Lanthanum-loaded fluorite spherical seed and method for treating fluorine-containing wastewater by using the same

Abstract

The application provides a lanthanum-loaded fluorite ball seed and a method for treating fluorine-containing wastewater, and a preparation method of the lanthanum-loaded fluorite ball seed comprises the following steps: firstly, mixing sodium silicate and polyacrylamide, and then uniformly dispersing the mixture in an aqueous solution to obtain a composite binder; secondly, uniformly mixing calcium fluoride powder and the composite binder, and then feeding the mixture into a granulator to granulate, and taking out and drying the fluorite ball particles; finally, soaking the fluorite ball particles in a lanthanum solution, and then baking to obtain the lanthanum-loaded fluorite ball seed. When the lanthanum-loaded fluorite ball seed is used for fluorine-containing wastewater treatment, the fluorite ball seed induces the crystallization of calcium fluoride on the surface of the fluorite ball seed, and the fluorine ions in the solution are effectively removed. The defluorination rate of the application is high, the purity of the fluorite ball seed after induced crystallization and the surface-loaded calcium fluoride is high, and the fluorite ball seed and the calcium fluoride can be recycled twice, and no sludge and other wastes are generated in the reaction process, so that no additional foreign matter removing device is needed.

Description

Technical Field

[0001] This invention relates to a method for preparing lanthanum-loaded fluorite spherical seeds and a method for deep treatment of fluoride-containing wastewater by filtering and crystallizing using lanthanum-loaded fluorite spherical seeds, belonging to the field of industrial wastewater treatment technology. Background Technology

[0002] Faced with the challenges of global climate change and resource scarcity, the recovery of high-value elements from wastewater has become a research hotspot in the field of wastewater resource utilization. With the mining of fluoride ores and the discharge of fluoride-containing wastewater from industries such as electronics and dyeing, the fluoride content in water bodies has increased significantly. Achieving the resource recovery of valuable substances from wastewater is of great significance for reducing wastewater treatment costs and improving the level of the social circular economy. Furthermore, the discharge of large amounts of fluoride-containing wastewater seriously endangers human health. When the fluoride concentration in drinking water exceeds 3 mg / L, it may lead to fluorosis (such as skeletal deformities and dental abnormalities), cognitive impairment, infertility, and diseases of organs such as endocrine glands, thyroid glands, and kidneys. Therefore, the recovery and treatment of fluoride ions from wastewater has become an urgent environmental challenge.

[0003] Currently, domestic and international defluoridation technologies mainly include chemical precipitation, coagulation, adsorption, ion exchange, electrodialysis, and reverse osmosis. Among these, chemical precipitation primarily involves adding calcium hydroxide or soluble calcium salts (such as calcium chloride) to the wastewater to remove fluoride. 2+ With F - The reaction produces CaF2 precipitate, thereby removing fluoride. Due to its low cost, simple operation, and high removal rate, chemical precipitation is widely used for fluoride removal in wastewater. Based on this, some research focuses on developing induced crystallization for fluoride removal. For example, patent CN 118666388 A proposes an integrated fluidized bed-based fluoride removal method and system, including two-stage fluoride removal and porous adsorption packing treatment. It boasts high fluoride removal efficiency, but its operation is cumbersome and unsuitable for practical engineering applications. Furthermore, CN116947179 A discloses a fluidized bed deep fluoride removal device, including main equipment, piping systems, and automatic control systems, which is also cumbersome. This process uses flocculation for deep fluoride removal, which wastes aluminum or iron salts and generates large amounts of fluoride-containing, aluminum- or iron-containing chemical sludge, causing secondary pollution.

[0004] As can be seen from the above, existing methods for treating fluoride-containing wastewater all have some problems. Fluidized bed induced crystallization technology for treating fluoride-containing wastewater produces effluent concentrations of 10-20 mg / L, which cannot meet the requirements for direct discharge. Further treatment with defluorinating agents involves large dosages and generates a large amount of water-rich sludge. Because the sludge has a high water content and low quality, it is difficult to effectively recover it for subsequent secondary applications, thus increasing operating costs.

