Preparation of starch-based polysaccharide flocculants for manure water purification and method for enhancing composting efficiency

Abstract

The present application relates to a kind of preparation of starch-based polysaccharide flocculants for fecal water purification and the method for enhancing compost efficiency, with starch as matrix, in alkaline aqueous phase make betaine type epoxy monomer and cationic epoxy monomer synchronous ring-opening etherification to obtain co-modified starch;The co-modified starch and [Fe (III)-TA] MPN carry out organic-inorganic synergistic effect, form hybrid flocculation network, and the mass ratio of the two is 1:1~1:15. Wherein, [Fe (III)-TA] MPN is formed by polymeric ferric salt and metal coordination coupling of tannic acid Form a polyphenol network structure.The flocculant described in the present application has the effect of quick flocculation, salt resistance, organic interference resistance on cow fecal water under the same or lower dosage, while playing the role of maturation on the flocculation precipitate in the composting process, overall with good economy and sustainability.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection, specifically relating to a flocculant technology, and in particular to a method for preparing a starch-based polysaccharide flocculant for purifying livestock and poultry farm manure and for increasing composting efficiency using the flocculant. Background Technology

[0002] Livestock and poultry manure contains a large amount of water, which is one of its main components; it also contains organic matter, including undigested food residue, cellulose, protein, and fat. This organic matter constitutes a significant proportion of livestock and poultry manure and is crucial for its treatment and resource utilization; it also contains inorganic matter, mainly inorganic salts ingested by livestock and poultry, such as calcium, phosphorus, and potassium. While these inorganic substances play a role in plant growth, excessive discharge can pollute the environment; and it also contains pathogenic microorganisms, such as bacteria and viruses, which may pose a threat to human and animal health if not properly treated. After a certain period of storage, under the action of microorganisms, livestock and poultry manure will form pollutants such as ammonia nitrogen, phosphorus, chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP), especially complex colloids (VOCs) composed of a large number of negatively charged volatile organic compounds formed after the decomposition of organic matter. Under the influence of these substances, the manure is difficult to separate by conventional solid-liquid separators, sedimentation tanks, and other methods for separating organic matter in water bodies, and its stability is very high, becoming a key factor causing environmental pressure in the livestock and poultry farming industry. How to quickly separate the large amount of high-concentration organic matter containing stable VOCs in livestock and poultry manure and dispose of the manure in a timely manner is a major technical bottleneck facing this industry. Taking Ningxia as an example, the amount of dairy farm manure produced and requiring treatment and disposal each year is as high as 31.671 million tons, equivalent to the total water volume of 2.2 West Lakes, resulting in enormous environmental pressure. The method disclosed in this invention is precisely the key to solving this industry problem. Through the search of relevant documents, the following comparative analysis was conducted:

[0003] Patent document CN06495304B discloses a formulation and its preparation process, particularly relating to a flocculant formulation and its preparation process for treating aquaculture wastewater. The technical problem this invention aims to solve is to provide a flocculant formulation and its preparation process for treating aquaculture wastewater that is environmentally friendly, effective, and requires only a small dosage.

[0004] Patent document CN111348773B discloses a method for flocculation and dual-filtration dephosphorization and denitrification of polluted seawater, including a method for preparing a flocculant. S3, Preparation of flocculant: Prepare 5-1000 parts of polyaluminum sulfate, 10-3000 parts of polyferric chloride, 5-1000 parts of polysilicic acid, 1000-5000 parts of distilled water, chitosan and its modified derivatives, wherein 5-20 parts of chitosan, 50-500 parts of carboxymethyl chitosan quaternary ammonium salt, hydroxypropyl chitosan quaternary ammonium salt, and 100-2000 parts of oyster shell powder. First, react polyaluminum sulfate with polyferric chloride to generate aluminum ferric sulfate. Then, mix the aluminum ferric sulfate into the polysilicic acid and add distilled water to prepare a polysilicic acid aluminum ferric sulfate solution. Then, mix the polysilicic acid aluminum ferric sulfate solution with chitosan and its modified derivatives to obtain the seawater flocculant. The inorganic mixed components are structurally unstable and easily dispersed.

[0005] Patent document CN106335988A discloses a composite polymeric flocculant for coking wastewater and its preparation method: using nonionic, anionic, cationic, and amphoteric polyacrylamide as the modified base, it is grafted or crosslinked with phenolic resin, acrylamide derivatives, etc., under initiator and acidic conditions, and then compounded with inorganic flocculants to form a composite system for reducing COD and suspended solids. Its core is a PAM petrochemical framework + inorganic mixture, without involving starch-based cationic or amphoteric "simultaneous etherification" co-modification, and the inorganic multi-component compound is prone to structural instability, aging, and dispersion problems.

[0006] Patent document CN110194806A discloses a method for preparing cationic starch: GTA is added to a 5.0 g / L NaOH solution and stirred for 15–25 min, then corn starch is added. The mixture is then heated in a water bath at 64–68 °C for 35–45 min, cooled to room temperature, neutralized, and microwaved for 2–4 min, repeated 6 times. The resulting product is washed 4–6 times with anhydrous ethanol, vacuum dried at 55–65 °C for 7–9 h, and passed through a 75 μm sieve. This method is simple and easy to scale up, but it belongs to a single quaternization route, does not introduce betaine-type amphipathic sites, and does not involve complexation with [Fe(Ⅲ)-TA]MPN.

[0007] Even after filtration, livestock and poultry manure still contains the aforementioned inorganic mixture, which is structurally unstable and easily dispersed. How to achieve effective flocculation and harmless treatment under these conditions has become a technical challenge for farmers. This invention addresses this problem by proposing a highly efficient flocculation solution for the preliminary filtrate of livestock and poultry manure. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a starch-based polysaccharide flocculant that is simple to prepare, has good flocculation properties for suspended solids, and can effectively remove substances such as chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) from sewage. This flocculant not only achieves the aforementioned multiple benefits but also increases composting efficiency.

