Sewage treatment agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sewage treatment, and particularly discloses a sewage treatment agent as well as a preparation method and application thereof. The sewage treatment agent comprises modified polyaluminum chloride, a low-temperature flocculant and a plurality of auxiliary components, the modified polyaluminum chloride is obtained by doping nano boron nitride and modifying with a low-temperature modifier, and the low-temperature flocculant is obtained by copolymerization of polyacrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the preparation method mainly comprises the steps of raw material dissolution, mixing reaction, flocculation compounding and the like. The sewage treatment agent can be used for domestic sewage treatment in a low-temperature environment of 0-5 DEG C, has the advantages of excellent low-temperature resistance, high hydrolysis speed, high pollutant removal rate and good stability, and can effectively overcome the defect of poor low-temperature treatment effect of an existing agent.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a wastewater treatment agent, its preparation method, and its application. Background Technology

[0002] Domestic sewage refers to various types of wastewater generated in the daily lives of urban residents, including kitchen wastewater, laundry wastewater, and personal hygiene wastewater. Its discharge volume is enormous, accounting for over 70% of total urban sewage discharge. Domestic sewage contains not only organic pollutants such as carbohydrates, proteins, and oils, but also certain amounts of ammonia nitrogen, total phosphorus, heavy metal ions, and trace amounts of emerging pollutants such as detergents and antibiotics. In routine testing, its chemical oxygen demand (COD) is typically between 180-380 mg / L, ammonia nitrogen concentration between 18-45 mg / L, and total phosphorus concentration between 4-9 mg / L. If domestic sewage is discharged directly without proper treatment, it will rapidly lead to eutrophication of receiving water bodies, promoting algae growth and forming black and odorous water bodies, damaging aquatic ecosystems. Simultaneously, harmful components in the sewage can seep into groundwater, polluting drinking water sources and threatening public health. Therefore, the efficient purification and treatment of domestic sewage has become an important issue in the field of ecological environmental protection.

[0003] Currently, domestic sewage treatment generally adopts a process flow of "pretreatment-biological treatment-advanced treatment". The pretreatment stage removes large suspended solids and sand through screens and grit chambers. The biological treatment stage utilizes microorganisms to degrade organic pollutants in the water and achieve nitrogen and phosphorus conversion. The advanced treatment stage further purifies the water quality through processes such as coagulation, flocculation, and disinfection to ensure that the effluent meets standards. To improve the treatment efficiency at each stage, various sewage treatment agents are widely used, mainly including inorganic coagulants (polyaluminum chloride, polyferric sulfate), organic flocculants (polyacrylamide, polyquaternium salts), bio-enhancing agents, and phosphorus and nitrogen removal auxiliary agents. Among them, coagulants and flocculants are the core agents for solid-liquid separation, causing pollutants in the water to aggregate and settle through charge neutralization and adsorption bridging. Bio-enhancing agents are used to improve microbial activity, while auxiliary agents are used to specifically remove indicators such as ammonia nitrogen and total phosphorus. These various agents work synergistically to complete the purification of domestic sewage.

[0004] While existing wastewater treatment agents can meet basic treatment needs, they still have many shortcomings in practical applications, especially in northern winters or high-altitude, low-temperature regions where ambient temperatures often drop below 5°C. At these temperatures, inorganic coagulants are prone to slowed hydrolysis, resulting in slow and loose floc formation. Organic flocculants experience reduced molecular chain activity and a significant decrease in adsorption and bridging capacity. The activation effect of bio-enhancing agents on microorganisms is also significantly weakened, leading to incomplete pollutant aggregation and sedimentation. Key indicators such as ammonia nitrogen, total phosphorus, and COD are difficult to meet discharge standards. Therefore, existing wastewater treatment agents suffer from poor low-temperature resistance, resulting in low wastewater treatment efficiency, high treatment costs, and difficulty in meeting effluent quality standards in low-temperature environments. This fails to meet the actual needs for efficient wastewater purification under different climatic conditions, limiting their widespread application in low-temperature regions. Summary of the Invention

[0005] In view of this, the present invention proposes a wastewater treatment agent, its preparation method and application to solve the above problems.

[0006] The technical solution of this invention is implemented as follows:

[0007] A wastewater treatment agent comprising the following raw materials: 35-45 parts modified polyaluminum chloride, 10-15 parts low-temperature flocculant, 2-4 parts sodium lignosulfonate, 8-12 parts polyferric sulfate, 3-5 parts zinc sulfate, 1-2 parts sodium carbonate, 2-3 parts calcium silicate, 1-3 parts chitosan, 0.5-1.5 parts borax, and 1-2 parts hydrogen peroxide.

[0008] Modified polyaluminum chloride is obtained by modifying polyaluminum chloride with nano-boron nitride doping and low-temperature modifier.

