Fluorine removal agent and preparation method thereof

Abstract

The invention discloses a fluorine removal agent and a preparation method thereof, and relates to the technical field of fluorine removal agents, the fluorine removal agent comprises the following components by weight: 5-10 parts of an aluminum salt, 5-10 parts of an iron salt, 15-20 parts of a rare earth material, sodium citrate and beta-cyclodextrin; the adding amount of the sodium citrate is 5%-10% of the total mass of the aluminum salt, the ferric salt and the rare earth material; the addition amount of the beta-cyclodextrin is 30%-50% of the mass of the sodium citrate; a synergistic system of sodium citrate and beta-cyclodextrin is introduced, the precipitation sequence of metal ions is regulated and controlled, meanwhile, beta-cyclodextrin captures competitive anions through molecular recognition and constructs a hydrogen bond network to block interference, and dynamic directional transmission and nuclear pore confinement crystallization of pollutants are further achieved through combination of a microsphere type and a porous particle type. Active site distribution is reconstructed on the molecular level, and a technical scheme with universality, economical efficiency and reliability is provided for complex fluorine-containing wastewater treatment.

Description

TECHNICAL FIELD

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

[0002] Fluorine-containing wastewater is common wastewater in the electronic industry, which has the characteristics of large water quantity and strong biological toxicity. As a key water treatment chemical agent, the defluorination agent plays a crucial role in the electronic industry and other fluorine-containing wastewater treatment fields. In view of the limitations of traditional defluorination methods such as chemical precipitation and coagulation sedimentation, such as unstable treatment effect, poor sludge settling performance, secondary pollution caused by metal ion back dissolution and other problems, in recent years, various new defluorination agents have been developed.

[0003] Although the new defluorination agent improves the problems of metal ion back dissolution and loose flocculation in the traditional process by loading aluminum, iron and rare earth metal co-precipitates on the chitosan skeleton, it still has defects such as mismatching of metal ion precipitation sequence leading to rare earth active sites being wrapped, interference of competitive ions such as phosphate in high-salinity wastewater with the adsorption process, and slow settling of loose sludge structure, which restricts its stability in complex water quality. SUMMARY

[0004] The embodiments of the present application provide a defluorination agent and a preparation method thereof, which solve the problems of metal ion precipitation disorder, poor anti-interference and loose flocculation of the defluorination agent in the prior art. By introducing a synergistic system of sodium citrate and β-cyclodextrin, the metal ion precipitation sequence is regulated, and the β-cyclodextrin captures competitive anions through molecular recognition and constructs a hydrogen bond network to block interference. The combination of microspheres and porous particles of the β-cyclodextrin further realizes dynamic directional transport and nuclear pore limited crystallization of pollutants, reconstructs the active site distribution at the molecular level, and improves the stability of the defluorination agent, thereby providing a technical solution with universality, economy and reliability for complex fluorine-containing wastewater treatment.

[0005] The embodiments of the present application provide a defluorination agent, which comprises, by weight: 5-10 parts of an aluminum salt, 5-10 parts of an iron salt, 15-20 parts of a rare earth material, sodium citrate and β-cyclodextrin; The addition amount of the sodium citrate is 5%-10% of the total mass of the aluminum salt, the iron salt and the rare earth material; The addition amount of the β-cyclodextrin is 30%-50% of the mass of the sodium citrate; The β-cyclodextrin includes microspherical β-cyclodextrin and porous particulate β-cyclodextrin, and the mass ratio of the two is 1:4; The particle size of the microspherical β-cyclodextrin is 0.45-0.55 μm, and the surface is modified by a sulfonic acid group; The particle size of the porous particulate β-cyclodextrin is 140-160 μm, and the pore size is 2-10 nm.

[0006] Further, the microsphere type β-cyclodextrin is prepared by a spray drying method, an inlet temperature is 75-85℃, a sulfonating agent is propylene sulfite, and a molar ratio of β-cyclodextrin to propylene sulfite is 1:1.1-1.3.

