A coking wastewater advanced treatment process

Abstract

The application relates to a coking wastewater advanced treatment process, wherein coking wastewater is introduced into an oil separation tank, the pH value is adjusted to 7-8, and a magnetic demulsifier is added; the magnetic demulsifier is recovered, and the effluent is sequentially introduced into a gas floatation tank-coagulation tank-sedimentation tank-flocculation tank to obtain clean water; wherein the magnetic demulsifier is first prepared by taking carbon nanotubes as a carrier, and depositing ferric chloride hexahydrate and copper sulfate pentahydrate on the surface of the carbon nanotubes to obtain magnetic carbon nanotubes, secondly, a hyperbranched polymer with a terminal double bond is prepared, then the two are mixed to obtain hyperbranched grafted magnetic carbon nanotubes, and finally, in-situ polymerization of an allyl polyoxyethylene ether is continuously carried out, and the magnetic demulsifier is obtained. The application simplifies the coking wastewater treatment process, reduces the treatment steps, greatly improves the treatment efficiency, and makes the water quality after the treatment meet the national discharge standard in terms of COD, ammonia nitrogen, cyanide and other indexes; the process route is short, the demulsifier can be recycled, energy consumption is reduced, and economic benefits are remarkable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment materials, and particularly relates to a coking wastewater advanced treatment process. BACKGROUND

[0002] With the rapid development of industrialization, sewage and wastewater discharge is becoming more and more serious. With the increasing emphasis on environmental protection, the requirements for water treatment are also becoming higher and higher. Coking wastewater is a typical toxic and difficult-to-treat industrial organic wastewater. This wastewater contains a large amount of toxic and harmful substances such as phenol, benzene, cyanide, ammonia nitrogen, oil, etc., and has complex composition and high content. The coking wastewater discharged beyond the standard will cause great harm to the environment.

[0003] At present, the water treatment process mainly adopts physical adsorption method, flocculation sedimentation method, activated sludge method, etc. However, for the coking wastewater with complex composition, a single treatment method is difficult to make the coking wastewater meet the discharge standard. At present, different forms of A / O biological denitrification process are generally used as the main process for treating coking wastewater, and coagulation sedimentation, filter membrane and other methods are used as auxiliary methods. However, the treatment process is complicated and time-consuming. In addition to a large amount of organic matter, there is also some oil in the coking wastewater. If the water-oil separation of the coking wastewater can be completed thoroughly in the early stage of treatment, and part of the organic matter is removed, part of the treatment steps can be optimized, and the water treatment efficiency can be improved. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application creatively designs a magnetic demulsifier for coking wastewater. After demulsification, the subsequent treatment of the wastewater only needs coagulation-sedimentation-flocculation to complete the treatment of the coking wastewater, simplifies the treatment process, and greatly improves the treatment efficiency.

[0005] To achieve the above object, the present application provides the following technical scheme:

[0006] A coking wastewater advanced treatment process, comprising the following steps:

[0007] I. The coking wastewater is introduced into an oil separation tank, a pH adjusting agent is first added to adjust the pH value to 7-8, and then a magnetic demulsifier is added to the adjusting tank, and after sufficient mixing, it is placed for 1h;

[0008] II. The clear water at the lower layer of the oil separation tank is introduced into a magnetic separation device, the magnetic demulsifier is recovered, and the water is sent to a flotation tank;

[0009] III. The water outlet of the flotation tank is connected to a coagulation tank, a water purifying agent is added in the coagulation tank, and the treatment is carried out for 30-60min, and then it is introduced into a sedimentation tank for filtration, and then passes through a flocculation tank, and the flocculation is carried out for 5-10min to obtain clean water;

[0010] IV. The water quality of the treated water is tested. When the water quality reaches the discharge standard, the water is directly discharged. When the water quality fails to reach the discharge standard, the water is again treated in the coagulation tank for secondary treatment until the water quality reaches the discharge standard.

