Fluorine removal agent for industrial sewage and preparation method of fluorine removal agent

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a fluorine removal agent for industrial sewage and a preparation method of the fluorine removal agent. The fluorine removal agent for industrial sewage is prepared from the following raw materials in parts by weight: 3-7 parts of sodium carboxymethyl cellulose, 20-25 parts of a modified attapulgite dispersion liquid, 30-35 parts of a polyaluminum solution, 10-15 parts of a hydroxyapatite nano dispersion liquid, 1-3 parts of chitosan quaternary ammonium salt, 0.5-2 parts of ammonium ferric sulfate, 1-3 parts of sodium potassium tartrate tetrahydrate, 1-3 parts of modified nano magnesium oxide and 2-4 parts of modified charcoal. 1-3 parts of Fe / Al modified kaolin material, and 70-90 parts of deionized water. The industrial sewage treatment agent has excellent stability and can quickly and efficiently remove fluoride in industrial sewage.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a defluorinating agent for industrial wastewater and its preparation method. Background Technology

[0002] Fluorine pollution caused by industrial wastewater discharge is becoming increasingly prominent in industries such as mining, photovoltaics, and semiconductors. For example, the fluoride content in industrial wastewater from gold mines can reach 20-50 mg / L, far exceeding the national emission standards.

[0003] Defluoridating agents are mainly divided into two categories: solid and liquid, each with different characteristics and applicable scenarios. Solid defluoridating agents can be used directly as filter media in adsorption filter tanks, achieving integrated adsorption and filtration with a high degree of process integration. However, they have many drawbacks, such as slow dissolution rate, which may prevent them from effectively removing fluoride in the emergency treatment of large quantities of industrial wastewater; uneven dispersion can also lead to incomplete localized defluoridation, affecting overall water quality. Liquid defluoridating agents, while convenient to use and capable of rapid mixing and reaction with industrial wastewater, suffer from poor stability. During storage, the active ingredients are prone to degradation, precipitation, and stratification, resulting in a significant decrease in defluoridation performance.

[0004] Chinese patent CN120794124A discloses a defluoridating agent for mine water, its preparation method, and its application. The preparation method includes the following steps: adding aluminum salts, calcium salts, magnesium salts, and iron salts to water and stirring; then adding a chelating agent, a hydroxycarboxylic acid compound, and a dispersant; heating to 40-60℃ and stirring to disperse; and maintaining the temperature. This defluoridating agent is in liquid form and contains a large amount of aluminum salts, calcium salts, magnesium salts, and iron salts. Its high efficiency depends on the long-chain porous structure formed by chelation, but it is prone to aggregation during storage, exhibiting poor chemical and storage stability.

[0005] Therefore, it is urgent to develop a highly stable and efficient defluorinating agent for the deep treatment of fluorides in industrial wastewater. Summary of the Invention

[0006] The purpose of this invention is to provide a defluorinating agent for industrial wastewater, which has excellent stability and can quickly and efficiently remove fluorides from industrial wastewater; this invention also provides a method for preparing the defluorinating agent for industrial wastewater.

[0007] The industrial wastewater defluoridator of the present invention is made from the following raw materials in parts by weight: 3-7 parts sodium carboxymethyl cellulose, 20-25 parts modified attapulgite dispersion, 30-35 parts polyaluminum solution, 10-15 parts hydroxyapatite nano dispersion, 1-3 parts chitosan quaternary ammonium salt, 0.5-2 parts ferric ammonium sulfate, 1-3 parts potassium sodium tartrate, 1-3 parts modified nano magnesium oxide, 2-4 parts modified biochar, 1-3 parts Fe / Al modified kaolin material, and 70-90 parts deionized water.

[0008] The solid content of the modified attapulgite dispersion is 20-30%, the mass concentration of the polyaluminum solution is 8-12%, and the solid content of the hydroxyapatite nano-dispersion is 10-15%.

[0009] The preparation method of modified attapulgite dispersion is as follows: attapulgite is pulverized, soaked in sulfuric acid solution, washed, and dried to obtain acidified attapulgite; then, the acidified attapulgite is mixed with hexadecyltrimethylammonium bromide solution, stirred and reacted, filtered to obtain modified attapulgite; deionized water is added to the modified attapulgite and dispersed at high speed to obtain the modified attapulgite dispersion; wherein, the pulverized particle size is 300-500 mesh, the mass concentration of the sulfuric acid solution is 8-12%, and the ratio of attapulgite to sulfuric acid solution is... The ratio of attapulgite to sulfuric acid solution is 1:4-8, with attapulgite measured in g and sulfuric acid solution measured in mL. The soaking temperature is 60-80℃, the soaking time is 3-5h, the mass concentration of hexadecyltrimethylammonium bromide solution is 5-10%, the mass ratio of acidified attapulgite to hexadecyltrimethylammonium bromide solution is 1:3-5, the stirring reaction temperature is 40-60℃, the stirring reaction time is 2-4h, the high-speed dispersion speed is 5000-8000 r / min, and the high-speed dispersion time is 30-60 min.

[0010] The preparation method of hydroxyapatite nano-dispersion is as follows: calcium chloride and diammonium hydrogen phosphate are dissolved in deionized water, and ammonia water is added under stirring to adjust the pH value before hydrothermal reaction. After cooling, centrifugation, and washing, nano-hydroxyapatite is obtained. Deionized water is added to the nano-hydroxyapatite, followed by sodium hexametaphosphate, and ultrasonic dispersion is performed to obtain hydroxyapatite nano-dispersion. The molar ratio of calcium chloride to diammonium hydrogen phosphate is 5:2.5-3.5. The ratio of calcium chloride to deionized water in the preparation of nano-hydroxyapatite is 1:40-60, with calcium chloride expressed in g and deionized water expressed in mL. The pH value is adjusted to 10-11, the hydrothermal reaction temperature is 150-180℃, the hydrothermal reaction time is 12-24 h, the amount of sodium hexametaphosphate added is 0.5-1.0% of the mass of nano-hydroxyapatite, the ultrasonic dispersion frequency is 40-60 kHz, and the ultrasonic dispersion time is 40-80 min.

[0011] The modified nano-magnesium oxide is prepared by dissolving rare earth salts and ligands in deionized water to obtain a rare earth complex solution; adding nano-magnesium oxide to anhydrous ethanol and ultrasonically dispersing it to obtain a nano-magnesium oxide suspension; then adding the rare earth complex solution dropwise to the nano-magnesium oxide suspension, stirring at a constant temperature, centrifuging and washing, drying, and grinding into powder to obtain modified nano-magnesium oxide; wherein the molar ratio of rare earth salt to ligand is 1:2-3, the mass ratio of rare earth salt to deionized water is 1:50-100, the rare earth salt is lanthanum nitrate or cerium sulfate, and the ligand is citric acid; the concentration of the nano-magnesium oxide suspension is 5-10 g / L. L; The ratio of nano-magnesium oxide to rare earth complex solution in nano-magnesium oxide suspension is 1:10-20, where nano-magnesium oxide is expressed in g and rare earth complex solution in mL; the ultrasonic dispersion power is 300-500W, and the ultrasonic dispersion time is 20-30min; the constant temperature stirring temperature is 50-70℃, the constant temperature stirring speed is 200-300rpm, and the constant temperature stirring time is 1-2h; the centrifugation speed is 3000-5000rpm, and the centrifugation time is 10-15min; the drying temperature is 80-120℃, and the drying time is 2-4h.

