A kind of pickling wastewater treatment process

Abstract

The present application relates to a pickling wastewater treatment process, including neutralization treatment, precipitation treatment, oxidation treatment, biological treatment and fine treatment. The present application uses calcium ions in lime and fluoride ions to form calcium fluoride precipitation to remove fluoride ions. The hydroxide of sodium hydroxide helps the precipitation of magnesium and aluminum ions, and can also neutralize with acids to generate salt and water to reduce the hardness of water. Sodium polystyrene sulfonate is a commonly used polymer adsorbent, which is widely used in wastewater treatment. Methacryloyloxyethyl trimethylammonium chloride is used as a cationic sewage flocculant to improve the flocculation effect. The modified chitosan has a high molecular weight, and can obtain a suitable charge density through the functional groups it has. Many parts extend into the liquid phase to improve the electrical neutralization efficiency. The extended part can also adsorb more colloidal particles to promote flocculation precipitation.

Description

Technical Field

[0001] The present application relates to the technical field of pickling wastewater treatment, and in particular to a pickling wastewater treatment process. Background Art

[0002] During the production process, steel pipes and other steel products generally need to be pickled and then rinsed with clean water. The direct discharge of the generated pickling wastewater does not meet environmental protection requirements and is therefore not allowed; therefore, the pickling wastewater needs to be treated accordingly. The traditional treatment method for pickling wastewater usually adopts neutralization-coagulation-precipitation-filter pressing-filter cake formation-landfill.

[0003] The existing Chinese patent with publication number CN105923852A discloses a steel pickling wastewater treatment process, which includes the following steps: (1) the steel pickling wastewater enters the security filter after the flow is adjusted in the flow regulating tank, and then enters the ultrafiltration membrane assembly for ultrafiltration membrane filtration after preliminary filtration; (2) the steel pickling wastewater after ultrafiltration membrane filtration is sent to the primary reverse osmosis water tank and the secondary reverse osmosis water tank through the first pressure pump for reverse osmosis filtration treatment, and the effluent of the secondary reverse osmosis water tank enters the clean water tank; (3) the high-concentration salt solution in the first reverse osmosis water tank and the second reverse osmosis water tank is sent to the neutralization reaction tank; (4) a neutralizer is added to the reduction reaction tank to adjust the pH; (5) the high-concentration salt solution after neutralization treatment is sent to the cathode tank of the diaphragm electrolytic cell.

[0004] With respect to the above-mentioned related technologies, the inventors believe that the flocculation effect of some current pickling wastewater treatments is not ideal, resulting in poor treatment effects, and there is still room for improvement. Summary of the invention

[0005] In order to improve the flocculation and sedimentation effect of pickling wastewater treatment and enhance the treatment effect of pickling wastewater, the present application provides a pickling wastewater treatment process.

[0006] The present application provides a pickling wastewater treatment process that adopts the following technical solution:

[0007] A pickling wastewater treatment process comprises the following steps:

[0008] S1. Neutralization treatment: Mix sodium hydroxide, lime and water to perform preliminary precipitation of the wastewater;

[0009] S2. Sedimentation treatment; add flocculant to the wastewater after initial precipitation in S1 for treatment, add 7-8 parts of flocculant per ton of wastewater, stir at a stirring speed of 40-80r / min for 8-10min;

[0010] S3. Oxidation treatment: adjusting the pH in the oxidation tank to 7.0-8.0 for electrolytic oxidation to reduce the concentration of heavy metal ions and iron ions;

[0011] S4. Biological treatment: the pickling wastewater after precipitation enters the biological treatment tank to convert organic matter into carbon dioxide and water through metabolism; S5. Fine treatment: the water in the oxidation tank is extracted through a reverse osmosis RO membrane to remove trace heavy metals, salts, etc. in the water; the flocculant in S2 includes the following components in parts by weight:

[0012] 20-30 parts of sodium polystyrene sulfonate;

[0013] 2-3 parts of methacryloyloxyethyl trimethyl ammonium chloride;

[0014] 6-8 parts of modified chitosan.

