Methods for bacterial leaching of uranium ore with high fluorine content

Abstract

This invention relates to the field of mineral utilization, specifically to a method for bacterial leaching of high-fluorine-content uranium ore. The method involves crushing the high-fluorine-content uranium ore and packing it into columns or heaps to obtain a ore heap. The ore heap is then sprayed with an acidic solution. The collected leachate is subjected to uranium adsorption treatment, and the adsorption tailings are defluorinated and recycled back to the spraying process. Subsequently, bacteria are implanted into the ore heap. Then, a spray solution containing boric acid and other acids is used for bacterial leaching. The collected bacterial leachate is subjected to uranium adsorption treatment, and the adsorption tailings are recycled back to the bacterial leaching process. This invention can process uranium ore with a fluorine content of 5% or higher while still exhibiting excellent uranium leaching efficiency and effect.

Description

Technical Field

[0001] This invention belongs to the fields of chemical engineering and hydrometallurgical technology, and specifically relates to a method for bacterial leaching of uranium ore with high fluorine content. Background Technology

[0002] Bacterial leaching of uranium from refractory or low-grade uranium ores is a technologically feasible, resource-saving, and environmentally friendly application technology with promising prospects for low-grade, complex, and refractory uranium ores. It can shorten the leaching cycle and improve the leaching rate. Iron-sulfur oxidizing bacteria are commonly used, but bacterial activity is one of the key factors affecting the leaching effect. Many factors influence bacterial activity, among which the concentration of harmful ions in the solution is a major one. Studies have shown that F dissolved from the ore... - This will severely inhibit bacterial growth. This is because fluoride has a small ionic radius, can damage cell membranes, and is toxic to protoplasts, thus inhibiting the synthesis of intracellular proteins and DNA. In uranium ore bacterial leaching systems, the environmental pH is generally below 2.0, creating a pH gradient between the intracellular and extracellular spaces. Fluoride transmembranely exists as hydrogen fluoride (ionic form F). - The passive diffusion in the form of F resulted in a large amount of F - It enters bacterial cells, thus severely affecting the biological activity of iron-sulfur oxidizing bacteria.

[0003] Because fluorine is a mineral-loving element, many uranium ores often contain large amounts of fluorite, fluorapatite, and other fluorine-containing minerals. These fluorine-containing minerals are highly soluble under acidic conditions. Therefore, in the bioleaching of fluorine-containing ores, fluorine... - Inhibition of iron-sulfur oxidizing bacteria will reduce leaching efficiency. Currently, the main methods to address this problem are flotation of fluoride-containing ores for fluoride removal or removal of fluoride ions from the leaching solution. These methods have high fluoride removal efficiency, but are often prohibitively expensive or involve complex processes. In addition, bacterial tolerance acclimation is currently the primary method, but regardless of the acclimation method, there is an upper limit to bacterial tolerance to fluoride. For example, Liu Yajie (Nonferrous Mining and Metallurgy, 2006) found that acclimation can increase bacterial tolerance to fluoride to 1400 mg / L, with a maximum [F... － This bacterium can also grow and develop in an acidified solution with a concentration of 1400 mg / L after a slightly longer lag phase, but it cannot completely oxidize Fe. 2+ The process takes as long as 96 hours, making it difficult to apply in actual processes.

[0004] Chinese patent document CN104745498A discloses a fluoride-resistant leaching bacterium and its application in a highly efficient leaching process for high-fluoride uranium ore. The process involves adding aluminum sulfate to the acidification solution to optimize c[Al] 3+ ]:c[F - ] = 1, because F in the acidification solution- The content of fluorine is the highest, leading to the need to add a large amount of aluminum sulfate. Therefore, it is only suitable for ores with a fluorine content of less than 5%, and cannot be used for high-fluorine uranium ores with a fluorine content of more than 5%. Furthermore, due to the high fluorine content of fluorine... - It will also react with Fe in the solution 3+ The formation of complex ions allows for the free Fe in the leachate. 3+ The significantly reduced content leads to a substantial decrease in the potential of the leachate, necessitating the addition of a large amount of Fe ions. Furthermore, pH is a crucial factor affecting the complexation of fluoride and aluminum ions. When the pH is low (e.g., less than 1.8), aluminum ions form clusters with water molecules, making it difficult for fluoride ions to complex with them. Therefore, pH adjustment is necessary before complexation, bringing the pH to 1.8–2.5.

