Treatment method of xenotime acid-soluble slag

Abstract

The invention relates to a method for treating xenotime acid-soluble slag, which comprises the following steps: mixing xenotime acid-soluble slag with water, sorting, mixing the obtained acid-soluble slag light mud with a hydrochloric acid solution and a reducing agent, carrying out acid dissolution, and carrying out first solid-liquid separation to obtain a first filtrate; the mass concentration of the hydrochloric acid solution is 15-25%, and the ratio of the volume of the hydrochloric acid solution to the mass of the acid-soluble slag light mud is 3m < 3 > / 1000kg-5m < 3 > / 1000kg; mixing the first filtrate with an oxidizing agent to carry out oxidation reaction, mixing the obtained oxidation reaction solution with a phosphorus source to carry out first precipitation treatment, and then carrying out second solid-liquid separation to respectively obtain an iron precipitate and a second filtrate; adjusting the pH value of the second filtrate to 3.8-4.2 by adopting a first pH regulator, then adding hydrogen peroxide to carry out second precipitation treatment, and carrying out third solid-liquid separation to respectively obtain a thorium-uranium precipitate and a third filtrate; and mixing the third filtrate with a rare earth precipitant, and carrying out third precipitation treatment to obtain a rare earth precipitate.

Description

Technical Field

[0001] The present application relates to the technical field of rare earth extraction, and in particular to a method for treating xenotime acid slag. Background Art

[0002] With the development of mineral processing technology, xenotime has gradually become an important phosphate rare earth ore, mainly derived from the mineral processing byproduct of zircon-titanium ore, often accompanied by rutile, ilmenite, zircon and a small amount of radioactive elements thorium and uranium. The decomposition methods commonly used in industry are mainly acid roasting and alkali roasting decomposition. The most widely used one is alkali roasting decomposition. Xenotime is roasted with alkali such as sodium hydroxide and sodium carbonate, and rare earth, thorium, uranium, etc. form oxides that are easily soluble in hydrochloric acid, while undecomposed ilmenite, zircon, xenotime and monazite are insoluble in acid. When hydrochloric acid is dissolved to produce rare earth chloride, iron, aluminum, thorium, uranium, etc. enter the precipitate slag together with acid-insoluble substances, which is called xenotime acid slag. The main components of xenotime acid slag are iron, silicon, titanium, rare earth, zirconium, aluminum, barium, thorium, uranium and other elements. The rare earth content is generally 5%~15%, and some are even higher than 15%. The thorium content is generally 2%~5%, and some are as high as 5%. Rare earth, thorium and uranium are important strategic resources, and xenotime acid slag needs to be comprehensively recycled. At present, there are very few research reports on the comprehensive recycling of rare earth, iron and thorium and uranium in xenotime acid slag. Summary of the invention

[0003] Based on this, the present application provides a method for processing xenotime acid slag that can extract rare earth, thorium, uranium and iron elements.

[0004] The technical solution of this application to solve the above technical problems is as follows.

[0005] On the one hand, the present application provides a method for treating xenotime acid slag, comprising the following steps:

[0006] After mixing the xenotime acid slag and water, the mixture is sorted to obtain acid slag light mud;

[0007] The acid-soluble slag light mud, hydrochloric acid solution and reducing agent are mixed and acid-dissolved, and then a first solid-liquid separation is performed to obtain a first filtrate; the mass concentration of the hydrochloric acid solution is 15% to 25%, and the mass ratio of the volume of the hydrochloric acid solution to the acid-soluble slag light mud is 3 m 3 / 1000 kg ~5 m 3 / 1000kg;

[0008] The first filtrate and an oxidant are mixed to perform an oxidation reaction to obtain an oxidation reaction liquid;

[0009] The oxidation reaction liquid and the phosphorus source are mixed to perform a first precipitation treatment, and then a second solid-liquid separation is performed to obtain an iron precipitate and a second filtrate respectively;

[0010] The pH value of the second filtrate is adjusted to 3.8-4.2 by using a first pH adjusting agent, and then hydrogen peroxide is added to perform a second precipitation treatment, and a thorium-uranium precipitate and a third filtrate are obtained by performing a third solid-liquid separation.

[0011] The third filtrate and the rare earth precipitant are mixed to perform a third precipitation treatment to obtain a rare earth precipitate.

[0012] In some of the embodiments, in the method for treating xenotime acid slag, the mass concentration of the hydrochloric acid solution is 15% to 20%.

[0013] In some of the embodiments, in the method for treating xenotime acid slag, the mass ratio of the rare earth oxides in the acid slag light mud to the reducing agent is 1:(0.02~0.3); optionally, the mass ratio of the rare earth oxides in the acid slag light mud to the reducing agent is 1:(0.05~0.3).

[0014] In some embodiments, in the method for treating xenotime acid slag, the molar ratio of the phosphorus source to the trivalent iron in the oxidation reaction solution is 0.9-1:1; and / or

[0015] The first precipitation treatment step also includes a step of using a second pH adjuster to adjust the pH value of the oxidation reaction solution and the first precipitation solution of the phosphorus source to 1.5~2.5; optionally, the pH value of the first precipitation solution is adjusted to 1.5~2.