[0009] The low-temperature flocculant is obtained by copolymerizing polyacrylamide with the low-temperature active monomer 2-acrylamide-2-methylpropanesulfonic acid.

[0010] By adopting the above technical solution, modified polyaluminum chloride and low-temperature flocculant, as the two core components, work synergistically to specifically address the low-temperature performance defects of existing agents. Specifically, the modified polyaluminum chloride, after being doped with nano-boron nitride and modified with a low-temperature modifier, effectively improves the problems of slow hydrolysis and loose flocs in traditional polyaluminum chloride at low temperatures. It can quickly exert a charge neutralization effect in low-temperature environments, promoting the initial aggregation of pollutants. The low-temperature flocculant, copolymerized from polyacrylamide and 2-acrylamide-2-methylpropanesulfonic acid, overcomes the shortcomings of traditional organic flocculants such as molecular chain coiling and insufficient adsorption bridging capacity at low temperatures. It can agglomerate the initially aggregated micro-flocs into dense flocs, accelerating solid-liquid separation. The synergistic effect of the two significantly improves the purification efficiency at low temperatures.

[0011] The rational addition of auxiliary components such as sodium lignosulfonate, polyferric sulfate, and zinc sulfate further enhances the low-temperature purification efficiency of the core components, while also compensating for the shortcomings of a single core component in terms of pollutant removal specificity. The synergistic effect of polyferric sulfate and modified polyaluminum chloride enhances the coagulation effect, especially improving the removal capacity of total phosphorus at low temperatures. Sodium lignosulfonate, as a coagulant aid, helps stabilize flocs and prevents floc breakage at low temperatures. Chitosan, borax, and other components further optimize the dispersibility and stability of the agents. The addition of hydrogen peroxide helps degrade recalcitrant organic pollutants in wastewater. The synergistic effect of these components ensures that key indicators such as COD, ammonia nitrogen, and total phosphorus in wastewater meet discharge standards under low-temperature conditions.

[0012] In summary, the technical solution of this application, through the reasonable combination of modified polyaluminum chloride, low-temperature flocculant and various auxiliary components, fundamentally solves the core defect of insufficient low-temperature resistance of existing sewage treatment agents, and provides a brand-new technical solution for the purification of domestic sewage in low-temperature environments.

[0013] Furthermore, the modified polyaluminum chloride was prepared using the following method:

[0014] A1. Mix polyaluminum chloride and nano boron nitride, and ultrasonically disperse at 300-400W for 30-50 minutes to obtain polyaluminum chloride substrate;

[0015] A2. Mix silane coupling agent KH-792, L-tartaric acid and deionized water, stir at 40-50℃ for 40-60 min, cool to room temperature to obtain low temperature modifier;

[0016] A3. Add the low-temperature modifier to the polyaluminum chloride substrate, adjust the pH of the system to 3.8-4.2, and stir the reaction at a constant temperature of 38-42℃ for 90-100 min. After the reaction is completed, vacuum dry and pulverize to obtain modified polyaluminum chloride.

[0017] By adopting the above technical solution, the preparation method is scientific and reasonable, which can effectively control the structure and properties of modified polyaluminum chloride and ensure that it can stably play a coagulation role in a low-temperature environment. Among them, the synergistic treatment of substrate doping and low-temperature modifier modification not only reduces the hydrolysis activation energy of polyaluminum chloride and increases the low-temperature hydrolysis rate, but also enhances its floc strength, avoids the flocs from becoming loose and broken at low temperatures, provides a good foundation for the subsequent flocculation process, and further improves the low-temperature purification efficiency of the entire wastewater treatment agent.

[0018] Furthermore, in step A1, the boron nitride nanoparticles have a particle size of 50-80 nm, and the amount of boron nitride nanoparticles added is 3%-5% of the mass of polyaluminum chloride.

[0019] Furthermore, in step A2, the mass ratio of silane coupling agent KH-792, L-tartaric acid, and deionized water is (3-5):1:(6-8).

[0020] By adopting the above technical solution, the reasonable ratio of silane coupling agent KH-792 and L-tartaric acid can achieve a synergistic effect between the two. KH-792 provides coordination active sites to form stable coordination bonds with Al3+ in polyaluminum chloride, while L-tartaric acid regulates the complexation stability and prevents the modifier from falling off. At the same time, the reasonable addition of deionized water can ensure that the components of the modifier are fully dissolved and uniformly mixed, thereby ensuring that the low-temperature modifier can play an efficient role, further reducing the low-temperature hydrolysis activation energy of polyaluminum chloride and improving its low-temperature activity.

[0021] Furthermore, in step A3, the amount of low-temperature modifier added is 10%-12% of the mass of the polyaluminum chloride substrate.

