Modified fluorine removal agent, fluorine removal method for industrial wastewater, and fluorine removal system

Abstract

This invention provides a modified defluorinating agent, a method for defluorinating industrial wastewater, and a defluorinating system, relating to the field of industrial wastewater treatment technology. The preparation method of the modified defluorinating agent includes: S101. Placing phosphogypsum powder in a sealed container, and introducing oxygen into the sealed container to oxidize the surface of the phosphogypsum powder, obtaining a phosphogypsum matrix; S102. Adding carbon fiber and aluminate coupling agent to the phosphogypsum matrix obtained in step S101 to react, and after the reaction is complete, adding the resulting product to an aluminum salt solution, reacting under heating and stirring; S103. After the reaction in the aluminum salt solution in step S102 is complete, filtering and drying the resulting mixture to obtain the modified defluorinating agent. This invention can effectively reduce the fluoride ion concentration and reduce the hardness of wastewater after treatment.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to a modified defluorinating agent, a method for defluorinating industrial wastewater, and a defluorinating system. Background Technology

[0002] Hydrofluoric acid generates fluoride-containing wastewater during photovoltaic cell cleaning and chip etching processes; fluoride-containing electrolytes used in processes such as chromium and nickel plating also eventually enter wastewater, forming fluoride ion pollutants; during bauxite smelting, fluorides in the ore release fluoride ions into the wastewater during high-temperature reactions. Meanwhile, fluorochemicals are a branch of chemical materials production using fluorides as raw materials, divided into inorganic fluorochemicals and organic fluorochemicals, falling under the category of new chemical materials. All of these industries are key sectors receiving government support; therefore, the fluoride-containing wastewater generated by these industries needs to be taken seriously and treated promptly to prevent further environmental pollution.

[0003] Existing defluoridation technologies for fluoride-containing wastewater commonly use calcium ions for defluorination, with calcium chloride and lime being the most common calcium ions. Alternatively, activated alumina, aluminum salts (such as polyaluminum chloride and aluminum sulfate), iron salts (such as polyferric sulfate), calcium salts (such as calcium chloride and calcium hydroxide), and rare earth modified materials can be used as alternatives. Other commonly used techniques include defluoridating agents or ion exchange resins.

[0004] However, all of the above processes have a common drawback: the final effluent still has a high fluoride content. Even with reverse osmosis membrane defluorination technology, the fluoride content on the concentrate side is still very high, requiring high secondary treatment costs. Summary of the Invention

[0005] This invention addresses the problem that the final effluent from fluoride-containing wastewater treatment technologies still has a high fluoride ion content. It provides a modified defluorinating agent that can achieve highly efficient fluoride ion removal, reduce the fluoride ion concentration to below 1 ppm, alleviate the pressure on downstream membrane systems, slow down membrane fouling, and simultaneously lower the material selection standards for subsequent systems, thus reducing investment. It is also a method and system for defluorinating industrial wastewater.

[0006] The technical solution adopted in this invention is:

[0007] A modified defluorinating agent, prepared by a method comprising:

[0008] S101. Place phosphogypsum powder in a sealed container, and introduce oxygen into the sealed container to oxidize the surface of the phosphogypsum powder to obtain a phosphogypsum matrix.

[0009] S102. Add carbon fiber and aluminate coupling agent to the phosphogypsum matrix obtained in step S101 and react. After the reaction is completed, add the product to the aluminum salt solution and react under heating and stirring.

[0010] S103. After the reaction in the aluminum salt solution in step S102 is completed, the resulting mixture is filtered and dried to obtain the modified defluorinating agent.

[0011] Furthermore, the particle size of the phosphogypsum particles used in step S101 is 100-200 μm; the mass ratio of the phosphogypsum matrix, carbon fiber, and aluminate coupling agent in step S102 is 2-4:1-3:2-5; and the particle size of the carbon fiber added in step S102 is 80-100 μm.

[0012] Further, the mass concentration of the aluminum salt solution in step S102 is 10~30%; the aluminum salt solution in step S102 is an aluminum sulfate solution or an aluminum oxide suspension.

