A polyacrylamide flocculant for sludge treatment and its preparation process

Abstract

This invention relates to the field of flocculant technology, and discloses a polyacrylamide flocculant for sludge treatment and its preparation process. The polyacrylamide flocculant for sludge treatment prepared by this invention comprises the following raw materials: water, modified starch, prepolymer, and bromoethane; the prepolymer includes butyl acrylate, water, sodium dodecyl sulfate, acrylamide, N,N-methylenebisacrylamide, glycidyl methacrylate, modified silica, ammonium persulfate, and sodium bisulfite; the modified silica includes vinyltriethoxysilane-modified nano silica; the modified starch includes corn starch, N,N'-(1,2-ethanediyl)bisaspartic acid, sodium alginate, water, sodium sulfate, and phosphorus oxychloride; the obtained polyacrylamide flocculant for sludge treatment has a high molecular weight hyperbranched structure and good flocculation effect.

Description

Technical Field

[0001] This invention relates to the field of flocculant technology, and discloses a polyacrylamide flocculant for sludge treatment and its preparation process. Background Technology

[0002] Sludge has a wide range of sources and a complex composition, including microorganisms, lipids, cellulose, heavy metals, and inorganic non-metallic elements such as nitrogen and phosphorus. If not properly treated, it can cause serious harm to the environment. Sludge treatment is complex. Due to its high water content, sludge must first undergo dewatering and volume reduction treatment. Existing dewatering technologies, such as composting and incineration, have problems with long processing times or high costs.

[0003] Flocculants are substances that reduce or eliminate the stability of particles in water, causing dispersed particles to aggregate, flocculate, and precipitate, thereby achieving solid-liquid separation. Adding flocculants is a very economical and effective water treatment method, with low investment costs, high treatment efficiency, and simple operation. Currently, polyacrylamide flocculants are commonly used, but as pollutant compositions become increasingly complex, existing flocculants are inadequate and their effectiveness is unsatisfactory. At the same time, with increasing environmental protection requirements, the environmental friendliness of flocculants is gradually gaining attention. Therefore, researching a polyacrylamide flocculant for sludge treatment that can handle complex pollutants, has good performance, is environmentally friendly, has good degradability, and is low-cost, as well as its preparation process, is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a polyacrylamide flocculant for sludge treatment and its preparation process, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A preparation process for a polyacrylamide flocculant for sludge treatment includes the following steps: taking water, modified starch, and polyacrylamide prepolymer, stirring evenly, heating to react, cooling, slowly adding bromoethane, stirring to react, filtering to obtain the solid, washing, and drying to obtain the polyacrylamide flocculant for sludge treatment.

[0007] In a more optimized manner, the polyacrylamide flocculant for sludge treatment comprises the following raw materials, by mass parts: 50-60 parts water, 2-5 parts modified starch, 5-10 parts polyacrylamide prepolymer, and 4-8 parts bromoethane.

[0008] In a more optimized manner, the preparation of the modified starch includes the following steps: take corn starch, modifier, water, and sodium sulfate, adjust the pH to 9-10, stir and add phosphorus oxychloride dropwise, stir at 30-40℃ for 1-2 hours, adjust the pH to 5.5-6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch.

[0009] In a more optimized manner, the modified starch comprises the following raw materials, by mass parts: 10-20 parts corn starch, 2-8 parts modifier, 30-40 parts water, 0.5-1.5 parts sodium sulfate, and 0.05-0.15 parts phosphorus oxychloride.

[0010] More optimally, the mass ratio of the modifier to corn starch is 5:1 to 5:2; the modifier includes N,N'-(1,2-ethanediyl)bisaspartic acid and sodium alginate, with a mass ratio of 1:1.

[0011] In a more optimized manner, the preparation of the polyacrylamide prepolymer includes the following steps: under a nitrogen atmosphere, butyl acrylate, water, and sodium dodecyl sulfate are taken and stirred until emulsification is complete. Acrylamide, crosslinking agent, and water are added and stirred to dissolve. Glycidyl methacrylate and modified silica are added and stirred evenly. The temperature is raised to 50-60°C, an initiator is added, and the mixture is stirred and reacted for 6-7 hours. The mixture is purified three times with ethanol to obtain a white product. The product is dissolved in water, dialyzed for 72 hours, and freeze-dried to obtain the polyacrylamide prepolymer.

