A method for removing SiO2 and P from fluoride-containing sludge

Abstract

The present application belongs to the technical field of solid waste treatment, and particularly relates to a method for removing SiO2 and P from fluorine-containing sludge. The method comprises the following processing steps: (1) the fluorine-containing sludge is preliminarily crushed, and large-particle impurities are removed by screening to obtain uniformly refined sludge raw materials; (2) the sludge raw materials obtained in step (1) are mixed uniformly with an alkaline control agent solution, and then added into a hydrothermal reaction kettle, which is sealed and subjected to hydrothermal reaction under the conditions of a temperature of 80-200 DEG C and a pressure of 0.5-2 MPa, after the reaction is completed, the reaction product is cooled to room temperature, and solid-liquid separation is performed, and the obtained solid phase is fluorine-containing sludge from which SiO2 and P are removed. The method uses a cheap alkaline reagent as a control agent of the fluorine-containing sludge, can effectively promote the dissolution reaction of SiO2 and phosphate, avoids using strong acid, reduces the generation of corrosive waste liquid, and has minimal impact on fluorine components (such as CaF2). The method has the advantages of high efficiency, low cost and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment technology, specifically relating to a method for removing SiO2 and P from fluoride-containing sludge. Background Technology

[0002] Fluorine-containing sludge is a common waste product in industries such as metallurgy and chemicals. Its high silica (SiO2) content severely hinders the purification and industrial application of valuable resources like calcium fluoride (CaF2). Current technologies exhibit low SiO2 removal efficiency from fluorine-containing sludge, leading to substandard final product purity or increased processing costs. Furthermore, the presence of phosphorus (primarily in the form of phosphates) in fluorine-containing sludge also affects subsequent treatment and the purification of valuable resources like calcium fluoride, especially in metallurgical and chemical applications where phosphorus content is strictly limited. Currently, effective phosphorus removal remains a key challenge in the industrial treatment of fluorine-containing sludge.

[0003] Existing methods for removing SiO2 from fluoride-containing sludge include: acid dissolution: separating SiO2 by adding strong acids. Disadvantages include high acid consumption, strong corrosiveness, and serious impact on equipment and the environment. Flotation: separating SiO2 using flotation reagents. Disadvantages include high reagent costs and potential residues affecting the purity of subsequent products. Physical separation: separating SiO2 using physical methods such as sieving and sedimentation. Disadvantages include low removal efficiency for fine SiO2 particles.

[0004] Existing methods for removing phosphorus (P) from fluoride-containing sludge include: acid dissolution: dissolving phosphates by adding strong acids (such as HCl or H₂SO₄). Disadvantages include high acid consumption, strong corrosiveness, unsafe operation, and complex wastewater treatment, increasing environmental risks. Precipitation: adding calcium salts (such as CaCl₂) to precipitate phosphates. Disadvantages include incomplete phosphate precipitation, strict requirements for operating conditions, and potential competition with CaF₂ products, reducing calcium fluoride extraction efficiency. Adsorption: using adsorbent materials (such as activated carbon or polymers) to adsorb phosphorus. Disadvantages include limited adsorption capacity, high material costs, and unsuitability for large-scale applications.

[0005] The methods described above generally suffer from low efficiency, high cost, or environmental unfriendliness, and cannot yet meet the needs of large-scale industrial applications. Therefore, there is a need to develop a novel, efficient, economical, and environmentally friendly method for removing SiO2 and P from fluoride-containing sludge to meet industrial treatment requirements. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, the present invention aims to provide a method for removing SiO2 and P from fluoride-containing sludge. This method is based on a hydrothermal reaction regulated by an alkaline solution, which converts SiO2 and phosphate into soluble compounds that separate from the solid phase. By combining appropriate additives and optimized hydrothermal conditions, this method can efficiently remove SiO2 and P without damaging the CaF2 component in the fluoride-containing sludge.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0009] (1) The fluoride-containing sludge is initially crushed and screened to remove large particles of impurities, so as to obtain uniform and fine sludge raw material.

