A method for treating fluoride-containing wastewater

Abstract

This invention discloses a method for treating fluoride-containing wastewater, belonging to the field of environmental protection. The grafted functional groups of zinc bromide, ferrocene, and bisphenol groups in this invention have the ability to specifically recognize fluoride ions, binding to them and thus capturing fluoride ions from the wastewater. The ultrafiltration membrane, acting as a physical barrier, prevents unadsorbed fluoride ions and other impurities from passing through, thereby achieving selective removal of trace fluoride ions from the wastewater. The ferrocene and bisphenol groups can form stable complexes with fluoride ions, effectively removing them from the wastewater. Through this submerged ultrafiltration membrane grafted with zinc bromide, ferrocene, and bisphenol groups, highly efficient removal of trace fluoride ions from wastewater used in the preparation of hexafluoropropylene can be achieved. The advantages of this method include high selectivity, low energy consumption, and low cost, making it of significant application value for treating similar wastewater problems in actual production.

Description

Technical Field

[0001] This invention relates to the field of environmental protection, and in particular to a method for treating fluoride-containing wastewater. Background Technology

[0002] China has a history of over forty years in hexafluoropropylene production, and has made great progress in production technology and waste treatment technology. However, manufacturers often prioritize product quality and manufacturing technology while neglecting the treatment and comprehensive utilization of waste generated during production, resulting in waste treatment technology lagging behind production technology.

[0003] Chinese Patent CN117023750B discloses a method for treating fluoride-containing wastewater, belonging to the field of fluoride-containing wastewater treatment technology. The method includes: fluoride-containing wastewater entering an equalization tank, where it is homogenized and equalized to obtain equalization tank effluent; the equalization tank effluent entering a primary reaction tank, where calcium hydroxide and a composite flocculant are added for reaction; the primary reaction tank effluent entering a primary sedimentation tank for sludge-water separation to obtain primary sedimentation tank effluent; the primary sedimentation tank effluent entering a secondary reaction tank, where a composite flocculant is added for reaction; the secondary reaction tank effluent entering a secondary sedimentation tank for sludge-water separation to obtain secondary sedimentation tank effluent; the composite flocculant includes inorganic flocculants and organic flocculants, the organic flocculant being a copolymer composed of acrylamide units and alkenyl quaternary ammonium salt units, or composed of acrylamide units, alkenyl quaternary ammonium salt units, and N-vinylpyrrolidone units.

[0004] Chinese Patent CN116874136A: Provides a treatment system and method for fluoride-containing wastewater, and its application, relating to the technical field of wastewater treatment. The treatment system includes a fluidized bed crystallization system, a circulation tank, a tubular membrane system, and a bipolar membrane electrodialysis system connected in sequence.

[0005] Chinese Patent CN116730562A discloses a treatment process and production line for fluoride-containing wastewater. It includes a six-step process: buffering, sedimentation, flocculation, sedimentation and conditioning, filtration, and recovery and reuse. The production line also includes a conditioning tank, a coagulation sedimentation tank, a filtration device, an RO device, and an MVR high-efficiency evaporator. The synergistic effect between each step of the production line achieves low-cost, high-efficiency, and stable treatment of fluoride-containing wastewater.

[0006] The above-mentioned patented and existing technologies for treating fluoride-containing wastewater have problems such as large investment, many equipment, complex processes, and high treatment costs. In addition, the concentration of fluoride ions after treatment is too high and unstable. Summary of the Invention Summary of the Invention

[0008] To address the above problems, this invention provides a method for treating fluoride-containing wastewater, the operation steps of which are as follows:

[0009] S1: By weight, send 100-200 parts of fluoride-containing wastewater with a concentration of 500-600 mg / L to a sedimentation tank, add 1-3 parts of flocculant and 0.3-3 parts of defluoridating agent, stir, let stand, filter, and remove most of the fluoride. - CO3 2- ;

[0010] S2: Add pH adjuster to the clear liquid after S1 filtration to control the pH of the solution to 7-8;

[0011] S3: Send the clarified liquid after S2pH adjustment into the flocculation sedimentation tank, add 0.3-3 parts of flocculant, and after flocculation sedimentation, filter;

[0012] S4: Membrane filtration system treatment: The water filtered by S3 is kept in the submerged membrane filtration system for 30-60 minutes; the submerged membrane filtration system uses a modified submerged ultrafiltration membrane with a curtain structure.

