Green co-treatment method for fluorine-containing wastewater and calcium-containing industrial solid waste

Abstract

The invention belongs to the technical field of waste treatment, and provides a fluorine-containing wastewater and calcium-containing industrial solid waste green co-treatment method which comprises the following steps: adding calcium-containing industrial solid waste into acidic fluorine-containing wastewater; the pH value of the aqueous solution of the calcium-containing industrial solid waste is greater than 7; and stirring to carry out precipitation reaction and flocculation reaction, and carrying out solid-liquid separation to obtain fluorine enrichment precipitate and supernate. The acidic fluorine-containing wastewater is treated by using the alkaline calcium-containing industrial solid waste, fluorine ions in the wastewater can be efficiently removed, the concentration of the fluorine ions in the treated system is stable and reaches the discharge standard, and the fluorine-containing wastewater deeply reaches the standard and the calcium-containing industrial solid waste is recycled through treatment of waste with waste, in-situ flocculation and one-step precipitation. The industrial wastewater-solid waste cooperative treatment system which is low in cost, high in efficiency and green and closed in loop is constructed, and the industrial wastewater-solid waste cooperative treatment system has the advantages of being high in universality and remarkable in industrial application value.

Description

A method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste Technical Field

[0001] This invention belongs to the field of waste treatment technology and relates to a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste. Background Technology

[0002] Fluorine is widely distributed in fluorine-containing minerals in the Earth's crust and can enter the ecological environment through various pathways such as geological weathering and industrial emissions. With the rapid development of modern industries such as electronic chemicals and semiconductor manufacturing, fluorine resources are widely used in materials processing, surface cleaning, etching, and fine chemicals, resulting in a large amount of fluorine-containing industrial wastewater.

[0003] The main sources of fluoride-containing wastewater currently include fluorite mining and deep processing, iron and steel smelting, thermal power generation, semiconductor cleaning and etching processes, silicate and pesticide production, non-ferrous metal smelting, and various fluoride preparation and reprocessing processes. Fluoride-containing industrial wastewater is characterized by large volumes, wide fluctuations in fluoride ion concentrations, and is often accompanied by strong acidity and complex coexisting ion systems. If discharged directly into the environment without effective treatment, fluoride ions will enter surface water, soil, and groundwater systems, easily causing long-term accumulation of fluoride in environmental media, thus posing a significant risk to ecosystem stability and human health. Simultaneously, industrial production generates large amounts of calcium-containing solid waste (steel slag, carbide slag, phosphogypsum, papermaking sludge, etc.), which occupy land when stockpiled, easily leachate and pollute the environment, and have low resource utilization rates.

[0004] Therefore, research on efficient, stable, and engineerable co-treatment technologies for fluoride-containing wastewater from industries such as electronics and calcium-containing industrial solid waste from industrial production is of significant environmental and social importance. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a green co-treatment method for fluoride-containing wastewater and calcium-containing industrial solid waste, which does not require segmented treatment or heating. Specifically, it includes adding calcium-containing industrial solid waste to acidic fluoride-containing wastewater; the pH of the aqueous solution of calcium-containing industrial solid waste is >7; stirring to carry out precipitation and flocculation reactions; and after solid-liquid separation, obtaining fluoride-rich precipitate and supernatant. By using calcium-containing industrial solid waste to treat fluoride-containing wastewater, this waste-to-waste treatment method can not only efficiently remove fluoride ions from the wastewater, ensuring that the fluoride ion concentration in the treated system stably meets the emission standards, but also has the advantages of wide availability of raw materials, simple operation, low treatment cost, adaptability to actual calcium-containing industrial solid waste and fluoride-containing industrial wastewater systems, and strong universality and significant industrial application value.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising the following steps: providing fluoride-containing wastewater with pH < 7; adding treated calcium-containing industrial solid waste to the fluoride-containing wastewater; wherein the aqueous solution of the calcium-containing industrial solid waste has pH > 7; stirring to simultaneously carry out precipitation and flocculation reactions; and obtaining fluoride-enriched precipitate and supernatant after solid-liquid separation.