[0012] More preferably, the polyacrylamide prepolymer comprises the following raw materials, by mass parts: 5-10 parts butyl acrylate, 160-240 parts water, 0.05-0.1 parts sodium dodecyl sulfate, 100-120 parts acrylamide, 0.05-0.2 parts crosslinking agent, 1-2 parts glycidyl methacrylate, 0.5-2 parts modified silica, and 3-6 parts initiator.

[0013] More preferably, the crosslinking agent includes N,N-methylenebisacrylamide.

[0014] More preferably, the initiator includes, but is not limited to, ammonium persulfate and sodium bisulfite.

[0015] In a more optimized manner, the preparation of the modified silica includes the following steps: take silica, ethanol, and water, ultrasonically stir for 30-40 min, add vinyltriethoxysilane, reflux at 60-70°C for 6-7 h, centrifuge, wash, and dry to obtain modified silica.

[0016] In a more optimized manner, the modified silica comprises the following raw materials: 2-5 parts silica, 200-300 parts ethanol, 100-200 parts water, and 0.5-2 parts vinyltriethoxysilane.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) A polyacrylamide flocculant for sludge treatment is prepared using modified starch as the matrix. Starch is composed of amylose macromolecules and branched starch macromolecules, containing many free hydroxyl groups. It has good water solubility, is environmentally friendly, easy to degrade, and has low cost. Starch-based flocculants complete the flocculation process through charge neutralization, adsorption bridging, netting and sweeping, and hydrophobic association, resulting in good flocculation effect. The present invention modifies starch before use, using N,N'-(1,2-ethanediyl)bisaspartic acid and sodium alginate as modifiers. Both are green and biodegradable modifiers, which can improve the starch complexing and adsorption capacity while also improving the problem of poor starch solubility in cold water. The mass ratio of N,N'-(1,2-ethanediyl)bisaspartic acid to sodium alginate was controlled at 1:1. N,N'-(1,2-ethanediyl)bisaspartic acid has a good complexing effect but is expensive. Adding sodium alginate partially replaces it to reduce costs. Sodium alginate has a good flocculation effect on heavy metal ions and cationic dyes, but too much sodium alginate should not be added, as it will increase the viscosity of the flocculant and hinder dispersion. The total amount of both added to the corn starch was in a mass ratio of 5:1 to 5:2 to obtain modified starch with good complexing ability and hydroxyl functional groups that can participate in subsequent reactions.

[0018] (2) A polyacrylamide prepolymer was prepared using butyl acrylate, acrylamide, N,N-methylenebisacrylamide, glycidyl methacrylate, and modified silica. Butyl acrylate contains hydrophobic ester groups and has a low cost, which can improve the problems of insufficient softness and dispersibility of polyacrylamide prepolymer in aqueous solution. N,N-methylenebisacrylamide promotes the formation of multi-branched structure and helps to enhance flocculation effect. The addition of modified silica filler can increase the surface area of ​​flocculant, provide more adsorption sites, and accelerate the flocculation process. Glycidyl methacrylate provides epoxy groups, which can be grafted with modified starch in subsequent steps.

