A method for recovering fluoride ions from wastewater

Abstract

This invention relates to the field of wastewater treatment technology and proposes a method for recovering fluoride ions from wastewater, comprising the following steps: S1, adjusting the pH of the wastewater to 4-6 to obtain pretreated wastewater; S2, adding a composite polyaluminum sulfate solution to the pretreated wastewater, stirring, reacting, and filtering to obtain a solid mixture and the reacted wastewater; S3, adding the solid mixture to an alkaline solution, stirring, and filtering to obtain an alkaline-washed solid mixture; S4, adding the alkaline-washed solid mixture to an acidic solution, stirring, filtering, and washing to obtain fluoride ion recovered material; in step S2, the raw materials of the composite polyaluminum sulfate solution include polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol. This technical solution solves the problems of poor removal and recovery of fluoride ions in wastewater in related technologies.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for recovering fluoride ions from wastewater. Background Technology

[0002] Fluorine is an essential trace element for the human body, and intake within a certain range can be beneficial to human health and activity. In biology, a certain amount of fluoride ions can enhance the activity of osteoblasts, playing an important role in the formation and structure of bones and teeth; fluoride ions also have antibacterial, anti-enzyme, and anti-acid effects, improving the body's resistance to tooth decay. In medicine, fluoride ions are often used in drinking water or pharmaceuticals to supplement the body's fluoride levels, helping to prevent diseases such as osteoporosis. In industry, fluoride ions can be used in the synthesis of foaming agents, fluoropolymers, and fluorinated fine chemicals. However, excessive fluoride ions can harm human health and even damage the environment and ecosystem. Long-term exposure to high-concentration fluoride wastewater can lead to fluorosis, causing varying degrees of damage to various organs, and in severe cases, even paralysis. High fluoride ion concentrations can also cause plant necrosis, affecting normal plant growth and development, and can harm soil and water bodies, disrupting ecological balance. Therefore, the efficient treatment of fluoride ions in wastewater to meet discharge standards and the effective recovery of fluoride ions are of paramount importance for protecting human health and promoting green production and sustainable development.

[0003] Traditional methods for treating and recovering fluoride ions from fluoride-containing wastewater, often employing calcium salt precipitation as the main process, typically result in significant waste of chemical reagents during fluoride ion separation and recovery. Furthermore, these methods are energy-intensive, complex, and difficult to implement efficiently, making it challenging to achieve effective removal and recovery of fluoride ions from wastewater. Therefore, proposing a new method for fluoride ion recovery from wastewater is crucial for addressing the technical challenges of efficiently removing and effectively recovering fluoride ions from wastewater. Summary of the Invention

[0004] This invention proposes a method for recovering fluoride ions from wastewater, which solves the problems of poor removal and recovery of fluoride ions in wastewater in related technologies.

[0005] The technical solution of the present invention is as follows:

[0006] This invention proposes a method for recovering fluoride ions from wastewater, comprising the following steps:

[0007] S1. Adjust the pH of the wastewater to 4-6 to obtain pretreated wastewater;

[0008] S2. Add composite polyaluminum sulfate solution to the pretreated wastewater, stir, react, and filter to obtain a solid mixture and the reacted wastewater;

[0009] S3. Add the solid mixture to the alkaline solution, stir, filter, and obtain the alkaline-washed solid mixture;

[0010] S4. Add the solid mixture after alkaline washing to an acid solution, stir, filter, and wash to obtain fluoride ion recovery product;

[0011] In step S2, the raw materials for the composite polyaluminum sulfate solution include polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol.

[0012] As a further technical solution, the weight ratio of the polyaluminum sulfate, polyquaternary ammonium salt and polyethylene glycol is 8~18:1:1.

[0013] When the weight ratio of polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol is 8~18:1:1, the removal and recovery efficiency of fluoride ions in wastewater can be improved.

[0014] As a further technical solution, the polyquaternary ammonium salt includes polyquaternary ammonium salt-10 and polyquaternary ammonium salt-37; the weight ratio of polyquaternary ammonium salt-10 to polyquaternary ammonium salt-37 is 1~3:1.

