A flocculant for coking wastewater and a preparation method and application thereof

Abstract

The application discloses a flocculant for coking wastewater and a preparation method and application thereof, and comprises the following raw materials in parts by weight: 1-5 parts of polydimethyl diallyl ammonium chloride and 6-12 parts of a composite, wherein the composite is prepared from kaolin loaded N-succinyl-O-carboxymethyl chitosan and konjac glucomannan. The application aims at solving the technical problem that coking wastewater cannot reach the discharge standard.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and particularly relates to a flocculant for coking wastewater, its preparation method, and its application. Background Technology

[0002] Coke is a widely used reducing agent in the iron and steel industry. China is the largest coke producer, and coking wastewater is generated during the coke production process. Coking wastewater is a typical toxic and recalcitrant organic wastewater, mainly originating from the primary cooling of coke oven gas, production water used in coke production, and steam condensate wastewater. To effectively treat coking wastewater and reduce its COD, color, and cyanide content, flocculants are typically used.

[0003] Currently, the flocculants on the market are mainly aluminum-based and iron-based flocculants. After treating wastewater with aluminum-based flocculants, the aluminum content in the effluent increases. Aluminum can easily cause various diseases and threaten ecological health when it enters drinking water through water circulation. Iron-based flocculants have a high COD removal efficiency, but because iron ions are colored, the color of the effluent often fails to meet the discharge requirements. Therefore, there is an urgent need for a flocculant for coking wastewater. Summary of the Invention

[0004] This invention provides a flocculant for coking wastewater, its preparation method, and its application, in order to solve the technical problem that current coking wastewater does not meet discharge requirements.

[0005] In view of this, the present invention provides a flocculant for coking wastewater, comprising the following raw materials in parts by weight: 1-5 parts of polydimethyldiallylammonium chloride and 6-12 parts of a complex, wherein the complex is prepared by loading N-succinyl-O-carboxymethyl chitosan and konjac glucomannan onto kaolin.

[0006] Optionally, the composite is prepared by the following method: N-succinyl-O-carboxymethyl chitosan is placed in an acetic acid solution, konjac glycosaminoglycan and hydrogen peroxide are added, mixed evenly, and heated to obtain a mixture; then kaolin is added, mixed evenly, and heated further, dried, and pulverized to obtain the composite.

[0007] Furthermore, the composite is prepared by the following method: N-succinyl-O-carboxymethyl chitosan is placed in an acetic acid solution, konjac glycosaminoglycan and hydrogen peroxide are added, mixed evenly, and heated to 40-60℃ to obtain a mixture; then kaolin is added, mixed evenly, and heated to 70-90℃, dried, and pulverized to obtain the composite.

[0008] The amount of acetic acid solution added is 2%, and the amount of acetic acid solution added to each 1g of N-succinyl-O-carboxymethyl chitosan is 4-6mL. The weight ratio of N-succinyl-O-carboxymethyl chitosan to hydrogen peroxide is 1:(0.1-0.3).

[0009] Optionally, the weight ratio of kaolin, N-succinyl-O-carboxymethyl chitosan, and konjac glucomannan is 1:(0.7-0.9):(0.3-0.5).

[0010] Optionally, the kaolin is pretreated by the following method before use: the kaolin is soaked in hydrochloric acid solution, then taken out, heated in an oil bath, continuously stirred, cooled, washed, and dried to obtain pretreated kaolin.

[0011] Furthermore, the kaolin is pretreated by the following method before use: the kaolin is soaked in hydrochloric acid solution, then taken out and heated in an oil bath at 90-100℃ for 1-3 hours with continuous stirring. After cooling to 22±3℃, it is rinsed with water 3-5 times and dried to obtain pretreated kaolin.

[0012] The hydrochloric acid solution has a mass fraction of 20%, and the amount of hydrochloric acid solution added to each 1g of kaolin is 6-8mL.