[0005] It is evident that there are still many shortcomings in the current approach to bacterial leaching of uranium ores with high fluorine content. When the fluorine content in uranium ore is greater than 5%, it is difficult to use bacterial leaching technology. In particular, with the increasing environmental protection requirements, there is still no wastewater-free bacterial leaching technology for uranium ores with high fluorine content. Summary of the Invention

[0006] To address the problem of difficulty in bacterial leaching of uranium ore with high fluoride content, the present invention aims to provide a method for bacterial leaching of uranium ore with high fluoride content, thereby solving the impact of high fluoride content on bacteria and improving the leaching efficiency and effect of uranium from uranium ore with high fluoride content.

[0007] When the fluorine content in uranium ore reaches 5% or more, the high F content significantly inhibits bacterial activity and noticeably affects the leaching effect. To address this problem, the present invention provides the following improvement:

[0008] The method for bacterial leaching of high-fluorine uranium ore includes the following steps:

[0009] Step (1): Acid pre-soaking treatment

[0010] After crushing the high-fluorine-content uranium ore, it is loaded into pillars or piled up to obtain a ore pile. The ore pile is sprayed with an acidic spraying liquid. The collected leaching liquid is subjected to uranium adsorption treatment. The adsorption tail liquid is defluorinated and then recycled back to the spraying process.

[0011] Step (2):

[0012] Bacteria were implanted into the ore pile in step (1); then a spray solution containing boric acid and acid was used to spray the bacteria for leaching. The collected bacterial leaching solution was subjected to uranium adsorption treatment, and the adsorption tail liquid was recycled back to the bacterial leaching process.

[0013] To address the problem of unsatisfactory bacterial leaching effects caused by high fluorine content in uranium ore, this invention provides a two-stage synergistic bacterial acid leaching process involving a first-stage acid leaching pretreatment and boric acid assistance. This unexpected synergy can solve the problem of bacterial leaching toxicity caused by high fluorine content and significantly improve the leaching efficiency and effect of high-fluorine uranium ore.

[0014] The process of this invention can theoretically be applied to uranium ore with any F content, but considering the maximization of the technological value, it is particularly suitable for uranium ore with an F content of 5 wt.% or higher, and further, for uranium ore with an F content of 5–10 wt.%. In this invention, the U grade of the uranium ore is not particularly required, for example, it can be 0.5–3 wt.%.

[0015] In step (1) of this invention, the high-fluorine-content uranium ore is crushed to any particle size between -4 and -20 mm.

[0016] In this invention, in step (1), the acid in the spray solution is sulfuric acid;

[0017] Preferably, during the spraying process, the solute concentration of acid in the spray solution is 20–100 g / L, and more preferably 40–60 g / L;

[0018] Preferably, the daily spraying time is 12–24 hours, and the spraying intensity is 10–50 L / (m²). 2 More preferably, the daily spraying time is 20–24 hours, and the spraying intensity is 20–25 L / (m²). 2 ·h).

[0019] In this invention, in step (1), uranium is adsorbed using resin, wherein the resin includes at least one of D363B macroporous resin, D201 macroporous resin, 201*7 resin, D263 macroporous resin, and D301 macroporous resin.

[0020] In this invention, the defluorination process includes neutralizing the pH of the adsorption tail liquid to 6-9 (preferably 8-9) using lime and a solid-liquid separation step.

[0021] In this invention, the defluorinated solution (defluorinated liquid) can be supplemented with acid as needed and used as a spraying liquid for circulating spraying of ore piles. Specifically, the acid concentration of the spraying liquid during the circulating spraying stage is controlled at 20–100 g / L, the daily spraying time is controlled at 12–24 h, and the spraying intensity is controlled at 10–50 L / (m²). 2 ·h).

[0022] In step (1) of this invention, the pH value of the effluent from the circulating spray is less than 2.0, thus ending step (1) and proceeding to step (2). In this invention, the circulating spray time in step (1) can be 5 to 15 days, and considering the treatment efficiency, it can be further extended to 8 to 10 days.

[0023] In this invention, under the first stage of acid leaching treatment in step (1), the subsequent second stage of boric acid-assisted bacterial leaching can unexpectedly achieve synergy, solve the problem of bacterial leaching toxicity caused by high F, and obtain excellent bacterial leaching efficiency and effect.

[0024] In this invention, the bacterial species can be well-known, for example, it can be one or more of Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans.

[0025] In this invention, the bacteria are domesticated bacteria, preferably bacteria domesticated from high-fluorine-content uranium ore. The domestication method for the bacterial strains in this invention can be of common knowledge.

[0026] In this invention, the bacteria's tolerance to fluoride ions is ≥300 mg / L, preferably 300–1500 mg / L, and more preferably 500–600 mg / L. Thanks to the combination of the aforementioned processes, the process of this invention does not have stringent requirements on the F-tolerance of the bacterial strain, and can achieve good bacterial leaching effects under relatively relaxed F-tolerance conditions.

