CN114164351B - Method for preparing thorium nitrate by using monazite optimum-solubility slag - Google Patents
Method for preparing thorium nitrate by using monazite optimum-solubility slag Download PDFInfo
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- C—CHEMISTRY; METALLURGY
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- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
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- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
- C22B3/06—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic acid solutions, e.g. with acids generated in situ; in inorganic salt solutions other than ammonium salt solutions
- C22B3/065—Nitric acids or salts thereof
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- C22B60/026—Obtaining thorium, uranium, or other actinides obtaining uranium by wet processes treatment or purification of solutions or of liquors or of slurries liquid-liquid extraction with or without dissolution in organic solvents
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Abstract
The invention discloses a method for preparing thorium nitrate by utilizing monazite optimum-solubility slag, which comprises the following steps: (1) slurry pretreatment: mixing the monazite dissolved slag into slurry, adding nitric acid, heating and stirring to obtain a feed liquid A; (2) titanium removal treatment: carrying out titanium removal treatment on the feed liquid A, and filtering to obtain filtrate B; (3) extracting uranium: extracting the filtrate B to obtain a uranium-containing organic phase, heating and back-extracting the uranium-containing organic phase by using a nitric acid solution, and precipitating to obtain raffinate C; (4) extracting thorium: extracting the raffinate C to obtain a thorium-containing organic phase and a raffinate D, and heating and back-extracting the thorium-containing organic phase by using a nitric acid solution to obtain a thorium back-extraction solution E; (5) thorium nitrate crystallization: and (3) concentrating the thorium strip liquor E, carrying out uranium extraction operation on the obtained concentrated solution in the step (3), obtaining raffinate F, carrying out crystallization treatment, and carrying out solid-liquid separation to obtain high-purity thorium nitrate. The invention aims to improve the extraction efficiency of monazite preferential dissolution slag.
Description
Technical Field
The invention relates to the technical field of chemical smelting, in particular to a method for preparing thorium nitrate by utilizing monazite optimal-solubility slag.
Background
Monazite is an important phosphate rare earth ore, and is often associated with more radioactive elements such as thorium and uranium and a small amount of minerals such as rutile, ilmenite, zirconite, quartz and the like. The decomposition method commonly used in industry mainly comprises sulfuric acid, soda roasting method and sodium hydroxide soda boiling decomposition method, and the most widely used method at present is sodium hydroxide soda boiling decomposition method. The monazite concentrate is heated to 130-160 ℃ in a solution of sodium hydroxide to carry out solid-liquid multiphase reaction, and the decomposition degree of rare earth, thorium and uranium is influenced by various factors. After decomposing and washing the alkali-soluble substance, an alkali cake consisting of hydroxide precipitates of rare earth, thorium and most uranium and undecomposed minerals is obtained. When the alkali cake is dissolved by hydrochloric acid, in order to improve the purity of the rare earth chloride solution, the washed hydroxide alkali cake or rare earth carbonate is often used industrially, the pH value of the acid leaching solution is reversely adjusted from 1-2 to about 4.5, thorium, iron and part of uranium are precipitated and enter precipitation slag together with acid insoluble substances, and monazite-quality dissolving slag is obtained.
The prior invention patent CN104775026 discloses a method for extracting high-purity uranium, thorium and mixed rare earth from superior slag, which comprises the following steps: dissolving the fine slag by using hydrochloric acid, filtering, entering a P350-kerosene cascade extraction system for multistage fractional extraction, carrying out thorium/rare earth separation on raffinate in a load phase by using the P350-kerosene cascade extraction system, carrying out thorium in the load phase, heating water by the raffinate to remove titanium, and precipitating to obtain the mixed rare earth. But the RE/Th separation coefficient is smaller under the condition of low acidity, and the purity of thorium is lower; titanium is easy to hydrolyze, so that the titanium is hydrolyzed in the extraction process to cause emulsification, and the thorium/rare earth extraction process is influenced.
Disclosure of Invention
The invention mainly aims to provide a method for preparing thorium nitrate by using monazite optimum soluble slag, and aims to solve the technical problem that thorium cannot be extracted by adopting TBP (tert-butyl-phosphate) extraction in a large amount of chloride ions in the existing monazite optimum soluble slag.
