Method for leaching uranium from radioactive high-silicon waste residues

Abstract

The invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for leaching uranium in radioactive high-silicon waste residues. The method comprises the steps of water content adjustment, acid mixing and curing, two-stage countercurrent leaching and uranium separation and recovery. By means of the steps, efficient and economical extraction and recovery of uranium in the waste residues are achieved, and the uranium leaching rate is larger than 98%. Compared with the prior art, the method has the technical advantages of simple process flow, low reagent cost, low equipment investment, low three-waste generation amount and the like. The invention provides an effective method for efficiently extracting and recycling uranium in radioactive smelting waste slag.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for leaching uranium from radioactive high-silicon waste slag. Background Art

[0002] Co-existing radioactive minerals are important mineral resources in my country, carrying certain amounts of radioactive elements such as uranium and thorium. During the smelting process, uranium and thorium accumulate in smelting waste, forming radioactive residues. Hydrometallurgical wastes, such as those from the zirconium and vanadium industries, contain significant amounts of silicates and 0.3% to 1.5% uranium. Currently, smelters both domestically and internationally dispose of these radioactive residues by stockpiling them, which not only imposes significant environmental pressures but also wastes valuable elements.

[0003] Research on the recovery of radioactive elements from radioactive waste residues is relatively extensive, with methods often employed, such as roasting pretreatment, enhanced leaching, and multi-stage leaching. Hu Eming et al. (Method for Leaching Uranium from Uranium-Containing Waste Residues, CN 108034843A) proposed a method for leaching uranium from uranium-containing waste residues. The method comprises stirring the uranium-containing waste residue with water, stirring it with acid, heating and aging it, leaching it with water and stirring it, centrifuging it, and finally washing the insoluble residue. This method can achieve a uranium leaching rate of 88% to 97%. While this method has a simple leaching process, it requires a high amount of leaching acid (50% to 400%), heating and aging it, and the leached residue requires frequent washing (3 to 5 times), with a high water consumption (50% to 200%). This method also consumes a lot of energy and energy, and produces a large amount of wastewater. Wang Qingliang et al. (Method for Leaching Uranium from Radioactive Alkali Slag, CN 105969987A) proposed a multi-stage countercurrent dissolution and leaching method for uranium-containing alkaline slag, with a cyclic process of alkaline slag dissolution, filtration, washing of insoluble slag, filtration, first-stage leaching of insoluble slag, clarification, second-stage leaching of insoluble slag, filtration, first-stage washing of leached slag, clarification, second-stage washing of leached slag, and filtration. The leaching agent was nitric acid solution. This method was also limited by the high equipment requirements for nitric acid leaching and the need for multiple leaching and washing stages, which made the equipment operation cumbersome. Liu Rongli et al. (Method for Recovering Radioactive Elements from Zirconium Industrial Waste Slag, CN 110373556A) proposed a method of alkali-roasting zirconium industrial waste slag, leaching the calcined slag with water, filtering, and washing it to obtain a filter residue containing uranium and thorium. The filter residue was dissolved in concentrated nitric acid and then subjected to extraction, washing, impurity removal, and step-by-step stripping. This method basically achieves the recovery of radioactive elements uranium and thorium in waste slag, but its application is limited by technical problems such as high equipment requirements for nitric acid leaching, large amount of reagents used and high cost, incomplete recovery of valuable elements, and difficulty in treating and comprehensively utilizing the three wastes.

[0004] Silicon in high-silicon waste residues is mostly present in the form of silicic acid, which will increase reagent consumption during the leaching process; the transformation of silicon morphology during the leaching process will affect the solid-liquid separation, and the formation of silica gel is easy to be mixed with valuable metals, affecting the metal leaching rate. There are relatively few research reports on the recovery and utilization of silicon in high-silicon waste residues. Most of the related research reports are about directly preparing mesoporous molecular sieves, cement concrete admixtures and other products from silicon slag. Liu Xianjian et al. (A method for efficient recovery and utilization of zirconium silicon in zirconium slag, CN112591758B) proposed to obtain high-activity zirconium silicate ash by crushing the zirconium slag, dehydrating it by roller extrusion, and calcining it; mixing the high-activity zirconium silicate ash with liquid alkali and heating it for reaction, cyclone-separating the reaction mixture to obtain centrifuge and zirconium slurry, drying and calcining the zirconium slurry to obtain zirconium silicate, mixing the centrifuge with microsilica powder, adding magnesium oxide, and obtaining a liquid ceramic mud degumming agent. This method does not consider the treatment and recovery of radioactive elements uranium and thorium in the slag, and the method only considers the recycling of zirconium and silicon in the zirconium slag. The zirconium and silicon content in the zirconium slag is relatively low, and the economic value is low. Xu Lina et al. (Cement concrete admixture prepared using acidic zirconium-silicon slag and preparation method thereof, CN 103159415B) proposed to prepare cement concrete admixture by calcining acidic zirconium-silicon slag and adding activators. Rao Jian et al. (A method for treating acid-leached high-silicon slag by low-temperature alkaline roasting, CN119330364A) proposed to mix the acid-leached high-silicon slag with an alkaline reagent, perform alkaline roasting, and water-leach the roasted product to obtain a sodium silicate solution and water-leached slag.

