A method for extracting uranium from monazite alkali cake

Abstract

The present invention discloses a method for extracting uranium from monazite alkali cake. The method comprises the following steps: stirring the monazite alkali cake with water to form a slurry to obtain a mixed slurry 1; then adding concentrated hydrochloric acid to the mixed slurry 1 and stirring the mixture to obtain a leaching slurry; adding a polyethylene glycol aqueous solution to the leaching slurry to remove silicon by flocculation, and filtering to obtain an alkali cake leachate and a filter cake; adding a mixed extractant of trioctyldecyl tertiary amine, tributyl phosphate, and sulfonated kerosene to the alkali cake leachate to extract uranium and iron, thereby obtaining an organic-loaded extract and a raffinate; adding a stripping agent to the organic-loaded extract to obtain a stripping solution and a lean organic phase; adding a sodium hydroxide solution to the stripping solution to control the pH of the stripping solution to 2.5-3, and filtering to obtain iron hydroxide and a filtrate; and adding solid sodium hydroxide to the filtrate to obtain a sodium diuranate precipitate. The present invention aims to improve the uranium extraction rate from monazite.

Description

Technical Field

[0001] The invention relates to the technical field of monazite smelting, and in particular to a method for extracting uranium from monazite alkali cake. Background Art

[0002] At present, monazite is one of the most widely distributed rare earth minerals. It is rich in precious resources such as rare earth, uranium, and thorium. Monazite concentrate is mainly used to extract rare earth chloride and phosphorus. Among them, most companies engaged in monazite smelting and production use caustic soda leaching technology. The alkali cake produced enters the subsequent hydrochloric acid dissolution process to produce rare earth chloride. The dissolution slag produced in this process can be used for uranium recovery processing.

[0003] Existing patent application CN116574928A discloses a method for recovering uranium from monazite slag. The method comprises the following steps: acid leaching the monazite slag with hydrochloric acid A to obtain a leached pulp; the concentration of the hydrochloric acid A is 4 to 10 mol / L; solid-liquid separation is performed on the leached pulp to obtain a leachate; the leachate is mixed with an extractant A and subjected to extraction and iron removal to obtain an iron-loaded organic phase and an iron raffinate; the extractant A comprises, by volume percentage, 4 to 10% of an amine extractant and 5 to 20% of a fatty alcohol extractant. and kerosene remainder; the volume content of the fatty alcohol extractant in the extractant A is greater than the volume content of the amine extractant; the iron raffinate is mixed with extractant B to extract uranium to obtain a uranium-loaded organic phase and a uranium raffinate; in terms of volume percentage, the extractant B comprises 5-20% amine extractant, 1-10% fatty alcohol extractant, and kerosene remainder; the volume content of the amine extractant in the extractant B is greater than the volume content of the fatty alcohol extractant; the uranium-loaded organic phase is stripped with hydrochloric acid B to obtain a qualified uranium solution. The above-mentioned process of using hydrochloric acid to dissolve the slag and extracting and recovering uranium with the clear solution after filtration has the following difficulties: ① The silicon content in the clear solution of the complete dissolution filtration is about 3g / L, which forms a third phase flocculent layer with the organic phase during the stripping process. The third phase material accumulated over a long period of operation seriously affects the operational stability of the extraction phase. ② The acid solution of the whole slag is designed to ensure slurry fluidity and a high chloride ion concentration in the filtered clear solution. The residual acid in the whole slag solution must reach above 2.5 mol / L. However, hydrochloric acid mist severely corrodes equipment, and filtering the whole slag is difficult, resulting in low uranium extraction efficiency. ③ The raffinate must be returned to the slag leaching process. During this continuous process cycle, small amounts of elements such as titanium, silicon, and zirconium in the solution gradually accumulate in the leachate, further affecting the stability of the extraction and stripping system. Consequently, a new uranium extraction method is urgently needed to address these issues. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for extracting uranium from monazite alkali cake, aiming to solve the technical problem of low efficiency of uranium extraction using monazite slag.

