Method for removing impurities from acid solution of alkali roasted material of xenotime

Abstract

The present application relates to a method for removing impurities from an acid solution of an alkali-roasted material of xenotime. The method comprises the following steps: using a neutralizing agent to adjust the pH of the acid solution of an alkali-roasted material of xenotime to 3.0-3.5, performing solid-liquid separation to obtain a first filtrate; adding a reducing agent to the first filtrate to reduce the Fe 2+ The concentration is 0.2g / L~3g / L, and after adding seed crystals, the pH of the system is increased to 4.0~5.5, and the solid-liquid separation is performed to obtain a uranium-thorium precipitate and a second filtrate; an iron-thorium-uranium remover is added to the second filtrate for impurity removal.

Description

Technical Field

[0001] The present application relates to the technical field of rare earth extraction, and in particular to a method for removing impurities from an acid solution of an alkali-roasted xenotime material. Background Art

[0002] Xenotime is a phosphate rare earth ore, generally found in polymetallic composite deposits or non-metallic deposits, and coexists with a variety of rare metals such as quartz, feldspar, tourmaline and ilmenite, and can be produced as a by-product in the screening process of other minerals. Although it and monazite are both phosphate rare earth ore, but the distribution is different, the yttrium content in xenotime is high, the light rare earth content is low, the radioactive element thorium content is lower than that of monazite, and the uranium content is higher than that of monazite. Usually, the liquid alkali pressure decomposition method, concentrated sulfuric acid high temperature decomposition method, alkali melting decomposition method and sodium carbonate roasting decomposition method are used. In general, xenotime is divided into alkali method and acid method to treat xenotime, and the alkali method is more common at present.

[0003] After the alkali decomposition treatment, xenotime is generally dissolved with hydrochloric acid to obtain a rare earth chloride solution. During the acid dissolution process, thorium, uranium and iron are dissolved into the solution together with the rare earth, which is called the acid solution of the alkali roasted material of xenotime. The thorium, uranium and iron in the acid solution of the alkali roasted material of xenotime must be removed before the solution can enter the precipitation or extraction separation system. The traditional methods for removing thorium and uranium from the acid solution of the alkali roasted material of xenotime mainly include neutralization precipitation, extraction, ion exchange, complexation, etc. However, the above methods still have certain shortcomings. For example, if the neutralization precipitation method is used, the uranium content in the solution often exceeds the standard, which will cause the radioactive indicators in the subsequent separation products to exceed the standard, causing radiation environmental management problems; if extraction is used to remove uranium, a new extraction system is required. The organic phase used for uranium extraction is different from the organic phase system used for rare earth separation. The entrainment of the organic phase into the rare earth extraction and separation system can easily cause poisoning of the rare earth extraction organic phase. At the same time, the COD treatment cost in the wastewater increases, the fixed investment increases, and the cost increases significantly; if ion exchange is used to remove uranium, the exchange efficiency is low, which affects production efficiency.

[0004] Therefore, the traditional technology still needs to be improved. Summary of the invention

[0005] Based on this, the present application provides a method for removing impurities from an acid solution of an alkaline roasted material of xenotime ore, which can simply and efficiently remove thorium and uranium, and has a high rare earth yield, and can effectively improve the separation capacity of rare earth, thorium and uranium in xenotime ore.

[0006] It is specifically achieved through the following technical solutions:

[0007] On the one hand, the present application provides a method for removing impurities from an acid solution of an alkali roasted material of xenotime, comprising the following steps:

[0008] A neutralizing agent is used to adjust the pH of the acid solution of the xenotime alkali roasted material to 3.0-3.5, and solid-liquid separation is performed to obtain a first filtrate;

[0009] Add a reducing agent to the first filtrate to reduce Fe 2+ The concentration is 0.2g / L~3g / L, and after adding seed crystals, the pH of the system is raised to 4.0~5.5, and the solid-liquid separation is performed to obtain a precipitate containing uranium and thorium and a second filtrate;

[0010] An iron-thorium-uranium remover is added to the second filtrate to carry out impurity removal treatment.

[0011] In some embodiments, the pH of the system is adjusted to 4.0-5.0 after adding the seed crystals.

[0012] In some embodiments, the seed crystal is the uranium-thorium-containing precipitate, and the mass of the seed crystal is 2 to 10 times the total mass of the uranium element and the thorium element in the first filtrate.

[0013] In some embodiments, during the process of adding the seed crystals, the temperature of the first filtrate is ≤70°C.

[0014] In some embodiments, after the system pH is raised to 4.0-5.5 after adding the seed crystals, a flocculant is added for flocculation treatment, and then a solid-liquid separation step is performed;

[0015] Optionally, the flocculant includes at least one of polyacrylamide, starch, dextrin, gelatin and polyvinyl alcohol.

[0016] In some of the embodiments, the acid concentration in the xenotime alkali roasted material acid solution is 0.2 mol / L to 1.0 mol / L.

[0017] In some embodiments, the neutralizing agent includes at least one of a rare earth compound and an alkali compound.

[0018] In some embodiments, the use of a neutralizer to adjust the pH of the acid solution to 3.0-3.5 includes using a rare earth compound or an alkaline compound to adjust the pH of the system to 0.5-1.5, and then using an alkaline compound to adjust the pH of the system to 3.0-3.5;

[0019] Optionally, the rare earth compound includes at least one of a rare earth carbonate and a rare earth hydroxide;

[0020] Optionally, the alkali compound includes at least one of alkali metal hydroxide, alkali metal carbonate, ammonia water, ammonium carbonate, ammonium bicarbonate and alkali metal bicarbonate.