[0019] (3) In this invention, N,N-methylenebisacrylamide is introduced as a crosslinking agent, modified silica filler is introduced to increase inorganic crosslinking sites, and modified starch is introduced as a matrix to react with polyacrylamide prepolymer to obtain a hyperbranched structure. After obtaining the hyperbranched structure, bromoethane is added to introduce cations. The high polarity of the cation groups will have an adverse effect on the molecular weight control. Thus, a hyperbranched high molecular weight polyacrylamide flocculant with good flocculation performance is obtained. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The following examples include the following raw materials: corn starch (item number: S11006, Shanghai Yuanye Biotechnology Co., Ltd.); N,N'-(1,2-ethanediyl)bisaspartic acid (EDDS, item number: Y0129, Suzhou Yake Technology Co., Ltd.); sodium alginate (item number: S11053, Shanghai Yuanye Biotechnology Co., Ltd.); sodium sulfate (item number: S24155, CAS: 7757-82-6, Shanghai Yuanye Biotechnology Co., Ltd.); phosphorus oxychloride (CAS: 10025-87-3); silicon dioxide (~12nm, Zhejiang Manli Nanotechnology Co., Ltd.); ethyl... Alcohols (CAS: 64-17-5); Vinyltriethoxysilane (CAS: 78-08-0); Butyl acrylate (CAS: 141-32-2); Sodium dodecyl sulfate (CAS: 151-21-3); Acrylamide (CAS: 79-06-1); N,N-methylenebisacrylamide (CAS: 110-26-9); Glycidyl methacrylate (CAS: 106-91-2); Ammonium persulfate (CAS: 7727-54-0); Sodium bisulfite (CAS: 7631-90-5); Bromoethane (CAS: 74-96-4);

[0022] The following quantities are by weight;

[0023] Example 1: S1: Take 15 parts corn starch, 1.5 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 1.5 parts sodium alginate, 40 parts water, and 1 part sodium sulfate. Adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise. Stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0024] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0025] S3: Under a nitrogen atmosphere, take 8 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 120 parts acrylamide, 0.15 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 2 parts glycidyl methacrylate and 1 part modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0026] S4: Take 60 parts water, 4 parts modified starch, and 8 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 6 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash, and dry to obtain polyacrylamide flocculant for sludge treatment.

[0027] Example 2: S1: Take 20 parts corn starch, 2 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 2 parts sodium alginate, 40 parts water, and 1 part sodium sulfate. Adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise. Stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0028] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0029] S3: Under a nitrogen atmosphere, take 10 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 120 parts acrylamide, 0.2 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 2 parts glycidyl methacrylate and 2 parts modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0030] S4: Take 60 parts water, 5 parts modified starch, and 10 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 8 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash, and dry to obtain polyacrylamide flocculant for sludge treatment.

[0031] Example 3: S1: Take 10 parts corn starch, 1 part N,N'-(1,2-ethanediyl)bisaspartic acid, 1 part sodium alginate, 40 parts water, and 1 part sodium sulfate. Adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise. Stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0032] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0033] S3: Under a nitrogen atmosphere, take 5 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 100 parts acrylamide, 0.05 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 1 part glycidyl methacrylate and 0.5 parts modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0034] S4: Take 60 parts water, 2 parts modified starch, and 5 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 4 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash, and dry to obtain polyacrylamide flocculant for sludge treatment.

[0035] Example 4: S1: Take 20 parts corn starch, 2 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 2 parts sodium alginate, 40 parts water, and 1 part sodium sulfate. Adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise. Stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0036] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0037] S3: Under a nitrogen atmosphere, take 5 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 120 parts acrylamide, 0.2 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 1 part glycidyl methacrylate and 2 parts modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0038] S4: Take 60 parts water, 5 parts modified starch, and 10 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 7 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash and dry to obtain polyacrylamide flocculant for sludge treatment.

[0039] Comparative Example 1 (using chitosan instead of corn starch, with the remaining steps the same as in Example 1): S1: Take 15 parts chitosan, 1.5 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 1.5 parts sodium alginate, 40 parts water, and 1 part sodium sulfate. Adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise. Stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind, and pass through a 100-mesh sieve to obtain modified chitosan;

[0040] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0041] S3: Under a nitrogen atmosphere, take 8 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 120 parts acrylamide, 0.15 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 2 parts glycidyl methacrylate and 1 part modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0042] S4: Take 60 parts water, 4 parts modified chitosan, and 8 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 6 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash, and dry to obtain polyacrylamide flocculant for sludge treatment.

