A method for treating fluorine-containing ammonia nitrogen wastewater

Abstract

The invention discloses a method for treating fluorine-containing ammonia nitrogen wastewater, which belongs to the technical field of wastewater treatment, and comprises the following steps: the first step, the fluorine-containing ammonia nitrogen wastewater enters the first reaction tank, adjusts the pH, mixes with modified hydroxyapatite, flows into the filter tank after sufficient stirring, the filtered wastewater enters the second reaction tank, adjusts the pH, mixes with a coagulant, enters the sedimentation tank for static sedimentation, and collects the supernatant; the second step, the supernatant in the first step enters the ultrasonic treatment tank, adjusts the pH, enters the stripping tower, the ammonia gas stripped enters the absorption tower, the wastewater treated by the stripping tower enters the pH adjustment tank, adjusts the pH of the wastewater, and obtains pre-treated wastewater; the third step, the pre-treated wastewater enters the SBR tank, and undergoes water inlet stirring, aeration, aeration stop stirring, sedimentation and sludge discharge to obtain treated wastewater. The method for treating fluorine-containing ammonia nitrogen wastewater provided by the invention can efficiently and stably remove fluorine and ammonia nitrogen in wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and specifically relates to a method for treating fluorine-containing ammonia nitrogen wastewater. Background Art

[0002] With the development of electronic industry technology, especially integrated circuit chip industry technology, the treatment of electronic industry wastewater, especially fluorine-containing ammonia nitrogen wastewater in the electronic industry has become a prominent problem in the water treatment industry. The electronic industry usually uses a large number of chemical agents such as hydrofluoric acid, sulfuric acid, phosphoric acid, ammonia water, hydrochloric acid and organic solvents in the production process, so that the discharged wastewater contains a large number of components that pollute the surrounding environment. At present, there are many treatment processes for fluorine-containing ammonia nitrogen wastewater. For fluorine-containing wastewater, quicklime is mainly used to flocculate and precipitate sulfate and fluoride ions in the wastewater. For ammonia nitrogen wastewater, air stripping, steam stripping and membrane separation are mainly used to remove ammonia nitrogen. However, these processes have the disadvantages of high energy consumption, large amount of hazardous waste residue, easy to generate secondary pollution, low treatment efficiency and high treatment cost, which limit the application of these methods in production enterprises.

[0003] At present, the common methods for treating fluoride-containing wastewater are chemical precipitation and flocculation precipitation. Among them, the chemical precipitation method is mainly used for the treatment of high-concentration fluoride-containing wastewater. The calcium salt precipitation method is more commonly used. By adding calcium salts and other chemicals to the wastewater, calcium ions react with fluoride ions to form CaF2 precipitates to achieve the purpose of removing fluoride from the wastewater. This process is simple and convenient with low cost, but the precipitate generated in the calcium salt precipitation method will be wrapped on the surface of the Ca(OH)2 particles, making it unable to be fully utilized. Therefore, it is necessary to add excess Ca 2+ However, a large amount of calcium salt mixed into the sludge not only increases the sludge production, but also the fluoride content in the treated wastewater reaches more than 20 mg / L, which is difficult to meet the national emission standards. The flocculation sedimentation method is prone to generate very fine particles in the process of treating wastewater. They have a small specific gravity and high viscosity. They are colloidal during the sedimentation process, making them difficult to separate. Not only does it make it difficult for the wastewater to meet the standards, but the generated sludge has a high water content and is difficult to recycle.

[0004] Therefore, it is of great significance to develop a method for treating fluorine-containing ammonia nitrogen wastewater with simple treatment process, economical cost and high efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a method for treating fluorine-containing ammonia nitrogen wastewater to solve the problem that the fluorine removal effect in the prior art treatment method for fluorine-containing ammonia nitrogen is poor, the fluorine content in the treated wastewater reaches more than 20 mg / L, and it is difficult to meet the national emission standards.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for treating fluorine-containing ammonia nitrogen wastewater comprises the following steps:

[0008] In the first step, the fluorine-containing ammonia nitrogen wastewater enters the first reaction tank, adjusts the pH to 8-10, mixes with modified hydroxyapatite, and flows into the filtration tank after sufficient stirring. The filtered wastewater enters the second reaction tank, adjusts the pH to 6-8, mixes with a coagulant, enters the sedimentation tank for static sedimentation, and collects the supernatant;

[0009] In the second step, the supernatant in the first step enters an ultrasonic treatment tank, adjusts the pH to 10.5-11.5, enters a stripping tower, and the ammonia gas stripped enters an absorption tower. The wastewater treated by the stripping tower enters a pH adjustment tank, and the pH of the wastewater is adjusted to 11.3-11.5 to obtain pretreated wastewater;

[0010] In the third step, the pretreated wastewater enters the SBR tank and undergoes water inlet stirring, aeration, aeration stop stirring, sedimentation and sludge discharge to obtain treated wastewater.