[0021] In some embodiments, the iron-thorium-uranium remover includes at least one of sodium sulfide, sodium hydroxide, ammonium fluoride, potassium fluoride and phosphate;

[0022] Optionally, the mass volume ratio of the sodium sulfide to the second filtrate is 0.2 kg / m 3 ~1.2kg / m 3 .

[0023] In some embodiments, the reducing agent includes at least one of iron powder and lanthanum powder.

[0024] In the above-mentioned method for removing impurities from the acid solution of the alkali roasted material of xenotime ore, a neutralizing agent is first used to adjust the pH of the acid solution of the alkali roasted material of xenotime ore to 3.0-3.5, so that the iron ions generate iron precipitates and the thorium ions generate thorium precipitates, thereby removing most of the iron and thorium in the acid solution, performing solid-liquid separation, and obtaining a first filtrate; a reducing agent is added to the first filtrate to control the specific Fe in the second filtrate. 2+ Concentration, Fe 2+ Can be reduced to UO2 2+ The high-valent uranium in the form of tetravalent uranium makes uranium exist in a tetravalent form, which is easy to precipitate and improves the precipitation rate of uranium. At the same time, after adding seed crystals, the pH of the system is raised to 4.0~5.5. Under the initiation of seed crystals, the crystal nuclei are induced to grow and form crystals. After solid-liquid separation, uranium-thorium precipitate and the second filtrate are obtained respectively, which improves the precipitation rate of thorium uranium and reduces the loss of rare earths; finally, iron-thorium-uranium remover is added to the second filtrate for impurity removal, deeply removes iron-thorium-uranium, reduces the loss of rare earths, and ensures the precipitation rate of thorium-uranium.

[0025] Furthermore, the impurity removal method is simple and easy to operate, does not require a new extraction system, can adapt to existing production processes, and effectively reduce costs. That is, the process can achieve high separation efficiency of rare earth and thorium uranium in xenotime ore, low consumption of raw and auxiliary materials, good water recycling, high rare earth yield, and realize green and efficient separation and recovery of rare earth and associated resources. DETAILED DESCRIPTION

[0026] The following is a further detailed description of a method for removing impurities from an alkali-roasted material of xenotime ore of the present application in conjunction with specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly understood.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0028] The optional scope of the terms "and / or", "or / and", and "and / or" used in this article includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, said any and all combinations include any combination of any two related listed items, any more related listed items, or all related listed items.

[0029] The weight of the relevant components mentioned in the specification of the examples of this application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the examples of this application, it is within the scope disclosed in the specification of the examples of this application. Specifically, the weight described in the specification of the examples of this application can be mass units known in the chemical industry such as μg, mg, g, and kg.

[0030] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1-10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0031] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0032] An embodiment of the present application provides a method for removing impurities from an alkali-roasted xenotime material, comprising steps S10 to S30.

[0033] Step S10: adjusting the pH of the acid solution of the xenotime alkali roasted material to 3.0-3.5 with a neutralizer, and performing solid-liquid separation to obtain a first filtrate.

[0034] Specifically, the preparation of the acid solution of the alkali-roasted xenotime ore material in step S10 includes the following steps: mixing the alkali-roasted xenotime ore material and hydrochloric acid for acid dissolution treatment to obtain the acid solution of the alkali-roasted xenotime ore material.

[0035] In some of the embodiments, before the step of mixing the alkali-roasted xenotime ore material with hydrochloric acid for acid dissolution treatment, the step further includes adding recycled water to the alkali-roasted xenotime ore material for slurry preparation.

[0036] In some of the embodiments, the volume ratio of the above-mentioned xenotime alkali-roasted material to the above-mentioned recycled water is 1:1~1.5, for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5. In some examples, it can be within the range formed by any two of these point values ​​as end values, the same below.

[0037] In some of the embodiments, the acid concentration in the above-mentioned xenotime alkali roasting material acid solution is 0.2 mol / L to 1.0 mol / L, for example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1.0 mol / L.

[0038] In some of the embodiments, the acid concentration in the above-mentioned xenotime alkali roasting material acid solution is 0.3 mol / L to 1.0 mol / L.

[0039] In some embodiments, the neutralizing agent includes at least one of a rare earth compound and an alkali compound.

[0040] In some embodiments, the neutralizing agent is used to adjust the pH of the acid solution to 3.0-3.5, including using a rare earth compound or an alkaline compound to adjust the pH of the system to 0.5-1.5, and then using an alkaline compound to adjust the pH of the system to 3.0-3.5.

[0041] It is understandable that the solution is highly acidic after acid dissolution. First, adjust the pH value to 3.0~3.5 with materials such as rare earth carbonate, sodium carbonate or ammonium bicarbonate. This step can allow some impurity ions that can form precipitation under the acidic conditions, such as some iron ions, to be initially precipitated, thereby preliminarily removing impurities in the solution and creating conditions for subsequent more precise pH adjustment and product purification. Further precise adjustment can enable the solution to reach the optimal pH range for precipitation or dissolution of specific rare earth compounds, which is conducive to further separation of rare earth elements and other impurities and improving the purity of rare earth products.