[0043] Comparative Example 2 (without using bromoethane, dimethyl diallyl ammonium chloride was added directly to the polyacrylic acid prepolymer, and the remaining steps were the same as in Example 1): S1: Take 15 parts corn starch, 1.5 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 1.5 parts sodium alginate, 40 parts water, and 1 part sodium sulfate, adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise, stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0044] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0045] S3: Under a nitrogen atmosphere, take 8 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified, add 120 parts acrylamide, 0.15 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 2 parts glycidyl methacrylate, 1 part modified silica, and 6 parts dimethyl diallyl ammonium chloride, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0046] S4: Take 60 parts water, 4 parts modified starch, and 8 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash, and dry to obtain polyacrylamide flocculant for sludge treatment.

[0047] Comparative Example 3 (the amounts of N,N'-(1,2-ethanediyl)bisaspartic acid and sodium alginate were changed, while the rest of the steps were the same as in Example 1): S1: Take 15 parts corn starch, 0.5 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 2.5 parts sodium alginate, 40 parts water, and 1 part sodium sulfate, adjust the pH to 10, stir and add 0.1 parts phosphorus oxychloride dropwise, stir at 40°C for 2 hours, adjust the pH to 6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0048] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0049] S3: Under a nitrogen atmosphere, take 8 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 120 parts acrylamide, 0.15 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 2 parts glycidyl methacrylate and 1 part modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0050] S4: Take 60 parts water, 4 parts modified starch, and 8 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 6 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash, and dry to obtain polyacrylamide flocculant for sludge treatment.

[0051] Comparative Example 4 (reduced amount of polyacrylamide prepolymer added, other steps are the same as in Example 1): S1: Take 15 parts corn starch, 1.5 parts N,N'-(1,2-ethanediyl)bisaspartic acid, 1.5 parts sodium alginate, 40 parts water, and 1 part sodium sulfate, adjust pH=10, stir and add 0.1 parts phosphorus oxychloride dropwise, stir at 40℃ for 2 hours, adjust pH=6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch;

[0052] S2: Take 5 parts of silica, 300 parts of ethanol, and 100 parts of water, stir ultrasonically for 30 minutes, add 2 parts of vinyltriethoxysilane, reflux at 70°C for 7 hours, centrifuge, wash, and dry to obtain modified silica.

[0053] S3: Under a nitrogen atmosphere, take 8 parts butyl acrylate, 120 parts water, and 0.1 parts sodium dodecyl sulfate, stir until emulsified completely, add 120 parts acrylamide, 0.15 parts N,N-methylenebisacrylamide, and 120 parts water, stir to dissolve, add 2 parts glycidyl methacrylate and 1 part modified silica, stir evenly, heat to 60℃, add 4 parts ammonium persulfate and 1 part sodium bisulfite, stir to react for 7 hours, purify with ethanol three times to obtain a white product, dissolve in water, dialyze for 72 hours, freeze dry to obtain polyacrylamide prepolymer;

[0054] S4: Take 60 parts water, 4 parts modified starch, and 2 parts polyacrylamide prepolymer, stir evenly, adjust pH to 13, react at 90℃ for 4 hours, cool to 45℃, slowly add 6 parts bromoethane, stir for 10 hours, cool to room temperature, add 200 parts ethanol, stir for 1 hour, filter to obtain solid, wash and dry to obtain polyacrylamide flocculant for sludge treatment.

[0055] Experiment: (1) Sludge with a water content of more than 95% from a sewage treatment plant was selected. 2g of polyacrylamide flocculant prepared in Examples 1-4 and Comparative Examples 1-4 was added to 1L of water and stirred for 30min to obtain working solution. 20mL of working solution was added to 500mL of sludge and stirred rapidly. The transmittance of the supernatant after flocculation was measured to evaluate the flocculation performance. (2) The ratio of BOD / COD (B / C) of the supernatant after flocculation was tested to reflect the microbial degradability. The specific data are shown in the table below.

