A multi-stage membrane concentration resource treatment process for tantalum-niobium hydrometallurgy fluorine-containing and ammonia-containing wastewater

Abstract

This application relates to the field of hydrometallurgical industrial wastewater treatment and resource recovery technology, and provides a resource recovery process for multi-stage membrane concentration of fluoride- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes. The process includes: multi-stage membrane concentration of the fluoride- and ammonia-containing wastewater to separate low-salinity fresh water and fluoride-containing concentrated water; mixing the fluoride-containing concentrated water with fluoride-containing mother liquor and adding a calcium-based precipitant for precipitation to obtain an ammonia-containing feed solution; subjecting the ammonia-containing feed solution to thermal deammoniation, and using low-salinity fresh water as the absorbent to absorb the released ammonia-containing gas to obtain ammonia water; and recirculating the wastewater generated after ammonia removal to the front end of the multi-stage membrane concentration treatment for internal system circulation. This application achieves low-energy, high-efficiency recovery of fluoride and ammonia resources and near-zero wastewater discharge.

Description

Technical Field

[0001] This application relates to the field of hydrometallurgical industrial wastewater treatment and resource recovery technology, specifically to a resource recovery process for multi-stage membrane concentration of fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes. Background Technology

[0002] In the hydrometallurgical process of tantalum and niobium and other chemical production processes, large amounts of alkaline wastewater rich in fluoride ions and ammonia nitrogen are often generated. Currently, there are two main technical routes for treating this type of wastewater: one is the traditional chemical precipitation method, which involves adding lime to generate calcium fluoride slag, followed by stripping or biochemical treatment of the effluent. While this method is low-cost, it results in large amounts of waste slag, low ammonia recovery rates, and difficulty in achieving efficient water reuse. The other is the membrane concentration coupled with evaporation crystallization method. For example, Chinese patent application CN118343856A discloses a process for recovering high-purity ammonium fluoride through multi-stage membrane concentration combined with low-temperature vacuum evaporation crystallization. Although this route achieves the resource recovery of fluoride and ammonia, the evaporation crystallization stage has extremely high energy consumption, and the equipment suffers severe corrosion in high-concentration fluoride-containing salt solutions. Furthermore, the introduction of external pure water or acid / alkali regulators easily disrupts the internal water balance of the system, leading to an expansion of the total wastewater volume or the accumulation of impurities, making it difficult to achieve truly stable near-zero discharge operation. Therefore, there is an urgent need to develop a resource-based treatment process that can efficiently recover fluorine and ammonia resources, significantly reduce treatment energy consumption, and maintain the internal water balance of the system. Summary of the Invention

[0003] To address the problems of high energy consumption, severe equipment corrosion, and difficulty in maintaining system water balance in existing technologies for treating fluoride and ammonia-containing wastewater, this application proposes a resource-based treatment process for fluoride and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes, which utilizes multi-stage membrane concentration to achieve low-energy, high-efficiency recovery of fluoride and ammonia resources and near-zero wastewater discharge.

[0004] To achieve the above objectives, this application adopts the following technical solution: A resource-based treatment process for multi-stage membrane concentration of fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes includes: performing multi-stage membrane concentration treatment on the fluorine- and ammonia-containing wastewater to separate low-salinity fresh water and fluorine-containing concentrated water; mixing the fluorine-containing concentrated water with fluorine-containing mother liquor and adding a calcium-based precipitant to carry out a precipitation reaction to obtain an ammonia-containing feed solution; performing thermal deammoniation treatment on the ammonia-containing feed solution and using the low-salinity fresh water as an absorbent to absorb the desorbed ammonia-containing gas to obtain ammonia water; and recirculating the wastewater generated after ammonia removal to the front end of the multi-stage membrane concentration treatment to participate in the system's internal circulation.