[0009] The technical problem solved by this invention is achieved through the following technical solution:

[0010] A method for preparing a starch-based polysaccharide flocculant for sewage purification includes the following steps:

[0011] ① This includes the preparation of co-modified starch, in which modified starch and betaine-type amphoteric epoxy monomers undergo ring-opening etherification with starch simultaneously under alkaline conditions to obtain co-modified starch;

[0012] ② Includes the step of forming a flocculant, which involves complexing co-modified starch with polymerized ferric salt to form a flocculant.

[0013] Furthermore, in step ②, a tannic acid-containing solution is added to form a flocculant, and the flocculant is formed after the addition.

[0014] Furthermore, the weight ratio of the co-modified starch to the polymerized ferric salt is 1:1 to 15.

[0015] Furthermore, the method for preparing the betaine-type amphoteric epoxy monomer is as follows:

[0016] E1 collects the dried molasses residue produced during the sugar-making process of sugar beets and crushes it into molasses powder;

[0017] E2 is prepared by mixing molasses powder with an ethanol aqueous solution of 30-70% by volume at a solid-liquid mass ratio of 1:8 to 1:15, placing the mixture in a reactor equipped with a reflux device, and extracting by reflux at 60-85°C for 1-4 hours.

[0018] After E3 extraction, filter or centrifuge while hot and collect the supernatant solution.

[0019] E4 was used to adjust the betaine concentration in the supernatant to 30–100 g / L. The pH was adjusted to 8–11 with stirring, and epichlorohydrin was added. The molar ratio of epichlorohydrin to betaine was 1–3:1. The reaction was carried out at 40–70 °C for 2–6 h to obtain a betaine-type amphoteric epoxy monomer.

[0020] The steps for preparing the co-modified starch are as follows:

[0021] A1 Weigh corn starch, dissolve it in an ethanol aqueous solution, and stir at 80-100℃ to gelatinize it;

[0022] A2 is added to the gelatinization system by adding 2,3-epoxypropyltrimethylammonium chloride and betaine-type amphoteric epoxy monomers in an isochronous dripping or pre-mixed one-time feeding manner;

[0023] Add A3 to the above dispersion system slowly with NaOH aqueous solution, adjust the pH to 10-11, stir the reaction at 50-60℃ for 2-7 hours, and consider the reaction to be complete when a stable and transparent paste is formed.

[0024] After the A4 reaction is complete, excess anhydrous ethanol is added to the dispersion system to precipitate the product.

[0025] A5 uses a vacuum filter to filter the precipitated product under reduced pressure, dries the filter residue, and then pulverizes the product after it is completely dry to obtain co-modified starch.

[0026] In the preparation of the co-modified starch, the molar ratio of corn starch, 2,3-epoxypropyltrimethylammonium chloride, and betaine-type amphoteric epoxy monomer is 1–2:1–1.5:0.1–0.8.

[0027] The preparation steps of a starch-based polysaccharide flocculant for sewage purification are as follows:

[0028] B1. Disperse the modified starch in water and gelatinize at 80-95℃ for 30 min;

[0029] B2 was added to a tannic acid extract with a final concentration of 10–150 g / L and a polymerized ferric salt with a final concentration of 10–150 g / L under pH conditions of 5.5–6.8, and stirred for 5–10 min to form an ferric salt complex.

[0030] Add B3 dropwise to the co-modified starch dispersion and continue stirring for 10–30 min;

[0031] Add 0.1–1.0 g / L potassium persulfate to B4 and continue the gelatinization reaction at 45–55°C for 2–3 hours.

[0032] After the B5 reaction is complete, excess anhydrous ethanol is added to the dispersion system to precipitate the product.

[0033] B6 uses a vacuum filter to filter the precipitated product under reduced pressure, and then pulverizes the filter residue to obtain a flocculant.

[0034] The weight ratio of the co-modified starch to the polymerized ferric salt is 1:1 to 15.

[0035] A method for purifying manure involves adding a starch-based polysaccharide flocculant, diluting it with water to form an orange-red, non-adherent aqueous flocculent solution, adding it to cow manure water at a ratio controlled at 7‰ to 10‰, stirring evenly at a speed of 200 to 500 r / min, allowing it to stand for 1 to 5 hours to generate flocculated precipitate, and then separating the flocculated precipitate.

[0036] A composting method for promoting flocculation and sedimentation, comprising the following steps:

[0037] C1. The separated flocculated precipitate is mixed with animal manure and straw on a dry basis, wherein the flocculated precipitate accounts for 10% to 30% of the dry basis mass of the mixture;

[0038] C2. Adjust the C / N ratio of the mixture to 25:1~30:1 and the moisture content to 55~65%;

[0039] C3. Add compound microbial preparation at 0.5 wt% on a wet basis, mix it evenly with the flocs first, and then mix it with the flocs and straw; the porosity of the mixture should be ≥35%, and the pH should be 6.5~8.0, and carry out staged composting fermentation;

[0040] C4. Carry out composting fermentation under aerobic conditions, keeping the pile temperature at 60~70℃ for a cumulative period of ≥3 days, until the pile temperature drops to ambient temperature, to obtain the finished compost product.

[0041] The flocculation and sedimentation method for promoting maturation involves the following stages of composting fermentation:

[0042] D1 pretreatment involves mixing livestock and poultry manure with straw and crushing it to a particle size ≤30 mm; adding flocculation sedimentation at a dry basis of 10-30%, adjusting the C / N ratio of the mixture to 25-30:1 and the moisture content to 55-65%; first, uniformly mixing the compound microbial preparation with the flocs at a wet basis of 0.5%, using the flocs as a carrier for the bacteria; then mixing it with the flocculation sedimentation and straw; the porosity of the mixture should be ≥35%, and the pH should be 6.5-8.0.

[0043] D2 primary fermentation involves aerobic fermentation methods such as windmill, trough, membrane fermentation, or reactor fermentation for composting. If windmill, trough, or membrane fermentation is used, the pile height should be controlled between 0.8 and 1.5 meters, and the pile width between 1.5 and 2.5 meters. If forced aeration is used to oxygenate the pile, the ventilation intensity should be no less than 0.1 meters. 3 ·min -1· m -3 (Based on pile volume) To maintain dissolved oxygen levels in the pile at no less than 10%, if using windrow or trough stacking, the pile temperature should be monitored until it reaches 50–60°C, at which point it should be turned over once. Once the pile temperature reaches 60–70°C and is maintained for 3–7 days, it should be allowed to cool naturally to complete the composting process. If using a reactor-type aerobic fermentation, the high temperature should be monitored until it reaches 60–70°C and is maintained for at least 3 days, at which point it should cool naturally to complete the composting process. If the reactor temperature is maintained at 60–70°C for less than 3 days, fermentation failure detection is required.