[0005] That is, the existing technology has the following problems:

[0006] (1) For the recovery of uranium from radioactive high-silicon waste, the existing technology mostly uses concentrated nitric acid (CN 105969987A, CN110373556 A) as a leaching agent. Although a high uranium leaching rate can be achieved, concentrated nitric acid is highly corrosive, and the application of the technology is limited by the high equipment requirements for nitric acid leaching.

[0007] (2) Existing technologies for recovering uranium from uranium-containing waste slag mostly use methods such as alkaline roasting (CN 110373556A), chlorination roasting (CN115491527A) and acid roasting and aging (CN 108034843A) to pretreat the uranium-containing waste slag. These methods can destroy the waste slag structure and enhance the leaching efficiency. However, the application of these technologies requires the addition of roasting equipment, resulting in high process energy consumption and increased environmental risks in the treatment of roasting waste gas.

[0008] (3) In order to improve the dissolution and leaching rate of uranium, the existing technology often adopts multi-stage countercurrent leaching (CN 105969987A), large washing ratio, and multiple washing (CN 108034843A). This method will increase the solid-liquid separation process, resulting in a long process flow and large equipment investment. In addition, there is a large amount of uranium-containing wastewater, which increases the risk of wastewater treatment.

[0009] In summary, uranium extraction and recovery from uranium-containing waste residues often utilize enhanced methods such as high-acid, high-temperature roasting or maturation, or employ multi-stage leaching and washing steps to enhance leaching efficiency. These methods suffer from limitations such as high reagent and energy consumption, and lengthy process routes. Furthermore, the silicon in high-silicon waste residues readily forms a gel during acidic leaching. Therefore, roasting, high-temperature, high-pressure hydrothermal treatment, and other methods are commonly employed during the disposal and recovery of high-silicon waste residues to achieve stable silicon conversion. Summary of the Invention

[0010] The present invention aims to address the deficiencies of the prior art and provide a method for extracting and recovering uranium from radioactive high-silicon waste residue, which can improve the solid-liquid separation operation, reduce the amount of acid used, and increase the uranium leaching efficiency, thereby achieving economical and efficient extraction and recovery of uranium from radioactive high-silicon waste residue.

[0011] To this end, the present invention provides a method for leaching uranium from radioactive high-silicon waste slag, the leaching method comprising:

[0012] (1) Adjust the moisture content:

[0013] Adjusting the moisture content of radioactive high-silicon waste slag to 15wt% to 25wt% and grinding;

[0014] (2) Acidification and ripening:

[0015] Add concentrated sulfuric acid, mix well and let stand for aging;

[0016] (3) Second stage countercurrent leaching:

[0017] Add the second stage leaching solution and mix, carry out the first stage leaching, filter to obtain the first stage leaching solution and the first stage leaching residue;

[0018] The first stage leaching residue is mixed with sulfuric acid solution, and the second stage leaching is carried out, and the second stage leaching liquid and the second stage leaching residue are obtained by filtration;

[0019] The second stage leaching liquid is returned as the leachate of the first stage leaching;

[0020] (4) Uranium separation and recovery:

[0021] The first stage leachate is subjected to extraction and separation to recover uranium;

[0022] The uranium-loaded organic phase is stripped with Na2CO3 solution and precipitated through a NaOH solution cycle to produce a uranium concentrate product;

[0023] After stripping, the organic phase is returned to the uranium extraction cycle.

