Preparation process of composite defluorination agent

Abstract

This invention discloses a preparation process for a composite defluorinating agent, belonging to the field of water treatment technology. The process involves dissolving polyethylene glycol in water, adding nano-hydroxyapatite, and stirring to obtain polyethylene glycol-modified nano-hydroxyapatite; hydrolyzing a silane coupling agent in an ethanol-water solution, adding the polyethylene glycol-modified nano-hydroxyapatite, and reacting to obtain silane coupling agent-polyethylene glycol-modified nano-hydroxyapatite; adding the silane coupling agent-polyethylene glycol-modified nano-hydroxyapatite to a hexadecyltrimethylammonium bromide solution and stirring to obtain composite-modified nano-hydroxyapatite; adding the composite-modified nano-hydroxyapatite and β-cyclodextrin to a sodium hydroxide solution, adding a crosslinking agent and an emulsifier, and reacting to obtain composite sustained-release microspheres; adding Fe3O4 powder to an ethanol-water solution, adding the composite sustained-release microspheres, and adding NaOH solution dropwise in a constant-temperature water bath until the pH reaches 9; aging the resulting precipitate, washing with water, and drying to obtain the composite defluorinating agent.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a preparation process for a composite defluoridating agent. Background Technology

[0002] Hydroxyapatite has a unique crystal structure and its surface is rich in OH groups. - Ca 2+ ,PO4 3- Plasma has excellent ion exchange properties and can adsorb fluoride ions, heavy metal ions and organic pollutants, thereby effectively purifying industrial wastewater.

[0003] Hydroxyapatite is a natural mineralization of calcium apatite. Due to its strong ion exchange and biocompatibility, it is considered a potential adsorbent. However, conventional hydroxyapatite has a small specific surface area and few active sites, resulting in a low fluoride removal capacity. Summary of the Invention

[0004] The purpose of this invention is to provide a preparation process for a composite defluorinating agent to solve the problems existing in the background art.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A preparation process for a composite defluorinating agent includes the following steps:

[0007] (1) Modification of nano-hydroxyapatite with polyethylene glycol:

[0008] Dissolve 2-3 parts by weight of polyethylene glycol in water at a ratio of 1:10, add 10-20 parts by weight of nano-hydroxyapatite, stir and react at room temperature for 1-2 hours, and centrifuge and wash with water to obtain polyethylene glycol modified nano-hydroxyapatite.

[0009] (2) Modification of nano-hydroxyapatite with silane coupling agent:

[0010] 1-2 parts by weight of silane coupling agent are fully hydrolyzed in 10-20 parts by weight of ethanol aqueous solution (mass concentration of 10-20%), and the polyethylene glycol modified nano-hydroxyapatite obtained in step (1) is added and reacted for 1-2 hours. After centrifugation, silane coupling agent-polyethylene glycol modified nano-hydroxyapatite is obtained.

[0011] The silane coupling agent is one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane or 3-aminopropylmethyldiethoxysilane;

[0012] (3) Composite modification of nano-hydroxyapatite:

[0013] Add the silane coupling agent-polyethylene glycol modified nano-hydroxyapatite obtained in step (2) to 50-80 parts by weight of hexadecyltrimethylammonium bromide solution (concentration of 1 mmol / L), stir magnetically to mix evenly, wash with water and filter to obtain composite modified nano-hydroxyapatite;

[0014] (4) Preparation of composite sustained-release microspheres:

[0015] Add the composite modified nano-hydroxyapatite obtained in step (3) and 4-8 parts by weight of β-cyclodextrin to 60-80 parts by weight of sodium hydroxide solution (mass fraction 5-10%), stir and add 1-2 parts by weight of crosslinking agent epichlorohydrin and react for 1-2 hours, add 2-3 parts by weight of emulsifier (Tween-80: Span-80 mass ratio of 5:1), react at 70-80℃ for 1-2 hours, centrifuge and wash with water to obtain composite sustained-release microspheres;

[0016] (5) Preparation of composite defluorinating agents:

[0017] Add 1-2 parts by weight of Fe3O4 powder to an ethanol aqueous solution (mass fraction of 20-30%) at a ratio of 1:10, add the composite slow-release microspheres obtained in step (4), add 20% NaOH solution by mass dropwise in a constant temperature water bath at 70-80℃ until the pH is 9, age the obtained precipitate at 70-80℃ for 1-2 hours, wash with water and dry to obtain the composite defluorinating agent.