[0044] D3 secondary fermentation involves transferring the materials from the primary fermentation to the secondary fermentation site for further stacking, maintaining proper ventilation and humidity, so that the organic matter that was not fully decomposed in the primary fermentation continues to degrade and humify until the stack temperature stabilizes within 10°C above the ambient temperature.

[0045] The advantages and positive effects of this invention are:

[0046] 1. The flocculant provided by this invention is a starch-based polysaccharide flocculant constructed from co-modified starch and [Fe(Ⅲ)-TA]MPN through coordination complexation and chain bridging. Under the same or lower dosage conditions, this flocculant shows significantly better treatment effects in terms of turbidity, suspended solids, and organic matter removal than traditional single-component inorganic salt flocculants or non-synergistic organic polymer systems. It has high reagent utilization efficiency and overall good economic efficiency and engineering applicability.

[0047] 2. The flocculant provided by this invention is an organic-inorganic multi-effect composite system synergistically constructed from co-modified starch and [Fe(Ⅲ)-TA]MPN. The co-modified starch is obtained by simultaneous ring-opening etherification of EPTAC and betaine-type epoxy monomers in an alkaline aqueous phase. Quaternary ammonium cation sites and amphoteric sites are simultaneously introduced onto the molecular chain of DF. These sites neutralize the anionic colloids in cow manure water and trigger chain bridging, rapidly reducing the zeta potential. [Fe(Ⅲ)-TA]MPN provides π-π, hydrophobic interactions and multiple coordination sites, selectively capturing pollutants. The multi-site interactions between the polynuclear hydroxyl Fe(Ⅲ) species provided by PFS and the ether oxygen, hydroxyl, and amphoteric sites on the chain make the organic-inorganic framework less prone to disintegration under conventional coagulation-flocculation stirring procedures. The construction of "[Fe(Ⅲ)-TA]MPN parallel co-modified starch" forms larger and denser flocs through charge neutralization and bridging, significantly improving the removal effect on water samples. When all formulations are used at the same or lower dosage, Example 2 has the lowest drug consumption (7‰~10‰), and the floc formation and sedimentation are more rapid, demonstrating higher drug utilization efficiency and operational economy.

[0048] 3. This invention preferably uses agricultural waste rich in tannin-type polyphenols (such as peanut skins, coffee shells, and potato peels) to obtain tannic acid extract through reflux extraction with an ethanol-water solution, which is then used to construct [Fe(Ⅲ)-TA]MPN. This achieves high-value resource utilization of agricultural and forestry waste and significantly reduces the cost of tannic acid raw materials.

[0049] 4. The precipitate generated by the flocculation reaction of the flocculant described in this invention is rich in organic matter, nitrogen, phosphorus and other nutrients, as well as a certain proportion of inorganic particles, and has good potential for resource utilization. Experiments have shown that the precipitate of this flocculant is rich in organic carbon sources, which can be used as raw materials for anaerobic digestion in biogas fermentation to achieve clean energy recovery. It can also be used as biomass fuel or biochar raw materials for pyrolysis energy conversion.

[0050] 5. The flocculent compost of this invention can provide nutrients and a favorable environment for microorganisms: the nitrogen and phosphorus nutrients retained in the flocs can compensate for the lack of nitrogen and phosphorus in the substrate in the early stage of composting, allowing microorganisms to reproduce faster and the compost to heat up faster. At the same time, the cationic starch structure can neutralize excess ammonia in the compost, reducing ammonia volatilization and irritating odor.

[0051] 6. The flocs of this invention improve the physical structure of compost: The flocs are granular structures formed by polysaccharides and iron, which can intertwine with fibers such as straw and manure, improving the aeration of the compost pile, making it easier for oxygen to enter, resulting in a more uniform temperature distribution, and reducing the likelihood of odor or localized anaerobic conditions. This reduces odor and gas emissions. The iron and cationic groups in the flocs can adsorb or bind phosphorus, ammonia, and hydrogen sulfide, reducing the release of these gases and thus lowering the ammonia and odor levels. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the flocculation effect in Embodiment 1 of the present invention.

[0053] Figure 2 This is a schematic diagram of the flocculation effect in Embodiment 2 of the present invention.

[0054] Figure 3 This is a schematic diagram of the flocculation effect in Embodiment 3 of the present invention.

[0055] Figure 4 This is a schematic diagram of the flocculation effect in Example 4 of the present invention.

[0056] Figure 5 This is a schematic diagram of the flocculation effect in Embodiment 5 of the present invention.

[0057] Figure 6 SEM image of corn starch.

[0058] Figure 7 SEM image of the material in Example 2.

[0059] Figure 8 EDS analysis of corn starch and the material in Example 2.

[0060] Figure 9 SEM of cow dung water.

[0061] Figure 10 SEM of flocculents.

[0062] Figure 11 EDS analysis of cow manure water and flocs.

[0063] Figure 12 The infrared spectrum of corn starch in Example 2.

[0064] Figure 13 Infrared spectra of cow dung water and flocs. Detailed Implementation

[0065] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0066] Example 1

[0067] A starch-based polysaccharide flocculant for sewage purification and its preparation method, comprising: co-modified starch + cationic quaternary ammonium salt starch + PolyFe 3+ (The following examples are all PFS polyferric sulfate).

[0068] Mechanism: Under alkaline conditions, the etherifying agent EPTAC and DF simultaneously undergo ring-opening etherification with betaine-type epoxy monomers to generate a co-modified product containing both quaternary ammonium cation sites and amphipathic sites within the inner salt. The quaternary ammonium groups increase the positive charge density, achieving charge neutralization and chain bridging of fecal colloids; the amphipathic inner salt groups form a strong hydration layer and provide ion pair and hydrogen bond interactions, weakening the shielding of active sites by salinity, hardness, and humic acid. Further grafting with quaternary ammonium monomers in cationic quaternary ammonium starch enhances the cationic charge; Fe in PFS... 3+ Ions further participate in coordination, forming a multinucleated complex network, which promotes floc formation through charge neutralization and adsorption bridging.

