Flocculating agent for coking wastewater as well as preparation method and application of flocculating agent

Abstract

The invention discloses a flocculating agent for coking wastewater and a preparation method and application thereof, the flocculating agent is prepared from the following raw materials in parts by weight: 1-5 parts of poly dimethyl diallyl ammonium chloride and 6-12 parts of a compound, and the compound is prepared from kaolin loaded N-succinyl-O-carboxymethyl chitosan and konjac glucomannan. The method is used for solving the technical problem that the coking wastewater cannot reach the discharge standard.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a flocculant for coking wastewater and a preparation method and application thereof. Background Art

[0002] Coke is a reducing agent widely used in the ironmaking industry. China is the largest coke producer, and coking wastewater is produced during the coke production process. Coking wastewater is a typical toxic and difficult-to-degrade organic wastewater, mainly from the initial cooling of coke oven gas and the production water and steam condensation wastewater in the coke production process. In order to effectively treat coking wastewater and reduce the COD, chromaticity and cyanide content in coking wastewater, flocculants are usually required to treat coking wastewater.

[0003] At present, the flocculants on the market are mainly aluminum flocculants and iron flocculants. After the aluminum flocculant is used to treat wastewater, the aluminum content in the effluent will increase. After the aluminum enters the drinking water through the water cycle, it is easy to cause a variety of diseases and threaten the ecological health. The iron flocculant has a high COD removal efficiency, but because the iron ions themselves are colored, the chromaticity of the effluent often does not meet the discharge requirements. Therefore, there is an urgent need for a flocculant for coking wastewater. Summary of the invention

[0004] The invention provides a flocculant for coking wastewater and a preparation method and application thereof, which are used to solve the technical problem that the existing coking wastewater cannot meet the discharge requirements.

[0005] In view of this, the present invention provides a flocculant for coking wastewater, which comprises 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 kaolin loaded with N-succinyl-O-carboxymethyl chitosan and konjac glucomannan.

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

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

[0008] The amount of acetic acid solution added is 2%, the amount of acetic acid solution added to each 1g of N-succinyl-O-carboxymethyl chitosan is 4-6mL, and 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: immersing the kaolin in a hydrochloric acid solution, taking it out, heating it in an oil bath, stirring it continuously, cooling it down, washing it, and drying it to obtain the pretreated kaolin.

[0011] Furthermore, the kaolin is pretreated by the following method before use: immersing the kaolin in a hydrochloric acid solution, taking it out, heating it in an oil bath at a temperature of 90-100° C., stirring it continuously for 1-3 hours, cooling it to 22±3° C., washing it with water for 3-5 times, and drying it to obtain the pretreated kaolin;

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

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

[0014] A1: put chitosan into isopropanol, mix well, add sodium hydroxide, let stand, then add chloroacetic acid, mix well, heat, react, centrifuge, wash, and 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 into solution A; after the addition is complete, heat and heat up 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 by 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°C, react for 1-3 hours, centrifuge, and 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 to solution A at a rate of 4-8 mL / min; after the addition is complete, heat to 30-50°C, 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 to each 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 to each 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 to each 1g of succinic anhydride is 10-20mL, and the amount of anhydrous ethanol added to each 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 put into water, urea is added, and the mixture is mixed evenly, then the konjac glucomannan is added, the mixture is mixed evenly, the mixture is heated, baked, and cooled to obtain the pretreated konjac glucomannan.

[0021] Furthermore, the konjac glucomannan is pretreated by the following method before use: sodium dihydrogen phosphate and disodium hydrogen phosphate are put into water, urea is added, the mixture is mixed evenly, konjac glucomannan is added, the mixture is mixed evenly, the mixture is heated to 130-150° C., baked for 30-60 min, and cooled to 22±3° C. to obtain 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 gram of konjac glucomannan is 1-3 mL.

[0023] A method for preparing a flocculant for coking wastewater comprises the following steps: uniformly mixing polydimethyldiallylammonium chloride and a composite material, and drying to obtain the flocculant.

[0024] The invention discloses an application of a flocculant for coking wastewater, comprising the following steps: putting the flocculant into water, mixing evenly, adding the coking wastewater to be treated under aeration, and letting it stand to obtain the treated coking wastewater.

[0025] Furthermore, an application of a flocculant for coking wastewater comprises the following steps: putting the flocculant into water, mixing evenly, adding the coking wastewater to be treated under aeration, and standing for 1-2 hours to obtain treated coking wastewater;

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

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

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

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

[0030] 1. The present application adopts kaolin to load N-succinyl-O-carboxymethyl chitosan and konjac glucomannan to obtain a composite material. First, kaolin has a large specific surface area and has excellent adsorption properties. It is mainly used to adsorb pigments in coking wastewater and effectively reduce the chromaticity of coking wastewater. In addition, kaolin also has a loading effect and can load N-succinyl-O-carboxymethyl chitosan and konjac glucomannan. In addition, 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 with N-succinyl-O-carboxymethyl chitosan, the molecular chain of N-succinyl-O-carboxymethyl chitosan carries a positive charge, and the electrical neutralization efficiency can be improved by utilizing the overlapping effect of the positive charge. After the two are compounded, there are a large number of amino groups 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 the present application, acid solution is used to pre-treat kaolin, which can change the structure of kaolin and remove impurities on the surface and in the structure, thereby significantly increasing its surface area, which is beneficial to improving the adsorption and ability to serve as a carrier.