[0015] When polyquaternary ammonium salts include polyquaternary ammonium salt-10 and polyquaternary ammonium salt-37, the removal and recovery of fluoride ions in wastewater can be further improved by using the two polyquaternary ammonium salts together. In addition, when the weight ratio of polyquaternary ammonium salt-10 to polyquaternary ammonium salt-37 is 1~3:1, the removal and recovery of fluoride ions in wastewater can be further improved.

[0016] As a further technical solution, the preparation method of the composite polyaluminum sulfate solution includes the following steps:

[0017] A1. Add polyquaternium salt and polyethylene glycol to water and stir to obtain a mixed solution;

[0018] A2. Add the polyaluminum sulfate to the mixed solution and stir to obtain the composite polyaluminum sulfate solution.

[0019] As a further technical solution, in step A2, the mass fraction of the composite polyaluminum sulfate solution is 5%~10%.

[0020] As a further technical solution, in step A2, the temperature during stirring is 50~60℃.

[0021] As a further technical solution, in step S2, the reaction time is 0.5~1h.

[0022] As a further technical solution, in step S2, the volume ratio of the composite polyaluminum sulfate solution to the pretreated wastewater is 30~60:1000.

[0023] As a further technical solution, in step S3, the amount of alkaline solution added is 7 to 10 times the weight of the solid mixture; the stirring time is 0.5 to 1 hour.

[0024] As a further technical solution, in step S4, the amount of acid solution added is 7 to 10 times the weight of the solid mixture after alkali washing; the stirring time is 0.5 to 1 hour.

[0025] As a further technical solution, in step S3, the alkaline solution is a sodium hydroxide solution with a mass fraction of 6% to 10%; in step S4, the acid solution is a hydrochloric acid solution with a mass fraction of 6% to 10%.

[0026] As a further technical solution, in step S1, the fluoride ion content in the wastewater is ≥210mg / L.

[0027] The working principle and beneficial effects of this invention are as follows:

[0028] In this invention, a composite polyaluminum sulfate solution is used to react with fluoride ions in wastewater. The raw materials of the composite polyaluminum sulfate solution include polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol. By using polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol together, fluoride ions in wastewater can be effectively removed, thereby improving the removal and recovery efficiency of fluoride ions in wastewater. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] In the following examples and comparative examples, the polyaluminum sulfate has a mesh size of 120; polyquaternium-10 has a model number of 3000KC; polyquaternium-37 has a model number of D1UL; polyquaternium-7 has a model number of M550; polyquaternium-22 has a model number of M-22; and polyethylene glycol has a model number of PEG400.

[0031] Example 1

[0032] A method for recovering fluoride ions from wastewater includes the following steps:

[0033] S1. Adjust the pH of the wastewater with a fluoride ion content of 250 mg / L to 5 to obtain the pretreated wastewater;

[0034] S2. Add 30 mL of 10% (w / w) composite polyaluminum sulfate solution to 1000 mL of pretreated wastewater, stir, react for 1 h, filter, and obtain a solid mixture and the reacted wastewater; wherein, the fluoride ion content in the reacted wastewater is 4.52 mg / L;

[0035] S3. Add the solid mixture to an 8% sodium hydroxide solution, the amount of sodium hydroxide solution added is 8 times the weight of the solid mixture, stir for 1 hour, filter, and obtain the alkali-washed solid mixture.

[0036] S4. Add the alkaline-washed solid mixture to an 8% hydrochloric acid solution, the amount of hydrochloric acid solution added being 8 times the weight of the alkaline-washed solid mixture. Stir for 1 hour, filter, and wash to obtain fluoride ion recovery product; wherein, the fluoride ion recovery product has a fluoride content of 58.15%;

[0037] In step S2, the raw materials for the composite polyaluminum sulfate solution include 6 parts polyaluminum sulfate, 2 parts polyquaternium salt and 2 parts polyethylene glycol; the polyquaternium salt is polyquaternium salt-10;

[0038] The preparation method of the composite polyaluminum sulfate solution includes the following steps:

[0039] A1. Add 2 parts of polyquaternium salt and 2 parts of polyethylene glycol to water, stir, and obtain a mixed solution;

[0040] A2. Add 6 parts of polyaluminum sulfate to the mixed solution and stir at 50°C to obtain a 10% (w / w) composite polyaluminum sulfate solution.