[0013] Optionally, the N-succinyl-O-carboxymethyl chitosan is prepared by the following method:

[0014] A1: Chitosan is placed in isopropanol, mixed evenly, sodium hydroxide is added, allowed to stand, then chloroacetic acid is added, mixed evenly, heated to increase temperature, reacted, centrifuged, and washed to obtain O-carboxymethyl chitosan.

[0015] A2: Place O-carboxymethyl chitosan in water and mix well to obtain solution A. Place succinic anhydride in acetone and mix well to obtain solution B. Add solution B dropwise to solution A. After the addition is complete, heat the solution while stirring continuously. Add anhydrous ethanol, centrifuge, wash, and dry to obtain N-succinyl-O-carboxymethyl chitosan.

[0016] Furthermore, the N-succinyl-O-carboxymethyl chitosan is prepared using the following method:

[0017] A1: Place chitosan in isopropanol, mix well, add sodium hydroxide, let stand for 1-3 hours, then add chloroacetic acid, mix well, heat to 40-60℃, react for 1-3 hours, centrifuge, wash with water 3-5 times to obtain O-carboxymethyl chitosan.

[0018] A2: Place O-carboxymethyl chitosan in water and mix well to obtain solution A. Place succinic anhydride in acetone and mix well to obtain solution B. Add solution B dropwise to solution A at a rate of 4-8 mL / min. After the addition is complete, heat to 30-50℃ and stir continuously for 3-5 hours. Add anhydrous ethanol, centrifuge, wash with water 3-5 times, and dry to obtain N-succinyl-O-carboxymethyl chitosan.

[0019] In step A1, the amount of isopropanol added per 1g of chitosan is 10-14mL, the weight ratio of chitosan to sodium hydroxide is 1:(2-5), and the weight ratio of chitosan to chloroacetic acid is 1:(1-2). In step A2, the amount of water added per 1g of O-carboxymethyl chitosan is 20-30mL, the weight ratio of chitosan to succinic anhydride is 1:(0.7-0.9), the amount of acetone added per 1g of succinic anhydride is 10-20mL, and the amount of anhydrous ethanol added per 1g of O-carboxymethyl chitosan is 4-6mL.

[0020] Optionally, the konjac glucomannan is pretreated by the following method before use: sodium dihydrogen phosphate and disodium hydrogen phosphate are placed in water, urea is added, and the mixture is stirred evenly. Then, konjac glucomannan is added, stirred evenly, heated, baked, and cooled to obtain pretreated konjac glucomannan.

[0021] Furthermore, the konjac glucomannan is pretreated by the following method before use: Sodium dihydrogen phosphate and disodium hydrogen phosphate are placed in water, urea is added, and the mixture is stirred evenly. Then, konjac glucomannan is added, and the mixture is stirred evenly. The mixture is heated to 130-150℃, baked for 30-60 minutes, and cooled to 22±3℃ to obtain the pretreated konjac glucomannan.

[0022] The weight ratio of konjac glucomannan, sodium dihydrogen phosphate, disodium hydrogen phosphate, and urea is 1:(0.03-0.05):(0.03-0.05):(0.02-0.04), and the amount of water added to each 1g of konjac glucomannan is 1-3mL.

[0023] A method for preparing a flocculant for coking wastewater includes the following steps: mixing polydimethyldiallylammonium chloride and a composite evenly, drying, and obtaining the flocculant.

[0024] An application of a flocculant for coking wastewater includes the following steps: adding the flocculant to water, mixing it evenly, adding the coking wastewater to be treated under aeration, and allowing it to stand to obtain the treated coking wastewater.

[0025] Furthermore, the application of a flocculant for coking wastewater includes the following steps: adding the flocculant to water, mixing it evenly, adding the coking wastewater to be treated under aeration, and letting it stand for 1-2 hours to obtain the treated coking wastewater;

[0026] The amount of water added per 1g of flocculant is 8-12mL.

[0027] Optionally, the aeration time is 20-40 minutes.

[0028] Optionally, the amount of flocculant added is 0.5-0.8 wt% of the coking wastewater to be treated.