[0013] A method for defluoridation of industrial wastewater, comprising:

[0014] S10. Add the modified defluorinating agent as described above to the industrial wastewater containing fluoride ions to be treated, and stir.

[0015] S20. Add quicklime to the industrial wastewater treated in step S10, and stir and adjust the pH value of the solution;

[0016] S30. Add coagulant to the industrial wastewater treated in step S20 and stir; then add flocculant and stir to obtain defluoridated water.

[0017] Furthermore, the method for defluoridating the industrial wastewater also includes:

[0018] S40. Add sodium carbonate to the defluoridated water treated in step S30 to obtain secondary defluoridated water.

[0019] Furthermore, in step S10, the industrial wastewater to be treated is industrial wastewater containing aluminum sulfate; the mass ratio of the modified defluorinating agent to the aluminum sulfate in the industrial wastewater to be treated is 6~10:1.

[0020] Furthermore, in step S20, the molar ratio of quicklime to the modified defluorinating agent added in step S10 is 1~5:1.

[0021] Furthermore, the step of adjusting the pH value of the solution in step S20 includes: first adjusting the pH value to be greater than 10 and stirring the reaction thoroughly; then adjusting the pH to 6-8 and adding aluminum salt defluorinating agent.

[0022] Furthermore, the coagulant used in step S30 is polyaluminum chloride (PAC), and the flocculant used in step S30 is polyacrylamide (PAM); the dosage of PAC is more than 3% of the mass concentration of the industrial wastewater; the dosage of PAM is more than 3% of the mass concentration of the industrial wastewater.

[0023] A defluoridation system for industrial wastewater uses the defluoridation method for industrial wastewater as described above to treat industrial wastewater; the defluoridation system for industrial wastewater includes a primary reaction tank and a secondary reaction tank; steps S10, S20 and S30 are carried out in the primary reaction tank; and step S40 is carried out in the secondary reaction tank.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention employs coagulation and sedimentation to remove fluoride ions from industrial wastewater. By combining lime with a specially modified defluorinating agent, the removal efficiency of fluoride ions is improved, while simultaneously removing fluoride impurities. This results in a fluoride ion removal rate of over 90% in the defluorinated water, with a final effluent fluoride concentration of less than 1 ppm. This ensures the smooth operation of subsequent membrane systems and reduces the risk of scaling. The combination of quicklime and the modified defluorinating agent is particularly suitable for the one-time treatment of industrial wastewater with high fluoride ion content, enabling the production of defluorinated water with a fluoride ion concentration of less than 1 ppm from high-fluoride-ion wastewater in a single treatment. This solves the problem of excessively high fluoride ion content in the final effluent from existing fluoride wastewater defluorination technologies.

[0026] 2. The defluorination system of the present invention, by setting up two-stage reaction tanks, conducts defluorination and hardness reduction reactions in different reaction tanks respectively. This ensures that the settled flocs will not be carried out again due to reaction stirring, and will not cause the formed flocs to be broken up, resulting in the precipitation of removed pollutants. This two-stage sedimentation can improve the removal efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the preparation method of the modified defluorinating agent of the present invention;

[0029] Figure 2 This is a flowchart of the defluorination method of the present invention;

[0030] Figure 3This is a schematic diagram of the defluorination system of the present invention;

[0031] Figure 4 The images show actual industrial wastewater before treatment in the embodiments and comparative examples of this invention.

[0032] Figure 5 This is a photograph of the defluoridated water from Embodiment 1 of the present invention.

[0033] Figure 6 This is a physical image of the defluoridated water from Comparative Example 1 of the present invention;

[0034] Figure 7 This is a physical image of the defluoridated water from Comparative Example 2 of the present invention;

[0035] Figure 8 This is a physical image of the defluoridated water from Comparative Example 3 of the present invention.

[0036] Attached diagram label: 100 - Primary reaction tank;

[0037] 200-Secondary reaction tank;

[0038] 300-flocculation tank;

[0039] 400- Inclined tube sedimentation tank;

[0040] 500-neutralization pool. Detailed Implementation

[0041] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention.