[0041] Example 2

[0042] A method for recovering fluoride ions from wastewater includes the following steps:

[0043] S1. Adjust the pH of the wastewater with a fluoride ion content of 300 mg / L to 5 to obtain the pretreated wastewater;

[0044] S2. Add 45 mL of 10% (w / w) composite polyaluminum sulfate solution to 1000 mL of pretreated wastewater, stir, react for 1 h, filter, and obtain a solid mixture and the reacted wastewater; wherein, the fluoride ion content in the reacted wastewater is 4.28 mg / L;

[0045] S3. Add the solid mixture to an 8% sodium hydroxide solution, the amount of sodium hydroxide solution added is 8 times the weight of the solid mixture, stir for 1 hour, filter, and obtain the alkali-washed solid mixture.

[0046] S4. Add the alkaline-washed solid mixture to an 8% hydrochloric acid solution, the amount of hydrochloric acid solution added being 8 times the weight of the alkaline-washed solid mixture. Stir for 1 hour, filter, and wash to obtain fluoride ion recovery product; wherein, the fluoride ion recovery product has a fluoride content of 58.26%;

[0047] In step S2, the raw materials for the composite polyaluminum sulfate solution include 9 parts polyaluminum sulfate, 3 parts polyquaternium salt, and 3 parts polyethylene glycol; the polyquaternium salt is polyquaternium salt-10.

[0048] The preparation method of the composite polyaluminum sulfate solution includes the following steps:

[0049] A1. Add 3 parts of polyquaternary ammonium salt and 3 parts of polyethylene glycol to water, stir, and obtain a mixed solution;

[0050] A2. Add 9 parts of polyaluminum sulfate to the mixed solution and stir at 50°C to obtain a 10% (w / w) composite polyaluminum sulfate solution.

[0051] Example 3

[0052] A method for recovering fluoride ions from wastewater includes the following steps:

[0053] S1. Adjust the pH of the wastewater with a fluoride ion content of 300 mg / L to 5 to obtain the pretreated wastewater;

[0054] S2. Add 60 mL of 10% (w / w) composite polyaluminum sulfate solution to 1000 mL of pretreated wastewater, stir, react for 1 h, filter, and obtain a solid mixture and the wastewater after reaction; wherein, the fluoride ion content in the wastewater after reaction is 4.02 mg / L;

[0055] S3. Add the solid mixture to an 8% sodium hydroxide solution, the amount of sodium hydroxide solution added is 8 times the weight of the solid mixture, stir for 1 hour, filter, and obtain the alkali-washed solid mixture.

[0056] S4. Add the alkaline-washed solid mixture to an 8% hydrochloric acid solution, the amount of hydrochloric acid solution added being 8 times the weight of the alkaline-washed solid mixture. Stir for 1 hour, filter, and wash to obtain fluoride ion recovery product; wherein, the fluoride ion recovery product has a fluoride content of 58.37%;

[0057] In step S2, the raw materials for the composite polyaluminum sulfate solution include 12 parts polyaluminum sulfate, 4 parts polyquaternium salt and 4 parts polyethylene glycol; the polyquaternium salt is polyquaternium salt-10;

[0058] The preparation method of the composite polyaluminum sulfate solution includes the following steps:

[0059] A1. Add 4 parts of polyquaternary ammonium salt and 4 parts of polyethylene glycol to water, stir, and obtain a mixed solution;

[0060] A2. Add 12 parts of polyaluminum sulfate to the mixed solution and stir at 50°C to obtain a 10% (w / w) composite polyaluminum sulfate solution.

[0061] Example 4

[0062] The only difference between this embodiment and embodiment 3 is that, in step S2, the raw materials for the composite polyaluminum sulfate solution include 19 parts of polyaluminum sulfate, 0.5 parts of polyquaternium salt and 0.5 parts of polyethylene glycol; the polyquaternium salt is polyquaternium salt-10; wherein, the fluoride ion content in the wastewater after the reaction is 3.93 mg / L; and the fluoride content in the fluoride ion recovery product is 58.40%.