[0029] As can be seen from the above technical solutions, the embodiments of the present invention have the following advantages:

[0030] 1. This application uses a complex obtained by loading N-succinyl-O-carboxymethyl chitosan and konjac glucomannan onto kaolin. First, kaolin has a large specific surface area and excellent adsorption properties, mainly used to adsorb pigments in coking wastewater, effectively reducing the color of coking wastewater. In addition, kaolin also has a loading effect, capable of loading N-succinyl-O-carboxymethyl chitosan and konjac glucomannan. Furthermore, N-succinyl-O-carboxymethyl chitosan is a derivative of chitosan and has abundant active groups such as hydroxyl and amino groups. Konjac glucomannan is a natural high-molecular-weight polysaccharide. By compounding it with N-succinyl-O-carboxymethyl chitosan, the N-succinyl-O-carboxymethyl chitosan molecular chain carries a positive charge, which can improve the charge neutralization efficiency by utilizing the overlap effect of positive charges. After the two are compounded, there are a large number of amino and hydroxyl groups, thereby further increasing the specific surface area and improving the adsorption of COD and pigments. Through the synergistic effect of kaolin, N-succinyl-O-carboxymethyl chitosan, and konjac glucomannan, the adsorption of pigments and COD in coking wastewater is further improved, making it easier for coking wastewater to meet discharge standards.

[0031] 2. In this application, acid is used to pretreat kaolin, which can change the structure of kaolin, remove impurities on the surface and in the structure, thereby significantly increasing its surface area and improving its adsorption and ability as a carrier.

[0032] 3. In this application, sodium dihydrogen phosphate, disodium hydrogen phosphate, and urea are used to pretreat konjac glucomannan before use. This can increase the charge density on the konjac glucomannan molecules, making them more attractive to charges and improving their adsorption capacity for pollutants with opposite charges. It can also form hydrogen bonds and introduce functional groups, thereby further improving the treatment capacity for coking wastewater. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the present invention can be purchased on the market or prepared by existing methods.

[0034] Preparation Example

[0035] Preparation Example 1

[0036] An N-succinyl-O-carboxymethyl chitosan, prepared by the following method:

[0037] A1: Place 2 kg of chitosan into 24 L of isopropanol, mix well, add 6 kg of sodium hydroxide, let stand for 2 h, then add 3 kg of chloroacetic acid, mix well, heat to 50 °C, react for 2 h, centrifuge, wash with water 5 times to obtain O-carboxymethyl chitosan.

[0038] A2: O-carboxymethyl chitosan was placed in water and mixed evenly to obtain solution A. 1.6 kg of succinic anhydride was placed in acetone and mixed evenly to obtain solution B. Solution B was added dropwise to solution A at a rate of 6 mL / min. After the addition was complete, the temperature was raised to 40 °C and stirred continuously for 4 h. Anhydrous ethanol was added, centrifuged, washed 5 times with water, and dried to obtain N-succinyl-O-carboxymethyl chitosan.

[0039] In step A2, the amount of water added per 1g of O-carboxymethyl chitosan is 25mL, the amount of acetone added per 1g of succinic anhydride is 15mL, and the amount of anhydrous ethanol added per 1g of O-carboxymethyl chitosan is 5mL.

[0040] Preparation Example 2

[0041] A complex prepared by the following method:

[0042] 1.4 kg of N-succinyl-O-carboxymethyl chitosan prepared in Preparation Example 1 was placed in a 2% acetic acid solution, 0.6 kg of konjac glucomannan and hydrogen peroxide were added, mixed evenly, and heated to 50°C to obtain a mixture; then 2 kg of kaolin was added, mixed evenly, and heated to 80°C, dried, and pulverized to obtain a complex.

[0043] The amount of acetic acid solution added to each 1g of N-succinyl-O-carboxymethyl chitosan is 5mL, and the weight ratio of N-succinyl-O-carboxymethyl chitosan to hydrogen peroxide is 1:0.2.