[0016] In some embodiments, in the method for treating xenotime acid slag, in the second precipitation treatment step, the molar ratio of uranium in the second filtrate to the hydrogen peroxide is 1:(1~5).

[0017] In some of the embodiments, in the method for treating xenotime acid slag, the reducing agent includes at least one of thiourea, sodium sulfite, sodium bisulfite, hydrazine hydrate and formaldehyde.

[0018] In some of the embodiments, in the method for treating xenotime acid slag, the oxidant includes at least one of hydrogen peroxide, sodium chlorate, sodium hypochlorite, oxygen and ozone.

[0019] In some of the embodiments, in the method for treating xenotime acid slag, the phosphorus source includes at least one of phosphoric acid, monohydrogen phosphate and dihydrogen phosphate.

[0020] In some of the embodiments, in the method for treating xenotime acid slag, the first pH adjuster includes at least one of rare earth carbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ammonia water and sodium hydroxide.

[0021] In some of the embodiments, in the method for treating xenotime acid slag, the rare earth precipitant includes at least one of ammonium bicarbonate, ammonium carbonate, sodium carbonate, sodium bicarbonate, ammonia water and sodium hydroxide.

[0022] In some embodiments, in the method for treating xenotime acid slag, the step of mixing the third filtrate and the rare earth precipitant further comprises the step of adding crystalline rare earth; and / or

[0023] The pH value of the third precipitation treatment is 6.8-7.2.

[0024] In some of the embodiments, the method for treating xenotime acid slag further includes, before the first solid-liquid separation step, a step of adjusting the pH value of the acid solution after the acid dissolution to 1.0-1.5 using a third pH adjuster.

[0025] Compared with the prior art, the method for treating xenotime acid slag of the present application has the following beneficial effects:

[0026] The method for treating xenotime acid slag of the present application first mixes the xenotime acid slag with water and performs sorting, separates the light mud of the acid slag from the heavy sand, and then acid-dissolves the light mud of the acid slag under the action of a hydrochloric acid solution and a reducing agent, and by controlling the mass concentration of the hydrochloric acid solution in the acid-dissolving step and the ratio between the light mud of the acid slag and the hydrochloric acid solution, the rare earth, thorium, uranium and iron elements in the light mud of the acid slag react with the hydrochloric acid to form chloride salts, which is beneficial to improving the leaching rate of the rare earth, thorium, uranium and iron elements, especially effectively improving the leaching rate of the insoluble terbium and cerium in the acid slag, and is beneficial to the subsequent recovery of the rare earth. ; The first filtrate is mixed with an oxidant to carry out an oxidation reaction, so that divalent iron is oxidized into trivalent iron, and the trivalent iron then reacts with a phosphorus source to form an iron precipitate, thereby recovering the iron element; the pH value of the second filtrate is adjusted to a specific value, under which the thorium element reacts with the first pH adjuster to form a thorium precipitate, and the uranium in the second filtrate reacts with hydrogen peroxide to form a uranium precipitate, and the iron impurity content in the thorium precipitate and the uranium precipitate is relatively low; the third filtrate is then mixed with a rare earth precipitant to carry out a third precipitation treatment to obtain a rare earth precipitate, thereby recovering the rare earth element, and the recovery rate of the rare earth element is relatively high.

[0027] The method for treating xenotime acid slag of the present application has simple process, simple equipment investment, and convenient operation. It does not require an ion exchange column or an extraction tank, and a conventional stirring tank can be used for the treatment. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in combination with the embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and are not used to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0029] It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the present application, and the equivalent forms obtained also fall within the scope of protection of the present application. For example, the features illustrated or described as part of one embodiment can be combined in another embodiment in a suitable manner to produce a new embodiment. In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0030] 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 implementation modes and embodiments and are not intended to limit this application.

[0031] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0032] In the present application, "plurality", "multiple", "multiple times", etc., unless otherwise specified, refer to a quantity greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0033] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0034] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0035] Herein, "preferred", "better", "more preferred", and "suitable" are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute a limitation on the scope of protection of this application. If multiple "preferred" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "preferred" item is independent.

[0036] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0037] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0038] In the present application, the terms "first", "second", "third", "fourth", etc. in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0039] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0040] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0041] 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.

[0042] In this application, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0043] In this application, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0044] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

[0045] The mass or weight of the relevant components mentioned in the specification of the embodiments of the present application may not only refer to the specific content of each component, but also indicate the proportional relationship of the mass or weight between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the embodiments of the present application, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass or weight described in the specification of the embodiments of the present application may be units known in the chemical industry such as μg, mg, g, and kg.

[0046] Although xenotime and monazite are both phosphate rare earth ores, there are certain differences in their composition and physical phases, and the treatment processes and acid slag obtained are also different. If the existing monazite acid slag method is used to treat xenotime acid slag, there are problems such as low rare earth leaching rate, high treatment cost, or ineffective recovery of other elements such as thorium and iron.

[0047] An embodiment of the present application provides a method for treating xenotime acid slag, comprising the following steps:

[0048] Step S10: After mixing the xenotime acid slag and water, the mixture is sorted to obtain acid slag light mud.