[0069] Preparation steps:

[0070] I. The preparation method of betaine-type amphoteric epoxy monomers is as follows:

[0071] E1. Select agricultural waste rich in betaine alkaloids, remove mud and other impurities, dry it at 50-70℃ to constant weight, crush it and pass it through a 40-80 mesh sieve to obtain raw material powder; the agricultural waste is molasses residue produced during the sugar beet production process.

[0072] E2. Take the above raw material powder at a solid-liquid mass ratio of 1:8 to 1:15 and mix it with an ethanol aqueous solution with a volume fraction of 30 to 70%. Place the mixture in a reactor equipped with a reflux device and reflux extract at 60 to 85°C for 1 to 4 hours.

[0073] E3. After extraction, filter or centrifuge while hot and collect the supernatant; the reflux extraction can be repeated 1 to 2 times as needed, and the filtrates from each extraction should be combined.

[0074] E4. Concentrate the combined filtrate under reduced pressure to the desired volume, so that the betaine concentration in the solution is 30-100 g / L. Adjust the pH to 8-11 with stirring, and add epichlorohydrin at a molar ratio of 1-3:1. React at 40-70℃ for 2-6 h to allow the carboxyl group in the betaine molecule to undergo addition with epichlorohydrin and then undergo a dehydrochlorination ring-closure reaction to generate a betaine-type amphoteric epoxy monomer with an epoxy group. The resulting reaction solution containing the betaine-type amphoteric epoxy monomer is used for the subsequent preparation of co-modified starch.

[0075] II. Preparation of Co-modified Starch

[0076] A1. Weigh corn starch, dissolve it in an ethanol aqueous solution, and stir at 80-100℃ for 0.5 h to gelatinize it.

[0077] A2. Add EPTAC (2,3-epoxypropyltrimethylammonium chloride) and betaine-type amphoteric epoxy monomer to the gelatinization system by adding them dropwise at equal intervals or by pre-mixing and adding them in one batch.

[0078] A3. Slowly add NaOH aqueous solution to the above dispersion system, adjust pH to 10-11, stir the reaction at 50-60℃ for 2-7 hours, and consider the reaction to be complete when a stable and transparent paste is formed.

[0079] A4. After the reaction is complete, add excess anhydrous ethanol to the dispersion system to precipitate the product.

[0080] A5. After precipitation, filter the product under reduced pressure using a vacuum filter, dry the filter residue, and grind the product into powder using a mortar and pestle after it is completely dry.

[0081] III. Compound reaction

[0082] F1. Weigh 10 g of co-modified starch and dissolve it in water, then gelatinize it at 60℃.

[0083] F2. Add 50-60 g / L of cationic quaternary ammonium salt starch aqueous solution and 1-5 g / L of PFS aqueous solution dropwise to the gelatinization solution.

[0084] Using a 0.05–0.25 g / L potassium persulfate aqueous solution (KPS) as an initiator, the reaction was continued at 60°C for 3–5 h.

[0085] F4. After the reaction is complete, add excess anhydrous ethanol to the dispersion system to precipitate the product.

[0086] F5. The precipitated product is filtered under reduced pressure using a vacuum filter. The filter residue is dried by blowing air at 60°C for 24 hours. After the product is completely dried, it is ground into powder using a mortar and pestle.

[0087] Flocculation effect experiment: A flocculation experiment was conducted by adding fecal water, the amount added being as follows... Figure 1-5 All figures shown are weight percentages (the same treatment applies to the following examples).

[0088] Example 2

[0089] A starch-based polysaccharide flocculant for sewage purification and its preparation method, the composition of which is: co-modified starch + [Fe(Ⅲ)-TA]MPN.

[0090] Mechanism: Under alkaline conditions, the etherifying agent EPTAC and starch undergo simultaneous ring-opening etherification with a betaine-type epoxy monomer, generating a co-modified product containing both quaternary ammonium cation sites and amphiphilic sites within the inner salt. The quaternary ammonium groups increase the positive charge density, achieving charge neutralization and chain bridging of the fecal colloids; the amphiphilic inner salt groups form a strong hydration layer and provide ion pair and hydrogen bond interactions, weakening the shielding effect of salinity, hardness, and humic acid on the active sites. PFS hydrolysis generates polynuclear hydroxyl-coordinated Fe(III) species, which coordinate with the polyphenolic hydroxyl groups of tannic acid to form [Fe(III)-TA]MPN. This mechanism is also applicable to pure tannic acid and tannic acid extracts obtained from agricultural waste rich in tannin-type polyphenols through ethanol reflux extraction. Subsequently, the quaternary ammonium cation sites of the co-modified starch undergo electrostatic adsorption and multi-point bridging with [Fe(Ⅲ)-TA]MPN. The hydroxyl groups, ether oxygens, and amphoteric internal salt sites on the chain further "parallel" the MPN particles into an organic-inorganic hybrid framework through hydrogen bonding and partial coordination.

[0091] Experimental steps:

[0092] I. Preparation of co-modified starch (same as Example 1)

[0093] II. Preparation of Tannic Acid Extract from Agricultural Waste

[0094] G1. Select agricultural waste rich in tannin polyphenols, remove mud and other impurities, dry it at 60-80℃ to constant weight, crush it and pass it through a 40-80 mesh sieve to obtain raw material powder; the agricultural waste is at least one of peanut skin produced during peanut processing, coffee shell produced during coffee processing, or potato peel produced during potato deep processing.

[0095] G2. Take the above raw material powder at a solid-liquid mass ratio of 1:5 to 1:20 and mix it with an ethanol aqueous solution with a volume fraction of 50 to 80%. Place the mixture in a reactor equipped with a reflux device and reflux extract at 70 to 85°C for 1 to 3 hours.