[0011] The magnetic demulsifier is prepared by the following steps:

[0012] S1: carbon nanotubes are ultrasonically dispersed in deionized water to form a dispersion liquid, mixed with ferric chloride hexahydrate and copper sulfate pentahydrate and stirred for 10-60 min, then 5-20 wt% ammonia water is added dropwise to adjust the pH to 7-8, and stirred at 90-100°C for 2-10 h. After cooling, the solid product is washed with ethanol and water alternately and then dried, and then calcined at 400-500°C in a nitrogen atmosphere for 1-4 h to prepare magnetic carbon nanotubes;

[0013] S2: xanthate with terminal double bond is used as chain transfer agent, AIBN is used as initiator, and acrylamide is used as reaction monomer to carry out RAFT polymerization under nitrogen atmosphere to prepare hyperbranched polymer;

[0014] S3: the magnetic carbon nanotubes are mixed with amino-functionalized ionic liquid for standby, the hyperbranched polymer is dissolved in DMF, and Michael addition reaction of amino-double bond occurs under catalysis of triethylamine to obtain hyperbranched grafted magnetic carbon nanotubes;

[0015] S4: the hyperbranched grafted magnetic carbon nanotubes are further dispersed in DMF, AIBN is added, nitrogen is introduced to remove air in the system, allyl polyoxyethylene ether is added, and the temperature is raised to 70°C for stirring reaction for 12 h. After the reaction is completed, the solid is precipitated in ice methanol, and then dried to obtain the product.

[0016] Further, in step S1, the amount of ferric chloride hexahydrate and copper sulfate pentahydrate is n(Fe 3+ ):n(Cu 2 + )=2:1, and the total mass of the two is 5-10 times the mass of the carbon nanotubes.

[0017] Further, in step S2, the structural formula of the xanthate with terminal double bond is The molar ratio of the RAFT chain transfer agent, the initiator, and the reaction monomer is 1:0.01:50-100.

[0018] Further, in step S3, the amino-functionalized ionic liquid is selected from one of 1-aminopropyl-3-methylimidazolium nitrate, 1-aminopropyl-3-methylimidazolium bromide, 1- aminoethyl-3-methylimidazolium nitrate, and 1-aminoethyl-3-methylimidazolium bromide.

[0019] Further, in the step S3, the mass ratio of the magnetic carbon nanotube, the amino-functionalized ionic liquid and the hyperbranched grafted magnetic carbon nanotube is 1:3:3-10.

[0020] Further, in the step S4, the molecular weight of the allyl polyoxyethylene ether ranges from 300 to 600, and the mass ratio of the allyl polyoxyethylene ether to the hyperbranched grafted magnetic carbon nanotube is 0.5-1:1.

[0021] Coking wastewater mainly comes from the initial cooling of coke oven gas and the production water in the coking production process, the pollutant concentration in the wastewater is high, and the composition is complex, at present, the treatment of coking wastewater mainly focuses on the removal of organic pollutants, but a small amount of oil exists in the coking wastewater, which affects the treatment efficiency. Therefore, the application expects to be able to demulsify and remove oil from the coking wastewater before coagulation treatment or biochemical treatment, on the basis of oil removal, the COD content of the wastewater is reduced, and the subsequent treatment is much easier. However, due to the too complex composition of the coking wastewater and the relatively low oil content, it is difficult for ordinary demulsifiers to capture oil molecules to make them quickly emulsify and stratify. Therefore, the application prepares a demulsifier for coking wastewater.