In order to achieve the aim, the invention provides a method for preparing thorium nitrate by using monazite optimum slag, which comprises the following steps:
(1) Slurry pretreatment: mixing the monazite dissolved slag, adding nitric acid, heating and stirring, controlling the concentration of residual acid and obtaining a feed liquid A;
(2) Titanium removal treatment: carrying out titanium and zirconium removal treatment on the feed liquid A, and filtering to obtain filtrate B;
(3) And (3) extracting uranium: extracting the filtrate B by using a mixed solution of 5-7% of tributyl phosphate and sulfonated kerosene as an extracting agent to obtain a uranium-containing organic phase, heating and back-extracting the uranium-containing organic phase by using a nitric acid solution, and precipitating to obtain a corresponding raffinate C;
(4) Extracting thorium: extracting the raffinate C by using a mixed solution of 38-42% of tributyl phosphate and sulfonated kerosene as an extracting agent to obtain a thorium-containing organic phase and a raffinate D, and heating and back-extracting the thorium-containing organic phase by using a nitric acid solution to obtain a thorium back-extraction solution E;
(5) Thorium nitrate crystallization: and (3) concentrating the thorium strip liquor E, carrying out uranium extraction operation on the obtained concentrated solution in the step (3), obtaining raffinate F, carrying out crystallization treatment, and carrying out solid-liquid separation to obtain high-purity thorium nitrate.
Further, the method further comprises the steps of:
(6) And (3) recovering rare earth: stirring the raffinate D, slowly adding hydrogen peroxide and caustic soda flakes to adjust the pH value to 3.5-4.5, filtering to obtain a filtrate G, adding a sodium carbonate solution into the filtrate G to adjust the pH value to 6.4-6.8, aging and filtering to obtain the rare earth carbonate.
Further, after the step (5), the method further comprises: and (4) performing thorium extraction operation on the mother liquor obtained after solid-liquid separation in the step (5).
Further, the step (1) specifically comprises the steps of adding more than 50% of nitric acid after size mixing of monazite dissolved slag, stirring and heating, and controlling the concentration of residual acid to be 2.5-4 mol/L.
Further, the step (2) further comprises: and when the temperature of the feed liquid A is reduced to below 60 ℃, adding hydrogen peroxide and polyether, uniformly stirring, and then performing filter pressing by using a box type or plate type filter press to obtain a filtrate B.
Further, in the step (3), 1-2% nitric acid solution is adopted to be heated to 40-55 ℃ for extraction, and then sodium hydroxide is adopted for precipitation, so that sodium diuranate is obtained.
Further, in the step (4), a 0.5-1.5% dilute nitric acid solution is heated to 45-65 ℃ for back extraction, so as to obtain thorium back extraction solution E.
Further, the concentration process in the step (5) specifically includes: and adding the thorium stripping solution E into a concentration reaction kettle, and stopping heating and cooling when the thorium oxide concentration is 300-500 g/L.
Further, the extraction tank is made of PP or PPH materials.
Further, the acid insoluble slag obtained after dissolving the nitric acid in the step (1) is recovered by gravity separation and/or magnetic separation.
According to the method for preparing thorium nitrate by using monazite excellent dissolving slag, disclosed by the embodiment of the invention, the technical problem that thorium cannot be extracted by adopting TBP due to a large amount of chloride ions in the monazite excellent dissolving slag is solved by optimizing the extraction process through the modes of dissolving the monazite excellent dissolving slag by nitric acid, extracting uranium by using low-concentration tributyl phosphate (TBP), extracting thorium by using high-concentration TBP, deeply removing uranium by using low-concentration TBP and crystallizing the thorium nitrate, and the problem of reduction of extraction efficiency caused by mutual confusion of extracting agents due to different extracting agent systems is solved by avoiding adopting a single TBP extraction system.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not delimit the invention.