[0012] The modified biochar is prepared by soaking granular biochar in a nitric acid solution to obtain activated biochar. The activated biochar is then impregnated in a pyrrole solution, and FeCl3 solution is added dropwise to initiate a polymerization reaction. The mixture is then treated at high temperature under an ammonia atmosphere, washed sequentially with dilute hydrochloric acid and distilled water, and dried to obtain modified biochar. The concentration of the nitric acid solution is 15-20 wt.%; the ratio of biochar to nitric acid solution is 1:10-15; biochar is expressed in g and nitric acid solution in mL; the soaking temperature is 15-20℃; the soaking time is 10-12 h; and the concentration of the pyrrole solution is 5-20 g. / L; the mass ratio of activated biochar to pyrrole solution is 1:3-5; the impregnation temperature is 10-20℃, and the impregnation time is 15-20h; the ratio of activated biochar to FeCl3 solution is 1:20-30, with activated biochar in g and FeCl3 solution in mL; the concentration of FeCl3 solution is 14-16g / L; the polymerization reaction temperature is 10-12℃, and the polymerization reaction time is 20-22h; the high-temperature treatment temperature is 800-900℃, and the high-temperature treatment time is 2-3h; the drying temperature is 100-110℃, and the drying time is 10-12h.

[0013] The preparation method of Fe / Al modified kaolin material includes the following steps: (A) Dissolve ferric nitrate and aluminum isopropoxide in anhydrous ethanol, add ammonia to adjust the pH, and stir at a constant temperature to obtain Fe / Al sol; (B) Kaolin was added to anhydrous ethanol and ultrasonically dispersed to obtain a suspension. The suspension was then added to Fe / Al sol, stirred, allowed to stand, dried, calcined, and ground to obtain Fe / Al modified kaolin material.

[0014] In step (A), the molar ratio of iron in ferric nitrate to aluminum in aluminum isopropoxide is 7-9:1-3; the ratio of ferric nitrate to anhydrous ethanol is 1:10-14, ferric nitrate is expressed in g and anhydrous ethanol in mL; the pH is 8.0-9.5; the constant temperature stirring temperature is 40-60℃ and the constant temperature stirring time is 2-4h.

[0015] In step (B), the ratio of kaolin to anhydrous ethanol is 1:10-15, with kaolin measured in g and anhydrous ethanol measured in mL; the volume ratio of suspension to Fe / Al sol is 3-5:1; the stirring time is 2-4 h; the standing time is 4-6 h; the drying temperature is 80-100℃; the drying time is 12-24 h; and the calcination temperature is 400-500℃; the calcination time is 3-5 h.

[0016] The method for preparing the defluoridating agent for industrial wastewater according to the present invention includes the following steps: (1) Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate and ferric ammonium sulfate were added to deionized water in sequence and stirred to prepare a base solution; (2) Add modified nano-magnesium oxide, modified biochar and Fe / Al modified kaolin material to the base solution in sequence, and stir until evenly dispersed; (3) Then add polyaluminum solution, modified attapulgite dispersion and hydroxyapatite nano dispersion in sequence, and stir continuously to obtain defluorinating agent for industrial wastewater.

[0017] The stirring time in step (1) is 30-60 min.

[0018] In steps (1) to (3), the stirring speed is 200-300 r / min and the stirring temperature is 20-30℃. The addition of each component is carried out under stirring.

[0019] The mechanism of action of this invention is as follows: 1. This invention selects components of different forms, such as modified attapulgite dispersion, Fe / Al modified kaolin material, modified biochar, and modified nano-magnesium oxide, which are spatially complementary and achieve spontaneous assembly through force gradient to build a stable flocculation framework. Then, multiple mechanisms are superimposed, such as rapid precipitation of polyaluminum solution and ferric ammonium sulfate, ion exchange of hydroxyapatite, surface complexation of modified nano-magnesium oxide and Fe / Al modified kaolin material, and electrostatic adsorption of modified attapulgite and modified biochar, to achieve comprehensive defluorination from physical interception to chemical fixation.

[0020] (1) Modified attapulgite is produced by organically modifying attapulgite using hexadecyltrimethylammonium bromide, changing its surface charge from negative to positive, and simultaneously increasing the number of surface hydroxyl groups through acidification, which allows it to react with F. - Hydrogen bonding is formed, further improving the fluoride removal rate. Modified attapulgite can interpenetrate with modified biochar and Fe / Al modified kaolinite materials, preventing interlayer stacking and forming a stable three-dimensional structure. This ensures the exposure of active sites while enhancing fluoride removal through electrostatic attraction and superposition effects. - The modified attapulgite can also form a hydrophobic interaction with the hydrophobic framework of chitosan quaternary ammonium salt. The positively charged groups of both can synergistically adsorb negatively charged fluorine-containing particles, resulting in a more compact floc structure. At the same time, it acts as a physical framework to support the formation of a three-dimensional network of flocs.

[0021] (2) Modified nano-magnesium oxide is achieved by loading rare earth ions onto the surface of nano-magnesium oxide through bridging with citric acid ligands, thereby changing the surface charge of magnesium oxide and simultaneously enhancing the hydrophilicity of the magnesium oxide surface, and thus improving its affinity for F. - This process forms a strong coordination chelation effect, with citric acid acting as a ligand. One end of citric acid complexes with rare earth ions, while the other end interacts with the MgO surface through hydrogen bonding or physical adsorption. The resulting organic-inorganic composite layer acts as a steric hindrance, solving the problem of nano-magnesium oxide particle agglomeration and maintaining a higher specific surface area and more active sites. Simultaneously, the hydration of modified nano-magnesium oxide creates a locally alkaline environment, promoting the formation of hydroxyl polymers with strong charge neutralization and bridging capabilities from polyaluminum salts. It also enhances the deprotonation of functional groups on the surface of modified biochar and other adsorbents, thereby improving their adsorption performance.

[0022] (3) Modified biochar has a rich specific surface area. By introducing nitrogen sites and further reconstructing the carbon matrix with nitrogen doping under an ammonia atmosphere, a nitrogen-doped carbon / graphene composite structure is formed, which can achieve the enrichment of specific adsorption sites, accelerate charge transfer, and improve the adsorption capacity of F. - The electrostatic adsorption effect of biochar. Due to its abundant porous structure, biochar can support modified nano-magnesium oxide and other microparticles, thus enhancing its electrostatic adsorption properties. 2 The carbon network forms a tight interfacial coupling with it, while the positive charge contained in the modified biochar forms a cluster of positively charged points with nano-magnesium oxide and Fe / Al modified kaolin materials. These points are attracted to each other by electrostatic attraction, forming a ternary composite adsorbent of biochar-magnesium oxide-kaolin materials, which effectively promotes the adsorption of F - The modified biochar provides an adhesion framework for colloids, enhances floc density, and strengthens the flocculation framework.

[0023] (4) Kaolin has natural interlayer gaps, but its structure is simple, its specific surface area is low, and its active sites are insufficient. Fe / Al modified kaolin materials are made by loading kaolin with iron and aluminum active metal ions without introducing other impurity metal ions. Iron ions dominate the highly selective fluorine capture, and aluminum ions form a cross-linking network through Al-O bonds, which prevents the agglomeration of the layered kaolin. At the same time, the hydroxyl groups of Al(OH)3 colloid supplement ion exchange sites, increasing coordination chelation sites while achieving stable loading. 3+ / Al 3+ It forms a multi-component cation network with other cations, enhancing its resistance to F. - The selectivity; Fe / Al modified kaolin materials interlock with modified attapulgite and modified biochar to avoid agglomeration, forming positive potential point clusters and charge transfer regions, and the specific surface area is synergistically amplified; Fe / Al active sites on Fe / Al modified kaolin materials interact with components such as polyaluminum solution, ferric ammonium sulfate and residual hydrolysis products in sewage to form a denser composite colloid.