[0056] Light transmittance / % B / C Example 1 92 0.85 Example 2 91 0.82 Example 3 92 0.83 Example 4 92 0.83 Comparative Example 1 85 0.75 Comparative Example 2 82 0.75 Comparative Example 3 79 0.74 Comparative Example 4 75 0.74

[0057] Conclusions: In Comparative Example 1, the performance of the chitosan-based polyacrylamide flocculant was inferior to that of the Example, possibly due to its poor water solubility; in Comparative Example 2, the introduction of cationic substances during the preparation of the polyacrylamide prepolymer resulted in uncontrollable product molecular weight and decreased flocculation capacity; in Comparative Example 3, changing the amount of N,N'-(1,2-ethanediyl)bisaspartic acid and sodium alginate added did not result in as good a flocculation effect as the Example; in Comparative Example 4, the reduced amount of polyacrylamide prepolymer added was not conducive to the formation of hyperbranched structures, leading to a decrease in performance; therefore, the solution provided by this invention can provide a polyacrylamide flocculant for sludge treatment that can cope with complex pollutants, has good performance, is environmentally friendly, and has a low cost, as well as its preparation process.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0059] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation process for a polyacrylamide flocculant for sludge treatment, characterized in that: The process includes the following steps: taking water, modified starch, and polyacrylamide prepolymer, stirring evenly, heating to react, cooling, slowly adding bromoethane, stirring to react, filtering to obtain the solid, washing, and drying to obtain polyacrylamide flocculant for sludge treatment; The preparation of the modified starch includes the following steps: take corn starch, modifier, water, sodium sulfate, adjust pH to 9-10, stir and add phosphorus oxychloride dropwise, stir at 30-40℃ for 1-2 hours, adjust pH to 5.5-6, centrifuge to collect the precipitate, wash, dry, grind finely, and pass through a 100-mesh sieve to obtain modified starch; The mass ratio of the modifier to corn starch is 5:1 to 5:2; the modifier includes N,N'-(1,2-ethanediyl)bisaspartic acid and sodium alginate, with a mass ratio of 1:

1. The preparation of the polyacrylamide prepolymer includes the following steps: Under a nitrogen atmosphere, butyl acrylate, water, and sodium dodecyl sulfate are taken and stirred until emulsification is complete. Acrylamide, crosslinking agent, and water are added and stirred to dissolve. Glycidyl methacrylate and modified silica are added and stirred evenly. The temperature is raised to 50-60℃, an initiator is added, and the reaction is stirred for 6-7 hours. The product is purified three times with ethanol to obtain a white product. The product is dissolved in water, dialyzed for 72 hours, and freeze-dried to obtain the polyacrylamide prepolymer. The polyacrylamide flocculant for sludge treatment comprises the following raw materials, by mass: 50-60 parts water, 2-5 parts modified starch, 5-10 parts polyacrylamide prepolymer, and 4-8 parts bromoethane.

2. The preparation process of a polyacrylamide flocculant for sludge treatment according to claim 1, characterized in that: The modified starch comprises the following raw materials, by mass: 10-20 parts corn starch, 2-8 parts modifier, 30-40 parts water, 0.5-1.5 parts sodium sulfate, and 0.05-0.15 parts phosphorus oxychloride.

3. The preparation process of a polyacrylamide flocculant for sludge treatment according to claim 1, characterized in that: The polyacrylamide prepolymer comprises the following raw materials, by mass parts: 5-10 parts butyl acrylate, 160-240 parts water, 0.05-0.1 parts sodium dodecyl sulfate, 100-120 parts acrylamide, 0.05-0.2 parts crosslinking agent, 1-2 parts glycidyl methacrylate, 0.5-2 parts modified silica, and 3-6 parts initiator.

4. The preparation process of a polyacrylamide flocculant for sludge treatment according to claim 1, characterized in that: The preparation of the modified silica includes the following steps: Take silica, ethanol, and water, and ultrasonically stir for 30-40 minutes. Add vinyltriethoxysilane, reflux at 60-70°C for 6-7 hours, centrifuge, wash, and dry to obtain modified silica.

5. The preparation process of a polyacrylamide flocculant for sludge treatment according to claim 4, characterized in that: The modified silica comprises the following raw materials: 2-5 parts silica, 200-300 parts ethanol, 100-200 parts water, and 0.5-2 parts vinyltriethoxysilane.

6. The polyacrylamide flocculant for sludge treatment obtained by the preparation process of a polyacrylamide flocculant for sludge treatment according to any one of claims 1 to 5.