Fluorine-removing agent for fluorine-containing wastewater treatment and preparation method thereof

Abstract

The application discloses a defluorination agent for fluorine-containing wastewater treatment and a preparation method thereof. The defluorination agent is prepared from chitosan as a biomolecular skeleton and magnesium salt, titanium salt, zirconium salt, aluminum salt, iron salt, rare earth material and organic material as blending raw materials. The mass ratio of the magnesium salt, the titanium salt, the zirconium salt, the aluminum salt, the iron salt, the rare earth material, the organic material and the chitosan is 1-30:1-30:2-20:2-10:2-10:20-50:2-10:1-10. The defluorination agent is prepared from the magnesium salt, the titanium salt, the zirconium salt and the organic material in addition to the existing composite defluorination agent, and has the characteristics of good stability, wide application range and large-scale application.

Description

Technical Field

[0001] This invention relates to the field of water treatment reagents technology, and in particular to a defluoridating agent for treating fluoride-containing wastewater and its preparation method. Background Technology

[0002] The fluoride industry, including fluoride ore mining, aluminum electrolysis, photovoltaics, electroplating, semiconductors, glass, and fertilizer production, generates large amounts of fluoride-containing waste, including wastewater containing fluoride ions. This allows fluoride to enter the environment, and improper management can easily lead to fluoride pollution. Long-term excessive fluoride intake can easily cause chronic fluorosis, severely damaging bones, teeth, and other hard tissues. In severe cases, it can lead to skeletal fluorosis and dental fluorosis, and even increase the risk of cancer. Studies have also confirmed that excessive fluoride intake can affect children's IQ. Therefore, the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB18918-2002) stipulates an upper limit of fluoride discharge of 1.5 mg / L, clearly defining the fluoride content in fluoride-containing wastewater and effluent.

[0003] Domestically and internationally, the main technologies for treating fluoride in wastewater include precipitation (chemical precipitation, coagulation precipitation), adsorption, electrocoagulation, electrodialysis, reverse osmosis, and ion exchange. When treating fluoride-containing wastewater, defluorinating agents are typically used. These agents react chemically with fluoride ions in the water, removing fluoride through adsorption, complexation, and flocculation to form precipitates. The preparation and production of defluorinating agents are common practices. However, existing methods for preparing defluorinating agents for fluoride-containing wastewater treatment often result in single-type purifying agents with poor defluorination effects. These agents also have poor performance and require large quantities, increasing the cost of treating fluoride-containing wastewater and leading to low economic efficiency.

[0004] CN114988547A discloses a composite defluoridator, prepared from components in the following mass ratio: chitosan serves as the biomolecular framework, with an aluminum-iron-rare earth metal blend loaded on the framework, forming a chelate with multiple active sites; wherein the mass ratio of aluminum salt: iron salt: rare earth material: chitosan: acetic acid is 5-10:5-10:15-20:5-10:3-5. This defluoridator, using chitosan as the framework, effectively improves the mechanical strength of chitosan under acidic conditions by fully chelating it with metal ion co-precipitates in acetic acid. Simultaneously, it effectively avoids secondary pollution caused by metal ion back-dissolution. Furthermore, the co-precipitates formed by multiple metal ions not only increase the applicable pH range of the defluoridator but also significantly enhance its adsorption and removal performance for fluoride ions and the settling speed of sludge flocs. The preparation method involves a reverse co-precipitation process to obtain co-precipitates of various metal ions. These co-precipitates have uniform particle size and exhibit no agglomeration or clumping, resulting in uniform dispersion of the metal active sites on chitosan and improving the adsorption performance of the defluorinating agent. Using this defluorinating agent for defluorination demonstrates high efficiency, with a fluoride ion removal rate exceeding 95%.- The concentration was reduced to below 1.0 mg / L. However, the defluorinating agent prepared by this method exhibited severe liquid-solid stratification after prolonged storage. Defluorination tests conducted at intervals showed a significantly lower defluorination rate compared to when the product was first prepared, indicating poor stability. Furthermore, this defluorinating agent is suitable for treating low-concentration industrial wastewater with small flow rates, high influent requirements, and low discharge requirements, limiting its applicability. Additionally, while defluorinating wastewater, the product increases the original turbidity of the wastewater solution. Although the fluoride content can be reduced to below 1 mg / L after treatment, the COD of the wastewater increases instead of decreasing. Moreover, the pH of the wastewater changes significantly after treatment with this defluorinating agent, requiring subsequent alkali adjustment and modifications to the existing water treatment process, making it unsuitable for large-scale application. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a defluorinating agent for the treatment of fluoride-containing wastewater, which solves the technical problems of poor stability, narrow range of action, and unfavorable large-scale application of existing defluorinating agents.