[0024] The above-mentioned method for leaching uranium from radioactive high-silica waste slag improves the existing extraction and recovery process of uranium from waste slag, increases the uranium leaching rate and recovery rate, reduces the reagent cost of the extraction and recovery process, shortens the process flow, reduces equipment investment, and realizes the efficient and economic recovery of uranium from radioactive high-silica waste slag.

[0025] The above-mentioned method for leaching uranium from radioactive high-silicon waste slag adopts a drying method to adjust the moisture content of the waste slag and thus adjust the form of silicon in the waste slag. The room temperature mixing acid maturation method-two-stage countercurrent leaching method realizes the waste slag volume and amount reduction and efficient uranium leaching. The room temperature mixing acid maturation method realizes the control of the organic metal phase in the waste slag. The flow direction of the waste slag and the leaching agent in the leaching process is finely controlled to maximize the acidolysis efficiency of the leaching agent and reduce the reagent consumption. At the same time, by controlling the pH of the leaching process, the slurry colloidalization is improved, the solid-liquid separation of the slurry is improved, and the damage of the leached slag uranium entrainment is reduced, thereby realizing efficient and economical extraction of uranium from high-silicon waste slag.

[0026] As a preferred embodiment, in step (1) of the method for leaching uranium from radioactive high-silicon waste slag, the raw material radioactive high-silicon waste slag meets at least one of the following characteristics:

[0027] The water content of the radioactive high-silicon waste residue is 55wt% to 80wt%;

[0028] The radioactive high-silicon waste slag has a uranium content of 0.5-3.0 wt% and a SiO2 content of ≥25 wt%;

[0029] In addition to uranium, the metal elements in the radioactive high-silicon waste slag also include at least one of Na, Fe, Zr and RE.

[0030] As a preferred embodiment, step (1) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag satisfies at least one of the following characteristics:

[0031] Adjusting the moisture content of radioactive high-silicon waste residue by drying;

[0032] Dry the radioactive high-silicon waste residue at room temperature for more than 48 hours;

[0033] Place the radioactive high-silicon waste residue in an oven at 90℃~100℃ and dry it for more than 12 hours;

[0034] Grinding uses disc milling and / or rod milling;

[0035] After grinding, the waste slag with a particle size of ≤5mm accounts for ≥90%.

[0036] As a preferred embodiment, step (2) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag satisfies at least one of the following characteristics:

[0037] The amount of concentrated sulfuric acid added is 10 wt% to 30 wt% relative to the dried radioactive high-silicon waste residue;

[0038] The mixing method is mechanical stirring, which optionally meets the following conditions: the mechanical stirring time is 2h to 4h;

[0039] The temperature for standing and aging is room temperature;

[0040] The standing and maturation time is 2h to 24h.

[0041] As a preferred embodiment, step (3) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag satisfies at least one of the following characteristics:

[0042] The first stage leaching: the liquid-to-solid ratio of the second stage leaching liquid and the radioactive high-silicon waste slag clinker after acid aging is (0.5-2.0L):1kg;

[0043] The second stage of leaching: the liquid-solid ratio of the sulfuric acid solution to the first stage leaching residue is (2.0-4.0L):1kg.

[0044] As a preferred embodiment, step (3) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag satisfies at least one of the following characteristics:

[0045] The temperature of the first leaching stage is room temperature;

[0046] The first leaching time is 2 to 4 hours.

[0047] As a preferred embodiment, step (3) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag satisfies at least one of the following characteristics:

[0048] The concentration of the sulfuric acid solution leached in the second stage is 150g / L to 250g / L;

[0049] The pH of the second leaching process is ≤ 0.5;

[0050] The temperature of the second leaching stage is 70℃~95℃;

[0051] The second leaching time is 4h to 6h.

[0052] As a preferred embodiment, the extraction agent used in the above-mentioned method for leaching uranium from radioactive high-silicon waste residue includes:

[0053] 5-10vt% trioctyldecyl tertiary amine, 5-20vt% auxiliary agent, and the balance is sulfonated kerosene;

[0054] The auxiliary agent is tributyl phosphate and / or secondary octanol.

[0055] Uranium is extracted and recovered using an extractant. Based on the high separation coefficient of trioctyldecyl tertiary amine (N235) extraction system for uranium and other metals, efficient separation and recovery of uranium can be achieved through multi-stage extraction. The raffinate and organic phase can be recycled. The uranium leaching difference in the entire process is small, and the uranium recovery rate is high.