[0024] (5) Polyaluminum sulfate solution and ferric ammonium sulfate are flocculants. Polyaluminum sulfate hydrolyzes to form Al(OH)3 amorphous colloid, which can adsorb fluorine-containing particles of different sizes and charges to build a basic flocculation skeleton. Ferric ammonium sulfate hydrolyzes to generate Fe(OH)3 colloid with high density and strong cohesion. The two form Fe-Al composite flocculation system, which improves both bridging ability and sedimentation speed. The formation of Fe-O-Al chemical bonds makes the colloidal skeleton more stable. At the same time, through electrostatic neutralization and bridging, it enhances the adsorption capacity of fluorine-containing particles.

[0025] (6) Hydroxyapatite nano-dispersion is the core component for deep purification of low-concentration fluorides. It has a large reaction surface area, and the hydroxyl groups in its crystal structure react with F. - An equal exchange occurs, and its adsorbed F - The resulting complex can combine with the flocculant colloids in the system through electrostatic attraction to form flocs that are easy to settle, thereby enhancing the speed of solid-liquid separation.

[0026] (7) Chitosan quaternary ammonium salt is a cationic organic polymer flocculant. It captures and connects destabilized particles through charge neutralization and bridging. Its positively charged groups are electrostatically crosslinked with the flocculant colloid, and the long-chain molecules wrap around the colloidal skeleton to form a three-dimensional network skeleton, which enhances the mechanical strength of the flocs. Its hydrophobic skeleton forms van der Waals forces with the hydrophobic long chains on the surface of the modified attapulgite. At the same time, the positively charged groups synergistically adsorb negatively charged fluorine-containing particles, making the internal binding of the flocs tighter.

[0027] (8) Sodium carboxymethyl cellulose provides a uniform and stable dispersion environment for all components through electrostatic, hydration membrane, and thickening effects, avoiding clogged active sites caused by agglomeration. Sodium carboxymethyl cellulose can adjust the viscosity of the system, prevent rapid sedimentation of the adsorbent, and ensure uniform mixing of the defluorinating agent and wastewater; its molecular chain has -COO - Hydrogen bonds are formed with the hydroxyl groups on the surface of nanoparticles, preventing particle aggregation through electrostatic repulsion and steric hindrance. The sodium carboxymethyl cellulose hydration film prevents interlayer stacking of kaolinite materials and aggregation of attapulgite, maintaining unobstructed micropore-mesopore channels and ensuring full exposure of active sites. The sodium carboxymethyl cellulose molecular chain acts as an auxiliary framework, enhancing floc continuity through bridging.

[0028] (9) Potassium sodium tartrate forms water-soluble complexes with metal ions in the system, preventing premature hydrolysis and precipitation, ensuring that the active ingredients can fully diffuse to all parts of the water body and efficiently capture F. - At the same time, it stabilizes the pH environment of the system, maintains the stability of the system and the effective active components, and ensures deep defluorination.

[0029] 2. This invention determines the feeding sequence by exploring the process of defluorinating agents. Through the logic of "first building a stable substrate → then introducing active components → finally strengthening dispersion and synergy", it solves the problems of component failure and uneven dispersion caused by disordered mixing, improves storage stability, ensures the synergistic efficiency of each component, and stably meets the standards for deep defluorination of industrial wastewater.

[0030] (1) First, sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate and ferric ammonium sulfate were added sequentially to deionized water to construct a dispersion-stabilized substrate: The addition of sodium carboxymethyl cellulose increases the viscosity of the aqueous phase and, through the hydration film effect and steric hindrance effect, constructs a dispersion system. The addition of chitosan quaternary ammonium salt allows it to fully dissolve in the neutral dispersion system, with its molecular chains freely extending. When it is subsequently used in conjunction with flocculants, it can exert optimal electrostatic crosslinking and hydrogen bonding effects. Potassium sodium tartrate acts as a complexing stabilizer and pH buffer, chelating interfering ions in advance and stabilizing the system environment. The addition of ferric ammonium sulfate as a flocculant ensures uniform dispersion to form a stable system. When it is subsequently used in conjunction with polyaluminum, it can form a uniform Fe-Al composite colloid, enhancing the flocculation effect.

[0031] (2) Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin material are then added sequentially to introduce active components: Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin were sequentially added to the constructed stable dispersion system. Within the buffer network formed by sodium carboxymethyl cellulose and chitosan quaternary ammonium salt, and under the protection of potassium sodium tartrate, each active component was slowly and uniformly dispersed, and the active sites were fully exposed, forming a homogeneous and stable suspension. This avoided mutual adsorption and aggregation between different adsorbents due to charge differences.

[0032] (3) Finally, polyaluminum chloride solution, modified attapulgite dispersion and hydroxyapatite nano dispersion are added in sequence to achieve flocculation and deep defluorination: After the polyaluminum chloride solution is added, potassium sodium tartrate will immediately complex some of the Al. 3+ The hydrolysis rate is controlled, and some polyaluminum hydrolyzes to form Al(OH)3 colloids, which are uniformly dispersed in the system, forming multiple highly active defluorination reaction sites. After the addition of modified attapulgite dispersion, the modified attapulgite acts as a flocculation skeleton, working with the colloids to construct a three-dimensional network of flocs, increasing floc density and settling velocity. Finally, hydroxyapatite nano-dispersion is added to prevent it from being encapsulated and buried by the formed floc network and precipitates, ensuring its uniform dispersion in a stable flocculation system, where it can exert its ion exchange function and capture residual low concentrations of fluoride. - At the same time, it can be adsorbed on the already formed flocculent skeleton, which ensures deep defluorination activity and avoids the loss of nanoparticles.

[0033] The beneficial effects of this invention are as follows: (1) The components selected in this invention have synergistic effects, covering multiple defluorination mechanisms such as complexation adsorption, coagulation precipitation, and ion exchange, which can efficiently remove fluoride. Through the adsorption, coagulation, ion exchange, and complexation effects of each component, fluoride in industrial wastewater can be removed quickly and deeply. Experimental data show that for industrial wastewater with a fluoride concentration higher than 20 mg / L, the fluoride concentration can be stably reduced to below 1 mg / L after treatment with the defluorinating agent of this invention, which is far below the national emission standard.

[0034] (2) By rationally selecting raw materials and optimizing the preparation process, this invention effectively prevents precipitation and stratification of the defluorinating agent, improves its chemical stability and storage stability, and the resulting defluorinating agent has excellent chemical and storage stability. Tests show that after 12 months of storage at room temperature or 3 months of storage at high temperature (40℃) and low temperature (5℃), the defluorinating agent maintains stable defluorination performance without precipitation or stratification, ensuring reliable and stable performance in practical applications and transportation, and adapting to different storage and usage environments.

[0035] (3) The defluorinating agent of the present invention is in liquid form, which is convenient to use and can be quickly mixed with industrial wastewater, thereby improving treatment efficiency and reducing operation difficulty and labor intensity. In actual industrial wastewater treatment, the dosage of the defluorinating agent can be precisely controlled according to the flow rate and fluoride concentration of the industrial wastewater, so as to achieve automated and efficient treatment.

[0036] (4) The raw materials selected in this invention are mostly natural or biodegradable substances, which will not generate secondary pollution during preparation and use, and meet environmental protection requirements. At the same time, the defluorinating agent of this invention can effectively reduce the harm of fluorides in industrial wastewater to the environment, protect the surrounding ecological environment, and is environmentally friendly. Detailed Implementation

[0037] The present invention will be further described below with reference to embodiments.

