A defluorinating agent and a preparation method thereof

Abstract

The application provides a defluorination agent and a preparation method thereof, and belongs to the technical field of water treatment. The defluorination agent is composed of an aluminum salt, a calcium salt and a gelling agent. The molar ratio of the aluminum salt and the calcium salt is 1:1-1:5. The molar ratio of the calcium salt and the gelling agent is 1:1-1:2. The defluorination agent can be prepared through simple ultrasonic treatment, grinding and constant-temperature treatment. The required equipment investment is small, and the preparation is easy to operate. The alum flower is attached to a small amount of organic cross-linked calcium salt particle carrier, so that the volume of the alum flower aggregation can be effectively improved, the settling rate of the alum flower is improved by using the advantage that the density of calcium carbonate is relatively high, and the removal efficiency and effect of the alum flower in a sedimentation tank are significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a defluorination agent and a preparation method thereof. Background Art

[0002] Fluoride is a crucial industrial reagent in numerous fields, including metallurgy, chemicals, pharmaceuticals, semiconductors, and aerospace. However, while its use drives economic development, it also inevitably produces large amounts of fluoridated water. Improper handling of this high fluoride content in water can exacerbate water pollution and even threaten human health.

[0003] Due to factors such as fluoride removal efficiency, cost, and operational process considerations, aluminum sulfate or polyaluminum chloride (PAC) are commonly used as defluoridation agents. When added to water, these agents react fully with fluoride ions, forming complexes and flocs (flocs). After sedimentation and solid-liquid separation, the flocs return the water to discharge standards. However, incomplete floc removal in sedimentation tanks is a common problem in industrial operations. The primary reason is that the flocs are small and loose, making them difficult to settle.

[0004] To address these issues, polyacrylamide is commonly used in industry to aid coagulation of alum flocs, but its effectiveness is easily affected by the water environment. "A Method for Producing Polyaluminum Sulfate from Aluminum Ash" (CN 112142085 A) discloses a defluorination agent and its preparation method. Polyaluminum sulfate is prepared using aluminum ash as an aluminum source, along with polyethylene glycol and cetyltrimethylammonium bromide. The adsorption and bridging properties of polyethylene glycol and cetyltrimethylammonium bromide increase the specific surface area of ​​the flocculant, facilitating colloid adsorption and increasing the size of the alum flocs. However, the preparation of this agent requires the use of a reactor, resulting in a complex process. The raw materials used contain a large amount of organic matter, which can introduce other impurities into the water. "A Fluorine Removal Agent and Its Preparation Method" (CN112340825 A) utilizes the amorphous macromolecular structure of humic acid in combination with zeolite, modified straw cellulose, aluminum sulfate, etc. to produce flocculation properties. The adsorption properties of modified straw cellulose are used to allow the flocculation effect to produce larger alum flocs, which can reduce the sedimentation rate of the flocs after fluorine removal from 35 minutes to 27-29 minutes. However, its raw material composition is complex, and it essentially still uses the gravity of the alum flocs for sedimentation, so the effect is still limited. Summary of the Invention

[0005] The purpose of the present invention is to propose a defluoridation agent and a preparation method. The aluminum salt that produces alum flocs is fixed in advance on the surface of calcium salt particles cross-linked by a small amount of organic matter to prepare the defluoridation agent. When the defluoridation agent is put into water for use, the alum flocs can grow on the cross-linked calcium salt particles as a matrix, thereby increasing the size of the alum flocs and the sedimentation dynamics, and solving the problem of incomplete alum floc removal in the sedimentation tank.

[0006] The technical solution of the present invention is achieved as follows:

[0007] The invention provides a defluorination agent, which consists of aluminum salt, calcium salt and a gelling agent.

[0008] As a further improvement of the present invention, the molar ratio of the aluminum salt to the calcium salt is 1:1-1:5; the molar ratio of the calcium salt to the gelling agent is 1:1-1:2.

