Preparation Method and Application of a Composite Polymer Flocculant

Abstract

The invention discloses a preparation method and application of a composite polymer flocculant, belonging to the technical field of flocculants. First, a mixed solvent is placed in a reaction kettle, and a part of acrylamide, a crosslinking agent, a part of functional monomers and 3-benzylmercapto thiocarbonyl propionic acid are slowly added to the reaction kettle under stirring conditions. Nitrogen is introduced, and the reaction is carried out under nitrogen protection and the action of an initiator. After 5 hours, the remaining acrylamide and functional monomers are added to the reaction system, and the initiator is supplemented at the same time. After the feeding is completed, the reaction continues for 8 hours to obtain. In the invention, through the introduction of functional monomers and crosslinking agents, a polymer structure containing comb-shaped branched chains can be formed, so that the flocculant can be easily and effectively spread out in sewage, and has a more remarkable flocculation effect; the obtained flocculant has extremely high application value in the field of sewage treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of flocculants, and specifically relates to a preparation method and application of a composite polymer flocculant. Background Art

[0002] Flocculants are mainly applied in the fields of water supply and sewage treatment. Among them, cationic flocculants are one of the water-soluble polymers that are currently widely used, and are mainly applied to the solid-liquid separation processes in industry, including processes such as sedimentation, clarification, concentration, and sludge dewatering. Through the electro-neutralization effect of the positively charged groups contained therein on the organic colloids with opposite charges in the sludge and the bridging adsorption effect of the polymer, the colloidal particles are induced to aggregate into massive flocs, so that the colloidal particles are separated from the suspension.

[0003] The existing cationic polyacrylamide flocculants are prepared by introducing cationic monomers (generally methylacryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, etc.). Those skilled in the art know that this polymer has a linear structure, a large molecular weight, a high viscosity of the formed aqueous solution, and the small molecular side chains of the linear polymer have poor compatibility with the oily hydrophobic organic matters in the sewage, and it is difficult to be uniformly dispersed in the sewage, which affects the flocculation effect. In addition, the introduced cationic monomers have a low cation density. If it is necessary to increase the cationicity of the flocculant, only the dosage of such monomers can be increased. However, if the dosage is too much, the colloidal particles wrapped by the cations will repel each other, resulting in small flocs and slow sedimentation, thereby reducing the flocculation effect. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a preparation method and application of a composite polymer flocculant.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A preparation method of a composite polymer flocculant includes the following steps:

[0007] S1. Add itaconic acid and acetone into a three-necked flask, place it in a low-temperature constant-temperature bath at 0 °C, add EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride) and NHS (N-hydroxysulfosuccinimide), stir and mix evenly, then slowly dropwise add N-methylethylenediamine. After the addition is completed, place the three-necked flask at room temperature and stir for reaction for 2 h. After removing acetone by rotary evaporation under reduced pressure, purify it by column chromatography (the eluent is a mixed solvent of chloroform and methanol, and the volume ratio of the two is 3:2). Finally, rotary evaporate the eluent to obtain intermediate 1. The dosage ratio of itaconic acid, EDC, NHS, and N-methylethylenediamine is 6.5 g:9.6 g:5.7 g:7.4 g;

[0008] Under the action of EDC and NHS, the -COOH on the itaconic acid molecule undergoes an amidation reaction with the -NH2 on the diethylenetriamine molecule to obtain Intermediate 1. The reaction process is shown as follows;

[0009]

[0010] S2. Add Intermediate 1, triethylamine, ethyl acetate, and chloroform into a dry three-necked flask. Place the flask in an ice bath and stir to mix. When the system temperature stabilizes at 0 - 2 °C, slowly dropwise add 1-chlorodecane with stirring. After the addition is complete, continue the reaction at room temperature for 3 h. Filter to remove the generated salt. After the filtrate is concentrated under reduced pressure to remove the solvent, column chromatography purification is carried out using a mixed solvent of n-hexane - ethyl acetate as the eluent (the volume ratio of the two is 11:9). Concentrate the eluent by rotary evaporation to obtain Intermediate 2; the dosage ratio of Intermediate 1, triethylamine, and 1-chlorodecane is 12.1 g:10.1 g:17.7 g;