[0007] Besides fluoride-containing wastewater, industries also generate large quantities of calcium-containing solid waste. The stockpiling and separate disposal of this waste not only consumes significant land resources but also negatively impacts the surrounding ecological environment. Furthermore, the valuable elements contained within the waste are not effectively utilized, resulting in resource waste. The fluoride ion removal method proposed in this invention utilizes a waste-to-waste approach. Acidic fluoride-containing wastewater is mixed with alkaline-treated calcium-containing industrial solid waste, and precipitation and flocculation reactions are carried out. The strong acidity of the fluoride-containing wastewater dissolves the calcium-containing industrial solid waste. Simultaneously, the precipitation and flocculation reactions work synergistically, allowing calcium ions to precipitate fluoride ions. This also effectively precipitates other metal elements in both the fluoride-containing wastewater and the calcium-containing industrial solid waste, forming colloids for further fluoride ion removal, thereby improving the effectiveness and efficiency of waste treatment. The removal method described in this invention ensures that the supernatant meets discharge standards. Therefore, calcium-containing solid waste can be directly used for the treatment of fluoride-containing wastewater. This not only helps to realize the resource utilization of industrial solid waste and reduce its potential pollution risks to the ecological environment, but also reduces the consumption of traditional chemical agents, thereby reducing the energy consumption of the treatment process and promoting the sustainable development of industrial production. Compared with existing calcium salt defluorination methods, this invention does not require step-by-step treatment and can simultaneously carry out the dual reactions of calcium salt precipitation and flocculation. Without the need for additional flocculants, it can enhance the destabilization, aggregation, and sedimentation of calcium fluoride colloids, significantly improving solid-liquid separation efficiency and effluent quality, achieving "waste-to-waste treatment, one agent with dual effects".

[0008] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0009] As a preferred technical solution of the present invention, the fluoride-containing wastewater contains, in addition to F - In addition, it also contains Na + Al 3+ Fe 2+ Ca 2+ K + Mg 2+ H + Cl - NO 3- SO4 2- PO4 3-At least one of the following ions. Fluoride-containing wastewater is typically acidic or even strongly acidic, so fluoride ions can coexist with other metal ions. Utilizing alkaline calcium-containing industrial solid waste to stabilize the system's pH between 7 and 13 facilitates the precipitation reaction, which is beneficial for removing Ca. 2+ Al 3+ Fe 2+ Mg 2+ SO4 2- and PO4 3- Simultaneously, sedimentation is carried out to improve the impurity removal effect.

[0010] As a preferred embodiment of the present invention, the concentration of fluoride ions in the fluoride-containing wastewater is 300 mg / L to 4000 mg / L. Exemplarily, the concentration of fluoride ions can be 300 mg / L, 500 mg / L, 800 mg / L, 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, or 4000 mg / L, etc. The removal method of the present invention is applicable to the treatment of fluoride-containing wastewater with a wide range of fluoride ion concentrations, and after precipitation reaction, the supernatant from solid-liquid separation can meet the discharge standard of ≤10 mg / L.

[0011] As a preferred embodiment of the present invention, the pH of the fluoride-containing wastewater is less than or equal to 1, i.e., it is strongly acidic.

[0012] As a preferred embodiment of the present invention, the calcium-containing industrial solid waste includes at least one of steel slag, fly ash, carbide slag, lead-zinc tailings, phosphogypsum, or papermaking sludge. In addition to Ca, the calcium-containing industrial solid waste also contains at least one of Al, Fe, or Mg. During precipitation reactions at pH > 7, the simultaneous removal of these other metal elements through precipitation and flocculation reactions is facilitated.

[0013] As a preferred embodiment of the present invention, the calcium-containing industrial solid waste includes at least one of calcium oxide, calcium chloride, or calcium hydroxide, and the mass percentage of Ca is ≥1%. Exemplarily, the mass percentage of Ca can be 1%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 30%, 50%, 70%, or 90%, etc. Preferably, it is 20%~90%. In the present invention, when calcium exists in the calcium-containing industrial solid waste as calcium oxide, calcium chloride, or calcium hydroxide, the aqueous solution of the calcium-containing industrial solid waste is alkaline. When subsequently mixed with fluoride-containing wastewater, this helps control the system pH > 7. Furthermore, since calcium oxide, calcium chloride, or calcium hydroxide dissolves in the fluoride-containing wastewater as active calcium ions, it is more conducive to the precipitation of fluoride.

