Low-temperature-resistant polyacrylamide flocculant suitable for low-temperature water body and preparation method of low-temperature-resistant polyacrylamide flocculant

Abstract

The invention discloses a low-temperature-resistant polyacrylamide flocculant suitable for a low-temperature water body and a preparation method of the low-temperature-resistant polyacrylamide flocculant. The flocculant is prepared from the following raw materials in parts by weight: 60 to 85 parts of acrylamide (AM), 15 to 40 parts of low-temperature-resistant functional monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 0.5 to 5 parts of hydrophobic modified monomer, 0.1 to 1.0 part of molecular chain regulator, 0.01 to 0.1 part of initiator, 120 to 200 parts of deionized water and 1 to 5 parts of post-added antifreezing agent. The product is prepared by an aqueous solution polymerization method. According to the invention, by introducing the rigid sulfonic monomer and the functional monomer with large steric hindrance and compounding the specific antifreezing agent, the extensibility and diffusion performance of a polymer molecular chain in low-temperature (less than or equal to 10 DEG C) water are remarkably improved, so that large and dense flocs can be quickly formed under the low-temperature condition, and an excellent flocculating settling effect is kept.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a flocculant and its preparation method, specifically a modified polyacrylamide flocculant and its preparation method that can maintain high flocculation performance under low temperature (≤10℃) conditions. Background Technology

[0002] Polyacrylamide (PAM), as a highly efficient flocculant, is widely used in drinking water, industrial wastewater, and municipal sewage treatment. Its flocculation mechanism mainly relies on the adsorption bridging and charge neutralization of its long molecular chains. However, under low-temperature conditions (especially in winter or cold regions), the flocculation efficiency of traditional PAM decreases sharply. The main reason is: 1. Increased viscosity and slower diffusion: Lower water temperature leads to increased water viscosity, which significantly slows down the diffusion and extension of PAM molecular chains in water, making it difficult for them to quickly collide and come into contact with colloidal particles.

[0003] 2. Molecular chain coiling: At low temperatures, the thermal motion of polymer chains weakens, and the molecular chains tend to coil, shortening their effective chain length and severely weakening their adsorption and bridging ability.

[0004] 3. Decreased degree of hydrolysis: For partially hydrolyzed polyacrylamide (HPAM), low temperature will inhibit the hydrolysis reaction of its amide groups, affecting its final electrical properties.

[0005] 4. Difficulty in floc formation: The above factors together slow down the flocculation kinetics process, resulting in small, loose flocs with extremely poor settling performance.

[0006] Currently, most methods for solving the low-temperature flocculation problem focus on optimizing the dosing process or compounding other agents, such as increasing the dosage or adding coagulant aids (e.g., clay). However, these methods are costly, have limited effectiveness, and may introduce secondary pollution. Developing intrinsically low-temperature resistant PAM flocculants through molecular design, starting from the polymer structure itself, is the fundamental way to solve this industry problem. Summary of the Invention

[0007] The purpose of this invention is to provide a low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies and its preparation method, solving the technical problem that the flocculation efficiency of traditional PAM will decrease sharply under low-temperature conditions. To achieve the above objective, according to one aspect of the invention, a low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies is provided, comprising, by weight, 60-85 parts of acrylamide (AM), 15-40 parts of the low-temperature resistant functional monomer 2-acrylamido-2-methylpropanesulfonic acid (AMPS), 0.5-5 parts of a hydrophobic modified monomer, 0.1-1.0 parts of a molecular chain regulator, 0.01-0.1 parts of an initiator, 120-200 parts of deionized water, and 1-5 parts of an antifreeze agent added later.

[0008] Furthermore, the hydrophobic modifying monomer is methyl methacrylate (MMA) or styrene (St).

[0009] Furthermore, the molecular chain regulator is isopropanol.

[0010] Furthermore, the initiator is ammonium persulfate-tetramethylethylenediamine.

[0011] Furthermore, the added antifreeze is ethylene glycol or glycerol.

[0012] According to another aspect of the present invention, a method for preparing the above-described low-temperature resistant polyacrylamide flocculant suitable for low-temperature water is provided, comprising: Step 1: Add deionized water to the reactor and control the temperature at 10-20℃. Then add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and hydrophobic modified monomer in sequence and stir until completely dissolved. Then add the molecular chain regulator and stir evenly. Step 2: Maintain the system temperature at 15±5℃, add an initiator to react and obtain a viscous gel polymer; Step 3: Granulate the obtained gel polymer and wash it to remove residual monomers and moisture; Step four: Dry the washed granules to constant weight, pulverize them, and then mix them thoroughly with the added antifreeze to obtain the product.

[0013] Furthermore, in step one, after adding deionized water to the reactor, stirring is started and nitrogen gas is introduced to remove oxygen.

[0014] Furthermore, in step two, the reaction time after adding the initiator is 4-8 hours.