[0027] In step (2) of this invention, the first spray solution containing boric acid and acid can be used to spray the ore pile after step (1) in the first stage to obtain a bacterial leachate. The first adsorption tail liquid obtained by the first bacterial leachate after U adsorption treatment is supplemented with boric acid, acid and other components as needed and used as the spray solution for the next spray treatment. This process is repeated.

[0028] In this invention, the acid in step (2) is sulfuric acid;

[0029] In this invention, during the bacterial leaching process in step (2), the concentration of acid in the spray solution is controlled to be 5–20 g / L; the concentration of boric acid is less than or equal to 10 g / L. In this invention, the concentration of boric acid in the spray solution during the first spraying stage is controlled to be 1–10 g / L, and the amount of boric acid added to the spray solution during the subsequent cyclic spraying stage is 3.9–5 times the molar amount of fluorine in the adsorption tail liquid.

[0030] In this invention, water-soluble ferrous salts can be added to the spray solution as needed to control the total iron ion concentration in the bacterial leachate to ≥3g / L.

[0031] In this invention, in step (2), the pH of the leachate is controlled at 1.2–2.0, the daily spray liquid-to-solid ratio is 1–3:1, the daily spraying time is 12–24 h (preferably 12–16 h), and the spraying intensity is 10–50 L / (m²). 2 ·h), preferably 15~25L / (m 2 ·h).

[0032] In this invention, in step (2), uranium is adsorbed using resin, wherein the resin includes at least one of D363B macroporous resin, D201 macroporous resin, 201*7 resin, D263 macroporous resin, and D301 macroporous resin.

[0033] Preferably, the uranium adsorption tail liquid is reused in the bacterial leaching process.

[0034] In this invention, the uranium concentration in the bacterial leachate is stably reduced to <30mg / L, or the uranium leaching rate is greater than 90%, when the cyclic spraying is stopped. After emptying the reactor, the reactor is washed with clean water, and the wash water can be used as the process water for the next column. Finally, the column is unloaded, and the uranium content is analyzed. The tailings are discarded.

[0035] In this invention, the water used in the leaching stage can be either cleaning water or recycled process water from the process.

[0036] The advantages of this invention are:

[0037] This invention provides a two-stage synergistic bacterial acid leaching process involving a single acid leaching stage and boric acid assistance. This process effectively addresses the bacterial leaching toxicity problem caused by high fluoride (F) content, significantly improving the leaching efficiency and effect of high-F uranium ore. The method of this invention can increase the fluoride content of bacterially leached uranium ore from the current approximately 0.2-5% to over 5%, without requiring wastewater discharge.

[0038] Compared to the commonly used Al ions as complexes for F ions, this invention uses boric acid as a complex for fluoride ions. Firstly, it allows for direct complexation under conditions where the pH is less than 1.8. Secondly, BF4... - Complex ions are more stable and can convert Fe 3+ Release it to ensure that the potential during the leaching process is not affected.

[0039] This invention is highly practical, has a high resource recovery rate, low overall processing cost, is simple and feasible to operate, and is easy to industrialize. Attached Figure Description

[0040] Figure 1 This is a process flow diagram of the present invention; Detailed Implementation

[0041] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited thereto.

[0042] In this invention, the fluorine in the high-fluorine uranium ore mainly exists in the form of calcium fluoride or fluorapatite, while the uranium mainly exists in the form of uranium rock, pitchblende, or crystalline uranium ore. The fluorine content can reach over 5%. Conventional stirred leaching or heap leaching processes require the use of large amounts of chemical oxidants, resulting in high production costs, complex processes, and difficulty in reusing process water. However, bacterial leaching can enhance the leaching process, save reagent consumption, and improve uranium recovery. Therefore, this invention provides a combined process of a first-stage circulating acid treatment and a second-stage circulating acid treatment assisted by boric acid. In this invention, the first-stage and second-stage circulating acid treatments can be conventional column leaching methods.

[0043] One exemplified embodiment of the present invention includes the following steps:

[0044] (1) Ore crushing: After crushing the high-fluorine-containing uranium ore to a certain particle size, it is loaded into columns or piles.

[0045] (2) Acid pretreatment stage: Use clean water or process water to prepare a sulfuric acid solution of a certain concentration and spray it on the ore pile. Adsorb uranium in the leaching liquid. After defluorination treatment of the adsorption tail liquid, add sulfuric acid to circulate and spray the ore pile until the pH value of the effluent is less than 2.0.