[0038] Example 1 The industrial wastewater defluoridator is made from the following raw materials in parts by weight: 3 parts sodium carboxymethyl cellulose, 20 parts modified attapulgite dispersion, 30 parts polyaluminum solution, 10 parts hydroxyapatite nano dispersion, 1 part chitosan quaternary ammonium salt, 0.5 parts ferric ammonium sulfate, 1 part potassium sodium tartrate, 2 parts modified nano magnesium oxide, 2 parts modified biochar, 2 parts Fe / Al modified kaolin material, and 70 parts deionized water.

[0039] The preparation method of modified attapulgite dispersion is as follows: 1000g of attapulgite was pulverized to 300 mesh and placed in 4000mL of 12% sulfuric acid solution. It was soaked at 60℃ for 5h, then washed with deionized water until neutral and dried to obtain acidified attapulgite. 1000g of acidified attapulgite was mixed with 4000g of 8% hexadecyltrimethylammonium bromide solution and stirred at 60℃ for 2h. After the reaction was completed, it was filtered to obtain modified attapulgite. Deionized water was added to the modified attapulgite and it was dispersed at 5000r / min for 60min to obtain a modified attapulgite dispersion with a solid content of 20%.

[0040] The preparation method of hydroxyapatite nano-dispersion is as follows: 1000g of calcium chloride and diammonium hydrogen phosphate were dissolved in 50L of deionized water at a molar ratio of 5:3. Under stirring, ammonia was slowly added to adjust the pH to 10. The mixture was then subjected to a hydrothermal reaction at 150℃ for 24h. After the reaction was completed, the mixture was cooled, centrifuged, and washed to obtain nano-hydroxyapatite. Deionized water was added to 1000g of nano-hydroxyapatite, followed by 10g of sodium hexametaphosphate. The mixture was ultrasonically dispersed at 40kHz for 80min to obtain a nano-dispersion of hydroxyapatite with a solid content of 10%.

[0041] The preparation method of modified nano-magnesium oxide is as follows: 1000g of lanthanum nitrate and citric acid were dissolved in 100kg of deionized water at a molar ratio of 1:2 to obtain a rare earth complex solution. 1000g of nano-magnesium oxide was added to anhydrous ethanol and ultrasonically dispersed at 300W for 30min to obtain a nano-magnesium oxide suspension with a concentration of 5g / L. Then, 1.5L of the rare earth complex solution was added dropwise to 20L of the nano-magnesium oxide suspension, and the mixture was stirred at 70℃ and 200rpm for 2h. After centrifugation at 3000rpm for 15min, the mixture was washed, dried at 100℃ for 3h, and ground into powder to obtain modified nano-magnesium oxide.

[0042] The preparation method of modified biochar is as follows: 1000g of granular biochar was added to 10L of 20wt.% nitric acid solution and soaked at 15℃ for 12h to obtain activated biochar. Then, 1000g of activated biochar was added to 4000g of 15g / L pyrrole solution and impregnated at 10℃ for 20h. 25L of 15g / L FeCl3 solution was added dropwise and polymerization was carried out at 10℃ for 20h. Then, it was treated at 850℃ for 2h under an ammonia atmosphere, washed sequentially with dilute hydrochloric acid and distilled water, and dried at 105℃ for 12h to obtain modified biochar.

[0043] The preparation method of Fe / Al modified kaolin material is as follows: According to the molar ratio of iron in ferric nitrate to aluminum in aluminum isopropoxide of 8:2, 1000g of ferric nitrate and aluminum isopropoxide were dissolved in 12L of anhydrous ethanol, and ammonia was added dropwise to adjust the pH to 8.0. The mixture was stirred at 60℃ for 2h to obtain Fe / Al sol. 1000g of kaolin was added to 15L of anhydrous ethanol and ultrasonically dispersed to obtain a suspension. 5L of the suspension was added to 1L of Fe / Al sol, stirred for 2h, allowed to stand for 6h, dried at 90℃ for 18h, calcined at 500℃ for 3h, and ground into powder to obtain Fe / Al modified kaolin material.

[0044] A method for preparing a fluoride removal agent for industrial wastewater includes the following steps: Deionized water was added to the reactor, and stirring was started at 200 r / min and 30℃. Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate, and ferric ammonium sulfate were added sequentially and stirred for 30 min to obtain a base solution. Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin material were then added sequentially to the base solution and stirred until uniformly dispersed. A 10% (w / w) polyaluminum solution was then added and stirred for 10 min. Modified attapulgite dispersion was then added and stirred for 10 min. Finally, hydroxyapatite nano-dispersion was added and stirred for another 40 min to obtain a fluoride removal agent for industrial wastewater.

[0045] Example 2 The industrial wastewater defluoridator is made from the following raw materials in parts by weight: 5 parts sodium carboxymethyl cellulose, 25 parts modified attapulgite dispersion, 35 parts polyaluminum solution, 12 parts hydroxyapatite nano dispersion, 2 parts chitosan quaternary ammonium salt, 1.2 parts ferric ammonium sulfate, 2 parts potassium sodium tartrate, 1 part modified nano magnesium oxide, 3 parts modified biochar, 1 part Fe / Al modified kaolin material, and 80 parts deionized water.

[0046] The preparation method of modified attapulgite dispersion is as follows: 1000g of attapulgite was pulverized to 400 mesh and placed in 6000mL of 10% sulfuric acid solution. It was soaked at 70℃ for 4h, then washed with deionized water until neutral and dried to obtain acidified attapulgite. 1000g of acidified attapulgite was mixed with 5000g of 5% hexadecyltrimethylammonium bromide solution and stirred at 40℃ for 4h. After the reaction was completed, it was filtered to obtain modified attapulgite. Deionized water was added to the modified attapulgite and it was dispersed at 6000r / min for 50min to obtain a modified attapulgite dispersion with a solid content of 25%.

[0047] The preparation method of hydroxyapatite nano-dispersion is as follows: 1000g of calcium chloride and diammonium hydrogen phosphate were dissolved in 60L of deionized water, with a molar ratio of calcium chloride to diammonium hydrogen phosphate of 5:3.5. Under stirring, ammonia water was slowly added to adjust the pH to 10.5. Then, a hydrothermal reaction was carried out at 160℃ for 18h. After the reaction was completed, the mixture was cooled, centrifuged, and washed to obtain nano-hydroxyapatite. Deionized water was added to 1000g of nano-hydroxyapatite, and then 5g of sodium hexametaphosphate was added. The mixture was ultrasonically dispersed at a frequency of 50kHz for 60min to obtain a nano-dispersion of hydroxyapatite with a solid content of 12%.

[0048] The preparation method of modified nano-magnesium oxide is as follows: 1000g of lanthanum nitrate and citric acid were dissolved in 50kg of deionized water at a molar ratio of 1:3 to obtain a rare earth complex solution. 1000g of nano-magnesium oxide was added to anhydrous ethanol and ultrasonically dispersed at 400W for 25min to obtain a nano-magnesium oxide suspension with a concentration of 5g / L. Then, 2L of the rare earth complex solution was added dropwise to 20L of the nano-magnesium oxide suspension, and the mixture was stirred at 60℃ and 300rpm for 1h. After centrifugation at 4000rpm for 12min, the mixture was washed, dried at 120℃ for 2h, and ground into powder to obtain modified nano-magnesium oxide.

[0049] The preparation method of modified biochar is as follows: 1000g of granular biochar was added to 15L of 15wt.% nitric acid solution and soaked at 20℃ for 10h to obtain activated biochar. Then, 1000g of activated biochar was added to 3000g of 10g / L pyrrole solution and impregnated at 20℃ for 15h. Then, 20L of 15g / L FeCl3 solution was added dropwise and polymerization was carried out at 10℃ for 22h. Then, it was treated at 800℃ for 3h under an ammonia atmosphere, washed with dilute hydrochloric acid and distilled water in sequence, and dried at 110℃ for 10h to obtain modified biochar.