[0009] As a further improvement of the present invention, the aluminum salt is selected from one or more of aluminum chloride hexahydrate, aluminum sulfate, and aluminum nitrate.

[0010] As a further improvement of the present invention, the calcium salt is selected from one or more of insoluble inorganic calcium salts such as calcium carbonate, calcium phosphate, and calcium sulfate.

[0011] As a further improvement of the present invention, the gelling agent is selected from one or more of chain organic substances containing carboxyl groups, such as sodium alginate and sodium carboxymethyl cellulose.

[0012] The present invention further protects a preparation method of the above-mentioned defluoridation agent, comprising the following steps: firstly pre-treating the calcium salt by ultrasound, then adding aluminum salt and gelling agent to the treated calcium salt, and finally grinding and mixing uniformly to obtain the defluoridation agent.

[0013] As a further improvement of the present invention, the power of the ultrasonic treatment is 100-500W, and the time is 0.5-1h.

[0014] As a further improvement of the present invention, the milling and mixing method is selected from one or more of ball milling, rod milling, grinding, etc.

[0015] The present invention operates on the principle that ultrasound effectively reduces unavoidable residual contaminants on the surface of calcium salt particles and exposes fresh surfaces. The ultrasonically pretreated calcium salt, aluminum salt, and gelling agent are ground to uniformly distribute the aluminum salt and gelling agent on the surface of the sparingly soluble inorganic calcium salt particles with a large specific surface area. During the addition and use of the agent, flocs formed by the dissolution and hydrolysis of the aluminum salt become entangled on the surface of the calcium salt particles. The chain-like gelling agent, rich in carboxyl groups, can connect multiple calcium salt particles through complexation, thereby enlarging the alum flocs. The weight of the large alum flocs and the gravity of the calcium salt matrix promote the sedimentation and removal of the alum flocs. Furthermore, when the agent is added to water and used, the flocs produced by the aluminum salt react with fluoride ions. The strong interaction between the fluoride ions and the calcium ions compacts the alum flocs, reducing the amount of water carried, further improving the sedimentation efficiency and helping to reduce the moisture content of the alum flocs and defluoridation sludge.

[0016] The present invention has the following beneficial effects:

[0017] 1. The defluorination agent of the present invention can be prepared by simple ultrasonic, grinding and constant temperature processes, requiring little equipment investment and is easy to operate and prepare.

[0018] 2. The present invention attaches alum flocs to a calcium salt particle carrier cross-linked with a small amount of organic matter, which can effectively increase the volume of alum floc aggregation and utilize the advantage of calcium carbonate having a higher density than alum flocs to increase the sedimentation rate of alum flocs, thereby significantly improving the efficiency and effect of alum floc removal in the sedimentation tank.

[0019] 3. After addition, the agent of the present invention also utilizes the strong interaction characteristics of fluoride ions and calcium ions to make the alum flocs compact, which is beneficial to reducing the moisture content of the alum flocs and the total amount of fluoride removal sludge. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] Example 1:

[0022] A high-efficiency deep defluoridation agent is prepared from aluminum chloride hexahydrate, calcium carbonate, and sodium alginate. First, the calcium carbonate is pretreated under an ultrasonic power of 100W for 0.5h. Then, the aluminum chloride hexahydrate, ultrasonically pretreated calcium carbonate, and sodium alginate are mixed according to a molar ratio of aluminum chloride hexahydrate: calcium carbonate = 1:1 and calcium carbonate: sodium alginate = 1:1.5. Finally, the mixed raw materials are ground uniformly by ball milling.

[0023] Example 2:

[0024] A high-efficiency deep defluoridation agent is prepared from aluminum sulfate, calcium sulfate, and sodium carboxymethyl cellulose. First, the calcium sulfate is pretreated under an ultrasonic power of 500W for 0.5h. Then, the aluminum sulfate, calcium sulfate, and sodium carboxymethyl cellulose raw materials are mixed according to the molar ratio of aluminum sulfate:calcium sulfate = 1:2.5 and calcium sulfate:sodium carboxymethyl cellulose = 1:2. Finally, the mixed raw materials are ground uniformly by a rod mill.

