Method for extracting uranium from monazite alkali cake

Abstract

The invention discloses a method for extracting uranium from a monazite alkali cake, which comprises the following steps: stirring the monazite alkali cake and water to prepare slurry to obtain mixed slurry 1, then adding concentrated hydrochloric acid into the mixed slurry 1, and stirring to react to obtain leached ore pulp; adding a polyethylene glycol aqueous solution into the leached ore pulp to flocculate and remove silicon, and filtering to obtain alkali cake leach liquor and a filter cake; adding a mixed extracting agent of tri-n-decyl alkyl tertiary amine, tributyl phosphate and sulfonated kerosene into the alkali cake lixivium for extraction treatment to co-extract uranium and iron to obtain an organic phase-loaded extract and raffinate; adding a stripping agent into the organic-phase-loaded extraction liquid to carry out stripping treatment, so as to obtain stripping liquid and a poor organic phase; adding a sodium hydroxide solution into the strip liquor to control the pH value of the strip liquor to 2.5-3, and filtering to obtain ferric hydroxide and filtrate; and adding sodium hydroxide solid into the filtrate, and filtering to obtain sodium diuranate precipitate. The invention aims to improve the uranium extraction rate in 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 cakes. 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. Most of the companies engaged in monazite smelting and production adopt caustic soda leaching process. The produced alkali cake enters the later hydrochloric acid dissolution process to produce rare earth chloride. The dissolution slag produced in this process can be used for uranium recovery treatment.

[0003] The invention patent with the existing patent publication number CN116574928A discloses a method for recovering uranium from monazite slag, which comprises the following steps: using hydrochloric acid A to acid-leach the monazite slag to obtain a leached pulp; the concentration of the hydrochloric acid A is 4-10 mol / L; the leached pulp is solid-liquid separated to obtain a leaching solution; the leaching solution is mixed with an extractant A to extract and remove iron to obtain an iron-loaded organic phase and an iron raffinate; the extractant A comprises 4-10% of an amine extractant and 5% of a fatty alcohol extractant in terms of volume percentage. ~20% 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 and the extractant B are mixed to extract uranium to obtain a uranium-loaded organic phase and a uranium raffinate; in terms of volume percentage, the extractant B includes 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 uranium qualified solution. The above-mentioned process of using hydrochloric acid to dissolve the slag and extracting and recovering uranium with the clear liquid after filtration has the following difficulties: ① The silicon content in the clear liquid of the complete dissolution filtration is about 3g / L, and a third phase flocculent layer is formed with the organic phase during the stripping process. The third phase material accumulated over a long period of operation seriously affects the operation stability of the extraction phase. ② The acid solution of the whole slag is to ensure the fluidity of the slurry and the filtration clear liquid with high chloride ion concentration, so that the residual acid of the whole solution of the slag reaches more than 2.5 mol / L. The hydrochloric acid mist seriously corrodes the equipment, and the filtration of the whole slag is also difficult, resulting in low uranium extraction efficiency. ③ The raffinate needs to be returned to the leaching process of the slag. During the continuous cycle of the process, a small amount of elements such as titanium, silicon, and zirconium in the solution are gradually enriched in the leaching solution, further affecting the stability of the extraction and stripping system. Therefore, it is urgent to propose a new uranium extraction method to solve the above problems. Summary of the invention

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

[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, mixing monazite alkali cake with a preset amount of water to obtain a mixed slurry 1, then adding a preset volume of concentrated hydrochloric acid to the mixed slurry 1, stirring and reacting for a preset time to obtain a leached slurry, wherein the mass volume ratio of monazite alkali cake to concentrated hydrochloric acid is 1t: (1-1.5)m 3 , leaching the residual acid H in the slurry + The concentration is 0.3-0.8 mol / L;

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

[0008] Step 3, adding trioctyldecyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant to the alkali cake leachate for extraction treatment, so as to extract uranium and iron together, and obtain an extract and a raffinate loaded with an organic phase, 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 iron 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, and then alkali slurry is added to adjust the pH to 3-4. After keeping warm for 4 hours, the filtrate is filtered to obtain a high-chloride rare earth liquid, wherein the alkali slurry is a 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 1 m 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 / s hydrochloric acid solution is added to the lean organic phase, and the lean organic phase and the hydrochloric acid solution are all returned to step 3, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution is 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 alkaline cake slurry and concentrated hydrochloric acid to react and leach, and controls the residual acid solubility to obtain a leached ore pulp, and then continues to use polyethylene glycol solution to flocculate and remove silicon, and then the filtered alkaline cake leachate is first extracted by a mixed extractant of trioctyl decyl tertiary amine, tributyl phosphate and sulfonated kerosene, so that uranium and iron are co-extracted to obtain an extract loaded with an organic phase, and the extract is further subjected to a stripping operation through an aqueous liquid to obtain a stripping solution, and the stripping solution 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 earths by one 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 excellent dissolution and rare earth recovery process with the residual, and finally go to the excellent dissolution slag or the rare earth removal slag. The uranium extraction method is simple, convenient and easy to operate, and can be easily promoted and used in industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It 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 realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