[0049] It is understandable that heavy sand is mostly undecomposed xenotime, monazite, zirconite, etc., which are difficult to dissolve in acid. It is necessary to sort out the heavy sand and return it to alkali roasting. If necessary, the sorted heavy sand needs to be further beneficiated to enrich rare earths and then returned to alkali roasting. Before acid dissolution, the xenotime acid slag and water are mixed and sorted to separate the light mud of the acid slag from the heavy sand. The light mud is specially used for the recycling of thorium, uranium and rare earths, which can reduce the amount of slag, improve the recovery rate of rare earths, and effectively avoid the material consumption and yield loss caused by the heavy sand in the extraction of valuable elements from the xenotime acid slag.

[0050] In some of the examples, in step S10, the solid content of the slag aqueous solution after the xenotime acid slag and water are mixed is 20% to 30%.

[0051] In some examples, step S10 includes the following steps:

[0052] The xenotime acid slag and water are mixed and stirred for 2 to 4 hours. The mixture is allowed to stand after the stirring is stopped, and the upper light mud slurry is collected. The acid slag light mud is obtained through solid-liquid separation.

[0053] Furthermore, the step of collecting the upper light mud material includes: pumping the upper light mud material into the filter press for filtration, or opening the middle valve to allow the upper light mud material to flow into the collection bucket, and then performing solid-liquid separation, and the solid phase is the acid-dissolved slag light mud. It can be understood that the liquid phase can be returned to the xenotime acid dissolution process or recycled in this process.

[0054] It can be understood that the slurry (heavy sand) with a larger specific gravity in the lower layer will be subsequently processed for mineral processing.

[0055] It can be understood that before performing step S20, a step of analyzing the element content in the acid slag light mud obtained in step S10 is also included.

[0056] Step S20: After the acid-soluble slag light mud, hydrochloric acid solution and reducing agent obtained in step S10 are mixed and acid-soluble, a first solid-liquid separation is performed to obtain a first filtrate; the mass concentration of the hydrochloric acid solution is 15% to 25%, and the mass ratio of the volume of the hydrochloric acid solution to the acid-soluble slag light mud is 3 m 3 / 1000 kg ~5 m 3 / 1000kg.

[0057] The acid-soluble slag light mud is acid-soluble under the action of a hydrochloric acid solution and a reducing agent, and by controlling the mass concentration of the hydrochloric acid solution in the acid-soluble step and the ratio between the acid-soluble slag light mud and the hydrochloric acid solution, rare earth, thorium, uranium and iron elements in the acid-soluble slag light mud react with hydrochloric acid to generate chloride salts, which is beneficial to improving the leaching rates of rare earth, thorium, uranium and iron elements, and is particularly effective in improving the leaching rates of insoluble terbium and cerium in the acid-soluble slag.

[0058] RE(OH)3+3HCl→RECl3+3H2O;

[0059] Fe(OH)3+3HCl→FeCl3+3H2O;

[0060] Th(OH)4+4HCl→ThCl4+4H2O;

[0061] Na2U2O7+6HCl→2UO2Cl2+2 NaCl +3H2O.

[0062] It is understood that the mass concentration of the hydrochloric acid solution includes but is not limited to 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%; the mass ratio of the volume of the hydrochloric acid solution to the acid slag light mud includes but is not limited to 3 m 3 / 1000 kg、3.2 m 3 / 1000 kg、3.5 m 3 / 1000 kg、3.8 m 3 / 1000 kg、4 m 3 / 1000 kg、4.2 m 3 / 1000 kg、4.5m 3 / 1000 kg、4.8 m 3 / 1000 kg、5 m 3 / 1000 kg; in some examples, it can be within the range formed by any two of these point values ​​as end values, the same below.

[0063] In some of the examples, in step S20, the mass concentration of the hydrochloric acid solution is 15% to 20%.

[0064] In some examples, in step S20, the mass ratio of the hydrochloric acid solution to the acid slag light mud is 3 m 3 / 1000 kg ~4 m 3 / 1000kg.

[0065] In some of the examples, in step S20, the mass ratio of the rare earth oxide in the acid-soluble slag light mud to the reducing agent is 1:(0.02~0.3).

[0066] It can be understood that the mass ratio of rare earth oxide to reducing agent in acid slag light mud includes but is not limited to 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.12, 1:0.15, 1:0.18, 1:0.2, 1:0.22, 1:0.25, 1:0.28, and 1:0.3.

[0067] Optionally, the mass ratio of the rare earth oxide in the acid slag light mud to the reducing agent is 1:(0.05-0.3). Further, the mass ratio of the rare earth oxide in the acid slag light mud to the reducing agent is 1:(0.05-0.25).

[0068] By controlling the ratio of rare earth to reducing agent in acid slag light mud, the leaching rate of rare earth in acid slag light mud can be further improved, especially the leaching rate of terbium and dysprosium elements therein, thereby improving the total recovery rate of rare earth and the recovery rate of terbium and dysprosium.

[0069] In some examples, in step S20, the reducing agent includes at least one of thiourea, sodium sulfite, sodium bisulfite, hydrazine hydrate and formaldehyde. Optionally, the reducing agent includes at least one of thiourea and sodium sulfite.