[0005] The aforementioned solution replaces the traditional high-energy-consumption evaporation and crystallization route with a closed-loop coupling mechanism of "multi-stage membrane concentration and volume reduction - combined chemical defluorination - thermal desorption and ammonia removal - desalination absorption". On the one hand, multi-stage membrane concentration separates wastewater into low-salinity desalinated water and fluoride-containing concentrated water, achieving graded enrichment of pollutants. On the other hand, the low-salinity desalinated water produced by membrane concentration is cleverly used directly as the absorbent in the thermal desorption and ammonia removal stage, avoiding system water volume expansion caused by the introduction of external fresh water. At the same time, the fluoride-containing concentrated water and fluoride-containing mother liquor are treated together, improving the precipitation efficiency of fluoride. The wastewater after ammonia removal is recycled to the front end, constructing a dual-circulation system of "ammonia closed loop + water closed loop", thereby significantly reducing the energy consumption per ton of water treated while maintaining the material and water balance within the system.

[0006] Preferably, the multi-stage membrane concentration treatment includes a first-stage reverse osmosis and a second-stage reverse osmosis in series; the first-stage reverse osmosis produces first-stage desalinated water and first-stage concentrated water, and the first-stage concentrated water enters the second-stage reverse osmosis to produce second-stage concentrated water; the fluoride-containing concentrated water is the second-stage concentrated water, and the low-salt desalinated water is the first-stage desalinated water; the first-stage desalinated water is divided into two parts, one part is used as recycled water, and the other part is used as the absorbent.

[0007] This preferred solution maximizes the concentration ratio while ensuring the quality of the produced water through a two-stage reverse osmosis cascade concentration design. In particular, the primary freshwater is used separately for different purposes, which not only meets the reuse requirements of the upstream washing section, but also provides sufficient and pure absorbent for the ammonia removal stage. This internal coupling design of material flow fundamentally eliminates the dependence on external fresh water sources and further enhances the system's self-balancing ability.

[0008] Preferably, the fluorine-containing mother liquor is a tantalum-niobium mother liquor obtained after precipitation reaction and solid-liquid separation of tantalum-niobium solution; the step of mixing the fluorine-containing concentrated water with the fluorine-containing mother liquor and adding the calcium-based precipitant to carry out the precipitation reaction includes: after the tantalum-niobium mother liquor is precisely filtered, it is mixed with the fluorine-containing concentrated water, and the calcium-based precipitant is added to carry out a neutralization precipitation reaction.

[0009] This preferred solution achieves the synergistic treatment of two high-fluoride wastewater streams by combining the tantalum-niobium mother liquor from the front-end process with the fluoride-containing concentrate from the back-end membrane concentration. The precision filtration step effectively removes tiny suspended particles from the mother liquor, preventing them from interfering with subsequent precipitation reactions and clogging equipment. Combined precipitation not only reduces the number of treatment units and investment costs but also utilizes any residual alkaline substances in the mother liquor to assist in pH adjustment, reducing the consumption of calcium-based precipitants.

[0010] Preferably, the operating pressure of the first-stage reverse osmosis is 5-6 MPa; the fluoride ion concentration in the first-stage concentrate is 15-20 g / L; the operating pressure of the second-stage reverse osmosis is 7-8 MPa; the fluoride ion concentration in the second-stage concentrate is 30-40 g / L, and the pH value is 8-9; and the fluoride ion concentration in the first-stage desalination is less than 0.1 g / L, and the pH value is 8-9.

[0011] This preferred scheme defines the critical operating window of the membrane concentration system. Within this pressure range, the first-stage reverse osmosis can stably produce low-fluoride desalinated water that meets the absorbent requirements while ensuring sufficient flux; the first-stage concentrate reaches a fluoride concentration of 15-20 g / L, and after further concentration by the second-stage reverse osmosis, the second-stage concentrate reaches a fluoride concentration of 30-40 g / L. This creates high supersaturation conditions for subsequent calcium-based precipitation, which is conducive to the formation of larger-particle-size calcium fluoride crystals that are easy to settle and separate, thereby improving the fluoride recovery rate and the quality of by-products.

[0012] Preferably, the calcium-based precipitant is lime, and lime powder with a purity greater than or equal to 95% is used; the fluoride ion concentration in the tantalum-niobium mother liquor is 30-60 g / L, and the pH value is 8-9.

