Treatment method of high-concentration wastewater containing fluorine and phosphorus

Abstract

The invention relates to a treatment method of high-concentration wastewater containing fluorine and phosphorus. The treatment method comprises the following steps: adjusting the pH value of the high-concentration fluorine-containing phosphorus-containing wastewater to 2-6; adding ferric salt into the wastewater with the adjusted pH to precipitate F <-> and PO4 < 3->; the pH value is adjusted to 2-6 again, continuous stirring is conducted, then precipitation products are removed through centrifugal separation, the concentration of the fluorine element in the high-concentration fluorine-containing phosphorus-containing wastewater is 200-20000 mg / L, and the concentration of the phosphorus element in the high-concentration fluorine-containing phosphorus-containing wastewater is 30-20000 mg / L. Compared with the prior art, the treatment method disclosed by the invention is simple in process operation, low in cost and better in defluorination and dephosphorization effects.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a method for treating high-concentration fluorine- and phosphorus-containing wastewater. Background Art

[0002] In recent years, the rapid development of industries such as semiconductors, photovoltaics, and chemicals has generated large quantities of highly concentrated fluorine and phosphorus-containing wastewater. Left untreated, this type of wastewater can adversely impact human health and the ecological environment. For example, excessive absorption of water-soluble fluoride by the human body can cause symptoms such as diarrhea and vomiting, and can even lead to shock and death. Excessive fluoride can also affect the metabolism of plants and animals. Phosphorus, as one of the elements required for the normal functioning of ecosystems, participates in many metabolic reactions and is essential for plant and animal growth, making it indispensable for life. However, excessive phosphorus can lead to the proliferation of algae in water, causing eutrophication, degrading aquatic ecosystems, and compromising the water's self-purification capacity. Therefore, treating highly concentrated fluorine and phosphorus-containing wastewater is of vital importance.

[0003] There are various methods for removing fluoride and phosphorus from water, including chemical precipitation, biological methods, adsorption, membrane separation, and ion exchange. For example, adsorbents such as biochar and metal oxides can be used to remove fluoride and phosphorus, ultrafiltration membranes can be used to intercept phosphates, and ion exchange resins can be used to remove fluoride and phosphorus from water.

[0004] CN 102070267 A discloses a method for treating high-concentration acidic phosphorus- and fluoride-containing wastewater. The method comprises the following steps: first, adding a calcium hydroxide emulsion to the acidic phosphorus- and fluoride-containing wastewater, and controlling the pH of the system to between 12 and 14 to obtain a reaction system containing a precipitate. This step can remove most of the fluorine and phosphorus in the solution. The pH of the wastewater after the first step is adjusted to 9-11 using sulfuric acid, and then to 6-7 using aluminum sulfate to obtain a reaction system containing a precipitate to further remove fluorine from the solution. However, controlling the pH to 12-14 in this application consumes a large amount of calcium salt.

[0005] CN 116854288 A proposes a method for separating and recovering phosphorus and fluorine in phosphorus-fluorine wastewater. The method comprises the following steps: (1) adding calcium salt and seed crystal inducer to the phosphorus-fluorine wastewater after aeration, adjusting the pH to 3-5, promoting the growth of calcium fluoride crystals, recovering most of the fluorine in the solution, and then entering the sedimentation tank; (2) adding a defluoridating agent to the sedimentation tank to further remove fluorine and achieve deep separation of fluorine and phosphorus, and then entering the reaction tank; (3) adding calcium salt to the reaction tank, controlling the pH to 5-9, generating calcium hydrogen phosphate precipitate, and recovering phosphorus in the wastewater. However, this treatment method requires multiple additions of calcium salt and additional seed crystal inducer, making the operation very cumbersome.

[0006] CN 118724209 A discloses a calcium oxide-iron composite agent for treating phosphorus and fluoride wastewater based on synergistic effects, as well as its preparation method and application. The calcium oxide-iron composite agent is prepared by adding calcium oxide and a dispersant to water, mixing, and then adding iron powder. After soaking, the calcium oxide-iron composite agent removes fluoride and phosphorus from the water by forming a precipitate with fluoride ions and phosphates. The iron powder removes phosphates and fluorides from the wastewater by adsorption, precipitation, and coprecipitation. However, this application requires the pre-preparation of the composite agent, and the ultimate removal of fluoride and phosphorus is based on the separate effects of calcium oxide and iron powder.