[0011] Under the action of triethylamine, the -NH- on the Intermediate 1 molecule undergoes a nucleophilic substitution reaction with 1-chlorodecane (halohydrocarbon) to obtain Intermediate 2. The process is shown as follows:

[0012]

[0013] S3. Add Intermediate 2, iodomethane, and chloroform into a three-necked flask. Raise the temperature to 45 °C and reflux for 4 h. Carry out rotary evaporation (to remove acetonitrile and excess iodomethane) to obtain the functional monomer; the dosage ratio of Intermediate 2 and iodomethane is 26.8 g:28.4 g;

[0014] The tertiary amine on the Intermediate 2 molecule undergoes a quaternization reaction under the action of iodomethane to obtain the functional monomer. The process is shown as follows:

[0015]

[0016] S4. First, place the mixed solvent in a reaction kettle. Under stirring conditions, slowly add a part of acrylamide, crosslinking agent, a part of functional monomer, and 3-benzylmercapto thiocarbonyl propionic acid (chain transfer agent) into the reaction kettle. Introduce nitrogen gas. After complete dissolution, under nitrogen protection, heat the oil bath to 56 °C and then add an appropriate amount of azodicyanovaleric acid (initiator) for reaction. After 5 h, add the remaining acrylamide and functional monomer into the reaction system, and supplement the initiator at the same time. After the feeding is completed, continue the reaction for 8 h. Rotate and evaporate to remove the solvent, wash it repeatedly with absolute ethanol 4 - 5 times, dry it and then pulverize it to obtain the flocculant. The dosage ratio of acrylamide, crosslinking agent, functional monomer, and 3-benzylmercapto thiocarbonyl propionic acid is 100 g: 8 - 9 mg: 90 - 110 g: 80 - 88 mg; the dosage of azodicyanovaleric acid is 2% of the mass of acrylamide; and the mass ratio of acrylamide added for the first time to that added for the second time is 1:3, and the mass ratios of the functional monomer added for the first time and the second time, and the initiator added for the first time and the second time are both 1:2; the mixed solvent is a mixture of acetic acid-sodium acetate buffer solution (pH value is 5) and absolute ethanol in a volume ratio of 1:1.

[0017] Acrylamide, functional monomer, and crosslinking agent undergo a polymerization reaction to obtain a high-molecular flocculant. The reaction process is as follows:

[0018]

[0019] Under the crosslinking action of the crosslinking agent, and by controlling the dosage of the crosslinking agent and the use of the chain transfer agent, the structure of the formed flocculant has more branched chains, forming a comb-like structure. Compared with linear macromolecules, the branched chains have a smaller molecular weight, and most of the branched chains contain nitrogen positive ions. Therefore, the flocculant is easy to effectively spread out in sewage, and can fully contact with the impurities in the sewage, and is easy to capture impurity molecules, so as to better play the role of electric neutralization and adsorption bridging, and has a more significant flocculation effect. In addition, through the introduction of the functional monomer, each functional monomer contains two longer molecular chains, and the molecular chains contain nitrogen positive ions and long fatty carbon chains. The presence of nitrogen positive ions can increase the charge density of the branched chains and enhance the electric neutralization effect. And because it has spread out, it is difficult to have the phenomenon of charge repulsion of colloidal particles in the later stage. In addition, the nitrogen positive ion is connected with a long fatty carbon chain, which has extremely high flexibility and lipophilicity. After adsorbing oily impurities through electron adsorption and bridging adsorption, it can penetrate between the impurity particles and generate an association effect, thereby further improving the flocculation effect.

[0020] It should be further noted that the molecular structure of the crosslinking agent contains a six-membered ring with a large steric hindrance, which can further increase the distance between branched chains, thereby improving the spreading state of the branched chains and further enhancing the flocculation effect of the flocculant.

[0021] In addition, due to the existence of the branched-chain spreading structure, larger flocs can be formed, thereby increasing the sedimentation rate of the flocs and improving the flocculation effect.