[0046] (3) Microbial inoculation stage: The microbial strains used are first cultured and acclimatized in the laboratory with high fluorine uranium ore. When their tolerance to fluoride ions increases to a certain level, the microbial liquid is expanded and cultured in a bioreactor or biological oxidation tank. The cultured high-activity microbial liquid is sprayed onto the ore pile after acid pretreatment and the microbial inoculation is carried out on the ore pile.

[0047] (4) Process water circulation spraying stage: For the ore piles that have completed bacterial inoculation, process water is used to prepare a sulfuric acid solution of a certain concentration for circulating spraying of the ore piles. During this period, based on the content of fluorine and iron ions in the leaching solution of each spraying and the activity of bacteria in the ore piles, boric acid is added to complex fluorine, and a small amount of ferrous sulfate is added as needed to maintain a certain ferric content. The purpose is to ensure the activity of bacteria in the ore piles. The leachate is returned for use after uranium adsorption by ion exchange.

[0048] (5) Washing the slag with clean water: When the uranium concentration in the leaching solution decreases to a certain level, or the uranium leaching rate meets the requirements, the spraying is stopped. After emptying the stack, the stack is washed with clean water. The wash water can be used as the process water for the next column. Finally, the column is unloaded and the uranium content is analyzed. The tailings are discarded.

[0049] The specific steps (1) are as follows: based on the grade of uranium and the mineral composition of the high-fluorine uranium ore, the ore can be crushed to any particle size between -4 and -20 mm and then packed into columns or piles.

[0050] Step (2) specifically involves preparing a sulfuric acid solution with a liquid-to-solid ratio of 2 to 5:1 (20 to 100 g / L) and spraying it onto the ore pile. The daily spraying time is 12 to 24 hours, and the spraying intensity is 10 to 50 L / (m²). 2 •h), the leachate is adsorbed with conventional resin. The adsorption tail liquid is neutralized with lime to a pH of 6-9, defluorinated and filtered before being recycled. The concentration of sulfuric acid sprayed is gradually reduced according to the acidity of the leachate until the pH of the effluent is less than 2.0.

[0051] This invention addresses the characteristic of fluoride-containing minerals being highly soluble under acidic conditions. It employs high-acid pretreatment to rapidly dissolve harmful components such as fluoride ions from the ore. After recovering uranium from the leachate, the leachate undergoes alkaline precipitation with lime for impurity removal before being reused, effectively reducing the total concentration of harmful fluoride ions in the system. The defluorination reaction is as follows:

[0052] 2HF + Ca(OH)₂ → CaF₂↓ + 2H₂O

[0053] The specific steps (3) are as follows: the bacteria used are one or more of the following iron-sulfur oxidizing mixed bacteria: Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, and Acidithiobacillus thiooxidans. First, the ore is adapted to the bacteria by bacterial domestication in the laboratory. When its tolerance to fluoride ions increases to 300-1500 mg / L, the bacterial solution is expanded by using a bioreactor or biological oxidation tank. The cultured high-activity bacterial solution is sprayed onto the ore column after acid pretreatment and the bacteria are introduced into the ore pile. The bacteria are introduced 3-6 times, with a liquid-solid ratio of 1-3:1 for each time.

[0054] Step (4) specifically involves: using process water to prepare a sulfuric acid solution with a mass concentration of 5–20 g / L, circulating and spraying it over the ore pile where the bacteria have been introduced; controlling the pH of the leachate at 1.2–2.0; maintaining a daily spray liquid-to-solid ratio of 1–3:1; spraying time of 12–24 hours per day; and spraying intensity of 10–50 L / (m²). 2 During the period, the amount of boric acid added was calculated according to the molar ratio of boron to fluoride ions in the solution of 1:4. The effect of fluoride ions on bacterial growth was reduced by the complexation of boron and fluoride. Ferrous sulfate was added to maintain the ferric iron content at 3-5 g / L, in order to ensure the bacterial activity in the ore pile.

[0055] This invention is based on the fact that fluorine is hydrogen fluoride (in ionic form F). - The principle behind the inhibitory effect of fluoride ions on bacteria is achieved by adding boric acid to the process circulating water. This alters the form of fluoride ions in the system, leading to the formation of a large ionic complex, hexafluoroaluminate, through the complexation of boric acid and fluoride: 4HF + H3BO3 → HBF4 + 3H2O. In this reaction, boric acid and fluoride ions react in an acidic environment (provided by hydrogen ions) to produce fluoroboric acid and water, thus reducing the form of fluoride ions. - Effects on bacterial growth. Furthermore, the complexation of fluoride ions with boric acid will generate BF4, which is more stable than FeF3. - Complex ions further enhance Fe 3+ This method frees up the system and solves the problem of insufficient system potential, ultimately enabling wastewater-free bacterial leaching of high-fluoride uranium ore. It avoids the difficulty of bacterial growth and survival under high fluoride ion conditions and achieves full recycling of process water.