[0011] As a further embodiment of the present invention, the modified hydroxyapatite is prepared by the following steps:

[0012] Add meso-tetra(4-carboxyphenyl)porphine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to dimethyl sulfoxide for ultrasonic mixing, heat to 33-35°C, stir to react, add amination hydroxyapatite, continue to stir to react, filter and wash, collect precipitate, dry, grind to obtain modified hydroxyapatite. By using the carboxyl group on meso-tetra(4-carboxyphenyl)porphine to react chemically with the amino group on the surface of amination hydroxyapatite, porphyrin macromolecules are formed on its surface and coated on the surface of hydroxyapatite, thereby improving the dispersibility and compatibility of hydroxyapatite in water, and overcoming the disadvantages of small hydroxyapatite particles, easy loss and difficult recovery.

[0013] As a further embodiment of the present invention, the usage ratio of meso-tetrakis(4-carboxyphenyl)porphine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide, dimethyl sulfoxide and amino hydroxyapatite is 3.0-3.2 mg: 5.9-6.0 mg: 2.1-2.2 mg: 10 mL: 2-3 mg.

[0014] As a further solution of the present invention, the powder is ground to a particle size of 180-220 μm.

[0015] As a further embodiment of the present invention, the aminated hydroxyapatite is prepared by the following steps:

[0016] Add silane coupling agent KH-550 to ethanol aqueous solution, adjust pH, hydrolyze at room temperature, add hydroxyapatite, disperse by ultrasonic, heat to 60-65°C, stir for reaction, evaporate and wash, dry to obtain amino hydroxyapatite. Graft silane coupling agent KH-550 on the surface of hydroxyapatite to obtain amino hydroxyapatite, which improves the mechanical stability of hydroxyapatite on the one hand, improves the dispersibility and dispersion stability of hydroxyapatite on the other hand, reduces the agglomeration phenomenon in water, further improves the adsorption capacity of fluoride ions, and improves the defluorination efficiency.

[0017] As a further embodiment of the present invention, the usage ratio of silane coupling agent KH-550, ethanol aqueous solution and hydroxyapatite is 0.5-1.5 mL: 50 mL: 3-5 g.

[0018] As a further embodiment of the present invention, the pH is adjusted to 4-4.5.

[0019] As a further solution of the present invention, the modified hydroxyapatite is 3 to 5 times the fluorine content in the wastewater.

[0020] As a further solution of the present invention, the coagulant is at least one of polyacrylamide and polyaluminium chloride.

[0021] As a further solution of the present invention, the gas-liquid ratio in the stripping tower is 5000:1.

[0022] As a further solution of the present invention, heating is performed in the stripping tower at a heating temperature of 40-50°C.

[0023] As a further solution of the present invention, the carbon source in the SBR pool includes one of domestic sewage and pig manure.

[0024] Beneficial effects of the present invention:

[0025] 1. A method for treating fluorine-containing ammonia nitrogen wastewater provided by the present invention, firstly, the wastewater is passed through a first reaction tank, and mixed with modified hydroxyapatite under a wide pH condition to adsorb fluorine ions. The modified hydroxyapatite has an excellent adsorption effect on fluorine ions, which greatly reduces the fluorine ion content in the wastewater. After filtration, the wastewater enters a second reaction tank to react with a coagulant again, and the wastewater is further defluorinated, so that the total fluorine content in the wastewater can be reduced to below 10 mg / L. The wastewater after defluorination is treated with a combined process of ultrasonic stripping and SBR method to remove ammonia nitrogen. Ultrasonic waves are used to induce cavitation in water to generate cavitation bubbles, so that the volatilization and mass transfer effect of NH3 in water are greatly accelerated, and NH3 in the wastewater is more easily transferred from the liquid phase to the gas phase, which strengthens the stripping effect of NH3. The stripping tail gas can also realize the recovery of ammonia, reducing secondary pollution. The fluorine content and ammonia nitrogen content of the wastewater discharged by the treatment method of the present invention can reach the national first-level emission standard.