[0005] To achieve the above object, the present invention provides a method for extracting uranium from monazite alkali cake, the method comprising the following steps:

[0006] Step 1: stir monazite alkali cake with a preset amount of water to obtain a mixed slurry 1, then add a preset volume of concentrated hydrochloric acid to the mixed slurry 1, stir and react for a preset time to obtain a leaching slurry, wherein the mass volume ratio of monazite alkali cake to concentrated hydrochloric acid is 1t: (1~1.5)m 3 , the residual acid H in the leaching pulp + The concentration is 0.3~0.8mol / L;

[0007] Step 2: adding a polyethylene glycol aqueous solution to the leached slurry to remove silicon by flocculation, and filtering to obtain an alkaline cake leachate and a filter cake;

[0008] Step 3, adding trioctyldecyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant to the alkali cake leachate for extraction treatment to co-extract uranium and iron, thereby obtaining an organic phase-loaded extract and a raffinate, wherein the volume ratio of trioctyldecyl tertiary amine to tributyl phosphate is 1:1, the trioctyldecyl tertiary amine accounts for 10-20% of the total volume of the mixed extractant, and the flow rate ratio of the alkali cake leachate to the mixed extractant is (1.5-2):1;

[0009] Step 4, adding a stripping agent to the organic phase-loaded extract to perform stripping treatment to obtain a stripping solution and a lean organic phase, wherein the stripping agent is an aqueous liquid, and the flow rate ratio of the extract to the stripping agent is 4:1;

[0010] Step 5, adding sodium hydroxide solution to the stripping solution to control the pH value of the stripping solution to 2.5-3, and filtering to obtain ferric hydroxide and a filtrate;

[0011] Step 6: adding solid sodium hydroxide to the filtrate to control the pH value of the filtrate to 7-8 by dissolving the solid sodium hydroxide, and filtering to obtain sodium diuranate precipitate.

[0012] Optionally, the method further comprises the following steps:

[0013] The filter cake in step 2 is mixed with the raffinate in step 3, and heated to 80°C. Alkali slurry is then added to adjust the pH to 3-4. After keeping warm for 4 hours, the mixture is filtered to obtain the filtrate, which is the high-chloride rare earth solution. The alkaline slurry is the slurry obtained by adding water to the alkali cake.

[0014] Optionally, in step 1, the residual acid H in the slurry is leached + The concentration is 0.4~0.5mol / L.

[0015] Optionally, in step 1, the mass ratio of monazite alkali cake to water is 2:1.

[0016] Optionally, in step 2, the volume mass ratio of the leached slurry to the polyethylene glycol solid is 1m 3 : (2.5~10)kg, the mass fraction of polyethylene glycol in the polyethylene glycol aqueous solution is 1~20%.

[0017] Optionally, in step 4, the stripping agent is water or a 0.001-0.1 mol / L hydrochloric acid solution.

[0018] Optionally, in step 1, the stirring reaction is preset for 4 to 12 hours.

[0019] Optionally, the method further comprises the following steps:

[0020] A 2.5 mol / L hydrochloric acid solution was added to the lean organic phase, and the lean organic phase and the hydrochloric acid solution were all returned to step 3, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution was 10:1.

[0021] Optionally, in step 3, a three-stage countercurrent extraction operation is adopted in the extraction treatment.

[0022] Optionally, in step 4, 8 to 11 stages of countercurrent stripping operations are used in the stripping treatment.