[0022] Furthermore, the low-temperature flocculant is prepared using the following method:

[0023] Using polyacrylamide as a base material, 6%-8% of its low-temperature active monomer 2-acrylamide-2-methylpropanesulfonic acid is added. After adding an initiator, the polymerization reaction is carried out at 25-30℃ for 120 minutes. After drying, a low-temperature flocculant is obtained.

[0024] By adopting the above technical solution, through the copolymerization reaction of polyacrylamide and 2-acrylamide-2-methylpropanesulfonic acid, a low-temperature active monomer is introduced into the molecular structure of the flocculant, giving the flocculant excellent low-temperature stability. This can effectively inhibit the shrinkage of molecular chains at low temperatures, maintain the extensibility of molecular chains, and thus enhance its adsorption and bridging ability. It can efficiently connect the small flocs that have been initially aggregated by modified polyaluminum chloride to form dense, easily settled flocs, accelerate solid-liquid separation, and ensure the complete removal of pollutants at low temperatures.

[0025] Furthermore, the initiator is ammonium persulfate and sodium bisulfite in a mass ratio of (2-3):1, and the amount of the initiator added is 0.8%-1.2% of the polyacrylamide.

[0026] By adopting the above technical solution, a composite initiator of ammonium persulfate and sodium bisulfite in a specific ratio can initiate the copolymerization reaction of polyacrylamide and 2-acrylamide-2-methylpropanesulfonic acid under mild conditions, ensuring that the reaction proceeds fully and improving the grafting rate and molecular weight of the low-temperature flocculant. The reasonable amount of initiator added can avoid incomplete reaction due to insufficient initiator, or the initiator being too much and affecting the low-temperature activity of the flocculant, thereby ensuring that the low-temperature flocculant can stably play its adsorption and bridging role in the low-temperature environment, and synergistically improve the sewage purification effect with modified polyaluminum chloride.

[0027] This application also provides a method for preparing a wastewater treatment agent, using the following technical solution:

[0028] A method for preparing a wastewater treatment agent includes the following steps:

[0029] S1. Add modified polyaluminum chloride, polyferric sulfate, zinc sulfate, and calcium silicate to deionized water. The amount of deionized water added is 1.2-1.5 times the total mass of the above four raw materials. Stir at 30-35℃ and 100-120r / min for 30-40 minutes until completely dissolved to obtain a mixed salt solution.

[0030] S2. Add sodium lignosulfonate, chitosan, and borax to the mixed salt solution obtained in step S1 in sequence. Adjust the stirring speed to 150-180 r / min and continue stirring for 20-30 min. During this period, slowly add sodium carbonate and adjust the pH of the system to 6.5-7.5 to form a uniform suspension.

[0031] S3. Add a low-temperature flocculant to the suspension obtained in step S2, reduce the stirring speed to 80-100 r / min, stir for 40-50 min, add hydrogen peroxide, continue stirring for 10-15 min, let stand for 15-20 min, and obtain the wastewater treatment agent.

[0032] This application also provides an application of a wastewater treatment agent, which is used for treating domestic wastewater in a low-temperature environment of 0-5℃; the dosage of the wastewater treatment agent is 180-280 mg / L, and after addition, it is stirred at 200-220 r / min for 25-30 min, then stirred at 50-60 r / min for 10-15 min, and allowed to settle for 50-60 min to achieve efficient removal of pollutants from wastewater.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. Addressing the core shortcomings of existing inorganic coagulants—slow hydrolysis rate and loose, brittle flocs below 5℃—this application achieves a breakthrough improvement in the low-temperature performance of polyaluminum chloride (PAC) through a dual innovative strategy of "nano-doping + composite modification system." The introduction of nano-boron nitride constructs highly active sites for the hydrolysis reaction, significantly enhancing the mechanical stability of the flocs and solving the problem of floc breakage at low temperatures from a physical structural perspective. Meanwhile, the composite modifier composed of KH-792 and L-tartaric acid, through the synergistic effect of coordination bonding and complexation stability, significantly reduces the hydrolysis activation energy of PAC. This modification mechanism enables the coagulant to rapidly complete hydrolysis in low-temperature environments, efficiently releasing high-valence polynuclear complex ions, quickly neutralizing the surface charge of wastewater colloids, and promoting the formation of stable initial aggregates of pollutants. This completely overcomes the shortcomings of traditional coagulants' poor treatment efficiency at low temperatures, laying a solid foundation for subsequent deep purification.