[0018] The beneficial effects of this invention are:

[0019] (1) In this invention, nonionic surfactant polyethylene glycol is used to modify nano-hydroxyapatite. Polyethylene glycol changes the surface morphology of nano-hydroxyapatite from short rod to a porous structure that is conducive to the exchange and adsorption of fluoride ions. The modification reduces the pore size of nano-hydroxyapatite, increases the specific surface area, and increases the number of mesopores and micropores. Therefore, the adsorption capacity and removal efficiency of fluoride ions by polyethylene glycol-modified nano-hydroxyapatite are higher than those of pure nano-hydroxyapatite.

[0020] (2) This invention modifies nano-hydroxyapatite with an amino-modified surface using a silane coupling agent; the silane coupling agent enhances the adsorption capacity of the nano-hydroxyapatite for fluorine. The coupling agent adheres to the surface of the hydroxyapatite, wherein the silanol groups (Si-OH) and hydrogen phosphate groups (HPO2) are present. -4Dehydration between the hydroxyl groups forms stable Si-OP chemical bonds, enhancing its dispersion stability in various liquid media. Furthermore, dehydration also occurs between the silanol groups and the -OH groups on the surface of nano-hydroxyapatite, forming chemical bonds. The hydrophilic end of the silane coupling agent can adsorb onto the surface of the nanoparticles and interact with the existing hydroxyl groups on the nanoparticle surface. Nano-hydroxyapatite modified in this way exhibits improved adsorption capacity and removal efficiency for fluorine.

[0021] (3) Nano-hydroxyapatite was modified with cetyltrimethylammonium bromide cationic surfactant. Surface modification technology can effectively improve the adsorption capacity of nano-hydroxyapatite. Surfactants have the property of reducing the surface tension of the solution, making the particles more hydrophilic. After modification, the adsorption capacity and defluorination efficiency are improved.

[0022] (4) Hydroxyapatite has a good defluorination effect, but its separation performance is poor and it is prone to agglomeration. To improve these problems, this invention uses β-cyclodextrin, epichlorohydrin, and emulsifiers to prepare slow-release microspheres to improve their adsorption capacity, defluorination efficiency, and regeneration performance. Hydroxyapatite is loaded onto β-cyclodextrin polymer microspheres to form slow-release microspheres. These microspheres can effectively improve the defluorination adsorption capacity and efficiency, and also achieve slow release of fluoride through the molecular structure and self-assembly properties of β-cyclodextrin. Furthermore, due to the good stability and cavity structure of the β-cyclodextrin polymer microspheres, these slow-release microspheres also have excellent regeneration performance.

[0023] (5) Magnetic microspheres were prepared using iron(III) oxide (Fe3O4). Iron(III) oxide is a magnetic material that can be easily separated by an external magnetic field, thus improving the reusability of the adsorbent. Furthermore, the presence of iron(III) oxide increases the stability and specific surface area of ​​the microspheres. These magnetic microspheres exhibit excellent magnetic response and dispersibility in aqueous solutions, with a specific surface area reaching 113 m². 2 / g, which means that the magnetic microspheres have high adsorption capacity and efficiency. At the same time, due to the slow-release properties of hydroxyapatite, these magnetic microspheres also have excellent recycling performance. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A preparation process for a composite defluorinating agent includes the following steps:

[0027] (1) Modification of nano-hydroxyapatite with polyethylene glycol:

[0028] Two parts by weight of polyethylene glycol were dissolved in water at a ratio of 1:10, and 10 parts by weight of nano-hydroxyapatite were added. The mixture was stirred and reacted at room temperature for 1 hour. The reaction product was centrifuged and washed with water to obtain polyethylene glycol-modified nano-hydroxyapatite.

[0029] (2) Modification of nano-hydroxyapatite with silane coupling agent:

[0030] One part by weight of silane coupling agent 3-aminopropyltriethoxysilane was fully hydrolyzed in 10 parts by weight of ethanol aqueous solution (mass concentration of 10%), and the polyethylene glycol modified nano-hydroxyapatite obtained in step (1) was added and reacted for 1 hour. After centrifugation, silane coupling agent-polyethylene glycol modified nano-hydroxyapatite was obtained.