[0023] Beneficial effects:

[0024] The present invention uses alkali cake slurry to react with concentrated hydrochloric acid for leaching, and controls the residual acid solubility to obtain a leached slurry. By continuing with a polyethylene glycol solution, flocculation and silicon removal are carried out, and then the filtered alkali cake leachate is first extracted with a mixed extractant of trioctanyl tertiary amine, tributyl phosphate and sulfonated kerosene to extract uranium and iron, thereby obtaining an organic phase-loaded extract. The extract is then subjected to a stripping operation through an aqueous liquid to obtain a stripping solution, which is then subjected to iron removal and impurity removal, followed by precipitation to prepare a uranium product. As can be seen, this step can recover uranium and rare earths through a single acid dissolution. The circulation of a small amount of elements is avoided, and a small amount of elements such as titanium, silicon, and zirconium enter the process of recovering rare earths with the residual extract, and eventually go to the superior dissolution slag or the rare earth removal slag. This uranium extraction method is simple, convenient and easy to operate, and can be easily promoted and used in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of an embodiment of a method for extracting uranium from monazite alkali cake according to the present invention;

[0026] Figure 2 for Figure 1 The flow chart shown.

[0027] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0028] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] See also Figure 1-2 The present invention provides a flow chart of a method for extracting uranium from monazite alkali cake, the method comprising the following steps:

[0030] Step 1: Stir the monazite alkali cake with a preset amount of water to obtain a mixed slurry 1, then add a preset volume of concentrated hydrochloric acid to the mixed slurry 1, stir and react for a preset time to obtain a leaching slurry. The mass fraction of the water content in the monazite alkali cake is 30-40%, the mass fraction of the uranium content is 0.4-0.5%, the mass fraction of the rare earth oxide is 50-65%, and the mass fraction of thorium is 6-12%. The mass ratio of the monazite alkali cake to water is 2:1, and the mass volume ratio of the monazite alkali cake to concentrated hydrochloric acid is 1t:(1-1.5)m 3 , preferably 1t:(1.1~1.2)m 3 The stirring reaction time is set to 4 to 12 hours, and the residual acid H in the leaching slurry is controlled. + The concentration is 0.3-0.8 mol / L, preferably 0.4-0.5 mol / L. The uranium content in the leached slurry is 0.8-1.6 g / L, and the rare earth oxide concentration is 180-280 g / L.

[0031] Step 2: Add polyethylene glycol solution to the leached slurry and stir for 10 to 30 minutes to remove silicon by flocculation. After filtration, obtain alkaline cake leachate and filter cake. The volume mass ratio of the leached slurry to the polyethylene glycol solid is 1m3: (2.5-10)kg, and the mass fraction of polyethylene glycol in the polyethylene glycol aqueous solution is 1-20%, preferably 5-10%. The polyethylene glycol content in the polyethylene glycol solid is 99%. Silicon is removed in advance in this step to avoid the high silicon content affecting the subsequent uranium extraction. The filtration step is achieved by plate and frame filtration, which has a better filtration effect than ordinary filtration devices.

[0032] Step 3: Add trioctyldecyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant to the alkali cake leachate for extraction treatment to extract uranium and iron together, thereby obtaining an organic phase-loaded extract and a raffinate, wherein the volume ratio of trioctyldecyl tertiary amine to tributyl phosphate is 1:1, trioctyldecyl tertiary amine accounts for 10-20% of the total volume of the mixed extractant, the flow rate ratio of the alkali cake leachate to the mixed extractant is (1.5-2):1, and a three-stage countercurrent extraction operation is used in the extraction treatment. This extraction step uses alkyl tertiary amine extraction method to extract UO2Cl4 formed in the alkali cake leachate under a high chloride ion system. 2- ions and exchange with the extracted ions.

[0033] Step 4: Add a stripping agent to the organic phase-loaded extract to perform stripping treatment to obtain a stripping solution and a lean organic phase. The stripping agent is an aqueous liquid, and the flow rate ratio of the extract to the stripping agent is 4:1. Specifically, the stripping agent is water or a 0.001-0.1 mol / L hydrochloric acid solution, preferably a 0.01-0.05 mol / L hydrochloric acid solution. In the stripping treatment, 8 to 11 stages of countercurrent stripping operation are adopted, and a 2.5 mol / L hydrochloric acid solution can be added to the lean organic phase. After mixing, the mixture is returned to step 3 to continue to be used as an extractant. Preferably, the volume ratio of the lean organic phase to the added hydrochloric acid solution is 10:1.