[0010] (2) The sludge raw material obtained in step (1) is mixed evenly with the alkaline regulator solution and then added to the hydrothermal reactor. After sealing, the hydrothermal reaction is carried out at a temperature of 80-200℃ and a pressure of 0.5-2MPa. After the reaction is completed, the reaction product is cooled to room temperature and the solid and liquid are separated. The obtained solid phase is fluorine-containing sludge with SiO2 and P removed.

[0011] Furthermore, the moisture content of the fluoride-containing sludge in step (1) is 5-10%.

[0012] Furthermore, the solid phase components of the fluoride-containing sludge in step (1) include calcium fluoride (CaF2), silicon dioxide (SiO2) and phosphate (such as Ca3(PO4)2).

[0013] More preferably, the fluorinated sludge contains 50-70% calcium fluoride, 10-20% silica, and 5-15% phosphate by mass.

[0014] Furthermore, the sieving in step (1) is performed using an 80-120 mesh sieve.

[0015] Furthermore, the alkaline regulator solution mentioned in step (2) is a sodium hydroxide (NaOH) solution, sodium carbonate (Na2CO3) solution, or potassium hydroxide (KOH) solution with a concentration of 10-30 wt.%.

[0016] More preferably, the amount of the alkaline regulator solution is 10-30% of the mass of the sludge raw material.

[0017] Furthermore, the hydrothermal reaction time in step (2) is 8 to 72 hours.

[0018] Furthermore, the solid-liquid separation in step (2) is carried out using a centrifuge, plate and frame filter press or vacuum filter.

[0019] More preferably, the centrifuge is used for solid-liquid separation at a speed of 3000-5000 rpm for 10-30 min; the plate and frame filter press is used for solid-liquid separation at a pressure of 0.1-0.5 MPa for 10-30 min; and the vacuum filter is used for solid-liquid separation at a vacuum degree of 0.01-0.1 MPa for 10-30 min.

[0020] The principle of this invention is as follows: Fluorine-containing sludge raw material reacts with an alkaline regulator solution under hydrothermal conditions. Under high temperature and pressure, the alkaline regulator reacts with silica and phosphates (such as Ca3(PO4)2) in the fluorine-containing sludge, generating soluble silicates (Na2SiO3) or phosphates (such as Na3PO4) that are transferred to the liquid phase. Simultaneously, this does not affect the CaF2 component in the solid phase, thereby achieving the removal of SiO2 and P impurities and the enrichment of CaF2 in the fluorine-containing sludge. The specific reaction formula is as follows:

[0021] SiO2(s)+2NaOH(aq)=Na2SiO3(aq)+H2O(aq);

[0022] SiO2(s)+2KOH(aq)=K2SiO3(aq)+H2O(aq);

[0023] SiO2(s)+Na2CO3(aq)=Na2SiO3(aq)+CO2(g);

[0024] Ca3(PO4)2(s)+6NaOH(aq)=2Na3PO4(aq)+3Ca(OH)2(aq);

[0025] Ca3(PO4)2(s)+6KOH(aq)=2K3PO4(aq)+3Ca(OH)2(aq).

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) The method of the present invention uses inexpensive alkaline reagents as regulators for fluoride-containing sludge, which can effectively promote the dissolution reaction of SiO2 and phosphate, avoid the use of strong acids, reduce the generation of corrosive waste liquid, and have minimal impact on fluoride-containing components (such as CaF2). It has the advantages of high efficiency, low cost and environmental protection.