[0042] In some embodiments, the neutralizing agent is used to adjust the pH of the acid solution to 3.0-3.5, including using a rare earth compound or an alkaline compound to adjust the pH of the system to 0.5-1.0, and then using an alkaline compound to adjust the pH of the system to 3.0-3.5.

[0043] In some of the embodiments, in the process of adjusting the pH of the acid solution by using a neutralizing agent, the system temperature is controlled to be 70° C. to 90° C., and the insulation time is 1 h to 3 h.

[0044] It can be understood that an increase in temperature helps certain impurity ions such as iron ions to form more stable precipitates, which promotes more complete precipitation of these impurities, facilitates their subsequent removal by filter press separation, and improves the purity of the filtrate.

[0045] In some embodiments, the rare earth compound includes rare earth carbonate or rare earth hydroxide.

[0046] In some embodiments, the rare earth compound includes lanthanum cerium carbonate or lanthanum cerium hydroxide.

[0047] In some embodiments, the alkali compound includes alkali metal hydroxides and alkali metal carbonates.

[0048] In some embodiments, the alkaline compound includes at least one of sodium carbonate, ammonium bicarbonate or sodium hydroxide.

[0049] Step S20: Add a reducing agent to the first filtrate to reduce Fe 2+ The concentration is 0.2g / L~3g / L. After adding seed crystals, the pH of the system is adjusted to 4.0~5.5, and the solid-liquid separation is performed to obtain a uranium-thorium-containing precipitate and a second filtrate.

[0050] It is understandable that the above Fe 2+ The concentration of 0.2g / L~3g / L can take the minimum and maximum values ​​in the range of 0.2g / L~3g / L, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, 0.2g / L, 0.3g / L, 0.4g / L, 0.5g / L, 0.6g / L, 0.7g / L, 0.8g / L, 0.9g / L, 1.0g / L, 1.1g / L, 1.2g / L, 1.3g / L, 1.4g / L, 1.5g / L, 1.6g / L, 1.7g / L, 1.8g / L, 1.9g / L, 2.0g / L, 2.1g / L, 2.2g / L, 2.3g / L, 2.4g / L, 2.5g / L, 2.6g / L, 2.7g / L, 2.8g / L, 2.9g / L or 3.0g / L, or a range consisting of any two of these values, for example, 1.0g / L to 3.0g / L.

[0051] After adding the seed crystals, the pH of the system is adjusted to 4.0-5.5, that is, the minimum and maximum values ​​in the range of 4.0-5.5, and each value between the minimum and maximum values, can be taken. Specific examples include but are not limited to: 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5, or a range consisting of any two of these values, for example, 4.0-5.2.

[0052] In some embodiments, the pH of the system is adjusted to 4.0-5.0 after adding the seed crystals.

[0053] In some embodiments, the reducing agent includes at least one of iron powder and lanthanum powder.

[0054] In a specific example, the reducing agent is iron powder.

[0055] It can be understood that, on the one hand, (1) when iron powder is put into the aqueous solution containing uranium, UO2 2+ Diffusion transfers to the surface of iron, followed by active site adsorption and inactive site adsorption; (2) On the other hand, iron is a metal with strong reducing properties. When iron powder is added, under acidic conditions, the iron powder will react with the uranyl ions (UO2 2+ )The following redox reaction occurs: Fe+UO2(aq) 2+ → UO2(s)+Fe 2+ , reducing uranium from a higher valence state (such as hexavalent) to tetravalent, making uranium exist in a tetravalent form, easy to precipitate, and increasing the precipitation rate of uranium. (3) On the other hand, the ferrous ions produced by the reaction of iron and acid are reducing, UO2 2+ +2Fe 2+ →UO2(s)+2Fe 3+ This adsorption method based on chemical reaction has high selectivity and can effectively remove uranium impurities from the first filtrate, reduce the interference of uranium in subsequent processes, and improve the purity of rare earth products. (4) Iron powder produces new hydrogen in acidic solution, which has a reducing effect and can reduce uranyl. UO2 2+ +2[H]→UO2(s)+ 2H + (5) Iron powder can also reduce some less active impurity metal elements, thereby improving the flocculation effect.

[0056] In some embodiments, hydrochloric acid is added to the first filtrate while adding the reducing agent to maintain the pH of the system at 2.0-3.0.

[0057] Under acidic conditions, Fe 2+ It has certain reducing properties and can undergo reduction reaction with uranium.

[0058] In some of the embodiments, the seed crystal is the uranium-thorium-containing precipitate, and the mass of the seed crystal is 2 to 10 times the total mass of the uranium element and the thorium element in the first filtrate.

[0059] Furthermore, the seed crystal is the uranium-thorium-containing precipitate, and the mass of the seed crystal is 3 to 10 times the total mass of the uranium element and the thorium element in the first filtrate.

[0060] In some embodiments, during the process of adding the seed crystals, the temperature of the first filtrate is ≤70°C.

[0061] Furthermore, during the process of adding the seed crystals, the temperature of the first filtrate is ≤50°C.

[0062] It can be understood that the addition of seed crystals provides a growth core for new uranium precipitation. The presence of seed crystals can reduce the energy barrier of precipitation formation, making it easier for uranium ions to gather and precipitate on the surface of the seed crystals, thereby accelerating the precipitation process of uranium, improving precipitation efficiency, reducing the time required for precipitation, and improving production efficiency. By controlling the temperature of the first filtrate at a lower temperature, the reaction of uranium ions with other substances may be more stable and complete, reducing the occurrence of side reactions. At the same time, a lower temperature is also conducive to the precipitation of uranium thorium precipitation.

