A fluorine removal agent, a preparation method and application thereof

Abstract

The application provides a fluorine removal agent and a preparation method and application thereof, and the preparation method comprises the following steps: (1) polyhydroxy carboxylic acid modification is conducted on attapulgite raw ore to obtain modified attapulgite; (2) the modified attapulgite, a hydroxyl carboxylic acid compound, a monomer salt inorganic nano material, a plasticizing agent, a containing agent, a flow agent and deionized water are mixed, and an intermediate solution is obtained after uniform stirring; (3) magnesium hydroxide aqueous solution is added dropwise into the intermediate solution until the pH of the solution reaches a target value, and the fluorine removal agent is obtained after solidification, washing and drying in sequence. The fluorine removal agent provided by the application comprises modified attapulgite and a polyhydroxy carboxylic acid-monosalt blend loaded on the surface of the modified attapulgite, can effectively treat fluorine-containing wastewater with low concentration and organic matter, improves the fluorine removal efficiency, simultaneously reduces the preparation cost, and is conducive to large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment, and relates to a defluorination agent, in particular to a defluorination agent, a preparation method thereof and application. BACKGROUND

[0002] Fluorine is an element widely existing in nature and has obvious biological toxicity. When the fluorine content in water exceeds the standard, it not only threatens the survival of aquatic organisms and destroys the ecological balance, but also has a serious impact on human health, such as causing dental caries, weakening the structure and strength of the skeleton, damaging the nervous system and the immune system, etc. The fluorine content in industrial wastewater, especially wastewater discharged from the metallurgy, semiconductor, pharmaceutical, chemical and material manufacturing industries, is the main reason for fluorine pollution in water bodies.

[0003] The chemical method of adding a defluorination agent to fluorine-containing wastewater to remove fluorine ions is the main means for treating fluorine-containing wastewater. This method is favored due to its high efficiency, easy operation and low cost, and has broad application prospects. At present, the commonly used defluorination agents mainly include various calcium salts, aluminum salts and magnesium salts, as well as composite agents prepared by mixing these salts with auxiliary materials. These composite agents mainly remove fluorine ions through chemical precipitation, that is, converting fluorine ions in water into insoluble fluorides, and then removing them through precipitation.

[0004] Although the existing defluorination agents have good effects in treating high-concentration fluorine-containing wastewater (fluorine ion concentration from several tens to several hundred milligrams per liter), the effects are often unsatisfactory in treating low-concentration fluorine-containing wastewater (fluorine ion concentration of several to tens of milligrams per liter). Especially when the wastewater contains a certain amount of organic matter, the organic matter is easy to react with the defluorination agent, further reducing the efficiency of treating low-concentration fluorine-containing wastewater containing organic matter.

[0005] Therefore, how to provide a defluorination agent and a preparation method thereof, effectively treat low-concentration fluorine-containing wastewater containing organic matter, improve the defluorination efficiency, and reduce the preparation cost, has become an urgent problem to be solved by the technical personnel in the field. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a defluorination agent, a preparation method thereof and application, which comprises modified attapulgite and a polyhydroxy carboxylic acid-monomer salt blend loaded on the surface of the modified attapulgite, can effectively treat low-concentration fluorine-containing wastewater containing organic matter, improve the defluorination efficiency, reduce the preparation cost, and is conducive to large-scale popularization and application.

[0007] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a defluorinating agent, the method comprising the following steps:

[0009] (1) Modified attapulgite is obtained by modifying the raw attapulgite ore with polyhydroxycarboxylic acid;

[0010] (2) Mix modified attapulgite, hydroxycarboxylic acid compound, monomeric salt inorganic nanomaterial, plasticizer, absorbent, dispersant and deionized water, and stir evenly to obtain an intermediate solution;

[0011] (3) Add magnesium hydroxide aqueous solution dropwise to the intermediate solution until the pH of the solution reaches the target value, and then proceed with solidification, washing and drying to obtain the defluorinating agent.