[0005] Given the current situation, how to deeply remove fluoride ions from water while simultaneously recovering economically viable calcium fluoride is a pressing technical problem that needs to be solved in the field of industrial wastewater resource recovery. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a lanthanum-loaded fluorite spherical seed crystal and a method for treating fluoride-containing wastewater. The method involves preparing lanthanum-loaded fluorite spherical seed crystals, filling these crystals into PVC pipes to remove fluoride ions from the water while simultaneously recovering calcium fluoride. This method effectively removes fluoride ions from fluoride-containing wastewater, requires no chemical reagents, operates stably, and yields high-purity recovered calcium fluoride, thus providing green and sustainable environmental benefits.

[0007] The technical solution adopted to achieve the above-mentioned objectives of this invention is as follows:

[0008] A method for preparing lanthanum-loaded fluorite spheroid seed crystals includes the following steps:

[0009] (1) Sodium silicate and polyacrylamide were mixed and then ultrasonically dispersed in an aqueous solution to obtain a composite adhesive;

[0010] (2) After uniformly mixing calcium fluoride powder with composite binder, the mixture is fed into a granulator for granulation, and then dried to obtain fluorite sphere particles.

[0011] (3) The obtained fluorite sphere particles are soaked in lanthanum solution and then roasted to obtain lanthanum-loaded fluorite sphere seed crystals.

[0012] Furthermore, in step (1), the mass ratio of sodium silicate to polyacrylamide is 0.5~1.2:1. After sodium silicate and polyacrylamide are ultrasonically dispersed in the aqueous solution, the pH is adjusted to 5.0~7.0.

[0013] Furthermore, in step (2), the calcium fluoride powder is derived from the photovoltaic wastewater recovery products, wherein the calcium fluoride purity is above 92%.

[0014] Furthermore, in step (2), the mixture obtained by uniformly mixing calcium fluoride powder and composite binder contains 3-5 wt% sodium silicate and 10-20% water.

[0015] Further, the granulation step in step (2) is as follows: calcium fluoride powder and composite binder are stirred into a gypsum-like substance and then fed into a shot rubbing machine to generate uniformly sized particles. The particles are polished and ground into spherical particles with a particle size of 0.6~1.2cm. The particles are then air-cooled in cold air at 20~30℃ for 2~4h. The drying step is as follows: the particles are placed in an electric heating blower dryer and dried at 40~60℃ for 8~12h.

[0016] Furthermore, the lanthanum solution mentioned in step (3) is a lanthanum nitrate or lanthanum chloride solution with a concentration of 0.1~0.5 mol / L and a soaking time of 0.5~2h, and is stirred during soaking; the specific steps of the roasting are as follows: the roasting temperature is 200~400℃ and the roasting time is 2~5h.

[0017] The lanthanum-loaded fluorite seed spheres prepared in this invention are used to treat fluoride-containing wastewater. The treatment method is as follows: Lanthanum-loaded fluorite seed spheres are filled into a PVC pipe. Fluoride-containing wastewater and calcium chloride solution are slowly injected from both ends of the bottom of the PVC pipe. The mixed solution after mixing submerges the fluorite seed spheres. After standing treatment, calcium fluoride in the mixed solution crystallizes on the surface of the fluorite seed spheres. After treatment, the treated solution is discharged. The fluoride ion removal rate in the treated solution is greater than 92%.

[0018] Furthermore, the inner diameter of the PVC pipe is 40~42mm, the height is 48~52cm, and the amount of lanthanum-loaded fluorite sphere seed crystals inside the PVC pipe is 300~1200g, with a filling height of 20~50cm.

[0019] Furthermore, the concentration of fluoride ions in the fluoride-containing wastewater is 5~20 mg / L, the molar ratio of fluoride ions to calcium chloride in the fluoride-containing wastewater is 1:0.5~0.6; the influent flow rate of the fluoride-containing wastewater and calcium chloride solution is 25~35 mL / min; during the static treatment, the temperature is maintained at 10~28℃, and the treatment time is 20~60 min.

