Preparation method of fluorine removal agent

Abstract

The invention provides a preparation method of a fluorine removal agent, and belongs to the technical field of wastewater treatment.The preparation method comprises the steps that ferric sulfate and aluminum sulfate with the weight ratio being 1: (1.55-1.71) are taken to be prepared into a colloidal solution, then montmorillonite powder is added and mixed to be uniform, an obtained prefabricated material is roasted and smashed, and the fluorine removal agent is prepared. By controlling the dosage of ferric sulfate and aluminum sulfate and matching with specific process steps and parameters, a novel composite adsorption material is prepared, and the particle size, the shape, the structure and the chemical property of the composite adsorption material are effectively controlled, so that the fluorine removal agent with a good fluorine removal effect is obtained.

Description

Technical Field

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

[0002] Fluoride is an essential trace element for the human body, but excessive intake of fluoride can cause tooth decay and even fluoride poisoning, and can hinder the development of intelligence and body, affecting human health. Among them, pharmaceutical wastewater contains a certain amount of fluoride ions, which can penetrate into the ground through the soil layer when discharged directly, causing groundwater pollution and affecting human health.

[0003] At present, the commonly used treatment methods for fluorine-containing pharmaceutical wastewater at home and abroad include precipitation, coagulation, ion exchange, electrodialysis, reverse osmosis and adsorption. Among them, adsorption is a simple and easy-to-operate wastewater treatment technology and is the most widely used. Commonly used adsorbents for treating pharmaceutical wastewater mainly include ion exchange fibers and ion exchange resins, metal oxides and metal hydroxides, zeolites, carbonaceous adsorbents, natural materials and industrial by-products. However, existing defluoridation agents generally have problems such as a large amount of residual substances, poor sedimentation, and high cost. How to prepare a defluoridation agent with low cost, good sedimentation, and the ability to remove other substances in wastewater at the same time is one of the current research hotspots. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for preparing a defluorinating agent.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A method for preparing a defluorinating agent comprises the following steps: preparing a colloidal solution of iron sulfate and aluminum sulfate in a weight ratio of 1:1.55-1.71, adding montmorillonite powder and mixing the solution, and calcining and crushing the obtained prefabricated material to obtain the defluorinating agent.

[0007] Furthermore, the colloidal solution is prepared by dissolving iron sulfate and aluminum sulfate in water and adding a sodium hydroxide aqueous solution dropwise to adjust the pH value.

[0008] Furthermore, after the sodium hydroxide aqueous solution is added dropwise, the pH value of the obtained system is 6.8-7.0.

[0009] Furthermore, the weight volume ratio of ferric sulfate to water is 1 g: 24-26 mL.

[0010] Further, after the dropwise addition of the sodium hydroxide aqueous solution is completed, sodium polyacrylate is added to the obtained system.

[0011] Furthermore, the weight ratio of ferric sulfate to sodium polyacrylate is 1:0.12-0.13.

[0012] Furthermore, the stirring speed during the preparation of the colloidal solution is 400-500 rpm.

[0013] Furthermore, the volume weight ratio of the colloidal solution to the montmorillonite powder is 1 mL: 2 to 2.2 g.

[0014] Furthermore, the calcination temperature is 200-210° C. and the calcination time is 2.8-3.2 h.

[0015] Furthermore, the montmorillonite powder is obtained by crushing montmorillonite and passing it through a 180-200 mesh sieve.

[0016] The beneficial effects of the preparation method of a defluorination agent of the present invention are:

[0017] The present invention uses a sol-gel method to prepare a new type of defluoridation agent, which can effectively remove COD and phosphate while removing fluoride ions;

[0018] The present invention controls the dosage of ferric sulfate and aluminum sulfate and cooperates with specific process steps and parameters to prepare a novel composite adsorption material, and effectively controls the particle size, shape, structure and chemical properties of the composite adsorption material, thereby obtaining a defluorination agent with good defluorination effect;

[0019] The present invention prepares a defluorinating agent by using a colloidal solution made of iron sulfate and aluminum sulfate in a specific ratio; the iron hydroxide and aluminum hydroxide colloids in a specific ratio contained in the prepared defluorinating agent can effectively adsorb fluoride ions and effectively remove COD and phosphate as a flocculant;

[0020] At the same time, the present invention loads aluminum hydroxide and ferric hydroxide on montmorillonite for modification, utilizes the layered structure and high specific surface area of ​​montmorillonite, provides more adsorption sites for aluminum hydroxide and ferric hydroxide loaded on its surface, improves the adsorption capacity, and utilizes Na+ between montmorillonite layers. + , Ca 2+ Isocations and Al 3+ , Fe 3+ Exchange, enhance the adsorption performance of the defluoridation agent, and use the charge on the surface of the defluoridation agent to further enhance the adsorption through electrostatic action;

[0021] Furthermore, aluminum hydroxide and ferric hydroxide loaded on montmorillonite can improve their dispersibility and stability, avoiding the problem of easy aggregation when used alone; at the same time, the loaded aluminum hydroxide and ferric hydroxide can make the flocs formed after adsorbing fluoride ions, COD and phosphate more compact and have better sedimentation performance, which is convenient for subsequent separation;