[0043] The embodiments of the invention will now be described in detail with reference to the accompanying drawings.

[0044] Implementation Method 1

[0045] To address the issue of persistently high fluoride ion levels in the effluent from existing fluoride removal technologies for fluoride-containing wastewater, the applicant's research revealed that current calcium ion defluorination methods require large feedstock dosages (typically 15:1), resulting in high residual hardness and low defluorination efficiency, making it difficult to reduce the fluoride ion concentration in the treated water to below 20 ppm. Similarly, existing wastewater treatment technologies using defluorinating agents also require large dosages and suffer from low efficiency, rarely reducing the fluoride ion concentration to below 5 ppm. Furthermore, further defluorination using ion exchange resins is prohibitively expensive and cannot guarantee a final fluoride ion concentration below 1 ppm. Therefore, this invention provides a method for removing fluoride ions from industrial wastewater, suitable for wastewater with low or high fluoride ion concentrations, accompanied by high hardness, and for wastewater requiring downstream membrane systems. It is particularly suitable for industries requiring zero-discharge wastewater treatment. This invention achieves highly efficient fluoride ion removal, reducing the fluoride ion concentration to below 1 ppm, alleviating pressure on downstream membrane systems, mitigating membrane fouling, and lowering the material requirements for subsequent systems, thus reducing investment. Please refer to [link to relevant documentation]. Figure 1 The defluoridation method for this industrial wastewater mainly includes the following steps:

[0046] S10. The industrial wastewater containing fluoride ions to be treated is added to the primary reaction tank. A modified defluorinating agent is added to the industrial wastewater, and the mixture is stirred. This embodiment uses a special modified defluorinating agent. The raw materials for preparing this modified defluorinating agent contain carbon fiber and aluminate coupling agent components, which can precipitate fluoride ions and adsorb fluorides, thereby achieving a comprehensive defluorination effect.

[0047] S20. Add slaked lime to the industrial wastewater treated in step S10, and stir and adjust the pH of the solution. Calcium ions in the slaked lime can react with fluoride ions to form calcium fluoride precipitate. Furthermore, by adding a modified defluorinating agent beforehand, the agent adsorbs and polymerizes the fluoride ions, improving the efficiency of the slaked lime in treating fluoride ions. Simultaneously, because F⁻ reacts with H⁺ to form weakly ionized HF under acidic conditions, affecting the precipitation reaction, and because HF is corrosive, the pH of the solution needs to be adjusted to alkaline after stirring.

[0048] S30. Add PAC (polyaluminum chloride) to the industrial wastewater treated in step S20 and stir. After stirring, add PAM (polyacrylamide) and stir again to obtain defluoridated water. PAC is an inorganic polymeric coagulant that neutralizes electrical charge, destabilizing tiny colloids and suspended particles in the water, causing them to initially coagulate into fine flocs. PAM is an organic polymeric flocculant that, through adsorption and bridging, connects the fine flocs formed by PAC into large, dense flocs, accelerating sedimentation. These large flocs settle rapidly, thus achieving efficient separation of impurities from water.

[0049] The present invention provides a method for defluoridating industrial wastewater using coagulation and sedimentation. By combining lime with a specially modified defluorinating agent, the removal efficiency of fluoride ions is improved, while simultaneously removing fluoride impurities. This results in a fluoride removal rate of over 90% in the defluorinated water, with a final effluent fluoride concentration of less than 1 ppm. This method also ensures the smooth operation of subsequent membrane systems and reduces the risk of scaling. The combination of quicklime and the modified defluorinating agent is particularly suitable for the one-time treatment of industrial wastewater with high fluoride ion content, enabling the production of defluorinated water with a fluoride ion concentration of less than 1 ppm from high-fluoride-ion wastewater in a single treatment. This solves the problem of excessively high fluoride ion content in the final effluent from existing defluoridation technologies for fluoride-containing wastewater.

[0050] In addition, this embodiment also accelerates the separation of impurities and water by adding a coagulation and flocculation combination of PAC and PAM.