[0006] Furthermore, a method for preparing the defluorinating agent is provided.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A defluoridating agent for treating fluoride-containing wastewater is prepared using chitosan as the biomolecular framework and magnesium salts, titanium salts, zirconium salts, aluminum salts, iron salts, rare earth materials, and organic materials as blending raw materials.

[0009] The mass ratio of magnesium salt: titanium salt: zirconium salt: aluminum salt: iron salt: rare earth material: organic material: chitosan is 1~30: 1~30: 2~20: 2~10: 2~10: 20~50: 2~10: 1~10.

[0010] Furthermore, the mass ratio of magnesium salt: titanium salt: zirconium salt: aluminum salt: iron salt: rare earth material: organic material: chitosan is 3~6: 3~6: 3~6: 5~10: 5~10: 20~30: 2~5: 3~5.

[0011] Further, the magnesium salt includes at least one of magnesium chloride, magnesium sulfate, magnesium citrate, and magnesium acetate; the titanium salt includes at least one of titanium dioxide, titanium tetrachloride, titanium sulfate, and titanium oxysulfate; the zirconium salt includes at least one of zirconium dioxide, zirconium chloride, zirconium silicate, and zirconium sulfate; the aluminum salt includes at least one of aluminum chloride, aluminum sulfate, alum, aluminum oxide, aluminum hydroxide, calcium aluminate, sodium aluminate, and polyaluminum chloride; the iron salt includes at least one of ferric sulfate, ferric chloride, aluminum ferric chloride, ferric oxide, iron tetroxide, ferric hydroxide, and polyaluminum ferric sulfate; the rare earth material is any one of lanthanum nitrate, lanthanum chloride, lanthanum oxide, lanthanum hydroxide, cerium nitrate, cerium chloride, cerium oxide, or cerium hydroxide; the organic material is any one of oxalic acid, tartaric acid, citric acid, naphthalenedicarboxylic acid, 1,4-butanedicarboxylic acid, 1,4-butenedicarboxylic acid, acetylenic acid, phthalic acid, 1,2-phthalic acid, 1,3-phthalic acid, acetylenic acid, acetic acid, ethyl acetate, or chloroacetic acid.

[0012] This invention also provides a method for preparing a defluorinating agent for treating fluoride-containing wastewater, comprising the following steps:

[0013] (1) Add magnesium salt, titanium salt, zirconium salt, aluminum salt, iron salt, rare earth material, and organic material to water according to the mass ratio described in claim 1 or 2, and stir evenly at room temperature to obtain a mixed solution.

[0014] (2) The mixed solution is slowly added dropwise to the sodium hydroxide solution, and the reaction produces metal ion coprecipitates;

[0015] (3) Add the mixture obtained in step (2) to the chitosan solution, dissolve it completely and stir it evenly so that the inorganic metal ions are fully chelated with the chitosan to obtain a mixture.

[0016] (4) Dry the mixture, remove it and cool it to room temperature, then crush and grind it to obtain a powdered defluorinating agent.