[0063] Example 5

[0064] The only difference between this embodiment and embodiment 3 is that, in step S2, the raw materials for the composite polyaluminum sulfate solution include 18 parts of polyaluminum sulfate, 1 part of polyquaternium salt and 1 part of polyethylene glycol; the polyquaternium salt is polyquaternium salt-10; wherein, the fluoride ion content in the wastewater after the reaction is 3.67 mg / L; and the fluoride content in the fluoride ion recovery product is 58.62%.

[0065] Example 6

[0066] The only difference between this embodiment and embodiment 3 is that, in step S2, the raw materials for the composite polyaluminum sulfate solution include 16 parts polyaluminum sulfate, 2 parts polyquaternium salt and 2 parts polyethylene glycol; the polyquaternium salt is polyquaternium salt-10; wherein, the fluoride ion content in the wastewater after the reaction is 3.60 mg / L; and the fluoride content in the fluoride ion recovery product is 58.66%.

[0067] Example 7

[0068] The only difference between this embodiment and Example 6 is that the polyquaternium salt includes 0.5 parts of polyquaternium salt-10 and 1.5 parts of polyquaternium salt-37; wherein, the fluoride ion content in the wastewater after the reaction is 3.38 mg / L; and the fluoride content in the fluoride ion recovery product is 58.89%.

[0069] Example 8

[0070] The only difference between this embodiment and Example 6 is that the polyquaternium salt includes 1.6 parts of polyquaternium salt-10 and 0.4 parts of polyquaternium salt-37; wherein, the fluoride ion content in the wastewater after the reaction is 3.43 mg / L; and the fluoride content in the fluoride ion recovery product is 58.86%.

[0071] Example 9

[0072] The only difference between this embodiment and Embodiment 6 is that the polyquaternium salt includes 1 part polyquaternium salt-10 and 1 part polyquaternium salt-37; wherein, the fluoride ion content in the wastewater after the reaction is 3.21 mg / L; and the fluoride content in the fluoride ion recovery product is 59.04%.

[0073] Example 10

[0074] The only difference between this embodiment and Example 6 is that the polyquaternium salt includes 1.5 parts of polyquaternium salt-10 and 0.5 parts of polyquaternium salt-37; wherein, the fluoride ion content in the wastewater after the reaction is 3.15 mg / L; and the fluoride content in the fluoride ion recovery product is 59.12%.

[0075] Example 11

[0076] The only difference between this embodiment and Example 10 is that the polyquaternium salt includes 1.5 parts of polyquaternium salt-10 and 0.5 parts of polyquaternium salt-7; wherein, the fluoride ion content in the wastewater after the reaction is 3.64 mg / L; and the fluoride content in the fluoride ion recovery product is 58.62%.

[0077] Example 12

[0078] The only difference between this embodiment and Example 10 is that the polyquaternium salt includes 1.5 parts of polyquaternium salt-10 and 0.5 parts of polyquaternium salt-22; wherein, the fluoride ion content in the wastewater after the reaction is 3.58 mg / L; and the fluoride content in the fluoride ion recovery product is 58.72%.

[0079] Comparative Example 1

[0080] The only difference between this comparative example and Example 1 is that, in step S2, the raw materials for the composite polyaluminum sulfate solution include 8 parts of polyaluminum sulfate and 2 parts of polyquaternium salt; the polyquaternium salt is polyquaternium salt-10; the fluoride ion content in the wastewater after the reaction is 5.11 mg / L; and the fluoride content in the fluoride ion recovery product is 53.42%.

[0081] Comparative Example 2

[0082] The only difference between this comparative example and Example 1 is that, in step S2, the raw materials for the composite polyaluminum sulfate solution include 8 parts polyaluminum sulfate and 2 parts polyethylene glycol; wherein, the fluoride ion content in the wastewater after the reaction is 5.23 mg / L; and the fluoride content in the fluoride ion recovery product is 52.86%.