[0050] The preparation method of Fe / Al modified kaolin material is as follows: According to the molar ratio of iron in ferric nitrate to aluminum in aluminum isopropoxide of 7:3, 1000g of ferric nitrate and aluminum isopropoxide were dissolved in 10L of anhydrous ethanol, and ammonia was added dropwise to adjust the pH to 9.0. The mixture was stirred at 50℃ for 3h to obtain Fe / Al sol. 1000g of kaolin was added to 10L of anhydrous ethanol to obtain a suspension. 3L of the suspension was then added to 1L of Fe / Al sol. The mixture was stirred for 2h, allowed to stand for 5h, dried at 95℃ for 18h, calcined at 450℃ for 4h, and ground into powder to obtain Fe / Al modified kaolin material.

[0051] A method for preparing a fluoride removal agent for industrial wastewater includes the following steps: Deionized water was added to the reactor, and stirring was started at 250 r / min and 25℃. Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate, and ferric ammonium sulfate were added sequentially and stirred for 45 min to obtain a base solution. Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin material were then added sequentially to the base solution and stirred until uniformly dispersed. A 10% (w / w) polyaluminum solution was then added and stirred for 12 min. Modified attapulgite dispersion was then added and stirred for 12 min. Finally, hydroxyapatite nano-dispersion was added and stirred for another 60 min to obtain a fluoride removal agent for industrial wastewater.

[0052] Example 3 The industrial wastewater defluoridator is made from the following raw materials in parts by weight: 7 parts sodium carboxymethyl cellulose, 25 parts modified attapulgite dispersion, 35 parts polyaluminum solution, 15 parts hydroxyapatite nano dispersion, 3 parts chitosan quaternary ammonium salt, 2 parts ferric ammonium sulfate, 3 parts potassium sodium tartrate, 3 parts modified nano magnesium oxide, 4 parts modified biochar, 3 parts Fe / Al modified kaolin material, and 90 parts deionized water.

[0053] The preparation method of modified attapulgite dispersion is as follows: 1000g of attapulgite was pulverized to 500 mesh and placed in 8000mL of 8% sulfuric acid solution. It was soaked at 80℃ for 3h, then washed with deionized water until neutral and dried to obtain acidified attapulgite. 1000g of acidified attapulgite was mixed with 3000g of 10% hexadecyltrimethylammonium bromide solution and stirred at 50℃ for 3h. After the reaction was completed, it was filtered to obtain modified attapulgite. Deionized water was added to the modified attapulgite and it was dispersed at 6500r / min for 40min to obtain a modified attapulgite dispersion with a solid content of 30%.

[0054] The preparation method of hydroxyapatite nano-dispersion is as follows: 1000g of calcium chloride and diammonium hydrogen phosphate were dissolved in 40L of deionized water at a molar ratio of 5:3. Under stirring, ammonia was slowly added to adjust the pH to 11. The hydrothermal reaction was carried out at 180℃ for 12h. After the reaction was completed, the mixture was cooled, centrifuged, and washed to obtain nano-hydroxyapatite. Deionized water was added to 1000g of nano-hydroxyapatite, followed by 10g of sodium hexametaphosphate. The mixture was ultrasonically dispersed at 60kHz for 40min to obtain a nano-dispersion of hydroxyapatite with a solid content of 15%.

[0055] The preparation method of modified nano-magnesium oxide is as follows: 1000g of lanthanum nitrate and citric acid were dissolved in 75kg of deionized water at a molar ratio of 1:3 to obtain a rare earth complex solution. 1000g of nano-magnesium oxide was added to anhydrous ethanol and ultrasonically dispersed at 500W for 20min to obtain a nano-magnesium oxide suspension with a concentration of 7g / L. Then, 1.4L of the rare earth complex solution was added dropwise to 20L of the nano-magnesium oxide suspension, and the mixture was stirred at 55℃ and 250rpm for 1.5h. After centrifugation at 5000rpm for 10min, the mixture was washed, dried at 100℃ for 3h, and ground into powder to obtain modified nano-magnesium oxide.

[0056] The preparation method of modified biochar is as follows: 1000g of granular biochar was added to 10L of 20wt.% nitric acid solution and soaked at 18℃ for 11h to obtain activated biochar. Then, 1000g of activated biochar was added to 4000g of 10g / L pyrrole solution and impregnated at 15℃ for 20h. Then, 20L of 15g / L FeCl3 solution was added dropwise and polymerized at 12℃ for 20h. Then, it was treated at 900℃ for 2h under an ammonia atmosphere, washed sequentially with dilute hydrochloric acid and distilled water, and dried at 105℃ for 11h to obtain modified biochar.

[0057] The preparation method of Fe / Al modified kaolin material is as follows: According to the molar ratio of iron in ferric nitrate to aluminum in aluminum isopropoxide of 7:3, 1000g of ferric nitrate and aluminum isopropoxide were dissolved in 14L of anhydrous ethanol, and ammonia was added dropwise to adjust the pH to 9.5. The mixture was stirred at 60℃ for 4h to obtain Fe / Al sol. 1000g of kaolin was added to 15L of anhydrous ethanol and ultrasonically dispersed to obtain a suspension. 6L of the suspension was added to 2L of Fe / Al sol, stirred for 3h, allowed to stand for 4h, dried at 80℃ for 24h, calcined at 400℃ for 5h, and ground into powder to obtain Fe / Al modified kaolin material.

[0058] A method for preparing a fluoride removal agent for industrial wastewater includes the following steps: Deionized water was added to the reactor, and stirring was started at 300 r / min and 20℃. Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate, and ferric ammonium sulfate were added sequentially and stirred for 60 min to obtain a base solution. Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin material were then added sequentially to the base solution and stirred until uniformly dispersed. A 12% (w / w) polyaluminum solution was then added and stirred for 15 min. Modified attapulgite dispersion was then added and stirred for 15 min. Finally, hydroxyapatite nano-dispersion was added and stirred for another 80 min to obtain a fluoride removal agent for industrial wastewater.

[0059] Example 4 The industrial wastewater defluoridator is made from the following raw materials in parts by weight: 4 parts sodium carboxymethyl cellulose, 22 parts modified attapulgite dispersion, 32 parts polyaluminum solution, 11 parts hydroxyapatite nano dispersion, 1.5 parts chitosan quaternary ammonium salt, 1 part ferric ammonium sulfate, 1.5 parts potassium sodium tartrate, 2 parts modified nano magnesium oxide, 2.5 parts modified biochar, 2 parts Fe / Al modified kaolin material, and 75 parts deionized water.

[0060] The preparation method of modified attapulgite dispersion is as follows: 1000g of attapulgite was crushed to 300 mesh and placed in 6000mL of 9% sulfuric acid solution. It was soaked at 65℃ for 4.5h, then washed with deionized water until neutral, and dried to obtain acidified attapulgite. 1000g of acidified attapulgite was mixed with 3000g of 10% hexadecyltrimethylammonium bromide solution and stirred at 45℃ for 3h. After the reaction was completed, it was filtered to obtain modified attapulgite. Deionized water was added to the modified attapulgite and it was dispersed at 7000r / min for 35min to obtain a modified attapulgite dispersion with a solid content of 22%.

[0061] The preparation method of hydroxyapatite nano-dispersion is as follows: 1000g of calcium chloride and diammonium hydrogen phosphate were dissolved in 60L of deionized water, with a molar ratio of 5:2.5. Under stirring, ammonia was slowly added to adjust the pH to 10. The hydrothermal reaction was carried out at 170℃ for 14h. After the reaction was completed, the mixture was cooled, centrifuged, and washed to obtain nano-hydroxyapatite. Deionized water was added to 1000g of nano-hydroxyapatite, followed by 6g of sodium hexametaphosphate. The mixture was ultrasonically dispersed at 50kHz for 50min to obtain a nano-dispersion of hydroxyapatite with a solid content of 14%.

