in the capsule wall material, wherein the degradable capsule wall material includes modified chitosan, sodium octenyl succinate starch, sucrose ester and calcium carbonate, and the modified chitosan is prepared by modifying chitosan with polyethylene glycol; The degradable capsule wall material includes 2-5 parts of modified chitosan, 1-3 parts of sodium octenyl succinate starch, 0.5-1 part of sucrose ester, 1-2 parts of calcium carbonate and 2-4 parts of crown ether; The modified chitosan includes 10-12 parts of polyethylene glycol, 1-3 parts of p-nitrochloroformic acid phenyl ester, 0.5-0.8 parts of triethylamine and 10-12 parts of water-soluble chitosan; and the ratio of the biologic flocculants to the weight parts of the modified chitosan in the degradable capsule wall material is 1:1-2.

2. The biodegradable bio-flocculating precipitant according to claim 1, characterized in that: The preparation steps of the modified chitosan are as follows: (1) activating polyethylene glycol: dissolving polyethylene glycol and triethylamine in acetonitrile to obtain a mixed solution, dissolving p-nitrochloroformic acid phenyl ester in acetonitrile and adding it dropwise into the mixed solution, using an ice-salt bath to keep the temperature at 4-6℃ during the reaction, stirring for 24-26 hours after the dropwise addition is completed, freezing the product for 12-14 hours after the reaction is completed, removing impurities, sedimentation and drying to obtain the activated polyethylene glycol; (2) stirring the water-soluble chitosan in deionized water until it is uniformly dissolved, heating and stirring in an oil bath to dissolve, then adding the activated polyethylene glycol at room temperature, stirring at room temperature, dialysis and impurity removal to obtain the modified chitosan.

3. The biodegradable bio-flocculating precipitant according to claim 1, characterized in that: The biologic flocculants in the capsule core material also include 1-2 parts of aluminum chloride.

4. A process for the preparation of a biodegradable bioflocculantsedimentation agent as claimed in any one of claims 1 to 3, characterized in that, The preparation steps are as follows: (1) preparing an aqueous phase containing capsule wall material; (2) dispersing the biologic flocculants in the aqueous phase containing the capsule wall material to form an emulsion; (3) forming microcapsules by low-temperature vacuum spray drying the emulsion to obtain the degradable biologic flocculating precipitator.

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