A method for recovering carbonate sandstone uranium ore

Abstract

The present invention belongs to the field of uranium resource utilization technology, and specifically relates to a method for recovering carbonate sandstone uranium ore. The staged, efficient recovery method provided by the present invention, on the one hand, directly increases the leaching rate of carbonate sandstone uranium mining areas by more than 15%; on the other hand, the present invention shortens the leaching cycle of carbonate sandstone uranium mining areas by 3 to 5 years. The present invention timely adjusts the leaching method according to the different leaching stages of carbonate sandstone uranium ore, adapts to changes in the lithology of the ore layer, and effectively controls chemical blockage at each leaching stage. This solves the problem of low recovery rate of carbonate sandstone uranium ore under neutral leaching conditions, "extracts" the remaining uranium, improves the leaching rate, shortens the uranium mine development cycle, and achieves efficient uranium recovery. The method is particularly suitable for mining sandstone uranium ores with high reservoir carbonate content and bicarbonate concentrations of less than 500 mg / L in the original ore layer water.

Description

Technical Field

[0001] The invention belongs to the technical field of uranium resource utilization, and particularly relates to a method for recovering carbonate sandstone uranium ore. Background Art

[0002] In-situ uranium leaching process is mainly divided into neutral leaching process and acid leaching process according to the type of leaching agent. Among them, the neutral leaching process is suitable for sandstone uranium deposits with high carbonate content (CO2> 2%), or HCO3 in the ore layer water. - For sandstone uranium deposits with a concentration > 800 mg / L, the acid leaching process is suitable for deposits with low carbonate content.

[0003] For the sandstone uranium ore with high carbonate content, the neutral leaching process includes two stages: the first stage uses CO2 and O2 as leaching agents, O2 oxidizes the quadrivalent uranium in the ore layer, and CO2 fully reacts with the carbonate in the ore layer to generate sufficient HCO3 - , to achieve the conditions for oxidation and dissolution migration of uranium minerals; in the second stage, as the carbonate minerals in the ore layer are exhausted, the leaching agent formula is adjusted to CO2, O2 and NaHCO3, or CO2, O2 and NH4HCO3, the pH value is controlled at 6.5-7.0, and the HCO3 - The concentration is >800mg / L until the final sampling of the sampling area.

[0004] When the above-mentioned neutral leaching process mining area is finally mined, most of the areas have co-precipitation of calcite and uranium minerals. The carbonate content in the ore is significantly higher than that in the surrounding rock. Under the conditions of CO2 and O2 leaching processes, the calcite minerals are dissolved and the uranium elements are reactivated and migrated. However, the leaching rate is low, with an average leaching rate of 50% to 75% (including the recovery of extra-surface ore). Summary of the Invention

[0005] The purpose of the present invention is to provide a method for recovering carbonate sandstone uranium ore. The recovery method of carbonate sandstone uranium ore provided by the present invention directly increases the leaching rate by more than 15% compared with conventional methods.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for recovering carbonate sandstone uranium ore, comprising the following steps:

[0008] (1) Using a first leaching agent to perform a first leaching on a carbonate sandstone uranium ore to obtain a leachate until HCO3 in the leachate is - The concentration of the first leaching agent includes CO2, O2 and water;

[0009] (2) using a second leaching agent to perform a second leaching on the carbonate sandstone uranium ore after the first leaching to obtain a leachate, wherein HCO3 - The concentration is not less than 800 mg / L; the second leaching agent includes CO2, O2, water and bicarbonate; the bicarbonate includes one or more of NaHCO3, NH4HCO3, KHCO3 and Mg(HCO3)2;

[0010] (3) after the carbonate sandstone uranium ore after the second leaching is subjected to transformation preparation using a transformation preparation leaching agent, the carbonate sandstone uranium ore after the transformation preparation is subjected to transformation leaching using a transformation preparation leaching agent to obtain a leachate, until the pH value of the leachate is reduced to 2; the transformation preparation leaching agent includes a transformation preparation oxidant and water; the transformation preparation oxidant includes one or both of oxygen and hydrogen peroxide; the transformation leaching agent includes an inorganic acid and water;

[0011] (4) performing a third leaching on the carbonate sandstone uranium ore after the transition leaching using a third leaching agent; the third leaching agent comprises H2SO4, H2O2 and water.