[0070] In some of the examples, in step S20, the acid-soluble slag light mud and the hydrochloric acid solution are first mixed and stirred for 2 to 4 hours, the temperature is raised to 50°C to 60°C, and then a reducing agent is added, the temperature is continued to be raised to ≥95°C, and the acid solution is kept warm for 1 to 2 hours.

[0071] In some of the examples, in step S20, before performing the first solid-liquid separation step, a step of adjusting the pH value of the acid solution after acid dissolution to 1.0-1.5 using a third pH adjuster is also included.

[0072] It can be understood that before performing the first solid-liquid separation step, the pH value of the acid solution after acid dissolution is adjusted to 1.0~1.5 to reduce the acidity of the acid solution and reduce the impact on the environment; further, the pH value includes but is not limited to 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5.

[0073] In some examples, in step S20, the third pH adjuster includes at least one of rare earth carbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ammonia water, and sodium hydroxide.

[0074] In some examples, in step S20, when the temperature of the acid solution after acid dissolution drops to ≤80°C, a third pH adjuster is added.

[0075] The first filtrate and the oxidant are mixed to perform an oxidation reaction to oxidize the divalent iron to trivalent iron. It can be understood that the first solid-liquid separation obtains the first filtrate and the first solid phase, and the filter residue is washed with water in a cross-flow stirring manner to perform solid-liquid separation, and the washing water is returned to step S20 to prepare hydrochloric acid, and the filter residue enters the mineral processing.

[0076] Step S30: The first filtrate obtained in step S20 is mixed with an oxidant to perform an oxidation reaction to obtain an oxidation reaction liquid.

[0077] In some examples, in step S30, the oxidant includes at least one of hydrogen peroxide, sodium chlorate, sodium hypochlorite, oxygen and ozone.

[0078] It is understood that the amount of oxidant used can be determined based on whether the divalent iron in the first filtrate is completely converted into trivalent iron, or by quantitatively testing the Fe 2+ The concentration is less than 0.01g / L.

[0079] Step S40: After the oxidation reaction liquid obtained in step S30 is mixed with the phosphorus source and subjected to a first precipitation treatment, a second solid-liquid separation is performed to obtain an iron precipitate and a second filtrate, respectively.

[0080] The first filtrate is mixed with an oxidant to carry out an oxidation reaction, so that the divalent iron is oxidized into trivalent iron, and the trivalent iron then reacts with a phosphorus source to form an iron precipitate, thereby recovering the iron element.

[0081] In some examples, in step S40, the phosphorus source includes at least one of phosphoric acid, monohydrogen phosphate, and dihydrogen phosphate.

[0082] It is understood that monohydrogen phosphate includes but is not limited to sodium monohydrogen phosphate; dihydrogen phosphate includes but is not limited to sodium dihydrogen phosphate. Optionally, the phosphorus source is phosphoric acid.

[0083] When the phosphorus source is phosphoric acid, the iron precipitate is ferric phosphate. The iron is recovered in the form of ferric phosphate and can be used as a raw material for new energy. It has higher economic value than the conventional method of generating iron hydroxide to remove iron.

[0084] In some of the examples, in step S40, the molar ratio of the phosphorus source to the trivalent iron in the oxidation reaction solution is 0.9-1:1.

[0085] It can be understood that the amount of phosphorus source used is determined according to the amount of ferric iron in the first filtrate, so that the concentration of ferric iron in the final filtrate is less than 0.2 g / L.

[0086] In some of the examples, in step S40, the first precipitation treatment step further includes a step of using a second pH adjuster to adjust the pH value of the oxidation reaction solution and the first precipitation solution of the phosphorus source to 1.5-2.5.

[0087] The pH value of the first precipitation liquid is adjusted to a specific range, which is conducive to the formation of iron precipitates by iron elements and less rare earth entrainment loss. It is understood that the pH value of the first precipitation liquid includes but is not limited to 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5.

[0088] In some of the examples, in step S40, the pH value of the first precipitation solution is adjusted to 1.5-2.

[0089] In some examples, in step S40, the second pH adjuster includes at least one of rare earth carbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ammonia water, and sodium hydroxide.

[0090] In some of the examples, in step S40, before adjusting the pH value of the first precipitation solution with the second pH adjuster, the temperature of the first precipitation solution is raised to above 90°C.

[0091] Step S50: adjusting the pH value of the second filtrate obtained in step S40 to 3.8-4.2 with a first pH adjusting agent, adding hydrogen peroxide to perform a second precipitation treatment, and performing a third solid-liquid separation to obtain a thorium-uranium precipitate and a third filtrate.

[0092] The pH value of the second filtrate is adjusted to a specific value. Under the pH condition, the thorium element reacts with the first pH adjuster to generate a thorium precipitate, the tetravalent uranium generates a uranium hydroxide precipitate, and the hexavalent uranium in the second filtrate reacts with hydrogen peroxide to generate a uranium precipitate, thereby avoiding the problem that high-valent uranyl is difficult to precipitate under the pH condition. In addition, the thorium precipitate and the uranium precipitate contain fewer impurities, and the obtained thorium-uranium precipitate has a higher grade. At the same time, the rare earth element does not precipitate.