[0017] Furthermore, the stirring in step (1) is carried out for 3 to 10 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention, based on existing composite defluorinating agents, adds magnesium salts, titanium salts, zirconium salts, and organic materials to prepare a novel defluorinating agent. Through the compatibility and synergistic effect of the components, it solves the technical problems of poor stability, narrow range of action, and unfavorable large-scale application of existing defluorinating agents. Extensive stability testing has proven that this defluorinating agent has excellent stability, maintaining a removal rate of 95% or higher even with increasing time intervals, while the pH value of the treated wastewater does not change significantly. Therefore, the amount of acid and alkali used to neutralize the wastewater is reduced, which can also lower engineering application costs and make it suitable for large-scale application.

[0020] This defluorinating agent, by adding various inorganic metal ions, possesses a high zero potential point and a wider suitable pH range, maintaining a high defluorination rate within the range of 3–11. Adding magnesium salts makes the internal structure of the defluorinating agent more compact, significantly increasing the specific surface area and the number and stability of active sites that bind to fluoride ions, thereby improving the adsorption efficiency of fluoride ions. Adding titanium salts increases the specific surface area of ​​the material through loading, increasing the number of adsorption active sites; furthermore, loading titanium salts increases the defluorination efficiency and correspondingly widens the pH range for application. Because titanium ions have a strong binding force with fluoride ions, adding titanium ions can enhance the adsorption capacity for fluoride. Adding zirconium salts can remove fluoride ions from wastewater through ion exchange. After adding zirconium salts, Zr-F bonds are formed in the solution. Due to the formation of this chemical bond, the removal of fluoride ions involves not only ion exchange but also a complexation reaction. The reaction energy of the complexation reaction is greater than that of ion exchange, and the complexation reaction enhances the selective adsorption of fluoride ions by this defluorinating agent. Simultaneously, zirconium salts can react with fluoride ions to form a precipitate, and this precipitate is more stable than that of other anions when binding with fluoride ions. The defluorinating agent with added zirconium salts has a significantly enhanced ability to resist interference from coexisting anions. Adding organic materials allows various metals to more tightly combine with chitosan, significantly enhancing the stability of the product and greatly improving the defluorination efficiency. The addition of organic materials promotes the dissolution of fine inorganic metal ions and binds non-dissolved metal solids together into larger complexes, further leading to polymerization reactions. The addition of organic materials also performs doping modification, improving the defluorination capacity of the defluorinating agent. This ensures that the liquid defluorinating agent remains stable, free of free inorganic metal ions, and has high purity with low impurity content, which is beneficial for subsequent drying and calcination to obtain a solid sample, facilitating storage and use. Therefore, the defluoridator prepared by this invention is more environmentally friendly, will not affect water bodies, and will not increase pollutants such as COD, N, and P in the water; it is also more efficient at removing fluoride, targeting high fluoride ion emission standards (F... - For industries and regions with fluoride concentrations <1 mg / L, only a single reaction and precipitation are required. The reagent is more stable, grafted with various metal ions and organic functional groups, resulting in more stable effluent and a higher removal rate. Furthermore, within a pH range of 3–11, fluoride ions will not dissolve due to pH fluctuations. Wastewater treated with the defluorinating agent can have reduced salinity and conductivity, making it suitable for industrial wastewater from coal chemical, photovoltaic, conductive, electronics, and glass industries, with a wide range of applications.

[0021] 2. The defluoridating agent of this invention has a wide range of applications. It can remove fluoride from fluoride-containing wastewater with a fluoride ion concentration of 10-30 mg / L, and the defluoridation efficiency is high. For fluoride-containing wastewater with an initial fluoride ion concentration of 30 mg / L, the fluoride ion removal rate is as high as 99% or more.