The invention provides a method for preparing thorium nitrate by using monazite optimum slag, which comprises the following steps:
(1) Slurry pretreatment: adding water into monazite optimal-dissolution slag for size mixing, and according to the slag: nitric acid (in terms of 98% nitric acid) =1: adding nitric acid with the concentration of more than 50% according to the proportion of 0.45-0.6, controlling the liquid-solid ratio range to be 1.2-2, heating to be more than 95 ℃, boiling at the highest temperature, stirring and preserving heat for 1-2 h, then adding normal-temperature water until the liquid-solid ratio is about 1.5-2.5, and controlling the concentration range of the residual acid to be 2.5-4 mol/L to obtain the feed liquid A. The main principle of dissolution of the monazite preferential dissolution slag in nitric acid is as follows:
RE(OH) 3 +3HNO 3 →RE(NO 3 ) 3 +3H 2 O
Th(OH) 4 +3HNO 3 →Th(NO 3 ) 4 +4H 2 O
Na 2 U 2 O 7 +6HNO 3 →2UO 2 (NO 3 ) 2 +2NaNO 3 +3H 2 O
in addition, aiming at the acid-insoluble slag obtained after the nitric acid is dissolved in the step (1), which is mainly undecomposed ore, monazite, xenotime, cobalt cristobalite and the like in the acid-insoluble slag are recovered by combining mineral separation modes such as gravity separation, magnetic separation and the like, and the monazite and the xenotime are returned to the alkali roasting decomposition stage.
(2) Titanium removal treatment: when the temperature of the feed liquid A is reduced to below 60 ℃, 25L/m of hydrogen peroxide is used 3 0.1-0.5L/m of polyether 3 Adding hydrogen peroxide and polyether into thiourea, stirring, press-filtering with a box-type or plate-type filter press to separate solid from liquid, aging for 12 hr or more, fine filtering to remove fine particles, and clarifying to obtain filtrate B. In the step, the pH value is adjusted by adding hydrogen peroxide, so that impurities such as titanium, zirconium and the like are effectively removed, emulsification caused by hydrolysis of titanium and zirconium in the subsequent extraction process is avoided, and the obtained filtrate B has good filtering performance.
(3) And (3) extracting uranium: and (3) extracting uranium, iron and partial chloride ions from the filtrate B by using a mixed solution of 5-7% tributyl phosphate (TBP) and sulfonated kerosene as an extracting agent, and then performing washing, uranium back-extraction and organic phase acidification treatment.
Specifically, the extraction method preferably adopts cascade extraction, and also can adopt intermittent single-stage extraction, and the extraction stage number is controlled as follows:extracting uranium by 8-12 grade countercurrent, washing iron and thorium by 6-10 grade countercurrent, anti-uranium by 4-8 grade countercurrent, acidifying by 2-4 grade, and 40g/L chloride ion, chloride ion and Fe contained in filtrate B 3+ Formation of FeCl 4 - Extracting by TBP; the uranium-thorium separation coefficient is small, and a small amount of uranium is left in raffinate in the uranium extraction process so as to ensure the purity of the extracted uranium; and wherein the extraction flow ratio is the organic extractant: feed liquid: washing solution: anti-uranium solution: acidified solution =1 to 1.5: 0.15 to 0.25:0.3 to 0.45:0.2 to 0.3;
specifically, the washing treatment: in the uranium extraction, feed liquid B is added from 8 stages, and raffinate at the outlet of the 1 st stage contains 0.08g/L of uranium, 69.47g/L of thorium, 42.56g/L of REO and 3.52mol/L of nitrate radical; using EC 17.2us/cm deionized water as a washing solution, washing, then, containing 5.51g/L thorium and 0.51g/L Fe, returning to the nitric acid dissolution in the step (1), and returning washing water to the step (1) for monazite superior dissolved slag size mixing;
and (3) uranium back extraction treatment: 1 to 2% of HNO 3 Heating the solution to 40-55 ℃ for back extraction, precipitating the back extraction solution containing uranium by using sodium hydroxide to obtain sodium diuranate and obtain corresponding raffinate C, wherein the raffinate C contains thorium, rare earth and a small amount of uranium;
acidification of the organic phase: using 4-5 mol/L HNO 3 And (3) acidifying the organic phase, wherein the acidizing fluid can be recycled, and when the pH value is more than or equal to 1, the acidizing fluid is replaced, and the replaced solution returns to the step (1) for dissolution.