[0013] S5: The clarified liquid after treatment by the membrane filtration system is sent to the biological contact oxidation tank for further treatment. The clarified liquid is used to recover the KOH solution.

[0014] The method for preparing the modified submerged ultrafiltration membrane is as follows:

[0015] H1: Immerse the submerged ultrafiltration membrane in methyl 3-mercaptopropionate at 25°C for 60-100 min, and then initiate the grafting reaction with plasma glow discharge under an argon atmosphere at a flow rate of 20-30 ml / min. The external electrode glow discharge power is 100-200 W, the treatment time is 5-15 min, and the membrane is removed and dried to obtain the mercapto submerged ultrafiltration membrane.

[0016] H2: By weight, 100-200 parts of the mercapto-immersed ultrafiltration membrane prepared according to the above steps are placed into 1000-1500 parts of DMF, and then 10-16 parts of diallyl bisphenol, 3-6 parts of allyl zinc bromide, 0.03-0.6 parts of (6-mercaptohexyl)ferrocene, and 3-6 parts of triethanolamine are added. The mixture is stirred evenly and soaked at 65-75℃ for 2-4 hours. The ultrafiltration membrane is then removed and dried in an ultra-clean room, and then placed in a constant temperature drying oven for 10-20 hours. The surface grafting reaction is then carried out using plasma glow discharge method, with the same power as before and a processing time of 20-50 seconds, to obtain the modified immersed ultrafiltration membrane.

[0017] The fluoride-containing wastewater mentioned is wastewater from the preparation of hexafluoropropylene;

[0018] The precipitant is 10-20% quicklime slurry.

[0019] As a preferred embodiment of the present invention, the defluorinating agent is one or more of magnesium hydroxide, sodium persulfate, sulfuric acid, hydrochloric acid, acrylamide, diethylenetriamine, and ethylenediamine.

[0020] As a preferred embodiment of the present invention, the pH adjuster is a hydrochloric acid solution with a mass concentration of 10-20%.

[0021] As a preferred embodiment of the present invention, the flocculant is one or more of polyaluminum chloride, aluminum hydroxide, aluminum oxide, and aluminum chloride.

[0022] As a preferred embodiment of the present invention, the operating conditions of the biological contact oxidation tank are as follows: the residence time of the biological contact oxidation tank is 6-12h and the temperature is 15-35℃.

[0023] Mechanism of this scheme: The mercapto-immersed ultrafiltration membrane undergoes a mercapto-olefin addition reaction with diallyl bisphenol or allyl zinc bromide; (6-mercaptohexyl)ferrocene undergoes a mercapto-olefin addition reaction with diallyl bisphenol or allyl zinc bromide, and the resulting immersed ultrafiltration membrane is grafted with functional groups such as zinc bromide, ferrocene, and bisphenol, which can remove trace amounts of fluoride ions from the wastewater used to prepare hexafluoropropylene through membrane adsorption and filtration.

[0024] The present invention provides a method for treating fluoride-containing wastewater, which has the following significant advantages compared with the prior art:

[0025] 1. This invention removes fluoride ions from wastewater used in the preparation of hexafluoropropylene through precipitation, flocculation sedimentation, and biological contact oxidation; the wastewater treated by this invention can be directly discharged.