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

[0029] See also Figure 1-2 The present invention provides a schematic flow diagram 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 above-mentioned 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 leached 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, adding polyethylene glycol solution to the leached slurry, stirring for 10 to 30 minutes to remove silicon by flocculation, and filtering to obtain alkaline cake leaching solution 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 to 20%, preferably 5 to 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, and its filtration effect is better than that of ordinary filtration devices.

[0032] Step 3, adding trioctyl decyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant to the alkali cake leachate for extraction treatment, so as to extract uranium and iron together, and obtain an extract and a raffinate loaded with an organic phase, wherein the volume ratio of trioctyl decyl tertiary amine to tributyl phosphate is 1:1, the trioctyl decyl 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 adopted in the extraction treatment. This extraction step adopts an alkyl tertiary amine extraction method, so that the UO2Cl4 formed in the alkali cake leachate is extracted in a high chloride ion system. 2- ions and exchange with the extracted ions.

[0033] 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. 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, wherein 8-11 levels of countercurrent stripping operations are adopted in the stripping treatment, and a 2.5 mol / L hydrochloric acid solution can be added to the lean organic phase, and after mixing, it 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] Step 5, adding sodium hydroxide solution to the stripping solution to control the pH value of the stripping solution to 2.5-3, filtering to obtain iron hydroxide and 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, 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. Preferably, the pH value of the filtrate is controlled to be 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 heated to 80°C. The pH value is adjusted to 3-4 using alkali slurry. After keeping warm for 4 hours, the filtrate is filtered to obtain a high-chloride rare earth liquid. The rare earth chloride product is obtained after impurities are removed, concentrated and crystallized. The alkali slurry is a slurry obtained by adding water to the alkali cake.

[0038] The present invention uses alkali cake slurry and concentrated hydrochloric acid to react and leach, and controls the residual acid solubility to obtain a leached ore pulp, and continues to use polyethylene glycol solution to remove silicon by flocculation, and then the filtered alkali cake leachate is first extracted by a mixed extractant of trioctyl decyl tertiary amine, tributyl phosphate and sulfonated kerosene, so that uranium and iron are co-extracted to obtain an extract loaded with an organic phase, and the extract is continued to be stripped by a water-containing liquid to obtain a stripping solution, and the stripping solution 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 earths by one 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 excellent dissolution recovery rare earth process with the residual, and finally go to the excellent dissolution slag or the rare earth removal slag.

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

[0040] Example 1

[0041] The water content of monazite alkali cake is 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 at 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 leached 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 leaching solution was obtained, wherein the iron content in the alkaline cake leaching solution 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] Step 3, the leaching solution is extracted and stripped using a mixing settler, and the extractant is 15% trioctyldecyl tertiary amine N235+15% tributyl phosphate+70% sulfonated kerosene (volume ratio) for three-stage countercurrent extraction, and the oil-water flow rate ratio is 1:1.5, to obtain an extract and a raffinate loaded with an organic phase, wherein the uranium content in the raffinate is 0.025 g / L, the iron content is 0.016 g / L, and the uranium content in the extract loaded with the organic phase is 1.83 g / L.

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

[0046] Step 5, the stripping solution is de-ironized by a step-by-step precipitation method, 30% by mass of sodium hydroxide is used to adjust the pH to 2.5, and the iron hydroxide impurities are removed by filtration.

[0047] Step 6, using solid sodium hydroxide to precipitate sodium diuranate in the filtrate, controlling the end point pH to 7.3, stirring for 8 hours and then filtering to obtain a sodium diuranate product, the product has a dry basis uranium content of 61.92%, an iron content of 0.18%, a rare earth oxide of 0.83%, and a thorium content of 0.57%, which meets the technical index requirements of the diuranate industry standard (EJ / T 803-1993).

[0048] Step 7, the uranium raffinate and the leaching residue are mixed to make pulp, the temperature is raised to 80° C., the pH value is adjusted to 3-4 using alkaline pulp, and the mixture is filtered after being kept warm for 4 hours. The filtrate is the high-chloride rare earth liquid, and the rare earth chloride product is obtained after impurity removal, concentration and crystallization.