[0007] Further, the porous particle type β-cyclodextrin is prepared by using 20nm silica as a template, calcining at 450℃, and then cross-linking by glutaraldehyde, and a molar ratio of β-cyclodextrin to glutaraldehyde is 1:0.55-0.65.

[0008] Further, the porous particle type β-cyclodextrin is coated to form a core-shell structure, including a core layer and a shell layer. The core layer is the porous particle type β-cyclodextrin cross-linked by glutaraldehyde. The shell layer is a pH-responsive layer formed by embedding sodium citrate in calcium alginate.

[0009] Further, the aluminum salt is aluminum chloride, the iron salt is polyaluminum chloride, and the rare earth material is at least one of lanthanum nitrate and cerium chloride.

[0010] A preparation method of a defluorination agent, specifically including the following steps: (a) dissolving an aluminum salt, an iron salt, a rare earth material, sodium citrate and β-cyclodextrin in water and stirring; (b) dropping the mixed solution into a NaOH solution to generate a precipitate by controlling the end point pH; (c) centrifugally separating the precipitate, washing and drying to obtain a powder; (d) dissolving chitosan in acetic acid, adding the powder of step (c) and stirring to obtain a mixed solution; (e) pre-freezing the mixed solution and vacuum freeze-drying to obtain the defluorination agent.

[0011] Further, in step (b), the mixed solution is dropped into a 10% NaOH solution at a speed of ≤10mL / min, and the end point pH is controlled to be 8.0-8.5.

[0012] Further, in step (a), the aluminum salt, the iron salt and the rare earth material are first dissolved in water, then the porous particle type β-cyclodextrin is added and stirred for 30 minutes, and finally the microsphere type β-cyclodextrin is added and stirred for 2 hours, and the water temperature is maintained at 25±3℃.

[0013] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: By the action of sodium citrate and β-cyclodextrin, the precipitation sequence is restructured at the molecular level, ion competition is blocked, and the crystallization process is optimized, realizing the triple breakthrough of defluorination efficiency, sludge performance and stability, solving the defects of metal precipitation layering and lack of anti-interference mechanism, leading to insufficient utilization of active sites, loose flocculation structure, and difficulty in stable standard in complex water quality; By introducing 0.5 μm microsphere type β-cyclodextrin and 150 μm porous particle type β-cyclodextrin, the problems of single β-cyclodextrin for colloidal PO4 3- low interception, traditional flocculation weak shear resistance, low temperature La 3+ nucleation slow, etc. are solved, realizing the effects of greatly improving defluorination efficiency, improving sludge settling performance, improving the tolerance of the system to colloidal pollutants, and prolonging the cycle life; By constructing a core-shell structure β-CD and sodium citrate composite carrier, 150 μm cross-linked porous β-cyclodextrin is used as the core layer to load calcium ions to form a precipitation microcavity, and a pH-responsive shell layer is coated with calcium alginate to embed sodium citrate. Through pH-triggered targeted release and energy feedback closed-loop cascade reaction, the comprehensive performance of the defluorination agent is further improved. The carrier intelligently swells and releases sodium citrate into the core pores when the system pH is greater than 7.5, matching the process of rare earth precipitation; simultaneously, 0.5 μm sulfonated microspherical β-cyclodextrin dynamically captures pollutants and releases reaction heat, and the heat energy is conducted through the core-shell to increase the temperature in the pores, drive the nucleation rate of lanthanum ions to increase, and guide the deposition of aluminum-iron hydroxide in 2-10 nm pores to form LaF3 crystal nucleus and Al(OH)3-coated single crystal active structure. DETAILED DESCRIPTION

[0014] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the use herein of the terms "and / or" includes a set of one or more associated listed items, in any and all combinations.