[0014] As a preferred technical solution of the present invention, the method for preparing the treated calcium-containing industrial solid waste includes crushing, grinding and calcining the calcium-containing industrial solid waste in advance.

[0015] As a preferred technical solution of the present invention, the dosage is controlled according to the molar amount of calcium in the calcium-containing industrial solid waste being 0.5 to 2 times the molar amount of fluoride in the fluoride-containing wastewater. For example, the multiple of the molar amount of calcium in the calcium-containing industrial solid waste can be 0.5, 0.8, 1, 1.3, 1.5, 1.8, or 2 times, etc. In order to ensure sufficient precipitation of fluoride ions in the fluoride-containing wastewater to meet the discharge standards for residual fluoride ion concentration in the supernatant, the calcium content in the calcium-containing industrial solid waste, especially the amount of calcium ions that can dissolve in water, is at least half the amount of fluoride in the fluoride-containing wastewater. This allows calcium ions to react with fluoride ions to form calcium fluoride precipitate, minimizing residual fluoride ions.

[0016] As a preferred embodiment of the present invention, the temperature for the precipitation and flocculation reactions is 15℃~35℃. Exemplarily, the temperature can be 15℃, 18℃, 20℃, 23℃, 25℃, 30℃, or 35℃, etc. In this invention, the precipitation and flocculation reactions can be carried out at room temperature or room temperature without additional heating. The precipitation and flocculation reactions are carried out at a pH > 7 to facilitate the precipitation and flocculation effects.

[0017] As a preferred embodiment of the present invention, the stirring time is 1 min to 60 min; the settling time after stirring is 1 h to 12 h; the solid-liquid separation method includes filtration. Exemplarily, the stirring time can be 1 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, or 60 min, etc.; the settling time can be 1 h, 3 h, 5 h, 8 h, or 10 h, etc. Appropriate stirring and settling facilitate more complete precipitation of fluoride ions and promote subsequent solid-liquid separation, resulting in a supernatant that meets emission standards.

[0018] As a preferred embodiment of the present invention, the concentration of fluoride ions in the supernatant is ≤10 mg / L. Exemplarily, the concentration of fluoride ions in the supernatant can be 10 mg / L, 8 mg / L, 5 mg / L, 3 mg / L, 1 mg / L, 0.5 mg / L, or 0.1 mg / L, etc. Supernatant with a fluoride ion concentration of less than 10 mg / L can meet the Class I standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996).

[0019] As a preferred technical solution of the present invention, the precipitation reaction and flocculation reaction work together to remove at least one of the elements Al, Fe and Mg contained in the calcium-containing industrial solid waste.

[0020] As a preferred technical solution of the present invention, the fluorine enrichment precipitate includes CaF2, and further mainly includes CaF2, which can be purified by water washing and weak acid leaching for resource utilization.

[0021] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0022] Compared with existing technologies, this invention has at least the following advantages: The fluoride ion removal method proposed in this invention can directly mix acidic fluoride-containing wastewater with alkaline calcium-containing industrial solid waste in aqueous solution and carry out precipitation and flocculation reactions to obtain fluoride-rich precipitates, and the supernatant can stably meet the treatment and discharge standards. By controlling pH and combining waste-to-waste treatment, not only can efficient removal of fluoride ions be achieved, but a new technical path for the resource utilization of calcium-containing solid waste can also be provided. Similarly, in addition to providing a new technical path for the resource utilization of calcium-containing solid waste, this invention can also solve the problems of complex equipment, cumbersome processes, limited applicable scenarios, and high treatment costs that are common in the current field of fluoride-containing industrial wastewater treatment. This removal method is applicable to fluoride-containing wastewater treatment technologies in complex application scenarios and has practical engineering application value. Attached Figure Description

[0023] Figure 1 is an XRD pattern of the fluorine-enriched precipitate obtained in Example 1. Detailed Implementation

[0024] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the invention and should not be considered as specific limitations thereof. Specific features, structures, or characteristics described in conjunction with the embodiments may be included in one or more embodiments or implementations of the present invention.