[0012] This invention modifies attapulgite with polyhydroxycarboxylic acid, resulting in abundant active sites on the modified surface. These active sites can chemically adsorb fluoride ions, thereby enhancing the fluoride removal capacity. Furthermore, by mixing hydroxycarboxylic acid compounds and monomeric salt inorganic nanomaterials, a long-chain polyhydroxycarboxylic acid and porous adsorption complex copolymer chelate are formed through the synergistic effect of multiple components. This further increases the specific surface area and pore volume, which is beneficial for increasing the contact area with fluoride ions in wastewater. The porous adsorption complex groups achieve strong adsorption, flocculation, and sedimentation for efficient removal of fluoride from water. It features thorough removal, low sludge production, economic efficiency, and stable compliance, making it suitable for treating various types of fluoride-containing wastewater and meeting green environmental protection requirements. Simultaneously, the long-chain polyhydroxycarboxylic acid has good organic matter compatibility; even in wastewater containing organic matter, the fluoride remover can effectively interact with fluoride ions, thus avoiding the negative impact of organic matter on fluoride removal efficiency, and has broad application prospects.

[0013] Preferably, the polyhydroxycarboxylic acid modification in step (1) includes the following steps:

[0014] (1.1) Disperse the raw attapulgite ore in deionized water to remove impurities, and filter to obtain the first attapulgite;

[0015] (1.2) The first attapulgite is dispersed in hydrochloric acid solution for acid treatment, and then filtered, washed with water, dried and crushed in sequence to obtain the second attapulgite;

[0016] (1.3) The second attapulgite is dispersed in deionized water and sodium pentahydroxyhexanoate is added. The mixture is first heated to a first temperature for evaporation treatment, and then heated to a second temperature for pressure polymerization reaction. After filtration, the modified attapulgite is obtained.

[0017] Since attapulgite ore contains impurities such as quartz and carbonates during its formation, and the presence of these impurities can adversely affect the defluorination performance of attapulgite, this invention thoroughly removes the above-mentioned impurities through sequential impurity removal and acid treatment, thereby further improving the defluorination performance of attapulgite.

[0018] Preferably, the concentration of the hydrochloric acid solution in step (1.2) is 0.5-1 mol / L, for example, it can be 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L or 1 mol / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the acid treatment time in step (1.2) is 1.5-2.5h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the mixing mass ratio of sodium pentahydroxyhexanoate and the second attapulgite in step (1.3) is (0.3-0.5):1, for example, it can be 0.3:1, 0.32:1, 0.34:1, 0.36:1, 0.38:1, 0.4:1, 0.42:1, 0.44:1, 0.46:1, 0.48:1 or 0.5:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the first temperature in step (1.3) is 100-110℃, for example, it can be 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃ or 110℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the evaporation time in step (1.3) is 30-60 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min or 60 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the second temperature in step (1.3) is 140-160°C, for example, it can be 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C or 160°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the absolute pressure of the pressurized polymerization reaction in step (1.3) is 0.2-0.4 MPa, for example, it can be 0.2 MPa, 0.22 MPa, 0.24 MPa, 0.26 MPa, 0.28 MPa, 0.3 MPa, 0.32 MPa, 0.34 MPa, 0.36 MPa, 0.38 MPa or 0.4 MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the time for the pressurized polymerization reaction in step (1.3) is 30-60 min, for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, 52 min, 54 min, 56 min, 58 min or 60 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the hydroxycarboxylic acid compound in step (2) includes sodium pentahydroxyhexanoate and / or polyhydroxyalkanoate.

[0027] Preferably, the degree of polymerization of the polyhydroxyalkanoate is 30-100, for example, it can be 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] Preferably, the monomeric salt inorganic nanomaterial in step (2) includes any one or at least two combinations of sodium salt, aluminum salt, iron salt or magnesium salt. Typical but non-limiting combinations include combinations of sodium salt and aluminum salt, combinations of aluminum salt and iron salt, combinations of iron salt and magnesium salt, combinations of sodium salt, aluminum salt and iron salt, or combinations of aluminum salt, iron salt and magnesium salt.

[0029] Preferably, the plasticizer in step (2) includes any one or a combination of at least two of lignin sulfonate, polycarboxylic acid, naphthalene sulfonate, aromatic aminosulfonate or sulfonated melamine-formaldehyde resin. Typical but non-limiting combinations include combinations of lignin sulfonate and polycarboxylic acid, combinations of polycarboxylic acid and naphthalene sulfonate, combinations of naphthalene sulfonate and aromatic aminosulfonate, or combinations of aromatic aminosulfonate and sulfonated melamine-formaldehyde resin.