[0026] 2. In the present invention, the modified hydroxyapatite is first grafted on the surface of hydroxyapatite by silane coupling agent KH-550 to obtain amino hydroxyapatite, and then the amino groups on the surface of the amino hydroxyapatite react chemically with the carboxyl groups on the medium-tetra(4-carboxyphenyl)porphine to form porphyrin macromolecules on its surface, which are coated on the surface of hydroxyapatite, thereby improving the dispersibility and compatibility of hydroxyapatite in water, thereby increasing the adsorption amount of fluoride ions by hydroxyapatite and improving the fluoride removal efficiency. In addition, the disadvantages of small hydroxyapatite particles, which make it difficult to recover and easy to lose, are overcome, and the action time of hydroxyapatite is extended. Compared with the commonly used powdered hydroxyapatite, the modified hydroxyapatite has the advantages of large adsorption capacity, fast adsorption and desorption rates, and easy recovery. In addition, the generated porphyrin can generate active oxygen that causes oxidative damage to biological species under the condition of light, thereby achieving effective sterilization of water bodies and further purifying water bodies.

[0027] 3. The method for treating fluorine-containing ammonia nitrogen wastewater provided by the present invention can efficiently and stably remove fluorine and ammonia nitrogen from wastewater. The treated wastewater can meet the national first-level emission standards, and the wastewater treatment operation cost is low, the operation is simple, easy to manage, and there is no secondary pollution, which has good promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 The present invention is a flow chart of a method for treating fluorine-containing ammonia nitrogen wastewater. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The aminated hydroxyapatite used in the examples and comparative examples of the present invention is prepared by the following steps:

[0032] 1 mL of silane coupling agent KH-550 was added to 50 mL of ethanol aqueous solution (volume ratio of ethanol to water was 9:1), the pH was adjusted to 4 with acetic acid solution, hydrolyzed at room temperature for 0.5 h, 3.5 g of hydroxyapatite was added, ultrasonic dispersion was performed, the temperature was raised to 60 ° C, the reaction was stirred for 2 h, and the temperature was continued to be raised to 80 ° C to evaporate the solvent, and the solution was washed with anhydrous ethanol and deionized water for 3 times respectively, and dried in an oven at 80 ° C to obtain amino hydroxyapatite.

[0033] Example 1

[0034] This embodiment provides a modified hydroxyapatite, and the preparation steps are as follows:

[0035] 3.0 mg of meso-tetrakis(4-carboxyphenyl)porphine, 5.9 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 2.1 mg of N-hydroxysuccinimide were added to 10 mL of dimethyl sulfoxide, and ultrasonically mixed. The mixture was heated to 35°C and stirred for 12 h. 2 mg of amino-hydroxyapatite was added and the reaction was continued with stirring for 24 h. The mixture was filtered and washed, the precipitate was collected, dried, and ground to a particle size of 200 μm to obtain modified hydroxyapatite.

[0036] Example 2

[0037] This embodiment provides a modified hydroxyapatite, and the preparation steps are as follows:

[0038] 3.1 mg of meso-tetrakis(4-carboxyphenyl)porphine, 5.9 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 2.1 mg of N-hydroxysuccinimide were added to 10 mL of dimethyl sulfoxide, and ultrasonically mixed. The mixture was heated to 35°C and stirred for 12 h. 2.5 mg of amino-hydroxyapatite was added and the reaction was continued with stirring for 24 h. The mixture was filtered and washed, the precipitate was collected, dried, and ground to a particle size of 200 μm to obtain modified hydroxyapatite.

[0039] Example 3

[0040] This embodiment provides a modified hydroxyapatite, and the preparation steps are as follows:

[0041] 3.2 mg of meso-tetrakis(4-carboxyphenyl)porphine, 6.0 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 2.2 mg of N-hydroxysuccinimide were added to 10 mL of dimethyl sulfoxide, mixed by ultrasonication, heated to 35°C, stirred and reacted for 12 h, 3 mg of amino hydroxyapatite was added, and the stirring reaction was continued for 24 h. The precipitate was collected by filtration and washed, dried, and ground to a particle size of 200 μm to obtain modified hydroxyapatite.

[0042] Comparative Example 1

[0043] The aminated hydroxyapatite is ground to a particle size of 200 μm to obtain modified hydroxyapatite.

[0044] Comparative Example 2

[0045] Hydroxyapatite (purchased from Wuhan Kemik Biopharmaceutical Technology Co., Ltd.) was ground to a particle size of 200 μm to obtain modified hydroxyapatite.

[0046] Example 4

[0047] The wastewater used in this embodiment is production wastewater from a chemical enterprise in Hunan, in which the fluorine content is 5.5 g / L, the ammonia nitrogen content is 2.5 g / L, and the amount of wastewater used is 1 ton.