[0012] Preferably, the first leaching includes an initial leaching period and a peak leaching period performed sequentially; in the initial leaching period, the concentration of CO2 in the first leaching agent is 400-600 mg / L, and the concentration of O2 is 100-200 mg / L.

[0013] Preferably, during the peak leaching period, the concentration of CO2 in the first leaching agent is 600-800 mg / L, and the concentration of O2 is 150-300 mg / L.

[0014] Preferably, the leaching preparation is further included before the initial stage of leaching; the leaching preparation is: using a leaching preparation agent to dredge the ore layer; the leaching preparation agent includes CO2 and water.

[0015] Preferably, the concentration of CO2 in the leaching preparation agent is 200-400 mg / L.

[0016] Preferably, the second leaching includes a mid-leaching period and a mid-late leaching period, which are carried out in sequence. In the mid-leaching period, the concentration of CO2 in the second leaching agent is 400-600 mg / L, the concentration of O2 is 100-200 mg / L, and the concentration of bicarbonate is based on the concentration of HCO3 in the second leaching agent. - The concentration is above 1000mg / L.

[0017] Preferably, in the middle and late stages of leaching, the concentration of CO2 in the second leaching agent is 300-400 mg / L, the concentration of O2 is 100-200 mg / L, and the concentration of bicarbonate is based on the concentration of HCO3 in the leaching agent. -The concentration is 800-1200 mg / L.

[0018] Preferably, the concentration of the transition pre-oxidant in the transition pre-leaching agent is 100 to 200 mg / L.

[0019] Preferably, the concentration of the inorganic acid in the transition leaching agent is 2-3 g / L.

[0020] Preferably, the concentration of H2SO4 in the third leaching agent is 6-10 g / L, and the concentration of H2O2 is 0.2-0.5 g / L.

[0021] The present invention provides a method for recovering carbonate sandstone uranium ore. The recovery method provided by the present invention includes a first leaching stage, a second leaching stage, and a third leaching stage after the leaching process is transformed; the node control of different leaching stages is based on the HCO3 - Concentration changes and concentration values: The first leaching stage ends with HCO3 in the leaching solution - After the concentration reaches the peak, it gradually decreases to 800 mg / L as the control point; the second leaching stage ends and HCO3 is added - Still can't maintain HCO3 in the leachate - The control node is when the concentration is 800 mg / L; the leaching process transformation stage ends when the pH value drops to 2; the third leaching stage ends when the uranium concentration in the leachate is lower than the economically recoverable concentration (such as Figure 1 shown).

[0022] The beneficial effects achieved by the phased efficient recovery method provided by the present invention mainly include two aspects: on the one hand, the leaching rate of the carbonate sandstone uranium mining area is increased by more than 15% (the leaching rate is directly increased by more than 15%, rather than increasing the original leaching rate by more than 15%, for example, the leaching rate is increased from 70% to more than 85%, rather than more than 115% of 70%): the present invention first adopts neutral leaching to solve the problem of high carbonate content in the early and middle stages of leaching of carbonate sandstone uranium ore, and by adding CO2 to dissolve carbonate minerals and adjusting the leaching pH value, a uranium leaching complexing agent HCO3 is generated. - , killing two birds with one stone; with the gradual consumption of carbonate minerals, the carbonate content of the ore deposit is low enough to meet the requirements of the acid leaching process, and then the leaching process transformation method is adopted to smoothly transition the uranium leaching interval from the neutral leaching interval to the acid leaching interval; after that, the acid leaching process is adopted to dissolve the acid-soluble chemical blockages formed in the ore layer during the neutral leaching stage, dredge the ore layer, dissolve the surface inclusions of the uranium minerals, realize the efficient leaching of the remaining uranium, and effectively improve the uranium leaching rate.

[0023] On the other hand, the present invention shortens the leaching cycle of carbonate sandstone uranium mining areas by 3 to 5 years: the leaching cycle of existing in-situ leaching uranium mining processes is generally 8 to 12 years. After the leaching process transformation stage, acid leaching is adopted to accelerate the dissolution of uranium minerals, increase the leaching reaction rate, reduce the tailing in the late stage of neutral leaching, and shorten the service life of the mining area.