[0007] Although the above treatment methods have a certain effect on removing fluorine and phosphorus in fluorine-containing and phosphorus-containing wastewater, they often require the addition of more than one treatment precipitant, resulting in a complicated treatment process and high treatment costs.

[0008] Therefore, a new and efficient treatment method for high-concentration fluorine- and phosphorus-containing wastewater still needs to be developed. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for treating high-concentration fluorine- and phosphorus-containing wastewater in order to overcome the defects of the above-mentioned existing treatment methods, such as complex process flow and inability to remove fluorine and phosphorus in one step.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] The present invention provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, the method comprising the following steps:

[0012] S1: Adjust the pH of high-concentration fluorine- and phosphorus-containing wastewater to 2-6;

[0013] S2: Add iron salt to the wastewater with adjusted pH to precipitate F - and PO4 3- ;

[0014] S3: Adjust the pH to 2-6 again with continuous stirring, and then remove the precipitated product by centrifugation;

[0015] The high-concentration fluorine-containing and phosphorus-containing wastewater has a fluorine concentration of 200 to 20,000 mg / L and a phosphorus concentration of 30 to 20,000 mg / L.

[0016] Furthermore, in step S1, the pH is adjusted using alkaline solution or acid solution.

[0017] Furthermore, the alkali solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0018] Furthermore, the acid solution includes any one or more combinations of hydrochloric acid, nitric acid, sulfuric acid or acetic acid.

[0019] Furthermore, in step S2, the iron salt includes any one or more combinations of ferric chloride, ferric sulfate, and ferric nitrate.

[0020] Furthermore, in step S2, the amount of the iron salt added satisfies the following conditions: 3+ The molar amount of F in wastewater - The molar amount and PO4 3- The molar amounts are L, M and N respectively, then L>1 / 3M+N.

[0021] Furthermore, in step S3, the pH is adjusted using an alkaline solution or an acid solution. The secondary pH adjustment can promote the precipitation of fluorine and phosphorus in the wastewater.

[0022] Furthermore, the alkali solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0023] Furthermore, the acid solution includes any one or more combinations of hydrochloric acid, nitric acid, sulfuric acid or acetic acid.

[0024] Furthermore, in step S3, the stirring time is 5 to 30 minutes.

[0025] Furthermore, in step S3, the stirring speed is 50 to 300 rpm.

[0026] Furthermore, in step S3, the Fe dissolved in the stirring process 3+ With F - Combined to form FeF3 precipitate.

[0027] Furthermore, in step S3, the Fe dissolved in the stirring process 3+ With PO4 3- The binding of Fe 3+ The iron hydroxide colloid generated by hydrolysis and PO4 3- Adsorption and coprecipitation occur; Fe 3+ Directly with PO4 3- Reacts to form phosphate precipitate; Fe 3+ With PO4 3- The hydroxyl groups in the wastewater undergo hydrolysis reactions to generate insoluble basic iron phosphate complexes.

[0028] Furthermore, in step S3, the centrifugation time is 5 to 30 minutes.

[0029] Furthermore, in step S3, the centrifugal speed is 1000-8000 rpm.

[0030] Furthermore, the fluorine concentration in the treated wastewater is not higher than 100 mg / L, and the phosphorus concentration is not higher than 1 mg / L.