[0048] A method for treating fluorine-containing ammonia nitrogen wastewater comprises the following steps:

[0049] In the first step, 1 ton of fluorine-containing ammonia nitrogen wastewater enters the first reaction tank, adjusts the pH to 8.5, mixes with 16.5 kg of modified hydroxyapatite in Example 1, and flows into the filtration tank after sufficient stirring. The filtered wastewater enters the second reaction tank, adjusts the pH to 7, mixes with polyacrylamide (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.), enters the sedimentation tank for static precipitation, and collects the supernatant;

[0050] In the second step, the supernatant in the first step enters the ultrasonic treatment tank (where the pneumatic ultrasonic generator is 300 mm long, the inner diameter of the tube is 20 mm, the air outlet slit width is 1 mm, the slit length is 20 mm, and the vibrating plate length is 150 mm; the air compressor is a JB-2 air compressor, and the air pressure is 0.4-0.6 mPa.), the pH is adjusted to 11, and enters the stripping tower. The gas-liquid ratio in the stripping tower is 5000:1, and the temperature is 45°C. The ammonia gas stripped out enters the absorption tower, and the wastewater treated by the stripping tower enters the pH adjustment tank, and the pH of the wastewater is adjusted to 11.5 to obtain pretreated wastewater;

[0051] In the third step, the pre-treated wastewater enters the SBR pool, in which the carbon source is domestic sewage. After water inlet stirring, aeration, aeration and stirring, sedimentation and sludge discharge, treated wastewater is obtained.

[0052] Example 5

[0053] The only difference from Example 4 is that:

[0054] In the first step, 16.5 kg of the modified hydroxyapatite in Example 1 was replaced with 22 kg of the modified hydroxyapatite in Example 1. The remaining steps were the same as those in Example 4.

[0055] Example 6

[0056] The only difference from Example 4 is that:

[0057] In the first step, 16.5 kg of the modified hydroxyapatite in Example 1 was replaced with 27.5 kg of the modified hydroxyapatite in Example 1. The remaining steps were the same as those in Example 4.

[0058] Example 7

[0059] The only difference from Example 4 is that:

[0060] In the first step, 16.5 kg of the modified hydroxyapatite in Example 1 was replaced with 27.5 kg of the modified hydroxyapatite in Example 3. The remaining steps were the same as those in Example 4.

[0061] Example 8

[0062] The only difference from Example 4 is that:

[0063] The polyacrylamide in the first step was replaced by polyaluminium chloride (purchased from Shanghai Haohong Biopharmaceutical Technology Co., Ltd.). The remaining steps were the same as those in Example 4.

[0064] Example 9

[0065] The only difference from Example 4 is that:

[0066] In the first step, 1 ton of fluorine-containing ammonia nitrogen wastewater enters the first reaction tank, adjusts the pH to 10, mixes with 16.5 kg of modified hydroxyapatite in Example 2, and flows into the filtration tank after sufficient stirring. The filtered wastewater enters the second reaction tank, adjusts the pH to 7, mixes with polyacrylamide, enters the sedimentation tank for static precipitation, and collects the supernatant; the remaining steps are the same as Example 4.

[0067] Example 10

[0068] The only difference from Example 4 is that:

[0069] In the first step, 1 ton of fluorine-containing ammonia nitrogen wastewater enters the first reaction tank, adjusts the pH to 9, mixes with 16.5 kg of modified hydroxyapatite in Example 3, and flows into the filtration tank after sufficient stirring. The filtered wastewater enters the second reaction tank, adjusts the pH to 8, mixes with polyaluminum chloride, enters the sedimentation tank for static precipitation, and collects the supernatant; the remaining steps are the same as Example 4.

[0070] Embodiment 11

[0071] The only difference from Example 4 is that:

[0072] In the second step, the supernatant in the first step enters the ultrasonic treatment tank, adjusts the pH to 11.4, and enters the stripping tower. The gas-liquid ratio in the stripping tower is 5000:1, the temperature is 50°C, and the ammonia gas stripped enters the absorption tower. The wastewater treated by the stripping tower enters the pH adjustment tank, adjusts the pH of the wastewater to 11.5, and obtains pretreated wastewater. The remaining steps are the same as Example 4.

[0073] Comparative Example 3

[0074] Compared with Example 4, the modified hydroxyapatite in Example 1 was replaced by the modified hydroxyapatite in Comparative Example 1, and the amount used remained unchanged. The remaining steps were the same as in Example 4.