[0093] Th 4+ +4HCO3 - →Th(CO3)2↓+2H2O+2CO2↑;

[0094] Th 4+ +4OH - →Th(OH)4↓;

[0095] UO2 2+ +H2O 2+ nH2O→2UO4·nH2O↓+2H + ;

[0096] U 4+ +OH - →U(OH)4↓;

[0097] H + +NH4HCO3→NH4 + +H2O+CO2↑.

[0098] It is understood that the pH value of the second filtrate is adjusted to include but is not limited to 3.8, 3.9, 4.0, 4.1, and 4.2.

[0099] In some examples, in step S50, the first pH adjuster includes at least one of rare earth carbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ammonia water, and sodium hydroxide.

[0100] In some examples, in step S50, the first pH adjuster is added when the temperature of the second filtrate is 50°C to 75°C.

[0101] In some of the examples, in step S50, in the second precipitation treatment step, the molar ratio of uranium to hydrogen peroxide in the second filtrate is 1:(1-5).

[0102] It is understood that the molar ratio of uranium to hydrogen peroxide in the second filtrate includes but is not limited to 1:1, 1:2, 1:3, 1:4, and 1:5.

[0103] Optionally, the molar ratio of uranium to hydrogen peroxide in the second filtrate is 1:(2-4).

[0104] Step S60: The third filtrate obtained in step S50 is mixed with a rare earth precipitant to perform a third precipitation treatment to obtain a rare earth precipitate.

[0105] The method for treating xenotime acid slag of the present application first mixes the xenotime acid slag with water and performs sorting, separates the light mud of the acid slag from the heavy sand, and then acid-dissolves the light mud of the acid slag under the action of a hydrochloric acid solution and a reducing agent, and by controlling the mass concentration of the hydrochloric acid solution in the acid-dissolving step and the ratio between the light mud of the acid slag and the hydrochloric acid solution, the rare earth, thorium, uranium and iron elements in the light mud of the acid slag react with the hydrochloric acid to form chloride salts, which is beneficial to improving the leaching rate of the rare earth, thorium, uranium and iron elements, and is particularly effective in improving the leaching rate of the insoluble terbium and cerium in the acid slag. ; The first filtrate is mixed with an oxidant to carry out an oxidation reaction, so that the divalent iron is oxidized into trivalent iron, and the trivalent iron then reacts with a phosphorus source to form an iron precipitate, thereby recovering the iron element; the pH value of the second filtrate is adjusted to a specific value, under which the thorium element reacts with the first pH adjuster to form a thorium precipitate, and the uranium in the second filtrate reacts with hydrogen peroxide to form a uranium precipitate, and the iron impurity content in the thorium precipitate and the uranium precipitate is relatively low; the third filtrate is then mixed with a rare earth precipitant to carry out a third precipitation treatment to obtain a rare earth precipitate, thereby recovering the rare earth element.

[0106] 2RE 3+ +3 HCO 3- →RE2(CO3)3↓+H + ;

[0107] 2RE 3+ +3 CO3 2- →RE2(CO3)3↓.

[0108] In some of the examples, in step S60, the rare earth precipitant includes at least one of ammonium bicarbonate, ammonium carbonate, sodium carbonate, sodium bicarbonate, ammonia water, and sodium hydroxide.

[0109] In some of the examples, in step S60, the molar ratio of the rare earth element to the rare earth precipitant in the third filtrate is 1:(2.1~2.8).

[0110] It can be understood that the molar ratio of the rare earth element to the rare earth precipitant in the third filtrate includes but is not limited to 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, and 1:2.8.

[0111] In some of the examples, in step S60, the pH value of the third precipitation treatment is 6.8-7.2.

[0112] It can be understood that the pH value of the third precipitation treatment includes but is not limited to 6.8, 6.9, 7, 7.1, and 7.2.

[0113] In some of the examples, in step S60, crystalline rare earth is first added to the third filtrate, and then a rare earth precipitant is added to perform a third precipitation treatment.

[0114] It can be understood that step S60 also includes the step of solid-liquid separation of the slurry after the third precipitation treatment, the liquid phase flows into the storage tank, and the ammonium chloride is recovered by evaporation, concentration and crystallization, and the distilled condensed water is reused without wastewater discharge; the solid phase is washed with cross-current water, and then solid-liquid separation is performed to obtain a rare earth precipitant, and the washing liquid can be used for the preparation of ammonium bicarbonate or sodium carbonate solution during ammonium carbonate precipitation.

[0115] The stirring tank and sedimentation tank of the present application are acid- and alkali-resistant tanks with stirring paddles made of PP or PPH materials. A filter press can be used for solid-liquid separation. The filter press is a plate type, chamber type, diaphragm type, etc. filter press familiar to the industry. The centrifuge is a three-legged high-speed centrifugal stainless steel or corrosion-resistant centrifuge familiar to the industry. The evaporation, concentration, and crystallization equipment is a two-effect, triple-effect evaporation, MVR, negative pressure concentration kettle, etc. familiar to the industry.