[0015] Example One: A defluorination agent, comprising the following components by weight: Aluminum salt (aluminum chloride): 5-10 parts; Iron salt (polyaluminum chloride): 5-10 parts; Rare earth material (lanthanum nitrate / cerium chloride, etc.): 15-20 parts; Sodium citrate (C6H5Na3O7): 5%-10% of the total mass of aluminum salt, iron salt, and rare earth material; β-cyclodextrin (β-CD): 30%-50% of the mass of sodium citrate; The preparation method of the defluorination agent comprises the following steps: Step 1. Add aluminum salt, iron salt, rare earth material, sodium citrate, and β-CD into deionized water; stir at a speed of 200-300 rpm for 3 hours at a water temperature of 25±3℃ to form a uniform solution; Step 2. Add the mixture obtained in Step 1 into a 10% NaOH solution at a rate of ≤10 mL / min; monitor the pH in real time and control the end-point pH to be 8.0-8.5; continue stirring for 30 minutes after the addition is completed; Step 3. Centrifuge the precipitate (10000 rpm, 10 minutes); wash with deionized water until the pH of the filtrate is 6.5-7.5 and the conductivity is ≤100 μS / cm; Dry at 70-80℃ until the weight is constant, and grind to a powder of 100-200 mesh; Step 4. Add chitosan (degree of deacetylation 80%-95%) into acetic acid at a mass ratio of chitosan: acetic acid = 1:0.5; dilute with deionized water to a solid content of 10% and stir to dissolve; Add the powder of Step 3 into the chitosan solution and stir at 200 rpm for 12 hours; Step 5: Pour the mixture into a mold and freeze at -80℃ for 6 hours; Set the freeze dryer to -45℃, vacuum degree ≤10 Pa, and dry for 24 hours to obtain a loose powder of the fluoride removal agent.

[0016] Experiments were conducted on the technical solutions of the present embodiment: 1. The total mass of the metal = 40g (aluminum salt + iron salt + rare earth), aluminum chloride: 10.0g, polyferric chloride: 10.0g, lanthanum nitrate: 20.0g; The experimental groups and the amounts of additives (with the total amount of metal fixed at 40g) are shown in Table 1 below: Table 1

[0017] 2. Performance test method: (1) Fluoride removal efficiency test: Simulated wastewater: Ca 2+ F - =10mg / L, Na2SO4 (SO4 2- =100mg / L) and Na3PO4 (PO4 3- =5mg / L) were added to simulate competitive ions; Operation: Take 500mL of simulated wastewater and add 300ppm of fluoride removal agent; Fast stirring (300r / min, 30min), then slow stirring (100r / min, 10min), and then standing for 30min; The supernatant was used to determine F by a fluorine ion electrode method (GB 7484-87) - Concentration.

[0018] (2) Sludge settling performance test: 100 mL of effluent from the flocculation tank was taken in a measuring cylinder, the sludge interface height change with time was recorded, and the settling velocity (m / h) was calculated; The settled sludge was taken, dried at 105 DEG C to constant weight, and the moisture content of the sludge was calculated (%).

[0019] The test results are shown in Table 2 as follows: Table 2

[0020] The technical solutions in the embodiments of the present application have at least the following technical effects or advantages: By introducing sodium citrate and β-cyclodextrin (β-CD), the problems of uneven metal coprecipitation, interference of multivalent anion competition and loose sludge floc structure are solved, the precipitation sequence is reconstructed at the molecular level, the ion competition is blocked, and the crystallization process is optimized, so that the fluorine removal efficiency, sludge performance and stability are improved.