[0022] Firstly, the application uses multi-walled carbon nanotubes (CNTs) as a carrier, and in-situ deposition of copper-doped magnetic nanomaterial CuFe2O4 is synthesized on the CNTs by virtue of the rich pore structure of the CNTs, and the magnetic nanomaterial has been proved to be a substance with higher magnetic stability than Fe3O4; the obtained magnetic carbon nanotubes are mixed with an amino-functionalized ionic liquid, there is a π-π interaction between the ionic liquid and the CNTs, then a Michael addition reaction is carried out between the amino group in the ionic liquid and the hyperbranched polymer containing a double bond at the end, so as to coat a layer of organic polymer on the surface of the magnetic carbon nanotubes, improve the hydrophilicity of the material, and then the dispersibility of the carbon nanotubes in the water body can be effectively improved, and the contact area is increased; finally, by taking advantage of the characteristics of active radical polymerization, allyl polyoxyethylene ether (APEG) is continuously polymerized outside the hyperbranched polymer, and a magnetic demulsifier with a multi-branched polyether structure and taking the magnetic carbon nanotube as a carrier is formed. The polyether with a multi-branched structure of the application can form a net trapping effect in the water body, so that oil and water can quickly gather and separate in the emulsified state, and the oil removal rate can reach more than 95%; at the same time, the demulsifier has magnetism, and after being recovered by magnetic separation, it can be recycled, and after ten cycles of demulsification-recovery-demulsification, the oil removal rate can still reach more than 92%; the addition amount is small and the oil removal effect is good, which simplifies the treatment process of the coking wastewater.

[0023] Compared with the prior art, the application has the advantages that the treatment process of the coking wastewater is simplified, the treatment steps are less, and the treatment efficiency is greatly improved; the water quality after the treatment by the process of the application can meet the national discharge standard in terms of COD, ammonia nitrogen, cyanide and other indicators, the process route is short, the demulsifier can be recycled, energy consumption is reduced, and the economic benefit is remarkable. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0025] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0026] Embodiment: a coking wastewater advanced treatment process

[0027] I. The coking wastewater is introduced into an oil separation tank, a pH regulator is first added to adjust the pH value to 7-8, and then a magnetic demulsifier is added to the adjustment tank, and after sufficient mixing, it is left for 1 h;

[0028] II. The clear water at the bottom of the oil separation tank is introduced into a magnetic separation device to recover the magnetic demulsifier, and the effluent is sent to a flotation tank;

[0029] III. The effluent outlet of the flotation tank is connected to a coagulation tank, a water purifying agent is added in the coagulation tank, and the treatment is carried out for 30-60 min, and then it is introduced into a sedimentation tank for filtration, and then through a flocculation tank, and flocculation for 5-10 min, to obtain clean water;

[0030] IV. The water quality of the clean water is tested, and after reaching the discharge standard, it is directly discharged, and if it fails to reach the discharge standard, it is introduced into the coagulation tank again for secondary treatment until the discharge standard is reached.

[0031] The magnetic demulsifier in the present application is a self-made material, and the water purifying agent can be selected from commercially available products. In the present case, the water purifying agent suitable for advanced treatment of coal chemical and coking industrial wastewater in the applicant's invention patent CN106745818B is selected.

[0032] The above treatment process is used to treat a certain coking wastewater, and the water quality of the coking wastewater is as follows: COD content 7500 mg / L, oil content 85 mg / L, ammonia nitrogen 530 mg / L, phenol 320 mg / L, and cyanide 25 mg / L.

[0033] Example 1

[0034] I. The coking wastewater is introduced into an oil separation tank, a pH regulator is first added to adjust the pH value to 7-8, and then a magnetic demulsifier is added to the adjustment tank, and after sufficient mixing, it is left for 1 h;

[0035] The magnetic demulsifier is prepared by the following steps:

[0036] S1: 10g of carbon nanotubes were ultrasonically dispersed in deionized water to form a dispersion, which was then mixed with 200ml of 0.8mol / L ferric chloride hexahydrate and 100ml of 0.8mol / L copper sulfate pentahydrate and stirred for 10-60min. Then, 5-20wt% ammonia was added dropwise to adjust the pH to 7-8. The mixture was stirred and reacted at 90-100℃ for 5h. After cooling, the mixture was filtered. The solid product was washed alternately with ethanol and water and then dried. Finally, it was calcined at 400℃ in a nitrogen atmosphere for 2h to obtain magnetic carbon nanotubes.