[0022] 3. The method for preparing a defluorinating agent for fluoride-containing wastewater treatment according to the present invention involves drying the mixed liquid, calcining to remove water molecules, and pulverizing to refine the mixed metal salt particles, thereby miniaturizing the particle size and obtaining raw materials with small particle sizes. This avoids the problems of agglomeration and clustering of magnesium salts, titanium salts, zirconium salts, aluminum salts, iron salts, and rare earth materials (lanthanum, cerium) during the mixing process, improves the subsequent dissolution quality, ensures uniform mixing of all components in the defluorinating agent, increases the specific surface area of ​​the defluorinating agent, and enhances its defluorination performance. Furthermore, chitosan has a double helix three-dimensional structure, is widely available, inexpensive, and readily available. It has a large specific surface area and contains a large number of functional groups, making it biodegradable. This results in a defluorinating agent with good defluorination performance and excellent purification effect.

[0023] It has wide applicability and is an environmentally friendly material. Detailed Implementation

[0024] The specific embodiments of the present invention will be described in further detail below with reference to specific examples.

[0025] The numerical ranges in this invention should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended, meaning that they include but are not limited to.

[0027] Unless otherwise specified, the experimental methods used in this invention are all conventional methods.

[0028] Unless otherwise specified, all materials and reagents used in this invention can be purchased or synthesized by known methods.

[0029] In the quantitative experiments of this invention, each experiment was repeated three times, and the average value of the results was taken.

[0030] Example 1

[0031] This embodiment provides a defluoridating agent for treating fluoride-containing wastewater, which is prepared using chitosan as the biomolecular framework and magnesium chloride, titanium dioxide, zirconium chloride, aluminum chloride, polyferric sulfate, lanthanum nitrate, and phthalic acid as blended raw materials;

[0032] The mass ratio of magnesium chloride: titanium dioxide: zirconium chloride: aluminum chloride: polyferric sulfate: lanthanum nitrate: phthalic acid: chitosan is 3:3:3:5:5:20:10:5. The degree of deacetylation of chitosan is 95%.

[0033] The above-mentioned defluorinating agent is prepared by the following method, specifically including the following steps:

[0034] (1) Mix 3 parts magnesium chloride, 3 parts titanium dioxide, 3 parts zirconium chloride, 5 parts aluminum chloride, 5 parts polyferric sulfate, 20 parts lanthanum nitrate and 1 part phthalic acid and add them to deionized water. Stir thoroughly at 25°C for 4 hours to obtain mixed solution A.

[0035] (2) Slowly add mixed solution A dropwise into a 10% NaOH solution; the reaction produces a metal coprecipitate;

[0036] (3) Dissolve 5 parts of chitosan in deionized water. The degree of deacetylation of chitosan is 95%. Add the solution mixture from step (2) to the chitosan solution and stir thoroughly for 12 hours to allow the metal coprecipitate to fully chelate with the chitosan and obtain mixed solution B.

[0037] (4) Place the mixed solution B in an oven and dry it at 80°C. Take it out and cool it to room temperature. After crushing and grinding, obtain a powdered defluorinating agent.

[0038] Example 2

[0039] This embodiment provides a defluoridating agent for treating fluoride-containing wastewater, which is prepared using chitosan as the biomolecular framework and magnesium chloride, titanium dioxide, zirconium chloride, aluminum chloride, polyferric sulfate, lanthanum chloride, and phthalic acid as blended raw materials;

[0040] The mass ratio of magnesium chloride: titanium dioxide: zirconium chloride: aluminum chloride: polyferric sulfate: lanthanum chloride: phthalic acid: chitosan is 6:3:3:10:5:30:2:3. The degree of deacetylation of chitosan is 95%.

[0041] The above-mentioned defluorinating agent is prepared by the following method, specifically including the following steps:

[0042] (1) Mix 6 parts magnesium chloride, 3 parts titanium dioxide, 3 parts zirconium chloride, 10 parts aluminum chloride, 5 parts polyferric sulfate, 20 parts lanthanum chloride and 2 parts phthalic acid and add them to deionized water. Stir thoroughly at 25°C for 6 hours to obtain mixed solution A.