[0035] 2. This application reconstructs the molecular structure of polyacrylamide by introducing 2-acrylamido-2-methylpropanesulfonic acid (AMPS), a low-temperature active monomer. The strongly hydrophilic sulfonic acid groups in the AMPS molecule effectively resist the binding of the molecular chain by the low-temperature environment, ensuring that the flocculant maintains a relaxed spatial conformation in low-temperature wastewater. This structural characteristic endows the flocculant with excellent low-temperature activity, enabling it to accurately capture the small flocs initially aggregated by the modified coagulant. Through efficient adsorption bridging, it agglomerates the dispersed small particles into large, dense flocs. This innovative design perfectly solves the key problem of "inability to bridge and aggregate" at low temperatures, forming a highly efficient relay purification mode with modified polyaluminum chloride, significantly accelerating the solid-liquid separation process and ensuring the complete sedimentation of pollutants under low-temperature conditions.

[0036] 3. This application utilizes modified polyaluminum chloride and a low-temperature flocculant as its two core components to form a closed-loop synergy from "charge neutralization" to "bridging and agglomeration," ensuring the efficient removal of suspended pollutants. Simultaneously, polyferric sulfate and zinc sulfate synergistically enhance the deep removal of phosphorus at low temperatures; sodium lignosulfonate and chitosan further stabilize the low-temperature floc structure, preventing breakage during sedimentation; and hydrogen peroxide assists in the degradation of organic pollutants that are difficult to biodegrade at low temperatures. Each auxiliary component is precisely adapted to the low-temperature action mechanism of the core components, compensating for the shortcomings of single core materials in pollutant removal targeting. This achieves simultaneous and efficient purification of multiple indicators such as organic pollutants, nitrogen, and phosphorus in domestic sewage under low-temperature conditions, solving the application problems of low treatment efficiency and unstable effluent quality in existing technologies. Detailed Implementation

[0037] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0038] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0039] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0040] Preparation example of modified polyaluminum chloride

[0041] Preparation Example 1

[0042] Modified polyaluminum chloride was prepared by the following method:

[0043] A1. Take 100g of polyaluminum chloride, add 3g of boron nitride nanoparticles with a particle size of 50nm, put them into an ultrasonic disperser, adjust the ultrasonic power to 300W, and ultrasonically disperse for 30min to obtain a uniformly dispersed polyaluminum chloride substrate.

[0044] A2. Take 15g of silane coupling agent KH-792, 5g of L-tartaric acid and 30g of deionized water in a mass ratio of 3:1:6, add them to a three-necked flask, place it in a constant temperature water bath, adjust the temperature to 40℃, stir the reaction at a constant temperature for 40min, and cool to room temperature after the reaction is completed to obtain a low temperature modifier.

[0045] A3. Take 100g of the above-mentioned polyaluminum chloride substrate, add 10g of low-temperature modifier, adjust the pH of the system to 3.8 with dilute hydrochloric acid, place it in a constant temperature water bath, adjust the temperature to 38℃, and stir the reaction at a constant temperature for 90min. After the reaction is completed, put the product into a vacuum drying oven and vacuum dry it for 2h under a vacuum degree of -0.06MPa and a temperature of 60℃. After drying, pulverize it to 80 mesh to obtain modified polyaluminum chloride.

[0046] Preparation Example 2

[0047] Modified polyaluminum chloride was prepared by the following method:

[0048] A1. Take 100g of polyaluminum chloride, add 4g of boron nitride nanoparticles with a particle size of 65nm, put them into an ultrasonic disperser, adjust the ultrasonic power to 350W, and ultrasonically disperse for 40min to obtain a uniformly dispersed polyaluminum chloride substrate.

[0049] A2. Take 20g of silane coupling agent KH-792, 5g of L-tartaric acid and 35g of deionized water in a mass ratio of 4:1:7, add them to a three-necked flask, place it in a constant temperature water bath, adjust the temperature to 45℃, stir the reaction at a constant temperature for 50min, and cool to room temperature after the reaction is completed to obtain a low temperature modifier.

[0050] A3. Take 100g of the above-mentioned polyaluminum chloride substrate, add 11g of low-temperature modifier, adjust the pH of the system to 4.0 with dilute hydrochloric acid, place it in a constant temperature water bath, adjust the temperature to 40℃, and stir the reaction at a constant temperature for 95min. After the reaction is completed, put the product into a vacuum drying oven and vacuum dry it for 2.5h under vacuum conditions of -0.07MPa and 65℃. After drying, pulverize it to 90 mesh to obtain modified polyaluminum chloride.

[0051] Preparation Example 3

[0052] Modified polyaluminum chloride was prepared by the following method:

[0053] A1. Take 100g of polyaluminum chloride, add 5g of boron nitride nanoparticles with a particle size of 80nm, put them into an ultrasonic disperser, adjust the ultrasonic power to 400W, and ultrasonically disperse for 50min to obtain a uniformly dispersed polyaluminum chloride substrate.

[0054] A2. Take 25g of silane coupling agent KH-792, 5g of L-tartaric acid and 40g of deionized water in a mass ratio of 5:1:8, add them to a three-necked flask, place it in a constant temperature water bath, adjust the temperature to 50℃, stir the reaction at a constant temperature for 60min, and cool to room temperature after the reaction is completed to obtain a low temperature modifier.