[0026] 2. This invention can recover the KOH solution from the wastewater used in the preparation of hexafluoropropylene as a by-product, thereby increasing its economic value;

[0027] 3. This invention requires little investment, few equipment, has a simple process, low processing cost, and produces a relatively stable fluoride ion concentration after treatment.

[0028] 4. The grafted functional groups of zinc bromide, ferrocene, and bisphenol groups in this invention have the ability to specifically recognize fluoride ions. They can bind with fluoride ions, thereby capturing fluoride ions from wastewater. The ultrafiltration membrane, as a physical barrier, can prevent unadsorbed fluoride ions and other impurities from passing through, thereby achieving selective removal of trace fluoride ions from wastewater. The ferrocene and bisphenol groups can form stable complexes with fluoride ions, thereby effectively removing fluoride ions from wastewater. Through this submerged ultrafiltration membrane grafted with zinc bromide, ferrocene, and bisphenol groups, highly efficient removal of trace fluoride ions from wastewater used in the preparation of hexafluoropropylene can be achieved. The advantages of this method include high selectivity, low energy consumption, and low cost, and it has important application value for treating similar wastewater problems in actual production. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with embodiments, is provided below.

[0030] The fluoride ion concentration was determined according to the "Determination of Fluoride in Water - Ion Selective Electrode Method" (GB7484-87).

[0031] Composition of raw material hexafluoropropylene wastewater:

[0032] KF / % <![CDATA[K2CO3 / %]]> KOH / % <![CDATA[H2O / %]]> hexafluoropropylene wastewater 18.6 17.1 4.8 59.5 Example 1

[0033] A method for treating fluoride-containing wastewater, comprising the following steps:

[0034] S1: Send 100g of fluoride-containing wastewater with a concentration of 500mg / L to a sedimentation tank, add 1g of flocculant and 0.3g of defluorinating agent, stir, let stand, filter, and remove most of the fluoride. - CO3 2- ;

[0035] S2: Add pH adjuster to the clear liquid after precipitation to control the pH of the solution to 7;

[0036] S3: The clear liquid after sedimentation is sent to the flocculation sedimentation tank, 0.3g of flocculant is added, and after flocculation sedimentation, it is filtered;

[0037] S4: Membrane filtration system treatment: Water stays in the submerged membrane filtration system for 30 minutes; the submerged membrane filtration system uses a modified submerged ultrafiltration membrane with a curtain structure.

[0038] S5: The clarified liquid after flocculation and sedimentation is sent to the biological contact oxidation tank for treatment, and the clarified liquid is used to recover KOH solution.

[0039] The fluoride-containing wastewater is wastewater from the preparation of hexafluoropropylene.

[0040] The precipitant is 10% quicklime slurry.

[0041] The defluorinating agent is magnesium hydroxide.

[0042] The pH adjuster is a 10% hydrochloric acid solution.

[0043] The flocculant mentioned is polyaluminum chloride.

[0044] The operating conditions of the biological contact oxidation tank are: a residence time of 6 hours and a temperature of 15°C.

[0045] The method for preparing the modified submerged ultrafiltration membrane is as follows:

[0046] H1: The submerged ultrafiltration membrane was immersed in methyl 3-mercaptopropionate at 25°C for 60 min, and then the grafting reaction was initiated by plasma glow discharge under argon atmosphere (20 ml / min). The external electrode glow discharge power was 100 W and the treatment time was 5 min. The membrane was then removed and dried to obtain the mercapto submerged ultrafiltration membrane.

[0047] H2: Place 100g of the mercapto-immersed ultrafiltration membrane prepared according to the above steps into 1000g of DMF, then add 10g of diallyl bisphenol, 3g of allyl zinc bromide, 0.03g of (6-mercaptohexyl)ferrocene, and 3g of triethanolamine. Stir well and soak at 65℃ for 2h. Remove the ultrafiltration membrane and air dry it in an ultra-clean room, then place it in a constant temperature drying oven for 10h. Then, perform a surface grafting reaction using plasma glow discharge method, with the same power as before and a processing time of 20s, to obtain the modified immersed ultrafiltration membrane.