[0096] G3. After extraction, filter or centrifuge while hot and collect the supernatant; the reflux extraction can be repeated 1 to 2 times as needed, and the filtrates from each extraction can be combined.

[0097] G4. Concentrate the combined filtrate under reduced pressure to the desired volume, so that the total polyphenol mass concentration is 10-150 g / L, and add water as necessary to adjust the ethanol volume fraction to obtain the tannic acid-containing extract for step B2.

[0098] III. Compound reaction

[0099] B1. Weigh 10g of co-modified starch and disperse it in water, then gelatinize at 80-95℃ for 30 min.

[0100] B2. Under pH conditions of 5.5 to 6.8, the tannic acid extract obtained in step G (final concentration 10 to 150 g / L) is mixed with 10 to 150 g / L PFS solution and stirred for 5 to 10 min.

[0101] B3. Add dropwise to the co-modified starch dispersion and continue stirring for 10–30 min.

[0102] B4. Add 0.1–1.0 g / L potassium persulfate and continue the gelatinization reaction at 45–55°C for 2–3 hours.

[0103] B5. After the reaction is complete, add excess anhydrous ethanol to the dispersion system to precipitate the product.

[0104] B6. The precipitated product is filtered under reduced pressure using a vacuum filter, and the filter residue is dried and pulverized to obtain a flocculant.

[0105] Example 3

[0106] A starch-based polysaccharide flocculant for sewage purification and its preparation method, comprising: cationic etherified starch + PolyFe 3+ .

[0107] Mechanism: Cationic etherified starch contains a high density of quaternary ammonium groups, and its long-chain molecular structure provides excellent adsorption bridging ability. The quaternary ammonium cations in cationic etherified starch react with PolyFe... 3+ The sulfate and hydroxyl groups in the polyFe2+ undergo electrostatic association to form a preliminary organic-inorganic complex system. Simultaneously, PolyFe2+... 3+ Fe in 3+ The ions coordinate with the hydroxyl or ether oxygen (–O–) groups on the starch molecular chain to form F–O coordination bonds. This demonstrates the advantages of the "direct etherification-coordination" system in terms of reaction simplification and flocculation efficiency.

[0108] Experimental steps:

[0109] H1. Weigh 10 g of cationic etherified starch and dissolve it in water, then gelatinize it at 60℃.

[0110] H2. Add a 20-30 g / L PFS aqueous solution dropwise to the gelatinized solution.

[0111] H3. Use 0.05-0.25 g / L potassium persulfate aqueous solution (KPS) as an initiator and continue the reaction at 60℃ for 3-5 h.

[0112] H4. After the reaction is complete, excess anhydrous ethanol is added to the dispersion system to precipitate the product.

[0113] H5. The precipitated product was filtered under reduced pressure using a vacuum filter. The filter residue was dried by blowing air at 60°C for 24 hours. After the product was completely dried, it was ground into powder using a mortar and pestle.

[0114] Example 4

[0115] A starch-based polysaccharide flocculant for sewage purification and its preparation method, comprising: cationic quaternary ammonium salt starch + PolyFe 3+ .

[0116] Mechanism: Cationic quaternary ammonium starch contains a high density of quaternary ammonium groups, and its long-chain molecular structure provides excellent adsorption bridging ability. The quaternary ammonium cations in cationic quaternary ammonium starch electrostatically associate with the sulfate and hydroxyl groups in PFS, forming a preliminary organic-inorganic complex system. This demonstrates the advantages of the "direct cationization-coordination" system in terms of reaction simplification and flocculation efficiency.

[0117] Experimental steps:

[0118] I1. Weigh 10g of cationic quaternary ammonium salt starch, dissolve it in water, and gelatinize it at 60℃.

[0119] I2. Add a 20-30 g / L PFS aqueous solution dropwise to the gelatinized solution.

[0120] I3. Use 0.05-0.25 g / L potassium persulfate aqueous solution (KPS) as an initiator and continue the reaction at 60℃ for 3-5 h.

[0121] I4. After the reaction is complete, add excess anhydrous ethanol to the dispersion system to precipitate the product.

[0122] H5. The precipitated product was filtered under reduced pressure using a vacuum filter. The filter residue was dried by blowing air at 60°C for 24 hours. After the product was completely dried, it was ground into powder using a mortar and pestle.

[0123] Example 5

[0124] A starch-based polysaccharide flocculant for sewage purification and its preparation method, comprising: corn starch + cationic quaternary ammonium salt starch + PolyFe 3+ .

[0125] Mechanism: The quaternary ammonium salt monomers in cationic quaternary ammonium salt starch undergo a direct grafting reaction with starch molecules, thereby introducing a high density of quaternary ammonium cationic groups onto the starch backbone. This direct grafting process significantly enhances the surface charge density and adsorption activity of starch molecules. The quaternary ammonium cations on the modified starch electrostatically associate with the sulfate and hydroxyl groups in PFS, forming a preliminary organic-inorganic complex system. This system embodies a synergistic mechanism of "direct grafting-coordination".

[0126] Experimental steps:

[0127] J1. Weigh 10 g of corn starch and add it to a 50% ethanol aqueous solution. Stir at 80°C for 0.5 h to gelatinize it.

[0128] J2.50~60 g / L PFS aqueous solution and 10~20 g / L cationic quaternary ammonium salt starch solution are added dropwise to the gelatinization solution.

[0129] J3. Use 0.05-0.25 g / L potassium persulfate aqueous solution (KPS) as an initiator and continue the reaction at 60℃ for 3-5 h.

[0130] J4. After the reaction is complete, add excess anhydrous ethanol to the dispersion system to precipitate the product.

[0131] J5. The precipitated product was filtered under reduced pressure using a vacuum filter. The filter residue was dried by blowing air at 60°C for 24 hours. After the product was completely dried, it was ground into powder using a mortar and pestle.

[0132] Table 1 Physicochemical properties of the supernatant after flocculation

[0133]

[0134] Table 2. Dosage of Flocculant

[0135]

[0136] ① In Example 1, the dosage was the highest (100‰~110‰) among the five experimental groups. At different dosages, below the optimal value, the flocs were loose and the supernatant was turbid. Compared with other formulations, this combination requires a higher dosage to achieve the desired effect, resulting in greater resource consumption.