[0022] Furthermore, the crosslinking agent is prepared through the following steps:

[0023] Add piperazine, triethylamine, and ethanol into a dry three-necked flask, then place it in an ice bath, start stirring. When the temperature stabilizes at 0 - 2 °C, slowly drop 4-chlorobutene under stirring. After the dropping is completed, continue the reaction at room temperature for 3 h. After removing the solvent by rotary evaporation under reduced pressure, recrystallize and purify with cyclohexane, and dry under vacuum to obtain the crosslinking agent; the dosage ratio of piperazine, triethylamine, and 4-chlorobutene is 8.6 g: 20.2 g: 18.1 g;

[0024] Under the action of triethylamine, the -NH- on the piperazine molecule undergoes a nucleophilic substitution reaction with 4-chlorobutene to obtain the crosslinking agent, and the process is as follows:

[0025]

[0026] The above-obtained polymer flocculant can be applied to the field of oily sewage treatment to achieve good flocculation and sedimentation effects.

[0027] Advantages of the present invention:

[0028] In the cationic polyacrylamide flocculant of the present invention, by introducing functional monomers and crosslinking agents, a polymer structure containing comb-like branched chains can be formed, making the flocculant easy to spread effectively in sewage, and fully contacting with impurities in the sewage, which is easy to capture impurity molecules, thereby better exerting the electro-neutralization effect and adsorption bridging effect, and having a more significant flocculation effect; in addition, the introduction of functional monomers can effectively enhance the electro-neutralization effect and the association effect with impurity particles, and due to the existence of the branched-chain spreading structure, larger flocs can be formed, thereby increasing the sedimentation rate of the flocs and improving the flocculation effect; the obtained flocculant has extremely high application value in the field of oily sewage treatment. Specific embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Example 1

[0031] Prepare the crosslinking agent:

[0032] 8.6 g of piperazine, 20.2 g of triethylamine and 100 mL of ethanol were added to a dry three-necked flask, and then placed in an ice bath. Stirring was started. When the temperature was stabilized at 0 - 2 °C, 18.1 g of 4-chlorobutene was slowly added dropwise under stirring. After the addition was completed, the reaction was continued at room temperature for 3 h. After removing the solvent by rotary evaporation under reduced pressure, recrystallization purification was carried out using cyclohexane, and vacuum drying was performed to obtain the crosslinking agent.

[0033] Example 2

[0034] Preparation of composite polymer flocculant:

[0035] S1. 6.5 g of itaconic acid and 80 mL of acetone were added to a three-necked flask, placed in a low-temperature constant temperature bath at 0 °C, 9.6 g of EDC and 5.7 g of NHS were added. After stirring and mixing evenly, 7.4 g of N-methylethylenediamine was slowly added dropwise. After the addition was completed, the three-necked flask was placed at room temperature and stirred for reaction for 2 h. After removing acetone by rotary evaporation under reduced pressure, column chromatography purification was carried out (the eluent was a mixed solvent of chloroform and methanol, and the volume ratio of the two was 3:2). Finally, the eluent was rotary evaporated to obtain intermediate 1;

[0036] S2. 12.1 g of intermediate 1, 10.1 g of triethylamine, 50 mL of ethyl acetate and 50 mL of chloroform were added to a dry three-necked flask. The flask was placed in an ice bath and stirred and mixed. When the system temperature was stabilized at 0 - 2 °C, 17.7 g of 1-chlorodecane was slowly added dropwise under stirring. After the addition was completed, the reaction was continued at room temperature for 3 h. The generated salt was removed by filtration. After the filtrate was rotary evaporated to remove the solvent, column chromatography purification was carried out using a mixed solvent of n-hexane - ethyl acetate as the eluent (the volume ratio of the two was 11:9). The eluent was rotary evaporated to obtain intermediate 2;

[0037] S3. 26.8 g of intermediate 2, 28.4 g of methyl iodide and 80 mL of chloroform were added to a three-necked flask. The temperature was raised to 45 °C and refluxed for 4 h, and rotary evaporation (removing acetonitrile and excessive methyl iodide) was carried out to obtain the functional monomer;

[0038] S4. First, 800 mL of a mixed solvent (400 mL of acetic acid - sodium acetate buffer solution with a pH of 5 and 400 mL of absolute ethanol) was placed in a reaction kettle. Under stirring conditions, 25 g of acrylamide, 8 mg of crosslinking agent, 30 g of functional monomer and 80 mg of 3-benzylmercapto thiocarbonylpropionic acid (chain transfer agent) were slowly added to the reaction kettle. Nitrogen was introduced, and after complete dissolution, under nitrogen protection, the oil bath was heated to 56 °C, and then 0.67 g of azodicyanovaleric acid (initiator) was added for reaction. After 5 h, the remaining 75 g of acrylamide and 60 g of functional monomer were added to the reaction system, and at the same time, 1.33 g of initiator was added. After the addition was completed, the reaction was continued for 8 h. The solvent was removed by rotary evaporation, and it was repeatedly washed 4 times with absolute ethanol, dried and pulverized to obtain the flocculant.