[0056] As a preferred embodiment, in step (4) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag, the extraction and separation of the uranium from a first-stage leaching solution satisfies at least one of the following characteristics:

[0057] The volume ratio of the organic phase to the aqueous phase is 1:1 to 5;

[0058] The extraction temperature is 20-40°C;

[0059] After 3 to 5 levels of countercurrent extraction.

[0060] As a preferred embodiment, in step (4) of the above-mentioned method for leaching uranium from radioactive high-silicon waste slag, the stripping satisfies at least one of the following characteristics:

[0061] The concentration of Na2CO3 is 100-200g / L;

[0062] The back extraction temperature is 20-40°C;

[0063] After 3 to 5 stages of countercurrent stripping;

[0064] The concentration of NaOH solution is 350-450 g / L.

[0065] Compared with the closest prior art, the technical advantages of the present invention are:

[0066] Radioactive high-silica waste residues have many components, low valuable metal content, and difficult solid-liquid separation in the leaching slurry. Existing technologies suffer from technical problems such as lengthy process flows, high requirements for leaching pretreatment equipment and energy consumption, and highly corrosive leaching agents. To address these existing technical issues, the present invention comprehensively considers uranium extraction efficiency, solid-liquid separation, and leaching agent utilization efficiency, and proposes a method for leaching uranium from radioactive high-silica waste residues. The method has the following technical advantages:

[0067] High uranium recovery rate. By adopting a drying method to adjust the moisture content, acid-mixed maturation, and two-stage countercurrent leaching, efficient uranium leaching from high-silicon waste slag is achieved, with a uranium leaching rate exceeding 98%. Precise control of the moisture content during the maturation process and the pH during the leaching process inhibits colloidization during the leaching process, improves solid-liquid separation, and reduces slag carryover losses. The leachate is recovered through N235+octanol / TBP extraction, resulting in a low leaching return difference throughout the entire process.

[0068] The reagent cost is low and the equipment investment is small. The leaching agent of the present invention adopts sulfuric acid commonly used in uranium mining and metallurgy, which is low in cost, easy to obtain, and has low equipment requirements. The drying method and room temperature acid mixing and maturation in the pretreatment stage do not require the use of high-temperature and high-pressure equipment. Conventional stirring leaching equipment can meet the operation requirements. The leaching agent sulfuric acid is added in different stages, and is added to the acid mixing and maturation and the second stage leaching respectively. The second stage leachate returns to the first leaching process and is stirred and leached with the acid mixing and maturation clinker, which can improve the utilization rate of sulfuric acid and reduce acid consumption.

[0069] The three wastes generated are minimal, reducing environmental impact. The present invention reduces the volume of high-silicon waste slag to less than 30%, lowering the residual uranium content in the slag to below the radioactivity exemption value, significantly minimizing environmental impact. The entire process involves no high-temperature operation, no acid gas generation, and the raffinate can be returned to the leaching agent. The lean organic phase can be recycled, and the entire process generates no wastewater.

[0070] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The present invention is a process flow chart of a specific embodiment of a method for leaching uranium from radioactive high-silicon waste slag. DETAILED DESCRIPTION

[0072] In the following description, a number of specific details are provided to provide a more thorough understanding of the technical solutions provided by the present invention. However, it is obvious to those skilled in the art that the technical solutions provided by the present invention can be implemented without one or more of these details.

[0073] In the examples and comparative examples of the present invention, the raw materials are commercially available.

[0074] In the examples and comparative examples of the present invention, the liquid-to-solid ratio refers to the liquid volume (L): solid weight (kg).

[0075] Example 1

[0076] A radioactive high-silicon waste slag has a moisture content of 57.1%, a U content of 0.98%, a SiO2 content of 29.8%, a REO content of 9.5%, a SiO2 content of 25%, a Fe2O3 content of 11.2%, and a ZrO2 content of 10.3%.

[0077] refer to Figure 1The radioactive high-silicon waste slag was spread out and placed in a crucible and placed at room temperature for 48 hours. The moisture content of the slag after drying was 18.4%. After treatment, the waste slag was disc-milled for 2 minutes, and the portion of waste slag with a particle size of ≤5mm accounted for more than 90%.

[0078] Concentrated sulfuric acid was added to the dried waste residue at a mass fraction of 20%, and the slurry was mechanically stirred for 2 hours and then aged at room temperature for 6 hours.