[0031] The basic principle of the present invention for treating high-concentration fluorine-containing and phosphorus-containing wastewater is as follows: the fluorine in the wastewater is removed by the ferric chloride treatment. 3+ With F - Combined to form FeF3 precipitation. Ferric chloride treatment of phosphorus in wastewater includes the following three methods: Fe 3+ Hydrolysis generates ferric hydroxide colloid which reacts with phosphate ions for adsorption and coprecipitation; Fe 3+ Directly with PO4 3- Reacts to form phosphate precipitate; Fe 3+ It will undergo rapid hydrolysis reaction with phosphate ions and hydroxyl ions to generate insoluble basic iron phosphate complexes, and the surface of the generated complex can further remove phosphorus from wastewater by adsorption.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) In the present invention, the method for treating high-concentration fluorine- and phosphorus-containing wastewater using iron salts first adjusts the initial pH of the wastewater to acidic, then adds ferric chloride once, adjusts the pH to acidic a second time, and then separates the wastewater. Ultimately, the fluorine concentration can be reduced to below 100 mg / L, and the phosphorus concentration can be reduced to below 1 mg / L. This treatment method is simple to operate, low-cost, and has excellent fluorine and phosphorus removal effects.

[0034] (2) The present invention only needs to add iron salt once to achieve the effect of F - and PO4 3- The method is convenient to operate because it does not require the batch and multiple addition of precipitants and additional seed inducers, nor does it require the advance preparation of a composite agent containing multiple compounds. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0036] The present invention provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, the method comprising the following steps:

[0037] S1: Adjust the pH of high-concentration fluorine- and phosphorus-containing wastewater to 2-6;

[0038] S2: Add iron salt to the wastewater with adjusted pH to precipitate F - and PO4 3- ;

[0039] S3: Adjust the pH to 2-6 again with continuous stirring, and then remove the precipitated product by centrifugation;

[0040] The high-concentration fluorine-containing and phosphorus-containing wastewater has a fluorine concentration of 200 to 20,000 mg / L and a phosphorus concentration of 30 to 20,000 mg / L.

[0041] In some specific embodiments, in step S1, the pH is adjusted using alkaline solution or acid solution.

[0042] In some more specific embodiments, the alkali solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0043] In some more specific embodiments, the acid solution includes any one or more combinations of hydrochloric acid, nitric acid, sulfuric acid or acetic acid.

[0044] In some specific embodiments, in step S2, the iron salt includes any one or more combinations of ferric chloride, ferric sulfate, and ferric nitrate.

[0045] In some specific embodiments, in step S2, the amount of the iron salt added satisfies the following conditions: 3+ The molar amount of F in wastewater - The molar amount and PO4 3- The molar amounts are L, M and N respectively, then L>1 / 3M+N.

[0046] In some specific embodiments, in step S3, the pH is adjusted using alkaline solution or acid solution.

[0047] In some more specific embodiments, the alkali solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0048] In some more specific embodiments, the acid solution includes any one or more combinations of hydrochloric acid, nitric acid, sulfuric acid or acetic acid.

[0049] In some specific embodiments, in step S3, the stirring time is 5 to 30 minutes.

[0050] In some specific embodiments, in step S3, the stirring speed is 50-300 rpm.

[0051] In some specific embodiments, in step S3, the Fe dissolved during the stirring process 3+ With F - Combined to form FeF3 precipitate.

[0052] In some specific embodiments, in step S3, the Fe dissolved during the stirring process 3+ With PO4 3- The binding of Fe 3+ The iron hydroxide colloid generated by hydrolysis and PO4 3- Adsorption and coprecipitation occur; Fe 3+ Directly with PO4 3- Reacts to form phosphate precipitate; Fe 3+ With PO4 3- The hydroxyl groups in the wastewater undergo hydrolysis reactions to generate insoluble basic iron phosphate complexes.

[0053] In some specific embodiments, in step S3, the centrifugation time is 5 to 30 minutes.

[0054] In some specific embodiments, in step S3, the centrifugal speed is 1000-8000 rpm.

[0055] In some specific embodiments, the fluorine concentration in the treated wastewater is no higher than 100 mg / L, and the phosphorus concentration is no higher than 1 mg / L.

[0056] The above embodiments can be implemented individually or in any combination of two or more. The above embodiments will be described in more detail below with reference to specific examples.

[0057] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0058] Example 1:

[0059] The high-concentration fluorine- and phosphorus-containing wastewater used in this example was collected from a semiconductor manufacturing company and had been initially filtered. The resulting solution was a colorless, pungent liquid with a fluorine content of 6277 mg / L, a phosphorus content of 9790 mg / L, and an acidity of 1.3 mol / L, indicating high-concentration fluorine- and phosphorus-containing wastewater. See Table 1 for the specific elemental contents.

