Composite fluorine removal agent for treating fluorine-containing wastewater as well as preparation method and application of composite fluorine removal agent

Abstract

The invention discloses a composite fluorine removal agent for treating fluorine-containing wastewater as well as a preparation method and application of the composite fluorine removal agent. The composite fluorine removal agent is prepared from the following raw material components: polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, scandium sulfate, epoxy chloropropane, potassium citrate and paraformaldehyde. According to the composite fluorine removal agent, under the synergistic effect of all the components, fluorine ions in waste water can be rapidly converted into composite fluoride precipitates, particularly under the action of scandium sulfate, the fluorine ions in the waste water can be more thoroughly precipitated, and the composite fluorine removal agent has the advantages of being low in cost, good in fluorine removal effect, environmentally friendly and the like; through the combined action of the procedures of polyaluminum chloride, the composite fluorine removal agent and the flocculant, fluorine ions in the wastewater can be more thoroughly removed, so that the fluorine content in the filtrate is less than 0.1 mg / L. The method has the advantages of simple process, convenience in operation, low treatment cost, high treatment efficiency, good removal effect and the like, and can be widely used for treating fluorine-containing wastewater with different water qualities.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering, and relates to a composite defluorinating agent for treating fluorine-containing wastewater, and a preparation method and application thereof. Background Art

[0002] Fluoride-containing wastewater mainly comes from traditional fluorine chemical industry, electronic components, coke, electroplating, steel smelting and other industrial production processes. Most fluorides are soluble in water, and the fluorine element in wastewater mainly exists in the form of fluorosilicic acid, soluble fluoride salts, etc. In the natural environment, when fluorine enters the soil in the form of ions, it will lead to a decrease in the soil's decomposition ability. Fluorine is an important trace element for the growth and metabolism of plants and animals, but fluorine has certain toxicity. When plants absorb excessive fluorine, since the plant absorbs fluorine ions in the root and stem, it will cause damage to the chloroplasts and affect photosynthesis; when animals consume food containing high concentrations of fluorine, it will affect their health. For example, when the fluorine concentration in the water source that humans drink for a long time is >0.3 mg / L, the risk of osteoporosis increases significantly, and excessive intake of fluorine will affect the body's enzyme activity, leading to a decrease in endocrine function and causing diseases. Therefore, strengthening the treatment of fluoride-containing wastewater is of great significance to maintaining the ecological environment and promoting the harmonious development of man and nature.

[0003] At present, the main fluorine removal processes include precipitation, adsorption, membrane separation and other process technologies. Precipitation is widely used in the treatment of fluorine-containing wastewater, including chemical precipitation, flocculation precipitation, coagulation precipitation, etc.; adsorption is the use of porous adsorption media to adsorb fluoride ions to the surface of the adsorption medium under the action of ion exchange, and remove fluoride from the wastewater through physical adsorption or chemical reaction. Among them, commonly used adsorption media include activated carbon, ion exchange resin, modified zeolite, etc.; membrane separation mainly includes electrodialysis and reverse osmosis. For fluorine-containing wastewater generated by different industries, a single treatment method is difficult to meet the treatment requirements, and the current main fluorine-containing wastewater treatment methods have their own limitations. For example, the precipitation method cannot meet the treatment standards in theory, and the adsorption method, membrane method and biological method have different requirements for the salinity and biodegradability of the influent water quality. In response to the above problems, some researchers have proposed a composition for recovering fluorine from fluorine-containing wastewater, including a first composition and a second composition, wherein the first composition is a calcium-containing solid, and the second composition includes an aluminum-containing solid, an iron-containing solid, and an alkaline activator. The composition is used to treat fluorine-containing wastewater to achieve the discharge of fluorine-containing wastewater and the recovery of fluorine in the wastewater. However, this method still has defects such as poor precipitation effect and high fluorine content in the filtrate after treatment. In particular, it is difficult to reduce the fluorine concentration in the wastewater to below 0.1 mg / L. Therefore, when the treated filtrate is discharged into the ecological environment, it will still affect the growth of animals and plants and endanger human health. Therefore, obtaining a composite defluoridation agent with good precipitation effect and more thorough removal effect has better practical application value for achieving deep purification of fluorine-containing wastewater. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a composite defluorinating agent for treating fluorine-containing wastewater with good precipitation effect and more thorough removal effect, as well as a preparation method and application thereof.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0006] A composite defluorinating agent for treating fluorine-containing wastewater, the composite defluorinating agent comprising the following raw material components: polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate and paraformaldehyde; the mass ratio of the polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate is 33-37: 23-27: 18-22: 13-17: 3-7, and the mass ratio of the total mass of the polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate to the mass ratio of the epichlorohydrin, potassium citrate and paraformaldehyde is 4.5-6.5: 1.5-3.5: 0.5-2.5: 0.5-1.5.