[0137] ② In Example 2, the dosage was the lowest among the five groups of experiments (7‰~10‰). At dosages higher than the optimal level, the floc volume increased slightly, but the supernatant transparency did not improve further, and the sedimentation effect tended to stabilize. Compared with other experiments, this combination achieved excellent flocculation results with extremely low dosages, demonstrating high dosage efficiency and economy.

[0138] ③ Example 3 falls within the low dosage range of the five experimental groups. The experiment showed that as the dosage increased further, the color and clarity of the supernatant did not change significantly. Compared to Example 2, a slightly higher dosage (14‰~16‰) was required to achieve similar supernatant clarity, but it exhibited higher dosage efficiency and clarity advantages compared to Examples 4 and 5.

[0139] ④ Example 4 was at a moderately high level (34‰~36‰) in the five groups of experiments. Above the optimal dosage, the change in floc volume was not significant, the color of the supernatant did not improve significantly, and the flocculation effect tended to stabilize. Compared with Example 3, the dosage of Example 4 was more than twice as high, but the improvement in supernatant transparency was limited. This formula was slightly inferior in dosage efficiency and consumed relatively more resources.

[0140] ⑤ The dosage in Example 5 was moderately high (38‰~40‰) among the five groups, slightly higher than that in Example 4. Above the optimal dosage, the change in floc volume was not significant, the color of the supernatant did not improve significantly, and the flocculation effect tended to stabilize. Compared with Examples 2 and 3, this formula was slightly less efficient in dosage and consumed relatively more resources.

[0141] The original corn starch granules exhibit a regular polyhedral or ellipsoidal shape, with a relatively smooth and intact surface. The granules exist in a dispersed state and lack significant structural features, only displaying typical microstructural characteristics of biomass polysaccharides. Figure 6 (As can be seen). In contrast, the SEM image of the co-modified starch-[Fe(Ⅲ)-TA]MPN (Example 2) shows that its surface has changed from smooth to rough with film-like and granular deposits, while depressions and irregular lamellae appear, and there are obvious signs of "bridging" and "gelling" between particles. Figure 7 (As can be seen). This morphological transformation, combined with infrared spectroscopy, indicates that the starch skeleton underwent quaternization and etherification modification and was combined with [Fe(Ⅲ)-TA]MPN. It is speculated that not only were cationic groups successfully grafted onto the starch surface, but an inorganic deposition layer of iron-oxygen-sulfate ions was also formed, thereby constructing an organic-inorganic synergistic network structure, which provides abundant active sites for the subsequent formation of flocs and bridging.

[0142] Combination Figure 8 EDS analysis further confirmed this: unlike the original starch which only contained C and O, the sample in Example 2 clearly showed significant N, Fe, and S elements. The N element originated from the introduction of quaternary ammonium salt groups, indicating that the cationic groups had been successfully grafted onto the starch molecular chain. The Fe and S elements belonged to the [Fe(Ⅲ)-TA]MPN structural unit, indicating that the inorganic polynuclear iron salt had been effectively loaded into the modified starch matrix. The presence of these elements not only demonstrates the success of the modification reaction but also showcases the diversity and synergy of the material at its functional sites.

[0143] The suspended particulate structure of raw cow dung water is loose. Figure 9 , Figure 11 (Showing morphological photographs and EDS images), the surface exhibits a lamellar and irregular blocky structure with a lack of effective interparticle connections, resulting in a relatively dispersed overall composition. This structural characteristic is closely related to the presence of abundant high-molecular-weight organic matter such as proteins, polysaccharides, and humic substances in the cow manure water, giving it a rich array of hydroxyl and carboxyl groups on its surface, resulting in a strong negative charge and thus maintaining the stability of the colloidal system. Further EDS analysis results show that C and O content is the highest in the cow manure water sample, while trace amounts of Na, Mg, Ca, Fe, P, and S are also detected, indicating a complex composition, primarily composed of organic matter with small amounts of inorganic salts and metal ions.

[0144] The morphology of the flocs after the reaction was significantly different from that of the original cow dung water. Figure 10 (Showing morphological photos). The surface of the flocs changed from a flaky and loose state to a large, dense, and rough structure, suggesting that the particles are cross-linked through organic segments and coated with an inorganic framework, forming a three-dimensional network aggregate. In some areas, numerous particulate precipitates were observed adhering to the floc surface. Combined with infrared spectroscopy, this indicated that the hydroxyl iron complex in the [Fe(Ⅲ)-TA]MPN hydrolysis products underwent complexation and precipitation with the organic matter in the cow manure water, thus enhancing the stability of the flocs. EDS analysis showed that C and O content remained dominant in the flocs, but the proportion of Fe and S increased significantly, and high Ca and Na contents were detected. This indicates that during flocculation, the cationic groups in the co-modified starch-[Fe(Ⅲ)-TA]MPN and the hydroxyl iron complex of [Fe(Ⅲ)-TA]MPN coordinated and co-precipitated with the groups in the cow manure water.

[0145] Figure 12 The infrared spectra of corn starch and co-modified starch-[Fe(Ⅲ)-TA]MPN are shown, with the characteristic peak of corn starch at 3419 cm⁻¹. -1 –OH stretching vibration, 2930 cm -1 –CH2 stretching vibrations, and 1081, 992 cm⁻¹ -1 Typical C–O–C and C–O stretching absorption bands are characteristic absorptions of the starch molecular skeleton. In contrast, the broad –OH peak in the spectrum of co-modified starch-[Fe(Ⅲ)-TA]MPN shows a significant red shift to 3383 cm⁻¹. -1 Furthermore, the intensity decreased, indicating that the hydroxyl groups underwent hydrogen bond rearrangement and partial substitution during the modification and composite process; 2928 cm -1 The enhanced –CH2 peak indicates the introduction of an alkyl segment; 1022 cm⁻¹ -1The C–O–C absorption at the modified starch was significantly enhanced compared to the original starch, indicating that the etherification reaction was successful. Furthermore, the co-modified starch-[Fe(Ⅲ)-TA]MPN showed improved absorption at 1082, 599, and 503 cm⁻¹. -1 The appearance of new peaks or enhanced peak shapes in certain regions can be attributed to the stretching vibrations of S=O and S–O–Fe, as well as the characteristic absorption of the Fe–O coordination bond, demonstrating the effective binding with [Fe(III)-TA]MPN. These changes collectively indicate that the co-modified starch-[Fe(III)-TA]MPN has simultaneously completed etherification, quaternization modification, and inorganic composite processes, resulting in a significant alteration of its molecular structure and endowing the material with higher charge density and stronger coordination ability.