[0039] Example 3

[0040] Preparation of composite polymer flocculant:

[0041] S1. Add 6.5 g of itaconic acid and 80 mL of acetone into a three-necked flask, place it in a low-temperature constant temperature bath at 0 °C, add 9.6 g of EDC and 5.7 g of NHS, stir and mix evenly, then slowly drop in 7.4 g of N-methylethylenediamine. After the dropping is completed, place the three-necked flask at room temperature and stir for reaction for 2 h. After removing acetone by rotary evaporation under reduced pressure, purify it by column chromatography (the eluent is a mixed solvent of chloroform and methanol, and the volume ratio of the two is 3:2). Finally, rotary evaporate the eluent to obtain intermediate 1;

[0042] S2. Add 12.1 g of intermediate 1, 10.1 g of triethylamine, 50 mL of ethyl acetate and 50 mL of chloroform into a dry three-necked flask, place the flask in an ice bath, stir and mix. When the system temperature is stable at 0-2 °C, slowly drop in 17.7 g of 1-chlorodecane under stirring. After the dropping is completed, continue the reaction at room temperature for 3 h. Filter to remove the generated salt. After the filtrate is rotary evaporated to remove the solvent under reduced pressure, purify it by column chromatography with a mixed solvent of n-hexane-ethyl acetate as the eluent (the volume ratio of the two is 11:9). Rotary evaporate the eluent to obtain intermediate 2;

[0043] S3. Add 26.8 g of intermediate 2, 28.4 g of methyl iodide and 80 mL of chloroform into a three-necked flask, raise the temperature to 45 °C and reflux for reaction for 4 h, and rotary evaporate (remove acetonitrile and excessive methyl iodide) to obtain the functional monomer;

[0044] S4. First, place 800 mL of a mixed solvent (400 mL of acetic acid-sodium acetate buffer solution with a pH of 5 and 400 mL of absolute ethanol) in a reaction kettle. Under stirring conditions, slowly add 25 g of acrylamide, 8-9 mg of cross-linking agent, 36.7 g of functional monomer and 88 mg of 3-benzylmercaptothiocarbonylpropionic acid (chain transfer agent) into the reaction kettle. Pass in nitrogen. After fully dissolving, under nitrogen protection, raise the temperature of the oil bath to 56 °C and then add 0.67 g of azodicyanovaleric acid (initiator) for reaction. After 5 h, add the remaining 75 g of acrylamide and 73.3 g of functional monomer into the reaction system, and simultaneously add 1.33 g of initiator. After the feeding is completed, continue the reaction for 8 h. Rotary evaporate to remove the solvent, wash it repeatedly with absolute ethanol for 4-5 times, dry it and then pulverize it to obtain the flocculant.

[0045] Comparative example

[0046] A cationic polyacrylamide flocculant obtained by solution polymerization using acrylamide and methacryloyloxyethyltrimethylammonium chloride as polymerization monomers.

[0047] Configure the oily sewage (simulating the sewage from an oilfield production station with an oil content of 150 mg / L) as the experimental object. Add the flocculants of Example 2, Example 3 and the comparative example to the oily sewage at a dosage of 40 mg / L, and carry out a flocculation reaction at 50 °C for 30 min. Observe the oil-water interface after contact according to the SY / T5797-93 method, then carry out oil-water separation, test the oil content in the obtained aqueous phase according to the SY / T5797-93 method, and observe the appearance of the aqueous phase. The results are shown in the following table:

[0048] Example 2 Example 3 Comparative example Oil content in water after 30 min (mg / L) 17.3 16.6 32.5 Oil removal rate (%) 88.5 88.9 78.3 Oil-water interface Clear Clear Relatively clear Water color Clear Clear Relatively clear

[0049] It can be seen from the data in the above table that the flocculant obtained by the present invention has high flocculation and sedimentation effects on oily sewage; combined with the data of the comparative example, it can be known that the treatment performance of the present invention on oily sewage is significantly higher than that of ordinary cationic polyacrylamide flocculants.