[0007] The above-mentioned composite defluoridating agent is further improved, wherein the mass ratio of the polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate is 35:25:20:15:5, and the mass ratio of the total mass of the polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate to the mass ratio of the epichlorohydrin, potassium citrate and paraformaldehyde is 5.5:2.5:1.5:0.5.

[0008] As a general technical concept, the present invention also provides a method for preparing a composite defluorinating agent for treating fluorine-containing wastewater, comprising the following steps: S1, mixing polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate to obtain a mixture; the mass ratio of the polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate is 33-37:23-27:18-22:13-17:3-7; S2. Mix the mixture obtained in step S1, epichlorohydrin, potassium citrate and paraformaldehyde, and obtain a composite defluorinating agent by drying, grinding and sieving; the mass ratio of the mixture, epichlorohydrin, potassium citrate and paraformaldehyde is 4.5-6.5:1.5-3.5:0.5-2.5:0.5-1.5.

[0009] The above preparation method is further improved in that the particle size of the composite defluorinating agent is 80-120 mesh, the drying temperature is 25° C.-35° C., and the drying pressure is 0.1 MPa-0.12 MPa.

[0010] As a general technical concept, the present invention also provides an application of the above-mentioned composite defluorinating agent in treating fluoride-containing wastewater.

[0011] The above application, further improved, comprises the following steps: (1) adjusting the pH value of the fluoride-containing wastewater to 8-9 to obtain a mixed solution A; (2) mixing the mixed solution A obtained in step (1) with polyaluminium chloride to obtain a mixed solution B; (3) adding a composite defluorinating agent to the mixed solution B obtained in step (2) to carry out a precipitation reaction to obtain a mixed solution C; (4) Add a flocculant to the mixed solution C obtained in step (3) for flocculation treatment, and filter to complete the treatment of the fluorine-containing wastewater.

[0012] The above application is further improved, in step (2), the polyaluminium chloride is implemented in the form of a polyaluminium chloride solution, the volume ratio of the polyaluminium chloride solution to the fluorine-containing wastewater is 1 to 5:200, and the mass percentage concentration of the polyaluminium chloride solution is 1% to 1.5%; In step (3), the composite defluorinating agent is implemented in the form of a composite defluorinating agent dispersion, and the volume ratio of the composite defluorinating agent dispersion to the fluorine-containing wastewater is 0.5 to 1:200; the preparation process of the composite defluorinating agent dispersion is: mixing the composite defluorinating agent and water to obtain the composite defluorinating agent dispersion, and the mass percentage concentration of the composite defluorinating agent dispersion is 5%; In step (4), the volume ratio of the flocculant to the fluorine-containing wastewater is 0.5-1.5:200, the flocculant is a polyacrylamide solution, and the mass percentage concentration of the polyacrylamide solution is 0.1%.

[0013] The above application is further improved in that the volume ratio of the polyaluminium chloride solution to the fluorine-containing wastewater is 1:200, the volume ratio of the composite defluorination agent dispersion to the fluorine-containing wastewater is 0.7-0.8:200, and the volume ratio of the flocculant to the fluorine-containing wastewater is 0.5:200.

[0014] The above application is further improved in that the fluorine concentration in the fluorine-containing wastewater is ≤20 mg / L.

[0015] The above application is further improved in that in step (1), a calcium oxide emulsion is used to adjust the pH value of the fluoride-containing wastewater; In step (3), the precipitation reaction time is 30 min to 60 min; In step (4), the flocculation treatment time is 60 min to 120 min.