[0025] Unless otherwise defined or stated, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; unless otherwise stated, the values ​​of the parameters mentioned in this invention can be measured using various measurement methods commonly used in the art, for example, they can be tested according to the methods given in the embodiments of this invention.

[0026] The "scope" disclosed in this invention is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way can include or exclude end values, and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope.

[0027] In the description of this invention, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this invention can be performed sequentially or randomly. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or optionally steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may optionally include steps (a), (b), and (c), or may include steps (a), (c), and (b), or optionally steps (c), (a), and (b), etc.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0029] Example 1 This example provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising: providing acidic fluoride-containing wastewater containing Na + With F - The fluoride ion concentration was 400 mg / L. Lead-zinc tailings from calcium-containing industrial solid waste (CaO mass percentage 36%) were provided. At 25℃, 200 mL of fluoride-containing wastewater was accurately measured and poured into a beaker, and stirring was started at 300 rpm. 0.5322 g of lead-zinc tailings was added (controlling the molar ratio Ca:F = 1:1). Then, 20% NaOH solution was added dropwise to adjust the pH of the solution to 7.21. Stirring continued for 30 min. Stirring was stopped, and the mixture was allowed to stand for 1 h. After solid-liquid separation, a fluoride-rich precipitate and supernatant were obtained. The fluoride-rich precipitate, after washing with water, leaching with weak acid, and drying, yielded a high-purity CaF2 product, achieving resource utilization. The supernatant was tested, and the fluoride ion concentration was 2.2 mg / L. The calculated fluoride ion removal efficiency was 99.43%, meeting the emission standards.

[0030] Figure 1 is the XRD pattern of the fluoride-rich precipitate obtained in this embodiment. The fluoride-rich precipitate is mainly composed of calcium fluoride phase.

[0031] Example 2 This example provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising: providing acidic fluoride-containing wastewater containing Na + With F -The fluoride ion concentration was 325 mg / L. Calcium-containing industrial solid waste, carbide slag (CaO mass percentage 80%), was provided. At 25℃, 200 mL of fluoride-containing wastewater was accurately measured and poured into a beaker, and stirring was started at 200 rpm. 0.1197 g of carbide slag was added (controlling the molar ratio Ca:F = 0.5:1). 20% NaOH solution was added dropwise to adjust the pH of the solution to 11.08. Stirring was continued for 1 min. Stirring was stopped, and the mixture was allowed to stand for 6 h. After solid-liquid separation, a fluoride-rich precipitate and supernatant were obtained. The fluoride-rich precipitate, after washing with water, leaching with a weak acid, and drying, yielded a high-purity CaF2 product, achieving resource utilization. The supernatant was tested, and the fluoride ion concentration was 4.6 mg / L. The calculated fluoride ion removal efficiency was 98.58%, meeting the emission standards.

[0032] Example 3 This example provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising: providing acidic fluoride-containing wastewater containing Na + Al 3+ Fe 2+ Ca 2+ H + Cl - NO3 - SO4 2- F - The fluoride ion concentration is 325 mg / L; calcium-containing industrial solid waste fly ash (CaO mass percentage content is 25%) is provided.

[0033] At 25℃, 200 mL of fluoride-containing wastewater was accurately measured and poured into a beaker, and the mixture was stirred at 150 rpm. Then, 0.3832 g of fly ash was added (controlling the molar ratio Ca:F = 0.5:1). 20% NaOH solution was added dropwise to adjust the pH of the solution to 9.92. Stirring was continued for 5 min. Stirring was stopped, and the mixture was allowed to stand for 12 h. After solid-liquid separation, fluoride-rich precipitate and supernatant were obtained. The fluoride-rich precipitate was washed with water, soaked in a weak acid, and dried to obtain high-purity CaF2 product, realizing resource utilization. The supernatant was tested, and the fluoride ion concentration was 8.0 mg / L. The calculated fluoride ion removal efficiency was 97.54%, which meets the emission standards.