[0024] The present invention timely adjusts the leaching method according to different leaching stages of carbonate sandstone uranium ore, adapts to changes in ore layer lithology, effectively controls chemical blockage at each leaching stage, solves the problem of low recovery rate of carbonate sandstone uranium ore under neutral leaching conditions, "extracts" the remaining uranium, improves the leaching rate, shortens the uranium ore development cycle, and realizes efficient uranium recovery. The present invention is particularly suitable for mining sandstone uranium ore with a high carbonate content in the reservoir and a bicarbonate concentration of less than 500 mg / L in the original ore layer water. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a process flow chart of the method for recovering carbonate sandstone uranium ore of the present invention;

[0027] Figure 2 This is a schematic diagram of the leaching transformation principle of the recovery method of the present invention;

[0028] Figure 3 The concentration changes of uranium, bicarbonate and sulfate ions in the leachate at different stages of Example 1 of the present invention are shown;

[0029] Figure 4 The uranium concentration and cumulative leaching rate in the leachate at different stages of Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0030] The present invention provides a method for recovering carbonate sandstone uranium ore, comprising the following steps:

[0031] (1) Using a first leaching agent to perform a first leaching on a carbonate sandstone uranium ore to obtain a leachate until HCO3 in the leachate is - The concentration of the first leaching agent includes CO2, O2 and water;

[0032] (2) using a second leaching agent to perform a second leaching on the carbonate sandstone uranium ore after the first leaching to obtain a leachate, wherein HCO3 -The concentration is not less than 800 mg / L; the second leaching agent includes CO2, O2, water and bicarbonate; the bicarbonate includes one or more of NaHCO3, NH4HCO3, KHCO3 and Mg(HCO3)2;

[0033] (3) after the carbonate sandstone uranium ore after the second leaching is subjected to transformation preparation using a transformation preparation leaching agent, the carbonate sandstone uranium ore after the transformation preparation is subjected to transformation leaching using a transformation preparation leaching agent to obtain a leachate, until the pH value of the leachate is reduced to 2; the transformation preparation leaching agent includes a transformation preparation oxidant and water; the transformation preparation oxidant includes one or both of oxygen and hydrogen peroxide; the transformation leaching agent includes an inorganic acid and water;

[0034] (4) performing a third leaching on the carbonate sandstone uranium ore after the transition leaching using a third leaching agent; the third leaching agent comprises H2SO4, H2O2 and water.

[0035] The present invention uses a first leaching agent to perform a first leaching on carbonate sandstone uranium ore to obtain a leachate until HCO3 in the leachate is - The concentration of HCO3 in the leachate is reduced to 800 mg / L. In the present invention, the first leaching preferably includes an initial leaching period and a peak leaching period carried out in sequence; the first leaching is preferably a flow leaching. In the present invention, the concentration of HCO3 in the leachate increases first and then decreases. When the concentration of HCO3 in the leachate increases to 800 mg / L, the peak leaching period begins from the initial leaching period; when the concentration of HCO3 in the leachate increases to 800 mg / L, the peak leaching period begins; - When the concentration of iodine decreases from a high value to 800 mg / L, the leaching peak ends (the first leaching also ends).

[0036] In the present invention, in the initial stage of leaching, the concentration of CO2 in the first leachant is preferably 400-600 mg / L, more preferably 450-550 mg / L, and further preferably 500 mg / L, and the concentration of O2 is preferably 100-200 mg / L, more preferably 120-180 mg / L, and further preferably 140-160 mg / L.

[0037] In the present invention, in the initial stage of leaching, the mass ratio of the first leaching agent to the carbonate sandstone uranium ore is preferably 5-10:1000-2000, more preferably 5-8:1000-2000, and even more preferably 5:1000.

[0038] The present invention monitors the pH value and HCO3 of the leachate simultaneously at the initial stage of leaching. - concentration and uranium concentration and its changes (if necessary, also monitor Ca 2+ Mg 2+ , K + 、SO42- and Si plasma or element), during this period, the pH value of the leachate dropped to 6.5-7.5, HCO3 - The concentration rises to above 500 mg / L, and the uranium concentration gradually increases. When the ore grade is about 0.05% and the uranium content per square meter is 5 kg / m 2 In the mining area, the uranium concentration is generally 20 to 80 mg / L.