[0037] S2: Xanthate with terminal double bonds (Reference: Polym. Chem., 2011, 2, 2231-2238. Synthesis, hereinafter referred to as RAFT reagent) as chain transfer agent, AIBN as initiator, acrylamide as reactant monomer, molar ratio of 1:0.01:50, all substances were added to a Schlenk flask, tetrahydrofuran was added as solvent, nitrogen gas was introduced, and the reaction was carried out at 70℃ for 3-5 h under nitrogen atmosphere to obtain hyperbranched polymer;

[0038] S3: Mix 5g of magnetic carbon nanotubes with 15g of 1-aminopropyl-3-methylimidazolium nitrate for later use. Dissolve 15g of hyperbranched polymer in DMF, add 2g of triethylamine, and react at room temperature for 3h to obtain hyperbranched grafted magnetic carbon nanotubes.

[0039] S4: The hyperbranched grafted magnetic carbon nanotubes were further dispersed in DMF, 0.5 times the amount of APEG300 was added, and the amount of AIBN was added as a catalyst. Nitrogen gas was introduced to remove air from the system, and the temperature was raised to 70°C and stirred for 12 hours. After the reaction was completed, the solid was precipitated in ice-cold methanol and dried to obtain the magnetic demulsifier.

[0040] 2. Pass the clear water from the bottom layer of the oil separator into the magnetic separation equipment to recover the magnetic demulsifier, and send the effluent into the air flotation tank.

[0041] 3. Connect the outlet of the flotation tank to the coagulation tank, add water purification agent to the coagulation tank, treat for 30-60 minutes, then pass it into the sedimentation tank for filtration, and then pass it into the flocculation tank for flocculation for 5-10 minutes to obtain purified water.

[0042] IV. Test the water quality of the purified water: COD content < 50 mg / L, oil < 0.5 mg / L, ammonia nitrogen < 5 mg / L, phenol < 0.3 mg / L, cyanide < 0.2 mg / L. After one complete treatment process, it can meet the national discharge standards.

[0043] Example 2:

[0044] 1. Pass the coking wastewater into the oil separator. First, add pH adjuster to adjust the pH value to 7-8. Then, add magnetic demulsifier to the equalization tank, mix thoroughly, and let stand for 1 hour.

[0045] wherein the magnetic demulsifier is prepared by the following steps:

[0046] S1: 10g carbon nanotubes are ultrasonically dispersed in deionized water to form a dispersion liquid, mixed with 200ml 0.8mol / L ferric chloride hexahydrate, 100ml 0.8mol / L copper sulfate pentahydrate, stirred for 10-60min, then 5-20wt% ammonia water is added dropwise, the pH is adjusted to 7-8, stirred at 90-100℃ for 5h, cooled and filtered, the solid product is washed with ethanol and water alternately, then dried, and then calcined at 400℃ under nitrogen atmosphere for 2h to prepare magnetic carbon nanotubes;

[0047] S2: n(RAFT reagent: AIBN: acrylamide) = 1:0.01:60, all substances are added to a Schlenk flask, tetrahydrofuran is added as a solvent, nitrogen is introduced, and the temperature is raised to 70℃ under nitrogen atmosphere for 3-5h to prepare a hyperbranched polymer;

[0048] S3: 5g magnetic carbon nanotubes are mixed with 15g 1-aminopropyl-3-methyl imidazole nitrate for standby, 17g hyperbranched polymer is dissolved in DMF, 2g triethylamine is added, and the reaction is carried out at room temperature for 3h to obtain hyperbranched grafted magnetic carbon nanotubes;

[0049] S4: the hyperbranched grafted magnetic carbon nanotubes are further dispersed in DMF, 0.5 times the amount of APEG300 is added, a catalytic amount of AIBN is added, nitrogen is introduced to remove air in the system, the temperature is raised to 70℃ and stirred for 12h, and after the reaction is completed, the solid is precipitated in ice methanol, and after drying, the magnetic demulsifier is obtained.