[0034] Example 4 This example provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising: providing acidic fluoride-containing wastewater containing Na + Al 3+ Fe 2+ Ca 2+ H + Cl - NO3 - SO4 2- F -The fluoride ion concentration is 325 mg / L; calcium-containing industrial solid waste phosphogypsum (CaO mass percentage is 34%) is provided.

[0035] At 25℃, 200 mL of fluoride-containing wastewater was accurately measured and poured into a beaker, and the mixture was stirred at 300 rpm. 0.8452 g of phosphogypsum was added (controlling the molar ratio Ca:F = 1.5:1). 20% NaOH solution was added dropwise to adjust the pH of the solution to 11.33. Stirring was continued for 15 min. Stirring was stopped, and the mixture was allowed to stand for 1 h. After solid-liquid separation, a fluoride-rich precipitate and a supernatant were obtained. The fluoride-rich precipitate was washed with water, soaked in a weak acid, and dried to obtain a high-purity CaF2 product, achieving resource utilization. The supernatant was tested, and the fluoride ion concentration was 5.2 mg / L. The calculated fluoride ion removal efficiency was 98.40%, meeting the emission standards.

[0036] Example 5 This example provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising: providing acidic fluoride-containing wastewater containing Na + Al 3+ Fe 2+ Ca 2+ K + Mg 2+ H + Cl - NO3 - SO4 2- F - PO4 3- The fluoride ion concentration was 325 mg / L. Calcium-containing industrial solid waste, carbide slag (CaO mass percentage 80%), was provided. At 25℃, 200 mL of fluoride-containing wastewater was accurately measured and poured into a beaker, and stirring was started at 300 rpm. Then, 0.4789 g of carbide slag was added (controlling the molar ratio Ca:F = 2:1). 20% NaOH solution was added dropwise to adjust the pH of the solution to 13.03. Stirring continued for 60 min. Stirring was stopped, and the mixture was allowed to stand for 6 h. After solid-liquid separation, a fluoride-rich precipitate and supernatant were obtained. The fluoride-rich precipitate was washed with water, soaked in a weak acid, and dried to obtain a high-purity CaF2 product, achieving resource utilization. The supernatant was tested, and the fluoride ion concentration was 6.0 mg / L. The calculated fluoride ion removal efficiency was 98.15%, meeting the emission standards.

[0037] Example 6 This example provides a method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, comprising: providing acidic fluoride-containing wastewater containing Na + Al 3+ Fe 2+ Ca 2+ K + Mg 2+ H +Cl - NO3 - SO4 2- F - PO4 3- The fluoride ion concentration was 325 mg / L. Calcium-containing industrial solid waste steel slag (CaO mass percentage 60%) was provided. At 25℃, 200 mL of fluoride-containing wastewater was accurately measured and poured into a beaker, and stirring was started at 300 rpm. Then, 0.3193 g of steel slag was added (controlling the molar ratio Ca:F = 1:1). 20% NaOH solution was added dropwise to adjust the pH of the solution to 12.03. Stirring continued for 60 min. Stirring was stopped, and the mixture was allowed to stand for 6 h. After solid-liquid separation, fluoride-rich precipitate and supernatant were obtained. The supernatant was tested, and the fluoride ion concentration was 8.0 mg / L. The calculated fluoride ion removal efficiency was 97.54%, meeting the emission standards.

[0038] Control Group 1: This control group provides a method for removing fluoride ions from fluoride-containing wastewater. The difference from Example 4 is the use of pure calcium oxide instead of calcium-containing industrial solid waste phosphogypsum. Specifically, 0.2874 g of pure calcium oxide is added (controlling the molar ratio Ca:F = 1.5:1); the pH of the solution is then adjusted to 11.33; after the reaction is completed, the supernatant is taken for testing, and the fluoride ion concentration is 5.2 mg / L; the calculated fluoride ion removal efficiency is 98.40%, which meets the emission standards.