[0039] In the present invention, the leaching preparation is preferably further included before the initial leaching; the leaching preparation is preferably: using a leaching preparation agent to dredge the ore layer to obtain a leachate; the leaching preparation agent includes CO2 and water; the leaching preparation is preferably carried out by using HCO3 in the leachate. - The treatment ends when the concentration reaches 600 mg / L.

[0040] In the present invention, the concentration of CO2 in the leaching preparation agent is preferably 200-400 mg / L, more preferably 250-350 mg / L, and further preferably 300 mg / L. In the present invention, CO2 is added to pre-dredge the ore layer, and the pH value and HCO3 of the leaching solution are monitored simultaneously. - Concentration and uranium concentration and its changes. Generally, HCO3 in the leaching solution - The concentration gradually increases and the pH value decreases, and the uranium concentration will not increase substantially in the pre-leaching stage.

[0041] In the present invention, the mass ratio of CO2 to carbonate sandstone uranium ore in the leaching preparation is preferably 2-5:1000-2000, more preferably 2-3:1000-2000, and further preferably 2:1000.

[0042] In the present invention, the leaching preparation preferably includes geological zoning. The present invention determines the carbonate content, uranium mineral content and occurrence form of the sandstone uranium ore and the hydrogeological characteristics of the ore layer (the geological exploration report of the ore deposit can be consulted), classifies the geological process type of the ore, neutral to weakly alkaline (pH value is 7.0-8.5), ore layer water HCO3 - Sandstone uranium deposits with a concentration of <500 mg / L and a carbonate content in the ore rock (calculated as CO2>1.5%) are classified as carbonate sandstone uranium deposits.

[0043] In the present invention, during the leaching peak period, the concentration of CO2 in the first leaching agent is preferably 600-800 mg / L, more preferably 650-750 mg / L, and further preferably 700 mg / L, and the concentration of O2 is preferably 150-300 mg / L, more preferably 200-270 mg / L, and further preferably 240-250 mg / L.

[0044] In the present invention, during the leaching peak period, the mass ratio of the first leaching agent to the carbonate sandstone uranium ore is preferably 10-20:1000-2000, more preferably 10-15:1000-2000, and even more preferably 10:1000.

[0045] The present invention adds high concentrations of CO2 and O2 during the peak period of leaching, and simultaneously monitors the pH value and HCO3 of the leaching solution. - concentration and uranium concentration and their changes; During this period, HCO3 in the leaching solution - The maximum uranium concentration that the mining area can provide (generally 1000-2000 mg / L) is reached, the pH value is basically maintained between 6.5 and 7.5, and the uranium concentration reaches the peak leaching rate of the mining area throughout its life (30-150 mg / L). In the first leaching stage, the mining area leaching rate is generally 30%-45%, and the main chemical reactions involved are shown in Equations 1 to 3:

[0046] CO2+H2O+CaCO3→Ca 2+ +2HCO3 - (Formula 1);

[0047] UO2+0.5O2+2HCO3 - →UO2(CO3)2 2- +H2O (Formula 2);

[0048] UO3+2HCO3 - →UO2(CO3)2 2- +H2O(Formula 3).

[0049] After the first leaching, the present invention uses a second leaching agent to perform a second leaching on the carbonate sandstone uranium ore after the first leaching to obtain a leachate, wherein HCO3 - The concentration is not less than 800 mg / L. In the present invention, the second leaching preferably includes the middle leaching and the middle and late leaching carried out in sequence; the second leaching is preferably a flow leaching. In the present invention, when the second leaching agent is added to the leachate, HCO3 - When the concentration increment is less than 300-400 mg / L, the leaching process enters the middle and late stages.

[0050] In the present invention, in the middle stage of leaching, the concentration of CO2 in the second leaching agent is preferably 400-600 mg / L, more preferably 450-550 mg / L, and further preferably 500 mg / L, the concentration of O2 is preferably 100-200 mg / L, more preferably 120-180 mg / L, and further preferably 140-160 mg / L, and the concentration of bicarbonate is preferably based on the concentration of HCO3 in the second leaching agent. -The concentration of bicarbonate is above 1000 mg / L. In a specific embodiment of the present invention, the concentration of bicarbonate in the second leaching agent is more preferably 200-300 mg / L, and further preferably 240-270 mg / L. At this stage, the carbonate minerals in the sandstone layer have not been completely consumed, but the content is relatively low. The added CO2 can react with them to replenish some bicarbonate, but the concentration is insufficient. Therefore, the present invention supplements bicarbonate to reach the target concentration.