[0063] In some of the embodiments, after the system pH is raised to 4.0-5.5 after adding the seed crystals, a flocculant is added for flocculation treatment, and then a solid-liquid separation step is performed.

[0064] Specifically, after adding the seed crystals, the method further includes adding a sodium hydroxide solution with a concentration of 0.1 mol / L to 1 mol / L to finely adjust the pH of the system to 4.0 to 5.5, and then adding a flocculant to perform flocculation treatment.

[0065] It can be understood that the above system is adjusted to the range of 4.0~5.5, which is close to the precipitation pH range of uranium-thorium hydroxide, so that the uranium-thorium ions can be more fully hydrolyzed and precipitated. If the pH value is not adjusted properly, rare earth elements may also precipitate or undergo other chemical reactions, resulting in the loss of rare earth elements. In the above pH range of 4.0~5.5, the stability of rare earth elements in the solution can be maintained while effectively removing uranium-thorium impurities, ensuring the recovery rate of rare earth elements and improving the economic benefits of the entire extraction process. The addition of flocculants can interact with the surface charges of suspended particles in the solution (including uranium-thorium precipitate particles and other tiny impurity particles that may exist), so that the particles aggregate to form larger flocs. That is, the addition of flocculants further enlarges the uranium precipitate particles, promotes the aggregation and sedimentation of the precipitate, reduces the time required for precipitation, and improves production efficiency.

[0066] In some embodiments, the flocculant includes at least one of polyacrylamide, starch, dextrin, gelatin and polyvinyl alcohol.

[0067] Step S30: adding an iron-thorium-uranium remover to the second filtrate to remove impurities.

[0068] In some embodiments, the iron-thorium-uranium remover includes at least one of sodium sulfide, sodium hydroxide, ammonium fluoride, potassium fluoride and phosphate.

[0069] It can be understood that adding sodium sulfide can precipitate iron, thorium, uranium and heavy metal impurities, adding sodium hydroxide can form hydroxide precipitates, adding ammonium fluoride and potassium fluoride can form fluoride precipitates, adding phosphates can form phosphoric acid precipitates, and the like.

[0070] In some embodiments, the mass volume ratio of the sodium sulfide to the second filtrate is 0.2 kg / m 3 ~1.2kg / m 3 .

[0071] Furthermore, the mass volume ratio of the sodium sulfide to the second filtrate is 0.2 kg / m 3 ~1kg / m 3 .

[0072] Furthermore, the above-mentioned phosphate includes at least one of trisodium phosphate, sodium dihydrogen phosphate, and sodium (ammonium) dihydrogen phosphate.

[0073] In some of the embodiments, after adding the iron-thorium-uranium remover to the second filtrate for impurity removal treatment, the process further includes adding a flocculant for flocculation treatment, and then performing a solid-liquid separation step.

[0074] In some embodiments, the flocculant includes at least one of polyacrylamide, starch, dextrin, gelatin and polyvinyl alcohol.

[0075] It is understandable that in the second filtrate, the iron, thorium and uranium precipitate is in a colloidal state, and there may be fine particles suspended in the solution, which may be filtered through during filtration, resulting in the uranium content in the obtained rare earth chloride solution not meeting the standard. Flocculants can make these tiny particles aggregate with each other to form larger flocs and further combine with other possible impurities to form larger precipitation particles, thereby improving the removal efficiency of impurities. This helps to further reduce the content of impurities such as uranium, thorium and iron, and improve the purity of rare earth elements.

[0076] Furthermore, during the process of adding the iron-thorium-uranium remover to the second filtrate for impurity removal, hydrochloric acid is used to control the pH of the system to be 4.0-5.5.

[0077] In some of the embodiments, according to the requirements of the national standard GB4148 "Mixed Rare Earth Chlorides", when the rare earth REO is greater than 260g / L, the thorium is less than 0.1g / L. In the industry, it is generally required that the uranium content shall not be higher than that of thorium. According to the REO content of 187.23g / L in the filtrate, the thorium and uranium contents should be less than 0.072g / L.

[0078] In the above-mentioned method for removing impurities from the acid solution of the alkali roasted material of xenotime ore, a neutralizing agent is first used to adjust the pH of the acid solution of the alkali roasted material of xenotime ore to 3.0-3.5, so that the iron ions generate iron precipitates and the thorium ions generate thorium precipitates, thereby removing most of the iron and thorium in the acid solution, performing solid-liquid separation, and obtaining a first filtrate; a reducing agent is added to the first filtrate to control the specific Fe in the second filtrate. 2+ Concentration, Fe 2+ Can be reduced to UO2 2+ The high-valent uranium in the form of tetravalent uranium makes uranium exist in a tetravalent form, which is easy to precipitate and improves the precipitation rate of uranium. At the same time, after adding seed crystals, the pH of the system is raised to 4.0~5.5. Under the initiation of seed crystals, the crystal nuclei are induced to grow and form crystals. After solid-liquid separation, uranium-thorium precipitate and the second filtrate are obtained respectively, which improves the precipitation rate of thorium uranium and reduces the loss of rare earths; finally, iron-thorium-uranium remover is added to the second filtrate for impurity removal, deeply removes iron-thorium-uranium, reduces the loss of rare earths, and ensures the precipitation rate of thorium-uranium.