[0030] Preferably, the containing agent in step (2) includes zirconium oxychloride and / or zirconium oxide.

[0031] Preferably, the flow agent in step (2) comprises polyisobutylene succinimide.

[0032] Preferably, the mixing mass ratio of the modified attapulgite, hydroxycarboxylic acid compound, monomeric salt inorganic nanomaterial, plasticizer, packing agent and flow agent in step (2) is (20-30):(15-25):(10-20):(2-5):(3-6):(1-4), for example, it can be 20:15:10:2:3:1, 22:17:12:2:3:1, 24:19:14:3:4:2, 26:21:16:4:5:3, 28:23:18:5:6:4 or 30:25:20:5:6:4, and more preferably (23-27):(18-22):(12-16):(3-4):(4-5):(2-3), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] Preferably, the target pH value of the solution in step (3) is 7-9, for example, it can be 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8 or 9, more preferably 8-9, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] Preferably, the drying method in step (3) includes freeze drying or heat drying.

[0035] Preferably, the heating and drying temperature is 75-85℃, for example, it can be 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃ or 85℃, and the time is 2-3h, for example, it can be 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3h, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] As a preferred embodiment of the first aspect of the present invention, the preparation method includes the following steps:

[0037] (1) Modification of attapulgite ore with polyhydroxycarboxylic acid, specifically including:

[0038] (1.1) Disperse the raw attapulgite ore in deionized water to remove impurities, and filter to obtain the first attapulgite;

[0039] (1.2) The first attapulgite is dispersed in a 0.5-1 mol / L hydrochloric acid solution and acid-treated for 1.5-2.5 h. Then, it is filtered, washed with water, dried and crushed to obtain the second attapulgite.

[0040] (1.3) Disperse the second attapulgite in deionized water and add sodium pentahydroxyhexanoate. Control the mixing mass ratio of sodium pentahydroxyhexanoate and the second attapulgite to be (0.3-0.5):1. First, heat to 100-110℃ for evaporation treatment for 30-60 min, then heat to 140-160℃ and carry out pressure polymerization reaction at 0.2-0.4 MPa for 30-60 min. After filtration, the modified attapulgite is obtained.

[0041] (2) A mixed modified attapulgite, hydroxycarboxylic acid compound, monomeric salt inorganic nanomaterial, plasticizer, absorbent, flow agent and deionized water are stirred evenly to obtain an intermediate solution; the hydroxycarboxylic acid compound includes sodium pentahydroxyhexanoate and / or polyhydroxyalkanoate, and the degree of polymerization of polyhydroxyalkanoate is 30-100; the monomeric salt inorganic nanomaterial includes any one or a combination of at least two of sodium salt, aluminum salt, iron salt or magnesium salt; the plasticizer includes any one or a combination of at least two of lignin sulfonate, polycarboxylic acid, naphthalene sulfonate, aromatic aminosulfonate or sulfonated melamine formaldehyde resin; the absorbent includes zirconium oxychloride and / or zirconium oxide; the flow agent includes polyisobutylene succinimide; the mixing mass ratio of the modified attapulgite, hydroxycarboxylic acid compound, monomeric salt inorganic nanomaterial, plasticizer, absorbent and flow agent is (23-27):(18-22):(12-16):(3-4):(4-5):(2-3);

[0042] (3) Add magnesium hydroxide aqueous solution dropwise to the intermediate solution until the solution pH reaches 8-9, and then proceed with solidification, washing and drying to obtain the defluorinating agent; the drying method includes freeze drying or heat drying, and the heat drying temperature is 75-85℃ and the time is 2-3h.

[0043] In a second aspect, the present invention provides a defluorinating agent, which is prepared by the preparation method described in the first aspect, and the defluorinating agent comprises a modified attapulgite and a polyhydroxycarboxylic acid-monomer salt blend loaded on the surface of the modified attapulgite.

[0044] Thirdly, the present invention provides an application of the defluorinating agent as described in the second aspect in the treatment of fluoride-containing wastewater.