[0034] In step 5, sodium hydroxide solution is added to the stripping solution to control the pH value of the stripping solution to 2.5-3, and the stripping solution is filtered to obtain iron hydroxide and a filtrate. The mass fraction of the added sodium hydroxide solution is 30%. Preferably, the pH value of the stripping solution is controlled to 2.5-2.7.

[0035] Step 6: Add solid sodium hydroxide to the filtrate to control the pH of the filtrate to 7-8 by dissolving the solid sodium hydroxide, and filter to obtain sodium diuranate precipitate. Preferably, the pH of the filtrate is controlled to 7-7.5.

[0036] Furthermore, the method further comprises the following steps:

[0037] The filter cake in step 2 is mixed with the raffinate in step 3, and the mixture is heated to 80°C. The pH value is adjusted to 3-4 using alkali slurry, and the mixture is kept warm for 4 hours and filtered. The filtrate obtained is a high-chloride rare earth liquid, which is then removed from impurities, concentrated, and crystallized to obtain a rare earth chloride product, wherein the alkali slurry is a slurry obtained by adding water to the alkali cake.

[0038] The present invention adopts alkali cake slurry and concentrated hydrochloric acid reaction leaching, and controls the residual acid solubility to obtain leached ore pulp, by continuing polyethylene glycol solution, flocculation and silicon removal, then the filtered alkali cake leachate is first extracted by trioctyl decyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant, so that uranium and iron are co-extracted to obtain an extract of the loaded organic phase, and the extract is continued to be stripped by an aqueous liquid to obtain a stripping solution, which is subjected to iron removal and impurity removal liquid precipitation to prepare a uranium product. It can be seen that this step can recover uranium and rare earth by a single acid dissolution. Avoiding the circulation of a small amount of elements, a small amount of elements such as titanium, silicon, and zirconium enters the excellent dissolution and rare earth recovery process with the residual extract, and eventually goes to the excellent dissolution slag or the rare earth removal slag.

[0039] Furthermore, in order to better illustrate the process and effect of a method for extracting uranium from monazite alkali cake, the following is a detailed description through specific examples, the details are as follows:

[0040] Example 1

[0041] The monazite alkali cake has a moisture content of 40.56%. By mass percentage, the uranium content is 0.43%, the rare earth oxide content is 60.59%, and the thorium content is 10.64%.

[0042] Step 1: Add water in a mass ratio of 2:1 to make a slurry, mix the solid and liquid evenly, then add concentrated hydrochloric acid to dissolve, control the residual acid to be less than 0.8 mol / L, stir and react for 4 hours to obtain the leaching slurry. The mass volume ratio of alkali cake (dry basis): industrial concentrated hydrochloric acid is about 1t:1.5m 3 .

[0043] Step 2: Add 20% polyethylene glycol to the leached slurry at a dosage of 0.25 kg / m 3 After filtration, an alkaline cake leachate was obtained, wherein the iron content in the alkaline cake leachate was 0.47 g / L, the uranium content was 1.03 g / L, the rare earth oxide concentration was 210.06 g / L, the thorium concentration was 25.7 g / L, and the residual acid was 0.76 mol / L.

[0044] In step 3, the leachate is extracted and stripped using a mixer-settler, and a three-stage countercurrent extraction is performed using 15% trioctyldecyl tertiary amine N235 + 15% tributyl phosphate + 70% sulfonated kerosene (volume ratio) as an extractant. The oil-water flow rate ratio is 1:1.5, and an organic phase-loaded extract and a raffinate are obtained. The uranium content of the raffinate is 0.025 g / L, and the iron content is 0.016 g / L. The uranium content of the organic phase-loaded extract is 1.83 g / L.