[0013] This preferred scheme clarifies the specific form and ratio of the calcium-based precipitant. Using high-purity lime powder ensures a sufficient supply of active ingredients, effectively raising the pH value of the waste liquid at the bottom of the tower and saving reagent costs; the reaction is exothermic, providing "preheating" energy: the large amount of heat released by the digestion reaction (approximately 64.9 kJ / mol) can instantly raise the wastewater temperature by 15-30°C. This means that the raw water temperature before entering the stripping tower is higher, saving some steam consumption and reducing overall energy consumption.

[0014] Preferably, the thermal desorption ammonia removal process is steam stripping ammonia removal; after adding lime powder for precipitation reaction, the pH value of the feed solution increases to 10-12; the ammonia-containing gas removed is condensed and then absorbed by the low-salt fresh water circulation to obtain ammonia water, and the ammonia water is reused in the precipitation reaction section.

[0015] This preferred solution uses steam stripping as a method for ammonia removal, which has advantages over membrane distillation or stripping methods in terms of high mass transfer efficiency and large processing capacity. The key lies in utilizing the primary desalinated water produced by the aforementioned multi-stage membrane concentration in a circulating absorption tower. The resulting ammonia water has high purity and few impurities, and can be directly reused in the upstream tantalum-niobium precipitation section. This achieves a closed-loop recycling of ammonia resources within the production process, completely cutting off the path of ammonia nitrogen emissions into the environment.

[0016] Preferably, the steam stripping ammonia removal is carried out in a stripping ammonia removal tower, with a tower bottom temperature of 95-105℃ and an operating pressure of 0.02-0.05MPa; the volume ratio of steam to ammonia-containing liquid is 1:3-1:5, and the residence time of the ammonia-containing liquid in the tower is 1.5-2.5 hours.

[0017] This preferred scheme optimizes the operating parameters of the stripping tower. Operating under slightly positive pressure (0.02-0.05 MPa) effectively avoids the severe flashing and cavitation corrosion problems caused by the lower boiling point of high-concentration fluoride salt solutions under negative pressure conditions, thus extending the equipment's service life. The specific combination of gas-liquid ratio and residence time ensures efficient removal of free ammonia while avoiding energy waste caused by excessive stripping, achieving an optimal balance between ammonia removal efficiency and operating costs.

[0018] Preferably, the fluoride- and ammonia-containing wastewater undergoes pretreatment and ultrafiltration before the multi-stage membrane concentration treatment to obtain ultrafiltration water and ultrafiltration concentrate; the ultrafiltration water undergoes the multi-stage membrane concentration treatment; the wastewater generated after ammonia removal is returned to the front end of the pretreatment and ultrafiltration treatment after deep filtration; the ultrafiltration concentrate is divided into reflux liquid and discharge liquid after deep filtration; the reflux liquid is returned to the front end of the pretreatment and ultrafiltration treatment, and the discharge liquid is discharged after adjusting the pH value.

[0019] This optimized design establishes a complete closed-loop water circulation path for the system. After ammonia removal, the wastewater and ultrafiltration concentrate are largely recycled after deep filtration, with only a very small amount meeting standards for external discharge, ensuring a wastewater internal recycling rate of ≥98% for the entire system. This design not only minimizes fresh water consumption and wastewater discharge but also ensures the quality of the recycled water through precision filtration, preventing suspended solids and colloids from accumulating at the front end and causing membrane module fouling, thus maintaining long-term stable operation.

[0020] Preferably, the water quality indicators of the wastewater generated after ammonia removal and returned to the front end of the pretreatment and ultrafiltration treatment are: fluoride ion concentration less than 0.02 g / L, ammonia nitrogen concentration less than 0.02 g / L, and suspended solids concentration less than 150 mg / L; the pH value of the effluent is adjusted to 7.0-7.5; and the wastewater internal recycling rate of the entire system is greater than or equal to 98%.

[0021] This optimized scheme quantifies the water quality control standards for the reflux water. Strictly controlling the levels of fluoride, ammonia, and suspended solids in the reflux solution is a crucial prerequisite for preventing scaling and fouling of the upstream ultrafiltration and reverse osmosis membranes. Simultaneously, precisely adjusting the pH of the effluent to the neutral range ensures the compliance of the final effluent. An internal recycling rate exceeding 98% signifies that this process truly achieves the near-zero discharge target for industrial wastewater.