[0021] Sodium citrate regulates the metal precipitation sequence by selective complexation, citrate and Al 3+ / Fe 3+ form a high-stability complex, and the complete precipitation pH is delayed from 4-6 to above 8.5; while the rare earth ions with weak complexing ability preferentially precipitate as crystal nuclei at pH 7.5-8.5, thereby forming a rare earth core-aluminum and iron shell ordered structure, the utilization rate of rare earth active sites is significantly improved, the application range of the fluorine removal agent is widened, and the water quality fluctuation resistance is enhanced; β-cyclodextrin avoids competition interference by molecular recognition, the hydrophobic cavity of β-CD encapsulates PO4 3- , and the outer wall hydroxyl forms a hydrogen bond network with citrate, so that the stability of the aluminum ion-citric acid complex is improved, the residual amount of PO4 3- is reduced, and the fluorine removal agent still maintains high efficiency in high-salinity wastewater with SO4 2- ≤200 mg / L and PO4 3- ≤10 mg / L; The combination of sodium citrate and β-CD produces a synergistic effect: After β-CD captures PO4 3- , the outer wall hydroxyl forms a hydrogen bond network with citrate, so that the binding energy of the aluminum ion-citric acid complex is significantly improved, and the anion competition is blocked, and the fluorine removal efficiency under PO4 3- interference is improved from 1.2 mg / L (sodium citrate alone) to 0.4 mg / L; After β-CD encapsulates PO4 3-The release of reaction heat locally raises the temperature of the system by 5°C, which promotes the La 3+ The nucleation rate is significantly improved at 35°C, and a high-crystallinity LaF3 rigid skeleton is formed first. At this time, the sodium citrate still dissolves Al 3+ / Fe 3+ and stabilizes it in a dissolved state. After the rare earth crystal nucleus is generated, Al 3+ / Fe 3+ is redeposited on the surface of the crystal nucleus to form a dense core-shell structure. This process drives the sludge settling speed from 0.7 m / h to 1.3 m / h, and the water content is reduced. The β-CD is adsorbed on the precipitation interface, and its rigid ring structure prevents Al(OH)3 colloid from wrapping the rare earth particles, ensuring that the aluminum-iron hydroxide is loaded on the surface of the rare earth crystal nucleus to form a uniform core-shell structure, so that the sludge floc density is increased from 1.2 g / cm 3 to 1.8 g / cm 3 , and the sludge volume is reduced.

[0022] The introduction of sodium citrate and β-CD has the following effects: 1. The removal efficiency of fluorine is improved, the utilization rate of active sites is doubled, the exposure of rare earth crystal nucleus is improved, Al / Fe shell provides auxiliary adsorption sites, and the adsorption capacity is significantly increased. The anti-interference is improved. Under the extreme conditions of PO4 3- = 10 mg / L and SO4 2- = 200 mg / L, the effluent F⁻ is stable at ≤0.5 mg / L; 2. The sludge is improved, and the floc density is improved: the LaF3 crystal nucleus formed by heat drive is the skeleton, and Al(OH)3 is wrapped outside, and the overall floc density is increased from 1.2 g / cm 3 to 1.8 g / cm 3 ; the water content and the settling speed are improved, and the sludge water content is reduced from 98.5% to 91.5%, and the settling speed is improved; 3. The cycle life is prolonged, and the pore stability is enhanced. The 2-5 nm mesopores produced by the decomposition of β-CD in the freeze-drying process increase the specific surface area by 30%, delay the CaF2 blockage, inhibit the metal dissolution, and control the Al 3+ dissolution concentration below 0.05 mg / L.

[0023] Example Two: The above-mentioned Example One restructures the precipitation sequence, blocks ion competition, and optimizes the crystallization process at the molecular level through the action of sodium citrate and β-cyclodextrin, realizes the triple breakthrough of fluorine removal efficiency, sludge performance, and stability, solves the defects of missing metal precipitation layering and anti-interference mechanism, which leads to insufficient utilization of active sites, loose floc structure, and difficulty in stable compliance in complex water quality. To further improve the comprehensive performance of the fluorine removal agent, further improvements are made on the basis of Example One.