[0015] By adopting the above technical scheme, the calcium ions in the lime can form calcium fluoride precipitates with fluoride ions to remove fluoride ions, the hydroxide of sodium hydroxide helps the precipitation of magnesium and aluminum ions, and can also neutralize with acids to generate salt and water to reduce the hardness of water; sodium polystyrene sulfonate is a commonly used polymer adsorbent, which is widely used in wastewater treatment, and methacryloyloxyethyltrimethylammonium chloride is used as a cationic sewage flocculant to improve the flocculation effect; the modified chitosan has a high molecular weight, and can obtain a suitable charge density through the functional groups it possesses. Many parts extend into the liquid phase to improve the electrical neutralization efficiency. The extended parts can also adsorb more colloidal particles to promote flocculation precipitation.

[0016] Preferably, the preparation method of the modified chitosan is: 3-4 parts of oxidized polyethylene wax emulsion and 3-6 parts of chitosan are mixed with 1-2 parts of 0.02-0.03 mol / L isopropanol aluminum toluene solution, passed through N2 for 10-15 min, 20-25° C. oil bath, then 8-12 parts of ε-caprolactone are added, and the reaction is continued for 2-3 hours.

[0017] By adopting the above technical scheme, the oxidized polyethylene wax emulsion has carbonyl and hydroxyl groups, and aluminum isopropoxide is used to initiate the ring opening of ε-caprolactone and form a graft copolymer with the oxidized polyethylene wax emulsion having hydroxyl groups and chitosan, so that the obtained polycaprolactone grafted polymer mixture has a strong flocculation ability.

[0018] Preferably, in terms of weight ratio, the oxidized polyethylene wax emulsion: chitosan: ε-caprolactone = 3:4:9.

[0019] Preferably, the flocculant further comprises 2-3 parts of gelatin and 4-6 parts of D-adipaldehyde glucose by weight.

[0020] By adopting the above technical scheme, gelatin is dissolved in a hot mixture of glycerol and water, and D-adipaldehyde glucose is further added to produce cross-linking, so that the molecular chain contains a certain number of polar groups, which can adsorb solid particles suspended in water, form bridges between particles, or cause the particles to condense into large floccules according to charge neutralization, thereby accelerating the sedimentation of particles in the suspension, thereby enhancing the flocculation effect of the flocculant.

[0021] Preferably, the flocculant further comprises 1-2 parts of succinic anhydride and 0.1-0.2 parts of 4-dimethylaminopyridine by weight.

[0022] By adopting the above technical solution, the carboxyl-containing succinic anhydride further combines with the hydroxyl group and is easily dissociated under alkaline conditions to produce COO - , which is beneficial to improve the adsorption capacity and prolong the action time of the flocculant.

[0023] Preferably, in terms of weight ratio, the sodium hydroxide: lime: water = (1-2): (3-4): 8.

[0024] Preferably, the pH value of the wastewater in S2 is adjusted to 7-8.

[0025] In summary, this application includes the following beneficial technical effects:

[0026] 1. The calcium ions in the lime can form calcium fluoride precipitation with fluoride ions to remove fluoride ions. The hydroxide of sodium hydroxide helps the precipitation of magnesium and aluminum ions, and can also neutralize with acids to generate salt and water to reduce the hardness of water. Sodium polystyrene sulfonate is a commonly used polymer adsorbent, which is widely used in wastewater treatment. Methacryloyloxyethyl trimethyl ammonium chloride is used as a cationic sewage flocculant to improve the flocculation effect. The modified chitosan has a high molecular weight and can obtain a suitable charge density through the functional groups it has. Many parts extend into the liquid phase to improve the electrical neutralization efficiency. The extended part can also adsorb more colloidal particles to promote flocculation precipitation.

[0027] 2. Oxidized polyethylene wax emulsion has carbonyl and hydroxyl groups. Aluminum isopropoxide is used to initiate the ring opening of ε-caprolactone and form a graft copolymer with oxidized polyethylene wax emulsion with hydroxyl groups and chitosan. The obtained polycaprolactone grafted polymer mixture has a strong flocculation ability.

[0028] 3. Gelatin is dissolved in a hot mixture of glycerol and water, and D-adipaldehyde glucose is further added to produce cross-linking, so that the molecular chain contains a certain number of polar groups, which can adsorb solid particles suspended in water, make bridges between particles, or condense particles to form large floccules according to charge neutralization, thereby accelerating the sedimentation of particles in the suspension, thereby improving the flocculation effect of the flocculant; succinic anhydride containing carboxyl groups is further combined with hydroxyl groups, and is easily dissociated under alkaline conditions to produce COO -, which is beneficial to improve the adsorption capacity and prolong the action time of the flocculant. DETAILED DESCRIPTION

[0029] The present application is described in further detail below.