[0079] The radioactive high-silicon waste clinker after acid aging was weighed and added to a second-stage leachate at a leachate-to-solid ratio of 2.0:1. The mixture was stirred and leached at room temperature for 4 hours. The first-stage leachate and first-stage leachate residue were filtered to obtain a first-stage leachate and first-stage leachate residue. The first-stage leachate was used for extraction and separation to recover uranium. The uranium leaching rate reached 78.5% based on the first-stage leachate residue. The first-stage leachate residue was mixed with 200g / L sulfuric acid solution at a leachate-to-solid ratio of 3.0:1. The leaching process was controlled at a pH of 0.15, a leaching temperature of 90°C, and a leaching time of 4 hours. The second-stage leachate and second-stage leachate residue were filtered to obtain a second-stage leachate and second-stage leachate residue. The second-stage leachate was returned as the leachant for the first-stage leachate. The uranium leaching rate reached 98% based on the leachate residue, the residue yield was 25%, and the uranium content in the residue was 0.02%.

[0080] The first-stage leach solution uses 10% nitrogen-235 (Vt%), 5% tributyl phosphate (TBP), 5% sec-octanol, and the balance sulfonated kerosene to extract uranium. The organic phase is extracted with a volume ratio of 1:2 (O / A) at 40°C. After five stages of countercurrent extraction, the uranium concentration in the solution is reduced to 0.8 mg / L, with a uranium extraction efficiency of 99.1%. The uranium-laden organic phase is stripped with 200 g / L sodium carbonate (Na2CO3) at 40°C. After five stages of countercurrent stripping, a qualified uranium solution is obtained. This solution is then precipitated with 400 g / L sodium hydroxide (NaOH) to produce a uranium concentrate. The organic phase, after stripping, is recycled back to the uranium extraction process.

[0081] Example 2

[0082] A radioactive high-silicon waste slag has a moisture content of 60.3%, a U content of 0.73%, a SiO2 content of 32.2%, a REO content of 8.9%, a Fe2O3 content of 12.6%, and a ZrO2 content of 11.7%.

[0083] refer to Figure 1 The radioactive high-silicon waste slag was spread out in a crucible and placed in a 90°C oven for 12 hours. The moisture content of the slag after drying was 16.0%. The waste slag was rod-milled for 5 minutes after treatment, and the proportion of waste slag particles ≤5mm accounted for more than 90%.

[0084] Concentrated sulfuric acid was added to the dried waste residue at a mass fraction of 18%, and the slurry was mechanically stirred for 3 hours and then aged at room temperature for 4 hours.

[0085] The radioactive high-silicon waste clinker after acid aging was weighed and added to a second-stage leachate at a leachate-to-solid ratio of 1.5:1.0. The mixture was stirred and leached at room temperature for 4 hours. The first-stage leachate and first-stage leachate residue were filtered. The first-stage leachate was used for extraction and separation to recover uranium. The uranium leaching rate reached 75.7% based on the first-stage leachate residue. The first-stage leachate residue was mixed with 220g / L sulfuric acid solution at a leachate-to-solid ratio of 4.0:1. The leaching process was controlled at a pH of 0.10, a leaching temperature of 95°C, and a leaching time of 6 hours. The second-stage leachate and second-stage leachate residue were filtered. The second-stage leachate was returned as the leachant for the first-stage leachate. The uranium leaching rate reached 99.2% based on the leachate residue, the slag yield was 23%, and the uranium content in the slag was 0.01%.

[0086] The first-stage leach solution uses 5% nitrogen (N₂₃₅)₅₅-5% ​​tributyl phthalate (TBP)₅₅-octanol (5% sec-octanol), with the remainder being sulfonated kerosene, to extract uranium. The organic phase is extracted at a volume ratio of 1:3 (O / A) and a temperature of 40°C. After three stages of countercurrent extraction, the uranium concentration in the solution is reduced to 1.0 mg / L, with a uranium extraction efficiency of 99.5%. The uranium-laden organic phase is then stripped with 150 g / L sodium carbonate (Na₂CO₃) solution at 40°C. After three stages of countercurrent stripping, a qualified uranium solution is obtained. This solution is then precipitated with 400 g / L sodium hydroxide solution to produce a uranium concentrate. The organic phase after stripping is then recycled back to the uranium extraction process.

[0087] Example 3

[0088] A radioactive high-silicon waste slag has a moisture content of 75.0%, a U content of 1.09%, a SiO2 content of 35.1%, a REO content of 7.9%, a Fe2O3 content of 10.4%, and a ZrO2 content of 12.3%.