[0031] (3) Composite modification of nano-hydroxyapatite:

[0032] Add the silane coupling agent-polyethylene glycol modified nano-hydroxyapatite obtained in step (2) to 50 parts by weight of hexadecyltrimethylammonium bromide solution (concentration of 1 mmol / L), stir magnetically to mix evenly, wash with water and filter to obtain composite modified nano-hydroxyapatite;

[0033] (4) Preparation of composite sustained-release microspheres:

[0034] Add the composite modified nano-hydroxyapatite obtained in step (3) and 4 parts by weight of β-cyclodextrin to 60 parts by weight of 5% sodium hydroxide solution, stir and add 1 part by weight of crosslinking agent epichlorohydrin to react for 1 hour, add 2 parts by weight of emulsifier (Tween-80: Span-80 mass ratio of 5:1), react at 70°C for 1 hour, centrifuge and wash with water to obtain composite sustained-release microspheres;

[0035] (5) Preparation of composite defluorinating agents:

[0036] Add 1 part by weight of Fe3O4 powder at a ratio of 1:10 to a 20% ethanol aqueous solution, add the composite slow-release microspheres obtained in step (4), add 20% NaOH solution dropwise in a 70°C constant temperature water bath until the pH is 9, age the resulting precipitate at 70°C for 1 hour, wash with water and dry to obtain the composite defluorinating agent.

[0037] Example 2

[0038] A preparation process for a composite defluorinating agent includes the following steps:

[0039] (1) Modification of nano-hydroxyapatite with polyethylene glycol:

[0040] Dissolve 3 parts by weight of polyethylene glycol in water at a ratio of 1:10, add 20 parts by weight of nano-hydroxyapatite, stir and react at room temperature for 2 hours, and centrifuge and wash with water to obtain polyethylene glycol modified nano-hydroxyapatite.

[0041] (2) Modification of nano-hydroxyapatite with silane coupling agent:

[0042] Two parts by weight of silane coupling agent 3-aminopropyltrimethoxysilane were fully hydrolyzed in 20 parts by weight of ethanol aqueous solution (mass concentration of 20%), and the polyethylene glycol modified nano-hydroxyapatite obtained in step (1) was added and reacted for 2 hours. After centrifugation, silane coupling agent-polyethylene glycol modified nano-hydroxyapatite was obtained.

[0043] (3) Composite modification of nano-hydroxyapatite:

[0044] Add the silane coupling agent-polyethylene glycol modified nano-hydroxyapatite obtained in step (2) to 80 parts by weight of hexadecyltrimethylammonium bromide solution (concentration of 1 mmol / L), stir magnetically to mix evenly, wash with water and filter to obtain composite modified nano-hydroxyapatite;

[0045] (4) Preparation of composite sustained-release microspheres:

[0046] Add the composite modified nano-hydroxyapatite obtained in step (3) and 8 parts by weight of β-cyclodextrin to 80 parts by weight of sodium hydroxide solution (mass fraction 5-10%), stir and add 2 parts by weight of crosslinking agent epichlorohydrin to react for 2 hours, add 3 parts by weight of emulsifier (Tween-80: Span-80 mass ratio of 5:1), react at 80℃ for 2 hours, centrifuge and wash with water to obtain composite sustained-release microspheres;

[0047] (5) Preparation of composite defluorinating agents:

[0048] Two parts by weight of Fe3O4 powder were added to an ethanol aqueous solution (mass fraction of 30%) at a ratio of 1:10. The composite slow-release microspheres obtained in step (4) were added, and 20% NaOH solution was added dropwise in a constant temperature water bath at 80°C until the pH reached 9. The resulting precipitate was aged at 80°C for 2 hours, washed with water, and dried to obtain the composite defluorinating agent.

[0049] Example 3

[0050] A preparation process for a composite defluorinating agent includes the following steps:

[0051] (1) Modification of nano-hydroxyapatite with polyethylene glycol:

[0052] 2.5 parts by weight of polyethylene glycol were dissolved in water at a ratio of 1:10, and 15 parts by weight of nano-hydroxyapatite were added. The mixture was stirred and reacted at room temperature for 1.5 hours. The reaction product was centrifuged and washed with water to obtain polyethylene glycol-modified nano-hydroxyapatite.

