Preparation method of washed sand flocculant

Abstract

The invention discloses a preparation method of a washed sand flocculant, and mainly relates to the field of flocculants. Comprising the following steps: S1, adding water, acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid into a reaction kettle, uniformly stirring and mixing, and adding sodium hydroxide to adjust the pH value to 8-10; s2, sequentially adding a cationic monomer, a cross-linking agent and a chain transfer agent into the solution in the step S1, uniformly mixing, adding an initiator and a reducing agent, stirring for 5 minutes, and standing for 5 hours to obtain a gelatinous liquid flocculant; s3, shearing and granulating the liquid flocculant obtained in the step S2, drying at 120 DEG C, and crushing to obtain a powder flocculant; the invention has the following beneficial effects: on the premise of ensuring good flocculation performance, the residual flocculant in the later period has small or even no influence on concrete performance, and powerful guarantee is provided for wide application of washed sand and construction of concrete for various projects.

Description

Technical Field

[0001] The invention relates to the field of flocculants, in particular to a method for preparing a water-washed sand flocculant. Background Art

[0003] Sand washing plants produce a large amount of sewage in daily production, which contains a large amount of sediment, colloids and suspended particles. In order to meet environmental protection requirements and efficiently recycle production water, sand washing plants generally use flocculants to treat sewage.

[0004] Polyacrylamide is generally used as a flocculant. The principle is to use the polar groups in its molecules to adsorb solid particles suspended in water. The particle bridge connection of the polymer chain and the polar charge neutralize the charge on the surface of the suspended particles, so that the particles form aggregates and settle quickly. Polyacrylamide is a linear polymer. When used as a water treatment flocculant, the molecular weight is generally between 7 and 15 million. A certain amount of polyacrylamide will remain in the sand washing water and the water-washed sand, and the residual amount is uncontrollable. According to relevant literature, polyacrylamide solution is basically stable at room temperature and decomposes very slowly. Therefore, in later applications, it will have a serious impact on the performance of concrete mixtures, causing the dispersion and retention of concrete to decrease, and the strength cannot be guaranteed, which brings great trouble to the production of downstream concrete companies. Generally, they can only passively increase the dosage of water reducers and slump retainers. In addition, when problems occur at the construction site, water reducers or thickeners need to be added for a second time, making it difficult to stabilize the quality of concrete. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a water-washed sand flocculant, which, under the premise of ensuring good flocculation performance, can achieve that the residual flocculant in the later stage has little or no effect on the performance of concrete, thereby providing a strong guarantee for the wide application of water-washed sand and the construction of concrete for various projects.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for preparing a water-washed sand flocculant comprises the following steps:

[0008] S1. Add water, acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid to the reactor, stir and mix well, and then add sodium hydroxide to adjust the pH to 8 to 10;

[0009] S2. Add cationic monomer, crosslinking agent and chain transfer agent to the solution of step S1 in sequence, mix well, add initiator and reducing agent, stir for 5 minutes and let stand for 5 hours to obtain a gel-like liquid flocculant;

[0010] S3. The liquid flocculant obtained in step S2 is sheared and granulated, dried at 120°C and crushed to obtain a powder flocculant;

[0011] Among them, the molar ratio of each raw material is: acrylic acid: acrylamide: 2-acrylamide-2-methylpropane sulfonic acid: cationic monomer: cross-linking agent = 1: (1-5): (0.1-0.5): (0.1-0.5): (0.03-0.1); the mass ratio of chain transfer agent, initiator and reducing agent to the total monomer is: (0.001-0.003): (0.001-0.003): (0.0005-0.001).

[0012] Furthermore, the cationic monomer includes at least one of methacryloyloxyethyltrimethylammonium chloride or dimethyldiallylammonium chloride.

[0013] Furthermore, the cross-linking agent includes at least one of ethylene glycol dimethacrylate or ethylene glycol diacrylate.

[0014] Furthermore, the initiator includes at least one of hydrogen peroxide, ammonium persulfate or potassium persulfate.

[0015] Furthermore, the reducing agent includes at least one of VC, bleaching powder or sodium hypophosphite.

[0016] Furthermore, the chain transfer agent includes at least one of mercaptoethanol, mercaptopropionic acid or thioglycolic acid.

[0017] Furthermore, the molecular structure of the prepared flocculant is:

[0018]

[0019] A liquid flocculant is prepared by the method, and the liquid flocculant is in gel form.