[0045] In step 4, the organic phase-loaded extract was subjected to 8-stage countercurrent stripping using water as a stripping agent, with an oil-water flow rate ratio of 4:1. The uranium content in the stripping solution was 7.26 g / L, the iron content was 2.72 g / L, and the uranium recovery rate was 97.57%.

[0046] Step 5: The stripping solution is subjected to a step-by-step precipitation method to remove iron, and the pH is adjusted to 2.5 using 30% by mass of sodium hydroxide, and the iron hydroxide impurities are removed by filtration.

[0047] In step 6, the filtrate is precipitated with sodium diuranate using solid sodium hydroxide, with the endpoint pH controlled at 7.3. The mixture is stirred for 8 hours and then filtered to obtain a sodium diuranate product having a dry basis uranium content of 61.92%, an iron content of 0.18%, a rare earth oxide content of 0.83%, and a thorium content of 0.57%, meeting the technical requirements of the diuranate industry standard (EJ / T 803-1993).

[0048] Step 7: The uranium extract raffinate and the leaching residue are mixed to prepare a slurry, the temperature is raised to 80° C., the pH value is adjusted to 3-4 using an alkaline slurry, the filtrate is kept warm for 4 hours and then filtered. The filtrate is a high-chloride rare earth solution, which is then removed from impurities, concentrated, and crystallized to obtain a chloride rare earth product.

[0049] 2.5 mol / s hydrochloric acid solution is further added to the lean organic phase prepared in the above step, and the lean organic phase and the hydrochloric acid solution are all returned for use as an extractant, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution is 10:1.

[0050] Example 2

[0051] The monazite alkali cake has a moisture content of 36.31%. By mass percentage, the uranium content is 0.46%, the rare earth oxide content is 57.69%, and the thorium content is 7.35%.

[0052] Step 1: Add water in a mass ratio of 2:1 to make a slurry, mix the solid and liquid evenly, then add concentrated hydrochloric acid to dissolve, control the residual acid to be less than 0.4 mol / L, stir and react for 8 hours to obtain the leaching slurry. The mass volume ratio of alkali cake (dry basis): industrial concentrated hydrochloric acid is about 1t:1.0m 3 .

[0053] Step 2: Add 20% polyethylene glycol to the leached slurry at a dosage of 0.5 kg / m 3 After filtration, an alkaline cake leachate was obtained, wherein the iron content in the alkaline cake leachate was 0.87 g / L, the uranium content was 1.22 g / L, the rare earth oxide concentration was 236.92 g / L, and the residual acid was 0.31 mol / L.

[0054] In step 3, the leachate is extracted and stripped using a mixer-settler, and a three-stage countercurrent extraction is performed using 15% N235 + 15% tributyl phosphate + 70% sulfonated kerosene (volume ratio) as an extractant. The oil-water flow rate ratio is 1:2 to obtain an extract and a raffinate loaded with an organic phase. The raffinate has a uranium content of 0.027 g / L and an iron content of 0.019 g / L, and the loaded organic phase has a uranium content of 2.87 g / L.

[0055] In step 4, the organic phase-loaded extract was subjected to 11-stage countercurrent stripping using 0.1 mol / L hydrochloric acid solution as a stripping agent, with an oil-water flow rate ratio of 4:1. The uranium content in the stripping solution was 11.45 g / L, the iron content was 7.81 g / L, and the uranium recovery rate was 97.79%.

[0056] Step 5: The stripping solution is subjected to a step-by-step precipitation method to remove iron, and the pH is adjusted to 2.9 using 30% by mass of sodium hydroxide, and the iron hydroxide impurities are removed by filtration.