[0030] In the present application, chitosan is provided by Shanghai Eon Chemical Technology Co., Ltd., with a deacetylation degree ≥95% (viscosity 100-200mPa.s), brand: Ron reagent, product number: R094950; the oxidized polyethylene wax emulsion is SOFT-80 oxidized polyethylene wax emulsion provided by Hai'an Petrochemical Plant, Jiangsu Province; ε-caprolactone is provided by Shanghai Eon Chemical Technology Co., Ltd., brand: Ron reagent, product number: R014209; gelatin is 120 frozen gelatin particles provided by Shandong Pingju Biotechnology Co., Ltd., a strong supplier, with item number 214; D-adipaldehyde glucose is provided by Shenzhen Jiangchuan Pharmaceutical Technology Co., Ltd., CAS: 3056-44-8, item number: RG-G122106.

[0031] Unless otherwise specified, the raw materials used in the following embodiments can be obtained from common commercial sources.

[0032] Example

[0033] Example 1

[0034] This embodiment discloses a pickling wastewater treatment process, comprising the following steps:

[0035] S1. Neutralization treatment: Mix sodium hydroxide, lime and water to perform preliminary precipitation on the wastewater, in a weight ratio of sodium hydroxide: lime: water = 1:3:8;

[0036] S2. Sedimentation treatment; add flocculant to the wastewater after initial precipitation in S1 for treatment, add 7 parts of flocculant per ton of wastewater, adjust the pH value of the wastewater to 7, and stir at a stirring speed of 40r / min for 8min;

[0037] S3. Oxidation treatment: adjusting the pH to 7.0 in the oxidation tank for electrolytic oxidation to reduce the concentration of heavy metal ions and iron ions;

[0038] S4. Biological treatment: The pickling wastewater after precipitation enters the biological treatment tank to convert organic matter into carbon dioxide and water through metabolism;

[0039] S5. Fine treatment: extract the water in the oxidation pool through a reverse osmosis RO membrane to remove trace heavy metals, salt, etc. in the water;

[0040] The flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethyl ammonium chloride and modified chitosan, and the content of each component is shown in Table 1 below.

[0041] The preparation method of modified chitosan is as follows: 3 parts of oxidized polyethylene wax emulsion and 3 parts of chitosan are mixed with 1 part of 0.02 mol / L isopropanol aluminum toluene solution, passed N2 for 10 min, 20°C oil bath, then 8 parts of ε-caprolactone are added, and the reaction is continued for 2 hours.

[0042] Example 2

[0043] This embodiment discloses a pickling wastewater treatment process, comprising the following steps:

[0044] S1. Neutralization treatment; sodium hydroxide, lime and water are mixed to perform preliminary precipitation of the wastewater, and the weight ratio is sodium hydroxide: lime: water = 2:5:8;

[0045] S2. Sedimentation treatment; add flocculant to the wastewater after initial sedimentation in S1 for treatment, add 8 parts of flocculant per ton of wastewater, and stir at a stirring speed of 80r / min for 10min;

[0046] S3. Oxidation treatment: adjusting the pH to 8.0 in the oxidation tank for electrolytic oxidation to reduce the concentration of heavy metal ions and iron ions;

[0047] S4. Biological treatment: The pickling wastewater after precipitation enters the biological treatment tank to convert organic matter into carbon dioxide and water through metabolism;

[0048] S5. Fine treatment: extract the water in the oxidation pool through a reverse osmosis RO membrane to remove trace heavy metals, salt, etc. in the water;

[0049] The flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethyl ammonium chloride and modified chitosan, and the content of each component is shown in Table 1 below.

[0050] The preparation method of modified chitosan is as follows: 4 parts of oxidized polyethylene wax emulsion and 6 parts of chitosan are mixed with 2 parts of 0.03 mol / L isopropanol aluminum toluene solution, passed N2 for 15 min, oil bath at 25°C, then 12 parts of ε-caprolactone are added, and the reaction is continued for 3 hours.