[0056] The specific steps (5) are as follows: under normal circumstances, spraying can be stopped when the uranium concentration in the leaching solution is stably reduced to <30mg / L, or the uranium leaching rate is greater than 90%. After emptying the reactor, the reactor is washed with clean water at a liquid-to-solid ratio of 1:1. The wash water can be used as the process water for the next column. Finally, the column is unloaded and the uranium content is analyzed. The tailings are discarded.

[0057] Example 1

[0058] A certain volcanic uranium ore is formed in a uranium-fluorite-sericite (hydromica) mineralized section, characterized by strong fluoritization, accompanied by strong hydromica formation and a certain degree of apatitization. The mineralization superimposed on uranium-hematite type ore. Uranium minerals are often associated with fluorite, hydromica, apatite, and microcrystalline quartz. The ore has a uranium grade of 0.20% and a fluorine content of 5.15%, classifying it as a high-fluorine, complex, and difficult-to-process uranium ore. The method described in this invention for processing this high-fluorine uranium ore includes the following process steps:

[0059] (1) Ore crushing: After crushing the uranium ore to a particle size of -5mm, weigh 5kg and pack it into a column with a diameter of 5cm and a height of 1.8m;

[0060] (2) Acid pretreatment stage: A sulfuric acid solution with a liquid-to-solid ratio of 4:1 and a mass concentration of 50 g / L was prepared by spraying the ore pillar with clean water. The daily spraying time was 24 hours, and the spraying intensity was 21.2 L / (m). 2 •h) The collected leachate is used to adsorb uranium using 201*7 resin. The adsorption tail liquid is neutralized to pH 8.5 with lime, filtered to remove impurities, and then recycled. During the circulating spraying stage, the acidity of the solution and the spraying parameters are controlled the same as the first spraying.

[0061] The cyclic spraying continued until the pH of the effluent was less than 2.0, and this stage lasted for 10 days.

[0062] (3) Inoculation stage: The bacteria used are a mixture of ferrooxidizobacterium and thiooxidizobacterium. First, the uranium ore is gradually cultured and acclimated. When its tolerance to fluoride ions increases to 500 mg / L, the bacterial solution is expanded and cultured in a bioreactor. The cultured high-activity bacterial solution is sprayed onto the ore column after acid pretreatment and inoculated into the ore column. The bacterial inoculation is carried out 5 times, with a liquid-to-solid ratio of 1:1 each time; the time taken is 5 days.

[0063] (4) Process water circulation spraying stage: After the ore pillar is inoculated with bacteria, the process water is used to prepare a spraying solution containing sulfuric acid (first spraying solution) to spray the ore pile in step (3), collect the leachate, and adsorb the leachate with resin (201*7 resin) to obtain adsorption tailings. Sulfuric acid, boric acid and ferrous sulfate are added to the adsorption tailings as needed for the next spraying treatment, and the spraying is carried out in this way; wherein, the concentration of sulfuric acid in the first spraying solution is 5-20 g / L, and the amount of boric acid is 2 g / L;

[0064] During the circulating spraying phase, the pH of the leachate was controlled between 1.4 and 2.0 for each cycle, the daily spraying liquid-to-solid ratio was 1:1, the daily spraying time was 12 hours, and the spraying intensity was 21.2 L / (m²). 2 During this period, the amount of boric acid added was calculated based on a molar ratio of boron to fluoride ions in the leachate of 1:4. The content of ferric iron in each leachate was greater than or equal to 3 g / L (if it was less than this number, ferrous sulfate could be added to the spray solution). This stage lasted for 32 days.

[0065] (5) Washing the reactor with clean water: When the uranium concentration in the leaching solution is stably reduced to <30mg / L for four consecutive days, the reactor is washed with clean water at a liquid-to-solid ratio of 1:1 after emptying the reactor. The wash water is used as the process water for the next column. Finally, the column is unloaded and the uranium content is analyzed. The tailings are discarded.

[0066] Final results: After acid pretreatment to remove impurities and boron ion complexes, bacteria can quickly survive in this high-fluorine uranium ore without the need for oxidant addition, and all process water is recycled. The uranium content in the tailings is 0.013%, and the uranium leaching rate is 93.50%.