[0057] In step 6, the filtrate is precipitated with sodium diuranate using solid sodium hydroxide, with the endpoint pH controlled at 7.1. The product is stirred for 8 hours and then filtered to obtain a sodium diuranate product. The product has a dry basis uranium content of 60.14%, an iron content of 0.58%, a rare earth oxide content of 0.97%, and a thorium content of 0.53%, meeting the technical requirements of the diuranate industry standard (EJ / T 803-1993).

[0058] Step 7: The uranium extract raffinate and the leaching residue are mixed to prepare a slurry, the temperature is raised to 80° C., the pH value is adjusted to 3-4 using an alkaline slurry, the filtrate is kept warm for 4 hours and then filtered. The filtrate is a high-chloride rare earth solution, which is then removed from impurities, concentrated, and crystallized to obtain a chloride rare earth product.

[0059] 2.5 mol / s hydrochloric acid solution is further added to the lean organic phase prepared in the above step, and the lean organic phase and the hydrochloric acid solution are all returned for use as an extractant, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution is 10:1.

[0060] Example 3

[0061] The monazite alkali cake has a moisture content of 33.18%. By mass percentage, the uranium content is 0.42%, the rare earth oxide content is 59.48%, and the thorium content is 6.35%.

[0062] Step 1: Add water in a mass ratio of 2:1 to make a slurry, mix the solid and liquid evenly, then add concentrated hydrochloric acid to dissolve, control the residual acid to be less than 0.5 mol / L, stir and react for 6 hours to obtain the leaching slurry. The mass volume ratio of alkali cake (dry basis): industrial concentrated hydrochloric acid is about 1t:1.2m 3 .

[0063] Step 2: Add 20% polyethylene glycol to the leached slurry at a dosage of 1 kg / m 3 After filtration, an alkaline cake leachate was obtained, wherein the iron content in the alkaline cake leachate was 0.99 g / L, the uranium content was 1.31 g / L, the rare earth oxide concentration was 263.92 g / L, and the residual acid was 0.49 mol / L.

[0064] In step 3, the leachate is extracted and stripped using a mixer-settler, and a three-stage countercurrent extraction is performed using 15% N235 + 15% tributyl phosphate + 70% sulfonated kerosene (volume ratio) as an extractant. The oil-water flow rate ratio is 1:2, and an extract and a raffinate loaded with an organic phase are obtained. The uranium content in the raffinate is 0.026 g / L, the iron content is 0.024 g / L, and the uranium content in the loaded organic phase is 3.03 g / L.

[0065] In step 4, the organic phase-loaded extract was subjected to 11-stage countercurrent stripping using 0.001 mol / L hydrochloric acid solution as a stripping agent, with an oil-water flow rate ratio of 4:1. The uranium content in the stripping solution was 12.11 g / L, the iron content was 9.41 g / L, and the uranium recovery rate was 98.02%.

[0066] Step 5: The stripping solution is subjected to a step-by-step precipitation method to remove iron, and the pH is adjusted to 2.7 using 30% by mass of sodium hydroxide, and the iron hydroxide impurities are removed by filtration.

[0067] In step 6, the filtrate is precipitated with sodium diuranate using solid sodium hydroxide, with the endpoint pH controlled at 7.1. The mixture is stirred for 8 hours and then filtered to obtain a sodium diuranate product having a dry basis uranium content of 61.68%, an iron content of 0.21%, a rare earth oxide content of 0.15%, and a thorium content of 0.35%, meeting the technical requirements of the diuranate industry standard (EJ / T 803-1993).

[0068] Step 7: The uranium raffinate and the leaching residue are mixed to prepare a slurry, which is heated to 80° C. and adjusted to a pH of 3-4 using an alkaline slurry. The filtrate is kept warm for 4 hours and then filtered. The filtrate is a high-chloride rare earth solution, which is then removed from impurities, concentrated, and crystallized to obtain a chloride rare earth product.

[0069] 2.5 mol / s hydrochloric acid solution is further added to the lean organic phase prepared in the above step, and the lean organic phase and the hydrochloric acid solution are all returned for use as an extractant, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution is 10:1.