[0089] refer to Figure 1 The radioactive high-silicon waste slag was spread out and placed in a crucible and placed at room temperature for 72 hours. The moisture content of the slag after drying was 17.8%. After treatment, the waste slag was disc-milled for 5 minutes, and the waste slag particle size ≤5mm accounted for more than 90%.

[0090] Concentrated sulfuric acid was added to the dried waste residue at a mass fraction of 25%, and the slurry was mechanically stirred for 4 hours and then aged at room temperature for 4 hours.

[0091] The radioactive high-silicon waste clinker after acid aging was weighed and added to a second-stage leachate at a leachate-to-solid ratio of 2.0:1.0. The mixture was stirred and leached at room temperature for 3 hours. The first-stage leachate and first-stage leachate residue were filtered. The first-stage leachate was used for extraction and separation to recover uranium. The uranium leaching rate reached 78.6% based on the first-stage leachate residue. The first-stage leachate residue was mixed with 150g / L sulfuric acid solution at a leachate-to-solid ratio of 3.5:1.0. The leaching process was controlled at a pH of 0.20, a leaching temperature of 90°C, and a leaching time of 5 hours. The second-stage leachate and second-stage leachate residue were filtered. The second-stage leachate was returned as the leachant for the first-stage leachate. The uranium leaching rate reached 98.9% based on the leachate residue, the slag yield was 27%, and the uranium content in the slag was 0.02%.

[0092] The first-stage leach solution uses 10% nitrogen-235 (Vt) + 10% TBP + 10% sec-octanol + the balance sulfonated kerosene to extract uranium. The organic phase is extracted with an organic / aqueous phase volume ratio of 1:5 (O / A) at 30°C. After five stages of countercurrent extraction, the uranium concentration in the solution is reduced to 0.7 mg / L, with a uranium extraction efficiency of 99.5%. The uranium-laden organic phase is stripped with 200 g / L sodium-2CO3 solution at 40°C. After five stages of countercurrent stripping, a qualified uranium solution is obtained. This solution is then precipitated with 400 g / L sodium hydroxide solution to produce a uranium concentrate. The organic phase after stripping is then recycled back to the uranium extraction process.

[0093] Comparative Example 1

[0094] Method for leaching uranium from uranium-containing waste residue, CN 108034843 A

[0095] A. Acid aging of uranium-containing waste residue

[0096] The uranium-containing waste residue S is placed in a stirring barrel, water is added and stirred evenly, and then concentrated sulfuric acid is added and stirred evenly. After stirring evenly, the mixture is transferred to a rotary kiln for heat preservation and aging at a temperature of 220° C. for 5 hours.

[0097] Among them, the mass ratio of uranium-containing waste residue to water and concentrated sulfuric acid is 1:0.2:2.

[0098] (Compared with Comparative Example 1, the amount of acid used in this application is significantly reduced. At the same time, according to the different moisture contents of the waste residue, the residue:water ratio is controlled at an appropriate ratio before acid aging, the residual acid in the system is adjusted, and the acidolysis effect is enhanced, which has the same effect as Comparative Example 1.)

[0099] B. Add water and stir to leach. The uranium-containing waste residue after acid aging is cooled to room temperature and then taken out. It is transferred to a stirred reactor, and water and washing liquid L2 are added, followed by heating and stirring. The heating and stirring temperature is 75°C. After stirring evenly, the heating is stopped, and the mixture is allowed to react for 3 hours to obtain a solid-liquid mixed slurry.

[0100] Among them, the mass ratio of uranium-containing waste slag after acid aging to water is 1:10.

[0101] C. Centrifugal filtration

[0102] The solid-liquid mixed slurry is pumped into a centrifugal filter for filtration to obtain a leachate L1 and a first-level insoluble slag S1. The leachate L1 is sent to a uranium recovery process to recover uranium.

[0103] D. First-level insoluble residue S1 washing

[0104] The first-level insoluble residue S1 is washed with water in a centrifugal filter, and then centrifuged and filtered. The operation is repeated 4 times. The washing liquid L2 after each washing is returned to step B as the leaching liquid. After the washing is completed, the second-level insoluble residue S2 is obtained.

[0105] In each washing process, the mass ratio of the first-level insoluble residue S1 to water is 1:1.2.

[0106] E. Secondary insoluble slag S2 is stored dry

[0107] The washed secondary insoluble slag S2 is dried in an oven and then stored in a disposal site.