[0020] Compared with the prior art, the lanthanum-loaded fluorite spheroid seeds and the method for treating fluoride-containing wastewater provided by the present invention have the following advantages:

[0021] (1) The PVC pipe of the present invention can provide suitable water pressure to promote the adhesion and crystallization of fluoride ions and calcium ions in the solution on the surface of fluorite sphere seed crystals; the lanthanum ions loaded on the fluorite sphere seed crystals can adsorb fluoride ions in the solution to generate lanthanum fluoride; the fluorite sphere seed crystals are doped with polyacrylamide, which is conducive to the flocculation and aggregation of fluoride ions and calcium ions on the seed crystal surface, promoting the induced calcium fluoride crystallization of the fluorite sphere seed crystals, and further promoting the removal of fluoride ions and resource recovery.

[0022] (2) No reagents are added during the wastewater treatment process, which saves costs. No sludge or other waste is generated during the reaction process, so no additional foreign matter removal device is needed. This treatment method can effectively remove fluoride ions from wastewater and recover calcium fluoride at the same time. It is stable in operation and has green and sustainable environmental benefits.

[0023] (3) The lanthanum-loaded fluorite spherical seed crystals and the calcium fluoride crystals generated after induced crystallization prepared in this invention have high purity and good economic benefits. At the same time, the overall structure of the wastewater treatment equipment is simple, easy to operate, and convenient for engineering promotion. Attached Figure Description

[0024] Figure 1 This is a photograph of the lanthanum-loaded fluorite sphere seed crystals prepared in Example 2;

[0025] Figure 2 Scanning electron microscope (SEM) images of the fluorite seed spheres prepared in Example 2 before and after fluorine removal;

[0026] Figure 3 XRD patterns of calcium fluoride raw material, AR calcium fluoride, and fluorite spheroid seed crystals prepared in Examples 1-3 and Comparative Examples 1-2;

[0027] Figure 4 Comparison chart of the purity of calcium fluoride raw material and calcium fluoride recovered in Examples 1-3 and Comparative Examples 1-2;

[0028] Figure 5 The graph shows the results of fluoride ion treatment in wastewater under different hydraulic retention times in Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited to the following embodiments. Example 1

[0030] A composite binder composed of sodium silicate and polyacrylamide was prepared, and the pH was adjusted to 6.5-7. Calcium fluoride recovered from wastewater was then added and thoroughly stirred to form a paste-like mixture. Sodium silicate and polyacrylamide were ultrasonically and uniformly dispersed in the aqueous solution at a mass ratio of 1:1. The calcium fluoride powder was derived from photovoltaic wastewater recovery products and had a purity of over 92%. The composite binder comprised 4 wt% of the mixed raw materials, and the moisture content of the mixed raw materials was 10%.

[0031] The resulting mixture was fed into a granulator for granulation, and then dried to obtain fluorite seed spheres with a diameter of 0.6~1.2cm. The specific granulation process was as follows: the raw materials were stirred into a gypsum-like consistency and then fed into a pelletizing machine to produce uniformly sized particles. These particles were then polished and ground into spherical particles with a diameter of 0.6~1.2cm. The resulting fluorite seed spheres were air-cooled at 23℃ for 2.5 hours. The fluorite seed spheres were then dried in an electrically heated forced-air dryer at 45℃ for 9 hours.

[0032] The obtained particles were soaked and stirred in a 0.1 mol / L lanthanum nitrate solution for 1 h, allowed to stand for 5 h, and then calcined at 300 °C for 4 h to obtain fluorite spherical seed crystals.

[0033] The prepared fluorite seed spheres were filled into a PVC pipe to a height of 50 cm. The filter media filling amount was 1200 g. The main component of the PVC pipe was polyvinyl chloride, and the inner diameter of the pipe was 42 mm, with a height of 52 cm.