[0028] (2) The method of the present invention can be seamlessly integrated with the existing fluoride-containing sludge treatment process, which is suitable for industrial application and has the advantage of good industrial compatibility. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0030] Example 1

[0031] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0032] (1) The fluorine-containing sludge (calcium fluoride (CaF2) 63.15%, silicon dioxide (SiO2) 14.72% and phosphate (Ca3(PO4)2) 13.13%, with a moisture content of 9%) was initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0033] (2) The sludge raw material obtained in step (1) is mixed evenly with a 10wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 100℃ and 1MPa pressure for 48h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0034] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 1 (SiO2 content was determined according to GB / T5195.8-2006 "Determination of Silica Content in Fluorite"; phosphorus content was determined according to GB / T 5195.6-2017 "Determination of Phosphorus Content in Fluorite" by spectrophotometry); the calcium fluoride loss rate was 6% (CaF2 content was determined according to GB / T 5195.1-2017 "Determination of Calcium Fluoride Content in Fluorite" by EDTA titration and distillation-potential titration, and the calcium fluoride loss rate was calculated by comparing the calcium fluoride content before and after treatment).

[0035] Table 1

[0036] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 93.27％ 3.68％ 1.70％

[0037] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0038] Example 2

[0039] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0040] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0041] (2) The sludge raw material obtained in step (1) is mixed evenly with a 15wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 100℃ and 1MPa pressure for 48h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0042] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 2, and the calcium fluoride loss rate is 6%.

[0043] Table 2

[0044] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 95.71％ 2.21％ 0.92％

[0045] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0046] Example 3

[0047] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0048] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0049] (2) The sludge raw material obtained in step (1) is mixed evenly with a 20wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 100℃ and 1MPa pressure for 48h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0050] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 3, and the calcium fluoride loss rate is 5%.

[0051] Table 3

[0052] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 96.33％ 1.47％ 0.66％

[0053] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0054] Example 4

[0055] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0056] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0057] (2) The sludge raw material obtained in step (1) is mixed evenly with a 25wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 100℃ and 1MPa pressure for 48h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0058] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 4, and the calcium fluoride loss rate is 7%.

[0059] Table 4

[0060] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 97.63％ 0.74％ 0.39％

[0061] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0062] Example 5

[0063] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0064] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0065] (2) The sludge raw material obtained in step (1) is mixed evenly with a 20wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 120℃ and 1.2MPa for 48h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0066] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 5, and the calcium fluoride loss rate is 8%.

[0067] Table 5

[0068] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 97.88％ 0.44％ 0.26％

[0069] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0070] Example 6

[0071] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0072] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0073] (2) The sludge raw material obtained in step (1) is mixed evenly with a 20wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 100℃ and 1MPa pressure for 36h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0074] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 6, and the calcium fluoride loss rate is 5%.

[0075] Table 6

[0076] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 95.11％ 1.77％ 1.44％

[0077] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0078] Example 7

[0079] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0080] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0081] (2) The sludge raw material obtained in step (1) is mixed evenly with a 20wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 100℃ and 1MPa pressure for 72h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2MPa and the time is 20min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0082] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 7, and the calcium fluoride loss rate is 6%.

[0083] Table 7

[0084] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 97.62％ 0.59％ 0.26％

[0085] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0086] Example 8

[0087] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0088] (1) The fluoride-containing sludge is initially crushed and screened through 80 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0089] (2) The sludge raw material obtained in step (1) is mixed evenly with a 20wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 10% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 160℃ and 1.5MPa for 12 hours. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a centrifuge. The centrifuge speed is 4000rpm and the time is 30min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0090] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 8, and the calcium fluoride loss rate is 8%.

[0091] Table 8

[0092] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2 <!-- 5 -->]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 96.87％ 1.47％ 1.05％

[0093] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0094] Example 9

[0095] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0096] (1) The fluoride-containing sludge is initially crushed and screened through 120 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0097] (2) The sludge raw material obtained in step (1) is mixed evenly with a 20wt% NaOH solution and then added to a hydrothermal reactor. The amount of NaOH solution is 30% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at 120℃ and 1.2MPa for 15h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a vacuum filter. The vacuum degree of solid-liquid separation is 0.1MPa and the time is 10min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0098] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 9, and the calcium fluoride loss rate is 7%.