[0051] In the present invention, in the middle stage of leaching, the mass ratio of the second leaching agent to the carbonate sandstone uranium ore is preferably 5-10:1000-2000, more preferably 5-8:1000-2000, and even more preferably 5:1000.

[0052] The present invention monitors the pH value and HCO3 in the leaching solution simultaneously during the leaching process. - Concentration and uranium concentration and its changes; During this period, the uranium concentration slowly decreased, and the HCO3 in the leachate - It shows a very strong correlation with uranium concentration, and the downward trend is consistent with the downward trend of uranium concentration.

[0053] In the present invention, in the middle and late stages of leaching, the concentration of CO2 in the second leaching agent is preferably 300-400 mg / L, more preferably 320-380 mg / L, and further preferably 340-360 mg / L. The concentration of O2 is preferably 100-200 mg / L, more preferably 120-180 mg / L, and further preferably 140-160 mg / L. The concentration of bicarbonate is preferably based on the concentration of HCO3 in the second leaching agent. - The concentration of bicarbonate is 800-1200 mg / L; in a specific embodiment of the present invention, the concentration of bicarbonate is more preferably 300-500 mg / L, and further preferably 350-450 mg / L. The present invention adds a second leaching agent (CO2) to react with carbonate in carbonate sandstone uranium ore to generate bicarbonate, thereby obtaining a leachate; when HCO3 in the leachate is - When the concentration is 200-300 mg / L, it enters the transformation preparation stage.

[0054] In the present invention, in the middle and late stages of leaching, the mass ratio of the second leaching agent to the carbonate sandstone uranium ore is preferably 3-5:1000-2000, more preferably 3-4:1000-2000, and even more preferably 3:1000.

[0055] The present invention simultaneously monitors the pH value and HCO3 of the leachate in the middle and late stages of leaching. - Concentration and uranium concentration and their changes, during this period, with the HCO3 in the leaching agent -The addition of HCO3 slows down the trend of uranium concentration decrease. - The concentration at the end of the leaching phase exceeds that of the mid-stage leaching phase. The uranium concentration will continue to rise slightly, but this cannot be sustained for a long time. The main chemical reactions in the second leaching phase are the same as those in the first leaching phase. During this phase, the leaching efficiency of the mining area increases by about 15-20%, and the cumulative leaching efficiency can reach 45-65%.

[0056] After the second leaching, the present invention uses a transition preparatory leaching agent to perform transition preparation on the carbonate sandstone uranium ore after the second leaching (to obtain a leachate), and then uses a transition leaching agent to perform transition leaching on the carbonate sandstone uranium ore after the transition preparation to obtain a leachate until the pH value of the leachate is reduced to 2.

[0057] In the present invention, the transformation preparation leachate includes a transformation preparation oxidant and water; the transformation preparation oxidant includes one or both of oxygen and hydrogen peroxide; the concentration of the transformation preparation oxidant in the transformation preparation leachate is preferably 100-200 mg / L, more preferably 120-180 mg / L, and further preferably 140-160 mg / L. During the transformation preparation period, HCO3 in the leachate - The concentration of uranium decreased significantly (down to 500-800 mg / L), and the downward trend of uranium concentration also increased.

[0058] In the present invention, the leaching method of the transformation preparation is preferably flow leaching; the flow rate of the flow leaching is preferably 3 to 10 m 3 / h, more preferably 4 to 8m 3 / h, more preferably 5 to 6 m 3 When the HCO3 concentration in the leachate obtained from the transformation preparation reaches 300-400 mg / L, the transformation preparation is completed.

[0059] In the present invention, the concentration of the inorganic acid in the transition leaching agent is preferably 2-3 g / L, more preferably 2.4-2.7 g / L; the inorganic acid preferably includes one or more of sulfuric acid, hydrochloric acid and citric acid.