[0108] By using the above method to treat uranium-containing waste residue, the dissolution rate of the uranium-containing waste residue is 50%, the uranium leaching rate is 95%, and the remaining uranium content in the secondary insoluble slag S2 can be reduced to 0.1%.

[0109] Comparative Example 2

[0110] A method for recycling uranium and vanadium precipitation mother liquor, CN 202011355466.5

[0111] A vanadium ore containing 0.572% vanadium was treated with concentrated acid aging-leaching process, and vanadium was extracted and recovered from the leachate. The qualified vanadium solution (obtained from sulfuric acid stripping) was used to prepare vanadium products using acidic ammonium salt precipitation process. The amount of vanadium precipitation mother liquor produced was 8.9wt% (based on the weight of the original ore), containing 0.150g / L of V and NH4 + 115.6g / L, pH 1.53. All vanadium precipitation mother liquor is returned to leaching. The specific steps are as follows:

[0112] (1) Ore crushing and grinding: Ore is crushed and ground to -60 mesh (accounting for 90%).

[0113] (2) Leaching: The ore in step (1) is subjected to concentrated acid aging-high temperature leaching. 8 wt% water and 28 wt% sulfuric acid are added to the ore, mixed well, and sealed. The ore is aged at 90°C for 24 h. The aged material is leached at 96°C. 8.9 wt% vanadium precipitation mother liquor and 71 wt% water are added. The solid volume mass ratio of the leachate is controlled to be 1. Calcium oxide is added as a neutralizing agent during the leaching process. The amount of calcium oxide is 2 wt% (based on the mass of the ore). The pH of the leaching process is adjusted to 1.32, and the leaching time is 2 h.

[0114] (In Comparative Example 2, the acid was added in sufficient amounts during the concentrated acid aging process. The vanadium precipitation mother liquor and the calcium oxide neutralization precipitate both served to adjust the pH. Compared to Comparative Example 2, the acid in this application was added in two stages: first, during the concentrated acid aging step, and second, during the second-stage leaching to adjust the pH. To improve acid utilization efficiency and ensure the leaching effect of the uranium-containing waste residue, a drying method was used to adjust the slag moisture content before aging to ensure that the waste residue was exposed to high acid concentration conditions during the aging process, thereby enhancing the leaching effect. Second, a two-stage countercurrent leaching process was adopted, with the first-stage leaching raw material being the acidified clinker and the second-stage leachate being the leaching agent. This process has the following functions: 1) maintaining a high residual acid level in the leaching system; and 2) utilizing the residual acid in the second-stage leachate, eliminating the need for additional acid addition in the first-stage leaching, thereby improving acid utilization efficiency.)

[0115] (3) Solid-liquid separation: After leaching in the above step (2), the slurry is vacuum filtered, and the filter cake is washed with 5g / L dilute sulfuric acid in four stages of countercurrent, and the filter cake and leachate are obtained after solid-liquid separation.

[0116] (4) Metal separation and recovery: Extraction and recovery of vanadium in the leachate after solid-liquid separation in step (3) to obtain a qualified vanadium solution and a raffinate aqueous phase.

[0117] (5) Precipitation: The qualified vanadium solution in step (4) is precipitated, and the qualified vanadium solution is precipitated to prepare ammonium vanadate by acidic ammonium salt precipitation. After solid-liquid separation, the precipitated slurry is subjected to ammonium vanadate and vanadium precipitation mother liquor. The precipitation mother liquor is returned to leaching. Under the same experimental conditions as in the above steps, when the precipitation mother liquor is not returned to leaching, the vanadium leaching rate is 78.9%, and the iron concentration in the leachate is 9.85g / L; after the uranium and vanadium precipitation mother liquors are returned to leaching, the uranium and vanadium leaching rates are 77.4%, respectively, and the iron concentration in the leachate is 3.21g / L. Compared with the case when the precipitation mother liquor is not returned to leaching, the vanadium leaching rate does not change significantly, and the iron concentration in the leachate is greatly reduced. While realizing the recycling of the precipitation mother liquor, the dissolution of iron is effectively suppressed.