(4) Extracting thorium: the mixed solution of TBP and sulfonated kerosene accounting for 38-42 percent is used as an extracting agent, the extraction flow ratio is determined according to the concentration of thorium in raffinate C, the extraction mode preferably adopts cascade extraction, also can adopt batch type single-stage extraction, and the extraction stage number is controlled as follows: 12-15 levels of countercurrent extraction, 5-7 levels of countercurrent acid washing, 7-9 levels of countercurrent water washing for washing chloride ions, and 6-8 levels of countercurrent back extraction;
specifically, extraction treatment: extracting the raffinate C to obtain a thorium-containing organic phase and a raffinate D, wherein thorium and a small amount of uranium enter the loaded organic phase, and rare earth enters the raffinate D;
acid washing: generally, 3 to 5mol/L of HNO is selected 3 Washing the loaded organic phase as a washing acidPreferably 4mol/L HNO is used 3 Acid washing two-phase contact flow ratio O: a =3.5 to 5:1, preferably 4;
water washing: washing with deionized water (EC less than 20 us/cm), and washing with water according to the contact flow ratio of two phases: o: a =8 to 10:1, preferably O: a =8:1;
back extraction: adding analytically pure nitric acid into deionized water (EC less than 20 us/cm) to prepare 0.5-1.5% dilute nitric acid, preferably 1% dilute nitric acid, heating to 45-65 ℃, preferably 50 ℃, and controlling the back-extraction two-phase contact phase ratio O: a =1, preferably O: a =1:1; obtaining thorium back extraction liquid E.
(5) Thorium nitrate crystallization: and (3) adding the thorium strip liquor E into a concentration reaction kettle for concentration, carrying out uranium extraction operation on the obtained concentrated solution in the step (3), obtaining raffinate F, adding the raffinate F into a concentration crystallization kettle (pot) for concentration, evaporation and crystallization, and continuously carrying out solid-liquid separation to obtain high-purity thorium nitrate.
Specifically, the concentration condition is that the concentration evaporation vacuum degree is controlled to be 6 x 10 -4 Pa, the evaporation temperature is 75-115 ℃, the steam pressure is 0.3-0.4 MPa, when the density of the concentrated solution reaches 50-65 Be and the thorium content is 300-500 g/L, the heating is stopped, and the concentrated solution is obtained after cooling;
deep extraction uranium removal: and (3) performing single-stage extraction on the obtained concentrated solution for 2-3 times, preferably 2 times, controlling the phase ratio of two phases to be O = 3-4, returning the loaded organic phase to the uranium extraction in the step (3), and obtaining raffinate F, wherein the extraction treatment realizes the return and centralized treatment of uranium, and the reaction formula of uranium removal reaction is as follows:
UO 2 2+ +2NO 3 - +TBP→UO 2 (NO 3 ) 2 .TBP；
thorium nitrate crystallization: adding the raffinate F into a concentration crystallization kettle (pot) for concentration, evaporation and crystallization, wherein a water jet vacuum pump is generally adopted, the concentration and evaporation vacuum degree is-0.06 to-0.08 MPa, the evaporation temperature is 75 to 115 ℃, and the steam pressure is as follows: 0.3-0.4 MPa, using a baume meter to measure the baume degree of the concentrated solution, stopping heating when the concentrated solution reaches 70-75 Be, naturally cooling and crystallizing the concentrated solution, and being beneficial to being mixed with chloride ionsIron, uranium and rare earth are well separated; cooling to room temperature for a certain time, preferably cooling for 24 hours, heating the material in a centrifuge for solid-liquid separation, wherein the rotation speed of the centrifuge is preferably more than or equal to 1500r/min, returning the obtained mother liquor to the step (4) for thorium extraction again, wherein the mother liquor is generally 300-500L/t (relative to thorium nitrate), wherein ThO 2 About 500g/L, nitric acid concentration of about 4mol/L, where a 99.99% thorium nitrate product (Th (NO) 3 ) 4 ·6H 2 O), and ThO) 2 ≥45％，Fe≤10ppm，TREO≤20ppm， Cl≤10ppm，Ca≤10ppm、Ti≤5ppm。
(6) And (3) recovering rare earth: stirring the raffinate D and slowly adding hydrogen peroxide, wherein the acidity of the raffinate D is 1.5-2 mol/L, the raffinate D contains rare earth and is 5-10L/m 3 Adding hydrogen peroxide as reducing agent to reduce Ce 4+ To Ce 3+ (ii) a And adding hydrogen hydroxide as a neutralizing agent, adjusting the pH value to 3.5-4.5, filtering by using a filter press to obtain a filtrate G, adding a sodium carbonate solution into the filtrate G, adjusting the pH value to 6.4-6.8, aging and filtering to obtain the rare earth carbonate.