[0050] II. The clear water at the lower layer of the oil separation tank is introduced into the magnetic separation equipment, the magnetic demulsifier is recovered, and the effluent is sent to the air flotation tank;

[0051] III. The effluent from the air flotation tank is connected to the coagulation tank, a water purifying agent is added to the coagulation tank, treated for 30-60min, then introduced into the sedimentation tank for filtration, and then passed through the flocculation tank, and flocculated for 5-10min to obtain clean water;

[0052] IV. The water quality of the clean water is tested, the COD content is <40mg / L, the oil is <0.5mg / L, the ammonia nitrogen is <5mg / L, the phenol is <0.3mg / L, and the cyanide is <0.2mg / L. After one complete process treatment, the national discharge standard can be reached.

[0053] Example 3:

[0054] I. The coking wastewater is introduced into the oil separation tank, first a pH adjusting agent is added to adjust the pH value to 7-8, then the magnetic demulsifier is added to the adjustment tank, mixed thoroughly, and then left to stand for 1h;

[0055] The magnetic demulsifier is prepared by the following steps:

[0056] S1: 10 g of carbon nanotubes are ultrasonically dispersed in deionized water to form a dispersion liquid, mixed with 200 ml of 0.8 mol / L ferric chloride hexahydrate and 100 ml of 0.8 mol / L copper sulfate pentahydrate and stirred for 10-60 min, then 5-20 wt% ammonia water is added dropwise, the pH is adjusted to 7-8, and the reaction is stirred at 90-100°C for 5 h, then filtered after cooling, the solid product is washed with ethanol and water alternately, then dried, and then calcined at 400°C for 2 h in a nitrogen atmosphere to prepare magnetic carbon nanotubes;

[0057] S2: n(RAFT reagent: AIBN: acrylamide) = 1:0.01:70, all substances are added to a Schlenk flask, tetrahydrofuran is added as a solvent, nitrogen is introduced, and the temperature is raised to 70°C under a nitrogen atmosphere for 3-5 h to prepare a hyperbranched polymer;

[0058] S3: 5 g of magnetic carbon nanotubes are mixed with 15 g of 1-aminopropyl-3-methyl imidazole bromide for use, 20 g of hyperbranched polymer is dissolved in DMF, 2 g of triethylamine is added, and the reaction is carried out at room temperature for 3 h to obtain hyperbranched grafted magnetic carbon nanotubes;

[0059] S4: The hyperbranched grafted magnetic carbon nanotubes are further dispersed in DMF, 0.8 times the amount of APEG400 is added, a catalytic amount of AIBN is added, nitrogen is introduced to remove air in the system, the temperature is raised to 70°C, and the reaction is stirred for 12 h. After the reaction is completed, the solid is precipitated in ice methanol, and after drying, the magnetic demulsifier is obtained.

[0060] II. The clear water at the bottom of the oil separation tank is introduced into the magnetic separation equipment, and the magnetic demulsifier is recovered. The effluent is introduced into the air flotation tank;

[0061] III. The effluent from the air flotation tank is introduced into the coagulation tank, and a water purifying agent is added. After 30-60 min of treatment, the effluent is introduced into the sedimentation tank for filtration, and then introduced into the flocculation tank for flocculation for 5-10 min to obtain purified water.

[0062] IV. The water quality of the purified water is tested, and the COD content is <40 mg / L, the oil is <0.3 mg / L, the ammonia nitrogen is <4 mg / L, the phenol is <0.2 mg / L, and the cyanide is <0.2 mg / L. After one complete process, the national discharge standard is reached.

[0063] Comparative Example 1:

[0064] Compared with Example 1, no demulsifier treatment is performed.

[0065] The water quality of the treated water is tested, and the COD content is less than 1000 mg / L, the oil is less than 80 mg / L, the ammonia nitrogen is less than 70 mg / L, the phenol is less than 40 mg / L, and the cyanogen is less than 5 mg / L. The first treatment fails to reach the national discharge standard.

[0066] While embodiments of the application have been disclosed in connection with the above specification and drawings, it will be understood by those skilled in the art that many modifications, additions, substitutions, and deletions can be made to the disclosed embodiments without departing from the scope and spirit of the application. Accordingly, the application is not to be limited by the foregoing description, but is to be understood in its broadest possible scope in connection with the drawings and the specification.