[0075] Comparative Example 4

[0076] Compared with Example 4, the modified hydroxyapatite in Example 1 was replaced by the modified hydroxyapatite in Comparative Example 1, and the amount used remained unchanged. The remaining steps were the same as in Example 4.

[0077] Comparative Example 5

[0078] Compared with Example 4, 16.5 kg of the modified hydroxyapatite in Example 1 was replaced with 13.75 kg of the modified hydroxyapatite in Example 1. The remaining steps were the same as those in Example 4.

[0079] Comparative Example 6

[0080] Compared with Example 4, 16.5 kg of the modified hydroxyapatite in Example 1 was replaced with 30.25 kg of the modified hydroxyapatite in Example 1. The remaining steps were the same as those in Example 4.

[0081] Comparative Example 7

[0082] Compared with Example 4, the pH value was adjusted to 6.5 in the first step. The remaining steps were the same as those in Example 4.

[0083] Comparative Example 8

[0084] Compared with Example 4, the pH value was adjusted to 11.5 in the first step. The remaining steps were the same as those in Example 4.

[0085] The fluorine content and ammonia nitrogen content of the final effluent in Examples 4-11 and Comparative Examples 3-8 were tested, and the test results are shown in Table 1:

[0086]

[0087] It can be seen from Table 1 that, compared with Comparative Examples 3-8, the fluorine content and ammonia nitrogen content of the wastewater in Examples 4-11 all reach the national first-level emission standard. It can be seen that the method for treating fluorine-containing ammonia nitrogen wastewater provided by the present invention can efficiently and stably remove fluorine and ammonia nitrogen from the wastewater, and the treated wastewater can meet the national first-level emission standard, and the wastewater treatment operation is simple, there is no secondary pollution, and it has good application and promotion value.

[0088] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating fluorine-containing ammonia nitrogen wastewater, characterized in that: The following steps are involved: In the first step, the fluorine-containing ammonia nitrogen wastewater enters the first reaction tank, adjusts the pH to 8-10, mixes with modified hydroxyapatite, and flows into the filtration tank after sufficient stirring. The filtered wastewater enters the second reaction tank, adjusts the pH to 6-8, mixes with a coagulant, enters the sedimentation tank for static sedimentation, and collects the supernatant; In the second step, the supernatant in the first step enters the ultrasonic treatment tank, adjusts the pH to 10.5-11.5, enters the stripping tower, and the ammonia gas stripped enters the absorption tower. The wastewater treated by the stripping tower enters the pH adjustment tank, and the pH of the wastewater is adjusted to 11.3-11.5 to obtain pretreated wastewater; Step 3: The pre-treated wastewater enters the SBR tank, and after water inlet stirring, aeration, aeration stop stirring, sedimentation and sludge discharge, the treated wastewater is obtained; Wherein, the modified hydroxyapatite in the first step is prepared by the following steps: Add meso-tetrakis(4-carboxyphenyl)porphine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to dimethyl sulfoxide, mix them by ultrasonication, raise the temperature to 33-35°C, stir to react, add aminated hydroxyapatite, continue to stir to react, filter and wash, collect the precipitate, dry and grind to obtain modified hydroxyapatite; Wherein, the aminated hydroxyapatite is prepared by the following steps: The silane coupling agent KH-550 is added to the ethanol aqueous solution, the pH is adjusted, hydrolyzed at room temperature, hydroxyapatite is added, ultrasonic dispersion is performed, the temperature is raised to 60-65° C., the reaction is stirred, the solution is evaporated and washed, and dried to obtain the amino hydroxyapatite.

2. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: The usage ratio of meso-tetrakis(4-carboxyphenyl)porphine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, N-hydroxysuccinimide, dimethyl sulfoxide and amino hydroxyapatite is 3.0-3.2 mg: 5.9-6.0 mg: 2.1-2.2 mg: 10 mL: 2-3 mg.

3. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: Grind to a particle size of 180-220 μm.

4. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: The dosage ratio of silane coupling agent KH-550, ethanol aqueous solution and hydroxyapatite is 0.5-1.5 mL: 50 mL: 3-5 g.

5. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: Adjust pH to 4-4.

5.

6. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: The modified hydroxyapatite has a fluorine content of 3 to 5 times that of the wastewater.

7. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: The coagulant is at least one of polyacrylamide and polyaluminium chloride.

8. The method for treating fluorine-containing ammonia nitrogen wastewater according to claim 1, characterized in that: The gas-liquid ratio in the stripping tower is 5000:1; The stripping tower is heated at a temperature of 40-50°C; The carbon source in the SBR pool includes one of domestic sewage and pig manure liquid.

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