[0146] like Figure 13 As shown, the original cow dung water was at 3378 cm. -1 The presence of a broad and strong –OH stretching vibration peak indicates that it is rich in organic matter containing hydroxyl and carboxyl groups, such as proteins, polysaccharides, and humic substances; 2930 cm⁻¹ -1 The –CH2 characteristic peak reflects the presence of an aliphatic structure; 1000–1200 cm⁻¹ -1 The multiple absorption in the region is related to the C–O–C and polysaccharide structures. These peak characteristics indicate that the cow manure water contains a large amount of negatively charged organic colloids and dissolved organic matter, resulting in stable dispersion of its colloidal particles and making it difficult to settle naturally. In contrast, the spectrum of the flocs after the reaction shows significant differences. First, the –OH stretching peak increases from 3378 cm⁻¹. -1 Redshifted to 3343 cm -1 Furthermore, the weakening intensity indicates that the hydroxyl group participated in hydrogen bond rearrangement and the substitution of cationic groups; 2930 cm -1 The –CH2 peak is enhanced and shifted to 2925 cm⁻¹. -1 This indicates that the alkyl structure on the flocculant molecular chain was successfully introduced and interacted with the organic matter; simultaneously, 1033 cm -1 Enhanced C–O–C absorption in the vicinity demonstrates that the ether bond structure of the starch molecular chain plays a crucial role in the flocculation process of cow manure water. More importantly, the flocs show increased absorption at 872, 775, 698, and 467 cm⁻¹. -1 The appearance of new peaks or enhanced peak shapes in certain regions can be attributed to the stretching vibrations of S=O, S–O–Fe, and Fe–O, indicating that the [Fe(Ⅲ)-TA]MPN complex has formed a stable coordination complex with the organic matter in the cow manure water.

[0147] This invention also provides a practical method for composting flocculant substrates, the specific operation of which is as follows:

[0148] The flocculated sediment obtained after flocculation in Example 2 (hereinafter referred to as "flocs") was mixed with livestock and poultry manure and straw in a certain proportion, the C / N ratio was adjusted to 25, and the moisture content was 60%. Aerobic composting was carried out in accordance with NY / T 3442-2019 "Technical Specification for Composting of Livestock and Poultry Manure". The pile temperature was maintained at 60℃ for 5 days under ventilation conditions, and the high temperature period lasted for a total of 7 days.

[0149] Specific composting methods:

[0150] D1. Pretreatment: Mix livestock and poultry manure with straw and crush to a particle size ≤30 mm; add 10-30% (dry basis) of flocculated sediment (hereinafter referred to as "flocs") and adjust the C / N ratio of the mixture to 25-30:1 and the moisture content to 55-65%. Mix the compound microbial preparation (effective viable count ≥10⁹ CFU / g, containing thermophilic cellulose and lignin-decomposing bacteria) at 0.5% (wet basis) evenly with the flocs to make the flocs act as a carrier; then mix it evenly with the flocs and straw; the porosity of the mixture should be ≥35%, and the pH should be 6.5-8.0. The compound microbial preparation is: effective viable count ≥10⁹ CFU / g, containing thermophilic cellulose and lignin-decomposing bacteria (Xingtai Heyang Bioengineering Co., Ltd.).

[0151] D2. Primary fermentation: This involves aerobic fermentation using methods such as windmills, troughs, membrane fermentation, or reactors. If windmills, troughs, or membrane fermentation are used, the pile height should be controlled between 0.8 and 1.5 m, and the pile width between 1.5 and 2.5 m. If forced aeration is used to oxygenate the pile, the ventilation intensity should be no less than 0.1 m. 3 ·min -1· m -3 (Based on pile volume) To maintain dissolved oxygen levels in the pile at no less than 10%, if using windrow or trough stacking, the pile temperature should be monitored until it reaches 50–60°C, at which point it should be turned over once. Once the pile temperature reaches 60–70°C and is maintained for 3–7 days, it should be allowed to cool naturally to complete the composting process. If using a reactor-type aerobic fermentation, the high temperature should be monitored until it reaches 60–70°C and is maintained for at least 3 days, at which point it should cool naturally to complete the composting process. If the reactor temperature is maintained at 60–70°C for less than 3 days, fermentation failure detection is required.

[0152] D3. Secondary fermentation: The material from the primary fermentation is transferred to the secondary fermentation site for further stacking. Appropriate ventilation and moisture retention are maintained to allow the organic matter that was not fully decomposed in the primary fermentation to continue to degrade and humify until the stack temperature stabilizes within 10°C above the ambient temperature.

[0153] D4. Post-processing: Mature materials are screened to obtain the finished compost. Optimal product indicators: Seed germination index (GI) ≥ 90%, organic matter ≥ 45% (dry basis).

[0154] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.

Claims

1. A process for the preparation of starch based polysaccharide flocculants for purification of manure water characterized by: Includes the following steps ① This includes the preparation of co-modified starch, in which modified starch and betaine-type amphoteric epoxy monomers undergo ring-opening etherification with starch simultaneously under alkaline conditions to obtain co-modified starch; ② This includes the step of forming a flocculant, which involves complexing co-modified starch with polymerized ferric salt to form a flocculant; The method for preparing the betaine-type amphoteric epoxy monomer is as follows: E1 collects the dried molasses residue produced during the sugar-making process of sugar beets and crushes it into molasses powder; E2 is prepared by mixing molasses powder with an ethanol aqueous solution of 30-70% by volume at a solid-liquid mass ratio of 1:8 to 1:15, placing the mixture in a reactor equipped with a reflux device, and extracting by reflux at 60-85°C for 1-4 hours. After E3 extraction, filter or centrifuge while hot and collect the supernatant solution. E4 was used to adjust the betaine concentration in the supernatant to 30–100 g / L. The pH was adjusted to 8–11 with stirring, and epichlorohydrin was added. The molar ratio of epichlorohydrin to betaine was 1–3:

1. The reaction was carried out at 40–70 °C for 2–6 h to obtain a betaine-type amphoteric epoxy monomer. In step ②, a tannic acid-containing solution is added to form a flocculant.