[0051] Preferably, in step S10 of this embodiment, the industrial wastewater to be treated is industrial wastewater containing aluminum sulfate, and the mass ratio of the modified defluorinating agent to the aluminum sulfate in the industrial wastewater to be treated is 6~10:1, which can ensure sufficient defluorination effect and avoid wasting raw materials.

[0052] Furthermore, the modified defluorinating agent used in step S10 of this embodiment is prepared by the following steps:

[0053] S101. Place phosphogypsum powder in a sealed container, and introduce oxygen into the sealed container to oxidize the surface of the phosphogypsum powder to obtain a phosphogypsum matrix.

[0054] S102. Add carbon fiber and aluminate coupling agent to the phosphogypsum matrix obtained in step S101 and react. After the reaction is completed, add the product to the aluminum salt solution and react under heating and stirring.

[0055] S103. After the reaction in the aluminum salt solution in step S102 is completed, the resulting mixture is filtered and dried to obtain the modified defluorinating agent for use.

[0056] This modified defluorinating agent can form aluminum salt polymers with fluoride ions in water, co-precipitating to remove fluoride ions. It can also adsorb some fluorides, which precipitate together to enhance the defluorination effect. Preferably, the surface oxidation step in S101 takes 40-60 minutes; the phosphogypsum particles used in S101 have a particle size of 100-200 μm. Preferably, the mass ratio of phosphogypsum matrix, carbon fiber, and aluminate coupling agent in S102 is 2-4:1-3:2-5; the carbon fiber added in S102 has a particle size of 80-100 μm. Furthermore, the mass concentration of the aluminum salt solution in S102 is 10-30%; the aluminum salt solution in S102 is an aluminum sulfate solution or an alumina suspension; the heating temperature of the aluminum salt solution in S102 is 50-70°C; and the stirring time of the aluminum salt solution in S102 is 40-60 minutes. Under the above-mentioned preferred process conditions, a modified defluorinating agent with superior and stable adsorption performance can be obtained.

[0057] Preferably, in step S20 of this embodiment, the molar ratio of quicklime to the modified defluorinating agent added in step S10 is 1 to 5:1. Under this ratio, the two work well together to remove fluoride.

[0058] Preferably, in step S20 of this embodiment, aluminum ions and hydroxide ions in the modified defluorinating agent combine to form aluminum hydroxide precipitate, while some fluoride is adsorbed and precipitates. After adding quicklime, the pH value is measured to ensure that pH > 10. If the pH value is low, an appropriate amount of sodium hydroxide is added to raise the pH value. When the stability of the modified defluorinating agent is insufficient, the step of adjusting the pH value of the solution in step S20 may include: first adding quicklime and adjusting the pH value of the solution to be greater than 10, stirring the reaction thoroughly to ensure that the pH value of the wastewater is greater than 10 so that fluoride ions can first react with calcium to form calcium fluoride precipitate and be removed; then adjusting the pH to 6-8, adding aluminum salt defluorinating agent to further remove the residual low concentration of fluoride ions. Fluoride ions and aluminum ions form a secondary precipitate of aluminum fluoride, thereby compensating for the fluoride ion residue caused by the insufficient stability of the modified defluorinating agent and ensuring that the removal amount of fluoride ions meets the standard.

[0059] Preferably, in step S30 of this embodiment, PAC is added and stirred for 6-8 minutes, and PAM is added and stirred for at least 5 minutes to ensure that the effluent fluoride concentration is less than 1 ppm. Furthermore, the dosage of PAC is maintained at at least 3% of the industrial wastewater mass concentration, and the dosage of PAM is maintained at at least 3% of the industrial wastewater mass concentration.

[0060] Furthermore, the defluoridation method for industrial wastewater in this embodiment also includes the following steps:

[0061] S40. The defluoridated water treated in step S30 is added to the secondary reaction tank, and sodium carbonate is added to obtain secondary defluoridated water. The purpose of adding sodium carbonate at the end is to reduce the hardness of the defluoridated water. In step S40 of this embodiment, the amount of sodium carbonate added needs to ensure that the total hardness of the final effluent is less than 50 ppm to prevent excessive hardness from causing membrane scaling and clogging.