[0024] The β-CD includes microspheric β-CD and porous granular β-CD; the mass ratio of the microspheric β-CD and the porous granular β-CD is 1:4; The particle size of the microspheric β-CD is 0.5 μm, and the particle size distribution range is 0.45-0.55 μm; the surface is modified by a sulfonic acid group (-SO3H); The microspheric β-CD is prepared by a spray drying method, the inlet temperature is controlled to be 75-85 ℃, propene sultone is used as a sulfonation reagent, and the molar ratio of β-cyclodextrin to propene sultone is 1:1.1-1.3; The average particle size of the porous granular β-CD is 150 μm, and the particle size distribution range is 140-160 μm; the porosity is 35±5%, and the pore size is 2-10 nm; the porous granular β-CD is crosslinked by glutaraldehyde (the crosslinking degree is 0.55-0.65 mol / mol); The porous granular β-CD is prepared by using silica nanospheres with a particle size of 20 nm as a template, calcining at 450 ℃ to remove the template, and then crosslinking by glutaraldehyde, and the molar ratio of β-cyclodextrin to glutaraldehyde is 1:0.55-0.65; The microspheric β-CD and the porous granular β-CD are added in the following manner, Step 1. Al salts, Fe salts, and rare earths are added to 200 mL of deionized water, and stirred at 200 rpm to dissolve; First, the porous granular β-CD is added, and stirred at 200 rpm for 30 minutes to construct a macroscopic skeleton; Then, the microspheric β-CD is added, and stirred at 300 rpm for 2 hours, and the system temperature is raised to 32±1 ℃, and the β-CD is exothermic; Sodium citrate is added, the water temperature is maintained at 25±3 ℃, and the total stirring time is 3 hours.

[0025] Based on the above technical solutions, experiments are carried out on the basis of Example 1 Experimental D2, as Experimental D4, the difference between D4 and D2 is that the β-CD in D4 includes microspheric β-CD and porous granular β-CD; the mass ratio of the microspheric β-CD and the porous granular β-CD is 1:4, and the detection results are shown in Table 3;

[0026] The technical solutions in the above embodiments have at least the following technical effects or advantages: Single β-cyclodextrin can only capture dissolved PO4 3- For colloidal PO4 3- The interception rate is low, the traditional floc has weak shear resistance, is easy to break under high flow rate, and leads to attenuation of the sedimentation efficiency, and La 3+Nucleation is slow, affecting the efficiency of active site generation. The above problems are solved by introducing a combination of 0.5 μm microspheres type β-cyclodextrin and 150 μm porous particle type β-cyclodextrin.

[0027] The introduction of a combination of 0.5 μm sulfonated microspheres β-cyclodextrin and 150 μm cross-linked porous particle β-cyclodextrin realizes a technical breakthrough by constructing a mechanism of dynamic capture, directional transport and limited precipitation. The sulfonic acid groups on the surface of the microspheres instantaneously capture dissolved phosphate ions through electrostatic attraction, and simultaneously release reaction heat to drive rare earth ions to accelerate nucleation. The particles physically intercept colloidal pollutants with rigid skeletons and precise pore sizes, and the pre-installed citrate-aluminum ion complex trap in the pores realizes irreversible locking of pollutants. Through the synergistic effect of the directional transport path mediated by Brownian motion, aluminum ions are precisely positioned in the particle pore reaction zone under the guidance of the sodium citrate hydrogen bond network, avoiding competitive interference while ensuring complete exposure of rare earth crystal nuclei and limited deposition of aluminum-iron hydroxide.