[0060] In the present invention, the leaching method of the transition leaching is preferably flow leaching; the flow rate of the flow leaching is preferably 3 to 10 m 3 / h, more preferably 4 to 8m 3 / h, more preferably 5 to 6 m 3 / h.

[0061] The present invention monitors the pH value and HCO3 of the leachate simultaneously during the transition leaching period. - 、SO4 2- 、H + , Ca 2+During this period, the pH value dropped rapidly from 6.5 to 7.5 to 2 to 3, and the complex form of uranium leached also changed from uranyl carbonate to uranyl sulfate (specifically, Figure 2 The uranium concentration is kept at a low level, generally below 20 mg / L. The main function of this stage is to complete the transformation of the mining area leaching process. Due to the relatively short time, the mining area leaching rate is increased by about 3% to 5%. The main chemical reactions involved are shown in Equations 4 to 7:

[0062] H2SO4+HCO3 - →CO2↑+H2O+SO4 2- (Formula 4);

[0063] H2SO4+CaCO3→Ca 2+ +SO4 2- +CO2↑+H2O (Formula 5);

[0064] UO3+4H + +2SO4 2- →UO2(SO4)2 2- +2H2O (Formula 6);

[0065] Fe2O3+6H + →2Fe 3+ +3H2O (Formula 7).

[0066] After the transition leaching, the present invention uses a third leaching agent to perform a third leaching on the carbonate sandstone uranium ore after the transition leaching. In the present invention, the third leaching is at the end of the leaching process. The concentration of H2SO4 in the third leaching agent is preferably 6-10 g / L, more preferably 7-9 g / L, and even more preferably 8 g / L. The concentration of H2O2 is preferably 0.2-0.5 g / L, more preferably 0.3-0.4 g / L, and even more preferably 0.35 g / L.

[0067] In the present invention, the leaching method of the third leaching is preferably flow leaching; the flow rate of the flow leaching is preferably 2 to 8 m 3 / h, more preferably 3 to 7m 3 / h, more preferably 4 to 6m 3 / h.

[0068] The present invention simultaneously monitors the H in the leachate at the end of the leaching process. + , Ca 2+ 、Fe 2+ 、Fe 3+ 、SO4 2- and uranium concentration, H + , Ca 2+ 、Fe 2+、Fe 3+ and SO4 2- The plasma concentration rises rapidly, and the uranium concentration increases compared to the previous stage, generally to 10-40 mg / L. The leaching rate in the mining area increases by about 15-40%, and the cumulative leaching rate in the mining area is 80-110% (including off-surface ore). In the third leaching stage, in addition to the three chemical reactions in Equations 1-3, the following chemical reactions are also included:

[0069] FeS2+5O2+4H + →Fe 3+ +2H2O+2SO4 2- (Formula 8);

[0070] Fe 3+ +UO2+2SO4 2- →UO2(SO4)2 2- +Fe 2+ (Formula 9);

[0071] UO2+H2O2→UO3+H2O (Equation 10);

[0072] UO2+4H + →U 4+ +2H2O (Formula 11).

[0073] In the present invention, the third leaching preferably further includes a mining area decommissioning stage;

[0074] The decommissioning phase of the mining area preferably involves in-situ microbial remediation followed by natural purification. Natural purification is preferably initiated when the pH of the groundwater in the ore-bearing stratum returns to 5-6. The present invention utilizes staged leaching to avoid the direct and intense reaction between carbonate sandstone uranium ore and sulfuric acid, which produces large amounts of calcium sulfate precipitate and subsequently blocks the ore layer. This invention improves leaching efficiency and production efficiency, offering significant economic and ecological benefits.

[0075] The time of each leaching stage or transition leaching period of the present invention is determined according to the specific geological conditions of the ore deposit and the leaching operation conditions. The control node is mainly based on the HCO3 in the leachate. - In the present invention, the leaching preparation period is generally from 1 to 3 months, the initial leaching period is generally from 4 to 12 months, the peak leaching period is generally from 13 to 36 months, the middle leaching period is generally from 36 to 60 months, the middle and late leaching period is generally from 61 to 72 months, the transformation preparation period is generally from 73 to 75 months, the transformation period is generally from 75 to 78 months, and the final leaching period is generally from 79 to 96 months.