[0032] 3. In the present application, sodium dihydrogen phosphate, disodium hydrogen phosphate and urea are used to pretreat konjac glucomannan before use, which can increase the charge density on the konjac glucomannan molecules, make it have a stronger charge attraction, improve the adsorption capacity of oppositely charged pollutants, and form hydrogen bonds and introduce functional groups, thereby further improving the treatment capacity of coking wastewater. DETAILED DESCRIPTION

[0033] In order to make the technical scheme of the present invention better understood by the personnel of the technical field, the technical scheme in the embodiment of the present invention is clearly and completely described below. Obviously, the described embodiment is only a part of the embodiment of the present invention, rather than all the embodiments. Based on the embodiment in the present invention, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of the present invention. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

[0034] Preparation Example

[0035] Preparation Example 1

[0036] A kind of N-succinyl-O-carboxymethyl chitosan, which is prepared by the following method:

[0037] A1: Put 2 kg of chitosan into 24 L of isopropanol, mix well, add 6 kg of sodium hydroxide, let stand for 2 hours, then add 3 kg of chloroacetic acid, mix well, heat to 50 ° C, react for 2 hours, centrifuge, and 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 completed, the temperature was raised to 40°C and stirred for 4 hours. Anhydrous ethanol was added, the mixture was centrifuged, washed with water for 5 times, and dried to obtain N-succinyl-O-carboxymethyl chitosan.

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

[0040] Preparation Example 2

[0041] A composite is 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% by mass acetic acid solution, 0.6 kg of konjac mannan and hydrogen peroxide were added, mixed evenly, and heated to 50° C. to obtain a mixture; 2 kg of kaolin was added, mixed evenly, and continued to heat to 80° C., dried, and crushed to obtain a composite;

[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 composite, which is different from Preparation Example 2 in that the amount of N-succinyl-O-carboxymethyl chitosan added is different, and the amount of N-succinyl-O-carboxymethyl chitosan added in Preparation Example 3 is 1.6 kg.

[0046] Preparation Example 4

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

[0048] Preparation Example 5

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

[0050] Preparation Example 6

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

[0052] Example

[0053] Example 1

[0054] A flocculant for coking wastewater, the raw material composition of which is shown in Table 1.

[0055] A method for preparing a flocculant for coking wastewater comprises 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] Embodiment 2-5

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

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

[0060] raw material Example 1 Example 2 Example 3 Example 4 Example 5 Polydimethyldiallylammonium chloride 1 1 1 3 5 Compound 6 8 12 8 8

[0061] Embodiment 6-9

[0062] A flocculant for coking wastewater, which differs from Example 4 in that the sources of the composite are different, and the composites in Examples 6-9 are prepared by Preparation Examples 3-6, respectively.

[0063] Example 10

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

[0065] Embodiment 11

[0066] A flocculant for coking wastewater, which differs from Example 10 in that the konjac glucomannan in the composite is pretreated by the following method before use: sodium dihydrogen phosphate and disodium hydrogen phosphate are put into water, urea is added, mixed evenly, then konjac glucomannan is added, mixed evenly, heated to 140° C., baked for 45 min, cooled to 25° C., and pretreated konjac glucomannan is obtained; wherein 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 to each 1 g of konjac glucomannan is 2 mL.

[0067] Comparative Example

[0068] Comparative Example 1

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

[0070] Comparative Example 2

[0071] A flocculant for coking wastewater, which differs from Example 1 in that an equal amount of N-succinyl-O-carboxymethyl chitosan in the composite is replaced by konjac glucomannan.

[0072] Comparative Example 3

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

[0074] Comparative Example 4

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

[0076] Application Examples

[0077] Application Example 1

[0078] An application of a flocculant for coking wastewater comprises the following steps:

[0079] The flocculant prepared in Example 1 was put into 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, wherein the amount of water added to each 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 flocculants in Application Example 2-11 are prepared using Examples 2-11.

[0082] Application Comparative Examples 1-4

[0083] The difference between application comparative examples 1-4 and application example 1 is that the flocculants in application comparative examples 1-4 are prepared by using comparative examples 1-4 respectively.

[0084] Performance testing

[0085] The following tests were performed on the coking wastewater treated in Example 1-11 and Comparative Example 1-4:

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

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

[0088] Chroma: The chroma of the treated coking wastewater was measured in accordance with GB / T11903-89 “Determination of Chroma of Water Quality”. The test results are shown in Table 2.