[0060] Table 1 Contents of elements in high concentration fluorine and phosphorus-containing wastewater

[0061]

[0062] This embodiment provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, which specifically includes the following steps:

[0063] (1) Measure 100 ml of high-concentration fluorine- and phosphorus-containing wastewater into a tetrafluoroethylene beaker and add sodium hydroxide solution to adjust the pH of the wastewater to 4.4.

[0064] (2) In molar ratio [F - ] / [Fe 3+ ]=3 and [Fe 3+ ] / [PO4 3- ]=1 is the minimum, add enough ferric chloride to meet the Fe 3+ F in wastewater - and PO4 3- Complete precipitation.

[0065] (3) Sodium hydroxide solution was added to adjust the wastewater pH to 4.4. After pH adjustment, the wastewater was stirred in a stirrer at 150 rpm for 10 minutes. The wastewater was then centrifuged at 7000 rpm for 10 minutes to obtain the treated wastewater. Testing showed that the fluorine content was reduced to 39.1 mg / L and the phosphorus content was reduced to 0.72 mg / L.

[0066] Example 2:

[0067] The high-concentration fluorine- and phosphorus-containing wastewater used in this example was collected from a semiconductor manufacturing company and had been initially filtered. The resulting solution was a colorless, pungent liquid with a fluorine content of 3625 mg / L, a phosphorus content of 4254 mg / L, and an acidity of 0.7 mol / L, indicating high-concentration fluorine- and phosphorus-containing wastewater. See Table 2 for the specific elemental contents.

[0068] Table 2 Contents of elements in high concentration fluorine and phosphorus-containing wastewater

[0069]

[0070] This embodiment provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, which specifically includes the following steps:

[0071] (1) Measure 100 ml of high-concentration fluorine- and phosphorus-containing wastewater into a tetrafluoroethylene beaker and add sodium hydroxide solution to adjust the pH of the wastewater to 5.2.

[0072] (2) In molar ratio [F - ] / [Fe 3+ ]=3 and [Fe 3+ ] / [PO4 3- ]=1 is the minimum, add enough ferric chloride to meet the Fe 3+ F in wastewater - and PO4 3- Complete precipitation.

[0073] (3) Sodium hydroxide solution was added to adjust the wastewater pH to 5.2. After pH adjustment, the wastewater was stirred in a stirrer at 150 rpm for 10 minutes. The wastewater was then centrifuged in a centrifuge at 7000 rpm for 10 minutes to obtain the treated wastewater. Testing showed that the fluorine content could be reduced to 31.5 mg / L, and the phosphorus content could be reduced to 0.69 mg / L.

[0074] Example 3:

[0075] The high-concentration fluorine- and phosphorus-containing wastewater used in this example was collected from a semiconductor manufacturing company and had been initially filtered. The resulting solution was a colorless, pungent liquid with a fluorine content of 18,720 mg / L, a phosphorus content of 16,637 mg / L, and an acidity of 2.8 mol / L, indicating high-concentration fluorine- and phosphorus-containing wastewater. See Table 3 for the specific elemental contents.

[0076] Table 3 Contents of elements in high concentration fluorine and phosphorus-containing wastewater

[0077]

[0078] This embodiment provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, which specifically includes the following steps:

[0079] (1) Measure 100 ml of high-concentration fluorine- and phosphorus-containing wastewater into a tetrafluoroethylene beaker and add sodium hydroxide solution to adjust the pH of the wastewater to 4.6.

[0080] (2) The molar ratio is [F - ] / [Fe 3+ ]=2.8,[Fe 3+ ] / [PO4 3- ]=1.1Add enough ferric chloride to meet the Fe 3+ F in wastewater - and PO4 3- Complete precipitation.

[0081] (3) Sodium hydroxide solution was added to adjust the wastewater pH to 4.6. After pH adjustment, the wastewater was stirred in a stirrer at 150 rpm for 15 minutes. The wastewater was then centrifuged in a centrifuge at 8000 rpm for 5 minutes to obtain the treated wastewater. Testing showed that the fluorine content was reduced to 89.2 mg / L and the phosphorus content was reduced to 0.91 mg / L.