[0048] Example 2

[0049] A method for treating fluoride-containing wastewater, comprising the following steps:

[0050] S1: Send 140g of fluoride-containing wastewater with a concentration of 540mg / L to a sedimentation tank, add 2g of flocculant and 1g of defluoridating agent, stir, let stand, filter, and remove most of the fluoride. - CO3 2- ;

[0051] S2: Add pH adjuster to the clear liquid after precipitation to control the pH of the solution to 7;

[0052] S3: The clear liquid after sedimentation is sent to the flocculation sedimentation tank, 1g of flocculant is added, and after flocculation sedimentation, it is filtered;

[0053] S4: Membrane filtration system treatment: Water stays in the submerged membrane filtration system for 40 minutes; the submerged membrane filtration system uses a modified submerged ultrafiltration membrane with a curtain structure.

[0054] S5: The clarified liquid after flocculation and sedimentation is sent to the biological contact oxidation tank for treatment, and the clarified liquid is used to recover KOH solution.

[0055] The fluoride-containing wastewater is wastewater from the preparation of hexafluoropropylene.

[0056] The precipitant is 15% quicklime slurry.

[0057] The defluorinating agent is sodium persulfate.

[0058] The pH adjuster is a 15% hydrochloric acid solution.

[0059] The flocculant mentioned is aluminum hydroxide.

[0060] The operating conditions of the biological contact oxidation tank are: a residence time of 8 hours and a temperature of 20°C.

[0061] The method for preparing the modified submerged ultrafiltration membrane is as follows:

[0062] H1: The submerged ultrafiltration membrane was immersed in methyl 3-mercaptopropionate at 25°C for 70 min, and then the grafting reaction was initiated by plasma glow discharge under argon atmosphere (23 ml / min). The external electrode glow discharge power was 140 W and the treatment time was 8 min. The membrane was then removed and dried to obtain the mercapto submerged ultrafiltration membrane.

[0063] H2: Place 130g of the mercapto-immersed ultrafiltration membrane prepared according to the above steps into 1100g of DMF, then add 12g of diallyl bisphenol, 4g of allyl zinc bromide, 0.2g of (6-mercaptohexyl)ferrocene, and 4g of triethanolamine. Stir well and soak at 70℃ for 3h. Remove the ultrafiltration membrane and air dry it in a clean room, then place it in a constant temperature drying oven for 14h. Then, perform a surface grafting reaction using plasma glow discharge method, with the same power as before and a treatment time of 30s, to obtain the modified immersed ultrafiltration membrane.

[0064] Example 3

[0065] A method for treating fluoride-containing wastewater, comprising the following steps:

[0066] S1: Send 180g of fluoride-containing wastewater with a concentration of 580mg / L to a sedimentation tank, add 2g of flocculant and 2g of defluoridating agent, stir, let stand, filter, and remove most of the fluoride. - CO3 2- ;

[0067] S2: Add pH adjuster to the clear liquid after precipitation to control the pH of the solution to 8;

[0068] S3: The clear liquid after sedimentation is sent to the flocculation sedimentation tank, 2g of flocculant is added, and after flocculation sedimentation, it is filtered;

[0069] S4: Membrane filtration system treatment: Water stays in the submerged membrane filtration system for 50 minutes; the submerged membrane filtration system uses a modified submerged ultrafiltration membrane with a curtain structure.

[0070] S5: The clarified liquid after flocculation and sedimentation is sent to the biological contact oxidation tank for treatment, and the clarified liquid is used to recover KOH solution.

[0071] The fluoride-containing wastewater is wastewater from the preparation of hexafluoropropylene.

[0072] The precipitant is 15% quicklime slurry.

[0073] The defluorinating agent is sulfuric acid.

[0074] The pH adjuster is a 15% hydrochloric acid solution.