[0116] The treatment method of xenotime acid slag of the present application has a simple process, simple equipment investment and convenient operation. No ion exchange column or extraction tank is required, and a conventional stirring tank can be used, which has a relatively friendly working environment. The wastewater is evaporated and concentrated after membrane enrichment and recycled, and the residual heat of evaporation is supplied to the sulfuric acid slurry reaction. The waste slag is treated with sludge drying system equipment, which can achieve slag reduction, resource utilization and harm reduction. This process fundamentally solves the problems of "three wastes" pollution, waste of resources, and large consumption of raw and auxiliary materials generated in the rare earth smelting process, and realizes the green and efficient use of rare earth and co-existing resources.

[0117] The raw materials used in this application are all commercially available, and there is no special requirement. Xenotime acid slag is well known to those skilled in the art, and there is no special requirement.

[0118] The present application is further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present application are not limited thereto.

[0119] Example 1

[0120] S1: Xenotime acid slag separation

[0121] 2000 kg of xenotime acid slag was placed into a 10m 3Add slag washing recycled water to the conical bottom straight cylindrical iron stirring tank lined with acid-resistant rubber to prepare the slurry with a solid content of 30%. Stir for 2 hours, stop stirring and clarify for 1 hour, pump the upper light mud slurry into the filter press for filtration, the filter cake is the acid-soluble slag light mud and enters S2, and the filtrate is loaded into the storage tank for recycling; open the bottom valve to release the slurry with a larger specific gravity at the bottom of the stirring tank, filter it and then send it to mineral processing for filtration.

[0122] The water content of the acid slag light mud obtained after gravity separation is about 46.90%, and its main chemical components on dry basis are shown in Table 1.

[0123] Table 1

[0124]

[0125] S2: Acid soluble

[0126] In the PPH stirring tank, 3m of hydrochloric acid with a mass concentration of 15% was prepared with circulating water and industrial hydrochloric acid. 3 , add 1000 kg of acid slag light mud obtained from S1, stir for 2 hours, then heat to 50℃, add thiourea according to the molar ratio of REO: reducing agent in the light mud of 1:0.125, continue to heat to above 95℃, keep stirring for 1 hour, stop heating, when the temperature is about to reach below 80℃, add ammonium bicarbonate to adjust the pH to 1.5, use filter press for solid-liquid separation, the first filtrate is 2.98m 3 Enter S3, (add 1.25m3 of water to the residue 3 Stir and wash, use a diaphragm filter press to separate the solid and liquid, the washing filtrate enters the storage tank and is reserved for the next S2 acid solution to prepare dilute hydrochloric acid, the filtrate is 1.2m 3 , of which the REO content is 4.13g / L. The filter residue is further stirred and washed with 1.25m³ of water. The filtrate after filter pressing is used as washing water, and the filter residue enters the mineral processing process). The iron, phosphorus, rare earth, thorium and uranium contents in the first filtrate are analyzed and shown in Table 2.

[0127] Table 2

[0128]

[0129] S3: Recycling Iron

[0130] The 2.98m³ first filtrate obtained by S2 filter press was pumped into the 10m 3 Slowly add hydrogen peroxide into the iron precipitation tank and use potassium ferrocyanide solution to check for Fe 2+Then, add 112 kg of 85% industrial phosphoric acid at a molar ratio of P:Fe=1:1, raise the temperature to above 90°C, add ammonium bicarbonate to adjust the pH to 1.5, and a precipitate is generated. After stirring and reacting for 1 hour, sample and analyze the iron ion in the solution (0.2 g / L). After aging for 2 hours, use a filter press to separate the solid and liquid. The filter residue is the iron phosphate product, and the second filtrate enters S4.

[0131] S4: Recovery of thorium uranium

[0132] The temperature of the second filtrate is 55°C. Ammonium bicarbonate is slowly added while hot to adjust the pH to 4.0. Hydrogen peroxide is added (the molar ratio of uranium in the second filtrate to hydrogen peroxide is 1:2). The mixture is stirred for reaction for 2 hours and aged for 2 hours. The filter press is used for solid-liquid separation to obtain the third filtrate and a filter cake containing thorium and uranium. The filter cake is unloaded from the filter press into bags and sent to the thorium-uranium separation and purification process. The third filtrate enters S5.

[0133] S5: Precipitated rare earth

[0134] The third filtrate obtained in S4 is heated to about 45°C, 5 kg of crystalline rare earth carbonate prepared in advance is first added, and then ammonium bicarbonate solution is slowly added. When the precipitation end point is controlled at a pH value of 7.2, the REO in the test solution is less than 0.001 g / L, and the addition of ammonium bicarbonate solution is stopped. The molar ratio of REO: ammonium bicarbonate is 1:2.8. Stirring is continued for 1 hour, and clarification is performed for 2 hours. A filter press is used for solid-liquid separation to obtain a filter cake and a filtrate. The filtrate is the precipitation mother liquor, which enters S7 for treatment, and the filter cake is rare earth carbonate, which enters S6 for washing.