[0025] Example 3:

[0026] A high-efficiency deep defluoridation agent is prepared from aluminum nitrate, calcium carbonate, and sodium alginate. First, the calcium carbonate is pretreated under an ultrasonic power of 300W for 0.5h. Then, the aluminum nitrate, calcium carbonate, and sodium alginate raw materials are mixed according to the molar ratio of aluminum nitrate:calcium carbonate = 1:1 and calcium carbonate:sodium alginate = 1:1.5. Finally, the mixed raw materials are evenly ground by a rod mill.

[0027] Example 4:

[0028] A high-efficiency deep defluoridation agent is prepared from aluminum chloride hexahydrate, calcium carbonate, and sodium carboxymethyl cellulose. The calcium carbonate is first pretreated under an ultrasonic power of 300W for 1 hour. The aluminum chloride hexahydrate, calcium carbonate, and sodium carboxymethyl cellulose are then mixed in a molar ratio of aluminum chloride hexahydrate: calcium carbonate = 1:5 and calcium carbonate: sodium carboxymethyl cellulose = 1:1. Finally, the mixed raw materials are evenly ground by ball milling.

[0029] The experimental subjects were the waters within an industrial park. A defluoridation agent was used at a dosage of 3-5 g / L. The defluoridation agent was added to the fluorinated water and stirred thoroughly. The supernatant was then filtered through a 0.45 μm membrane to analyze the fluoride ion concentration in the treated water. The treated defluoridated water was allowed to stand, and the settling time and size of the alum flocs were recorded. A common commercial flocculant was added to the control group, while the defluoridation agents prepared in the four examples above were used in the experimental groups. The test results for the different agents are shown in Table 1:

[0030] Table 1 Experimental results of using different defluoridation agents to treat fluoride-containing water

[0031]

[0032] It can be seen from the above table that compared with the treatment effect of the defluoridation agent in the comparative example, the defluoridation agent prepared by the present invention has excellent defluoridation effect. After defluoridation, the fluoride ion concentration in the water body is significantly reduced, the diameter of the formed alum flowers is significantly increased, and the alum flower sedimentation time is also significantly shortened.

[0033] The above description is only a preferred embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a defluorination agent, characterized in that: The defluoridation agent is composed of aluminum salt, calcium salt and gelling agent, and the preparation method comprises the following steps: firstly, pre-treating the calcium salt by ultrasound, then adding the aluminum salt and gelling agent to the treated calcium salt, and finally grinding and mixing them uniformly to obtain the defluoridation agent; The aluminum salt is selected from one or more of aluminum chloride hexahydrate, aluminum sulfate, and aluminum nitrate; The calcium salt is a poorly soluble inorganic calcium salt; The gelling agent is a chain organic substance containing carboxyl groups.

2. The preparation method according to claim 1, characterized in that The power of the ultrasonic treatment is 100-500W, and the time is 0.5-1h.

3. The preparation method according to claim 1, characterized in that The milling and mixing method is selected from one or more of ball milling, rod milling and grinding.

4. The defluorination agent obtained according to the preparation method of claim 1, 2 or 3.

5. The defluorination agent according to claim 4, characterized in that The molar ratio of the aluminum salt to the calcium salt is 1:1-1:5; the molar ratio of the calcium salt to the gelling agent is 1:1-1:

2.

6. The defluorination agent according to claim 5, characterized in that The poorly soluble inorganic calcium salt is selected from one or more of calcium carbonate, calcium phosphate and calcium sulfate.

7. The defluorination agent according to claim 5, characterized in that: The carboxyl-containing chain organic matter is selected from one or more of sodium alginate and sodium carboxymethyl cellulose.

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