[0075] The flocculant mentioned is aluminum oxide.

[0076] The operating conditions of the biological contact oxidation tank are: a residence time of 10 hours and a temperature of 30°C.

[0077] The method for preparing the modified submerged ultrafiltration membrane is as follows:

[0078] H1: The submerged ultrafiltration membrane was immersed in methyl 3-mercaptopropionate at 25°C for 90 min, and then the grafting reaction was initiated by plasma glow discharge under argon atmosphere (25 ml / min). The external electrode glow discharge power was 180 W and the treatment time was 13 min. The membrane was then removed and dried to obtain the mercapto submerged ultrafiltration membrane.

[0079] H2: Place 180g of the mercapto-immersed ultrafiltration membrane prepared according to the above steps into 1400g of DMF, then add 14g of diallyl bisphenol, 5g of allyl zinc bromide, 0.4g of (6-mercaptohexyl)ferrocene, and 5g of triethanolamine. Stir well and soak at 70℃ for 3h. Remove the ultrafiltration membrane and air dry it in a clean room, then place it in a constant temperature drying oven for 18h. Then, perform a surface grafting reaction using plasma glow discharge method, with the same power as before and a processing time of 40s, to obtain the modified immersed ultrafiltration membrane.

[0080] Example 4

[0081] A method for treating fluoride-containing wastewater, comprising the following steps:

[0082] S1: Send 200g of fluoride-containing wastewater with a concentration of 600mg / L to a sedimentation tank, add 3g of flocculant and 3g of defluoridating agent, stir, let stand, filter, and remove most of the fluoride. - CO3 2- ;

[0083] S2: Add pH adjuster to the clear liquid after precipitation to control the pH of the solution to 8;

[0084] S3: The clear liquid after sedimentation is sent to the flocculation sedimentation tank, 3g of flocculant is added, and after flocculation sedimentation, it is filtered;

[0085] S4: Membrane filtration system treatment: Water stays in the submerged membrane filtration system for 60 minutes; the submerged membrane filtration system uses a modified submerged ultrafiltration membrane with a curtain structure.

[0086] S5: The clarified liquid after flocculation and sedimentation is sent to the biological contact oxidation tank for treatment, and the clarified liquid is used to recover KOH solution.

[0087] The fluoride-containing wastewater is wastewater from the preparation of hexafluoropropylene.

[0088] The precipitant is 20% quicklime slurry.

[0089] The defluorinating agent is ethylenediamine.

[0090] The pH adjuster is a 20% hydrochloric acid solution.

[0091] The flocculant mentioned is aluminum chloride.

[0092] The operating conditions of the biological contact oxidation tank are: a residence time of 12 hours and a temperature of 35°C.

[0093] The method for preparing the modified submerged ultrafiltration membrane is as follows:

[0094] H1: The submerged ultrafiltration membrane was immersed in methyl 3-mercaptopropionate at 25°C for 100 min, and then the grafting reaction was initiated by plasma glow discharge under argon atmosphere (30 ml / min). The external electrode glow discharge power was 200 W and the treatment time was 15 min. The membrane was then removed and dried to obtain the mercapto submerged ultrafiltration membrane.

[0095] H2: Place 200g of the mercapto-immersed ultrafiltration membrane prepared according to the above steps into 1500g of DMF, then add 16g of diallyl bisphenol, 6g of allyl zinc bromide, 0.6g of (6-mercaptohexyl)ferrocene, and 6g of triethanolamine. Stir well and soak at 75℃ for 4h. Remove the ultrafiltration membrane and air dry it in a clean room, then place it in a constant temperature drying oven for 20h. Then, perform a surface grafting reaction using plasma glow discharge method, with the same power as before and a processing time of 50s, to obtain the modified immersed ultrafiltration membrane.

[0096] Comparative Example 1

[0097] This comparative example is identical to Example 1 except that diallyl bisphenol is not added.