[0043] (2) Slowly add mixed solution A dropwise into a 10% NaOH solution; the reaction produces a metal coprecipitate;

[0044] (3) Dissolve 3 parts of chitosan in deionized water. The degree of deacetylation of chitosan is 95%. Add the solution mixture from step (2) to the chitosan solution and stir thoroughly for 12 hours to allow the metal coprecipitate to fully chelate with the chitosan and obtain mixed solution B.

[0045] (4) Place the mixed solution B in an oven and dry it at 80°C. Take it out and cool it to room temperature. After crushing and grinding, obtain a powdered defluorinating agent.

[0046] Example 3

[0047] This embodiment provides a defluoridating agent for treating fluoride-containing wastewater, which is prepared using chitosan as the biomolecular framework and magnesium chloride, titanium dioxide, zirconium chloride, aluminum chloride, polyferric sulfate, cerium nitrate, and phthalic acid as blended raw materials;

[0048] The mass ratio of magnesium chloride: titanium dioxide: zirconium chloride: aluminum chloride: polyferric sulfate: cerium nitrate: phthalic acid: chitosan is 6:3:6:10:10:20:5:5. The degree of deacetylation of chitosan is 95%.

[0049] The above-mentioned defluorinating agent is prepared by the following method, specifically including the following steps:

[0050] (1) Mix 6 parts magnesium chloride, 3 parts titanium dioxide, 6 parts zirconium chloride, 10 parts aluminum chloride, 10 parts polyferric sulfate, 20 parts cerium nitrate and 1 part phthalic acid and add them to deionized water. Stir thoroughly at 25°C for 6 hours to obtain mixed solution A.

[0051] (2) Slowly add mixed solution A dropwise into a 10% NaOH solution; the reaction produces a metal coprecipitate;

[0052] (3) Dissolve 5 parts of chitosan in deionized water. The degree of deacetylation of chitosan is 95%. Add the solution mixture from step (2) to the chitosan solution and stir thoroughly for 12 hours to allow the metal coprecipitate to fully chelate with the chitosan and obtain mixed solution B.

[0053] (4) Place the mixed solution B in an oven and dry it at 80°C. Take it out and cool it to room temperature. After crushing and grinding, obtain a powdered defluorinating agent.

[0054] Comparative Example 1

[0055] Comparative Example 1 provides a defluorinating agent, the preparation process of which is mainly the same as that of Example 1, except that the mass ratio of magnesium chloride: titanium dioxide: zirconium chloride: aluminum chloride: polyferric sulfate: lanthanum nitrate: phthalic acid: chitosan is 3:3:3:5:5:12:10:5.

[0056] Comparative Example 2

[0057] Comparative Example 2 provides a defluorinating agent, the preparation process of which is mainly the same as that of Example 2, except that the mass ratio of magnesium chloride: titanium dioxide: zirconium chloride: aluminum chloride: polyferric sulfate: lanthanum chloride: phthalic acid: chitosan is 6:3:3:10:5:30:1:3.

[0058] Comparative Example 3

[0059] Comparative Example 3 provides a defluorinating agent whose preparation process is mainly the same as that of Example 3, except that it does not contain chitosan. After the metal coprecipitate is generated in step (2), the mixture in step (2) is placed directly in an oven and dried at 70°C. After grinding, a powdered defluorinating agent is obtained.

[0060] Application examples and comparative examples of the defluorinating agent of the present invention

[0061] 1. The method for defluorination using the defluorinating agent obtained in Example 1 specifically includes the following steps:

[0062] (1) The fluoride ion concentration of the fluoride-containing waste liquid was detected to be 30 mg / L, and the pH value of the wastewater was controlled between 3 and 7.

[0063] (2) Add a defluorinating agent to the fluoride-containing waste liquid until its concentration is 600 mg / L, and stir for 3 hours;

[0064] (3) Add 10% NaOH and 10% HCl to the wastewater of the reaction, and adjust the pH of the wastewater in the adjustment tank to 7.0-9.0;

[0065] (4) F in the wastewater after fluoride removal - If the content is <1mg / L, it can meet the emission standards.