[0079] The above-mentioned method for removing impurities from the acid solution of the alkali roasted material of xenotime is simple and easy to operate, does not require a new extraction system, can adapt to the existing production process, and effectively reduce costs. That is, the process can make the rare earth and thorium uranium in xenotime highly efficient, consume less raw and auxiliary materials, have good water recycling, and have a high rare earth yield, thus realizing the green and efficient separation and recovery of rare earth and associated resources.

[0080] In order to make the purpose, technical solutions and advantages of the present application more concise and clear, the present application is described with the following specific embodiments, but the present application is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present application and can be used to describe the present application, and cannot be understood as limiting the scope of the present application. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

[0081] In order to better illustrate the present application, the present application is further described below in conjunction with the embodiments. The following are specific embodiments.

[0082] The reaction kettle and stirring tank used in the embodiment are acid-base resistant tanks with stirring paddles made of PP or PPH materials, and the filter press and precision filtration used in the embodiment are plate-type and chamber-type filter presses and precision filtration equipment familiar in the industry. The centrifuge is a three-legged high-speed centrifugal stainless steel or corrosion-resistant centrifuge familiar in the industry.

[0083] Example 1

[0084] Table 1 Main chemical composition of calcined alkali cake of xenotime

[0085]

[0086] (1) Acid dissolution: 1 ton of washed xenotime ore roasted alkali cake with a moisture content of 49.6% and a REO content of 51.7% was prepared according to the ratio of actual weight of alkali cake to volume of recycled water = 1:1, and then 30% industrial hydrochloric acid was slowly added. The mixture was heated to above 90°C and the pH value of the solution was checked at any time. When the pH value stabilized at 1.5, hydrochloric acid was continued to be added. The mixture was stirred for 2 hours at the same time. Solid-liquid separation was performed. When the residual acid reached the standard of 0.67 mol / L, an acid solution of xenotime ore alkali roasted material was obtained.

[0087] (2) Neutralization precipitation: Add sodium carbonate to the acid solution obtained in (1) above while it is hot to neutralize the residual acid, adjust the pH value to 1.0, and then slowly add 0.5 mol / L sodium hydroxide solution to finely adjust the pH to 3.5. Use the residual heat of the solution to keep it at 90°C~75°C for 1 hour, filter it with a filter press to obtain iron precipitate and the first filtrate respectively, and the first filtrate enters the next step. The REO content in the first filtrate is 187.23 g / L, the iron content is 1.07 g / L, the thorium content is 0.063 g / L, and the uranium content is 0.65 g / L, which does not meet the requirements of GB / T4148, which specifically requires that the thorium uranium content is ≤0.1 (g / L) / 260 (g / L) REO.

[0088] (3) Further removal of thorium and uranium: Add 300 mesh reduced iron powder to the first filtrate obtained in (2) above in a mass volume ratio of 5 g / L, add hydrochloric acid until the pH value is 2.5, and check the Fe content in the solution. 2+ The concentration is 2.3 g / L. When the temperature of the first filtrate after mixing drops to 35°C, add the uranium-thorium precipitate obtained in this process as a seed crystal to the first filtrate after mixing. The mass of the seed crystal added is 5 times the total mass of the uranium element and the thorium element in the first filtrate after mixing. Stir for 30 minutes, then slowly add 1 mol / L sodium hydroxide solution to finely adjust the pH to 4.5, add 0.3% flocculant (specifically polyacrylamide), the amount of flocculant added is 0.05% of the solution volume, settle, and finely filter to obtain the uranium-thorium precipitate and the second filtrate respectively. The uranium-thorium precipitate obtained can be used as a seed crystal for the next precipitation and uranium removal. The iron content in the second filtrate exceeds the standard, and enters the next step of impurity removal.

[0089] (4) Impurity removal: The second filtrate obtained in the above (3) was concentrated in a concentration reactor. When the concentration of the second filtrate reached 310 g / L, it was transferred to a stirring tank and sodium sulfide with a concentration of 20 g / L was slowly dripped into the second filtrate at a mass volume ratio of 0.5 kg / m 3 At the same time, use hydrochloric acid to control the pH at 4.5, stir for 1 hour, let it stand for more than 8 hours, use a filter press to separate the solid and liquid, add flocculants, filter press to get qualified rare earth filtrate for rare earth extraction separation. The thorium content is 0.1mg / L, the uranium content is 38.5mg / L, and the REO content is 273g / L.

[0090] Example 2

[0091] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 2 is basically the same as that in Example 1, except that the slurry is prepared according to the actual weight of the alkali cake: the volume of the recycled water = 1:1.5.

[0092] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0093] Example 3

[0094] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 3 is basically the same as that in Example 1, except that, in step (2), the precipitation is neutralized: 0.5 mol / L sodium hydroxide solution is added to the acid solution obtained in the above (1) while it is hot to neutralize the residual acid, the pH is adjusted to 3.5, the solution is kept warm at 90°C to 75°C for 1 hour using the residual heat of the solution, and filtered by a filter press to obtain an iron precipitate and a first filtrate, respectively.