[0022] Preferably, the resource recovery process is applied to fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes; the calcium fluoride byproduct produced by the precipitation reaction meets the secondary standard for calcium fluoride; and the mass concentration of the ammonia water obtained is 18%-25%.

[0023] This optimized solution specifically applies the general process to the tantalum-niobium hydrometallurgical scenario and clarifies the quality standards for the resource-based products. The produced calcium fluoride reaches 90%, possessing marketable value; the recovered 18%-25% concentration ammonia fully meets the process requirements for the tantalum-niobium hydroxide precipitation reaction. This demonstrates that the process not only solves environmental problems but also creates significant economic benefits, achieving a balance between environmental governance and resource value enhancement.

[0024] Beneficial effects: 1. Full-component resource utilization: This process, through the coupling of "lime neutralization + stripping and deammoniation", converts fluoride ions in wastewater into calcium fluoride by-products that meet quality standards, and converts ammonia nitrogen in wastewater into 18%-25% ammonia water that can be directly recycled in the tantalum-niobium precipitation section, thus turning pollutants into valuable resources.

[0025] 2. Near-zero wastewater discharge: This process constructs a closed-loop system of "pretreatment-membrane concentration-neutralization and deammoniation-filtration reflux". A large amount of deammoniation wastewater and ultrafiltration concentrate are returned to the front end of the system after deep filtration. The wastewater internal recycling rate of the entire system reaches more than 98%, which greatly reduces the consumption of fresh water and the amount of wastewater discharged.

[0026] 3. Low operating cost and stable operation: This application abandons the high-energy-consuming high-temperature vacuum evaporation crystallization process and adopts the mature combination of "two-stage RO membrane physical concentration + steam stripping deammoniation". The stripping process is carried out under a slight positive pressure, which not only effectively avoids the strong corrosion of the equipment by high-concentration fluoride salt solution, but also significantly reduces the energy consumption per ton of water treated. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the process flow for the resource-based treatment of fluoride- and ammonia-containing wastewater according to an embodiment of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] Example 1: This example provides a resource-based treatment process for multi-stage membrane concentration of fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes, such as... Figure 1 As shown, this process achieves efficient recovery of ammonia fluoride resources and near-zero wastewater discharge through an internal coupling mechanism between materials and energy. Specifically, this resource recovery process includes the following steps: Step S100 involves multi-stage membrane concentration treatment of the fluoride- and ammonia-containing wastewater to separate low-salinity freshwater and fluoride-containing concentrated water. In this embodiment, the multi-stage membrane concentration treatment includes a series of first-stage and second-stage reverse osmosis systems. The first-stage reverse osmosis system operates at a pressure of 5-6 MPa, producing first-stage freshwater and first-stage concentrated water. The first-stage concentrated water enters the second-stage reverse osmosis system at a pressure of 7-8 MPa, producing second-stage concentrated water. The fluoride ion concentration in the first-stage concentrated water is 15-20 g / L, and the fluoride ion concentration in the second-stage concentrated water is 30-40 g / L, with a pH value of 8-9. The fluoride ion concentration in the first-stage freshwater is less than 0.1 g / L, with a pH value of 8-9. The first-stage freshwater is divided into two parts: one part is used as reclaimed water, and the other part is used as absorbent.

[0031] In step S200, the fluoride-containing concentrated water and the fluoride-containing mother liquor are mixed, and a calcium-based precipitant is added to carry out a precipitation reaction, resulting in an ammonia-containing feed solution. The fluoride-containing mother liquor is obtained from tantalum-niobium solution after precipitation reaction and solid-liquid separation. After precision filtration, the tantalum-niobium mother liquor is mixed with secondary concentrated water, and a calcium-based precipitant is added to carry out a neutralization and precipitation reaction. The calcium-based precipitant is lime, using lime powder with a purity greater than or equal to 95%. The fluoride ion concentration in the tantalum-niobium mother liquor is 30-60 g / L, and the pH value is 8-9. After adding lime slurry, the pH value of the feed solution rises to 10-12, creating suitable alkaline conditions for subsequent stripping and deammoniation.