[0082] Example 4:

[0083] The high-concentration fluorine- and phosphorus-containing wastewater used in this example was collected from a semiconductor manufacturing company and had been initially filtered. The resulting solution was a colorless, pungent liquid with a fluorine content of 211 mg / L, a phosphorus content of 33 mg / L, and an acidity of 0.14 mmol / L, indicating high-concentration fluorine- and phosphorus-containing wastewater. See Table 4 for the specific elemental contents.

[0084] Table 4 Contents of elements in high concentration fluorine and phosphorus-containing wastewater

[0085]

[0086] This embodiment provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, which specifically includes the following steps:

[0087] (1) Measure 100 ml of high-concentration fluorine- and phosphorus-containing wastewater into a tetrafluoroethylene beaker and add sodium hydroxide solution to adjust the pH of the wastewater to 4.2.

[0088] (2) In molar ratio [F - ] / [Fe 3+ ]=3 and [Fe 3+ ] / [PO4 3- ]=1 is the minimum, add enough ferric chloride to meet the Fe 3+ F in wastewater - and PO4 3- Complete precipitation.

[0089] (3) Sodium hydroxide solution was added to adjust the wastewater pH to 4.2. After pH adjustment, the wastewater was stirred in a stirrer at 150 rpm for 15 minutes. The wastewater was then centrifuged in a centrifuge at 8000 rpm for 10 minutes to obtain the treated wastewater. Testing showed that the fluorine content could be reduced to 11.3 mg / L and the phosphorus content could be reduced to 0.11 mg / L.

[0090] Comparative Example 1:

[0091] The high-concentration fluorine- and phosphorus-containing wastewater used in this comparative example was collected from a semiconductor manufacturing company and had been initially filtered. The overall solution was a colorless liquid with a fluorine content of 3928 mg / L, a phosphorus content of 8620 mg / L, and a hydroxide ion concentration of 2.2 mol / L, representing high-concentration fluorine- and phosphorus-containing alkaline wastewater. See Table 5 for the specific elemental contents.

[0092] Table 5 Contents of elements in high concentration fluorine and phosphorus-containing wastewater

[0093]

[0094]

[0095] This comparative example provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, which specifically comprises the following steps:

[0096] (1) Measure 100 ml of high-concentration fluorine- and phosphorus-containing wastewater and place it in a tetrafluoroethylene beaker.

[0097] (2) In molar ratio [F - ] / [Fe 3+ ]=3 and [Fe 3+ ] / [PO4 3- ]=1 is the minimum, add enough ferric chloride to meet the Fe 3+ F in wastewater - and PO4 3- Complete precipitation.

[0098] (3) Hydrochloric acid solution was added to adjust the wastewater pH to 4.6. After pH adjustment, the wastewater was stirred in a stirrer at 150 rpm for 10 minutes. The wastewater was then centrifuged at 7000 rpm for 10 minutes to obtain treated wastewater. Testing revealed that the fluorine content in the wastewater was 3751 mg / L and the phosphorus content was 8237 mg / L.

[0099] In this comparative example, the initial pH of the extremely alkaline wastewater was not adjusted. After ferric chloride was added to the wastewater, ferric hydroxide precipitate was generated and the solution was still alkaline. A secondary adjustment of the pH to 4.6 still could not change the experimental results, and therefore fluorine and phosphorus in the wastewater could not be effectively removed.

[0100] Comparative Example 2:

[0101] The high-concentration fluorine- and phosphorus-containing wastewater used in this comparative example was collected from a semiconductor manufacturing company and had been initially filtered. The resulting solution was a colorless liquid with a pungent smell. It contained 7040 mg / L of fluorine, 8540 mg / L of phosphorus, and an acidity of 1.4 mol / L, representing high-concentration fluorine- and phosphorus-containing wastewater. See Table 6 for the specific elemental contents.