[0028] The 0.5 μm microspheres type β-cyclodextrin generates strong electrostatic attraction through its surface sulfonic acid groups, efficiently capturing dissolved phosphate ions. Its nanoscale size ensures an ultra-high diffusion rate, while the heat released by the inclusion reaction drives the local temperature to rise to 35°C, significantly increasing the nucleation rate of lanthanum ions. The 150 μm porous particle type β-cyclodextrin forms a micron-sized interception network with a cross-linked rigid skeleton and pore size, physically capturing colloidal pollutants. Its high porosity skeleton provides an irreversible precipitation reaction cavity for the citrate-aluminum ion complex trap; The combination of microspheres type β-cyclodextrin and porous particle type β-cyclodextrin realizes directional transport from dynamic capture to deep fixation. The PO4 3- Through Brownian motion, it is carried into the pores of the particles and locked by the pre-installed citrate-aluminum ion complex trap in the pores, avoiding the competitive interference caused by the escape of colloidal pollutants in traditional processes. The heat conducted from the microspheres to the particle skeleton uniformly raises the temperature inside the pores, simultaneously optimizing the kinetic matching degree of lanthanum ion nucleation and aluminum ion precipitation. The particle skeleton resists water flow shear force, protecting the complete growth of rare earth crystal nuclei; The carboxyl groups of sodium citrate form a hydrogen bond network with the hydroxyl groups on the surface of the particle β-cyclodextrin, directing aluminum ions into the pores of the particles to form a combination of citrate-aluminum ion-β-cyclodextrin, blocking PO4 3- competition for active sites; The synergy of microspherical β-cyclodextrin and porous particulate β-cyclodextrin is not a functional superposition, but a directional transport path of pollutants through Brownian motion, which can transport dissolved phosphate ions captured by microspheres to the pores of the particles, and under the guidance of the hydrogen bond network constructed by sodium citrate, aluminum ions are positioned in the pore reaction zone, avoiding colloidal interference while realizing the complete exposure of rare earth crystal nucleus and the limited deposition of aluminum-iron hydroxide, thereby reconstructing the pollutant removal path at the molecular level. The combination of microspherical β-cyclodextrin and porous particulate β-cyclodextrin further improves the performance of the fluorine removal agent. In terms of fluorine removal efficiency, the hierarchical capture of dissolved and colloidal phosphate ions significantly improves the total removal rate, which increases from 84% to 94%, and the residual amount of phosphate is reduced to below 0.3 mg / L. The directional precipitation process ensures the exposure of rare earth active sites, further reduces the concentration of fluoride ions in the effluent, and improves the adsorption capacity. In terms of sludge performance, the particle skeleton gives the flocculent concrete a dense structure, which improves the settling rate, and the permanent skeleton formed by limited crystallization in the pores can prevent the flocculent from loosening. In terms of system tolerance, the upper limit of colloidal pollutant tolerance is expanded, and the application range is further improved. The cross-linked particle skeleton prolongs the service life. The mechanism of dynamic capture, directional transport, and limited precipitation provides a technical solution with universality, economy, and engineering reliability for the treatment of high-toxicity fluorine-containing wastewater.

[0029] Example Three: By introducing a combination of 0.5 μm microspherical β-cyclodextrin and 150 μm porous particulate β-cyclodextrin, the problems of single β-cyclodextrin for colloidal PO4 3- low interception, weak shear resistance of traditional flocculent, low-temperature La 3+ nucleation, and slow nucleation are solved, which realizes the effects of significantly improving fluorine removal efficiency, improving sludge settling performance, increasing the tolerance of colloidal pollutants, and prolonging the service life. To further improve the fluorine removal effect, further improvements are made based on Example Two.

[0030] The porous particulate β-cyclodextrin is coated to form a core-shell structure, including a core layer and a shell layer. The core layer is porous particulate β-cyclodextrin cross-linked with glutaraldehyde, and the shell layer is a pH-responsive layer formed by embedding sodium citrate in calcium alginate.

[0031] The preparation of the core-shell structure includes the following specific steps: (1) Core layer pretreatment: Take 150 μm porous β-CD particles and cross-link them with glutaraldehyde. Vacuum soak in 0.1 M CaCl2 solution for 30 minutes, load calcium ions in the pores and on the surface to form pre-calcified β-CD particles. (2) Shell coating: Put the pre-calcified β-CD particles into the fluidized bed, and pass in hot air at 40°C to maintain suspension; Atomized spray shell solution, 10% sodium alginate and 5% sodium citrate: Among them, the shell solution is a mixture of 10% sodium alginate and 5% sodium citrate, the atomization pressure is 0.2 MPa, the liquid spraying rate is 2 g / min, and the spraying wheel number is 8, with an interval of 3 minutes between each wheel; (3) Steam crosslinking and curing: Pass in 0.1M CaCl2 steam (65°C) for 20 minutes to crosslink the sodium alginate to form a gel network, forming a core-shell structure particle; Among them, the particle size of the core-shell structure particle is 185±5μm.