[0099] Table 9

[0100] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 96.19％ 1.18％ 1.05％

[0101] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0102] Example 10

[0103] A method for removing SiO2 and P from fluoride-containing sludge includes the following treatment steps:

[0104] (1) The fluoride-containing sludge is initially crushed and screened through 100 mesh to remove large particulate impurities and obtain uniform and fine sludge raw material.

[0105] (2) The sludge raw material obtained in step (1) is mixed evenly with a KOH solution with a concentration of 20 wt% and then added to a hydrothermal reactor. The amount of KOH solution is 20% of the mass of the sludge raw material. After sealing, the hydrothermal reaction is carried out at a temperature of 150℃ and a pressure of 1.5 MPa for 10 h. After the reaction is completed, the reaction product is cooled to room temperature and solid-liquid separation is carried out using a plate and frame filter press. The pressure of solid-liquid separation is 0.2 MPa and the time is 20 min. The solid phase is fluorine-containing sludge with SiO2 and P removed.

[0106] The composition of the fluoride-containing sludge after treatment in this embodiment is shown in Table 10, and the calcium fluoride loss rate is 6%.

[0107] Table 10

[0108] Composition <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Ca3(PO4)2]]> Fluoride-containing sludge (wt.%) 63.15％ 14.72％ 13.13％ Processed product (wt.%) 96.72％ 1.03％ 1.05％

[0109] The results above show that the method of the present invention can effectively remove SiO2 and P impurities and enrich CaF2 in fluoride-containing sludge, and the calcium fluoride loss rate is low.

[0110] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for removing SiO2 and P from fluoride-containing sludge, characterized in that, The processing steps include the following: (1) The fluoride-containing sludge is initially crushed and screened to remove large particles of impurities, so as to obtain a uniform and fine sludge raw material. (2) After the sludge raw material obtained in step (1) is mixed evenly with the alkaline regulator solution, it is added to the hydrothermal reactor. After sealing, the hydrothermal reaction is carried out at a temperature of 80~200℃ and a pressure of 0.5~2MPa. After the reaction is completed, the reaction product is cooled to room temperature and the solid and liquid are separated. The obtained solid phase is fluorine-containing sludge with SiO2 and P removed. The solid phase components of the fluoride-containing sludge in step (1) include calcium fluoride, silicon dioxide and calcium phosphate; The alkaline regulator solution mentioned in step (2) is a sodium hydroxide solution, sodium carbonate solution or potassium hydroxide solution with a concentration of 10~30 wt.%.

2. The method for removing SiO2 and P from fluoride-containing sludge according to claim 1, characterized in that, The fluoride-containing sludge in step (1) has a moisture content of 5-10%.

3. The method for removing SiO2 and P from fluoride-containing sludge according to claim 1, characterized in that, The fluorine-containing sludge contains 50-70% calcium fluoride, 10-20% silicon dioxide, and 5-15% calcium phosphate by mass.

4. The method for removing SiO2 and P from fluoride-containing sludge according to claim 1, characterized in that, The sieving in step (1) is performed using an 80-120 mesh sieve.

5. The method for removing SiO2 and P from fluoride-containing sludge according to claim 1, characterized in that, The amount of alkaline regulator solution used is 10-30% of the mass of the sludge raw material.

6. The method for removing SiO2 and P from fluoride-containing sludge according to claim 1, characterized in that, The hydrothermal reaction time in step (2) is 8~72h.

7. The method for removing SiO2 and P from fluoride-containing sludge according to claim 1, characterized in that, The solid-liquid separation in step (2) is carried out using a centrifuge, plate and frame filter press or vacuum filter.

8. The method for removing SiO2 and P from fluoride-containing sludge according to claim 7, characterized in that, For solid-liquid separation using a centrifuge, the rotation speed is 3000~5000 rpm and the time is 10~30 min; for solid-liquid separation using a plate and frame filter press, the pressure is 0.1~0.5 MPa and the time is 10~30 min; for solid-liquid separation using a vacuum filter, the vacuum degree is 0.01~0.1 MPa and the time is 10~30 min.