[0015] Furthermore, in step three, wash with ethanol 2-3 times.

[0016] Furthermore, in step four, the granules are vacuum dried at 55-65°C to constant weight.

[0017] The low-temperature resistant polyacrylamide flocculant provided by this invention significantly improves the extensibility and diffusion properties of polymer molecular chains in low-temperature (≤10℃) water by introducing rigid sulfonic acid monomers and functional monomers with large steric hindrance, and compounding with specific antifreeze agents. As a result, it can quickly form large and dense flocs under low-temperature conditions and maintain excellent flocculation and sedimentation effects.

[0018] The flocculant obtained by this invention is particularly suitable for drinking water treatment in winter, industrial wastewater treatment in cold northern regions, and sludge dewatering in low-temperature biochemical systems. Detailed Implementation

[0019] A typical embodiment of the present invention provides a low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies. By mass, its raw materials include 60-85 parts of acrylamide (AM), 15-40 parts of the low-temperature resistant functional monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 0.5-5 parts of hydrophobic modified monomer, 0.1-1.0 parts of molecular chain regulator, 0.01-0.1 parts of initiator, 120-200 parts of deionized water, and 1-5 parts of antifreeze added later.

[0020] The above raw materials were used to prepare the product via aqueous solution polymerization.

[0021] Preferably, the hydrophobic modifying monomer is methyl methacrylate (MMA) or styrene (St), the molecular chain regulator is isopropanol, and the added antifreeze is ethylene glycol or glycerol.

[0022] The initiator is preferably a redox initiation system with high low-temperature activity, such as ammonium persulfate-tetramethylethylenediamine.

[0023] The introduced low-temperature resistant functional monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS) has a highly hydrating sulfonic acid group (-SO3H). This group has a strong hydration capacity and is not easily dehydrated at low temperatures. It can effectively destroy the ice crystal structure between water molecules and provide a strong hydration film for the polymer chain, forcing the molecular chain to remain in an extended state at low temperatures and fully exert its adsorption bridging effect, thereby giving the product of this invention excellent low-temperature resistance.

[0024] AMPS monomers themselves have large side groups, which can increase the rigidity of the molecular chain; the benzene ring structure of the hydrophobic monomer styrene (St) also has extremely high rigidity. The introduction of these rigid segments effectively suppresses the tendency of molecular chains to curl up at low temperatures and maintains the effective chain length of the polymer.

[0025] Because of its well-extended molecular chains, it can quickly interact with colloidal particles to form large and dense flocs, with a sedimentation rate much faster than that of ordinary PAM at low temperatures.

[0026] Furthermore, this invention employs a dual low-temperature resistance strategy of "intramolecular modification" and "extramolecular compounding." It not only enhances low-temperature resistance at the molecular structure level through copolymerization modification but also incorporates small-molecule antifreeze agents during post-processing. These small molecules preferentially bind to water molecules, further lowering the system's freezing point, improving water flowability, and creating a better low-temperature environment for the PAM macromolecules to function, resulting in a synergistic effect.

[0027] Another typical embodiment of the present invention provides a method for preparing the low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies as described above.

[0028] Step 1: Preparation of monomer solution Add deionized water to the reactor, start stirring and introduce nitrogen gas to remove oxygen.

[0029] Then control the temperature at 10-20℃, for example, 15℃, 16℃, 17℃, 18℃, 19℃, and 20℃. Then add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and hydrophobic modified monomer in sequence, and stir until completely dissolved; then add the molecular chain regulator and stir evenly.

[0030] Step 2, Low-temperature polymerization reaction The system temperature was maintained at 15±5℃, and an initiator was added to react and a viscous gel polymer was obtained.

[0031] Preferably, the reaction time after adding the initiator is 4-8 hours.

[0032] Step 3: Granulation and alcohol washing The obtained gel polymer was granulated and washed with ethanol 2-3 times to remove residual monomers and moisture.

[0033] Step 4, Drying and Compounding The washed granules were vacuum dried at 55-65℃ to constant weight, pulverized, and then thoroughly mixed with the subsequently added antifreeze to obtain the product.

[0034] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation schemes of this invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art. Example 1

[0035] Add 1500g of deionized water to the reactor, start stirring and introduce nitrogen gas to remove oxygen.

[0036] Add 750g acrylamide (AM), 250g 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 20g methyl methacrylate (MMA) sequentially, and stir to dissolve at 15°C. Add 5g isopropanol and stir until completely dissolved.

[0037] Maintaining the temperature at 15℃, 0.5g of ammonium persulfate and 0.3g of tetramethylethylenediamine were added, and the reaction was carried out for 6 hours to obtain a viscous, transparent gel-like polymer.

[0038] The gel polymer was granulated using a granulator and washed three times with ethanol.