[0050] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0051] The above content is only an example and explanation of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A preparation method of a composite polymer flocculant, characterized in that, It includes the following steps: S1. Add itaconic acid and acetone into a three-necked flask, place it in a low-temperature constant-temperature bath at 0 °C, add EDC and NHS, stir and mix evenly, then slowly dropwise add N-methylethylenediamine. After the addition is completed, place the three-necked flask at room temperature and stir for reaction for 2 h. After removing acetone by rotary evaporation under reduced pressure, purify it by column chromatography, and finally rotary dry the eluent to obtain intermediate 1; S2. Add intermediate 1, triethylamine, ethyl acetate and chloroform into a dry three-necked flask, place the flask in an ice bath, stir and mix. When the system temperature is stable at 0-2 °C, slowly dropwise add 1-chlorodecane under stirring. After the addition is completed, continue the reaction at room temperature for 3 h. Filter to remove the generated salt. After the filtrate is rotary evaporated to remove the solvent under reduced pressure, purify it by column chromatography using a mixed solvent of n-hexane-ethyl acetate as the eluent, and rotary dry the eluent to obtain intermediate 2; S3. Add intermediate 2, methyl iodide and chloroform into a three-necked flask, raise the temperature to 45 °C and reflux for reaction for 4 h, then rotary evaporate to obtain the functional monomer; S4. First, place the mixed solvent in a reaction kettle. Under stirring conditions, slowly add a part of acrylamide, crosslinking agent, a part of the functional monomer and 3-benzylmercapto thiocarbonyl propionic acid into the reaction kettle, introduce nitrogen gas, and after fully dissolving, under nitrogen protection, raise the temperature of the oil bath to 56 °C and then add an appropriate amount of azodicyanovaleric acid for reaction. After 5 h, add the remaining acrylamide and functional monomer into the reaction system, and at the same time supplement the initiator. After the feeding is completed, continue the reaction for 8 h. Rotary evaporate to remove the solvent, wash it repeatedly with absolute ethanol for 4-5 times, dry it and then pulverize it to obtain the flocculant.

2. The preparation method of a composite polymer flocculant according to claim 1, characterized in that, In step S1, the dosage ratio of itaconic acid, EDC, NHS, and N-methylethylenediamine is 6.5 g:9.6 g:5.7 g:7.4 g.

3. The preparation method of a composite polymer flocculant according to claim 1, characterized in that, In step S2, the dosage ratio of intermediate 1, triethylamine and 1-chlorodecane is 12.1 g:10.1 g:17.7 g.

4. The preparation method of a composite polymer flocculant according to claim 1, characterized in that In step S3, the dosage ratio of intermediate 2 and methyl iodide is 26.8 g:28.4 g.

5. The preparation method of a composite polymer flocculant according to claim 1, characterized in that, In step S4, the dosage ratio of acrylamide, crosslinking agent, functional monomer and 3-benzylmercapto thiocarbonyl propionic acid is 100 g:8-9 mg:90-110 g:80-88 mg; the dosage of azodicyanovaleric acid is 2% of the mass of acrylamide; the mixed solvent is a mixture obtained by mixing acetic acid-sodium acetate buffer solution and absolute ethanol according to a volume ratio of 1:

1.

6. The preparation method of a composite polymer flocculant according to claim 1, characterized in that, The crosslinking agent is prepared through the following steps: Add piperazine, triethylamine and ethanol into a dry three-necked flask, then place it in an ice bath, start stirring. When the temperature is stable at 0-2 °C, slowly dropwise add 4-chlorobutene under stirring. After the addition is completed, continue the reaction at room temperature for 3 h. After removing the solvent by rotary evaporation under reduced pressure, purify it by recrystallization using cyclohexane, and vacuum dry it to obtain the crosslinking agent.

7. The preparation method of a composite polymer flocculant according to claim 6, characterized in that, The dosage ratio of piperazine, triethylamine and 4-chlorobutene is 8.6 g:20.2 g:18.1 g. Application of the composite polymer flocculant prepared by the method according to any one of claims 1-7 in the treatment of oily sewage.

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