[0066] 2. The method for defluorination using the defluorinating agent obtained in Example 2 specifically includes the following steps:

[0067] (1) The fluoride ion concentration of the fluoride-containing waste liquid was detected to be 10 mg / L, and the pH value of the wastewater was controlled between 3 and 7.

[0068] (2) Add a defluorinating agent to the fluoride-containing waste liquid until its concentration is 800 mg / L, and stir for 3 hours;

[0069] (3) Add 10% NaOH and 10% HCl to the wastewater of the reaction, and adjust the pH of the wastewater in the adjustment tank to 7.0-9.0;

[0070] (4) F in the wastewater after fluoride removal - If the content is <1mg / L, it can meet the emission standards.

[0071] 3. The method for defluorination using the defluorinating agent obtained in Example 3 specifically includes the following steps:

[0072] (1) The fluoride ion concentration of the fluoride-containing waste liquid was detected to be 20 mg / L, and the pH value of the wastewater was controlled between 3 and 7.

[0073] (2) Add a defluorinating agent to the fluoride-containing waste liquid until its concentration is 1000 mg / L, and stir for 3 hours;

[0074] (3) Add 10% NaOH and 10% HCl to the wastewater of the reaction, and adjust the pH of the wastewater in the adjustment tank to 7.0-9.0;

[0075] (4) F in the wastewater after fluoride removal - If the content is <1mg / L, it can meet the emission standards.

[0076] 4. The method for defluorination using the defluorinating agent obtained in Comparative Example 1 includes the following steps:

[0077] (1) The fluoride ion concentration of the fluoride-containing waste liquid was detected to be 30 mg / L, and the pH value of the wastewater was controlled between 3 and 7.

[0078] (2) Add a defluorinating agent to the fluoride-containing waste liquid until its concentration is 600 mg / L, and stir for 3 hours;

[0079] (3) Add 10% NaOH and 10% HCl to the wastewater of the reaction, and adjust the pH of the wastewater in the adjustment tank to 7.0-9.0;

[0080] (4) F in the wastewater after fluoride removal - The concentration was 8–12 mg / L, which is higher than the emission standard.

[0081] Analysis revealed that this was because, compared to Example 1, the proportion of rare earth materials added was lower, resulting in a lower effect of rare earth materials on F. - This is due to a decrease in the amount of adsorption.

[0082] 5. The method for defluorination using the defluorinating agent obtained in Comparative Example 2 specifically includes the following steps:

[0083] (1) The fluoride ion concentration of the fluoride-containing waste liquid was detected to be 10 mg / L, and the pH value of the wastewater was controlled between 3 and 7.

[0084] (2) Add a defluorinating agent to the fluoride-containing waste liquid until its concentration is 800 mg / L, and stir for 3 hours;

[0085] (3) Add 10% NaOH and 10% HCl to the wastewater of the reaction, and adjust the pH of the wastewater in the adjustment tank to 7.0-9.0;

[0086] (4) F in the wastewater after fluoride removal - The concentration is 3-5 mg / L, which is higher than the emission standard.

[0087] Analysis revealed that this was because, compared to Example 2, the proportion of organic matter added was lower, resulting in incomplete polymerization and co-precipitation of the metal copolymer and a decrease in the removal performance of fluoride ions.

[0088] 6. The method for defluorination using the defluorinating agent obtained in Comparative Example 3 includes the following steps:

[0089] (1) The fluoride ion concentration of the fluoride-containing waste liquid was detected to be 20 mg / L, and the pH value of the wastewater was controlled between 3 and 7.

[0090] (2) Add a defluorinating agent to the fluoride-containing waste liquid until its concentration is 1000 mg / L, and stir for 3 hours;

[0091] (3) Add 10% NaOH and 10% HCl to the wastewater of the reaction, and adjust the pH of the wastewater in the adjustment tank to 7.0-9.0;

[0092] (4) F in the wastewater after fluoride removal - The concentration was 10–12 mg / L, which is higher than the emission standard.