[0016] Compared with the prior art, the advantages of the present invention are: (1) The present invention provides a composite defluorinating agent for treating fluorine-containing wastewater, which uses polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate and paraformaldehyde as raw materials, and according to the mass ratio of polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate of 33-37:23-27:18-22:13-17:3-7, and the mass ratio of their total mass to epichlorohydrin, potassium citrate and paraformaldehyde of 4.5-6.5:1.5-3.5:0.5-2.5:0.5-1.5, they are compounded into a composite defluorinating agent with good precipitation effect and more thorough removal effect. When the composite defluorinating agent of the present invention is used to treat fluorine-containing wastewater, under the synergistic effect of each component, fluoride ions in the wastewater are quickly converted into composite fluoride precipitates, especially under the action of scandium sulfate, the fluoride ions in the wastewater can be precipitated more thoroughly, and finally the effect of deep removal of fluoride in the wastewater is achieved. At the same time, each raw material in the composite defluoridation agent will also be transferred to the precipitate, so by filtering, the heavy metals and epichlorohydrin and citric polyformaldehyde in the raw materials can also be removed at the same time. More importantly, by optimizing the dosage of each raw material in the composite defluoridation agent, the utilization rate of each raw material can be improved to the greatest extent, so as to ensure that the fluoride ions in the filtrate are up to standard, and the residual raw material components in the filtrate can also be avoided, so that the contents of fluoride ions and raw material components in the filtrate can reach the emission limit, so as to avoid the hidden danger of secondary pollution of harmful substances to the water environment. The composite defluoridation agent of the present invention has the advantages of low cost, good defluoridation effect, green environmental protection, etc., is a novel defluoridation agent with excellent defluoridation performance, can be widely used in treating fluorine-containing wastewater, and can achieve deep treatment, high use value, and good application prospects.

[0017] (2) The present invention also provides a method for preparing a composite defluorinating agent for treating fluorine-containing wastewater, wherein the raw materials are polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate, and paraformaldehyde, and the mass ratio of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, and scandium sulfate is 33-37:23-27:18-22:13-17:3-7, and the mass ratio of their total mass to epichlorohydrin, potassium citrate, and paraformaldehyde is 4.5-6.5:1.5-3.5:0.5-2.5:0.5-1.5. The composite defluorinating agent with good precipitation effect and more thorough removal effect can be prepared by mixing them. At the same time, the preparation method also has the advantages of simple process and operation, strong adaptability, etc., and is suitable for large-scale preparation and convenient for industrial application.

[0018] (3) The present invention also provides an application of a composite defluoridation agent in treating fluoride-containing wastewater. The pH value of the fluoride-containing wastewater is first adjusted to 8-9, and then polyaluminium chloride is added as a capture agent to promote the subsequent precipitation reaction and enhance the effect of the precipitation reaction. Then, the composite defluoridation agent is added to carry out a precipitation reaction, that is, a chemical reaction occurs between the effective components in the composite defluoridation agent and fluoride ions and is quickly converted into a composite fluoride precipitate. Finally, a flocculant is added. Through the flocculation effect of the flocculant, the composite fluoride precipitate is promoted to agglomerate and the sedimentation effect is improved. The wastewater and the composite fluoride precipitate are effectively separated by filtration, thereby achieving deep purification of the fluoride-containing wastewater. In the present invention, through the combined action of the processes such as "polyaluminium chloride + composite defluoridating agent + flocculant", the fluoride ions in the wastewater can be more thoroughly removed, so that the fluoride content in the filtrate is less than 0.1 mg / L. The present invention has the advantages of simple process, convenient operation, low treatment cost, high treatment efficiency, good removal effect, etc., can be widely used in treating fluoride-containing wastewater of different water qualities, and can achieve effective purification of fluoride-containing wastewater, which is of great significance for the effective treatment of fluoride-containing wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the process flow of treating fluoride-containing wastewater using a composite defluorinating agent in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0021] Embodiment 1: A composite defluorinating agent for treating fluorine-containing wastewater of the present invention is composed of the following raw material components: polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate and paraformaldehyde; wherein the mass ratio of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate is 35:25:20:15:5, and the mass ratio of the total mass of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate to that of epichlorohydrin, potassium citrate and paraformaldehyde is 5.5:2.5:1.5:0.5.

[0022] A method for preparing a composite defluorinating agent for treating fluorine-containing wastewater according to this embodiment comprises the following steps: (1) Polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate are uniformly mixed in a mass ratio of 35:25:20:15:5 to obtain a mixture A; (2) Mixing mixture A, epichlorohydrin, potassium citrate and paraformaldehyde in a mass ratio of 5.5:2.5:1.5:0.5 to obtain mixture B; (3) The mixture B obtained in step (2) is dried at a temperature of 25° C. and a pressure of 0.12 MPa, and then ground and sieved to control the particle size to 80 mesh to 120 mesh to obtain a composite defluorination agent.