[0067] The following table 1 compares the various methods used to process the high-fluorine-content, refractory uranium ore of Example 1 with those of Example 1:

[0068] Comparative Example 1:

[0069] Compared with Example 1, the difference is that in step 3, no bacterial strain is implanted, and in step 4, boric acid is not sprayed; instead, a solution containing 3g / LFe is directly sprayed. 3+ Spray with ferric sulfate or sulfuric acid solution of 5-20 g / L.

[0070] Comparative Example 2:

[0071] Compared with Example 1, the only difference is that step 2 is omitted, and step 3 and subsequent treatments are carried out directly after step 1. The cyclic spraying time in step 4 is extended to 77 days, and the total treatment time is 82 days. All other operations and parameters are the same as in Example 1.

[0072] Comparative Example 3

[0073] Compared to Example 1, the only difference is that boric acid is missing in step 4. Furthermore, the spraying time in step 4 is extended to 73 days; all other operations and parameters are the same as in Example 1.

[0074] Comparative Example 4

[0075] Compared with Example 1, the only difference is that in step 4, an equimolar amount of aluminum sulfate is used to replace boric acid (the concentration of aluminum sulfate in the first spray solution is 3 g / L, and the molar ratio of Al to leachate is 1:3 in the subsequent steps), and the spraying time in step 4 is extended to 40 days. All other operations and parameters are the same as in Example 1.

[0076] The results of Example 1 and Comparative Examples 1-4 are shown in Table 1:

[0077] Table 1

[0078]

[0079] In summary, the process of this invention, based on the first stage acid treatment and the second stage acid treatment assisted by boric acid, can solve the problem of bacterial poisoning caused by high F. It can achieve better leaching efficiency and effect without the need to use high F-tolerant acclimatized bacterial strains.

[0080] Example 2

[0081] Similar to Example 1, the difference lies in changing some parameters, specifically:

[0082] This uranium deposit is a low-to-medium temperature hydrothermal uranium deposit, belonging to the uranium-apatite-chlorite mineralization category, with the ore lithology being welded tuff lava. The main minerals include quartz, albite, chlorite, calcite, fluorapatite, and small amounts of dispersed hematite and limonite. Uranium in the ore mainly exists in the form of pitchblende, with a small amount oxidized to residual uranium black. Liquid latex microradiography indicates that quartz and calcite do not contain uranium. Uranium exists in dispersed form in fluorapatite, limonite, and speckled chlorite. The uranium grade in the ore is 0.131%, and the fluorine content is 8.85%, classifying it as a high-fluorine, difficult-to-process uranium ore. The method described in this invention for processing this high-fluorine uranium ore includes the following process steps:

[0083] (1) Ore crushing: After crushing the uranium ore to a particle size of -6mm, weigh 20kg and pack it into a column with a diameter of 10cm and a height of 1.7m;

[0084] (2) Acid pretreatment stage: A sulfuric acid solution with a liquid-to-solid ratio of 4:1 and a mass concentration of 40 g / L was prepared by spraying the ore pillar with clean water. The daily spraying time was 24 hours, and the spraying intensity was 21.2 L / (m). 2 •h), the collected leachate was used to adsorb uranium using D363 resin. The adsorption tail liquid was neutralized with lime to pH 8.8, filtered to remove impurities, and then recycled until the pH of the effluent was less than 2.0. This stage lasted for 8 days.

[0085] (3) Inoculation stage: The bacteria used are a mixture of ferrous thiobacillus and ferrous leptospira. First, the uranium ore is gradually cultured and acclimatized. When its tolerance to fluoride ions increases to 600 mg / L, the bacterial solution is expanded by using a bioreactor. The cultured high-activity bacterial solution is sprayed onto the ore column after acid pretreatment. The ore column is inoculated with bacteria three times, with a liquid-to-solid ratio of 1:1 for each time.

[0086] (4) Process water circulation and spraying stage: After the inoculum is planted in the ore pillar, a sulfuric acid solution with a mass concentration of 8-20 g / L is prepared using process water and circulated for spraying. The pH of the leachate is controlled at ~1.5, the daily spray liquid-to-solid ratio is 1:1, the daily spraying time is 16 hours, and the spraying intensity is 15.9 L / (m²). 2 During the first leaching stage (h), the amount of boric acid added was calculated based on a 1:4 molar ratio of boron to fluoride ions in the solution (4 g / L of boric acid was used in the first leaching solution). The complexation of boron and fluoride reduced the influence of fluoride ions on bacterial growth. Since the content of ferric iron in the system was already greater than 3 g / L, the bacterial activity in the ore pile was sufficient, so there was no need to add ferrous sulfate. This stage lasted for 35 days. The leachate was reused after uranium adsorption through ion exchange.