[0020] A powder flocculant is prepared by the method through shearing granulation, drying and pulverization.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The flocculant of the present invention is copolymerized by cationic monomers and anionic monomers to form amphoteric polymers. The molecular structure contains amide groups, carboxyl groups, sulfonic acid groups, etc., which can accelerate the rapid sedimentation of suspended matter in sand washing water;

[0023] 2. Compared with the ultra-long linear structure of commonly used polyacrylamide flocculants, the flocculant of the present invention adds a certain amount of chain transfer agent to control the molecular weight of linear copolymers such as acrylamide and acrylic acid, and at the same time, adds a certain amount of cross-linking agent to link such relatively small molecular weight linear chains. The overall result is that through the linking of the cross-linking agent, a high molecular weight polymer with flocculation function similar to that of polyacrylamide is still synthesized. At the same time, because the structure can contain a small amount of double cross-linked polymers, that is, a three-dimensional network structure, more colloidal particles and suspended matter in the water can be captured and swept up in the flocculation sedimentation process than flocculants such as polyacrylamide, and the flocculation efficiency is higher;

[0024] 3. The present invention introduces a cross-linking agent into the comonomer to form a local micro-cross-linking structure, so that the flocculant has the molecular weight required for the flocculation structure. At the same time, after the sand washing is completed, the residual flocculant in the sand washing water and the water-washed sand will be hydrolyzed into a small molecular linear polymer during the storage process due to the hydrolysis of the ester group in the cross-linking agent, so that it loses the flocculation function of the flocculant. At the same time, the hydrophilic groups such as the carboxyl group and the sulfonic acid group of the side chain of the small molecular linear polymer together with the lipophilic main chain constitute a small molecule surfactant with certain wetting and anti-mud sacrificial functions, which can provide auxiliary effects on the dispersion and dispersion retention of concrete, thereby achieving the purpose of minimizing the impact on the state and strength of the concrete mixture during the application of sand washing water and water-washed sand in concrete;

[0025] 4. The ester crosslinking agent introduced into the flocculant of the present invention is the key core of the present invention to meet the requirements of sand washing flocculation while not affecting the later use in concrete;

[0026] 5. The flocculant synthesis process of the present invention is simple, it is a room temperature reaction, no external heat source is required, the energy consumption is low, the production equipment is simple, and the investment is small;

[0027] 6. The present invention can produce two products, liquid and powder. The liquid product has the advantages of easy use, small equipment investment and high cost performance for the sand washing plants of surrounding customers; the powder product is suitable for long-distance transportation and storage, which is beneficial to the promotion and application of various sand washing plants and the quality control of concrete company products, and has better flexibility. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the application equally.

[0029] Working principle: In the synthetic flocculant of the present invention, a certain amount of chain transfer agent is used to control the molecular weight of the linear main chain, and a certain amount of cross-linking agent is added to form a local micro-cross-linking structure, so that the overall polymer molecular weight meets the requirements of the flocculant structure, ensuring the rapid flocculation and sedimentation of suspended particles in the water during the sand washing process. Furthermore, because the structure may contain a small amount of double cross-linked polymers, that is, a three-dimensional network structure, more colloidal particles and suspended matter in the water can be captured and swept up compared to flocculants such as polyacrylamide during the flocculation and sedimentation process, and has a higher flocculation efficiency.

[0030] When the flocculant prepared by the present invention is used, after the sand washing is completed, the residual flocculant in the sand washing water and the water-washed sand will be decomposed into small molecular linear polymers due to the hydrolysis of the ester group in the cross-linking agent during storage, and the micro-crosslinking part will be broken, so that the flocculant loses its flocculation function. Even if some unhydrolyzed flocculants still enter the concrete, they will be rapidly hydrolyzed in the strong alkaline environment of cement. At the same time, the hydrophilic groups such as carboxyl and sulfonic acid groups on the side chains of the small molecular linear polymers together with the lipophilic main chain constitute a small molecule surfactant with certain wetting and anti-mud sacrificial functions, which can provide auxiliary effects on the dispersion and dispersion retention of concrete, thereby achieving the purpose of minimizing the impact on the state and strength of the concrete mixture during the application of sand washing water and water-washed sand in concrete.

[0031] Embodiment 1: A method for preparing a water-washed sand flocculant comprises the following steps: adding an appropriate amount of water and 75 grams of acrylic acid, 400 grams of acrylamide, and 42 grams of 2-acrylamide-2-methylpropanesulfonic acid into a reaction kettle, stirring evenly, adding sodium hydroxide to adjust the pH to 8-10, then adding 40 grams of methacryloyloxyethyl trimethylammonium chloride, 4 grams of ethylene glycol dimethacrylate, and 1 gram of mercaptoethanol, stirring evenly, adding 1.1 grams of hydrogen peroxide and 0.5 grams of VC, stirring again for 5 minutes, and then standing for 5 hours to obtain a gel product, which is a liquid flocculant. The obtained liquid flocculant is sheared and granulated, dried at 120°C, and crushed to obtain a powder flocculant.

[0032] Embodiment 2: A method for preparing a water-washed sand flocculant comprises the following steps: adding an appropriate amount of water and 75 grams of acrylic acid, 410 grams of acrylamide, and 45 grams of 2-acrylamide-2-methylpropanesulfonic acid into a reaction kettle, stirring evenly, adding sodium hydroxide to adjust the pH to 8-10, then adding 45 grams of methacryloyloxyethyl trimethylammonium chloride, 3 grams of ethylene glycol diacrylate, and 1.1 grams of mercaptopropionic acid, stirring evenly, adding 2 grams of ammonium persulfate and 0.8 grams of bleaching powder, stirring again for 5 minutes and then standing for 5 hours to obtain a gel product, which is a liquid flocculant. The obtained liquid flocculant is sheared and granulated, dried at 120°C, and crushed to obtain a powder flocculant.