Claims

1. A deep treatment process for coking wastewater, characterized in that, Includes the following steps:

1. Pass the coking wastewater into the oil separator. First, add pH adjuster to adjust the pH value to 7-8. Then, add magnetic demulsifier to the equalization tank, mix thoroughly, and let stand for 1 hour.

2. Pass the clear water from the bottom layer of the oil separator into the magnetic separation equipment to recover the magnetic demulsifier, and send the effluent into the air flotation tank.

3. Connect the outlet of the flotation tank to the coagulation tank, add water purification agent to the coagulation tank, treat for 30-60 minutes, then pass it into the sedimentation tank for filtration, and then pass it into the flocculation tank for flocculation for 5-10 minutes to obtain purified water. IV. Test the water quality of the purified water. If it meets the discharge standard, it will be discharged directly. If it fails to meet the discharge standard, it will be fed into the coagulation tank for secondary treatment until it meets the discharge standard. The magnetic demulsifier is prepared through the following steps: S1: Disperse carbon nanotubes ultrasonically in deionized water to form a dispersion. Mix this dispersion with ferric chloride hexahydrate and copper sulfate pentahydrate and stir for 10-60 min. Then, add 5-20 wt% ammonia solution dropwise to adjust the pH to 7-8. Maintain a pH of 90-100. o The reaction was stirred at C for 2–10 h, cooled, filtered, and the solid product was washed alternately with ethanol and water, dried, and then dried at 400–500 °C. o Magnetic carbon nanotubes were obtained by calcination in a nitrogen atmosphere at C for 1-4 hours. S2: Hyperbranched polymers were prepared by RAFT polymerization using xanthate with terminal double bonds as chain transfer agents, AIBN as initiator, and acrylamide as reactant monomer under a nitrogen atmosphere. S3: Mix magnetic carbon nanotubes with amino-functionalized ionic liquid for later use. Dissolve hyperbranched polymer in DMF and undergo Michael addition reaction of amino-double bond under triethylamine catalysis to obtain hyperbranched grafted magnetic carbon nanotubes. S4: Continue to disperse the hyperbranched grafted magnetic carbon nanotubes in DMF, add AIBN, purge the system with nitrogen to remove air, add allyl polyoxyethylene ether, and heat to 70°C. o C. Stir the reaction for 12 hours. After the reaction is complete, a solid precipitates in ice-cold methanol. After drying, the product is obtained. The structural formula of the xanthate ester with terminal double bonds is as follows: .

2. The deep treatment process for coking wastewater according to claim 1, characterized in that, In step S1, the amounts of ferric chloride hexahydrate and copper sulfate pentahydrate are determined according to n(Fe 3+ ):n(Cu 2+ The ratio of the total mass of the nanotubes to the total mass of the carbon nanotubes is 2:1, and the ratio of their total mass to the mass of the carbon nanotubes is 5 to 10:

1.

3. The deep treatment process for coking wastewater according to claim 1, characterized in that, In step S2, the molar ratio of chain transfer agent, initiator, and reactant monomer is 1:0.01:50 to 100.

4. The deep treatment process for coking wastewater according to claim 1, characterized in that, In step S3, the amino-functionalized ionic liquid is selected from one of 1-aminopropyl-3-methylimidazolium nitrate, 1-aminopropyl-3-methylimidazolium bromide, 1-aminoethyl-3-methylimidazolium nitrate, and 1-aminoethyl-3-methylimidazolium bromide.

5. The deep treatment process for coking wastewater according to claim 1, characterized in that, In step S3, the mass ratio of magnetic carbon nanotubes, amino-functionalized ionic liquids, and hyperbranched grafted magnetic carbon nanotubes is 1:3:3 to 10.

6. The deep treatment process for coking wastewater according to claim 1, characterized in that, In step S4, the molecular weight of allyl polyoxyethylene ether ranges from 300 to 600, and its mass ratio to hyperbranched grafted magnetic carbon nanotubes is 0.5 to 1:1.

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