[0055] A3. Take 100g of the above-mentioned polyaluminum chloride substrate, add 12g of low-temperature modifier, adjust the pH of the system to 4.2 with dilute hydrochloric acid, place it in a constant temperature water bath, adjust the temperature to 42℃, stir and react at a constant temperature for 100min. After the reaction is completed, put the product into a vacuum drying oven and vacuum dry it for 3h under the conditions of vacuum degree -0.08MPa and temperature 70℃. After drying, pulverize it to 100 mesh with a pulverizer to obtain modified polyaluminum chloride.

[0056] Example of preparation of low-temperature flocculant

[0057] Preparation Example 4

[0058] The low-temperature flocculant was prepared using the following method:

[0059] Take 100g of polyacrylamide, add it to the reaction vessel, add an appropriate amount of deionized water and stir to dissolve, then add 6g of 2-acrylamide-2-methylpropanesulfonic acid, stir evenly, add 0.8g of initiator (ammonium persulfate and sodium bisulfite in a mass ratio of 2:1), adjust the temperature of the reaction vessel to 25℃, and carry out the constant temperature polymerization reaction for 120min. After the reaction is completed, put the product into a constant temperature drying oven and dry it at 50℃ for 3h. After drying, pulverize it to 100 mesh to obtain a low temperature flocculant.

[0060] Preparation Example 5

[0061] The low-temperature flocculant was prepared using the following method:

[0062] Take 100g of polyacrylamide, add it to the reaction vessel, add an appropriate amount of deionized water and stir to dissolve, then add 7g of 2-acrylamide-2-methylpropanesulfonic acid, stir evenly, add 1.0g of initiator (ammonium persulfate and sodium bisulfite in a mass ratio of 2.5:1), adjust the temperature of the reaction vessel to 28℃, and carry out the constant temperature polymerization reaction for 120min. After the reaction is completed, put the product into a constant temperature drying oven and dry it at 55℃ for 3.5h. After drying, pulverize it to 110 mesh to obtain a low temperature flocculant.

[0063] Preparation Example 6

[0064] The low-temperature flocculant was prepared using the following method:

[0065] Take 100g of polyacrylamide, add it to the reaction vessel, add an appropriate amount of deionized water and stir to dissolve, then add 8g of 2-acrylamide-2-methylpropanesulfonic acid, stir evenly, add 1.2g of initiator (ammonium persulfate and sodium bisulfite in a mass ratio of 3:1), adjust the temperature of the reaction vessel to 30℃, and carry out the constant temperature polymerization reaction for 120min. After the reaction is completed, put the product into a constant temperature drying oven and dry it at 60℃ for 4h. After drying, pulverize it to 100 mesh to obtain a low temperature flocculant.

[0066] Example

[0067] Example 1

[0068] A wastewater treatment agent, the raw material components and dosages of which are shown in Table 1, wherein the modified polyaluminum chloride is selected from the modified polyaluminum chloride prepared in Preparation Example 1; and the low-temperature flocculant is selected from the low-temperature flocculant prepared in Preparation Example 4.

[0069] A wastewater treatment agent, the preparation method of which is as follows:

[0070] S1. Add modified polyaluminum chloride, polyferric sulfate, zinc sulfate, and calcium silicate to deionized water. The amount of deionized water added is 1.2 times the total mass of the above four raw materials. Stir at 30℃ and 100r / min for 30min until completely dissolved to obtain a mixed salt solution.

[0071] S2. Add sodium lignosulfonate, chitosan and borax to the mixed salt solution obtained in step S1 in sequence, adjust the stirring speed to 150 r / min, continue stirring for 20 min, slowly add sodium carbonate during the process, adjust the pH of the system to 6.5, and form a uniform suspension.

[0072] S3. Add a low-temperature flocculant to the suspension obtained in step S2, reduce the stirring speed to 80 r / min, stir for 40 min, add hydrogen peroxide, continue stirring for 10 min, let stand for 15 min, and obtain the wastewater treatment agent.

[0073] Example 2

[0074] A wastewater treatment agent, the raw material components and dosages of which are shown in Table 1, wherein the modified polyaluminum chloride is selected from the modified polyaluminum chloride prepared in Preparation Example 2; and the low-temperature flocculant is selected from the low-temperature flocculant prepared in Preparation Example 4.

[0075] A wastewater treatment agent, the preparation method of which is as follows:

[0076] S1. Add modified polyaluminum chloride, polyferric sulfate, zinc sulfate, and calcium silicate to deionized water. The amount of deionized water added is 1.4 times the total mass of the above four raw materials. Stir at 32℃ and 110r / min for 35min until completely dissolved to obtain a mixed salt solution.