2RE 3+ +3Na 2 CO 3 →RE 2 (CO 3 ) 3 ↓+6Na + ；
Specific examples are as follows:
1. the raw material components are as follows: typical values of main components of monazite dissolving slag are as follows: the moisture content in wet basis analysis was 40%, and the main chemical composition thereof is shown in Table 1.
TABLE 1 main chemical composition of monazite slag
Example 1
(1) Pretreatment and titanium removal treatment: taking 3000Kg of monazite dissolved slag of the above components and pouring into 10m 3 In a stirred PPH tank and mixed as described by S: L =1: adding 3000L of water into 1, adding 1050L of 98% fuming nitric acid under stirring, heating to boil, stirring and keeping the temperature for 1h. After heat preservation for 1 hourL =1, the residual acid concentration was measured to be 3.27mol/L; cooling to solution temperature of 60 deg.C, adding 50L hydrogen peroxide and 0.4L polyether, stirring, press filtering with 100m2 membrane filter press, aging for 12 hr, filtering with 5 μm precision filter to obtain clear solution B-5.19m 3 . NO in feed liquid 3 - 3.91mol/L、 REO 43.10g/L、ThO 2 70.82g/L、U 3 0 8 3.02g/L、Fe 5.06g/L、TiO 2 6.11g/L、ZrO 2 0.11g/L、Cl - 40.31g/L, the direct yield of thorium is 88.27%, the direct yield of rare earth is 78.09%, and the direct yield of uranium is 94.98%. Dissolving a plurality of batches of fine slag, and reserving enough feed liquid for extraction to keep the relative consistency of the extract liquid.
(2) And (3) extracting uranium: preparing a cascade extraction tank containing 5% of TBP + sulfonated kerosene, controlling the number of stages to 8 stages of countercurrent extraction U,6 stages of countercurrent washing of iron and thorium, 4 stages of countercurrent anti-uranium, 2 stages of acidification, and controlling the flow ratio to be organic: feed liquid: washing solution: anti-uranium solution: acidified solution =1.2: 0.15:0.3:0.2, adding the feed liquid A from the 8-stage, wherein the raffinate at the outlet of the 1-stage contains 0.08g/L of uranium, 69.47g/L of thorium, 42.56g/L of REO and 3.52mol/L of nitrate radical; using EC 17.2us/cm deionized water as the washing solution (thorium content 5.51g/L, fe content 0.51g/L after washing, returning to the previous nitric acid dissolution), 1% HNO at 50 ℃ 3 The solution is used as an anti-uranium solution, and the anti-extraction solution contains 9.05g/L uranium. Returning the uranium return liquid to the monazite ore alkali boiling uranium extraction process flow, and precipitating with sodium hydroxide to obtain sodium diuranate; 4mol/L HNO is used for a blank organic phase after back extraction 3 Acidifying the organic phase for recycling.
(3) Extracting thorium: preparing a cascade extraction tank of 42% TBP + sulfonated kerosene, controlling 12 stages of countercurrent extraction, 5 stages of countercurrent acid washing, 7 stages of countercurrent water washing for chloride ions, and 6 stages of countercurrent back extraction; controlling the flow ratio to be organic: feed liquid: acid washing: water washing: back extraction: acidified solution =1.25: 0.25:0.125: 1.0, washing acid is 4mol/L HNO3, washing water is deionized water with EC 17.2us/cm, and stripping solution is 1% nitric acid solution prepared by deionized water and analytically pure nitric acid at 50 ℃.