[0045] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] This invention modifies attapulgite with polyhydroxycarboxylic acid, resulting in abundant active sites on the modified surface. These active sites can chemically adsorb fluoride ions, thereby enhancing the fluoride removal capacity. Furthermore, by mixing hydroxycarboxylic acid compounds and monomeric salt inorganic nanomaterials, a long-chain polyhydroxycarboxylic acid and porous adsorption complex copolymer chelate are formed through the synergistic effect of multiple components. This further increases the specific surface area and pore volume, which is beneficial for increasing the contact area with fluoride ions in wastewater. The porous adsorption complex groups achieve strong adsorption, flocculation, and sedimentation for efficient removal of fluoride from water. It features thorough removal, low sludge production, economic efficiency, and stable compliance, making it suitable for treating various types of fluoride-containing wastewater and meeting green environmental protection requirements. Simultaneously, the long-chain polyhydroxycarboxylic acid has good organic matter compatibility; even in wastewater containing organic matter, the fluoride remover can effectively interact with fluoride ions, thus avoiding the negative impact of organic matter on fluoride removal efficiency, and has broad application prospects. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0049] Example 1

[0050] This embodiment provides a defluorinating agent and its preparation method, the preparation method comprising the following steps:

[0051] (1) Modification of attapulgite ore with polyhydroxycarboxylic acid, specifically including:

[0052] (1.1) Disperse the raw attapulgite ore in deionized water to remove impurities, and filter to obtain the first attapulgite;

[0053] (1.2) The first attapulgite was dispersed in a 0.8 mol / L hydrochloric acid solution and acid-treated for 1.5 h. After being filtered, washed with water, dried and crushed, the second attapulgite was obtained.

[0054] (1.3) The second attapulgite was dispersed in deionized water and sodium pentahydroxyhexanoate was added. The mixing mass ratio of sodium pentahydroxyhexanoate and the second attapulgite was controlled to be 0.4:1. The temperature was first raised to 105℃ for evaporation treatment for 45 min, and then raised to 150℃ for pressure polymerization reaction at 0.4 MPa for 45 min. After filtration, the modified attapulgite was obtained.

[0055] (2) Mix 23 parts of modified attapulgite, 18 parts of sodium pentahydroxyhexanoate, 12 parts of sodium sulfate, 3 parts of sodium lignosulfonate, 4 parts of zirconium oxychloride, 2 parts of polyisobutylene succinimide (polymerization degree of 6000-10000) and deionized water, and stir evenly to obtain an intermediate solution.

[0056] (3) Add magnesium hydroxide aqueous solution dropwise to the intermediate solution until the solution pH reaches 8, and then proceed with solidification, washing and freeze drying to obtain the defluorinating agent.

[0057] The defluorinating agent obtained in this embodiment includes a modified attapulgite and a polyhydroxycarboxylic acid-monomer salt blend loaded on the surface of the modified attapulgite, forming a long-chain polyhydroxycarboxylic acid, porous structure adsorption complex copolymer chelate.

[0058] Example 2

[0059] This embodiment provides a defluorinating agent and its preparation method, the preparation method comprising the following steps:

[0060] (1) Modification of attapulgite ore with polyhydroxycarboxylic acid, specifically including:

[0061] (1.1) Disperse the raw attapulgite ore in deionized water to remove impurities, and filter to obtain the first attapulgite;

[0062] (1.2) The first attapulgite was dispersed in a 0.5 mol / L hydrochloric acid solution and acid-treated for 1.5 h. After being filtered, washed with water, dried and crushed, the second attapulgite was obtained.

[0063] (1.3) The second attapulgite was dispersed in deionized water and sodium pentahydroxyhexanoate was added. The mixing mass ratio of sodium pentahydroxyhexanoate and the second attapulgite was controlled to be 0.3:1. The temperature was first raised to 100℃ for evaporation treatment for 60 min, and then raised to 140℃ for pressure polymerization reaction at 0.4 MPa for 60 min. After filtration, the modified attapulgite was obtained.

[0064] (2) Mix 27 parts of modified attapulgite, 22 parts of polyhydroxyalkanoate (polymerization degree of 30-100), 16 parts of magnesium sulfate, 4 parts of sodium naphthalene sulfonate, 5 parts of zirconium oxide, 3 parts of polyisobutylene succinimide (polymerization degree of 6000-10000) and deionized water, and stir evenly to obtain an intermediate solution.