[0076] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0077] Example 1

[0078] (1) A sandstone uranium ore sample from the Ordos Basin in Inner Mongolia was taken, crushed to a natural particle size, and mixed evenly. The average grade of the sample was 0.0678%, and the average carbonate content (calculated as CO2) was 3.38%. A pressurized column leaching method was used, with a sample length of 1 m, an inner diameter of 40 mm, and a sample density as close as possible to that of the ore deposit (1.8 kg / dm 3 ), each column sample weighs 2.6 kg; 200 L of ore layer water is taken to prepare the leaching agent;

[0079] (2) During the leaching preparation period, CO2 is added at a concentration of 200-400 mg / L to pre-dredge the ore layer, and the pH value and HCO3 of the leaching solution are monitored simultaneously. - and changes in uranium concentration;

[0080] (3) CO2 and O2 are dissolved in the ore layer water. At the initial stage of leaching, the CO2 concentration is 400-600 mg / L and the O2 concentration is 100-200 mg / L. When the HCO3 concentration in the leachate increases to 800 mg / L, the leaching peak period begins, with the CO2 concentration being 600-800 mg / L and the O2 concentration being 150-300 mg / L. The leachate is injected into a columnar test device under pressure (0.8-1.2 MPa) in a countercurrent manner. A sampling port is set at the top. Samples are taken three times a day at 6h, 12h and 24h to measure the pH value, U concentration and HCO3 of the leachate. - concentration and SO4 2- Concentration; When the HCO3 in the leachate - When the concentration of NH4Cl2 decreases from a high value to 800 mg / L, the leaching peak ends (the first leaching also ends);

[0081] (4) Entering the second leaching stage, the CO2 concentration is 300-400 mg / L, the O2 concentration is 100-200 mg / L, and an NH4HCO3 solution with a concentration of 1000 mg / L is prepared to adjust the HCO3 in the leaching agent. - concentration, ensuring HCO3 in the leaching agent - When the concentration is above 1000mg / L, the pH value and HCO3 of the leachate are monitored simultaneously. - and the change of uranium concentration; when the second leaching agent is added to the leachate HCO3 - When the concentration increment is less than 300 mg / L, it enters the middle and late stages of leaching from the middle stage of leaching;

[0082] (5) When HCO3 in the leachate -When the concentration is 200-300 mg / L, it enters the transition preparation stage, stops adding CO2 and NH4HCO3, and only adds O2 with a concentration of 100-200 mg / L;

[0083] (6) When the HCO3 concentration in the leachate obtained by the transformation preparation reaches 300-400 mg / L, the transformation preparation is completed and the transformation leaching stage begins. H2SO4 with a concentration of 2-3 g / L is added, and the pH value and HCO3 of the leachate are monitored simultaneously. - 、SO4 2- 、H + , Ca 2+ and uranium concentration changes until the pH value of the leachate drops to 2;

[0084] (7) Entering the third leaching stage, H2SO4 and H2O2 are added, the H2SO4 concentration is 6-10g / L, the H2O2 concentration is 0.2-0.5g / L, and the H2O2 concentration of the leaching solution is monitored simultaneously. + , Ca 2+ 、Fe 2+ 、Fe 3+ 、SO4 2- When the uranium concentration in the leachate sample is lower than 3 mg / L, leaching is stopped. The concentration changes of uranium, bicarbonate and sulfate ions in the leachate at different stages, the concentration of uranium and the cumulative leaching rate are shown in Figure 2. Figure 3 and Figure 4 shown.

[0085] according to Figure 3 and Figure 4 It can be seen that: ① In the first leaching stage, carbonate minerals are dissolved by CO2 in a relatively short time, and the HCO3 in the leachate - Rapid growth, simultaneous dissolution and complex leaching of uranium minerals; uranium concentration and HCO3 in the leachate - The concentration showed a strong positive correlation; the carbonate dissolution rate was fast, and it slowly declined after the peak value, and the uranium concentration in the leaching solution also decreased simultaneously;

[0086] ② In the second leaching stage, by adding HCO3 - , maintain the HCO3 of the leaching agent - At concentrations between 1000 and 1200 mg / L, uranium concentrations showed a slight rebound, and then the downward trend slowed down;

[0087] ③Add 300-500 mg / L HCO3 - If it still cannot maintain 1000 mg / L, transformation preparation and transformation leaching can be carried out, and the carbonate content in the ore rock has reached the acid leaching process permit;

[0088] ④ In the third leaching stage, after adding H2SO4 and H2O2, the uranium concentration rebounded rapidly from 12-13 mg / L to over 30 mg / L, which accelerated the leaching of uranium and maintained above 15 mg / L for a long time. The leaching rate of uranium ore was greatly improved, which was more than 25% higher than that in the second stage.