[0023] An application of the composite defluoridation agent prepared in the above embodiment in treating fluoride-containing wastewater is to use a combined process of "polyaluminium chloride + composite defluoridation agent + flocculant" to treat fluoride-containing wastewater. The treatment process is as follows: Figure 1 As shown, the following steps are included: (1) Mixing the prepared composite defluorinating agent with water to obtain a composite defluorinating agent dispersion, wherein the mass percentage concentration of the composite defluorinating agent in the composite defluorinating agent dispersion is 5%.

[0024] (2) Take 200 mL of fluorine-containing wastewater with a concentration of 2.71 mg / L, add CaO emulsion to adjust the pH to 9 while stirring; add 1 mL of polyaluminium chloride solution (the mass percentage concentration of the solution is 1%) and stir evenly; then add 0.7 mL of the above-mentioned composite defluorination agent dispersion for precipitation reaction while stirring for 30 minutes; then add 0.5 mL of polyacrylamide solution (the mass percentage concentration of the solution is 0.1%) for flocculation treatment, stir for 5 minutes, let stand for 1 hour, filter, and complete the treatment of fluorine-containing wastewater.

[0025] The filtrate obtained after filtration was tested to obtain the residual fluorine (F - ) concentrations, and the results are shown in Table 1.

[0026] Embodiment 2: A composite defluorinating agent for treating fluorine-containing wastewater of the present invention is composed of the following raw material components: polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate and paraformaldehyde; wherein the mass ratio of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate is 35:25:20:15:3, and the mass ratio of the total mass of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate to that of epichlorohydrin, potassium citrate and paraformaldehyde is 5.5:2.5:1.5:0.5.

[0027] A method for preparing a composite defluorinating agent for treating fluorine-containing wastewater in this embodiment is substantially the same as the method for preparing the composite defluorinating agent in Example 1, except that the amount of raw materials used in the composite defluorinating agent is different.

[0028] The application of the composite defluorinating agent prepared in the present embodiment in treating fluoride-containing wastewater is basically the same as the application method in embodiment 1, except that the composite defluorinating agent prepared in embodiment 2 replaces the composite defluorinating agent prepared in embodiment 1.

[0029] The filtrate obtained after filtration was tested to obtain the residual fluorine (F - ) concentrations, and the results are shown in Table 1.

[0030] Embodiment 3: A composite defluorinating agent for treating fluorine-containing wastewater of the present invention is composed of the following raw material components: polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate and paraformaldehyde; wherein the mass ratio of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate is 35:25:20:15:7, and the mass ratio of the total mass of polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate to that of epichlorohydrin, potassium citrate and paraformaldehyde is 5.5:2.5:1.5:0.5.

[0031] A method for preparing a composite defluorinating agent for treating fluorine-containing wastewater in this embodiment is substantially the same as the method for preparing the composite defluorinating agent in Example 1, except that the amount of raw materials used in the composite defluorinating agent is different.

[0032] The application of the composite defluorinating agent prepared in the above-mentioned embodiment in treating fluoride-containing wastewater is basically the same as the application method in embodiment 1, with the only difference being that the composite defluorinating agent prepared in embodiment 3 replaces the composite defluorinating agent prepared in embodiment 1.

[0033] The filtrate obtained after filtration was tested to obtain the residual fluorine (F - ) concentrations, and the results are shown in Table 1.

[0034] Comparative Example 1: A composite defluorinating agent is substantially the same as the composite defluorinating agent of Example 1, except that scandium sulfate is not added in Comparative Example 1.

[0035] The application of the composite defluorinating agent prepared in the above-mentioned comparative example 1 in treating fluorine-containing wastewater is basically the same as the application method in Example 1, except that the composite defluorinating agent prepared in comparative example 1 replaces the composite defluorinating agent prepared in Example 1.

[0036] The filtrate obtained after filtration was tested to obtain the residual fluorine (F - ) concentrations, and the results are shown in Table 1.

[0037] Table 1 Comparison of the defluorination effects of different composite defluoridation agents on fluoride-containing wastewater

[0038] As shown in Table 1, in Examples 1, 2 and 3, the purification process technology of "polyaluminium chloride + composite defluoridation agent + flocculant" of the present invention is used to treat low-concentration fluorine-containing wastewater, and the fluorine in the fluorine-containing wastewater is deeply treated by chemical precipitation, flocculation and filtration, and the fluorine in the wastewater can be reduced to <0.1 mg / L. In Comparative Example 1, since scandium sulfate is not added to the composite defluoridation agent, the defluoridation effect is poor and does not meet the discharge requirements.

[0039] At the same time, in this embodiment, the residual amount of each raw material (scandium sulfate, epichlorohydrin, and paraformaldehyde) in the filtrate obtained after treatment with different composite defluorinating agents was also detected, and the results are shown in Table 2.