[0095] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0096] Example 4

[0097] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 4 is basically the same as that in Example 1, except that the residual acid concentration in the acid solution is controlled to be 0.3 mol / L in step (1).

[0098] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0099] Example 5

[0100] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 5 is basically the same as that in Example 1, except that the residual acid concentration in the acid solution is controlled to be 1.0 mol / L in step (1).

[0101] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0102] Example 6

[0103] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 6 is basically the same as that in Example 1, except that the residual acid concentration in the acid solution is controlled to be 0.2 mol / L in step (1).

[0104] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0105] Example 7

[0106] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 7 is basically the same as that in Example 1, except that, during the neutralization and precipitation in step (2), sodium carbonate is added to adjust the pH value to 1.5, and 1 mol / L sodium hydroxide solution is slowly added to finely adjust the pH to 3.5.

[0107] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0108] Example 8

[0109] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 8 is basically the same as that in Example 1, except that the Fe 2+ The concentration is 1.03g / L.

[0110] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0111] Example 9

[0112] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 9 is basically the same as that in Example 1, except that the Fe 2+ The concentration is 3.00g / L.

[0113] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0114] Example 10

[0115] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 10 is basically the same as that in Example 1, except that in step (3), when the temperature drops to 50° C., seed crystals are added to the mixed first filtrate.

[0116] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0117] Embodiment 11

[0118] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 11 is basically the same as that in Example 1, except that in step (3), when the temperature drops to 15° C., seed crystals are added to the first filtrate after mixing.

[0119] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0120] Example 12

[0121] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 12 is basically the same as that in Example 1, except that in step (3), when the temperature drops to 70° C., seed crystals are added to the first filtrate after mixing.

[0122] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0123] Embodiment 13

[0124] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 13 is basically the same as that in Example 1, except that the amount of seed crystal added in step (3) is 10 times the total mass of uranium and thorium in the first filtrate after mixing.

[0125] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0126] Embodiment 14

[0127] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 14 is basically the same as that in Example 1, except that the amount of seed crystal added in step (3) is twice the total mass of uranium and thorium in the first filtrate after mixing.

[0128] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0129] Embodiment 15

[0130] The method for removing impurities from the acid solution of the alkali roasted material of xenotime in Example 15 is basically the same as that in Example 1, except that the amount of seed crystals added in step (3) is 3 times the total mass of uranium and thorium in the first filtrate after mixing.

[0131] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0132] Example 16

[0133] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 16 is basically the same as that in Example 1, except that the mass volume ratio of sodium sulfide added to the second filtrate in step (4) is 0.2 kg / m 3 .

[0134] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0135] Embodiment 17

[0136] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 17 is basically the same as that in Example 1, except that the mass volume ratio of sodium sulfide added to the second filtrate in step (4) is 1 kg / m 3 .

[0137] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0138] Embodiment 18

[0139] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 18 is basically the same as that in Example 1, except that the mass volume ratio of sodium sulfide added to the second filtrate in step (4) is 1.2 kg / m 3 .

[0140] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0141] Embodiment 19

[0142] The impurity removal method of the acid solution of the alkali roasted material of xenotime ore in Example 19 is basically the same as that in Example 1, except that in steps (3) and (4), the pH value is 5.0 from the addition of iron powder to the first filtrate for reduction and then the addition of sodium hydroxide solution to adjust the pH value to the subsequent concentration and addition of sodium sulfide.

[0143] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0144] Embodiment 20

[0145] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 20 is basically the same as that in Example 1, except that after adding the seed crystals in step (3), 0.5 mol / L sodium hydroxide solution is slowly added to finely adjust the pH to 4.0.

[0146] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0147] Embodiment 21

[0148] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 21 is basically the same as that in Example 1, except that no flocculant is added after the pH of the sodium hydroxide solution is adjusted in step (3).

[0149] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0150] Embodiment 22

[0151] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Example 22 is basically the same as that in Example 1, except that after adding the seed crystals in step (3), 0.5 mol / L sodium hydroxide solution is slowly added to finely adjust the pH to 5.5.

[0152] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0153] Comparative Example 1

[0154] The impurity removal method of the acid solution of the alkali roasted material of xenotime in Comparative Example 1 is basically the same as that in Example 1, except that the Fe 2+ The concentration is 0.15g / L.

[0155] Other conditions and parameters are the same as those in Example 1. Please see Table 2 for specific test results.

[0156] Comparative Example 2

[0157] Comparative Example 2 adopts an acid dissolution one-step neutralization process, and the specific steps are as follows: (1) Acid dissolution: 1 ton of washed xenotime ore roasted alkali cake, the alkali cake has a moisture content of 49.6%, and a REO content of 51.7%, is slurried according to the ratio of actual weight of alkali cake: volume of recycled water = 1:1, and then 30% industrial hydrochloric acid is slowly added, and the solution is heated to above 90°C. The pH value of the solution is checked at any time. When the pH value stabilizes at 1.5, hydrochloric acid is continued to be added, and the solution is stirred for 2 hours at this temperature for solid-liquid separation. After the residual acid is measured at 0.67 mol / L and meets the standard, an acid solution of xenotime ore alkali roasted material is obtained.

[0158] (2) Neutralization precipitation: add 0.5 mol / L sodium hydroxide solution to the acid solution obtained in the above (1) while it is hot to adjust the pH to 4.5 in one step, keep the solution at 90°C-75°C for 1 hour using the residual heat of the solution, and filter by filter press to obtain iron thorium uranium precipitate and the first filtrate, respectively. The first filtrate is directly used as the mixed rare earth chloride solution to enter the concentration process.