[0098] Comparative Example 2

[0099] This comparative example is identical to Example 1 except that allyl zinc bromide is not added.

[0100] Comparative Example 3

[0101] This comparative example is identical to Example 1 except that (6-mercaptohexyl)ferrocene is not added.

[0102] Test results:

[0103] Fluoride ion concentration / mg / L Example 1 0.018 Example 2 0.013 Example 3 0.006 Example 4 0.005 Comparative Example 1 7.13 Comparative Example 2 5.87 Comparative Example 3 4.15

[0104] Based on the data analysis of the above embodiments and comparative examples, the wastewater treated by the present invention can be directly discharged.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for treating fluoride-containing wastewater, comprising the following steps: S1: By weight, send 100-200 parts of fluoride-containing wastewater with a concentration of 500-600 mg / L to a sedimentation tank, add 1-3 parts of flocculant and 0.3-3 parts of defluoridating agent, stir, let stand, filter, and remove most of the fluoride. - CO3 2- ; S2: Add pH adjuster to the clear liquid after S1 filtration to control the pH of the solution to 7-8; S3: Send the clarified liquid after S2pH adjustment into the flocculation sedimentation tank, add 0.3-3 parts of flocculant, and after flocculation sedimentation, filter; S4: Membrane filtration system treatment: The water filtered by S3 is kept in the submerged membrane filtration system for 30-60 minutes; the submerged membrane filtration system uses a modified submerged ultrafiltration membrane with a curtain structure. S5: The clarified liquid after treatment by the membrane filtration system is sent to the biological contact oxidation tank for further treatment. The clarified liquid is used to recover the KOH solution. The method for preparing the modified submerged ultrafiltration membrane is as follows: H1: Immerse the submerged ultrafiltration membrane in methyl 3-mercaptopropionate at 25°C for 60-100 min, and then initiate the grafting reaction with plasma glow discharge under an argon atmosphere at a flow rate of 20-30 ml / min. The external electrode glow discharge power is 100-200 W, the treatment time is 5-15 min, and the membrane is removed and dried to obtain the mercapto submerged ultrafiltration membrane. H2: By weight, 100-200 parts of the mercapto-immersed ultrafiltration membrane prepared according to the above steps are placed into 1000-1500 parts of DMF, and then 10-16 parts of diallyl bisphenol, 3-6 parts of allyl zinc bromide, 0.03-0.6 parts of (6-mercaptohexyl)ferrocene, and 3-6 parts of triethanolamine are added. The mixture is stirred evenly and soaked at 65-75℃ for 2-4 hours. The ultrafiltration membrane is then removed and dried in an ultra-clean room, and then placed in a constant temperature drying oven for 10-20 hours. The surface grafting reaction is then carried out using plasma glow discharge method, with the same power as before and a processing time of 20-50 seconds, to obtain the modified immersed ultrafiltration membrane. The fluoride-containing wastewater mentioned is wastewater from the preparation of hexafluoropropylene; The precipitant is 10-20% quicklime slurry.

2. The method for treating fluoride-containing wastewater according to claim 1, characterized in that: The defluorinating agent is one or more of magnesium hydroxide, sodium persulfate, sulfuric acid, hydrochloric acid, acrylamide, diethylenetriamine, and ethylenediamine.

3. The method for treating fluoride-containing wastewater according to claim 1, characterized in that: The pH adjuster is a hydrochloric acid solution with a mass concentration of 10-20%.

4. The method for treating fluoride-containing wastewater according to claim 1, characterized in that: The flocculant is one or more of polyaluminum chloride, aluminum hydroxide, aluminum oxide, and aluminum chloride.

5. The method for treating fluoride-containing wastewater according to claim 1, characterized in that: The operating conditions of the biological contact oxidation tank are as follows: the residence time of the biological contact oxidation tank is 6-12 hours and the temperature is 15-35℃.