[0083] Comparative Example 3

[0084] The only difference between this comparative example and Example 1 is that, in step S2, the raw material for the composite polyaluminum sulfate solution includes only 10 parts of polyaluminum sulfate; the fluoride ion content in the wastewater after the reaction is 5.44 mg / L; and the fluoride content in the fluoride ion recovery product is 51.21%.

[0085] Compared with Comparative Examples 1-3, the fluoride ion content in the wastewater after the reaction in Example 1 was significantly reduced and the fluoride content in the fluoride ion recovery product was significantly increased. This indicates that when the raw materials of the composite polyaluminum sulfate solution include polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol, the combined use of polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol can improve the removal and recovery efficiency of fluoride ions in wastewater.

[0086] Compared to Examples 3-4, the fluoride ion content in the wastewater after the reaction in Examples 5-6 decreased, while the fluoride content in the fluoride ion recovery product increased, indicating that a weight ratio of polyaluminum sulfate, polyquaternium salt, and polyethylene glycol of 8-18:1:1 can improve the removal and recovery efficiency of fluoride ions in wastewater. Compared to Examples 6 and 11-12, the fluoride ion content in the wastewater after the reaction in Examples 7-10 decreased, while the fluoride content in the fluoride ion recovery product increased, indicating that when the polyquaternium salt includes polyquaternium salt-10 and polyquaternium salt-37, the removal and recovery efficiency of fluoride ions in wastewater can be further improved. Furthermore, compared to Examples 7-8, the fluoride ion content in the wastewater after the reaction in Examples 9-10 decreased, while the fluoride content in the fluoride ion recovery product increased, indicating that a weight ratio of polyquaternium salt-10 and polyquaternium salt-37 of 1-3:1 can further improve the removal and recovery efficiency of fluoride ions in wastewater.

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering fluoride ions from wastewater, characterized in that, Includes the following steps: S1. Adjust the pH of the wastewater to 4-6 to obtain pretreated wastewater; S2. Add composite polyaluminum sulfate solution to the pretreated wastewater, stir, react, and filter to obtain a solid mixture and the reacted wastewater; S3. Add the solid mixture to the alkaline solution, stir, filter, and obtain the alkaline-washed solid mixture; S4. Add the solid mixture after alkali washing to an acid solution, stir, filter, and wash to obtain fluoride ion recovery product; In step S2, the raw materials for the composite polyaluminum sulfate solution include polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol; The weight ratio of the polyaluminum sulfate, polyquaternary ammonium salt, and polyethylene glycol is 8~18:1:1; The polyquaternium salt includes polyquaternium salts 10 and polyquaternium salts 37.

2. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, The polyquaternium salt 10 and polyquaternium salts The weight ratio of 37 is 1~3:

1.

3. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, The preparation method of the composite polyaluminum sulfate solution includes the following steps: A1. Add polyquaternium salt and polyethylene glycol to water and stir to obtain a mixed solution; A2. Add the polyaluminum sulfate to the mixed solution and stir to obtain the composite polyaluminum sulfate solution.

4. The method for recovering fluoride ions from wastewater according to claim 3, characterized in that, In step A2, the mass fraction of the composite polyaluminum sulfate solution is 5% to 10%.

5. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, In step S2, the volume ratio of the composite polyaluminum sulfate solution to the pretreated wastewater is 30~60:1000.

6. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, In step S3, the amount of alkaline solution added is 7 to 10 times the weight of the solid mixture; the stirring time is 0.5 to 1 hour.

7. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, In step S4, the amount of acid solution added is 7 to 10 times the weight of the solid mixture after alkali washing; the stirring time is 0.5 to 1 hour.

8. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, In step S3, the alkaline solution is a sodium hydroxide solution with a mass fraction of 6% to 10%; in step S4, the acid solution is a hydrochloric acid solution with a mass fraction of 6% to 10%.

9. The method for recovering fluoride ions from wastewater according to claim 1, characterized in that, In step S1, the fluoride ion content in the wastewater is ≥210 mg / L.