[0062] The preparation method of modified nano-magnesium oxide is as follows: 1000g of lanthanum nitrate and citric acid were dissolved in 80kg of deionized water, with a molar ratio of lanthanum nitrate to citric acid of 1:2.5, to obtain a rare earth complex solution. 1000g of nano-magnesium oxide was added to anhydrous ethanol and ultrasonically dispersed at 400W for 25min to obtain a nano-magnesium oxide suspension with a concentration of 10g / L. Then, 2L of the rare earth complex solution was added dropwise to 20L of the nano-magnesium oxide suspension, and the mixture was stirred at 50℃ and 300rpm for 1h, then centrifuged at 4000rpm for 12min, washed, dried at 80℃ for 4h, and ground into powder to obtain modified nano-magnesium oxide.

[0063] The preparation method of modified biochar is as follows: 1000g of granular biochar was added to 15L of 15wt.% nitric acid solution and soaked at 15℃ for 12h to obtain activated biochar. Then, 1000g of activated biochar was added to 5000g of 20g / L pyrrole solution and impregnated at 10℃ for 20h. Then, 30L of 14g / L FeCl3 solution was added dropwise and polymerization was carried out at 11℃ for 21h. Then, it was treated at 850℃ for 2h under an ammonia atmosphere, washed with dilute hydrochloric acid and distilled water in sequence, and dried at 100℃ for 12h to obtain modified biochar.

[0064] The preparation method of Fe / Al modified kaolin material is as follows: According to the molar ratio of iron in ferric nitrate to aluminum in aluminum isopropoxide of 9:1, 1000g of ferric nitrate and aluminum isopropoxide were dissolved in 10L of anhydrous ethanol, and ammonia was added dropwise to adjust the pH to 8.0. The mixture was stirred at 40℃ for 4h to obtain Fe / Al sol. 1000g of kaolin was added to 12L of anhydrous ethanol and ultrasonically dispersed to obtain a suspension. 4L of the suspension was then added to 1L of Fe / Al sol, stirred for 2h, allowed to stand for 6h, dried at 85℃ for 18h, calcined at 500℃ for 3h, and ground into powder to obtain Fe / Al modified kaolin material.

[0065] A method for preparing a fluoride removal agent for industrial wastewater includes the following steps: Deionized water was added to the reactor, and stirring was started at 220 r / min and 20℃. Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate, and ferric ammonium sulfate were added sequentially and stirred for 35 min to obtain a base solution. Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin material were then added sequentially to the base solution and stirred until uniformly dispersed. A 10% (w / w) polyaluminum solution was then added and stirred for 11 min. Modified attapulgite dispersion was then added and stirred for 11 min. Finally, hydroxyapatite nano-dispersion was added and stirred for another 50 min to obtain a fluoride removal agent for industrial wastewater.

[0066] Example 5 The industrial wastewater defluoridator is made from the following raw materials in parts by weight: 6 parts sodium carboxymethyl cellulose, 24 parts modified attapulgite dispersion, 34 parts polyaluminum solution, 14 parts hydroxyapatite nano dispersion, 2.5 parts chitosan quaternary ammonium salt, 1.8 parts ferric ammonium sulfate, 2.5 parts potassium sodium tartrate, 2.5 parts modified nano magnesium oxide, 3 parts modified biochar, 2.5 parts Fe / Al modified kaolin material, and 85 parts deionized water.

[0067] The preparation method of modified attapulgite dispersion is as follows: 1000g of attapulgite was pulverized to 400 mesh and placed in 5000mL of 10% sulfuric acid solution. It was soaked at 75℃ for 3.5h, then washed with deionized water until neutral, and dried to obtain acidified attapulgite. 1000g of acidified attapulgite was mixed with 4000g of 9% hexadecyltrimethylammonium bromide solution and stirred at 60℃ for 2.5h. After the reaction was completed, it was filtered to obtain modified attapulgite. Deionized water was added to the modified attapulgite, and it was dispersed at 8000r / min for 30min to obtain a modified attapulgite dispersion with a solid content of 28%.

[0068] The preparation method of hydroxyapatite nano-dispersion is as follows: 1000g of calcium chloride and diammonium hydrogen phosphate were dissolved in 50L of deionized water at a molar ratio of 5:3. Under stirring, ammonia was slowly added to adjust the pH to 11. The hydrothermal reaction was carried out at 160℃ for 20h. After the reaction was completed, the mixture was cooled, centrifuged, and washed to obtain nano-hydroxyapatite. Deionized water was added to 1000g of nano-hydroxyapatite, followed by 5g of sodium hexametaphosphate. The mixture was ultrasonically dispersed at 60kHz for 45min to obtain a nano-dispersion of hydroxyapatite with a solid content of 11%.

[0069] The preparation method of modified nano-magnesium oxide is as follows: 1000g of cerium sulfate and citric acid were dissolved in 80kg of deionized water at a molar ratio of 1:2 to obtain a rare earth complex solution. 1000g of nano-magnesium oxide was added to anhydrous ethanol and ultrasonically dispersed at 400W for 30min to obtain a nano-magnesium oxide suspension with a concentration of 8g / L. Then, 2.4L of the rare earth complex solution was added dropwise to 20L of the nano-magnesium oxide suspension, and the mixture was stirred at 60℃ and 300rpm for 1.5h. After centrifugation at 5000rpm for 12min, the mixture was washed, dried at 100℃ for 3h, and ground into powder to obtain modified nano-magnesium oxide.

[0070] The preparation method of modified biochar is as follows: 1000g of granular biochar was added to 12L of 18wt.% nitric acid solution and soaked at 18℃ for 12h to obtain activated biochar. Then, 1000g of activated biochar was added to 4000g of 5g / L pyrrole solution and impregnated at 15℃ for 17h. Then, 20L of 16g / L FeCl3 solution was added dropwise and polymerized at 10℃ for 20h. Then, it was treated at 800℃ for 2.5h under an ammonia atmosphere, washed successively with dilute hydrochloric acid and distilled water, and dried at 105℃ for 12h to obtain modified biochar.

[0071] The preparation method of Fe / Al modified kaolin material is as follows: According to the molar ratio of iron in ferric nitrate to aluminum in aluminum isopropoxide of 7:3, 1000g of ferric nitrate and aluminum isopropoxide were dissolved in 12L of anhydrous ethanol, and ammonia was added dropwise to adjust the pH to 9.0. The mixture was stirred at 50℃ for 3h to obtain Fe / Al sol. 1000g of kaolin was added to 12L of anhydrous ethanol and ultrasonically dispersed to obtain a suspension. 5L of the suspension was added to 1L of Fe / Al sol, stirred for 4h, allowed to stand for 5h, dried at 100℃ for 12h, calcined at 450℃ for 4h, and ground into powder to obtain Fe / Al modified kaolin material.

[0072] A method for preparing a fluoride removal agent for industrial wastewater includes the following steps: Deionized water was added to the reactor, and stirring was started at 280 r / min and 25℃. Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate, and ferric ammonium sulfate were added sequentially and stirred for 55 min to obtain a base solution. Modified nano-magnesium oxide, modified biochar, and Fe / Al modified kaolin material were then added sequentially to the base solution and stirred until uniformly dispersed. Then, an 8% (w / w) polyaluminum solution was added and stirred for 13 min. Next, modified attapulgite dispersion was added and stirred for 13 min. Finally, hydroxyapatite nano-dispersion was added and stirred for another 70 min to obtain a fluoride removal agent for industrial wastewater.

[0073] Comparative Example 1 The preparation method is the same as in Example 5, except that no modified attapulgite dispersion is added.