[0032] In the preparation process of the defluorination agent after introducing the core-shell structure particle, in step 2, the mixed solution obtained in step 1 is added dropwise to the 10% NaOH solution at a speed of ≤5 mL / min; the pH is monitored in real time, and the pH is controlled to rise from 6.0 to 8.5; after the dropwise addition is completed, continue to stir for 30 minutes; In step 3, the precipitate is separated by centrifugation (8000 rpm, 8 minutes); without grinding, the core-shell functional powder is directly obtained.

[0033] Based on the above embodiment technical scheme, experiments are carried out on the basis of example two experiment D4, as experiment D5, the difference between D5 and D4 is that the porous particle type β-CD is a core-shell structure particle, and the detection results are shown in Table 4;

[0034] The technical scheme in the above embodiments of the present application has at least the following technical effects or advantages: By modifying the porous particle type β-cyclodextrin into a core-shell structure, a β-CD core and a sodium citrate shell composite carrier is constructed, and on the basis of the double particle size synergistic mechanism, targeted slow release and energy feedback are further introduced, solving the problems of time sequence mismatching and low reaction heat energy utilization rate in the traditional process.

[0035] Through the core-shell structure, the spatial isolation and intelligent response of the functional components are realized, and the 150μm porous β-CD particle is used as a rigid carrier core layer, which provides a physical trapping network and a limited precipitation space through its crosslinked skeleton and precise pore size (2-10nm); the shell layer embeds sodium citrate through the sodium alginate-calcium ion crosslinking network to form a pH-responsive intelligent slow-release unit, when the pH of the system is greater than 7.5, the shell layer swells, and the sodium citrate is released into the core pore at a controllable rate, matching the rare earth precipitation; and the reaction heat captured by the microspherical β-CD is conducted efficiently through the core-shell interface, driving the temperature in the core pore to rise, so that the nucleation rate of lanthanum ions is further improved and the deposition path of aluminum-iron hydroxide is optimized simultaneously. At the molecular level, the on-demand release of sodium citrate avoids the disorder of the precipitation sequence caused by the premature complexation of aluminum and iron ions, ensuring the exposure of rare earth crystal nuclei; at the mesoscopic level, the nuclear pore confinement space enables the ordered deposition of aluminum and iron hydroxides within 2-10 nm pores, forming composite active sites of LaF3 and Al(OH)3 with single crystal structure, and the combination energy is improved to further improve the fluoride ion adsorption capacity; at the macro level, the mechanical strength and thermal energy feedback of the core-shell carrier enable the sludge skeleton density to be improved to 2.4 g / cm 3 , further breaking through the water content; among them, the dynamic capture of pollutants by microspheres releases heat energy which is efficiently converted by the core-shell structure, further improving the utilization rate, forming a process of pollutant capture, heat release, heat energy feedback and directional precipitation, solving the problems of energy dissipation and precipitation disorder in the process of discrete components; The targeted controlled release of sodium citrate by the core-shell carrier reduces the residual amount of phosphate to 0.05 mg / L, further improving the fluoride ion removal depth; the sludge water content is further broken through under the driving of the heat energy closed loop; the cross-linked core-shell skeleton anti-breakup characteristics further prolong the service life.