[0159] test:

[0160] The rare earth yield, thorium / rare earth ratio and uranium / rare earth ratio in the impurity removal method of the xenotime alkali roasted material in the embodiment and the comparative example were tested, wherein:

[0161] Rare earth leaching rate = (rare earth concentration before impurity removal * initial solution volume) / (weight of alkali cake * rare earth content in alkali cake);

[0162] Total rare earth recovery rate = (rare earth concentration after impurity removal * solution volume) / (rare earth concentration before impurity removal * initial solution volume) * rare earth leaching rate of alkali cake;

[0163] Thorium / REO ratio = Thorium concentration in the solution after impurity removal / Rare earth concentration in the solution after impurity removal;

[0164] Uranium / REO ratio = uranium concentration in the solution after impurity removal / rare earth concentration in the solution after impurity removal.

[0165] Please see Table 2 for the specific test results. A: actual weight of alkali cake: ratio of recycled water volume to slurry preparation; B: residual acid concentration in the first filtrate (mol / L); C: Fe 2+ concentration; D: mass of seed added / total mass of uranium and thorium in the second filtrate; E: temperature of the first filtrate when seed is added (°C); F: mass volume ratio of sodium sulfide to the third filtrate (kg / m 3 ); G: whether to add flocculant after raising the system pH after adding seed crystals to the first filtrate; H: pH value of the system after adding seed crystals; I: thorium content in the first filtrate (g / L); J: uranium content in the first filtrate (g / L); K: rare earth yield after impurity removal (%); L: thorium / REO in the solution after impurity removal (ppm); M: uranium / REO in the solution after impurity removal (ppm).

[0166] Table 2

[0167]

[0168] By comparing Example 2 with Example 1, it can be seen that according to the slurry adjustment of the actual weight of alkali cake: the volume of recycled water = 1:1.5, the solid content of the obtained slurry decreases, which is beneficial to the medium transmission and the acid dissolution reaction speed in the initial stage of the reaction, but has little effect on the rare earth leaching rate. If the residual acid concentration of the acid dissolution is maintained, the amount of acid needs to be increased, which increases the pressure of subsequent neutralization and impurity removal.

[0169] By comparing Example 3 and Example 7 with Example 1, it can be seen that by using 0.5 mol / L sodium hydroxide solution to adjust the pH to 3.5 in one step, the ratio of thorium uranium to rare earth in the rare earth chloride solution after removing thorium uranium increases, the concentration of the rare earth solution decreases, and the energy consumption of concentration increases. By using 1 mol / L sodium hydroxide solution to slowly add and finely adjust the pH to 3.5, the rare earth yield decreases slightly, the thorium precipitation rate increases, and the uranium removal rate is not greatly affected.

[0170] Compared with Example 1, Examples 4 to 6 show that the rare earth leaching rate is slightly decreased by controlling the acid-soluble residual acid at 0.3 mol / L. The amount of acid used and the residual acid concentration affect the rare earth leaching rate, which increases the ratio of thorium uranium to rare earth. When the acid-soluble residual acid is controlled at 1.0 mol / L, the rare earth leaching rate is slightly increased, but the amount of acid used increases, which increases the cost of subsequent neutralization. When the acid-soluble residual acid is controlled at 0.2 mol / L, the rare earth leaching rate decreases, and the ratio of thorium uranium to rare earth in the rare earth chloride solution increases.

[0171] Comparison between Examples 1 and 8-9 and Comparative Example 1 shows that Fe 2+ At 1.03 g / L, the removal rate of uranium decreased slightly. Under the same acidity conditions, the concentration of ferrous ions affects the valence state of uranium.2+ At 3.00 g / L, the uranium removal rate increased slightly, but the iron content increased, making subsequent iron removal more difficult. 2+ At 0.15 g / L, the uranium removal rate was significantly reduced and did not meet the requirements.

[0172] Compared with Example 1, when the temperature dropped to 50°C, the uranium removal rate was slightly reduced by adding seed crystals into the solution, indicating that the temperature increased and the uranium removal rate decreased. 4+ More easily oxidized to UO2 2+ , which is not conducive to the removal of uranium precipitation. When the temperature drops to room temperature (15°C), seed crystals are added to the solution, and the uranium removal rate increases slightly, indicating that the temperature decreases and U 4+ More stable, conducive to the precipitation and removal of uranium. At a temperature of 70°C, the residual uranium content in the solution is large, and the uranium removal rate decreases.

[0173] Comparison of Examples 13 to 15 with Example 1 shows that the amount of uranium added to the seed crystal is 10 times the uranium content in the solution, and the uranium removal rate is improved, but the increase in the uranium content in the solution increases the radiation risk. At the same time, the amount of addition increases, and the amount of other impurities introduced increases, increasing the pressure of impurity removal. The amount of uranium added to the seed crystal is 3 times the uranium content in the solution, and the uranium removal rate decreases. The amount of uranium added to the seed crystal is 2 times the uranium content in the solution, and the uranium removal rate decreases significantly.