[0087] (5) Washing the reactor with clean water and removing slag: When the uranium concentration in the leaching solution is stably reduced to <25mg / L for four consecutive days, the reactor is washed with clean water at a liquid-to-solid ratio of 1:1 after emptying the reactor. The wash water is used as the process water for the next column. Finally, the column is unloaded and the uranium content is analyzed. The tailings are discarded.

[0088] Final results: After acid pretreatment to remove impurities and aluminum ion complexes, bacteria can quickly survive in this high-fluorine uranium ore without the need for oxidant addition, and all process water is recycled. The uranium content in the tailings is 0.013%, and the uranium leaching rate is 90.07%.

[0089] Example 3

[0090] Similar to Example 1, the difference lies in changing some parameters, specifically:

[0091] The gangue minerals of a certain uranium deposit mainly include muscovite, quartz, calcite, epidote, rutile, fluorite, fluorapatite, and zircon. The ore contains a high amount of calcite and fluorite, which will result in a higher acid consumption. The main metallic minerals include pyrite, rutile, sphalerite, ilmenite, sulphite, galena, and magnetite. The uranium grade in the ore is 0.118%, and the fluorine content is 9.95%, classifying it as a high-fluorine, difficult-to-process uranium ore. The method described in this invention for processing this high-fluorine uranium ore includes the following process steps:

[0092] (1) Ore crushing: After crushing the uranium ore to a particle size of -10mm, weigh 20kg and pack it into a column with a diameter of 10cm and a height of 1.8m;

[0093] (2) Acid pretreatment stage: A sulfuric acid solution with a liquid-to-solid ratio of 4:1 and a mass concentration of 50 g / L was prepared by spraying the ore pillar with clean water. The daily spraying time was 24 hours, and the spraying intensity was 21.2 L / (m). 2 •h), the collected leachate was used to adsorb uranium using D263 resin. The adsorption tail liquid was neutralized with lime to pH 9.0, filtered to remove impurities, and then recycled until the pH of the effluent was less than 2.0. This stage lasted for 10 days.

[0094] (3) Inoculation stage: The bacteria used are a mixture of ferrous thiobacillus and ferrous leptospira. First, the uranium ore is gradually cultured and acclimatized. When its tolerance to fluoride ions increases to 500 mg / L, the bacterial solution is expanded and cultured in a bioreactor. The cultured high-activity bacterial solution is sprayed onto the ore column after acid pretreatment and the ore column is inoculated with bacteria. The bacteria are inoculated 4 times, with a liquid-solid ratio of 1:1 for each time.

[0095] (4) Process water circulation and spraying stage: After the inoculum is planted in the ore pillar, a sulfuric acid solution with a mass concentration of 5-20 g / L is prepared using process water and circulated for spraying. The pH of the leachate is controlled at ~1.5, the daily spray liquid-to-solid ratio is 1:1, the daily spraying time is 16 hours, and the spraying intensity is 15.9 L / (m²). 2 During the first leaching stage (h), the amount of boric acid added was calculated based on a 1:4 molar ratio of boron to fluoride ions in the solution (5 g / L of boric acid was used in the first leaching solution). The complexation of boron and fluoride reduced the influence of fluoride ions on bacterial growth. Since the ferric iron content in the system was already greater than 3 g / L, the bacterial activity in the ore pile was sufficient, so there was no need to add ferrous sulfate. This stage lasted for 33 days. The leachate was reused after ion exchange adsorption of uranium.

[0096] (5) Washing the reactor with clean water: When the uranium concentration in the leaching solution is stably reduced to <25mg / L for 3 consecutive days, the reactor is washed with clean water at a liquid-to-solid ratio of 1:1 after emptying the reactor. The wash water is used as the process water for the next column. Finally, the column is unloaded and the uranium content is analyzed. The tailings are discarded.

[0097] Final results: After acid pretreatment to remove impurities and aluminum ion complexes, bacteria can quickly survive in this high-fluorine uranium ore without the need for oxidant addition, and all process water is recycled. The uranium content in the tailings is 0.011%, and the uranium leaching rate is 90.68%.