[0033] Embodiment 3: A method for preparing a water-washed sand flocculant comprises the following steps: adding an appropriate amount of water and 75 grams of acrylic acid, 350 grams of acrylamide, and 50 grams of 2-acrylamide-2-methylpropanesulfonic acid into a reaction kettle, stirring evenly, adding sodium hydroxide to adjust the pH to 8-10, then adding 45 grams of dimethyldiallylammonium chloride, 4 grams of ethylene glycol dimethacrylate, and 1 gram of thioglycolic acid, stirring evenly, adding 2.1 grams of potassium persulfate and 0.8 grams of sodium hypophosphite, stirring again for 5 minutes, and then standing for 5 hours to obtain a gel product, which is a liquid flocculant. The obtained liquid flocculant is sheared and granulated, dried at 120°C, and crushed to obtain a powder flocculant.

[0034] The molecular structure of the flocculants prepared in the above-mentioned Examples 1, 2 and 3 is

[0035]

[0036] Comparative example: Cationic polyacrylamide with a molecular weight of 12 million produced by a certain factory on the market.

[0037] Performance Testing

[0038] 1. Flocculant performance test

[0039] The flocculant prepared by the above method was tested using SY / T 5796-93 "Flocculant Evaluation Method" and expressed by turbidity. The specific test results are shown in Table 1.

[0040] Table 1

[0041] Test items Comparative Example Example 1 Example 2 Example 3 Turbidity removal rate / % 93.57 94.62 93.85 95.61

[0042] It can be seen from the data in Table 1 that the turbidity removal rate of the flocculant of the present invention is better than that of the comparative example, indicating that it has a good flocculation effect.

[0043] 2. Detection of the influence of residual flocculant on concrete performance

[0044] The experiment used sand without flocculant, sand containing comparative example flocculant and sand containing example flocculant to carry out concrete experimental test.

[0045] The test concrete mix proportions are shown in Table 2.

[0046] Table 2

[0047]

[0048] The concrete test results are shown in Table 3.

[0049] Table 3

[0050]

[0051] From the results in Table 3, it can be seen that the flocculant in the comparative example has a great influence on the slump and expansion of concrete. The flocculant in the embodiment still has a much lower performance than the sample without flocculant, but compared with the comparative example, the initial slump and the slump and expansion at 1 hour are greatly improved. At the same time, it can be seen that the slump and expansion at 1 hour in the embodiment are very small compared with the initial changes. From the mechanism analysis, the residual flocculant still has some influence when the concrete is initially stirred, and with the continuous hydrolysis under alkaline conditions, it brings auxiliary wetting and anti-mud sacrificial effects. The macroscopic performance is that the flocculant of the present invention does not cause much loss in slump and expansion.

Claims

1. A method for preparing a water-washed sand flocculant, characterized in that: The following steps are involved: S1. Add water, acrylic acid, acrylamide and 2-acrylamide-2-methylpropanesulfonic acid to the reactor, stir and mix well, and then add sodium hydroxide to adjust the pH to 8 to 10; S2. Add cationic monomer, crosslinking agent and chain transfer agent to the solution of step S1 in sequence, mix well, add initiator and reducing agent, stir for 5 minutes and let stand for 5 hours to obtain a gel-like liquid flocculant; S3. The liquid flocculant obtained in step S2 is sheared and granulated, dried at 120°C and crushed to obtain a powder flocculant; Among them, the molar ratio of each raw material is: acrylic acid: acrylamide: 2-acrylamide-2-methylpropane sulfonic acid: cationic monomer: cross-linking agent = 1: (1-5): (0.1-0.5): (0.1-0.5): (0.03-0.1); the mass ratio of chain transfer agent, initiator and reducing agent to the total monomer is: (0.001-0.003): (0.001-0.003): (0.0005-0.001).

2. The method for preparing a water-washed sand flocculant according to claim 1, characterized in that: The cationic monomer includes at least one of methacryloyloxyethyltrimethylammonium chloride or dimethyldiallylammonium chloride.

3. The method for preparing a water-washed sand flocculant according to claim 1, characterized in that: The cross-linking agent includes at least one of ethylene glycol dimethacrylate or ethylene glycol diacrylate.

4. The method for preparing a water-washed sand flocculant according to claim 1, characterized in that: The initiator includes at least one of hydrogen peroxide, ammonium persulfate or potassium persulfate.

5. The method for preparing a water-washed sand flocculant according to claim 1, characterized in that: The reducing agent includes at least one of VC, bleaching powder or sodium hypophosphite.

6. The method for preparing a water-washed sand flocculant according to claim 1, characterized in that: The chain transfer agent includes at least one of mercaptoethanol, mercaptopropionic acid or thioglycolic acid.

7. The method for preparing a water-washed sand flocculant according to claim 1, characterized in that: The molecular structure of the prepared flocculant is:

8. A liquid flocculant, characterized in that: Prepared by the method according to any one of claims 1 to 7, the liquid flocculant is in gel form.

9. A powder flocculant, characterized in that: The product is prepared by the method according to any one of claims 1 to 7 through shearing granulation, drying and crushing.

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