[0032] Step S300, as follows Figure 1As shown, an ammonia-containing feed solution undergoes thermal desorption and ammonia removal treatment, using low-salt fresh water as the absorbent to absorb the removed ammonia-containing gas, producing ammonia water. The thermal desorption and ammonia removal process is a steam stripping process carried out in a stripping ammonia removal tower. The tower bottom temperature is 95-105℃, the operating pressure is 0.02-0.05MPa, the volume ratio of steam to ammonia-containing feed solution is 1:3-1:5, and the residence time of the ammonia-containing feed solution in the tower is 1.5-2.5 hours. It should be noted that after adding lime slurry in step S200 for neutralization and precipitation, the pH value of the feed solution rises to 10-12, creating suitable alkaline conditions for subsequent stripping ammonia removal, ensuring that ammonia nitrogen exists mainly in the form of free ammonia, thus improving stripping efficiency. The removed ammonia-containing gas is condensed and then recycled to the absorption tower by primary fresh water to produce ammonia water, which is then reused in the precipitation reaction section.

[0033] Step S400, as follows Figure 1 As shown, the wastewater generated after ammonia removal is recycled to the front end of the multi-stage membrane concentration treatment to participate in the system's internal circulation. Before multi-stage membrane concentration treatment, the fluoride- and ammonia-containing wastewater undergoes pretreatment and ultrafiltration to obtain ultrafiltered water and ultrafiltration concentrate. The ultrafiltration water undergoes multi-stage membrane concentration treatment; the wastewater generated after ammonia removal is deep filtered and then recycled to the front end of the pretreatment and ultrafiltration treatment; the ultrafiltration concentrate is deep filtered and divided into reflux and effluent; the reflux is recycled to the front end of the pretreatment and ultrafiltration treatment, and the effluent is discharged after pH adjustment. The water quality indicators of the wastewater generated after ammonia removal recycled to the front end of the pretreatment and ultrafiltration treatment are: fluoride ion concentration less than 0.02 g / L, ammonia nitrogen concentration less than 0.02 g / L, and suspended solids concentration less than 150 mg / L; the pH of the effluent is adjusted to 7.0-7.5; the overall wastewater internal circulation utilization rate is greater than or equal to 98%.

[0034] Example 2: Based on the aforementioned examples, this example further applies the resource-based treatment process to a specific scenario involving fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes, to verify the feasibility and economic value of the technical solution in actual industrial production. Combined with... Figure 1 The process flow shown should be understood as follows: Although this embodiment uses tantalum-niobium hydrometallurgy as an example for detailed description, the scope of protection of this application is not limited to this specific industry. Any chemical or metallurgical process that generates wastewater containing fluorine and ammonia with similar components should be considered to fall within the scope of protection of this application as long as it adopts the material coupling and double closed-loop circulation process described in the foregoing embodiment of this application.

[0035] In this application scenario, the calcium fluoride byproduct produced by the precipitation reaction meets the secondary standard for calcium fluoride. Specifically, through the combined precipitation strategy and strict reagent control described in Example 1, the generated calcium fluoride crystals have high purity and few impurities. After drying, the CaF2 content stably reaches over 95%, meeting the quality requirements of industrial-grade secondary calcium fluoride. This gives it market value as a direct chemical raw material, realizing the resource-based value-added of waste residue. Simultaneously, the ammonia solution produced has a mass concentration of 18%-25%. This concentration range perfectly matches the process requirements of the tantalum-niobium hydroxide precipitation reaction, allowing for direct reuse in the front-end reaction tank without additional concentration or preparation. This not only saves on ammonia purchase costs but also avoids the risk of introducing impurity ions from purchased ammonia, which could affect the quality of tantalum-niobium products.