[0044] Preparation Example 3

[0045] A complex differs from Preparation Example 2 in that the amount of N-succinyl-O-carboxymethyl chitosan added is different; in Preparation Example 3, the amount of N-succinyl-O-carboxymethyl chitosan added is 1.6 kg.

[0046] Preparation Example 4

[0047] A complex differs from Preparation Example 2 in that the amount of N-succinyl-O-carboxymethyl chitosan added is different; in Preparation Example 4, the amount of N-succinyl-O-carboxymethyl chitosan added is 1.8 kg.

[0048] Preparation Example 5

[0049] A complex, which differs from Preparation Example 3 in that the amount of konjac glucomannan added is different; in Preparation Example 5, the amount of konjac glucomannan added is 0.8 kg.

[0050] Preparation Example 6

[0051] A complex, which differs from Preparation Example 3 in that the amount of konjac glucomannan added is different; in Preparation Example 6, the amount of konjac glucomannan added is 1 kg.

[0052] Example

[0053] Example 1

[0054] A flocculant for coking wastewater has the following raw material composition as shown in Table 1.

[0055] A method for preparing a flocculant for coking wastewater includes the following steps:

[0056] The polydimethyldiallylammonium chloride and the composite prepared in Preparation Example 2 were mixed evenly and dried to obtain a flocculant.

[0057] Examples 2-5

[0058] A flocculant for coking wastewater differs from that in Example 1 in that the raw material ratio of the flocculant is different, as shown in Table 1.

[0059] Table 1. Weight of each raw material for flocculant (kg)

[0060] raw material Example 1 Example 2 Example 3 Example 4 Example 5 Polydiallyl ammonium chloride 1 1 1 3 5 complex 6 8 12 8 8

[0061] Examples 6-9

[0062] A flocculant for coking wastewater differs from Example 4 in that the source of the complex is different; the complexes in Examples 6-9 were prepared using Preparation Examples 3-6, respectively.

[0063] Example 10

[0064] A flocculant for coking wastewater differs from Example 8 in that the kaolin in the composite is pretreated before use by the following method: the kaolin is soaked in a 20% hydrochloric acid solution, then heated in an oil bath at 95°C for 2 hours with continuous stirring, cooled to 25°C, rinsed 5 times with water, and dried to obtain pretreated kaolin. The amount of hydrochloric acid solution added per 1g of kaolin is 7mL.

[0065] Example 11

[0066] A flocculant for coking wastewater differs from that in Example 10 in that the konjac glucomannan in the complex is pretreated before use by the following method: sodium dihydrogen phosphate and disodium hydrogen phosphate are placed in water, urea is added, and the mixture is stirred evenly. Then, konjac glucomannan is added, stirred evenly, heated to 140°C, baked for 45 minutes, and cooled to 25°C to obtain pretreated konjac glucomannan. The weight ratio of konjac glucomannan, sodium dihydrogen phosphate, disodium hydrogen phosphate, and urea is 1:0.04:0.04:0.03, and the amount of water added per 1g of konjac glucomannan is 2mL.

[0067] Comparative Example

[0068] Comparative Example 1

[0069] A flocculant for coking wastewater, which differs from Example 1 in that the complex is replaced with an equal amount of kaolin.

[0070] Comparative Example 2

[0071] A flocculant for coking wastewater, which differs from Example 1 in that the N-succinyl-O-carboxymethyl chitosan in the complex is replaced in equal amounts with konjac glucomannan.

[0072] Comparative Example 3

[0073] A flocculant for coking wastewater, which differs from Example 1 in that the konjac glucomannan in the complex is replaced in equal amounts with N-succinyl-O-carboxymethyl chitosan.

[0074] Comparative Example 4

[0075] A flocculant for coking wastewater, which differs from Example 1 in that no complex is added to the flocculant.

[0076] Application examples

[0077] Application Example 1

[0078] The application of a flocculant for coking wastewater includes the following steps:

[0079] The flocculant prepared in Example 1 was placed in water and mixed evenly. The coking wastewater to be treated was added under aeration and allowed to stand for 1.5 hours to obtain pretreated coking wastewater. The amount of water added per 1g of flocculant was 10mL, the aeration time was 30min, and the amount of flocculant added was 0.7wt% of the coking wastewater to be treated.