[0034] Simulated industrial wastewater containing fluoride ions and a calcium chloride solution are slowly injected into both ends of a PVC pipe. Once the solution is mixed, fluorite spheres are submerged. The fluorite spheres act as seed crystals, inducing calcium fluoride to crystallize on their surface, effectively removing fluoride ions from the solution. - The concentration is 23.04 mg / L, and the molar ratio of fluoride ions to calcium chloride solution is 1:0.6. The fluoride-containing wastewater and calcium chloride solution must be simultaneously injected into the PVC pipe and mixed thoroughly, with an influent flow rate of 25 mL / min. Example 2

[0035] A composite binder composed of sodium silicate and polyacrylamide was prepared, and the pH was adjusted to 6.5-7. Calcium fluoride recovered from wastewater was then added and thoroughly stirred to form a paste-like mixture. Sodium silicate and polyacrylamide were ultrasonically and uniformly dispersed in the aqueous solution at a mass ratio of 1:1. The calcium fluoride powder was derived from photovoltaic wastewater recovery products and had a purity of over 92%. The composite binder comprised 3.5 wt% of the mixed raw materials, and the moisture content of the mixed raw materials was 10%.

[0036] The resulting mixture was fed into a granulator for granulation, and then dried to obtain fluorite seed spheres with a diameter of 0.6~1.2cm. The specific granulation process was as follows: the raw materials were stirred into a gypsum-like consistency and then fed into a pelletizing machine to produce uniformly sized particles. These particles were then polished and ground into spherical particles with a diameter of 0.6~1.2cm. The resulting fluorite seed spheres were air-cooled at 25℃ for 3 hours. The fluorite seed spheres were then dried in an electrically heated forced-air dryer at 50℃ for 10 hours.

[0037] The obtained particles were soaked and stirred in a 0.2 mol / L lanthanum nitrate solution for 1 h, allowed to stand for 5 h, and then calcined at 350 °C for 3 h to obtain fluorite spherical seed crystals.

[0038] The prepared fluorite spheres were filled into a PVC pipe to a height of 50 cm. The filter media filling amount was 1200 g. The main component of the PVC pipe was polyvinyl chloride, with an inner diameter of 42 mm and a height of 52 cm.

[0039] Simulated industrial wastewater containing fluoride ions and a calcium chloride solution are slowly injected into both ends of a PVC pipe. Once the solution is mixed, fluorite spheres are submerged. The fluorite spheres act as seed crystals, inducing calcium fluoride to crystallize on their surface, effectively removing fluoride ions from the solution. -The concentration is 23.12 mg / L, and the molar ratio of fluoride ions to calcium chloride solution is 1:0.6. The fluoride-containing wastewater and calcium chloride solution must be simultaneously injected into the PVC pipe and mixed thoroughly, with an influent flow rate of 28 mL / min. Example 3

[0040] A composite binder composed of sodium silicate and polyacrylamide was prepared, and the pH was adjusted to 6.5-7. Calcium fluoride recovered from wastewater was then added and thoroughly stirred to form a paste-like mixture. Sodium silicate and polyacrylamide were ultrasonically and uniformly dispersed in the aqueous solution at a mass ratio of 1:1. The calcium fluoride powder was derived from photovoltaic wastewater recovery products and had a purity of over 92%. The composite binder comprised 4.5 wt% of the mixed raw materials, and the moisture content of the mixed raw materials was 15%.

[0041] The resulting mixture was fed into a granulator for granulation, and then dried to obtain fluorite seed spheres with a diameter of 0.6~1.2cm. The specific granulation process was as follows: the raw materials were stirred into a gypsum-like consistency and then fed into a pelletizing machine to produce uniformly sized particles. These particles were then polished and ground into spherical particles with a diameter of 0.6~1.2cm. The resulting fluorite seed spheres were air-cooled at 28℃ for 3.5 hours. The fluorite seed spheres were then dried in an electrically heated forced-air dryer at 55℃ for 11 hours.

[0042] The obtained particles were soaked and stirred in a 0.3 mol / L lanthanum chloride solution for 1.5 h, allowed to stand for 5 h, and then calcined at 250 °C for 4.5 h to obtain fluorite spherical seed crystals.