[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 water content of monazite alkali cake is 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 at 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 leached 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 leaching solution was obtained, wherein the iron content in the alkaline cake leaching solution 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] Step 3, the leaching solution is extracted and stripped using a mixing settler, and the extractant is 15% N235+15% tributyl phosphate+70% sulfonated kerosene (volume ratio) for three-stage countercurrent extraction, and the oil-water flow rate ratio is 1:2 to obtain an extract and a raffinate loaded with an organic phase, wherein the uranium content in the raffinate is 0.027 g / L, the iron content is 0.019 g / L, and the uranium content in the loaded organic phase is 2.87 g / L.

[0055] Step 4, the extract loaded with the organic phase is 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 is 11.45 g / L, the iron content is 7.81 g / L, and the uranium recovery rate is 97.79%.

[0056] Step 5, the stripping solution is de-ironized by a step-by-step precipitation method, 30% by mass of sodium hydroxide is used to adjust the pH to 2.9, and the iron hydroxide impurities are removed by filtration.

[0057] Step 6, using solid sodium hydroxide to precipitate sodium diuranate in the filtrate, controlling the end point pH to 7.1, stirring for 8 hours and then filtering 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 of 0.97%, and a thorium content of 0.53%, which meets the technical index requirements of the diuranate industry standard (EJ / T 803-1993).

[0058] Step 7, the uranium raffinate and the leaching residue are mixed to make pulp, the temperature is raised to 80° C., the pH value is adjusted to 3-4 using alkaline pulp, and the mixture is filtered after being kept warm for 4 hours. The filtrate is the high-chloride rare earth liquid, and the rare earth chloride product is obtained after impurity removal, concentration and crystallization.

[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 water content of monazite alkali cake is 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 at 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 leached 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 leaching solution was obtained, wherein the iron content in the alkaline cake leaching solution 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] Step 3, the leaching solution is extracted and stripped using a mixing settler, and the extractant is 15% N235+15% tributyl phosphate+70% sulfonated kerosene (volume ratio) for three-stage countercurrent extraction, and the oil-water flow rate ratio is 1:2 to obtain an extract and a raffinate loaded with an organic phase, wherein 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] Step 4, the extract loaded with the organic phase is 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 is 12.11 g / L, the iron content is 9.41 g / L, and the uranium recovery rate is 98.02%.

[0066] Step 5, the stripping solution is de-ironized by a step-by-step precipitation method, 30% by mass of sodium hydroxide is used to adjust the pH to 2.7, and the iron hydroxide impurities are removed by filtration.

[0067] Step 6, using solid sodium hydroxide to precipitate sodium diuranate in the filtrate, controlling the end point pH to 7.1, stirring for 8 hours and then filtering to obtain a sodium diuranate product, the product has a dry basis uranium content of 61.68%, an iron content of 0.21%, a rare earth oxide of 0.15%, and a thorium content of 0.35%, which meets the technical index requirements of the diuranate industry standard (EJ / T 803-1993).

[0068] Step 7, the uranium raffinate and the leaching residue are mixed to make pulp, the temperature is raised to 80° C., the pH value is adjusted to 3-4 using alkaline pulp, and the mixture is filtered after being kept warm for 4 hours. The filtrate is the high-chloride rare earth liquid, and the rare earth chloride product is obtained after impurity removal, concentration and crystallization.

[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 article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0071] The serial numbers of the above embodiments of the present invention are only for description 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 specification 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, mixing monazite alkali cake with a preset amount of water to obtain a mixed slurry 1, then adding a preset volume of concentrated hydrochloric acid to the mixed slurry 1, stirring and reacting for a preset time to obtain a leached slurry, wherein the mass volume ratio of monazite alkali cake to concentrated hydrochloric acid is 1t: (1-1.5)m 3 , leaching the residual acid H in the slurry + The concentration is 0.3-0.8 mol / L; Step 2, adding polyethylene glycol aqueous solution to the leached slurry to remove silicon by flocculation, and obtaining an alkaline cake leachate and a filter cake after filtering; Step 3, adding trioctyldecyl tertiary amine, tributyl phosphate and sulfonated kerosene mixed extractant to the alkali cake leachate for extraction treatment, so as to extract uranium and iron together, and obtain an extract and a raffinate loaded with an organic phase, 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 iron 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, characterized in that: 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, and then alkali slurry is added to adjust the pH to 3-4. After keeping warm for 4 hours, the filtrate is filtered to obtain a high-chloride rare earth liquid, wherein the alkali slurry is a slurry obtained by adding water to the alkali cake.

3. The method for extracting uranium from monazite alkali cake according to claim 1, characterized in that: 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, characterized in that: 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, characterized in that: 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%.

6. The method for extracting uranium from monazite alkali cake according to claim 1, characterized in that: 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, characterized in that: 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 / s hydrochloric acid solution is added to the lean organic phase, and the lean organic phase and the hydrochloric acid solution are all returned to step 3, wherein the volume ratio of the lean organic phase to the added hydrochloric acid solution is 10:

1.

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

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

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