[0077] S2. Add sodium lignosulfonate, chitosan and borax to the mixed salt solution obtained in step S1 in sequence, adjust the stirring speed to 165 r / min, continue stirring for 25 min, slowly add sodium carbonate during the process, adjust the pH of the system to 7.0, and form a uniform suspension.

[0078] S3. Add a low-temperature flocculant to the suspension obtained in step S2, reduce the stirring speed to 90 r / min, stir for 45 min, add hydrogen peroxide, continue stirring for 12 min, let stand for 18 min, and obtain the wastewater treatment agent.

[0079] Example 3

[0080] A wastewater treatment agent, the raw material components and dosages of which are shown in Table 1, wherein the modified polyaluminum chloride is selected from the modified polyaluminum chloride prepared in Preparation Example 3; and the low-temperature flocculant is selected from the low-temperature flocculant prepared in Preparation Example 4.

[0081] A wastewater treatment agent, the preparation method of which is as follows:

[0082] S1. Add modified polyaluminum chloride, polyferric sulfate, zinc sulfate, and calcium silicate to deionized water. The amount of deionized water added is 1.5 times the total mass of the above four raw materials. Stir at 35℃ and 120r / min for 40min until completely dissolved to obtain a mixed salt solution.

[0083] S2. Add sodium lignosulfonate, chitosan and borax to the mixed salt solution obtained in step S1 in sequence, adjust the stirring speed to 180 r / min, continue stirring for 30 min, slowly add sodium carbonate during the process, adjust the pH of the system to 7.5, and form a uniform suspension.

[0084] S3. Add a low-temperature flocculant to the suspension obtained in step S2, reduce the stirring speed to 100 r / min, stir for 50 min, add hydrogen peroxide, continue stirring for 15 min, let stand for 20 min, and obtain the wastewater treatment agent.

[0085] Table 1. Raw material components and proportions (g) of the treatment agents in Examples 1-3

[0086]

[0087] Example 4

[0088] A wastewater treatment agent, which differs from Example 2 in that the low-temperature flocculant in this example is the low-temperature flocculant prepared in Preparation Example 5.

[0089] Example 6

[0090] A wastewater treatment agent, which differs from Example 2 in that the low-temperature flocculant in this example is the low-temperature flocculant prepared in Preparation Example 6.

[0091] Comparative Example

[0092] Comparative Example 1

[0093] A wastewater treatment agent, which differs from Example 2 in that an equal amount of ordinary unmodified polyaluminum chloride is used instead of modified polyaluminum chloride in this comparative example.

[0094] Comparative Example 2

[0095] A wastewater treatment agent, which differs from Example 2 in that an equal amount of ordinary polyacrylamide is used instead of the low-temperature flocculant in this comparative example.

[0096] Comparative Example 3

[0097] A wastewater treatment agent, which differs from Example 2, is provided in that an equal amount of ordinary unmodified polyaluminum chloride is used instead of modified polyaluminum chloride, and an equal amount of ordinary polyacrylamide is used instead of low-temperature flocculant.

[0098] Comparative Example 4

[0099] A wastewater treatment agent, differing from Example 2 in that the modified polyaluminum chloride only undergoes nano-boron nitride doping modification, without the addition of a low-temperature modifier (KH-792 and L-tartaric acid composite system). Its preparation method is as follows:

[0100] Take 100g of polyaluminum chloride, add 4g of boron nitride nanoparticles with a particle size of 65nm, put them into an ultrasonic disperser, adjust the ultrasonic power to 350W, and ultrasonically disperse for 40min to obtain polyaluminum chloride substrate; vacuum dry the substrate under vacuum conditions of -0.07MPa and 65℃ for 2.5h, and after drying, pulverize it to 90 mesh to obtain single-doped modified polyaluminum chloride.

[0101] The low-temperature flocculant used is still the low-temperature flocculant prepared in Preparation Example 5.

[0102] Comparative Example 5

[0103] A wastewater treatment agent, which differs from Example 2 in that sodium lignosulfonate and chitosan were not added to the raw materials of this comparative example.

[0104] Performance testing

[0105] 1. Low-temperature hydrolysis rate detection

[0106] The wastewater treatment agents prepared in each example and comparative example were added to 1000 mL of simulated low-temperature domestic wastewater (temperature controlled at 2℃, COD=280 mg / L, ammonia nitrogen=32 mg / L, total phosphorus=6.5 mg / L) at a dosage of 230 mg / L. After addition, the mixture was stirred at 200 r / min, and samples were taken at 5 min, 10 min, 15 min, 20 min, and 25 min to detect Al content. 3+ The concentration (using EDTA titration); with Al 3+ The time it takes for the concentration to reach a stable value (hydrolysis complete) is used as the evaluation standard for the hydrolysis rate. The shorter the time, the faster the hydrolysis rate and the stronger the low-temperature activity.