[0053] (2) Modification of nano-hydroxyapatite with silane coupling agent:

[0054] 1.5 parts by weight of silane coupling agent 3-aminopropylmethyldiethoxysilane were fully hydrolyzed in 15 parts by weight of ethanol aqueous solution (mass concentration of 15%), and the polyethylene glycol modified nano-hydroxyapatite obtained in step (1) was added and reacted for 1.5 h. After centrifugation, silane coupling agent-polyethylene glycol modified nano-hydroxyapatite was obtained.

[0055] (3) Composite modification of nano-hydroxyapatite:

[0056] The silane coupling agent-polyethylene glycol modified nano-hydroxyapatite obtained in step (2) was added to 65 parts by weight of hexadecyltrimethylammonium bromide solution (concentration of 1 mmol / L), and magnetically stirred to mix evenly. After washing with water and filtering, the composite modified nano-hydroxyapatite was obtained.

[0057] (4) Preparation of composite sustained-release microspheres:

[0058] Add the composite modified nano-hydroxyapatite obtained in step (3) and 7 parts by weight of β-cyclodextrin to 70 parts by weight of sodium hydroxide solution (mass fraction 8%), stir and add 1.5 parts by weight of crosslinking agent epichlorohydrin and react for 1.5 h, add 2.5 parts by weight of emulsifier (Tween-80: Span-80 mass ratio of 5:1), react at 75℃ for 1.5 h, centrifuge and wash with water to obtain composite sustained-release microspheres;

[0059] (5) Preparation of composite defluorinating agents:

[0060] 1.5 parts by weight of Fe3O4 powder were added to an ethanol aqueous solution (mass fraction of 25%) at a ratio of 1:10. The composite slow-release microspheres obtained in step (4) were added. 20% NaOH solution was added dropwise in a constant temperature water bath at 75°C until the pH reached 9. The resulting precipitate was aged at 75°C for 1.5 hours, washed with water, and dried to obtain the composite defluorinating agent.

[0061] Comparative Example 1: Compared with Example 3, no modification treatment was performed on the nano-hydroxyapatite.

[0062] Comparative Example 2: Compared with Example 3, the nano-hydroxyapatite was not modified with polyethylene glycol, and step (1) was omitted.

[0063] Comparative Example 3: Compared with Example 3, the nano-hydroxyapatite was not modified with a silane coupling agent, and step (2) was omitted.

[0064] Comparative Example 4: Compared with Example 3, the nano-hydroxyapatite was not modified with hexadecyltrimethylammonium bromide, and step (3) was omitted.

[0065] Comparative Example 5: Compared with Example 3, step (4) was omitted.

[0066] Comparative Example 6: Compared with Example 3, step (5) was omitted.

[0067] The performance of the composite defluorinating agents prepared in Examples 1-3 and Comparative Examples 1-6 was tested using the following methods, and the results are shown in Table 1:

[0068] Composite defluorinating agent for simulated wastewater F - Removal:

[0069] Prepare 2mg / LF - The solution was used to simulate actual fluoride-containing wastewater (containing 25 mg / L Na). + 10 mg / L NO3 - 10 mg / L SO4 2- 20 mg / L CO3 2- 40mg / LMg 2+ 15mg / L Ca 2+ 15mg / LK + 150mg / L Cl - Add 0.5 g / L of a composite defluorinating agent to simulated fluoride-containing wastewater, and react with shaking at 25°C for 3 hours. Determine the F content in the solution according to the standard method "Fluoride Reagent Spectrophotometry" (HJ488-2009). - Mass concentration.

[0070] q=(ρ0-ρ c V / m, η=(ρ0-ρ c ) / ρ0×100%

[0071] In the formula, q is the adsorption capacity of the composite defluorinating agent, mg / g; ρ0 is the initial F of the solution. - Mass concentration, mg / L; ρ C The remaining F after adsorption by the adsorbent - Mass concentration, mg / L; V is F - The initial volume of the solution is L; m is the mass of the composite defluorinating agent, g; and η is the defluorination efficiency of the composite defluorinating agent.

[0072] Composite defluorinating agent adsorbs F - Post-cycle regeneration performance:

[0073] Adsorbed F -The composite defluorinating agent was reacted with 0.2 mol / L NaOH for 12 h to obtain a regenerated composite defluorinating agent; the fluoride concentration (F) in the wastewater was measured after each use of the regenerated composite defluorinating agent. - Record the mass concentration and the number of regenerations of the compound defluoridator; it can then be used continuously several times, and the effluent F - The mass concentration meets the requirement of less than 1 mg / L as stipulated in the national standard, which can meet the actual needs.