[0022] In addition, the specific proportion of aluminum hydroxide and iron hydroxide loaded on montmorillonite can complement each other's charge and improve the adsorption effect; at the same time, the specific proportion of aluminum hydroxide and iron hydroxide can also increase each other's adsorption sites and specific surface area, improve the adsorption capacity, and the interaction between the three can also improve the density of the flocs, further providing adsorption and flocculation effects;

[0023] Furthermore, when aluminum hydroxide and ferric hydroxide in a specific ratio act together, a mixed precipitate (such as Fe 3+ -Al 3+ -PO4 3- ), improve the removal efficiency of phosphate;

[0024] The preparation method of the invention is simple to operate, and the prepared defluorinating agent has a small and stable particle size, and can effectively remove fluoride ions in wastewater. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0026] Example 1 A method for preparing a defluorinating agent

[0027] This embodiment is a method for preparing a defluorinating agent, which is specifically as follows:

[0028] S1, crush montmorillonite and pass it through a 200-mesh sieve to obtain montmorillonite powder;

[0029] S2. Take 4 g of ferric sulfate and 6.2 g of aluminum sulfate, add them to 100 mL of water, stir and dissolve, then add 10% sodium hydroxide aqueous solution dropwise while stirring at a speed of 400 rpm until the pH of the obtained system is 6.8, stop adding the sodium hydroxide aqueous solution, add 0.5 g of sodium polyacrylate, and continue stirring at a speed of 400 rpm for 10 minutes to obtain a colloidal solution; wherein, the addition of sodium polyacrylate can maintain the stability of the colloidal solution, which is conducive to more uniform loading of iron hydroxide and aluminum hydroxide on the montmorillonite powder in the later stage.

[0030] S3, take 15mL of the colloidal solution, add 30g of montmorillonite powder in five batches while stirring at a speed of 400rpm, and continue to stir and mix evenly after the montmorillonite powder is added to obtain a prefabricated material;

[0031] S4. Take the prefabricated material and put it into a muffle furnace, bake it at 200℃ for 3h, then naturally cool it to room temperature, grind it into powder, pass it through a 60-mesh sieve, and obtain a defluorination agent, marked as F1.

[0032] S5. Take 1L of secondary effluent from pharmaceutical wastewater (fluoride ion concentration is 59.3mg / L, COD is 183mg / L, phosphate is 17.2mg / L), add 10g of defluoridation agent F1, stir and react for 1.5h, filter, and take the clear liquid for testing. The fluoride ion concentration in the clear liquid is 0.8mg / L, COD is 25mg / L, and phosphate is 0.3mg / L. The fluoride removal rate is 98.65%, the COD removal rate is 86.34%, and the phosphate removal rate is 98.26%.

[0033] Embodiment 2~5 Preparation method of defluorination agent

[0034] Examples 2 to 5 are respectively methods for preparing a defluorinating agent, which are substantially the same as Example 1, except that some process parameters are different, as shown in Table 1:

[0035] Table 1 List of process parameters in Examples 2 to 5

[0036]

[0037]

[0038] The contents and results of other parts of Examples 2 to 5 are basically the same as those of Example 1 and will not be repeated here.

[0039] Experimental Example 1 Preparation method of defluorination agent

[0040] Comparative Examples 1 to 7 are comparative tests of the preparation method of the defluorinating agent in Example 1, and the prepared defluorinating agent is used to treat the secondary effluent of the same batch of pharmaceutical wastewater as Example 1, and the steps are basically the same as those in Example 1, except that:

[0041] In step S2 of comparative example 1, 3.1 g of aluminum sulfate is used instead of 6.2 g of aluminum sulfate, and the amounts of other raw materials, process steps and parameters remain unchanged. The prepared defluorinating agent is marked as DF1, and the defluorinating agent DF1 is used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration is 59.3 mg / L, COD is 183 mg / L, and phosphate is 17.2 mg / L). The fluoride ion concentration in the clear liquid after treatment is 5.4 mg / L, COD is 67 mg / L, and phosphate is 2.5 mg / L. The fluoride removal rate is 90.89%, the COD removal rate is 63.39%, and the phosphate removal rate is 85.47%.

[0042] In step S2 of comparative example 2, 9.3 g of aluminum sulfate is used instead of 6.2 g of aluminum sulfate, and the amounts of other raw materials, process steps and parameters remain unchanged. The prepared defluorinating agent is marked as DF2. The defluorinating agent DF2 is used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration is 59.3 mg / L, COD is 183 mg / L, and phosphate is 17.2 mg / L). The fluoride ion concentration in the clear liquid after treatment is 3.7 mg / L, COD is 44 mg / L, and phosphate is 1.7 mg / L. The fluoride removal rate is 93.76%, the COD removal rate is 75.96%, and the phosphate removal rate is 90.12%.