[0062] In this embodiment, sodium carbonate needs to be added last to remove calcium ions from the water. The reason why the modified defluorinating agent containing aluminum ions, quicklime, and sodium carbonate need to be added in sequence is that if sodium carbonate is added first, it will affect the removal of fluoride ions from the water by calcium ions, resulting in insufficient removal of fluoride. If quicklime and sodium carbonate are added first, the resulting calcium hydroxide is slightly soluble in water, which will affect the removal of fluoride from the water by the modified defluorinating agent, and additional aluminum ions will need to be added to remove fluoride. Therefore, the order of aluminum ions, quicklime, and sodium carbonate must be followed to ensure fluoride removal while reducing the high hardness of the defluorinated water caused by calcium and magnesium.

[0063] In one or more other embodiments, step S30 of this embodiment may further involve adding other types of coagulants and flocculants to the primary reaction tank. The coagulants and flocculants ensure the settling performance of the flocs, thereby better adsorbing and carrying fluoride ions from the effluent, ensuring that the effluent fluoride ion level is as low as possible.

[0064] Implementation Method 2

[0065] Based on the above embodiments, a defluoridation system for industrial wastewater using the above-mentioned defluoridation method for industrial wastewater is further proposed, and a second embodiment is provided below.

[0066] Please see Figure 2 The defluoridation system for industrial wastewater in the second embodiment is used to treat fluoride-containing industrial wastewater. This system can efficiently remove fluoride ions, reducing the fluoride ion concentration to below 1 ppm, alleviating pressure on the downstream membrane system, mitigating membrane fouling, and lowering the material selection standards for subsequent systems, thus reducing investment. The defluoridation system mainly includes a primary reaction tank 100 and a secondary reaction tank 200 connected in sequence.

[0067] The defluoridation system for industrial wastewater in this embodiment uses a two-stage reaction tank to carry out defluoridation and hardness reduction separately. This ensures that the settled flocs are not carried out again by the reaction and stirring, and also prevents the formed flocs from being broken up and causing the removed pollutants to precipitate out. This two-stage sedimentation can improve the removal efficiency.

[0068] Furthermore, the defluoridation system for industrial wastewater in this embodiment can also include supporting treatment equipment such as a flocculation tank 300, an inclined tube sedimentation tank 400, and a neutralization tank 500 between the primary reaction tank 100 and the secondary reaction tank 200. Specifically, the primary reaction tank 100 is connected to the neutralization tank 500, the neutralization tank 500 is connected to the flocculation tank 300, the flocculation tank 300 is connected to the inclined tube sedimentation tank 400, and the inclined tube sedimentation tank 400 is then connected to the secondary reaction tank 200.

[0069] Example 1

[0070] The modified defluorinating agent is first prepared, including the following steps:

[0071] Phosphogypsum powder was placed in a sealed container, and oxygen was introduced into the container for 35 minutes to oxidize the surface and obtain a phosphogypsum matrix. Then, carbon fiber and aluminate coupling agent were added to react the phosphogypsum matrix, carbon fiber and aluminate coupling agent in a mass ratio of 1:1:1. After the reaction was completed, the product was added to a 40% (mass concentration) aluminum sulfate solution and stirred for 50 minutes under heating conditions at 60°C. After the reaction was completed, the product was filtered and dried to prepare a modified defluorinating agent.

[0072] Next, photovoltaic semiconductor wastewater was used as the wastewater to be treated, with a fluoride ion concentration of 40 ppm. The modified defluorinating agent was added at a molar ratio of 1:1 to the fluoride ions in the water to remove the fluoride ions. Then, quicklime was added at a mass ratio of 1:1 to the modified defluorinating agent. Then, 50 ppm PAC and 10 ppm PAM were added. After stirring and settling, the final supernatant was taken as the effluent. 150 ppm sodium carbonate was added to it, and the fluoride ion concentration of the defluorinated water was found to be 0.8 ppm.