[0070] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or system comprising the element.

[0071] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0072] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for extracting uranium from monazite alkali cake, characterized in that: The method comprises the following steps: Step 1: stir monazite alkali cake with a preset amount of water to obtain a mixed slurry 1, then add a preset volume of concentrated hydrochloric acid to the mixed slurry 1, stir and react for a preset time to obtain a leaching slurry, wherein the mass volume ratio of monazite alkali cake to concentrated hydrochloric acid is 1t: (1~1.5)m 3 , the residual acid H in the leaching pulp + The concentration is 0.3~0.8mol / L; Step 2: adding a polyethylene glycol aqueous solution to the leached slurry to remove silicon by flocculation, and filtering to obtain an alkaline cake leachate and a filter cake; Step 3, adding trioctyldecyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant to the alkali cake leachate for extraction treatment to co-extract uranium and iron, thereby obtaining an organic phase-loaded extract and a raffinate, wherein the volume ratio of trioctyldecyl tertiary amine to tributyl phosphate is 1:1, the trioctyldecyl tertiary amine accounts for 10-20% of the total volume of the mixed extractant, and the flow rate ratio of the alkali cake leachate to the mixed extractant is (1.5-2):1; Step 4, adding a stripping agent to the organic phase-loaded extract to perform stripping treatment to obtain a stripping solution and a lean organic phase, wherein the stripping agent is an aqueous liquid, and the flow rate ratio of the extract to the stripping agent is 4:1; Step 5, adding sodium hydroxide solution to the stripping solution to control the pH value of the stripping solution to 2.5-3, and filtering to obtain ferric hydroxide and a filtrate; Step 6: adding solid sodium hydroxide to the filtrate to control the pH value of the filtrate to 7-8 by dissolving the solid sodium hydroxide, and filtering to obtain sodium diuranate precipitate.

2. The method for extracting uranium from monazite alkali cake according to claim 1, wherein The method further comprises the following steps: The filter cake in step 2 is mixed with the raffinate in step 3, and heated to 80°C. Alkali slurry is then added to adjust the pH to 3-4. After keeping warm for 4 hours, the mixture is filtered to obtain the filtrate, which is the high-chloride rare earth solution. The alkaline slurry is the slurry obtained by adding water to the alkali cake.

3. The method for extracting uranium from monazite alkali cake according to claim 1, wherein In step 1, the residual acid H in the slurry is leached + The concentration is 0.4~0.5mol / L.

4. The method for extracting uranium from monazite alkali cake according to claim 1, wherein In step 1, the mass ratio of monazite alkali cake to water is 2:

1.

5. The method for extracting uranium from monazite alkali cake according to claim 1, wherein In step 2, the volume mass ratio of the leached slurry to the polyethylene glycol solid is 1m 3 : (2.5-10) kg, the mass fraction of polyethylene glycol in the polyethylene glycol aqueous solution is 20%.

6. The method for extracting uranium from monazite alkali cake according to claim 1, wherein In step 4, the stripping agent is water or 0.001-0.1 mol / L hydrochloric acid solution.

7. The method for extracting uranium from monazite alkali cake according to claim 1, wherein In step 1, the stirring reaction is preset for 4 to 12 hours.

8. The method for extracting uranium from monazite alkali cake according to any one of claims 1 to 7, characterized in that: The method further comprises the following steps: A 2.5 mol / L hydrochloric acid solution was added to the lean organic phase, and the lean organic phase and the hydrochloric acid solution were all returned to step 3, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution was 10:

1.

9. The method for extracting uranium from monazite alkali cake according to claim 8, wherein: In step 3, a three-stage countercurrent extraction operation is adopted in the extraction process.

10. The method for extracting uranium from monazite alkali cake according to claim 8, wherein: In step 4, 8 to 11 stages of countercurrent stripping are used in the stripping treatment.

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