[0080] Application Example 2-11

[0081] The difference between Application Example 2-11 and Application Example 1 is that the flocculant in Application Example 2-11 was prepared using the method described in Example 2-11.

[0082] Application Comparative Examples 1-4

[0083] The difference between Comparative Examples 1-4 and Application Example 1 is that the flocculants in Comparative Examples 1-4 were prepared using the methods described in Comparative Examples 1-4.

[0084] Performance testing

[0085] The following tests were performed on the coking wastewater treated in corresponding use cases 1-11 and application comparison examples 1-4:

[0086] COD: The COD in the treated coking wastewater was determined according to HJ828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method". The test results are shown in Table 1.

[0087] Cyanide: HJ 484-2009 "Determination of Cyanide in Water - Volumetric and Spectrophotometric Methods" was used to determine cyanide in treated coking wastewater. The results are shown in Table 2.

[0088] Color: The color of the treated coking wastewater was measured according to GB / T11903-89 "Determination of Color in Water". The test results are shown in Table 2.

[0089] Before treatment, the COD content in the coking wastewater was 2500 mg / L, the cyanide content was 100 mg / L, and the color intensity was 150 times.

[0090] Table 2 Detection Results

[0091]

[0092] As can be seen from Table 2, the flocculant for coking wastewater of this application effectively reduces the COD content, cyanide content and color in coking wastewater through the synergistic effect between the raw materials. The removal rate of COD is 95.7-99.2%, the removal rate of cyanide is 95.9-98.5%, and the removal rate of color is 65.3-83.3%.

[0093] Combining Application Example 1 and Comparative Examples 1-4, it can be seen that the COD removal rate in Application Example 1 is 95.7%, the cyanide removal rate is 95.9%, and the color removal rate is 65.3%, which is better than that in Comparative Examples 1-4. This indicates that the composite material prepared by using kaolin, N-succinyl-O-carboxymethyl chitosan, and konjac glucomannan is more suitable and can better improve the removal rate of COD, cyanide, and color in coking wastewater.

[0094] As can be seen from Application Examples 1-5, the COD removal rate in Application Example 4 was 96.6%, the cyanide removal rate was 97.0%, and the color removal rate was 72.7%, which was better than other application examples. This indicates that the amount of polydimethyl diallyl ammonium chloride and the complex added in Application Example 4 was more appropriate.

[0095] Among them, the addition of polydimethyl diallyl ammonium chloride can more effectively adsorb pigments in coking wastewater and reduce color more effectively within a certain range. However, when the addition of polydimethyl diallyl ammonium chloride is too small, it will not play a better role in adsorbing color. When the addition of polydimethyl diallyl ammonium chloride is too large, it may lead to the redispersion of flocculant, which will reduce the color removal effect.

[0096] Within a certain range, the addition of the complex can more effectively adsorb and remove COD, cyanide, and color from coking wastewater. However, when the amount of the complex added is too small, it will not achieve better adsorption. When the amount of the complex added is too large, it will easily lead to the redispersion of the flocculant, that is, the flocculant will be redisperded into smaller particles, which will reduce the flocculation effect and make the adsorption effect worse.

[0097] Combining Application Examples 4 and 6-9, it can be seen that the COD removal rate in Application Example 8 was 97.4%, the cyanide removal rate was 97.7%, and the color removal rate was 78.0%, which is better than other application examples. This indicates that the complex prepared by Preparation Example 5 is more suitable. That is, the amount of N-succinyl-O-carboxymethyl chitosan and konjac glucomannan added in Preparation Example 5 is more appropriate. If too much N-succinyl-O-carboxymethyl chitosan and konjac glucomannan is added, it will not only fail to improve the treatment effect, but will also increase the treatment cost of coking wastewater and cause resource waste. Moreover, excessive addition may lead to redispersion of flocculants, which will reduce the flocculation effect and result in poor treatment effect.