[0073] Comparative Example 1

[0074] Using photovoltaic semiconductor wastewater as the wastewater to be treated, the fluoride ion concentration was 40 ppm. Calcium chloride was added to remove fluoride ions at a molar ratio of 1:1 to calcium chloride to fluoride ions in the water. Then, quicklime was added at a mass ratio of 1:1 to calcium chloride. Next, 50 ppm PAC and 10 ppm PAM were added. After stirring and settling, the final supernatant was taken as the effluent. 150 ppm sodium carbonate was added to it, and the fluoride ion concentration of the defluorinated water was measured to be 18.7 ppm.

[0075] Comparative Example 2

[0076] The modified defluorinating agent is first prepared, including the following steps:

[0077] Phosphogypsum powder was placed in a sealed container, and oxygen was introduced into the sealed container for 35 minutes to oxidize the surface and obtain a phosphogypsum matrix. Then, carbon fiber was added to mix the phosphogypsum and carbon fiber at a mass ratio of 1:1. The resulting product was then added to a 40% (mass concentration) aluminum sulfate solution and stirred for 50 minutes under heating conditions at 70°C. After the reaction was completed, the mixture was filtered and dried to prepare a modified aluminum salt.

[0078] Next, photovoltaic semiconductor wastewater was used as the wastewater to be treated, with a fluoride ion concentration of 40 ppm. The modified aluminum salt was added at a molar ratio of 1:1 to the fluoride ions in the water to remove the fluoride ions. Then, quicklime was added at a mass ratio of 1:1 to the modified aluminum salt. After that, 50 ppm PAC and 10 ppm PAM were added. After stirring and settling, the final supernatant was taken as the effluent. 150 ppm sodium carbonate was added to it, and the fluoride ion concentration of the defluorinated water was found to be 10.3 ppm.

[0079] Comparative Example 3

[0080] The modified defluorinating agent is first prepared, including the following steps:

[0081] Phosphogypsum powder was placed in a sealed container, and oxygen was introduced into the sealed container for 35 minutes to oxidize the surface and obtain a phosphogypsum matrix. Then, an aluminate coupling agent was added, and the phosphogypsum matrix and the aluminate coupling agent were mixed at a mass ratio of 1:1 to react. After the reaction was completed, the product was added to a 40% (mass concentration) aluminum sulfate solution and stirred for 50 minutes under heating conditions at 50°C. After the reaction was completed, the product was filtered and dried to obtain the modified aluminum salt.

[0082] Next, photovoltaic semiconductor wastewater was used as the wastewater to be treated, with a fluoride ion concentration of 40 ppm. The modified aluminum salt was added at a molar ratio of 1:1 to the fluoride ions in the water to remove the fluoride ions. Then, quicklime was added at a mass ratio of 1:1 to the modified aluminum salt. After that, 50 ppm PAC and 10 ppm PAM were added. After stirring and settling, the final supernatant was taken as the effluent. 150 ppm sodium carbonate was added to it, and the fluoride ion concentration of the defluorinated water was found to be 16.5 ppm.

[0083] Experimental results

[0084] The water treated in Example 1 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0085] Table 1

[0086]

[0087] As can be seen from Table 1, the modified defluorinating agent in Example 1, in addition to retaining the function of aluminum sulfate, also has a rougher surface due to the oxidation treatment, which allows it to adsorb more target pollutants. At the same time, it retains the function of forming a co-precipitate with fluoride ions. Since phosphogypsum, carbon fiber and aluminate coupling agent are added to the modified defluorinating agent to react, the adsorption capacity is also enhanced, and the removal rate can be greatly improved to 98%.

[0088] Comparative Example 1 uses calcium chloride to remove fluoride ions. Calcium ions and fluoride ions react to form calcium fluoride precipitate, which removes fluoride ions through chemical precipitation. However, the solubility product of calcium fluoride is fixed, which means that when a certain amount of calcium ions is added, it is impossible to remove fluoride ions further. Generally, it can only reduce fluoride ions to about 20 mg / L.