[0074] Comparative Example 2 The preparation method is the same as in Example 5, except that the modified attapulgite dispersion is replaced with attapulgite dispersion. The preparation method of attapulgite dispersion is to crush attapulgite to 400 mesh, add deionized water, and disperse at high speed at 8000 r / min for 30 min to obtain attapulgite dispersion with a solid content of 28%.

[0075] Comparative Example 3 The preparation method is the same as in Example 5, except that hydroxyapatite nanodispersion is not added.

[0076] Comparative Example 4 The preparation method is the same as in Example 5, except that no modified nano-magnesium oxide is added.

[0077] Comparative Example 5 The preparation method is the same as in Example 5, except that the modified nano-magnesium oxide is replaced with nano-magnesium oxide.

[0078] Comparative Example 6 The preparation method is the same as in Example 5, except that no modified biochar is added.

[0079] Comparative Example 7 The preparation method is the same as in Example 5, except that the modified biochar is replaced with biochar.

[0080] Comparative Example 8 The preparation method is the same as in Example 5, except that Fe / Al is not added to modify the kaolin material.

[0081] Comparative Example 9 The preparation method is the same as in Example 5, except that the Fe / Al modified kaolin material is replaced with kaolin.

[0082] Comparative Example 10 The preparation method is the same as in Example 5, except that potassium sodium tartrate is not added.

[0083] Comparative Example 11 The preparation method is the same as in Example 5, except that ferric ammonium sulfate is not added.

[0084] Comparative Example 12 The preparation method is the same as in Example 5, except that sodium carboxymethyl cellulose is not added.

[0085] Comparative Example 13 The preparation method is the same as in Example 5, except that chitosan quaternary ammonium salt is not added.

[0086] Comparative Example 14 The raw materials for the defluorinating agent used in industrial wastewater are the same as in Example 5.

[0087] A method for preparing a fluoride removal agent for industrial wastewater includes the following steps: Deionized water was added to the reactor, and stirring was started at a speed of 280 r / min and a temperature of 25℃. Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate, ferric ammonium sulfate, modified nano magnesium oxide, modified biochar, Fe / Al modified kaolin material, 8% polyaluminum solution, modified attapulgite dispersion, and hydroxyapatite nano dispersion were added and stirred for 151 min to obtain a fluoride removal agent for industrial wastewater.

[0088] Product performance tests are as follows: 1. Defluorination effect test of defluorinating agent Take 1000 mL of industrial wastewater with different fluoride concentrations, add the defluorinating agent prepared in Example 1, and then add 3 mL of 1‰ polyacrylamide. Stir for 10 min, let stand for 1 h to settle, and then detect the concentration of fluoride in the supernatant. The detection results are shown in Table 1.

[0089] Table 1. Defluorination effect of the defluorinating agent prepared in Example 1

[0090] As shown in Table 1, the defluorinating agent prepared in Example 1 can effectively reduce the fluoride concentration in industrial wastewater to below 1 mg / L, which is far below the concentration specified by the national emission standards. This indicates that the defluorinating agent prepared in this invention can effectively remove fluoride from industrial wastewater and significantly reduce the fluoride concentration.

[0091] 2. Stability test of defluorinating agent The defluorinating agents prepared in Examples 1-5 were stored at room temperature (25°C) for 12 months, at high temperature (40°C) for 3 months, and at low temperature (5°C) for 3 months, respectively. 1000 mL of industrial wastewater containing the same fluoride was taken from each case, and equal amounts of the defluorinating agent before and after storage were added for treatment (3 mL of 1‰ polyacrylamide was added during treatment). The removal rate of fluoride by the defluorinating agent before and after storage was measured, and the defluorination retention rate was calculated.

[0092] Fluoride removal retention rate = Fluoride removal rate after storage / Fluoride removal rate before storage × 100%.

[0093] The measurement results are shown in Table 2.

[0094] Table 2. Defluorination retention rate of the defluorinating agents prepared in Examples 1-5

[0095] As shown in Table 2, the defluorination agent prepared in this invention maintains a defluorination retention rate of over 95.1% after 12 months of storage at room temperature; over 91.8% after 3 months of storage at high temperature (40℃); and over 95.0% after 3 months of storage at low temperature (5℃). Furthermore, observation revealed that the defluorination agent of this invention did not exhibit precipitation or stratification after long-term storage. This demonstrates that the defluorination agent of this invention possesses excellent storage stability.

[0096] 3. Comparison of defluorination effect and stability of the defluorinating agents prepared in Example 5 and Comparative Examples 1-14 Defluoridation effect test: Take 1000 mL of the same fluoride-containing industrial wastewater, add the defluoridating agent prepared in Example 5 and Comparative Examples 1-14 respectively, and then add 3 mL of 1‰ polyacrylamide. After stirring for 10 min, let it stand for 1 h to settle, and then detect the concentration of fluoride in the supernatant.

[0097] Stability test: The defluorinating agents prepared in Example 5 and Comparative Examples 1-14 were stored at room temperature (25°C) for 12 months, at high temperature (40°C) for 3 months, and at low temperature (5°C) for 3 months, respectively. 1000 mL of industrial wastewater containing the same fluoride was taken from each case, and equal amounts of the defluorinating agent before and after storage were added for treatment (3 mL of 1‰ polyacrylamide was added during treatment). The removal rate of fluoride by the defluorinating agent before and after storage was determined, and the defluorination retention rate was calculated.

[0098] The measurement results are shown in Table 3.

[0099] Table 3. Defluorination effect and stability results of the defluorination agents prepared in Example 5 and Comparative Examples 1-14

[0100] Table 3 shows that, compared with Example 5, the defluorination effects of the defluorinating agents prepared in Comparative Examples 1-13 were significantly reduced, indicating that the addition of modified attapulgite dispersion, hydroxyapatite nano-dispersion, modified nano-magnesium oxide, modified biochar, Fe / Al modified kaolin material, potassium sodium tartrate, and ferric ammonium sulfate can effectively improve the defluorination effect. Meanwhile, the stability of the defluorinating agents prepared in Comparative Examples 1-13 also decreased to varying degrees, indicating that the components of this invention synergistically construct the high stability of the defluorinating agent. Adding unmodified attapulgite dispersion, nano-magnesium oxide, biochar, and kaolin to Comparative Examples 2, 5, 7, and 9, respectively, not only reduced the defluorination effect of the defluorinating agent but also decreased the stability of the system, making it prone to aggregation and sedimentation during storage. The results of Comparative Examples 1 and 13 show that the absence of either modified attapulgite dispersion or chitosan quaternary ammonium salt prevents the synergistic adsorption of negatively charged fluoride particles, resulting in a reduced ability to treat fluorides. In Comparative Example 4, the absence of modified nano-magnesium oxide, in Comparative Example 6, the absence of modified biochar, and in Comparative Example 8, the absence of Fe / Al modified kaolin material all failed to form a ternary composite adsorbent of biochar-magnesium oxide-kaolin material, resulting in a reduced adsorption capacity for F⁻. In Comparative Example 10, the absence of potassium sodium tartrate, and in Comparative Example 12, the absence of sodium carboxymethyl cellulose, both led to a decrease in the stability of the defluorinating agent and a significant reduction in its defluorination performance. This indicates that the addition of potassium sodium tartrate and sodium carboxymethyl cellulose in this invention can significantly improve the stability of the defluorinating agent, ensure stable defluorination efficiency, and extend the product's shelf life. In Comparative Example 14, the defluorinating agent was not prepared according to the feeding sequence of this invention, resulting in a significant reduction in both its defluorination effect and stability. This demonstrates that this invention, by adjusting the defluorinating agent process and exploring the feeding sequence, solves the problems of component failure and uneven dispersion caused by disordered mixing through the logic of "first building a stable substrate, then introducing active components, and finally strengthening dispersion synergy," significantly improving the stability of the defluorinating agent and fully utilizing its defluorination efficiency.