2. The method for preparing the starch-based polysaccharide flocculant for sewage purification according to claim 1, characterized in that: The weight ratio of the co-modified starch to the polymerized ferric salt is 1:1 to 15.

3. The method for preparing the starch-based polysaccharide flocculant for sewage purification according to claim 1, characterized in that: The specific preparation steps are as follows: A1 Weigh corn starch, dissolve it in an ethanol aqueous solution, and stir at 80-100℃ to gelatinize it; A2 is added to the gelatinization system by adding 2,3-epoxypropyltrimethylammonium chloride and betaine-type amphoteric epoxy monomers in an isochronous dripping or pre-mixed one-time feeding manner; Add NaOH aqueous solution slowly to the system of step A2, adjust the pH to 10-11, stir the reaction at 50-60℃ for 2-7 hours, and consider the reaction to be complete when a stable and transparent paste is formed. After the A4 reaction is complete, excess anhydrous ethanol is added to the dispersion system to precipitate the product. A5 uses a vacuum filter to filter the precipitated product under reduced pressure, dries the filter residue, and then pulverizes the product after it is completely dry to obtain co-modified starch.

4. The method for preparing the starch-based polysaccharide flocculant for sewage purification according to claim 3, characterized in that: In the preparation of the co-modified starch, the molar ratio of corn starch, 2,3-epoxypropyltrimethylammonium chloride and betaine-type amphoteric epoxy monomer is 1-2:1-1.5:0.1-0.

8.

5. The method for preparing the starch-based polysaccharide flocculant for sewage purification according to claim 1, characterized in that: The steps are as follows: B1. Disperse the modified starch in water and gelatinize at 80-95℃ for 30 min; B2 was added to a tannic acid extract with a final concentration of 10–150 g / L and a polymerized ferric salt with a final concentration of 10–150 g / L at pH 5.5–6.8, and stirred for 5–10 min to form an ferric salt complex. Add B3 dropwise to the co-modified starch dispersion and continue stirring for 10–30 min; Add 0.1–1.0 g / L potassium persulfate to B4 and continue the gelatinization reaction at 45–55℃ for 2–3 hours. After the B5 reaction is complete, excess anhydrous ethanol is added to the dispersion system to precipitate the product. B6 uses a vacuum filter to filter the precipitated product under reduced pressure, and then pulverizes the filter residue to obtain a flocculant. The weight ratio of the co-modified starch to the polymerized ferric salt is 1:1 to 15.

6. A method for purifying sewage, characterized in that: Add the starch-based polysaccharide flocculant prepared by any one of claims 1-5, dilute with water to form an orange-red, non-adherent aqueous flocculent solution, add it to cow manure water at a ratio controlled at 7‰ to 10‰, stir evenly at a speed of 200 to 500 r / min, let stand for 1 to 5 h to generate flocculated precipitate, and then separate the flocculated precipitate.

7. A composting method for promoting flocculation and sedimentation, characterized in that: The steps are as follows: C1 mixes the flocculated precipitate obtained by the manure purification method described in claim 6 with animal manure and straw on a dry basis, wherein the flocculated precipitate accounts for 10% to 30% of the dry basis mass of the mixture; C2 adjusts the C / N ratio of the mixture to 25:1 to 30:1 and the moisture content to 55% to 65%; C3 is added at 0.5 wt% of the compound microbial preparation on a wet basis. It is first mixed evenly with the flocs, and then mixed evenly with the flocs and straw. The porosity of the mixture is ≥35%, and the pH is 6.5-8.

0. It is then used for staged composting fermentation. C4 is used for composting fermentation under aerobic conditions, maintaining the pile temperature at 60-70℃ for a cumulative period of ≥3 days until the pile temperature drops to ambient temperature, thus obtaining the finished compost product.

8. The composting method for promoting maturation through flocculation and sedimentation according to claim 7, characterized in that: The stages of composting and fermentation are as follows: D1 pretreatment involves mixing livestock and poultry manure with straw and crushing it to a particle size ≤30 mm; adding flocculation sedimentation at a dry basis of 10-30%, adjusting the C / N ratio of the mixture to 25-30:1 and the moisture content to 55-65%; first, uniformly mixing the compound microbial preparation with the flocs at a wet basis of 0.5%, using the flocs as a carrier for the bacteria; then mixing it with the flocculation sedimentation and straw; the porosity of the mixture is ≥35%, and the pH is 6.5-8.

0. D2 primary fermentation utilizes aerobic fermentation for maturation. If windrow, trough, or membrane fermentation is used, the pile height should be controlled between 0.8 and 1.5 meters, and the pile width between 1.5 and 2.5 meters. If forced aeration is used, the ventilation intensity should be no less than 0.1 m³·min⁻¹·m⁻³, maintaining a dissolved oxygen level of no less than 10% by pile volume. If windrow or trough fermentation is used, the pile temperature should be monitored until it reaches 50–60°C, at which point the pile should be turned once. The pile temperature should be maintained at 60–70°C for 3–7 days, followed by natural cooling to complete the maturation process. If a reactor-type aerobic fermentation is used, the high temperature should be monitored until it reaches 60–70°C for at least 3 days, followed by natural cooling to complete the maturation process. If the reactor temperature is maintained at 60–70°C for less than 3 days, fermentation failure detection is required. D3 secondary fermentation involves transferring the materials from the primary fermentation to the secondary fermentation site for further stacking, maintaining proper ventilation and humidity, so that the organic matter that was not fully decomposed in the primary fermentation continues to degrade and humify until the stack temperature stabilizes within 10°C above the ambient temperature.

Images