[0065] (3) Add magnesium hydroxide aqueous solution dropwise to the intermediate solution until the solution pH reaches 9, and then proceed with solidification, washing and heating drying (temperature 85℃, time 2h) to obtain the defluorinating agent.

[0066] The defluorinating agent obtained in this embodiment includes a modified attapulgite and a polyhydroxycarboxylic acid-monomer salt blend loaded on the surface of the modified attapulgite, forming a long-chain polyhydroxycarboxylic acid, porous structure adsorption complex copolymer chelate.

[0067] Example 3

[0068] This embodiment provides a defluorinating agent and its preparation method, the preparation method comprising the following steps:

[0069] (1) Modification of attapulgite ore with polyhydroxycarboxylic acid, specifically including:

[0070] (1.1) Disperse the raw attapulgite ore in deionized water to remove impurities, and filter to obtain the first attapulgite;

[0071] (1.2) The first attapulgite was dispersed in a 1 mol / L hydrochloric acid solution and acid-treated for 2.5 h. After being filtered, washed with water, dried and crushed, the second attapulgite was obtained.

[0072] (1.3) The second attapulgite was dispersed in deionized water and sodium pentahydroxyhexanoate was added. The mixing mass ratio of sodium pentahydroxyhexanoate and the second attapulgite was controlled to be 0.3:1. The temperature was first raised to 110℃ for evaporation treatment for 30 min, and then raised to 160℃ for pressure polymerization reaction at 0.3 MPa for 30 min. After filtration, the modified attapulgite was obtained.

[0073] (2) Mix 20 parts of modified attapulgite, 15 parts of sodium pentahydroxyhexanoate, 10 parts of ferric nitrate, 2 parts of sodium naphthalenesulfonate, 3 parts of zirconium oxychloride, 1 part of polyisobutylene succinimide (polymerization degree of 6000-10000) and deionized water, and stir evenly to obtain an intermediate solution.

[0074] (3) Add magnesium hydroxide aqueous solution dropwise to the intermediate solution until the solution pH reaches 7, and then successively pass through solidification, washing and heating drying (temperature 75℃, time 3h) to obtain the defluorinating agent.

[0075] The defluorinating agent obtained in this embodiment includes a modified attapulgite and a polyhydroxycarboxylic acid-monomer salt blend loaded on the surface of the modified attapulgite, forming a long-chain polyhydroxycarboxylic acid, porous structure adsorption complex copolymer chelate.

[0076] Example 4

[0077] This embodiment provides a defluorinating agent and its preparation method. Except for the deletion of step (1.2), i.e., the attapulgite is not acid-treated, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0078] Example 5

[0079] This embodiment provides a defluorinating agent and its preparation method. Except that only the pressure polymerization reaction is carried out in step (1.3), and no evaporation treatment is carried out before that, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0080] Comparative Example 1

[0081] This comparative example provides a defluorinating agent and its preparation method. Except for not modifying the attapulgite ore with polyhydroxycarboxylic acid, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0082] Comparative Example 2

[0083] This comparative example provides a defluorinating agent and its preparation method. Except for the absence of sodium sulfate in step (2), the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0084] Comparative Example 3

[0085] This comparative example provides a fluoride removal agent and its preparation method. Except that sodium lignosulfonate was not added in step (2), the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0086] Comparative Example 4

[0087] This comparative example provides a defluorinating agent and its preparation method. Except for the absence of zirconium oxychloride in step (2), the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0088] Comparative Example 5

[0089] This comparative example provides a defluorinating agent and its preparation method. Except for the absence of polyisobutylene succinimide in step (2), the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0090] Performance testing

[0091] Ten groups of fluoride-containing organic wastewater (1L each) were prepared, with the pH controlled at 6, fluoride ion concentration at 10 mg / L, and chemical oxygen demand (COD) at 500 mg / L. The defluorinating agents obtained in Examples 1-5 and Comparative Examples 1-5 were added to the above ten groups of fluoride-containing organic wastewater, with an addition amount of 10 g. The mixture was thoroughly stirred to suspend the defluorinating agent and ensure full contact with the fluoride-containing organic wastewater. After stirring for 5 hours, the residual fluoride ion concentration in the wastewater was measured. The relevant test results are shown in Table 1 below.