[0051] Example 3

[0052] This embodiment discloses a pickling wastewater treatment process, comprising the following steps:

[0053] S1. Neutralization treatment; sodium hydroxide, lime and water are mixed to perform preliminary precipitation of the wastewater, and the weight ratio is sodium hydroxide: lime: water = 2:3:8;

[0054] S2. Sedimentation treatment; add flocculant to the wastewater after initial sedimentation in S1 for treatment, add 8 parts of flocculant per ton of wastewater, and stir at a stirring speed of 6r / min for 9min;

[0055] S3. Oxidation treatment: adjusting the pH to 8.0 in the oxidation tank for electrolytic oxidation to reduce the concentration of heavy metal ions and iron ions;

[0056] S4. Biological treatment: The pickling wastewater after precipitation enters the biological treatment tank to convert organic matter into carbon dioxide and water through metabolism;

[0057] S5. Fine treatment: extract the water in the oxidation pool through a reverse osmosis RO membrane to remove trace heavy metals, salt, etc. in the water;

[0058] The flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethyl ammonium chloride and modified chitosan, and the content of each component is shown in Table 1 below.

[0059] The preparation method of modified chitosan is as follows: 3 parts of oxidized polyethylene wax emulsion and 5 parts of chitosan are mixed with 2 parts of 0.03 mol / L isopropanol aluminum toluene solution, passed N2 for 12 min, 23°C oil bath, then 11 parts of ε-caprolactone are added, and the reaction is continued for 2.5 hours.

[0060] Example 4

[0061] The difference from Example 1 is that the flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethylammonium chloride, modified chitosan, gelatin, D-adipaldehyde glucose and succinic anhydride, and the content of each component is shown in Table 1 below.

[0062] Gelatin was dissolved in a hot mixture of 3 parts glycerol and 1 part water and heated to 60°C, and then D-adipaldehyde glucose was added, heated to 70°C in a water bath, and stirred for 2 minutes; then succinic anhydride and 4-dimethylaminopyridine were added, and stirring was continued for 50 minutes; finally, the flocculant was prepared by blending with sodium polystyrene sulfonate, methacryloyloxyethyltrimethylammonium chloride and modified chitosan.

[0063] Example 5

[0064] The difference from Example 2 is that the flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethylammonium chloride, modified chitosan, gelatin, D-adipaldehyde glucose and succinic anhydride, and the content of each component is shown in Table 1 below.

[0065] Gelatin was dissolved in a hot mixture of 4 parts of glycerol and 2 parts of water and heated to 60°C, and then D-adipaldehyde glucose was added, heated to 80°C in a water bath, and stirred for 3 minutes; then succinic anhydride and 4-dimethylaminopyridine were added, and stirring was continued for 60 minutes; finally, the flocculant was prepared by blending with sodium polystyrene sulfonate, methacryloyloxyethyltrimethylammonium chloride and modified chitosan.

[0066] Example 6

[0067] The difference from Example 3 is that the flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethylammonium chloride, modified chitosan, gelatin, D-adipaldehyde glucose and succinic anhydride, and the content of each component is shown in Table 1 below.

[0068] Gelatin was dissolved in a hot mixture of 4 parts of glycerol and 2 parts of water and heated to 60°C, and then D-adipaldehyde glucose was added, heated to 75°C in a water bath, and stirred for 3 minutes; then succinic anhydride and 4-dimethylaminopyridine were added, and stirring was continued for 55 minutes; finally, the flocculant was prepared by blending with sodium polystyrene sulfonate, methacryloyloxyethyltrimethylammonium chloride and modified chitosan.

[0069] Example 7

[0070] The difference from Example 1 is that the flocculant in S2 includes the following components: sodium polystyrene sulfonate, methacryloyloxyethyl trimethylammonium chloride, modified chitosan, gelatin and D-adipaldehyde glucose, and the content of each component is shown in Table 2 below.

[0071] Example 8

[0072] The difference from Example 7 is that gelatin is replaced by sodium carboxymethyl cellulose. The contents of each component are shown in Table 2 below.

[0073] Example 9

[0074] The difference from Example 8 is that D-adipaldehyde glucose is replaced by glycerol. The contents of each component are shown in Table 2 below.

[0075] Example 10

[0076] The difference from Example 4 is that succinic anhydride is replaced by acetic acid. The contents of each component are shown in Table 2 below.

[0077] Embodiment 11

[0078] The difference from Example 1 is that, by weight ratio, sodium hydroxide: lime: water = 1:2:4.