[0135] S6: Washing rare earth carbonate

[0136] The filter cake obtained by S5 filtration was washed with cross-current water twice, and the filter press was used for solid-liquid separation each time. The washed rare earth carbonate was bagged, and the filtrate was used for the preparation of ammonium bicarbonate solution.

[0137] S7: Treatment of precipitation mother liquor

[0138] The filtrate obtained by filter pressing of S5 precipitated rare earth flows into the storage tank. After membrane treatment, part of the water is returned to wash the rare earth carbonate. The concentrated water is recovered by double-effect evaporation, concentration and crystallization to recover ammonium chloride, and the distilled condensed water is reused without wastewater discharge.

[0139] Example 2

[0140] It is basically the same as Example 1, except that in the S2 acid dissolution step, the molar ratio of REO: reducing agent in the light mud is 1:0.25.

[0141] Example 3

[0142] It is basically the same as Example 1, except that in the S2 acid dissolution step, the molar ratio of REO: reducing agent in the light mud is 1:0.05.

[0143] Example 4

[0144] It is basically the same as Example 1, except that in the S2 acid dissolution step, the molar ratio of REO: reducing agent in the light mud is 1:0.03.

[0145] Example 5

[0146] It is basically the same as Example 1, except that in the S2 acid dissolution step, the molar ratio of REO: reducing agent in the light mud is 1:0.3.

[0147] The rare earth leaching rate is basically the same as that of Example 1, the cost is higher than that of Example 1, and the environmental impact is increased.

[0148] Example 6

[0149] It is basically the same as Example 1, except that in the S2 acid dissolution step, the reducing agent thiourea is replaced by sodium sulfite, and the molar ratio of REO:sodium sulfite in the light mud is 1:0.25.

[0150] Example 7

[0151] It is basically the same as Example 1, except that in the S2 acid dissolution step, the reducing agent thiourea is replaced by hydrazine hydrate, and the molar ratio of REO:hydrazine hydrate in the light mud is 1:0.25.

[0152] Example 8

[0153] The same as Example 1, except that in the acid dissolution step S2, the amount of hydrochloric acid with a mass concentration of 15% is 5m 3 .

[0154] In Example 8, more materials are consumed in the neutralization of the residual acid, resulting in a higher salt content.

[0155] Example 9

[0156] The method is basically the same as Example 1, except that in the acid dissolution step S2, the mass concentration of hydrochloric acid is 20%.

[0157] Example 10

[0158] The method is basically the same as Example 1, except that in the acid dissolution step S2, the mass concentration of hydrochloric acid is 25%.

[0159] Embodiment 11

[0160] The method is basically the same as Example 1, except that in the iron recovery step S3, ammonium bicarbonate is added to adjust the pH to 2.0.

[0161] Example 12

[0162] The method is basically the same as Example 1, except that in the iron recovery step S3, ammonium bicarbonate is added to adjust the pH to 2.5.

[0163] Example 13

[0164] The method is basically the same as Example 1, except that in the step S4 of recovering iron, the molar ratio of uranium to hydrogen peroxide in the second filtrate is 1:5.

[0165] Embodiment 14

[0166] The method is basically the same as Example 1, except that in the iron recovery step S4, the molar ratio of uranium to hydrogen peroxide in the second filtrate is 1:1.

[0167] Embodiment 15

[0168] It is basically the same as Example 1, except that the xenotime acid slag is different. The water content of the acid slag light mud obtained by step S1 in Example 1 is about 51.24%, and its main chemical components on a dry basis are shown in Table 3.

[0169] Table 3

[0170]

[0171] Example 16

[0172] It is basically the same as Example 1, except that the xenotime acid slag is different. The typical values ​​of the main components of the acid slag light mud obtained by step S1 in Example 1 are as follows: the wet basis analysis water content is about 52.56%, and its main chemical components are shown in Table 4.

[0173] Table 4

[0174]

[0175] Comparative Example 1

[0176] The same as Example 1, except that in the acid dissolution step S2, the amount of hydrochloric acid with a mass concentration of 15% is 2m 3 .

[0177] Comparative Example 2

[0178] The method is basically the same as Example 1, except that in the acid dissolution step S2, the mass concentration of hydrochloric acid is 10%.

[0179] The processing parameters of xenotime acid slag in various embodiments and comparative examples are shown in Table 5, wherein:

[0180] "Light mud: hydrochloric acid" refers to the mass ratio of acid slag light mud to the volume ratio of hydrochloric acid solution; "REO: reducing agent" refers to the mass ratio of rare earth oxides in acid slag light mud to reducing agent; "terbium content" refers to the change in the rare earth terbium content in the first filtrate of S2 and the rare earth terbium content in the acid slag light mud of S1; "pH in S3" refers to the pH value controlled at the precipitation endpoint in step S3; "uranium: hydrogen peroxide" refers to the molar ratio of uranium to hydrogen peroxide in the second filtrate; "pH in S5" refers to the pH value controlled at the precipitation endpoint in step S5.