[0040] Table 2 Comparison of the contents of scandium, epichlorohydrin and paraformaldehyde in the filtrate obtained after treatment with different composite defluorinating agents

[0041] As shown in Table 2, the residual content of scandium in the filtrate treated with the composite defluorinating agent of the present invention in Examples 1 to 3 is very low, and when the content of scandium in the filtrate is ≤0.5 mg / L, the pollution risk caused by them to the water environment and humans is negligible. In addition, no epichlorohydrin or paraformaldehyde was detected in the filtrate. It can be seen that the residual amounts of scandium, epichlorohydrin, and paraformaldehyde in the filtrate after treatment with the composite defluorinating agent of the present invention are all very low, all of which meet the relevant emission standards, and they will not cause secondary pollution to the environment, and there is no safety hazard.

[0042] Embodiment 4: An application of the composite defluorinating agent for treating fluorine-containing wastewater of the present invention in treating fluorine-containing wastewater comprises the following steps: The composite defluorinating agent prepared in Example 1 was mixed with water to obtain a composite defluorinating agent dispersion (the mass percentage concentration of the dispersion was 5%); 200 mL of wastewater from a nonferrous metal smelter was taken, the fluorine concentration in the fluorine-containing wastewater was 3.67 mg / L, and CaO emulsion was added under stirring to adjust the pH to 9; 1 mL of polyaluminium chloride solution (the mass percentage concentration of the solution was 1%) was added and stirred evenly; 0.8 mL of the above composite defluorinating agent dispersion was added under stirring conditions for precipitation reaction, and stirred for 30 minutes. During this process, a chemical reaction occurred between the effective components in the composite defluorinating agent and the fluoride ions and they were quickly converted into composite fluoride precipitates; 0.5 mL of polyacrylamide solution (the mass percentage concentration of the solution was 0.1%) was added for flocculation treatment, and stirred for 5 minutes. During this process, the flocculation effect of the flocculant promoted the aggregation of the composite fluoride precipitate and improved the sedimentation effect. The mixture was allowed to stand for 1 hour to achieve solid-liquid separation, and filtered to complete the treatment of the fluoride-containing wastewater.

[0043] The filtrate obtained after filtration was tested to obtain the residual fluorine (F - ) concentrations, and the results are shown in Table 3.

[0044] In this example, the effects of different amounts of composite defluorinating agents on the defluorination effect of fluorine-containing wastewater were also investigated, as shown in Table 3. Except for the different amounts of composite defluorinating agents, other conditions were the same as those in Example 4.

[0045] Table 3 Comparison of the defluorination effects of different composite defluoridation agent dosage conditions on fluoride-containing wastewater

[0046] It can be seen from Table 3 that when the amount of composite defluorinating agent dispersion added is less than 0.5mL (such as 0.4mL), the defluorination effect is poor and does not meet the discharge requirements; when the amount of composite defluorinating agent dispersion added is 0.5mL~1.0mL, the defluorination effect is good, and the fluoride in the wastewater is reduced to <0.1mg / L, meeting the discharge requirements; when the amount of composite defluorinating agent dispersion added is greater than 1.0mL (such as 1.2mL), increasing the amount of composite defluorinating agent added has little effect on the defluorination effect.

[0047] It can be seen from the above results that compared with conventional defluoridation agents, the composite defluoridation agent of the present invention can quickly convert fluoride ions in wastewater into composite fluoride precipitation under the synergistic effect of various components, especially under the effect of scandium sulfate, which can make the fluoride ion precipitation in wastewater more thorough, which is conducive to deep removal of fluorine in wastewater, and will not bring secondary pollution, and has the advantages of low cost, good defluoridation effect, green environmental protection, etc. It is a new type of defluoridation agent with excellent defluoridation performance, which can be widely used in treating fluorine-containing wastewater, and can achieve deep treatment, high use value, and good application prospects. In addition, in the present invention, through the combined action of "polyaluminum chloride + composite defluoridation agent + flocculant" and other processes, the fluoride ions in the wastewater can be more thoroughly removed, so that the fluorine content in the filtrate is less than 0.1mg / L, with the advantages of simple process, convenient operation, low processing cost, high processing efficiency, good removal effect, etc., can be widely used in treating fluorine-containing wastewater of different water qualities, and can achieve effective purification of fluorine-containing wastewater, which is of great significance for efficient purification of fluorine-containing wastewater.