[0079] Comparative Example

[0080] Comparative Example 1

[0081] The difference from Example 1 is that the modified chitosan is replaced by chitosan.

[0082] Comparative Example 2

[0083] The difference from Example 1 is that the oxidized polyethylene wax emulsion is replaced by a polyacrylate emulsion.

[0084] Comparative Example 3

[0085] The difference from Comparative Example 2 is that ε-caprolactone is replaced by ethyl acetate.

[0086] Comparative Example 4

[0087] The difference from Example 1 is that, by weight ratio, the oxidized polyethylene wax emulsion: chitosan: ε-caprolactone = 3:4:9, i.e., 3 parts of oxidized polyethylene wax emulsion, 4 parts of chitosan, and 9 parts of ε-caprolactone.

[0088] Table 1 Component contents of Examples 1-6

[0089]

[0090] Table 2 Component contents of Examples 7-10

[0091]

[0092] Performance testing

[0093] Test method: Use sewage with a COD of 100 mg / L as the test sewage to be treated, treat the sewage with the process of the above embodiment and comparative example, determine the COD and calculate the COD removal rate according to the "Water and Wastewater Monitoring and Analysis Method". The higher the removal rate, the better the wastewater treatment effect. The test results are shown in Table 3 below.

[0094] Table 3 Performance test results of various embodiments and comparative examples

[0095] COD removal rate / % Example 1 81 Example 2 85 Example 3 83 Example 4 91 Example 5 95 Example 6 93 Example 7 87 Example 8 84 Example 9 83 Example 10 87 Embodiment 11 85 Comparative Example 1 74 Comparative Example 2 79 Comparative Example 3 75 Comparative Example 4 84

[0096] This specific implementation is merely an explanation of the present application and is not intended to limit the scope of protection of the present application. After reading this specification, those skilled in the art may make modifications to the present implementation as needed without any creative contribution, but as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A pickling wastewater treatment process, characterized in that: The steps include: S1. Neutralization treatment: Mix sodium hydroxide, lime and water to perform preliminary precipitation on the wastewater; S2. Sedimentation treatment; add flocculant to the wastewater after initial precipitation in S1 for treatment, add 7-8 parts of flocculant per ton of wastewater, stir at a stirring speed of 40-80r / min for 8-10min; S3. Oxidation treatment: adjusting the pH in the oxidation tank to 7.0-8.0 for electrolytic oxidation to reduce the concentration of heavy metal ions and iron ions; S4. Biological treatment: The pickling wastewater after precipitation enters the biological treatment tank to convert organic matter into carbon dioxide and water through metabolism; S5. Fine treatment: extract the water in the oxidation tank through a reverse osmosis RO membrane to remove trace heavy metals and salts in the water; The flocculant in S2 includes the following components in parts by weight: 20-30 parts of sodium polystyrene sulfonate; 2-3 parts of methacryloyloxyethyl trimethyl ammonium chloride; 6-8 parts of modified chitosan; The preparation method of the modified chitosan is as follows: 3-4 parts of oxidized polyethylene wax emulsion and 3-6 parts of chitosan are mixed with 1-2 parts of 0.02-0.03 mol / L isopropanol aluminum toluene solution, passed through N2 for 10-15 min, and placed in an oil bath at 20-25° C., then 8-12 parts of ε-caprolactone are added, and the reaction is continued for 2-3 hours.

2. A pickling wastewater treatment process according to claim 1, characterized in that: In terms of weight ratio, the oxidized polyethylene wax emulsion: chitosan: ε-caprolactone = 3:4:

9.

3. A pickling wastewater treatment process according to claim 1, characterized in that: The flocculant further comprises 2-3 parts of gelatin and 4-6 parts of D-adipaldehyde glucose by weight.

4. A pickling wastewater treatment process according to claim 3, characterized in that: The flocculant further comprises 1-2 parts of succinic anhydride and 0.1-0.2 parts of 4-dimethylaminopyridine by weight.

5. A pickling wastewater treatment process according to claim 1, characterized in that: In terms of weight ratio, the sodium hydroxide: lime: water = (1-2): (3-5):

8.

6. A pickling wastewater treatment process according to claim 5, characterized in that: By weight ratio, the sodium hydroxide: lime: water = 1:2:

4.

7. A pickling wastewater treatment process according to claim 1, characterized in that: The pH value of the wastewater in S2 is adjusted to 7-8.

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