[0174] It can be seen from the comparison between Examples 16 to 18 and Example 1 that the amount of sodium sulfide added is 0.2 kg sodium sulfide / cubic solution, and impurities such as iron and aluminum increase slightly, but the yield of rare earth increases slightly. The amount of sodium sulfide added is 1.0 kg sodium sulfide / cubic solution, and the content of iron, aluminum, thorium and uranium all decreases, indicating that sodium sulfide is beneficial to remove impurities and thorium and uranium. The amount of sodium sulfide added is 1.2 kg sodium sulfide / cubic solution, and the content of iron, aluminum, thorium and uranium all decreases, and the yield of rare earth decreases.

[0175] Comparison of Examples 19-20 and 22 with Example 1 shows that after adding the seed crystals, 0.5 mol / L sodium hydroxide solution is slowly added to finely adjust the pH to 5.0, the thorium uranium / rare earth ratio is reduced, and the rare earth yield is improved. After adding the seed crystals, 0.5 mol / L sodium hydroxide solution is slowly added to finely adjust the pH to 4.0, and the uranium removal rate decreases slightly, indicating that the decrease in pH is not conducive to the removal of uranium, but is conducive to the increase in the yield of rare earths. After adding the seed crystals, 0.5 mol / L sodium hydroxide solution is slowly added to finely adjust the pH to 5.5, the thorium uranium / rare earth ratio is reduced, but the rare earth yield decreases.

[0176] Comparison between Example 21 and Example 1 shows that after the pH of the sodium hydroxide solution is adjusted without adding a flocculant, the ratio of thorium uranium / rare earth increases and fine particles exist.

[0177] Comparative Examples 1 and 2 show that the removal rate of thorium and uranium is higher than that in the comparative examples, the thorium and uranium content in the rare earth chloride solution meets the standard of mixed rare earth chloride solution, and the rare earth yield is higher. The process can separate rare earth and thorium and uranium in xenotime ore with high efficiency, less consumption of raw and auxiliary materials, good water recycling, high rare earth yield, and realize green and efficient rare earth and associated resources.

[0178] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0179] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be based on the attached claims.

Claims

1. A method for removing impurities from an acid solution of an alkali-roasted xenotime material, characterized in that: The steps include: A neutralizing agent is used to adjust the pH of the acid solution of the xenotime alkali roasted material to 3.0-3.5, and solid-liquid separation is performed to obtain a first filtrate; Add a reducing agent to the first filtrate to reduce Fe 2+ The concentration is 0.2g / L~3g / L, and after adding seed crystals, the pH of the system is raised to 4.0~5.5, and the solid-liquid separation is performed to obtain a precipitate containing uranium and thorium and a second filtrate; An iron-thorium-uranium remover is added to the second filtrate to carry out impurity removal treatment.

2. The method for removing impurities from the acid solution of the alkali roasted xenotime material according to claim 1, characterized in that: After adding the seed crystals, the pH of the system was adjusted to 4.0~5.

0.

3. The method for removing impurities from the acid solution of the alkali roasted xenotime material according to claim 1, characterized in that: The seed crystal is the uranium-thorium-containing precipitate, and the mass of the seed crystal is 2 to 10 times the total mass of the uranium element and the thorium element in the first filtrate.

4. The impurity removal method of the xenotime alkali roasted material acid solution according to any one of claims 1 to 3, characterized in that: During the process of adding the seed crystals, the temperature of the first filtrate is ≤70°C.

5. The method for removing impurities from an acid solution of an alkali-roasted xenotime material according to any one of claims 1 to 3, characterized in that: After adding the seed crystals and raising the system pH to 4.0-5.5, a flocculant is added for flocculation treatment, and then a solid-liquid separation step is performed; Optionally, the flocculant includes at least one of polyacrylamide, starch, dextrin, gelatin and polyvinyl alcohol.

6. The method for removing impurities from an acid solution of an alkali-roasted xenotime material according to any one of claims 1 to 3, characterized in that: The acid concentration in the xenotime alkali roasting material acid solution is 0.2 mol / L to 1.0 mol / L.

7. The method for removing impurities from an acid solution of an alkali-roasted xenotime material according to any one of claims 1 to 3, characterized in that: The neutralizer includes at least one of a rare earth compound and an alkali compound.

8. The method for removing impurities from the acid solution of the alkali roasted xenotime material according to claim 7, characterized in that: The step of adjusting the pH of the acid solution to 3.0-3.5 by using a neutralizer comprises adjusting the pH of the system to 0.5-1.5 by using a rare earth compound or an alkaline compound, and then adjusting the pH of the system to 3.0-3.5 by using an alkaline compound; Optionally, the rare earth compound includes at least one of a rare earth carbonate and a rare earth hydroxide; Optionally, the alkali compound includes at least one of alkali metal hydroxide, alkali metal carbonate, ammonia water, ammonium carbonate, ammonium bicarbonate and alkali metal bicarbonate.

9. The method for removing impurities from an acid solution of an alkali-roasted xenotime material according to any one of claims 1 to 3 and 8, characterized in that: The iron-thorium-uranium remover comprises at least one of sodium sulfide, sodium hydroxide, ammonium fluoride, potassium fluoride and phosphate; Optionally, the mass volume ratio of the sodium sulfide to the second filtrate is 0.2 kg / m 3 ~1.2kg / m 3 .

10. The method for removing impurities from an acid solution of an alkali-roasted xenotime material according to any one of claims 1 to 3 and 8, characterized in that: The reducing agent includes at least one of iron powder and lanthanum powder.

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