[0048] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A composite defluorinating agent for treating fluorine-containing wastewater, characterized in that: The composite defluorinating agent includes the following raw material components: polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, scandium sulfate, epichlorohydrin, potassium citrate, and paraformaldehyde; the mass ratio of the polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, and scandium sulfate is 33-37: 23-27: 18-22: 13-17: 3-7, and the mass ratio of the total mass of the polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate, and scandium sulfate to the mass ratio of the epichlorohydrin, potassium citrate, and paraformaldehyde is 4.5-6.5: 1.5-3.5: 0.5-2.5: 0.5-1.

5.

2. The composite defluorinating agent for treating fluorine-containing wastewater according to claim 1, characterized in that: The mass ratio of the polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate is 35:25:20:15:5, and the mass ratio of the total mass of the polyaluminum sulfate, polyferric sulfate, calcium carbonate, aluminum chlorohydrate and scandium sulfate to the mass ratio of the epichlorohydrin, potassium citrate and paraformaldehyde is 5.5:2.5:1.5:0.

5.

3. A method for preparing a composite defluorinating agent for treating fluorine-containing wastewater, characterized in that: The following steps are involved: S1, mixing polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate to obtain a mixture; the mass ratio of the polyaluminium sulfate, polyferric sulfate, calcium carbonate, aluminium chlorohydrate and scandium sulfate is 33-37:23-27:18-22:13-17:3-7; S2. Mix the mixture obtained in step S1, epichlorohydrin, potassium citrate and paraformaldehyde, and obtain a composite defluorinating agent by drying, grinding and sieving; the mass ratio of the mixture, epichlorohydrin, potassium citrate and paraformaldehyde is 4.5-6.5:1.5-3.5:0.5-2.5:0.5-1.

5.

4. The method for preparing a composite defluorinating agent for treating fluorine-containing wastewater according to claim 3, characterized in that: The particle size of the composite defluorinating agent is 80-120 meshes, the drying temperature is 25° C.-35° C., and the drying pressure is 0.1 MPa-0.12 MPa.

5. Use of the composite defluorinating agent as claimed in claim 1 or 2 or the composite defluorinating agent prepared by the preparation method as claimed in claim 3 or 4 in treating fluoride-containing wastewater.

6. The use according to claim 5, characterized in that: The following steps are involved: (1) adjusting the pH value of the fluoride-containing wastewater to 8-9 to obtain a mixed solution A; (2) mixing the mixed solution A obtained in step (1) with polyaluminium chloride to obtain a mixed solution B; (3) adding a composite defluorinating agent to the mixed solution B obtained in step (2) to carry out a precipitation reaction to obtain a mixed solution C; (4) Add a flocculant to the mixed solution C obtained in step (3) for flocculation treatment, and filter to complete the treatment of the fluorine-containing wastewater.

7. The use according to claim 6, characterized in that: In step (2), the polyaluminium chloride is implemented in the form of a polyaluminium chloride solution, the volume ratio of the polyaluminium chloride solution to the fluorine-containing wastewater is 1 to 5:200, and the mass percentage concentration of the polyaluminium chloride solution is 1% to 1.5%; In step (3), the composite defluorinating agent is implemented in the form of a composite defluorinating agent dispersion, and the volume ratio of the composite defluorinating agent dispersion to the fluorine-containing wastewater is 0.5 to 1:200; the preparation process of the composite defluorinating agent dispersion is: mixing the composite defluorinating agent and water to obtain the composite defluorinating agent dispersion, and the mass percentage concentration of the composite defluorinating agent dispersion is 5%; In step (4), the volume ratio of the flocculant to the fluorine-containing wastewater is 0.5-1.5:200, the flocculant is a polyacrylamide solution, and the mass percentage concentration of the polyacrylamide solution is 0.1%.

8. The use according to claim 7, characterized in that: The volume ratio of the polyaluminium chloride solution to the fluorine-containing wastewater is 1:200, the volume ratio of the composite defluorination agent dispersion to the fluorine-containing wastewater is 0.7-0.8:200, and the volume ratio of the flocculant to the fluorine-containing wastewater is 0.5:

200.

9. The use according to claim 8, characterized in that: The fluorine concentration in the fluorine-containing wastewater is ≤20 mg / L.

10. The use according to any one of claims 6 to 9, characterized in that: In step (1), the pH value of the fluoride-containing wastewater is adjusted using a calcium oxide emulsion; In step (3), the precipitation reaction time is 30 min to 60 min; In step (4), the flocculation treatment time is 60 min to 120 min.

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