[0039] The washed granules were vacuum dried at 60°C to constant weight. After pulverization, they were thoroughly mixed with 30g of ethylene glycol to obtain the low-temperature resistant flocculant product L1. Example 2

[0040] Add 1200g of deionized water to the reactor, start stirring and purge with nitrogen to remove oxygen.

[0041] Add 600g acrylamide (AM), 150g 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 5g methyl methacrylate (MMA) sequentially, and stir to dissolve at 10°C. Add 1g isopropanol and stir until completely dissolved.

[0042] Maintaining the temperature at 10℃, add 0.06g ammonium persulfate and 0.04g tetramethylethylenediamine, and react for 4 hours to obtain a viscous, transparent gel-like polymer.

[0043] The gel polymer was granulated using a granulator and washed three times with ethanol.

[0044] The washed granules were vacuum dried at 65°C to constant weight. After pulverization, they were thoroughly mixed with 10g of glycerol to obtain the low-temperature anti-flocculation agent product L2. Example 3

[0045] Add 2000g of deionized water to the reactor, start stirring and introduce nitrogen gas to remove oxygen.

[0046] Add 850g acrylamide (AM), 400g 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and 50g styrene (St) sequentially, and stir to dissolve at 20°C. Add 10g isopropanol and stir until completely dissolved.

[0047] Maintaining the temperature at 20℃, 0.5g of ammonium persulfate and 0.5g of tetramethylethylenediamine were added, and the reaction was carried out for 8 hours to obtain a viscous, transparent gel-like polymer.

[0048] The gel polymer was granulated using a granulator and washed twice with ethanol.

[0049] The washed granules were vacuum dried at 55°C to constant weight. After pulverization, they were thoroughly mixed with 50g of ethylene glycol to obtain the low-temperature resistant flocculant product L3.

[0050] Comparative Example 1 Ordinary cationic polyacrylamide (CPAM, molecular weight approximately 9 million, ionicity 40%) was used as a comparative example, D-CPAM.

[0051] Application effect test: A kaolin suspension was prepared to simulate high-turbidity wastewater (initial turbidity ≈ 100 NTU), and the water sample temperature was controlled at 5℃. 0.1 g of comparative example 1D-CPAM and example product L1 were weighed and prepared into 0.1% solutions. 1.0 mL of flocculant solution (dosage 2 mg / L) was added to each 500 mL low-temperature water sample. The mixture was first stirred rapidly at 200 rpm for 1 minute, then slowly stirred at 50 rpm for 5 minutes. After standing for 10 minutes, the supernatant was collected to determine the residual turbidity.

[0052]

[0053] Test results show that, at a low temperature of 5℃, the performance of the low-temperature resistant flocculant L1 prepared in this invention is significantly better than that of ordinary commercial CPAM, with an extremely high turbidity removal rate, which fully demonstrates its excellent low-temperature flocculation performance.

[0054] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies, characterized in that: By mass, the raw materials include 60-85 parts of acrylamide (AM), 15-40 parts of low-temperature resistant functional monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS), 0.5-5 parts of hydrophobic modified monomer, 0.1-1.0 parts of molecular chain regulator, 0.01-0.1 parts of initiator, 120-200 parts of deionized water, and 1-5 parts of antifreeze added later.

2. The low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies according to claim 1, characterized in that: The hydrophobic modifying monomer is methyl methacrylate (MMA) or styrene (St).

3. The low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies according to claim 1 or 2, characterized in that: The molecular chain regulator is isopropanol.

4. The low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies according to claim 3, characterized in that: The initiator is ammonium persulfate-tetramethylethylenediamine.

5. The low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies according to claim 4, characterized in that: The added antifreeze is ethylene glycol or glycerol.

6. The method for preparing the low-temperature resistant polyacrylamide flocculant suitable for low-temperature water bodies according to any one of claims 1-5, characterized in that, include: Step 1: Add deionized water to the reactor and control the temperature at 10-20℃. Then add acrylamide, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and hydrophobic modified monomer in sequence and stir until completely dissolved. Then add the molecular chain regulator and stir evenly. Step 2: Maintain the system temperature at 15±5℃, add an initiator to react and obtain a viscous gel polymer; Step 3: Granulate the obtained gel polymer and wash it to remove residual monomers and moisture; Step four: Dry the washed granules to constant weight, pulverize them, and then mix them thoroughly with the added antifreeze to obtain the product.

7. The method according to claim 6, characterized in that: In step one, after adding deionized water to the reactor, stirring is started and nitrogen gas is introduced to remove oxygen.

8. The method according to claim 6 or 7, characterized in that: In step two, the reaction time after adding the initiator is 4-8 hours.

9. The method according to claim 8, characterized in that: In step three, wash with ethanol 2-3 times.

10. The method according to claim 9, characterized in that: In step four, the granules are vacuum dried at 55-65℃ to constant weight.

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