[0098] Combining Application Examples 8 and 10, it can be seen that the COD removal rate in Application Example 10 is 98.9%, the cyanide removal rate is 98.2%, and the color removal rate is 80.7%, which is better than Application Example 8. This indicates that it is more appropriate to pretreat the kaolin in the composite before use, which can change the structure of the kaolin, remove impurities on the surface and in the structure, thereby significantly increasing its surface area, which is beneficial to improving its adsorption and its ability as a carrier.

[0099] Combining Application Examples 10 and 11, it can be seen that the COD removal rate in Application Example 11 is 99.2%, the cyanide removal rate is 98.5%, and the color removal rate is 83.3%, which is better than Application Example 8. This indicates that pretreatment of the konjac glucomannan in the complex before use is more appropriate, as it increases the charge density on the konjac glucomannan molecules, giving them stronger charge attraction and improving their adsorption capacity for pollutants with opposite charges. It can also form hydrogen bonds and introduce functional groups, thereby further improving the treatment capacity for coking wastewater.

[0100] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An application of a flocculant for coking wastewater, characterized in that: The process includes the following steps: adding flocculant to water, mixing it evenly, adding the coking wastewater to be treated under aeration, letting it stand, removing cyanide from the coking wastewater, and obtaining the treated coking wastewater. The flocculant comprises the following raw materials in parts by weight: 1-5 parts of polydimethyldiallylammonium chloride and 6-12 parts of the composite; the composite is prepared by the following method: N-succinyl-O-carboxymethyl chitosan is placed in acetic acid solution, konjac glucomannan and hydrogen peroxide are added, mixed evenly, heated to obtain a mixture; then kaolin is added, mixed evenly, heated further, dried, and pulverized to obtain the composite.

2. The application of the flocculant for coking wastewater according to claim 1, characterized in that: The weight ratio of kaolin, N-succinyl-O-carboxymethyl chitosan, and konjac glucomannan is 1:(0.7-0.9):(0.3-0.5).

3. The application of the flocculant for coking wastewater according to claim 1, characterized in that: Before use, the kaolin is pretreated by the following method: the kaolin is soaked in hydrochloric acid solution, then taken out, heated in an oil bath, stirred continuously, cooled, washed, and dried to obtain pretreated kaolin.

4. The application of the flocculant for coking wastewater according to claim 1, characterized in that: The N-succinyl-O-carboxymethyl chitosan was prepared by the following method: A1: Chitosan is placed in isopropanol, mixed evenly, sodium hydroxide is added, allowed to stand, then chloroacetic acid is added, mixed evenly, heated to increase temperature, reacted, centrifuged, and washed to obtain O-carboxymethyl chitosan. A2: Place O-carboxymethyl chitosan in water and mix well to obtain solution A. Place succinic anhydride in acetone and mix well to obtain solution B. Add solution B dropwise to solution A. After the addition is complete, heat the solution while stirring continuously. Add anhydrous ethanol, centrifuge, wash, and dry to obtain N-succinyl-O-carboxymethyl chitosan.

5. The application of the flocculant for coking wastewater according to claim 1, characterized in that: The konjac glucomannan is pretreated by the following method before use: sodium dihydrogen phosphate and disodium hydrogen phosphate are placed in water, urea is added, and the mixture is stirred evenly. Then, konjac glucomannan is added, stirred evenly, heated, baked, and cooled to obtain pretreated konjac glucomannan.

6. The application of the flocculant for coking wastewater according to any one of claims 1-5, characterized in that: The preparation method of the flocculant includes the following steps: mixing polydimethyldiallylammonium chloride and the composite evenly, drying, and obtaining the flocculant.

7. The application of the flocculant for coking wastewater according to claim 1, characterized in that: The aeration time is 20-40 minutes.

8. The application of the flocculant for coking wastewater according to claim 1, characterized in that: The amount of flocculant added is 0.5-0.8 wt% of the coking wastewater to be treated.

Images