[0043] The prepared fluorite seed spheres were filled into a PVC pipe to a height of 50 cm. The filter media filling amount was 1200 g. The main component of the PVC pipe was polyvinyl chloride, and the inner diameter of the pipe was 42 mm, with a height of 52 cm.

[0044] Simulated industrial wastewater containing fluoride ions and a calcium chloride solution are slowly injected into both ends of a PVC pipe. Once the solution is mixed, fluorite spheres are submerged. The fluorite spheres act as seed crystals, inducing calcium fluoride to crystallize on their surface, effectively removing fluoride ions from the solution. - The concentration is 22.28 mg / L, and the molar ratio of fluoride ions to calcium chloride solution is 1:0.5. The fluoride-containing wastewater and calcium chloride solution must be simultaneously injected into the PVC pipe and mixed thoroughly. The influent flow rate for both the fluoride-containing wastewater and calcium chloride solution is 33 mL / min.

[0045] Comparative Example 1

[0046] Sodium silicate was uniformly dispersed in an aqueous solution, and the pH was adjusted to 6.5-7. Calcium fluoride recovered from wastewater was then added and thoroughly stirred to form a paste-like mixture. The calcium fluoride powder was derived from photovoltaic wastewater recovery products and had a purity of over 92%. Sodium silicate accounted for 4 wt% of the mixed raw materials, and the moisture content of the mixed raw materials was 10%.

[0047] The obtained mixture is fed into a granulator for granulation, and then dried to obtain fluorite seed spheres with a diameter of 0.6~1.2cm. The specific granulation process is as follows: the raw material is stirred into a gypsum-like consistency and then fed into a pelletizing machine to produce uniformly sized particles. The particles are polished and ground into spherical particles with a diameter of 0.6~1.2cm. The resulting fluorite seed spheres are air-cooled at 20~30℃ for 2~4 hours. The fluorite seed spheres are then dried in an electrically heated forced-air dryer at 40~60℃ for 8~12 hours.

[0048] The prepared fluorite spheres were filled into a PVC pipe to a height of 50 cm. The filter media filling amount was 1200 g. The main component of the PVC pipe was polyvinyl chloride, with an inner diameter of 42 mm and a height of 52 cm.

[0049] Simulated industrial wastewater containing fluoride ions and a calcium chloride solution are slowly injected into both ends of a PVC pipe. Once the solution is mixed, fluorite spheres are submerged. The fluorite spheres act as seed crystals, inducing calcium fluoride to crystallize on their surface, effectively removing fluoride ions from the solution. - The concentration is 21.67 mg / L, and the molar ratio of fluoride ions to calcium chloride solution is 1:0.6. The fluoride-containing wastewater and calcium chloride solution must be simultaneously injected into the PVC pipe and mixed thoroughly, with an influent flow rate of 25 mL / min.

[0050] Comparative Example 2

[0051] A composite binder composed of sodium silicate and polyacrylamide was prepared, and the pH was adjusted to 6.5-7. Calcium fluoride recovered from wastewater was then added and thoroughly stirred to form a paste-like mixture. Sodium silicate and polyacrylamide were ultrasonically and uniformly dispersed in the aqueous solution at a mass ratio of 1:1. The calcium fluoride powder was derived from photovoltaic wastewater recovery products and had a purity of over 92%. The composite binder comprised 4 wt% of the mixed raw materials, and the moisture content of the mixed raw materials was 10%.

[0052] The obtained mixture is fed into a granulator for granulation, and then dried to obtain fluorite seed spheres with a diameter of 0.6~1.2cm. The specific granulation process is as follows: the raw material is stirred into a gypsum-like consistency and then fed into a pelletizing machine to produce uniformly sized particles. The particles are polished and ground into spherical particles with a diameter of 0.6~1.2cm. The resulting fluorite seed spheres are air-cooled at 20~30℃ for 2~4 hours. The fluorite seed spheres are then dried in an electrically heated forced-air dryer at 40~60℃ for 8~12 hours.