[0036] To more intuitively demonstrate the operational effectiveness of the process described in this application, a full-process material balance calculation is performed below using actual operating data from a tantalum-niobium hydrometallurgical plant. The plant's reaction section produces 2000 m³ of wash water daily, with initial water quality indicators of fluoride ion concentration of 5 g / L and pH value of 8.5. First, this wash water enters a pretreatment and ultrafiltration unit for treatment, separating 1800 m³ of ultrafiltration water and 200 m³ of ultrafiltration concentrate. The ultrafiltration water is then sent to a first-stage reverse osmosis unit, producing 1600 m³ of primary desalinated water (fluoride ion concentration of 0.05 g / L, pH value 8.5) and 200 m³ of primary concentrate (fluoride ion concentration of 15 g / L, pH value 8.5) under an operating pressure of 5.5 MPa. The primary concentrate continues to enter a second-stage reverse osmosis unit for further concentration, ultimately yielding 90 m³ of secondary concentrate (fluoride ion concentration of 35 g / L, pH value 8.5) under an operating pressure of 7.5 MPa. During this process, the primary freshwater is utilized in stages: 1200 m³ is returned to the washing section as washing water for reuse, replacing an equal amount of fresh tap water; the remaining 400 m³ is transported to the condensation absorption unit as absorbent for later use.

[0037] Meanwhile, the 500 m³ tantalum-niobium mother liquor (fluoride ion concentration 45 g / L, pH 8.5) produced after ammonia precipitation and pressure filtration of the front-end tantalum-niobium solution is treated by a precision filter and then combined with the aforementioned 90 m³ secondary concentrated water into the neutralization reactor. Under stirring conditions, lime powder with a purity ≥95% is added to the reactor for neutralization and precipitation reaction. After the reaction is completed, the ammonia-containing liquid is sent to a stripping ammonia removal tower for steam stripping under a slightly positive pressure condition of 100℃ at the tower bottom temperature and 0.03 MPa. The stripped ammonia-containing gas is condensed and then absorbed in an absorption tower using the aforementioned 400 m³ primary fresh water to stably produce ammonia water with a mass concentration of 20%, which is entirely recycled to the tantalum-niobium solution precipitation reaction section, forming a stable closed-loop ammonia cycle.

[0038] Regarding water circulation, the wastewater after stripping and ammonia removal is filtered through a solid-liquid separation unit to remove crude calcium fluoride with a water content of approximately 35%. The clarified liquid is then treated by a deep filtration unit, achieving water quality indicators of less than 0.02 g / L fluoride ion concentration, less than 0.02 g / L ammonia nitrogen concentration, and less than 150 mg / L suspended solids concentration. All of this water is then recycled back to the front end of the pretreatment and ultrafiltration units for internal system circulation. For the 200 m³ of ultrafiltration concentrate generated in the pretreatment stage, after deep filtration, approximately 164 m³ of clarified liquid is also recycled back to the front end of the system. Only 36 m³ of clarified liquid enters the pH adjustment tank, where the pH is adjusted to 7.2 with sulfuric acid before being discharged as qualified water. Calculations show that this system processes 2000 m³ of washing water daily, with a final discharge volume of only 36 m³. The overall wastewater internal circulation rate reaches 98.2%, truly achieving near-zero discharge of tantalum-niobium hydrometallurgical wastewater. This actual operational data fully demonstrates that the process described in this application can not only efficiently recover fluoride and ammonia resources when treating high-concentration fluoride and ammonia wastewater, but also significantly reduce fresh water consumption and wastewater treatment costs while maintaining system water balance, thus demonstrating significant industrial application prospects and promotional value.

[0039] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Those skilled in the art should understand that the specific process parameters, equipment selection, material ratios, and process sequences described in the foregoing embodiments are preferred examples listed to clearly illustrate the technical solution of this application, and are not intended to limit this application. Within the scope of the technology disclosed in this application, any equivalent substitution, modification, combination, or omission of the above technical features based on the inventive concept of this application, as long as it can achieve the same or similar technical effects, should be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A resource-based treatment process for multi-stage membrane concentration of fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes, characterized in that, include: Fluorine- and ammonia-containing wastewater is subjected to multi-stage membrane concentration treatment to separate low-salt fresh water and fluorine-containing concentrated water. The fluorine-containing concentrated water is mixed with fluorine-containing mother liquor, and a calcium-based precipitant is added to carry out a precipitation reaction to obtain an ammonia-containing feed solution. The ammonia-containing feed solution is subjected to thermal desorption and ammonia removal treatment, and the low-salt fresh water is used as an absorbent to absorb the ammonia-containing gas released to obtain ammonia water. The wastewater generated after ammonia removal is recycled to the front end of the multi-stage membrane concentration treatment to participate in the internal circulation of the system.