[0036] By constructing a core-shell structure β-CD and sodium citrate composite carrier, a 150 μm cross-linked porous β-cyclodextrin is used as the core layer to load calcium ions to form a precipitation microcavity, and a calcium alginate shell layer is used to embed the pH-responsive shell layer of sodium citrate, to realize the further improvement of the comprehensive performance of the fluoride removal agent through the cascade reaction of pH-triggered targeted slow release and energy feedback closed loop. The carrier intelligently swells and releases sodium citrate into the nuclear pore when the system pH is greater than 7.5, matching the process of rare earth precipitation; simultaneously, 0.5 μm sulfonated microspheres β-cyclodextrin dynamically captures pollutants and releases reaction heat, and the heat energy is conducted through the core-shell to increase the temperature in the pore, driving the nucleation rate of lanthanum ions to increase and guiding the limited directional deposition of aluminum and iron hydroxides within 2-10 nm pores, forming a single crystal active structure of LaF3 crystal nucleus and Al(OH)3 coating.

[0037] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A fluorine removing agent, characterized by comprising: By weight parts including: aluminum salt 5-10 parts, iron salt 5-10 parts, rare earth material 15-20 parts, sodium citrate and β-cyclodextrin; The addition amount of the sodium citrate is 5%-10% of the total mass of the aluminum salt, the iron salt and the rare earth material; The addition amount of the β-cyclodextrin is 30%-50% of the mass of the sodium citrate; The β-cyclodextrin includes microspherical β-cyclodextrin and porous granular β-cyclodextrin, and the mass ratio of the two is 1:4; The particle size of the microspherical β-cyclodextrin is 0.45-0.55 μm, and the surface is modified by a sulfonic acid group; The particle size of the porous granular β-cyclodextrin is 140-160 μm, and the pore size is 2-10 nm.

2. The fluorine removing agent according to claim 1, wherein The microspherical β-cyclodextrin is prepared by a spray drying method, the inlet temperature is 75-85℃, the sulfonating reagent is propylsulfonic acid lactone, and the molar ratio of the β-cyclodextrin to the propylsulfonic acid lactone is 1:1.1-1.

3.

3. The fluorine removing agent according to claim 2, wherein The porous granular β-cyclodextrin is templated by 20 nm silica, calcined at 450℃, crosslinked by glutaraldehyde, and the molar ratio of the β-cyclodextrin to the glutaraldehyde is 1:0.55-0.

65.

4. The fluorine removing agent according to claim 1, wherein The porous granular β-cyclodextrin is coated to form a core-shell structure, including a core layer and a shell layer; The core layer is the porous granular β-cyclodextrin crosslinked by glutaraldehyde; The shell layer is a pH-responsive layer formed by embedding sodium citrate in calcium alginate.

5. The fluorine removing agent according to claim 1, wherein The aluminum salt is aluminum chloride, the iron salt is polyaluminum chloride, and the rare earth material is at least one of lanthanum nitrate and cerium chloride.

6. A method for producing the fluorine removing agent according to any one of claims 1 to 5, characterized by, Specifically including the following steps: (a) Dissolve the aluminum salt, the iron salt, the rare earth material, the sodium citrate and the β-cyclodextrin in water and stir; (b) Drop the mixed solution into a NaOH solution to control the end point pH to generate a precipitate; (c) Centrifuge the precipitate, wash and dry to obtain a powder; (d) Dissolve chitosan in acetic acid, add the powder of step (c) and stir to obtain a mixed solution; (e) Pre-freeze the mixed solution and vacuum freeze-dry to obtain the product.

7. The method for producing a fluorine removing agent according to claim 6, wherein In step (b), the mixed solution is dropped into a 10% NaOH solution at a speed of ≤10 mL / min, and the end point pH is controlled at 8.0-8.

5.

8. The method for producing a fluorine removing agent according to claim 6, wherein In step (a), first dissolve the aluminum salt, the iron salt and the rare earth material in water, then add the porous granular β-cyclodextrin and stir for 30 minutes, and finally add the microspherical β-cyclodextrin and stir for 2 hours, maintaining the water temperature at 25±3℃.

Images