[0098] In summary, this invention provides a wastewater-free bacterial leaching method for high-fluoride-content uranium ore. Firstly, this method employs high-acid pretreatment to rapidly dissolve a large amount of harmful components in the ore, followed by impurity removal to reduce the concentration of harmful ions in the system. Secondly, while improving the bacterial strain's tolerance to harmful fluoride ions in the ore, boric acid is added to the process circulating water. The strong complexation between boron and fluoride reduces the impact of fluoride ions on bacterial growth, ultimately achieving wastewater-free bacterial leaching of high-fluoride-content uranium ore. This method avoids the problem of bacterial growth and survival under high fluoride ion conditions and achieves full recycling of process water. It has advantages such as low equipment investment, strong overall practicality, low treatment cost, environmental friendliness, simple and feasible operation, and ease of industrial production.

Claims

1. A method for bacterial leaching of high-fluorine-content uranium ore, characterized in that the steps include: include: Step (1): Acid pre-soaking treatment After crushing the high-fluorine-content uranium ore, it is loaded into pillars or piled up to obtain a ore pile. The ore pile is sprayed with an acidic spraying liquid. The collected leaching liquid is subjected to uranium adsorption treatment. The adsorption tail liquid is defluorinated and then recycled back to the spraying process. Step (2): Bacteria were implanted into the ore pile in step (1); then a spray solution containing boric acid and acid was used to spray and leach the bacteria, and the collected bacterial leachate was subjected to uranium adsorption treatment, and the adsorption tail liquid was recycled back to the bacterial leaching process. The acid in step (2) is sulfuric acid.

2. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, The high-fluorine uranium ore contains more than 5 wt.% F and 0.5-3 wt.% U.

3. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, In step (1), the high-fluorine uranium ore is crushed to less than 20 mm.

4. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, In step (1), the acid in the spray solution is sulfuric acid.

5. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 4, characterized in that, During the spraying process, the concentration of acid solute in the spray solution is 20~100g / L.

6. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 4, characterized in that, The spraying time is 12-24h, and the spraying intensity is 10-50 L / (m 2 • h).

7. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, In step (1), uranium is adsorbed using resin, wherein the resin includes at least one of D363B macroporous resin, D201 macroporous resin, 201×7 resin, D263 macroporous resin, and D301 macroporous resin.

8. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, In step (1), the defluorination process includes using lime to neutralize the pH of the adsorption tail liquid to 6-9 and a solid-liquid separation step.

9. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, In step (1), the pH value of the effluent from the circulating spray is less than 2.0, and step (1) ends.

10. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, In step (2), the bacterial species is *Thiobacillus ferrooxidans* (…). Acidithiobacillus ferrooxidans ), ferrous oxide Leptospira ( Leptospirillum ferrooxidans ), Thiobacillus thiooxidans ( Acidithiobacillus thiooxidans One or more of the following.

11. The method for bacterial leaching of high-fluorine-containing uranium ore as described in claim 10, characterized in that, In step (2), the bacteria mentioned are domesticated bacteria.

12. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 11, characterized in that, In step (2), the bacteria are bacteria that have been domesticated with high-fluorine uranium ore.

13. The method for bacterial leaching of high-fluorine-containing uranium ore as described in claim 10, characterized in that, In step (2), the bacteria have a tolerance to fluoride ions ≥300 mg / L.

14. The method for bacterial leaching of high-fluorine-containing uranium ore as described in claim 13, characterized in that, In step (2), the bacteria have a tolerance to fluoride ions of 300~1500 mg / L.

15. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, During the bacterial leaching process in step (2), the concentration of acid in the spray solution is controlled to be 5~20g / L; the concentration of boric acid is ≤10g / L.

16. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 15, characterized in that, In step (2), the pH of the leachate is controlled at 1.2~2.0, the total iron ion concentration in the leachate is controlled at ≥3g / L, the daily spray liquid-to-solid ratio is 1~3:1, the daily spraying time is 12~24h, and the spraying intensity is 10~50L / (m²). 2 ·h).

17. The method for bacterial leaching of high-fluorine-containing uranium ore as described in claim 15, characterized in that, In step (2), uranium is adsorbed using resin, wherein the resin includes at least one of D363B macroporous resin, D201 macroporous resin, 201×7 resin, D263 macroporous resin, and D301 macroporous resin.

18. The method for bacterial leaching of high-fluorine-content uranium ore as described in claim 1, characterized in that, The uranium adsorption tail liquid is reused in the bacterial leaching process.

19. The method for bacterial leaching of high-fluorine-containing uranium ore as described in any one of claims 1, 15-18, characterized in that, The uranium concentration in the bacterial leachate is continuously sprayed until it stabilizes and decreases to <30 mg / L, or the uranium leaching rate is greater than 90%. After the reactor is empty, it is washed with clean water, which can be used as the process water for the next column. Finally, the column is unloaded and samples are taken to analyze the uranium content. The tailings are discarded.

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