[0102] Table 6 Contents of elements in high concentration fluorine and phosphorus-containing wastewater

[0103]

[0104] This comparative example provides a method for treating high-concentration fluorine- and phosphorus-containing wastewater, which specifically comprises the following steps:

[0105] (1) Measure 100 ml of high-concentration fluorine- and phosphorus-containing wastewater into a tetrafluoroethylene beaker and add sodium hydroxide solution to adjust the pH of the wastewater to 4.4.

[0106] (2) In molar ratio [F - ] / [Fe 3+ ]=3 and [Fe 3+] / [PO4 3- ]=1 is the minimum, add enough ferric chloride to meet the Fe 3+ F in wastewater - and PO4 3- Complete precipitation.

[0107] (3) Stirring in a stirrer at 150 rpm for 10 min. Subsequently, centrifuging in a centrifuge at 7000 rpm for 10 min to obtain treated wastewater. Testing showed that the fluorine content in the wastewater was 6945 mg / L and the phosphorus content was 8390 mg / L. In this comparative example, the pH of the wastewater was not adjusted secondary, and the wastewater was strongly acidic. Under these conditions, iron salts could not effectively remove fluorine and phosphorus from the wastewater.

[0108] In summary, the present invention utilizes ferric chloride to treat high-concentration fluorine- and phosphorus-containing wastewater. The initial pH of the wastewater is first adjusted to acidic, followed by the addition of ferric chloride at a specific molar ratio and further adjustment of the pH. After the reaction, solid-liquid separation is performed to obtain treated wastewater, wherein the fluorine concentration can be reduced to below 100 mg / L, and the phosphorus concentration can be reduced to below 1 mg / L. This treatment method is simple to operate, low-cost, and has excellent fluorine and phosphorus removal effects.

[0109] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for treating high-concentration fluorine- and phosphorus-containing wastewater, characterized in that: The processing method comprises the following steps: S1: Adjust the pH of high-concentration fluorine- and phosphorus-containing wastewater to 2-6; S2: Add iron salt to the wastewater with adjusted pH to precipitate F - and PO4 3- ; S3: Adjust the pH to 2-6 again with continuous stirring, and then remove the precipitated product by centrifugation; The high-concentration fluorine-containing and phosphorus-containing wastewater has a fluorine concentration of 200 to 20,000 mg / L and a phosphorus concentration of 30 to 20,000 mg / L.

2. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S1, the pH is adjusted using alkaline solution or acid solution; The alkali solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide; The acid solution includes any one or more of hydrochloric acid, nitric acid, sulfuric acid or acetic acid.

3. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S2, the iron salt includes any one or more combinations of ferric chloride, ferric sulfate, and ferric nitrate.

4. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S2, the amount of the iron salt added satisfies the following conditions: Definition of Fe in iron salts 3+ The molar amount of F in wastewater - The molar amount and PO4 3- The molar amounts are L, M and N respectively, then L>1 / 3M+N.

5. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S3, the pH is adjusted using alkaline solution or acid solution; The alkali solution includes any one or more combinations of sodium hydroxide, potassium hydroxide, and calcium hydroxide; The acid solution includes any one or more of hydrochloric acid, nitric acid, sulfuric acid or acetic acid.

6. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S3, the stirring time is 5 to 30 minutes, and the stirring speed is 50 to 300 rpm.

7. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S3, the Fe dissolved in the stirring process 3+ With F - Combined to form FeF3 precipitate.

8. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S3, the Fe dissolved in the stirring process 3+ With PO4 3- The combination includes the following three ways: Fe 3+ The iron hydroxide colloid generated by hydrolysis and PO4 3- Adsorption and coprecipitation occur; Fe 3+ Directly with PO4 3- A reaction occurs to form a phosphate precipitate; Fe 3+ With PO4 3- The hydroxyl groups in the wastewater undergo hydrolysis reactions to generate insoluble basic iron phosphate complexes.

9. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: In step S3, the centrifugal speed is 1000-8000 rpm, and the centrifugal time is 5-30 min.

10. The method for treating high-concentration fluorine- and phosphorus-containing wastewater according to claim 1, characterized in that: The fluorine concentration in the treated wastewater is not higher than 100 mg / L, and the phosphorus concentration is not higher than 1 mg / L.

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