[0118] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for leaching uranium from radioactive high-silicon waste residue, characterized in that: The leaching method comprises: (1) Adjust the moisture content: Adjusting the moisture content of radioactive high-silicon waste slag to 15wt% to 25wt% and grinding; (2) Acidification and ripening: Add concentrated sulfuric acid, mix well and let stand for aging; (3) Second stage countercurrent leaching: Add the second stage leaching solution and mix, carry out the first stage leaching, filter to obtain the first stage leaching solution and the first stage leaching residue; The first stage leaching residue is mixed with sulfuric acid solution, and the second stage leaching is carried out, and the second stage leaching liquid and the second stage leaching residue are obtained by filtration; The second stage leaching liquid is returned as the leachate of the first stage leaching; (4) Uranium separation and recovery: The first stage leachate is subjected to extraction and separation to recover uranium; The uranium-loaded organic phase is stripped with Na2CO3 solution and precipitated through a NaOH solution cycle to produce a uranium concentrate product; After stripping, the organic phase is returned to the uranium extraction cycle.

2. The method for leaching uranium from radioactive high-silicon waste according to claim 1, characterized in that: The radioactive high-silicon waste residue meets at least one of the following characteristics: The water content of the radioactive high-silicon waste residue is 55wt% to 80wt%; The radioactive high-silicon waste slag has a uranium content of 0.5-3.0 wt% and a SiO2 content of ≥25 wt%; In addition to uranium, the metal elements in the radioactive high-silicon waste slag also include at least one of Na, Fe, Zr and RE.

3. The method for leaching uranium from radioactive high-silicon waste according to claim 1, characterized in that: Step (1) satisfies at least one of the following characteristics: Adjusting the moisture content of radioactive high-silicon waste residue by drying; Dry the radioactive high-silicon waste residue at room temperature for more than 48 hours; Place the radioactive high-silicon waste residue in an oven at 90℃~100℃ and dry it for more than 12 hours; Grinding uses disc milling and / or rod milling; After grinding, the waste slag with a particle size of ≤5mm accounts for ≥90%.

4. The method for leaching uranium from radioactive high-silicon waste according to claim 1, characterized in that: Step (2) satisfies at least one of the following characteristics: The amount of concentrated sulfuric acid added is 10 wt% to 30 wt% relative to the dried radioactive high-silicon waste residue; The mixing method is mechanical stirring, which optionally meets the following conditions: the mechanical stirring time is 2h to 4h; The temperature for standing and aging is room temperature; The standing and maturation time is 2h to 24h.

5. The method for leaching uranium from radioactive high-silicon waste according to claim 1, characterized in that: Step (3) satisfies at least one of the following characteristics: The first stage leaching: the liquid-to-solid ratio of the second stage leaching liquid and the radioactive high-silicon waste slag clinker after acid aging is (0.5-2.0L):1kg; The second stage of leaching: the liquid-solid ratio of the sulfuric acid solution to the first stage leaching residue is (2.0-4.0L):1kg.

6. The method for leaching uranium from radioactive high-silicon waste residue according to claim 1, characterized in that: Step (3) satisfies at least one of the following characteristics: The temperature of the first leaching stage is room temperature; The first leaching time is 2 to 4 hours.

7. The method for leaching uranium from radioactive high-silicon waste slag according to claim 1, characterized in that: Step (3) satisfies at least one of the following characteristics: The concentration of the sulfuric acid solution leached in the second stage is 150g / L to 250g / L; The pH of the second leaching process is ≤ 0.5; The temperature of the second leaching stage is 70℃~95℃; The second leaching time is 4h to 6h.

8. The method for leaching uranium from radioactive high-silicon waste residue according to claim 1, characterized in that: The extractants used for extraction separation include: 5-10vt% trioctyldecyl tertiary amine, 5-20vt% auxiliary agent, and the balance is sulfonated kerosene; The auxiliary agent is tributyl phosphate and / or secondary octanol.

9. The method for leaching uranium from radioactive high-silicon waste slag according to claim 1, characterized in that: In step (4), the extraction and separation of the first-stage leaching solution to recover uranium satisfies at least one of the following characteristics: The volume ratio of the organic phase to the aqueous phase is 1:1 to 5; The extraction temperature is 20-40°C; After 3 to 5 levels of countercurrent extraction.

10. The method for leaching uranium from radioactive high-silicon waste slag according to claim 1, characterized in that: The back extraction in step (4) satisfies at least one of the following characteristics: The concentration of Na2CO3 is 100-200g / L; The back extraction temperature is 20-40°C; After 3 to 5 stages of countercurrent stripping; The concentration of NaOH solution is 350-450 g / L.

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