[0074] Table 1

[0075]

[0076] As shown in Table 1, in Examples 1-3, by modifying nano-hydroxyapatite with polyethylene glycol, silane coupling agent, and hexadecyltrimethylammonium bromide, and then preparing the resulting composite modified nano-hydroxyapatite into slow-release microspheres and subjecting them to magnetic treatment, the resulting composite defluorinating agent effectively removes fluoride. - It has excellent adsorption capacity, fluoride removal efficiency, and number of regeneration cycles.

[0077] The nano-hydroxyapatite in Comparative Example 1 was not subjected to any modification treatment, resulting in an effect on F. - Its adsorption capacity, fluoride removal efficiency, and number of regeneration cycles are poor.

[0078] In Comparative Examples 2-4, the adsorption capacity and defluorination efficiency of the resulting composite defluorinating agents were reduced because polyethylene glycol, silane coupling agent, and hexadecyltrimethylammonium bromide were not used to modify the nano-hydroxyapatite.

[0079] In Comparative Examples 5-6, the adsorption capacity, defluorination efficiency, and number of cycles of the resulting composite defluorinating agent were reduced because the composite-modified nano-hydroxyapatite was not made into slow-release microspheres and magnetically treated.

[0080] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0081] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A preparation process for a composite defluorinating agent, characterized in that, Includes the following steps: (1) Composite modification of nano-hydroxyapatite: Add 10-20 parts by weight of silane coupling agent-polyethylene glycol modified nano-hydroxyapatite to 50-80 parts by weight of hexadecyltrimethylammonium bromide solution, stir magnetically to mix evenly, wash with water and filter to obtain composite modified nano-hydroxyapatite. (2) Preparation of composite sustained-release microspheres: Add the composite modified nano-hydroxyapatite obtained in step (1) and 4-8 parts by weight of β-cyclodextrin to 60-80 parts by weight of sodium hydroxide solution, stir and add 1-2 parts by weight of crosslinking agent to react for 1-2 hours, add 2-3 parts by weight of emulsifier, react at 70-80℃ for 1-2 hours, centrifuge and wash with water to obtain composite sustained-release microspheres. (3) Preparation of composite defluorinating agent: Add 1-2 parts by weight of Fe3O4 powder in an ethanol aqueous solution at a ratio of 1:10, add the composite slow-release microspheres obtained in step (2), add NaOH solution dropwise in a constant temperature water bath at 70-80℃ until the pH is 9, age the obtained precipitate at 70-80℃ for 1-2 hours, wash with water and dry to obtain the composite defluorinating agent. Preparation of silane coupling agent-polyethylene glycol modified nano-hydroxyapatite in step (1): 1-2 parts by weight of silane coupling agent were fully hydrolyzed in 10-20 parts by weight of ethanol aqueous solution. After adding polyethylene glycol modified nano-hydroxyapatite and reacting for 1-2 hours, the mixture was centrifuged to obtain silane coupling agent-polyethylene glycol modified nano-hydroxyapatite. The silane coupling agent is one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, or 3-aminopropylmethyldiethoxysilane.

2. The preparation process of the composite defluorinating agent according to claim 1, characterized in that, Preparation of the polyethylene glycol-modified nano-hydroxyapatite: Dissolve 2-3 parts by weight of polyethylene glycol in water at a ratio of 1:10, add 10-20 parts by weight of nano-hydroxyapatite, stir and react at room temperature for 1-2 hours, and centrifuge and wash with water to obtain polyethylene glycol modified nano-hydroxyapatite.

3. The preparation process of the composite defluorinating agent according to claim 1, characterized in that, In step (1), the concentration of the hexadecyltrimethylammonium bromide solution is 1 mmol / L.

4. The preparation process of the composite defluorinating agent according to claim 1, characterized in that, In step (2), the sodium hydroxide solution has a mass fraction of 5-10%, the crosslinking agent is epichlorohydrin, and the emulsifier is a mixture of Tween-80 and Span-80 in a mass ratio of 5:

1.

5. The preparation process of a composite defluorinating agent according to claim 1, characterized in that, In step (3), the mass fraction of the ethanol aqueous solution is 20-30%, and the mass fraction of the NaOH solution is 20%.

6. The preparation process of a composite defluorinating agent according to claim 1, characterized in that, The mass concentration of the ethanol aqueous solution is 10-20%.

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