[0089] In Comparative Example 2, the modified aluminum salt was supplemented with phosphogypsum and carbon fiber, but no aluminate coupling agent was added for reaction. The adsorption capacity was not significantly enhanced, and the removal rate was only increased to 74.25%.

[0090] In Comparative Example 3, the modified defluorinating agent contained phosphogypsum and aluminate coupling agent, but no carbon fiber was added. Therefore, the adsorption capacity was poor and the removal rate was low, reaching only 58.75%.

[0091] At the same time, from Figures 3-6 The comparison also shows that the amount of impurities adsorbed and precipitated in Example 1 is significantly higher than that in Comparative Examples 1-3, indicating that the defluorination effect of the defluorination method of the present invention is greatly improved.

[0092] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A modified defluorinating agent, characterized in that, The preparation method of the modified defluorinating agent includes: S101. Place phosphogypsum powder in a sealed container, and introduce oxygen into the sealed container to oxidize the surface of the phosphogypsum powder to obtain a phosphogypsum matrix. S102. Add carbon fiber and aluminate coupling agent to the phosphogypsum matrix obtained in step S101 and react. After the reaction is completed, add the product to the aluminum salt solution and react under heating and stirring. S103. After the reaction in the aluminum salt solution in step S102 is completed, the resulting mixture is filtered and dried to obtain the modified defluorinating agent.

2. The modified defluorinating agent as described in claim 1, characterized in that, The particle size of the phosphogypsum particles used in step S101 is 100-200 μm; the mass ratio of the phosphogypsum matrix, carbon fiber and aluminate coupling agent in step S102 is 2-4:1-3:2-5; the particle size of the carbon fiber added in step S102 is 80-100 μm.

3. The modified defluorinating agent as described in claim 1, characterized in that, The mass concentration of the aluminum salt solution in step S102 is 10-30%; the aluminum salt solution in step S102 is an aluminum sulfate solution or an aluminum oxide suspension.

4. A method for defluoridation of industrial wastewater, characterized in that, Include: S10. Add the modified defluorinating agent as described in any one of claims 1-3 to the industrial wastewater containing fluoride ions to be treated, and stir. S20. Add quicklime to the industrial wastewater treated in step S10, and stir and adjust the pH value of the solution; S30. Add coagulant to the industrial wastewater treated in step S20 and stir; then add flocculant and stir to obtain defluoridated water.

5. The method for defluoridation of industrial wastewater as described in claim 4, characterized in that, The method for defluoridating industrial wastewater further includes: S40. Add sodium carbonate to the defluoridated water treated in step S30 to obtain secondary defluoridated water.

6. The method for defluoridation of industrial wastewater as described in claim 4, characterized in that, In step S10, the industrial wastewater to be treated is industrial wastewater containing aluminum sulfate; the mass ratio of the modified defluorinating agent to the aluminum sulfate in the industrial wastewater to be treated is 6~10:

1.

7. The method for defluoridation of industrial wastewater as described in claim 4, characterized in that, In step S20, the molar ratio of quicklime to the modified defluorinating agent added in step S10 is 1~5:

1.

8. The method for defluoridation of industrial wastewater as described in claim 4, characterized in that, The step of adjusting the pH value of the solution in step S20 includes: first adjusting the pH value to be greater than 10 and stirring the reaction thoroughly; then adjusting the pH to 6-8 and adding aluminum salt defluorinating agent.

9. The method for defluoridation of industrial wastewater as described in claim 4, characterized in that, The coagulant used in step S30 is polyaluminum chloride (PAC), and the flocculant used in step S30 is polyacrylamide (PAM); the dosage of PAC is more than 3% of the mass concentration of the industrial wastewater; the dosage of PAM is more than 3% of the mass concentration of the industrial wastewater.

10. A defluoridation system for industrial wastewater, characterized in that, The industrial wastewater is treated using the defluorination method for industrial wastewater as described in claim 5; the defluorination system for industrial wastewater includes a primary reaction tank (100) and a secondary reaction tank (200); steps S10, S20 and S30 are carried out in the primary reaction tank (100); and step S40 is carried out in the secondary reaction tank (200).

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