[0039] The green co-treatment method for fluoride-containing wastewater and calcium-containing industrial solid waste provided by the embodiments of the present invention can meet the treatment and discharge standards, achieving the same treatment level as the pure calcium oxide used in control group 1. Simultaneously, the method provided by the embodiments of the present invention achieves waste-to-waste treatment, significantly controlling costs. For example, Table 1 lists the costs of treating fluoride-containing wastewater using the calcium-containing industrial solid waste used in the above embodiments, other calcium-containing industrial solid wastes, and the pure calcium oxide used in the control group. The effective CaO content and price are all cost-effective averages. It can be seen that the cost of treating fluoride-containing wastewater using calcium-containing industrial solid waste is significantly reduced, with raw material costs lowered by more than 85% compared to pure calcium oxide, demonstrating significant economic advantages. Furthermore, combined with current subsidy policies for calcium-containing industrial solid waste, the cost can be controlled to less than or equal to zero, demonstrating significant practical application value.

[0040] Table 1 In summary, the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste provided by this invention uses alkaline calcium-containing industrial solid waste to treat acidic fluoride-containing wastewater. By treating waste with waste, it can not only efficiently remove fluoride ions from the wastewater and ensure that the fluoride ion concentration in the treated system stably meets the emission standards, but also has the advantages of wide availability of raw materials, simple operation, low treatment cost, adaptability to actual calcium-containing industrial solid waste and fluoride-containing industrial wastewater systems, and strong universality and significant industrial application value.

[0041] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0042] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0043] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for the green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste, characterized in that, Using calcium-containing industrial solid waste as a calcium source and flocculant, the method of treating waste with waste includes the following steps: providing fluoride-containing wastewater with pH < 7; adding treated calcium-containing industrial solid waste to the fluoride-containing wastewater; the aqueous solution of the calcium-containing industrial solid waste having pH > 7; stirring to simultaneously carry out precipitation and flocculation reactions; and obtaining fluoride-enriched precipitate and supernatant after solid-liquid separation.

2. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to claim 1, characterized in that, The fluoride-containing wastewater contains, in addition to, F - In addition, it also contains Na + Al 3+ Fe 2+ Ca 2+ K + Mg 2+ H + Cl - NO 3- SO4 2- PO4 3- At least one of the ions.

3. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to claim 1 or 2, characterized in that, The concentration of fluoride ions in the fluoride-containing wastewater is 300 mg / L to 4000 mg / L.

4. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-3, characterized in that, The pH of the fluoride-containing wastewater is less than or equal to 1.

5. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-4, characterized in that, The calcium-containing industrial solid waste includes at least one of steel slag, fly ash, carbide slag, lead-zinc tailings, papermaking sludge, or phosphogypsum; and / or includes at least one of calcium oxide, calcium chloride, or calcium hydroxide, with a Ca mass percentage ≥ 1%.

6. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-5, characterized in that, The method for preparing the treated calcium-containing industrial solid waste includes crushing, grinding, and calcining the calcium-containing industrial solid waste in advance.

7. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-6, characterized in that, The dosage should be controlled so that the molar amount of calcium in the calcium-containing industrial solid waste is 0.5 to 2 times the molar amount of fluorine in the fluorine-containing wastewater.

8. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-7, characterized in that, The precipitation and flocculation reactions are carried out at temperatures of 15°C to 35°C and pH > 7; and / or the stirring time is 1 min to 60 min; the mixture is then allowed to stand for 1 h to 12 h after stirring; the solid-liquid separation method includes filtration.

9. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-8, characterized in that, The concentration of fluoride ions in the supernatant is ≤10 mg / L.

10. The method for green co-treatment of fluoride-containing wastewater and calcium-containing industrial solid waste according to any one of claims 1-9, characterized in that, The precipitation reaction and flocculation reaction work together to remove at least one of the elements Al, Fe, and Mg contained in the calcium-containing industrial solid waste; and / or, the fluorine-enriched precipitate includes CaF2, which is purified by water washing and weak acid leaching before being utilized for resource recovery.

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