[0043] In step S2 of comparative example 3, after adding sodium hydroxide aqueous solution until the pH of the obtained system is 8.0, the addition of sodium hydroxide aqueous solution is stopped, and the amounts of other raw materials, process steps and parameters remain unchanged. The prepared defluorinating agent is marked as DF3, and the defluorinating agent DF3 is used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration is 59.3 mg / L, COD is 183 mg / L, and phosphate is 17.2 mg / L). The fluoride ion concentration in the clear liquid after treatment is 7.5 mg / L, COD is 83 mg / L, and phosphate is 3.4 mg / L. The fluoride removal rate is 87.35%, the COD removal rate is 54.64%, and the phosphate removal rate is 80.23%.

[0044] In step S2 of comparative example 4, sodium polyacrylate was not added, and the system obtained by directly adding sodium hydroxide aqueous solution until the pH of the system was 6.8 was used as the colloidal solution. The amounts of other raw materials, process steps and parameters remained unchanged. The prepared defluorinating agent was marked as DF4, and the defluorinating agent DF4 was used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration was 59.3 mg / L, COD was 183 mg / L, and phosphate was 17.2 mg / L). The fluoride ion concentration in the clear liquid after treatment was 3.1 mg / L, COD was 52 mg / L, and phosphate was 2.2 mg / L. The fluoride removal rate was 94.77%, the COD removal rate was 71.58%, and the phosphate removal rate was 87.21%.

[0045] In step S4 of comparative example 5, 15 g of montmorillonite powder is used instead of 30 g of montmorillonite powder, and the amounts of other raw materials, process steps and parameters remain unchanged. The prepared defluorinating agent is marked as DF5, and the defluorinating agent DF5 is used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration is 59.3 mg / L, COD is 183 mg / L, and phosphate is 17.2 mg / L). The fluoride ion concentration in the clear liquid after treatment is 3.8 mg / L, COD is 47 mg / L, and phosphate is 2.3 mg / L. The fluoride removal rate is 93.59%, the COD removal rate is 74.32%, and the phosphate removal rate is 88.95%.

[0046] In step S4 of comparative example 6, 45 g of montmorillonite powder is used instead of 30 g of montmorillonite powder, and the amounts of other raw materials, process steps and parameters remain unchanged. The prepared defluorinating agent is marked as DF6, and the defluorinating agent DF6 is used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration is 59.3 mg / L, COD is 183 mg / L, and phosphate is 17.2 mg / L). The fluoride ion concentration in the clear liquid after treatment is 6.6 mg / L, COD is 74 mg / L, and phosphate is 2.9 mg / L. The fluoride removal rate is 88.87%, the COD removal rate is 59.56%, and the phosphate removal rate is 83.14%.

[0047] In step S4 of comparative example 7, calcination at 400°C for 3h is used instead of calcination at 200°C for 3h. The amounts of other raw materials, process steps and parameters remain unchanged. The obtained defluorinator is marked as DF7. The defluorinator DF7 is used to treat the secondary effluent of pharmaceutical wastewater (fluoride ion concentration is 59.3mg / L, COD is 183mg / L, phosphate is 17.2mg / L). The fluoride ion concentration in the clear liquid after treatment is 5.7mg / L, COD is 79mg / L, phosphate is 3.2mg / L, the fluoride removal rate is 90.39%, the COD removal rate is 56.83%, and the phosphate removal rate is 81.40%.

[0048] Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a defluorinating agent, characterized in that: The preparation method comprises the following steps: preparing a colloidal solution of iron sulfate and aluminum sulfate in a weight ratio of 1:1.55-1.71, then adding montmorillonite powder and mixing evenly, and roasting and crushing the obtained prefabricated material to obtain the defluorination agent.

2. The method for preparing a defluorinating agent according to claim 1, characterized in that: The colloidal solution is prepared by dissolving ferric sulfate and aluminum sulfate in water and adding a sodium hydroxide aqueous solution dropwise to adjust the pH value.

3. The method for preparing a defluorinating agent according to claim 2, characterized in that: After the sodium hydroxide aqueous solution was added dropwise, the pH value of the obtained system was 6.8-7.

0.

4. The method for preparing a defluorinating agent according to claim 2 or 3, characterized in that: The weight volume ratio of ferric sulfate to water is 1g:24-26mL.

5. The method for preparing a defluorinating agent according to claim 2 or 3, characterized in that: After the dropwise addition of the sodium hydroxide aqueous solution was completed, sodium polyacrylate was added to the resulting system.

6. The method for preparing a defluorinating agent according to claim 5, characterized in that: The weight ratio of ferric sulfate to sodium polyacrylate is 1:0.12-0.

13.

7. The method for preparing a defluorinating agent according to claim 2, 3 or 6, characterized in that: The stirring speed during the preparation of the colloidal solution is 400-500 rpm.

8. The method for preparing a defluorinating agent according to claim 1, 2, 3 or 6, characterized in that: The volume weight ratio of the colloidal solution to the montmorillonite powder is 1 mL: 2 to 2.2 g.

9. The method for preparing a defluorinating agent according to claim 1, 2, 3 or 6, characterized in that: The calcination temperature is 200-210°C and the calcination time is 2.8-3.2h.

10. The method for preparing a defluorinating agent according to claim 1, 2, 3 or 6, characterized in that: Montmorillonite powder is obtained by crushing montmorillonite and passing it through a 180-200 mesh sieve.

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