[0101] 4. Comparison of defluorination effect and stability between Example 5 and commercially available defluorinators Defluoridation effect test: Take 1000 mL of the same fluoride-containing industrial wastewater, add equal amounts of the defluoridating agent prepared in Example 5, commercial liquid defluoridating agent 1 and commercial liquid defluoridating agent 2, and then add 3 mL of 1‰ polyacrylamide. After stirring for 10 min, let it stand for 1 h to settle, and then detect the concentration of fluoride in the supernatant.

[0102] Stability test: The defluorinating agent prepared in Example 5, commercial liquid defluorinating agent 1, and commercial liquid defluorinating agent 2 were stored at room temperature (25°C) for 12 months, at high temperature (40°C) for 3 months, and at low temperature (5°C) for 3 months, respectively. 1000 mL of industrial wastewater containing the same fluoride was taken from each of them and equal amounts of the defluorinating agent before and after storage were added for treatment (3 mL of 1‰ polyacrylamide was added during treatment). The removal rate of fluoride by the defluorinating agent before and after storage was measured, and the defluorination retention rate was calculated.

[0103] The measurement results are shown in Table 4.

[0104] Table 4. Defluorination effect and stability results of the defluorination agent prepared in Example 5, commercially available liquid defluorination agent 1, and commercially available liquid defluorination agent 2.

[0105] As shown in Table 4, compared with commercially available liquid defluorinating agents, the defluorinating agent of this invention significantly reduced the fluoride concentration in the supernatant after treating industrial wastewater, and significantly increased the defluorination retention rate. Long-term storage observation revealed that commercially available liquid defluorinating agents all exhibited precipitation and stratification, while the defluorinating agent of this invention did not. Therefore, compared with commercially available liquid defluorinating agents, the defluorinating agent of this invention has a significant defluorination effect and excellent stability.

Claims

1. A defluoridating agent for industrial wastewater, characterized in that... It is made from the following raw materials in parts by weight: 3-7 parts sodium carboxymethyl cellulose, 20-25 parts modified attapulgite dispersion, 30-35 parts polyaluminum solution, 10-15 parts hydroxyapatite nano dispersion, 1-3 parts chitosan quaternary ammonium salt, 0.5-2 parts ferric ammonium sulfate, 1-3 parts potassium sodium tartrate, 1-3 parts modified nano magnesium oxide, 2-4 parts modified biochar, 1-3 parts Fe / Al modified kaolin material, and 70-90 parts deionized water.

2. The defluoridating agent for industrial wastewater according to claim 1, characterized in that... The solid content of the modified attapulgite dispersion is 20-30%, the mass concentration of the polyaluminum solution is 8-12%, and the solid content of the hydroxyapatite nano-dispersion is 10-15%.

3. The defluoridating agent for industrial wastewater according to claim 1, characterized in that... The method for preparing modified attapulgite dispersion is as follows: attapulgite is crushed, soaked in sulfuric acid solution, washed, and dried to obtain acidified attapulgite; then the acidified attapulgite is mixed with hexadecyltrimethylammonium bromide solution, stirred and reacted, filtered to obtain modified attapulgite; deionized water is added to the modified attapulgite and dispersed at high speed to obtain modified attapulgite dispersion.

4. The defluoridating agent for industrial wastewater according to claim 1, characterized in that... The preparation method of hydroxyapatite nano-dispersion is to dissolve calcium chloride and diammonium hydrogen phosphate in deionized water, add ammonia water to adjust the pH value under stirring, carry out hydrothermal reaction, cool, centrifuge, and wash to obtain nano-hydroxyapatite; add deionized water to nano-hydroxyapatite, then add sodium hexametaphosphate, and disperse by ultrasonication to obtain hydroxyapatite nano-dispersion.

5. The defluoridating agent for industrial wastewater according to claim 1, characterized in that... The modified nano-magnesium oxide is prepared by dissolving rare earth salts and ligands in deionized water to obtain a rare earth complex solution; adding nano-magnesium oxide to anhydrous ethanol and ultrasonically dispersing it to obtain a nano-magnesium oxide suspension; then adding the rare earth complex solution dropwise to the nano-magnesium oxide suspension, stirring at a constant temperature, centrifuging and washing, drying, and grinding into powder to obtain modified nano-magnesium oxide.

6. The defluoridating agent for industrial wastewater according to claim 5, characterized in that... The molar ratio of rare earth salt to ligand is 1:2-3, the mass ratio of rare earth salt to deionized water is 1:50-100, the rare earth salt is lanthanum nitrate or cerium sulfate, and the ligand is citric acid; the concentration of the nano magnesium oxide suspension is 5-10 g / L; the ratio of nano magnesium oxide to rare earth complex solution in the nano magnesium oxide suspension is 1:10-20, where nano magnesium oxide is expressed in g and rare earth complex solution is expressed in mL.

7. The defluoridating agent for industrial wastewater according to claim 1, characterized in that... The modified biochar is prepared by adding granular biochar to a nitric acid solution and soaking it to obtain activated biochar. Then, the activated biochar is added to a pyrrole solution for impregnation, FeCl3 solution is added dropwise to carry out a polymerization reaction, and then it is treated at high temperature under an ammonia atmosphere. It is then washed with dilute hydrochloric acid and distilled water in sequence and dried to obtain modified biochar.

8. The defluoridating agent for industrial wastewater according to claim 7, characterized in that... The concentration of nitric acid solution is 15-20 wt.%; the ratio of biochar to nitric acid solution is 1:10-15, with biochar measured in g and nitric acid solution measured in mL; the soaking temperature is 15-20℃, and the soaking time is 10-12 h; the concentration of pyrrole solution is 5-20 g / L; the mass ratio of activated biochar to pyrrole solution is 1:3-5; the impregnation temperature is 10-20℃, and the impregnation time is 15-20 h; the ratio of activated biochar to FeCl3 solution is 1:20-30, with activated biochar measured in g and FeCl3 solution measured in mL; the concentration of FeCl3 solution is 14-16 g / L; the polymerization reaction temperature is 10-12℃, and the polymerization reaction time is 20-22 h; the high-temperature treatment temperature is 800-900℃, and the high-temperature treatment time is 2-3 h; the drying temperature is 100-110℃, and the drying time is 10-12 h.

9. The defluorinating agent for industrial wastewater according to claim 1, characterized in that... The preparation method of Fe / Al modified kaolin material includes the following steps: (A) Dissolve ferric nitrate and aluminum isopropoxide in anhydrous ethanol, add ammonia to adjust the pH, and stir at a constant temperature to obtain Fe / Al sol; (B) Kaolin was added to anhydrous ethanol and ultrasonically dispersed to obtain a suspension. The suspension was then added to Fe / Al sol, stirred, allowed to stand, dried, calcined, and ground to obtain Fe / Al modified kaolin material.

10. A method for preparing a defluorinating agent for industrial wastewater according to any one of claims 1-9, characterized in that... Includes the following steps: (1) Sodium carboxymethyl cellulose, chitosan quaternary ammonium salt, potassium sodium tartrate and ferric ammonium sulfate were added to deionized water in sequence and stirred to prepare a base solution; (2) Add modified nano-magnesium oxide, modified biochar and Fe / Al modified kaolin material to the base solution in sequence, and stir until evenly dispersed; (3) Then add polyaluminum solution, modified attapulgite dispersion and hydroxyapatite nano dispersion in sequence, and stir continuously to obtain defluorinating agent for industrial wastewater.

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