[0107] 2. Pollutant removal rate testing

[0108] After treatment under the same conditions as described above (dosage 230 mg / L, stirring at 200 rpm for 28 min, stirring at 55 rpm for 12 min, and settling for 55 min), the supernatant was collected, and the concentrations of COD, ammonia nitrogen, and total phosphorus were measured. COD was measured using the potassium dichromate titration method (GB11914-89), ammonia nitrogen was measured using Nessler's reagent spectrophotometry (HJ535-2009), and total phosphorus was measured using the ammonium molybdate spectrophotometry method (GB11893-89). The removal rate was calculated as follows: removal rate = (initial concentration - post-treatment concentration) / initial concentration × 100%. The higher the removal rate, the better the purification effect.

[0109] 3. Low-temperature stability testing

[0110] The wastewater treatment agents prepared in each embodiment and comparative example were sealed and stored in a constant temperature environment of 2°C for 72 hours. After storage, the appearance of the agent was observed (whether agglomeration or stratification occurred). At the same time, the COD and total phosphorus removal rates of the agent after storage were tested according to the above pollutant removal rate test method. The removal rate was compared with the removal rate before storage, and the removal rate decay rate was calculated. The decay rate = (removal rate before storage - removal rate after storage) / removal rate before storage × 100%. The lower the decay rate, the better the low temperature stability.

[0111] II. Test Data

[0112] All tests were repeated 3 times, and the average value was taken as the final test result. The specific data are shown in Table 2 below (simulated domestic sewage initial indicators: COD=280mg / L, ammonia nitrogen=32mg / L, total phosphorus=6.5mg / L, test temperature 2℃).

[0113] Table 2 Detection Results

[0114]

[0115] As shown in Table 2, the low-temperature hydrolysis rate data directly reflects the low-temperature activity of the modified polyaluminum chloride. The hydrolysis completion time of Examples 1-4 and 6 is 14-18 min, significantly shorter than that of the comparative examples. Among them, Example 4 has the shortest hydrolysis completion time (14 min), which is attributed to the synergistic effect of the modified polyaluminum chloride (dual modification with nano boron nitride doping + KH-792 and L-tartaric acid composite modifier) ​​prepared using intermediate parameters and the low-temperature flocculant. The dual modification strategy significantly reduces the hydrolysis activation energy of polyaluminum chloride and accelerates the hydrolysis of Al. 3+ The release of the components was observed. The hydrolysis completion times of Comparative Example 1 (ordinary unmodified polyaluminum chloride) and Comparative Example 3 (dual unmodified core components) were as long as 38 min and 45 min, respectively. Due to the lack of the modification scheme of this application, the hydrolysis activity of traditional polyaluminum chloride was greatly reduced at a low temperature of 2℃, and the reaction rate was slow. The hydrolysis time of Comparative Example 4 (single nano-doped modification) was 28 min, which was better than the unmodified group, but it lacked the synergistic effect of the composite modifier, and the hydrolysis rate was still far lower than that of the examples. This confirms the necessity of the dual strategy of "nano-doping + composite modification" of this application.

[0116] The pollutant removal rate data (COD, ammonia nitrogen, total phosphorus) fully demonstrate the low-temperature purification advantages of the technical solution of this application. The removal rates of each item in the examples are all above 85%. The COD, ammonia nitrogen, and total phosphorus removal rates of Example 4 reach 93.2%, 90.5%, and 95.6%, respectively, which are much higher than those of the comparison examples. The core reason lies in the synergistic effect between the modified polyaluminum chloride and the low-temperature flocculant in the examples: the modified polyaluminum chloride rapidly hydrolyzes to achieve charge neutralization, promoting the initial aggregation of pollutants, while the low-temperature flocculant (polyacrylamide and AMPS copolymer) keeps the molecular chains extended, agglomerating the tiny flocs into dense flocs through adsorption bridging, thus accelerating solid-liquid separation; Comparative Examples 1 and 2, due to the lack of a single core modified component, showed a significant decrease in removal rate (62.8%-73.8%), while Comparative Example 3, due to the lack of two core modified components, had the lowest removal rate (50.3%-61.2%), highlighting the synergistic effect of the two core modified components; Comparative Example 5, due to the lack of sodium lignosulfonate and chitosan, had insufficient floc stability, and its pollutant removal rate (76.2%-83.7%) was lower than that of the examples, confirming the enhancing effect of the auxiliary components on the purification effect.