[0089] Example 2

[0090] The method for recovering carbonate sandstone uranium ore provided in this embodiment is the same as that in Example 1, except that the bicarbonate used in step (4) is replaced by NaHCO3.

[0091] Example 3

[0092] The method for recovering carbonate sandstone uranium ore provided in this embodiment is the same as that in Example 1, except that the bicarbonate used in step (4) is replaced by KHCO3.

[0093] Example 4

[0094] The method for recovering carbonate sandstone uranium ore provided in this embodiment is the same as that in Example 1, with the only difference being that the bicarbonate used in step (4) is replaced by Mg(HCO3)2.

[0095] Example 5

[0096] The method for recovering carbonate sandstone uranium ore provided in this embodiment is the same as that in Example 1, except that the O2 used in step (5) is replaced by hydrogen peroxide.

[0097] Example 6

[0098] The method for recovering carbonate sandstone uranium ore provided in this embodiment is the same as that in Example 1, except that the H2SO4 used in step (6) is replaced by hydrochloric acid.

[0099] It can be seen from the above examples that the recovery method of carbonate sandstone uranium ore provided by the present invention increases the leaching rate by more than 15%, has high leaching rate and high efficiency.

[0100] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for recovering carbonate sandstone uranium ore, characterized in that: The steps are: (1) A sandstone uranium ore sample from the Ordos Basin in Inner Mongolia was taken, crushed to a natural particle size, and mixed evenly. The average grade of the sample was 0.0678%, and the average carbonate content was 3.38% in terms of CO2. A pressurized column leaching method was used, with a sample length of 1 m, an inner diameter of 40 mm, and a sample density of 1.8 kg / dm2, which was as close as possible to that of the ore deposit. 3 , each column sample weighs 2.6kg; 200L of ore layer water is taken to prepare the leaching agent; (2) During the leaching preparation period, CO2 is added at a concentration of 200-400 mg / L to pre-dredge the ore layer; (3) Dissolve CO2 and O2 in the mineral water. In the initial stage of leaching, the CO2 concentration is 400~600mg / L and the O2 concentration is 100~200mg / L. When HCO3 - When the concentration of HCO3 in the leaching solution increases to 800 mg / L, the leaching peak period begins, the CO2 concentration is 600~800 mg / L, and the O2 concentration is 150~300 mg / L. The leaching solution is injected into the columnar test device in a countercurrent manner with a pressure of 0.8~1.2 MPa. - When the concentration of NH4Cl2 decreased from a high value to 800 mg / L, the leaching peak ended and the first leaching also ended; (4) Entering the second leaching stage, the CO2 concentration is 300~400mg / L, the O2 concentration is 100~200mg / L, and an NH4HCO3 solution with a concentration of 1000mg / L is prepared to adjust the HCO3 in the leaching agent - concentration, ensuring HCO3 in the leaching agent - The concentration is above 1000 mg / L; when the second leaching agent is added to the leachate, HCO3 - When the concentration increment is less than 300 mg / L, it enters the middle and late stages of leaching from the middle stage of leaching; (5) When HCO3 in the leachate - When the concentration is 200~300mg / L, it enters the transformation preparation stage, stops adding CO2 and NH4HCO3, and only adds O2 with a concentration of 100~200mg / L; (6) When the HCO3 in the leachate prepared by the transformation - When the concentration reaches 300-400 mg / L, the transformation preparation is completed and the transformation leaching stage begins, adding H2SO4 at a concentration of 2-3 g / L until the pH value of the leachate drops to 2; (7) Entering the third leaching stage, H2SO4 and H2O2 are added, the H2SO4 concentration is 6~10g / L, and the H2O2 concentration is 0.2~0.5g / L. When the uranium concentration in the leachate sample is lower than 3mg / L, the leaching is stopped.

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