(4) Deeply extracting uranium: mixing the obtained in the previous stepThorium stripping solution containing 60.57g/L thorium and 0.26g/L uranium is added into a 3m & lt 3 & gt stainless steel concentration reaction kettle for vacuum concentration, a 500 type water jet vacuum pump is adopted, and the concentration evaporation vacuum degree is 6 multiplied by 10 4 Pa, the evaporation temperature fluctuates between 75 and 115 ℃, the steam pressure fluctuates between 0.3 and 0.4MPa, the baume degree of the concentrated solution is measured by a baume meter, when the baume degree reaches 65Be, the heating is stopped, and 2m is used for cooling 3 The single-stage extraction tank is characterized in that the extracting agent is 5 percent of TBP + sulfonated kerosene, the ratio of the extracting agent to the extracting agent is controlled to be O: A =3:1, 2-stage single-stage extraction is carried out, and the organic phase is loaded with uranium and returns to the previous uranium extraction system; pumping raffinate into 3m 3 Vacuum concentration, evaporation and crystallization are carried out in a stainless steel concentration reaction kettle, and the concentration and evaporation are still 6 multiplied by 10 of vacuum degree 4 Pa, evaporation temperature of 75-115 deg.C, steam pressure of 0.3-0.4 MPa, stopping heating when the concentrated solution reaches 75Be, naturally cooling for crystallization, cooling to room temperature, centrifuging for 24 hr, and centrifuging the precipitate with SS-800 stainless steel centrifuge to obtain mother liquor, returning the mother liquor to 42% TBP system for thorium extraction, wherein ThO is used as the raw material for thorium extraction 2 485g/L, and the nitrate concentration is 4.16mol/L; crystalline 99.99% thorium nitrate product (Th (NO) 3 ) 4 ·6H 2 O)：ThO 2 45.32％，U 3 0 8 27.2ppm，Fe 5.1ppm，TREO 16.7ppm，Cl 8.4ppm，Ca 1.32ppm、 Ti 4.63ppm。
(5) And (3) recovering rare earth: throwing 6.2m3 of raffinate from which thorium is extracted by 42 percent of TBP into a 10m3PPH tank with stirring, and slowly adding 30L of hydrogen peroxide to reduce Ce4+ to Ce3+; the acidity of raffinate is about 1.77mol/L, the pH value of rare earth is 32.27g/L, thorium is 1.23g/L and uranium is 5.6ppm, caustic soda flakes are added to adjust the pH value of the solution to 4.5, the solution is stirred for more than 1 hour, a filter press is used for filtering, filter residues are piled up in a concentrated mode, filtrate is heated to 70 ℃, sodium carbonate solution of about 100g/L is added, stirring and heat preservation are carried out for 1 to 1.5 hours, the pH value of supernatant is detected, when the pH value at the end point of reaction reaches 6.8, the addition of the sodium carbonate solution is stopped, the mixture is aged for 4 hours, and carbonate is subjected to solid-liquid separation by a 100m & lt 2 & gt plate and frame filter press, so that 715 kg of rare earth carbonate is obtained. In rare earth carbonate, TREO is 26.56%.
(6) Wastewater treatment: precipitating the wastewater after rare earth filtration, concentrating and crystallizing by using a concentration reaction kettle under the same crystallization condition as thorium nitrate concentration and crystallization condition, and spin-drying by using a centrifugal machine to obtain NaNO 3 And (4) crystals.
(7) Acid slag dissolution treatment: the components of the acid insoluble slag obtained by dissolving and filtering the optimum soluble slag by nitric acid are shown in a table 2,
table 2: the main component of the acid-insoluble residue
And recovering monazite, xenotime, zirconite and the like by gravity separation and magnetic separation, wherein the monazite and the xenotime return to the alkali roasting decomposition stage.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of other like elements in a process, method, article, or system comprising the element.