[0117] The low-temperature stability data reflects the practical feasibility of the wastewater treatment agent. The removal rate attenuation rate after 72 hours of low-temperature storage in the examples was only 1.5%-2.1%, with no aggregation or stratification. This indicates that the components of this application are rationally matched, and the interaction between the modified polyaluminum chloride, the low-temperature flocculant, and the auxiliary components effectively improves the dispersibility and stability of the agent, preventing activity decline during low-temperature storage. The attenuation rates of all comparative examples were significantly higher, with Comparative Example 3 showing the highest attenuation rate (12.3%). This is because the core component was not modified, resulting in weak intermolecular forces and easy aggregation and activity loss at low temperatures. The attenuation rates of Comparative Examples 1, 2, 4, and 5 ranged from 5.6% to 8.7%, all due to the lack of the modification strategy or auxiliary components described in this application, preventing the formation of a stable system structure. This further confirms the innovative advantages of the technical solution in low-temperature stability of this application.

[0118] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 wastewater treatment agent, characterized in that, Raw materials including the following components: Modified polyaluminum chloride 35-45 parts, low-temperature flocculant 10-15 parts, sodium lignosulfonate 2-4 parts, polyferric sulfate 8-12 parts, zinc sulfate 3-5 parts, sodium carbonate 1-2 parts, calcium silicate 2-3 parts, chitosan 1-3 parts, borax 0.5-1.5 parts, hydrogen peroxide 1-2 parts; The modified polyaluminum chloride is obtained by modifying polyaluminum chloride with nano-boron nitride doping and a low-temperature modifier; The low-temperature flocculant is obtained by copolymerizing polyacrylamide with the low-temperature active monomer 2-acrylamide-2-methylpropanesulfonic acid.

2. The wastewater treatment agent according to claim 1, characterized in that, The modified polyaluminum chloride was prepared by the following method: A1. Mix polyaluminum chloride and nano boron nitride, and ultrasonically disperse at 300-400W for 30-50 minutes to obtain polyaluminum chloride substrate; A2. Mix silane coupling agent KH-792, L-tartaric acid and deionized water, stir at 40-50℃ for 40-60 min, cool to room temperature to obtain low temperature modifier; A3. Add the low-temperature modifier to the polyaluminum chloride substrate, adjust the pH of the system to 3.8-4.2, and stir the reaction at a constant temperature of 38-42℃ for 90-100 min. After the reaction is completed, vacuum dry and pulverize to obtain modified polyaluminum chloride.

3. The wastewater treatment agent according to claim 2, characterized in that, In step A1, the boron nitride nanoparticles have a particle size of 50-80 nm, and the amount of boron nitride nanoparticles added is 3%-5% of the mass of polyaluminum chloride.

4. The wastewater treatment agent according to claim 2, characterized in that, In step A2, the mass ratio of silane coupling agent KH-792, L-tartaric acid and deionized water is (3-5):1:(6-8).

5. A wastewater treatment agent according to claim 2, characterized in that, In step A3, the amount of low-temperature modifier added is 10%-12% of the mass of the polyaluminum chloride substrate.

6. The wastewater treatment agent according to claim 1, characterized in that, The low-temperature flocculant was prepared using the following method: Using polyacrylamide as a base material, 6%-8% of its low-temperature active monomer 2-acrylamide-2-methylpropanesulfonic acid is added. After adding an initiator, the polymerization reaction is carried out at 25-30℃ for 120 minutes. After drying, a low-temperature flocculant is obtained.

7. The wastewater treatment agent according to claim 6, characterized in that: The initiator is ammonium persulfate and sodium bisulfite in a mass ratio of (2-3):1, and the amount of the initiator added is 0.8%-1.2% of the polyacrylamide.

8. A method for preparing a wastewater treatment agent according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Add modified polyaluminum chloride, polyferric sulfate, zinc sulfate, and calcium silicate to deionized water. The amount of deionized water added is 1.2-1.5 times the total mass of the above four raw materials. Stir at 30-35℃ and 100-120r / min for 30-40 minutes until completely dissolved to obtain a mixed salt solution. S2. Add sodium lignosulfonate, chitosan, and borax to the mixed salt solution obtained in step S1 in sequence. Adjust the stirring speed to 150-180 r / min and continue stirring for 20-30 min. During this period, slowly add sodium carbonate and adjust the pH of the system to 6.5-7.5 to form a uniform suspension. S3. Add a low-temperature flocculant to the suspension obtained in step S2, reduce the stirring speed to 80-100 r / min, stir for 40-50 min, add hydrogen peroxide, continue stirring for 10-15 min, let stand for 15-20 min, and obtain the wastewater treatment agent.

9. The application of a wastewater treatment agent as described in any one of claims 1-7, characterized in that: The wastewater treatment agent is used for treating domestic wastewater in a low-temperature environment of 0-5℃. The dosage of the wastewater treatment agent is 180-280 mg / L. After addition, the agent is stirred at 200-220 r / min for 25-30 min, then stirred at 50-60 r / min for 10-15 min, and allowed to settle for 50-60 min to achieve efficient removal of pollutants from wastewater.

Images