[0093] Analysis revealed that this was because, compared to Example 3, Comparative Example 3 did not use chitosan as the framework for the metal co-precipitate, resulting in a lack of framework support for the metal co-precipitate and a lack of adsorption capacity for fluoride ions, thus reducing the removal performance of fluoride ions.

[0094] 7. The treatment effect of adding a defluorinating agent to the fluoride-containing wastewater from a semiconductor company is shown in Table 1.

[0095] Table 1 Comparison of the defluorination effects of defluorinating agents on semiconductor fluoride-containing wastewater

[0096]

[0097] As shown in Table 1, the defluorination agent of this invention achieves a stable defluorination rate of over 95%, demonstrating high efficiency and consistent defluorination effect. Its defluorination efficiency is significantly higher than that of commercially available defluorination agents and commercially available activated alumina.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A defluoridating agent for treating fluoride-containing wastewater, characterized in that, Chitosan is used as biomolecular skeleton, and magnesium salt, titanium salt, zirconium salt, aluminum salt, iron salt, rare earth material and organic material are used as blending raw materials to prepare the defluorination agent; The mass ratio of the magnesium salt, the titanium salt, the zirconium salt, the aluminum salt, the iron salt, the rare earth material, the organic material and the chitosan is 1-30:1-30:2-20:2-10:2-10:20-50:2-10:1-10. The defluorination agent is prepared by the following method: (1) The magnesium salt, the titanium salt, the zirconium salt, the aluminum salt, the iron salt, the rare earth material and the organic material are added into water according to the mass ratio, and stirred uniformly at room temperature after being dissolved sufficiently to obtain a mixed solution; (2) The mixed solution is slowly dropped into sodium hydroxide solution to generate metal ion co-precipitate; (3) The mixture prepared in step (2) is added into chitosan solution, and stirred uniformly after being dissolved sufficiently to make the inorganic metal ion chelate with the chitosan to obtain a mixed solution; (4) The mixed solution is dried, cooled to room temperature, and ground to obtain a powder defluorination agent.

2. The fluorine removal agent for treating fluorine-containing wastewater according to claim 1, characterized by, The mass ratio of the magnesium salt, the titanium salt, the zirconium salt, the aluminum salt, the iron salt, the rare earth material, the organic material and the chitosan is 3-6:3-6:3-6:5-10:5-10:20-30:2-5:3-5.

3. The fluorine removal agent for treating fluorine-containing wastewater according to claim 1, wherein The magnesium salt includes at least one of magnesium chloride, magnesium sulfate, magnesium citrate and magnesium acetate; the titanium salt includes at least one of titanium dioxide, titanium tetrachloride, titanium sulfate and titanium oxysulfate; the zirconium salt includes at least one of zirconium dioxide, zirconium chloride, zirconium silicate and zirconium sulfate; the aluminum salt includes at least one of aluminum chloride, aluminum sulfate, alum, aluminum oxide, aluminum hydroxide, calcium aluminate, sodium aluminate and polyaluminum chloride; the iron salt includes at least one of iron sulfate, iron chloride, aluminum-iron chloride, iron oxide, magnetite, iron hydroxide and polyaluminum sulfate; the rare earth material is any one of lanthanum nitrate, lanthanum chloride, lanthanum oxide, lanthanum hydroxide, cerium nitrate, cerium chloride, cerium oxide or cerium hydroxide; and the organic material is any one of oxalic acid, tartaric acid, citric acid, naphthalene dicarboxylic acid, 1,4-butane dicarboxylic acid, 1,4-butene dicarboxylic acid, acetylene dicarboxylic acid, benzenedicarboxylic acid, 1,2-benzenedicarboxylic acid, 1,3-benzenedicarboxylic acid, acetylene dicarboxylic acid, acetic acid, ethyl acetate or chloroacetic acid.

4. The fluorine removal agent for treating fluorine-containing wastewater according to claim 1, wherein The stirring time in step (1) is 3-10 hours.

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