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

[0090] Table 2 Test results

[0091]

[0092] It can be seen from Table 2 that the flocculant for coking wastewater of the present application effectively reduces the COD content, cyanide content and chroma in the coking wastewater through the synergistic effect of various raw materials, wherein the COD removal rate is 95.7-99.2%, the cyanide removal rate is 95.9-98.5%, and the chroma removal rate is 65.3-83.3%.

[0093] Combining Application Example 1 and Application 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 chroma removal rate is 65.3%, which are better than Application Comparative Examples 1-4, indicating that the composite prepared by kaolin, N-succinyl-O-carboxymethyl chitosan, and konjac glucomannan is more suitable and can better improve the removal rates of COD, cyanide, and chroma in coking wastewater.

[0094] Combining application examples 1-5, it can be seen that the removal rate of COD in application example 4 is 96.6%, the removal rate of cyanide is 97.0%, and the removal rate of chroma is 72.7%, which are better than other application examples, indicating that the addition amount of polydimethyldiallylammonium chloride and the composite in application example 4 is more appropriate;

[0095] Among them, the addition amount of polydimethyldiallyl ammonium chloride within a certain range can more effectively adsorb the pigment in the coking wastewater and can more effectively reduce the chromaticity. However, when the addition amount of polydimethyldiallyl ammonium chloride is too small, it cannot achieve a better adsorption effect of chromaticity. When the addition amount of polydimethyldiallyl ammonium chloride is too large, it may cause the redispersion of the flocculant, which will reduce the chromaticity removal effect.

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

[0097] Combining Application Example 4 and Application Examples 6-9, it can be seen that the COD removal rate in Application Example 8 is 97.4%, the cyanide removal rate is 97.7%, and the chromaticity removal rate is 78.0%, which are better than other application examples, indicating that the composite prepared by Preparation Example 5 is more suitable, that is, the addition amount of N-succinyl-O-carboxymethyl chitosan and konjac glucomannan in Preparation Example 5 is more suitable. Excessive addition of N-succinyl-O-carboxymethyl chitosan and konjac glucomannan will not only fail to improve the treatment effect, but will increase the treatment cost of coking wastewater, resulting in a waste of resources, and excessive addition may cause the flocculant to disperse again, reduce the flocculation effect, and cause the treatment effect to deteriorate.

[0098] Combining Application Example 8 and Application Example 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 chroma removal rate is 80.7%, which are better than Application Example 8, indicating that it is more appropriate to pretreat the kaolin in the composite before use, which can change the structure of kaolin and remove impurities on the surface and in the structure, thereby significantly increasing its surface area, which is beneficial to improving the adsorption and ability to serve as a carrier.

[0099] Combining Application Example 10 and Application Example 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 chromaticity removal rate is 83.3%, which are better than Application Example 8, indicating that it is more appropriate to pretreat the konjac glucomannan in the complex before use, which increases the charge density on the konjac glucomannan molecules, making it have a stronger charge attraction, improves the adsorption capacity for pollutants with opposite charges, and can also form hydrogen bonds and introduce functional groups, thereby further improving the treatment capacity for coking wastewater.

[0100] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flocculant for coking wastewater, characterized in that: The invention comprises the following raw materials in parts by weight: 1-5 parts of polydimethyldiallylammonium chloride and 6-12 parts of a composite material, wherein the composite material is prepared by kaolin loaded with N-succinyl-O-carboxymethyl chitosan and konjac glucomannan.

2. The flocculant for coking wastewater according to claim 1, characterized in that: The composite is prepared by the following method: N-succinyl-O-carboxymethyl chitosan is placed in an acetic acid solution, konjac mannan and hydrogen peroxide are added, mixed evenly, and heated to obtain a mixture; kaolin is then added, mixed evenly, heated continuously, dried, and crushed to obtain a composite.

3. The flocculant for coking wastewater according to claim 2, 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).

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

5. The flocculant for coking wastewater according to claim 1, characterized in that: The N-succinyl-O-carboxymethyl chitosan is prepared by the following method: A1: put chitosan into isopropanol, mix well, add sodium hydroxide, let stand, then add chloroacetic acid, mix well, heat, react, centrifuge, wash, and 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 into solution A; after the addition is complete, heat and heat up while stirring continuously; add anhydrous ethanol; centrifuge, wash, and dry to obtain N-succinyl-O-carboxymethyl chitosan.

6. 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 put into water, urea is added, the mixture is evenly mixed, then the konjac glucomannan is added, the mixture is evenly mixed, heating, baking, and cooling to obtain the pretreated konjac glucomannan.

7. A method for preparing a flocculant for coking wastewater according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: uniformly mixing polydimethyldiallylammonium chloride and a compound, and drying the mixture to obtain a flocculant.

8. An application of a flocculant for coking wastewater according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: putting a flocculant into water, mixing evenly, adding the coking wastewater to be treated under aeration, and letting it stand to obtain the treated coking wastewater.

9. The use of the flocculant for coking wastewater according to claim 8, characterized in that: The aeration time is 20-40 minutes.

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

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