The above-mentioned serial numbers of the embodiments of the present invention are only for description, and do not represent the advantages and disadvantages of the embodiments.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (5)
1. A method for preparing thorium nitrate by utilizing monazite preferential dissolution slag is characterized by comprising the following steps:
(1) Slurry pretreatment: mixing the monazite dissolved slag into slurry, adding nitric acid, heating and stirring, controlling the concentration of residual acid and obtaining a feed liquid A;
(2) Titanium removal treatment: when the temperature of the feed liquid A is reduced to below 60 ℃, adding hydrogen peroxide and polyether, uniformly stirring, and then performing filter pressing by using a box-type or plate-type filter press to obtain filtrate B;
(3) And (3) extracting uranium: extracting the filtrate B by using a mixed solution of 5-7% of tributyl phosphate and sulfonated kerosene as an extracting agent to obtain a uranium-containing organic phase and a corresponding raffinate C, heating the uranium-containing organic phase to 40-55 ℃ by using a 1-2% nitric acid solution for back extraction, and then precipitating the back extract by using sodium hydroxide to obtain sodium diuranate;
(4) Extracting thorium: and (2) extracting the raffinate C by using a mixed solution of 38-42% of tributyl phosphate and sulfonated kerosene as an extracting agent to obtain a thorium-containing organic phase and a raffinate D, heating the thorium-containing organic phase to 45-65 ℃ by using a 0.5-1.5% nitric acid solution for back extraction to obtain a thorium back extraction solution E, wherein the contact ratio of two phases of the back extraction is O =1: (0.8-1.2);
(5) Thorium nitrate crystallization: adding the thorium strip liquor E into a concentration reaction kettle for concentration, stopping heating and cooling when the thorium oxide concentration is 300-500 g/L, carrying out uranium extraction operation on the obtained concentrated liquor in the step (3), obtaining raffinate F, carrying out vacuum concentration evaporative crystallization treatment, and continuously carrying out solid-liquid separation to obtain high-purity thorium nitrate;
wherein, after the step (5), the method further comprises the following steps: and (4) carrying out thorium extraction operation on the mother liquor obtained after solid-liquid separation in the step (5).
2. The method for preparing thorium nitrate by using monazite preferential slag according to claim 1, characterized by further comprising the following steps:
(6) And (3) recovering rare earth: stirring the raffinate D, slowly adding hydrogen peroxide and caustic soda flakes to adjust the pH value to 3.5-4.5, filtering to obtain a filtrate G, adding a sodium carbonate solution into the filtrate G to adjust the pH value to 6.4-6.8, aging and filtering to obtain the rare earth carbonate.
3. The method for preparing thorium nitrate from monazite eutectoid slag according to claim 1, wherein the step (1) specifically comprises adding more than 50% nitric acid after size mixing of the monazite eutectoid slag, stirring and heating, and controlling the concentration of the residual acid to be 2.5-4 mol/L.
4. The method for preparing thorium nitrate by using monazite preferential slag as claimed in claim 1, wherein the extraction tank used in the extraction treatment is made of PP or PPH material.
5. The method for preparing thorium nitrate by using monazite preferential soluble slag as claimed in claim 4, wherein the acid insoluble slag obtained after dissolving nitric acid in the step (1) is recovered by reselection and/or magnetic separation.
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| CN103014333A (en) * | 2012-11-27 | 2013-04-03 | 益阳鸿源稀土有限责任公司 | Separation and recovery method of uranium, thorium and rare earth in monazite slag |
| CN111004920A (en) * | 2019-09-09 | 2020-04-14 | 湖南中核金原新材料有限责任公司 | Method for smelting and separating uranium, thorium and rare earth from monazite excellent slag |
| CN112760485A (en) * | 2020-12-21 | 2021-05-07 | 湖南中核金原新材料有限责任公司 | Method for leaching valuable resources from optimal slag |
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| CN103014333A (en) * | 2012-11-27 | 2013-04-03 | 益阳鸿源稀土有限责任公司 | Separation and recovery method of uranium, thorium and rare earth in monazite slag |
| CN111004920A (en) * | 2019-09-09 | 2020-04-14 | 湖南中核金原新材料有限责任公司 | Method for smelting and separating uranium, thorium and rare earth from monazite excellent slag |
| CN112760485A (en) * | 2020-12-21 | 2021-05-07 | 湖南中核金原新材料有限责任公司 | Method for leaching valuable resources from optimal slag |
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