[0053] The prepared fluorite spheres were filled into a PVC pipe to a height of 50 cm. The filter media filling amount was 1200 g. The main component of the PVC pipe was polyvinyl chloride, with an inner diameter of 42 mm and a height of 52 cm.

[0054] Simulated industrial wastewater containing fluoride ions and a calcium chloride solution are slowly injected into both ends of a PVC pipe. Once the solution is mixed, fluorite spheres are submerged. The fluorite spheres act as seed crystals, inducing calcium fluoride to crystallize on their surface, effectively removing fluoride ions from the solution. - The concentration is 22.06 mg / L, and the molar ratio of fluoride ions to calcium chloride solution is 1:0.6. The fluoride-containing wastewater and calcium chloride solution must be simultaneously injected into the PVC pipe and mixed thoroughly, with an influent flow rate of 25 mL / min.

[0055] Comparative Example 3

[0056] No seed crystals were added in this comparative example. F in fluoride-containing wastewater - The concentration is 21.17 mg / L, and the molar ratio of fluoride ions to calcium chloride solution is 1:0.6. The fluoride-containing wastewater and calcium chloride solution must be simultaneously injected into the PVC pipe and mixed thoroughly, with an influent flow rate of 25 mL / min.

[0057] Results Analysis

[0058] A physical image of the lanthanum-loaded fluorite spheroids prepared in Example 2 is shown below. Figure 1 As shown, the prepared lanthanum-supported fluorite sphere seed crystals mainly contain C, O, F, Ca, and La. Further analysis revealed that La accounts for 17.22% of the total elements. This result indicates that Example 2 successfully synthesized lanthanum-supported fluorite sphere seed crystals, and that lanthanum was successfully loaded onto the fluorite sphere seed crystals.

[0059] Scanning electron microscope (SEM) images of the lanthanum-loaded fluorite seed spheres prepared in Example 2 before and after fluorine removal are shown below. Figure 2 As shown in the figures, (a), (b), and (c) are scanning electron microscope (SEM) images of the lanthanum-loaded fluorite spherical seeds prepared in Example 2 before defluorination; (d), (e), and (f) are the corresponding SEM images after seed-induced defluorination. It can be seen from the figures that the particle size change before and after the reaction is not significant, indicating that compared with the CaF2 raw material, the purity change after defluorination in Example 2 is not significant. The above results show that the recovered calcium fluoride from the lanthanum-loaded fluorite spherical seeds still has high purity after induced defluorination.

[0060] XRD patterns of calcium fluoride raw material, AR calcium fluoride, and fluorite spheroid seed crystals prepared in Examples 1-3 and Comparative Examples 1-2 are shown below. Figure 3As shown, similar to AR CaF2, the raw material CaF2 and the fluorite seed spheres prepared in Comparative Examples 1-2 all exhibit peaks corresponding to CaF2 in PDF#35-0816 at 28.2°, 47°, 55.7°, 68.6°, 75.8°, and 87.3°. This result indicates that the fluorite seed spheres were successfully prepared. However, as the lanthanum loading gradually increased, the characteristic peaks of CaF2 in the lanthanum-loaded fluorite seed spheres prepared in Examples 1-3 gradually weakened, while the characteristic peaks of LaF3 began to appear. This result further confirms that lanthanum has been successfully loaded onto the fluorite seed spheres.

[0061] The purity comparison chart of calcium fluoride raw material and calcium fluoride recovered in Examples 1-3 and Comparative Examples 1-2 is shown in the figure below. Figure 4 As shown, compared with CaF2 raw material, the purity of calcium fluoride after defluorination in Examples 1-3 and Comparative Examples 1-2 did not decrease significantly. Combined with... Figure 2 and 4 It can be seen that the product obtained after the induced crystallization reaction of lanthanum-loaded fluorite seed spheres is mainly calcium fluoride crystals.