2. The resource recovery process according to claim 1, characterized in that, The multi-stage membrane concentration treatment includes a first-stage reverse osmosis and a second-stage reverse osmosis connected in series; the first-stage reverse osmosis produces first-stage desalinated water and first-stage concentrated water, and the first-stage concentrated water enters the second-stage reverse osmosis to produce second-stage concentrated water; the fluoride-containing concentrated water is the second-stage concentrated water, and the low-salt desalinated water is the first-stage desalinated water; the first-stage desalinated water is divided into two parts, one part is used as reclaimed water, and the other part is used as the absorbent.

3. The resource recovery process according to claim 1, characterized in that, The fluorine-containing mother liquor is a tantalum-niobium mother liquor obtained after precipitation reaction and solid-liquid separation of tantalum-niobium solution; the step of mixing the fluorine-containing concentrated water with the fluorine-containing mother liquor and adding the calcium-based precipitant to carry out the precipitation reaction includes: after the tantalum-niobium mother liquor is precisely filtered, it is mixed with the fluorine-containing concentrated water, and the calcium-based precipitant is added to carry out a neutralization precipitation reaction.

4. The resource recovery process according to claim 2, characterized in that, The operating pressure of the first-stage reverse osmosis is 5-6 MPa; the fluoride ion concentration in the first-stage concentrate is 15-20 g / L, and the pH value is 8-9; the fluoride ion concentration in the second-stage concentrate is 30-40 g / L, and the pH value is 8-9; the fluoride ion concentration in the first-stage desalination is less than 0.1 g / L, and the pH value is 8-9.

5. The resource recovery process according to claim 3, characterized in that, The calcium-based precipitant is lime, with a purity greater than or equal to 95%; the fluoride ion concentration in the tantalum-niobium mother liquor is 30-60 g / L, and the pH value is 8-9.

6. The resource recovery process according to claim 1, characterized in that, The pyrolysis and ammonia removal process is a steam stripping process; after the addition of calcium-based precipitant for precipitation reaction, the pH value of the feed solution increases to 10-12; the ammonia-containing gas removed is condensed and then absorbed by the low-salt fresh water circulation to obtain ammonia water, which is then reused in the precipitation reaction section.

7. The resource recovery process according to claim 6, characterized in that, The steam stripping and ammonia removal are carried out in a stripping and ammonia removal tower, with a tower bottom temperature of 95-105℃ and an operating pressure of 0.02-0.05MPa; the volume ratio of steam to ammonia-containing liquid is 1:3-1:5, and the residence time of the ammonia-containing liquid in the tower is 1.5-2.5 hours.

8. The resource recovery process according to claim 1, characterized in that, The fluoride- and ammonia-containing wastewater undergoes pretreatment and ultrafiltration before being subjected to the multi-stage membrane concentration treatment to obtain ultrafiltration water and ultrafiltration concentrate; the ultrafiltration water is then subjected to the multi-stage membrane concentration treatment. The wastewater generated after ammonia removal is returned to the front end of the pretreatment and ultrafiltration processes after deep filtration. The ultrafiltration concentrate is separated into reflux liquid and discharge liquid after deep filtration; the reflux liquid is returned to the front end of the pretreatment and ultrafiltration treatment, and the discharge liquid is discharged after adjusting the pH value.

9. The resource recovery process according to claim 8, characterized in that, The water quality indicators of the wastewater generated after ammonia removal and returned to the front end of the pretreatment and ultrafiltration treatment are: fluoride ion concentration less than 0.02 g / L, ammonia nitrogen concentration less than 0.02 g / L, and suspended solids concentration less than 150 mg / L; the pH value of the effluent is adjusted to 7.0-7.

5. The wastewater recycling rate of the entire system is greater than or equal to 98%.

10. The resource recovery process according to claim 1, characterized in that, The resource-based treatment process is applied to fluorine- and ammonia-containing wastewater from tantalum-niobium hydrometallurgical processes; the calcium fluoride byproduct CaF2 produced by the precipitation reaction is ≥90%; and the mass concentration of the ammonia water obtained is 18%-25%.

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