[0092] Table 1

[0093] Fluorine removing agent Residual fluorine ion concentration (mg / L) Fluorine removal efficiency (%) Example 1 0.129 98.71 Example 2 0.142 98.58 Example 3 0.135 98.65 Example 4 2.137 78.63 Example 5 2.351 76.49 Comparative Example 1 1.568 84.32 Comparative Example 2 1.383 86.17 Comparative Example 3 1.154 88.46 Comparative Example 4 1.302 86.98 Comparative Example 5 1.542 84.58

[0094] Therefore, this invention modifies attapulgite with polyhydroxycarboxylic acid, resulting in abundant active sites on the modified surface. These active sites can chemically adsorb fluoride ions, thereby enhancing the fluoride removal capacity. Furthermore, by mixing hydroxycarboxylic acid compounds and monomeric salt inorganic nanomaterials, a long-chain polyhydroxycarboxylic acid and porous adsorption complex copolymer chelate are formed through the synergistic effect of multiple components. This further increases the specific surface area and pore volume, which is beneficial for increasing the contact area with fluoride ions in wastewater. The porous adsorption complex groups achieve strong adsorption, flocculation, and sedimentation for efficient removal of fluoride from water. It features thorough removal, low sludge production, economic efficiency, and stable compliance, making it suitable for treating various types of fluoride-containing wastewater and meeting green environmental protection requirements. Simultaneously, the long-chain polyhydroxycarboxylic acid has good organic matter compatibility; even in wastewater containing organic matter, the defluorinating agent can effectively interact with fluoride ions, thus avoiding the negative impact of organic matter on defluorination efficiency, and has broad application prospects.

[0095] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a defluorinating agent, characterized in that, The preparation method includes the following steps: (1) Modification of attapulgite ore with polyhydroxycarboxylic acid, specifically including: (1.1) Disperse the raw attapulgite ore in deionized water to remove impurities, and filter to obtain the first attapulgite; (1.2) The first attapulgite is dispersed in a 0.5-1 mol / L hydrochloric acid solution and acid-treated for 1.5-2.5 h. Then, it is filtered, washed with water, dried and crushed to obtain the second attapulgite. (1.3) Disperse the second attapulgite in deionized water and add sodium pentahydroxyhexanoate. Control the mixing mass ratio of sodium pentahydroxyhexanoate and the second attapulgite to be (0.3-0.5):

1. First, heat to 100-110℃ for evaporation treatment for 30-60 min, then heat to 140-160℃ and carry out pressure polymerization reaction at 0.2-0.4 MPa for 30-60 min. After filtration, the modified attapulgite is obtained. (2) A mixed modified attapulgite, hydroxycarboxylic acid compound, monomeric salt inorganic nanomaterial, plasticizer, absorbent, flow agent and deionized water are stirred evenly to obtain an intermediate solution; the hydroxycarboxylic acid compound includes sodium pentahydroxyhexanoate and / or polyhydroxyalkanoate, and the degree of polymerization of polyhydroxyalkanoate is 30-100; the monomeric salt inorganic nanomaterial includes any one or a combination of at least two of sodium salt, aluminum salt, iron salt or magnesium salt; the plasticizer includes any one or a combination of at least two of lignin sulfonate, polycarboxylic acid, naphthalene sulfonate, aromatic aminosulfonate or sulfonated melamine formaldehyde resin; the absorbent includes zirconium oxychloride and / or zirconium oxide; the flow agent includes polyisobutylene succinimide; the mixing mass ratio of the modified attapulgite, hydroxycarboxylic acid compound, monomeric salt inorganic nanomaterial, plasticizer, absorbent and flow agent is (23-27):(18-22):(12-16):(3-4):(4-5):(2-3); (3) Add magnesium hydroxide aqueous solution to the intermediate solution until the solution pH reaches 8-9, and then proceed with solidification, washing and drying to obtain the defluorinating agent; the drying method includes freeze drying or heat drying, and the heat drying temperature is 75-85℃ and the time is 2-3h.

2. A defluorinating agent, characterized in that, The defluorinating agent is prepared by the preparation method described in claim 1, and the defluorinating agent comprises a modified attapulgite and a polyhydroxycarboxylic acid-monomer salt blend loaded on the surface of the modified attapulgite.

3. The application of the defluorinating agent as described in claim 2 in the treatment of fluoride-containing wastewater.