[0062] The effects of different hydraulic retention times on fluoride ion treatment in wastewater in Examples 1-3 and Comparative Examples 1-3 are as follows: Figure 5 And as shown in the table below:

[0063]

[0064] Depend on Figure 5 As shown in the table above, compared with Comparative Example 3, the fluoride removal rate of Comparative Examples 1-2 using fluorite seed spheres was significantly improved. The fluoride removal rate of Comparative Example 2 was above 90%. Furthermore, the fluoride removal rate of fluorite seed spheres loaded with lanthanum in Examples 1-3 was significantly improved, reaching a maximum of 96.99%.

Claims

1. A method for preparing lanthanum-loaded fluorite spheroid seed crystals, characterized in that... Includes the following steps: (1) Sodium silicate and polyacrylamide are mixed and ultrasonically dispersed in an aqueous solution to obtain a composite adhesive; the mass ratio of sodium silicate to polyacrylamide is 0.5~1.2:

1. After the sodium silicate and polyacrylamide are ultrasonically dispersed in the aqueous solution, the pH is adjusted to 5.0~7.

0. (2) Mix calcium fluoride powder with composite binder evenly. The content of sodium silicate and polyacrylamide in the mixture is 3-5 wt%, and the water content of the mixture is 10-20%. Put the mixture into a granulator for granulation. The granulation steps are as follows: stir calcium fluoride powder and composite binder into a gypsum-like state and then put it into a shot rubbing machine to generate uniformly sized particles. Polish and grind the particles into spherical particles with a particle size of 0.6-1.2 cm. Take them out and dry them to obtain fluorite ball particles. (3) The obtained fluorite sphere particles are soaked in a lanthanum solution and then roasted to obtain lanthanum-loaded fluorite sphere seed crystals; the lanthanum solution is a lanthanum nitrate or lanthanum chloride solution with a concentration of 0.1~0.5 mol / L; the specific roasting steps are as follows: the roasting temperature is 200~400℃ and the roasting time is 2~5h.

2. The method for preparing lanthanum-loaded fluorite spheroids according to claim 1, characterized in that: In step (2), the calcium fluoride powder comes from the recycled products of photovoltaic wastewater, and the purity of calcium fluoride is above 92%.

3. The method for preparing lanthanum-loaded fluorite spheroids according to claim 1, characterized in that: In step (2), the particles are air-cooled in cold air at 20~30℃ for 2~4 hours and then dried; the drying steps are as follows: place them in an electric heating blower dryer and dry at 40~60℃ for 8~12 hours.

4. The use of the lanthanum-loaded fluorite seed spheres prepared by the method of claim 1 in the treatment of fluoride-containing wastewater.

5. A method for treating fluoride-containing wastewater using lanthanum-loaded fluorite seed spheroids prepared by the method described in claim 1, characterized in that: Lanthanum-loaded fluorite seed spheres were filled into PVC pipes. Fluorine-containing wastewater and calcium chloride solution were slowly injected from both ends of the bottom of the PVC pipes. The mixed solution submerged the fluorite seed spheres. After standing, the calcium fluoride in the mixed solution crystallized on the surface of the fluorite seed spheres. After the treatment was completed, the treatment solution was discharged. The fluoride ion removal rate in the treatment solution was greater than 92%.

6. The method for treating fluoride-containing wastewater using lanthanum-supported fluorite seed spheroids according to claim 5, characterized in that: The PVC pipe has an inner diameter of 40~42mm and a height of 48~52cm. The amount of lanthanum-loaded fluorite sphere seed crystals inside the PVC pipe is 300~1200g, and the filling height is 20~50cm.

7. The method for treating fluoride-containing wastewater using lanthanum-supported fluorite seed spheroids according to claim 5, characterized in that: The concentration of fluoride ions in the fluoride-containing wastewater is 5~20 mg / L, and the molar ratio of fluoride ions to calcium chloride in the fluoride-containing wastewater is 1:0.5~0.6; the influent flow rate of the fluoride-containing wastewater and calcium chloride solution is 25~35 mL / min; during the static treatment, the temperature is kept constant at 10~28℃, and the treatment time is 20~60 min.

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