[0181] Table 5

[0182]

[0183] The recovery rates of each element are shown in Table 6, where:

[0184] Rare earth leaching rate = (volume of acid leaching solution * REO in acid leaching solution + volume of washing water * REO in washing water) / (weight of light mud of acid leaching residue * (1-water content) * dry basis REO in light mud) * 100%;

[0185] Total recovery of rare earth = (weight of rare earth carbonate * (1-ignition loss) * loss rate * REO of burned product) / (weight of acid leaching residue light mud * (1-water content) * dry basis REO in light mud - volume of washing water * REO in washing water) * 100%;

[0186] Thorium recovery rate = weight of thorium-uranium precipitate * (1-water content) * dry basis thorium content in precipitate / (weight of acid leaching residue light mud * (1-water content) * dry basis thorium content in light mud);

[0187] Uranium recovery rate = weight of thorium uranium precipitate * (1-water content) * dry uranium content in the precipitate / (weight of acid leaching residue light mud * (1-water content) * dry uranium content in the light mud).

[0188] Table 6

[0189]

[0190] It can be seen that compared with the comparative example, the treatment methods of xenotime acid slag provided in each embodiment have higher recovery rates of rare earth, thorium, uranium and iron elements extracted. Among them, the rare earth content in the xenotime acid slag used in Example 15 is lower than that in Example 1, and the final rare earth leaching rate is slightly reduced; the rare earth content in the acid slag used in Example 16 is higher than that in Example 1, and the rare earth leaching rate is slightly improved.

[0191] 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.

[0192] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solutions of the present application in detail, but cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the contents of the attached claims, and the description can be used to interpret the contents of the claims.

Claims

1. A method for treating xenotime acid slag, characterized in that: The following steps are involved: After mixing the xenotime acid slag and water, the mixture is sorted to obtain acid slag light mud; The acid-soluble slag light mud, hydrochloric acid solution and reducing agent are mixed and acid-soluble, and then a first solid-liquid separation is performed to obtain a first filtrate; The mass concentration of the hydrochloric acid solution is 15% to 25%, and the mass ratio of the volume of the hydrochloric acid solution to the acid slag light mud is 3 m 3 / 1000 kg ~5 m 3 / 1000kg; The first filtrate and an oxidant are mixed to perform an oxidation reaction to obtain an oxidation reaction liquid; The oxidation reaction liquid and the phosphorus source are mixed to perform a first precipitation treatment, and then a second solid-liquid separation is performed to obtain an iron precipitate and a second filtrate respectively; The pH value of the second filtrate is adjusted to 3.8-4.2 by using a first pH adjusting agent, and then hydrogen peroxide is added to perform a second precipitation treatment, and a thorium-uranium precipitate and a third filtrate are obtained by performing a third solid-liquid separation. The third filtrate and the rare earth precipitant are mixed to perform a third precipitation treatment to obtain a rare earth precipitate.

2. The method for treating xenotime acid slag according to claim 1, characterized in that: The mass concentration of the hydrochloric acid solution is 15% to 20%.

3. The method for treating xenotime acid slag according to claim 1, characterized in that: The mass ratio of the rare earth oxide in the acid-soluble slag light mud to the reducing agent is 1:(0.02~0.3); optionally, the mass ratio of the rare earth oxide in the acid-soluble slag light mud to the reducing agent is 1:(0.05~0.3).

4. The method for treating xenotime acid slag according to claim 1, characterized in that: The molar ratio of the phosphorus source to the trivalent iron in the oxidation reaction solution is 0.9 to 1:1; and / or The first precipitation treatment step also includes a step of using a second pH adjuster to adjust the pH value of the oxidation reaction solution and the first precipitation solution of the phosphorus source to 1.5~2.5; optionally, the pH value of the first precipitation solution is adjusted to 1.5~2.

5. The method for treating xenotime acid slag according to claim 1, characterized in that: In the second precipitation treatment step, the molar ratio of uranium in the second filtrate to the hydrogen peroxide is 1:(1-5).

6. The method for treating xenotime acid slag according to any one of claims 1 to 5, characterized in that: The reducing agent includes at least one of thiourea, sodium sulfite, sodium bisulfite, hydrazine hydrate and formaldehyde.

7. The method for treating xenotime acid slag according to any one of claims 1 to 5, characterized in that: The oxidant comprises at least one of hydrogen peroxide, sodium chlorate, sodium hypochlorite, oxygen and ozone; and / or The phosphorus source includes at least one of phosphoric acid, monohydrogen phosphate and dihydrogen phosphate.

8. The method for treating xenotime acid slag according to any one of claims 1 to 5, characterized in that: The first pH regulator comprises at least one of rare earth carbonate, ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate, ammonia water and sodium hydroxide; and / or The rare earth precipitant includes at least one of ammonium bicarbonate, ammonium carbonate, sodium carbonate, sodium bicarbonate, ammonia water and sodium hydroxide.

9. The method for treating xenotime acid slag according to any one of claims 1 to 5, characterized in that: The step of mixing the third filtrate and the rare earth precipitant further comprises the step of adding crystalline rare earth; and / or The pH value of the third precipitation treatment is 6.8-7.

2.

10. The method for treating xenotime acid slag according to any one of claims 1 to 5, characterized in that: Before performing the first solid-liquid separation step, the method further includes using a third pH adjuster to adjust the pH value of the acid solution after acid dissolution to 1.0-1.5.

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